HK1202988B - Microstructured electrode structures - Google Patents

Description

Microstructured electrode structure

Technical Field

The present invention relates generally to structures for use in energy storage devices, energy storage devices incorporating the structures, and methods of making the structures and energy devices.

Background

A rocking chair or plug-in secondary battery is an energy storage device in which carrier ions (carrier ions) such as lithium, sodium or potassium ions move between an anode and a cathode through an electrolyte. A secondary battery may include a single battery cell (battery cell), or more than two battery cells electrically coupled to form a battery, wherein each battery cell includes an anode, a cathode, and an electrolyte.

In a rocking chair cell, both the anode and cathode comprise materials in which carrier ions are inserted and extracted. When the cell is discharged, the carrier ions are extracted from the anode and inserted into the cathode. When the cell is charged, the reverse process occurs: the carrier ions are extracted from the cathode and inserted into the anode.

Fig. 1 shows a cross-sectional view of an electrochemical stack (electrochemical stack) of a prior art energy storage device, such as a non-aqueous lithium ion battery. The electrochemical stack 1 comprises a cathode current collector 2, on top of which a cathode layer 3 is mounted. The cathode layer is covered by a microporous separator (4), on which microporous separator 4a combination of an anode current collector (5) and an anode layer (6) is placed. The laminate is sometimes covered with another separator layer (not shown) located above the anode current collector 5, wound and caulked in a can shape, and filled with a nonaqueous electrolyte to assemble a secondary battery.

The anode and cathode current collectors share the current from the respective active electrochemical electrodes and enable the current to be transferred to the environment outside the cell. A portion of the anode current collector is in physical contact with the anode active material, and a portion of the cathode current collector is in contact with the cathode active material. The current collector does not participate in the electrochemical reaction and is therefore limited to materials that are electrochemically stable over the respective electrochemical potentials used for the anode and cathode.

In order for the current collectors to bring the current to the environment outside the cell, they are typically connected to a tab (tab), terminal (tag), package-feed-through or case feed-through (typically collectively referred to as a contact). One end of the contact is connected to one or more current collectors, while the other end passes through the battery package to be electrically connected to the environment outside the battery. The anode contact is connected to the anode current collector and the cathode contact is connected to the cathode current collector by welding, crimping (crimp) or ultrasonic bonding, or bonding in place with a conductive adhesive.

During charging, lithium leaves the cathode layer 3 and passes as lithium ions through the separator 4 into the anode layer 6. Depending on the anode material used, lithium ions are intercalated (e.g., in the matrix of the anode material without forming an alloy) or alloyed. During discharge, lithium leaves the anode layer 6, passes through the separator 4, and enters the cathode layer 3. The current collectors conduct electrons from the battery contacts (not shown) to the electrodes, or vice versa.

Existing energy storage devices, such as batteries, fuel cell cells and electrochemical capacitors, typically have a two-dimensional laminate structure (e.g., planar or spiral wound laminates) as exemplified in fig. 1, wherein the surface area of each laminate is approximately equal to its geometric footprint (disregarding porosity and surface roughness).

Three-dimensional batteries have been proposed in the literature as a means of improving battery capacity and active material utilization. It has been proposed that three-dimensional structures can be used to provide greater surface area and higher energy than two-dimensional laminate battery structures. Manufacturing three-dimensional energy storage devices is beneficial due to the increased energy available from the smaller geometric area. See, for example, WO2008/089110 to Rust et al and "Three-Dimensional Battery architecture" to Long et al, chemical reviews, (2004),104, 4463-.

New anode and cathode materials have also been proposed as means to improve energy density, safety, charge/discharge rate, and cycle life of secondary batteries. Some of these new high capacity materials, such as silicon, lithium or tin anodes in lithium batteries, have significant volume expansion that causes decomposition and exfoliation of existing electron collectors during lithium insertion and extraction. Silicon anodes, for example, have been proposed as an alternative to carbon-containing electrodes because of their ability to provide significantly greater energy per unit volume of matrix material for lithium battery applications. See, for example, U.S. patent publication No.2009/006856 to Konishike et al and "Nano-and Bulk-Silicon-Based Insertion antibodies for Lithium-Ion Secondary Cells" Journal of Power Sources163(2007) 1003-. The formation of lithium silicide when lithium is inserted into the anode results in a significant volume change that can lead to crack formation and pulverization of the anode. As a result, the battery capacity decreases as the battery is repeatedly charged and discharged.

Various strategies have been proposed to overcome the challenges presented by the significant volume changes experienced by silicon anodes due to repeated charge and discharge cycles. For example, Bourderau et al disclose amorphous silicon (Bourderau et al, "Amorphous silicon As A powdery Material For Li-Ion Batteries," Journal of Power sources81-82(1999) 233-236)). Li et al disclose silicon nanowires ("The crystalline structured Of By Nano-Si Anode used By Lith Lithium Insertion and extraction At Room Temperature," Solid State Ionics135(2000)181-191 Of Li et al). In NL1015956, Sloe Yao Kan discloses a porous silicon electrode for a battery. Shin et al also disclose Porous Silicon Electrodes For use in Batteries (Shin et al, "Porous Silicon Negative Electrodes For rechargeable lithium Batteries," Journal of Power Sources139(2005) 314-.

Monolithic electrodes, i.e., electrodes comprising a mass of electrode material that retains its shape without the use of a binder, have been proposed as an alternative to improving performance (weight and volume energy density, rate, etc.) relative to particulate electrodes that are molded or otherwise formed into a shape and rely on conductive agents or binders to retain the shape of aggregates of particulate material. The monolithic anode, for example, may comprise a monolithic block of silicon (e.g., single crystal silicon, polycrystalline silicon, or amorphous silicon), or it may comprise a mass of agglomerated particles that are inserted or otherwise processed to fuse the anode materials together and remove any binder. In one such exemplary embodiment, a silicon wafer may be used as a monolithic anode material for a lithium ion battery, wherein one face of the wafer is coupled to a first cathode element through a separator 4 and the other face is coupled to a second cathode element opposite thereto. In such an arrangement, an important technical challenge is the ability to collect and carry current from the integral electrodes to the outside of the cell while efficiently utilizing the available space inside the cell.

The energy density of conventional batteries can also be increased by reducing the weight and volume of inactive components to more efficiently package the battery. Current batteries use relatively thick current collectors because the foil that makes up the current collector is required to be used at a minimum thickness to be strong enough to survive the active material application process. A performance advantage can be expected if an invention is made to isolate the current collection from the process limitations.

Despite the various approaches, there remains a need for improved battery capacity and active material utilization.

Disclosure of Invention

In aspects of the invention, three-dimensional structures are provided for use in energy storage devices such as batteries, fuel cell cells, and electrochemical capacitors. The three-dimensional structure includes a microstructured anode active material layer on a side of a backbone (backbone) structure, the layer including a void fraction (void fraction) that can accommodate significant volume changes of the anode active material when cycling between charge and discharge states. Advantageously, the three-dimensional structure may be included in two or more cells that are vertically stacked (stack), such that the shortest distance between the anode active material and the cathode material in a cell is measured in a direction orthogonal to the stacking direction of the cell (e.g., in a three-dimensional cartesian (X-Y-Z) coordinate, if the stacking direction is the Z direction, the shortest distance between the anode active material and the cathode material is measured in the X or Y direction). The three-dimensional energy storage device can produce higher energy storage and recovery per unit geometric area than conventional devices. They may also provide a higher energy recovery rate for a particular amount of stored energy than two-dimensional energy storage devices, for example by minimizing or reducing the transport distance for electron and ion transport between the anode and cathode. These devices may be more suitable for miniaturization and for applications where the available geometric area of the device is limited and/or where the energy density requirements are higher than can be achieved with laminated devices.

Briefly, therefore, one aspect of the present invention is a structure for use in an energy storage device. The structure comprises a population (population) of microstructured anode active material layers, wherein (a) members of the population comprise a fibrous or porous anode active material and have a surface substantially perpendicular to a reference plane, (ii) a thickness of at least 1 micrometer measured in a direction parallel to the reference plane, a height of at least 50 micrometers measured in a direction orthogonal to the reference plane, and a void volume fraction of at least 0.1. Furthermore, a straight-line distance between at least two members of the group measured in a direction parallel to the reference plane is greater than a maximum height of any layer in the group.

Another aspect of the invention is an architecture for use in an energy storage device, the architecture comprising a backbone network, the backbone network comprising a flanking sequence. The side surface is substantially perpendicular to a reference plane and has a height of at least 50 microns measured in a direction substantially perpendicular to the reference plane. The structure further comprises a group of microstructured anode active material layers supported by the side faces, a maximum straight-line distance between at least two of the side faces in the group measured in a direction parallel to the reference plane being greater than a maximum height of any of the side faces in the sequence. The microstructured anode active material layer comprises a front surface, a back surface and a fibrous or porous anode active material, the microstructured anode active material layer having a void volume fraction of at least 0.1 and a thickness between the front and back surfaces of at least 1 micron. The back surface of each of the microstructured anode active material layers is adjacent (proximate) to a side of the backbone supporting the microstructured anode active material layer. The front surface of each of the microstructured anode active material layers is distal from the side of the backbone supporting the microstructured anode active material layer. The fibers comprised by the members of the population of microstructured anode active material layer are attached to the back surface of the members of the population comprising the fibers and have a central axis that is substantially parallel to the reference plane at the point of attachment of the fibers. The member of the group of microstructured anode active material layers comprises holes having hole openings with a major axis substantially parallel to the reference plane.

Another aspect of the invention is an electrochemical stack for use in an energy storage device. The electrochemical stack comprises a cathode structure, a separator layer and an anode structure arranged in a stack, the separator layer being disposed between the anode structure and the cathode structure, wherein a stacking direction of the cathode structure, the separator layer and the anode structure in the electrochemical stack is parallel to a reference plane. The anode structure comprises a population of microstructured anode active material layers, wherein (a) members of the population comprise a fibrous or porous anode active material and have (i) a surface substantially perpendicular to the reference plane, (ii) a thickness of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1. Furthermore, a linear distance between at least two members of the group measured in a direction parallel to the reference plane is greater than a maximum height of the members of the group.

Another aspect of the invention is an electrochemical stack for use in an energy storage device. The electrochemical stack includes a group of anode structures, cathode structures, and a separator layer comprising a porous dielectric material between the anode structures and the cathode structures. The anode structure, cathode structure, and separator layer are stacked in a direction substantially perpendicular to a reference plane, wherein each anode structure comprises: (a) a stem having a side surface substantially perpendicular to a reference plane and having a height of at least 50 micrometers measured in a direction substantially perpendicular to a surface of the reference plane, and (b) a microstructured anode active material layer supported by the side surface. A linear distance between at least two members of the group measured in a direction parallel to the reference plane is greater than a maximum height of the members of the group. The microstructured anode active material layer includes a back surface, a front surface, and a fibrous or porous anode active material. The microstructured anode active material layer also has a void volume fraction of at least 0.1 and a thickness between the front and back surfaces of at least 1 micron, wherein (i) the back surface of each of the layers of microstructured anode active material is adjacent to the side supporting the stems of the layer of microstructured anode active material, (ii) the front surface of each of the layers of microstructured anode active material is remote from the side supporting the stems of the layer of microstructured anode active material, (iii) the fibers comprised by the members of the group of microstructured anode active material layers are attached to the back surface of the members comprising the fibers and have a central axis that is substantially perpendicular to the plane of the back surface of the members comprising the fibers, and (iv) the holes comprised by the members of the group of microstructured anode active material layers have hole openings with major axes substantially parallel to the reference plane.

Another aspect of the invention is an energy storage device comprising a carrier ion that is lithium, sodium or potassium ions, a non-aqueous electrolyte and an electrochemical stack comprising a cathode structure, a separator layer and an anode structure arranged in a stack, the separator layer being disposed between the anode structure and the cathode structure. The stacking direction of the cathode structure, the separator layer, and the anode structure is parallel to a reference plane. The anode structure comprises a population of microstructured anode active material layers, wherein (a) members of the population comprise a fibrous or porous anode active material and have (i) a surface substantially perpendicular to the reference plane, (ii) a thickness of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1. A linear distance between at least two members of the group measured in a direction parallel to the reference plane is greater than a maximum height of any member of the group of microstructured anode active material layers.

Another aspect of the present invention is a secondary battery comprising a carrier ion, which is lithium, sodium or potassium ion, a non-aqueous electrolyte and at least two electrochemical stacks. Each of the electrochemical stacks includes a cathode structure, a separator layer, and an anode structure arranged in a stack. The separator layer is disposed between the anode structure and the cathode structure, and a stacking direction of the cathode structure, the separator layer, and the anode structure within each of the electrochemical stacks is parallel to a reference plane. The anode structure comprises a population of microstructured anode active material layers, wherein (a) members of the population comprise a fibrous or porous anode active material and have (i) a surface substantially perpendicular to the reference plane, (ii) a thickness of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1. Further, the electrochemical stacks are stacked on top of each other in a direction orthogonal to the reference plane.

Other objects and features will be in part apparent and in part pointed out hereinafter.

Drawings

Fig. 1 is a general cross-section of a cell of an electrochemical stack of a prior art two-dimensional energy storage device, such as a lithium ion battery.

Fig. 2 is a schematic example of two battery cells in a three-dimensional energy storage device (e.g., a secondary battery) of the present invention.

Fig. 3 is a fragmentary cross-sectional view of the anode active material layer containing silicon, taken along line 3-3 in fig. 2.

Fig. 4A-4E are schematic illustrations of certain shapes in which anode and cathode structures may be assembled, according to particular embodiments of the invention.

Fig. 5 is a fragmentary cross-sectional view of three dies (die), each die including an electrochemical stack.

Fig. 6 is a diagram of an anode structure of one of the dies in fig. 5.

Fig. 7 is a fragmentary cross-sectional view of the anode active material layer including porous silicon, taken along line 7-7 of fig. 6.

Fig. 8 is a schematic illustration of starting materials for the fabrication steps of the anode backbone and cathode support structure according to the present invention.

Fig. 9 is a schematic illustration of an exemplary anode backbone and cathode support structure formed in accordance with an embodiment of the method of the present invention.

Fig. 10 is a schematic example of a secondary battery of the present invention.

Fig. 11 is a schematic diagram of a 3-dimensional electrochemical stack of an energy storage device according to an alternative embodiment of the present invention.

Fig. 12 is a fragmentary schematic view of a 3-dimensional electrochemical stack of an energy storage device according to an alternative embodiment of the present invention.

Fig. 13 is a schematic diagram of an interdigitated 3-dimensional electrochemical stack of an energy storage device according to an alternative embodiment of the present invention.

Fig. 14 is a photograph of a porous silicon layer on a silicon backbone prepared as described in example 1.

Corresponding reference characters indicate corresponding parts throughout the drawings.

Detailed Description

In various aspects of the present invention, attention may be paid to such a three-dimensional structure: the three-dimensional structure provides particular advantages when incorporated in an electrochemical stack of an energy storage device such as a battery, capacitor and fuel cell. For example, the structure can be included in a secondary battery in which the anode, cathode, and/or separator are non-laminated in nature. Advantageously, the surface area of the non-laminated anode and cathode structures may exceed the geometric footprint of the substrate (base) supporting the electrodes by a factor of 1.5, 2, 2.5 or even 3 or more. In a preferred exemplary embodiment, the structure is contained in a secondary battery in which carrier ions selected from lithium, sodium and potassium ions move between an anode and a cathode.

Fig. 2 schematically illustrates an electrochemical stack of two cells in a three-dimensional battery according to one embodiment of the invention. For ease of illustration, only one anode structure 24 and two cathode structures 26 are shown in fig. 2 for each cell 20, and only two cells are present in fig. 2; however, in practice, the electrochemical stack of each cell will typically comprise a sequence of anode and cathode structures extending perpendicularly from a common reference plane, wherein the number of anode and cathode structures per cell and the number of cells in the battery depends on the application. For example, in one embodiment, the number of anode structures in the electrochemical stack is at least 10. As another example, in one embodiment, the number of anode structures in the electrochemical stack is at least 50. As another example, the number of anode structures in the electrochemical stack is at least 100.

As shown, the electrochemical stack of each cell 20 includes a substrate 22, an anode structure 24, and a cathode structure 26. Each anode structure 24 projects perpendicularly (i.e., in the Z-direction as represented by the axes in the cartesian coordinate system appearing in fig. 2) from a common reference plane, i.e., the surface of the substrate 22 (as shown), and has a bottom surface B adjacent the substrate 22, a top surface T remote from the substrate 22, and side surfaces S extending from the top surface T to the bottom surface B₁、S₂. Side S₁Intersects the surface of the substrate 22 at an angle α, and has a side S₂Intersecting the surface of the substrate 22 at an angle in a preferred embodiment α is approximately equal and between 80 and 100, for example, in one embodiment α is approximately equal and 90 + -5, in a particularly preferred embodiment α is approximately equal and about 90, independent of the angle of intersection, side S is generally preferred₁And S₂Most of the surface area of each of (neglecting surface S)₁And S₂Any of the holes) is substantially perpendicular to a reference plane, which in this embodiment is the surface of the substrate 22; in other words, the side S is generally preferred₁And S₂Most of the surface area of each of (neglecting surface S)₁And S₂Any of the holes) lie in a plane that intersects a reference plane (as shown, the surface of substrate 22) at an angle of between about 100 ° and 100 °, and more preferably at an angle of 90 ° ± 5 °. It is also generally preferred that the top surface T and the side surfaces S₁And S₂(neglecting surface S)₁And S₂Any of the holes) is substantially perpendicular and substantially parallel to a reference plane, which in this embodiment is the surface of the substrate 22. For example, in one presently preferred embodiment, the substrate 22 has a substantially planar surface, and the anode structure 24 has a top surface T that is substantially parallel to a reference plane, i.e., the planar surface of the substrate 22 in this embodiment, and a side surface S₁And S₂(neglecting surface S)₁And S₂Any of the apertures) is substantially perpendicular to the reference plane, i.e., the planar surface of the substrate 22 in this embodiment.

As shown, each anode structure 24 includes a base having a (from surface S in a direction parallel to a reference plane-i.e., the planar surface of the substrate 22, as illustrated)₃To S₄Measured) thickness T₃And each has (in a direction parallel to the reference plane, i.e. the plane surface of the substrate 22, as illustrated) a secondary surface S₁To S₃Measured) thickness T₁And (from surface S in a direction parallel to a reference plane, i.e., the planar surface of substrate 22, as illustrated₂To S₄Measured) thickness T₂And a height H (measured in a direction orthogonal to the reference plane) of the anode active material layers 30, 31_A. During charging, lithium (or other carrier) exits the cathode structure 26 and passes through a separator (not shown) into the anode active material layers 30, 31 as lithium ions generally in the direction of arrow 23. Depending on the anode active material used, lithium ions may intercalate (e.g., in the matrix of the anode material without forming an alloy) or form an alloy. During discharge, lithium ions (or other carrier ions) leave the anode active material layers 30, 31 and generally pass in the direction of arrow 21Through a separator (not shown) and into the cathode 26. As illustrated in fig. 2, the two battery cells are arranged vertically (i.e., in the Z-direction as illustrated in the figure), and the shortest distance between the anode active material layer and the cathode material of a single battery cell is measured in a direction parallel to the reference plane, i.e., in this embodiment, the substantially planar surface of the substrate 22 (i.e., in the X-Y plane as illustrated in the figure) and orthogonal to the stacking direction of the battery cells (i.e., the Z-direction as illustrated in the figure). In another embodiment, two cells are arranged horizontally (i.e., in the X-Y plane as exemplified in fig. 2), the shortest distance between the anode active material layer and the cathode material of a single cell is measured in a direction parallel to the reference plane, i.e., in this embodiment, the substantially planar surface of the substrate 22 (i.e., in the X-Y plane as exemplified in the figures), and the stacking direction of the cells is also parallel to the reference plane (i.e., in the X-Y plane as exemplified in fig. 2).

The anode stem 32 provides mechanical stability to the anode active material layers 30, 31. Typically, the anode stem 32 will have a height (in a direction parallel to the reference plane surface, i.e., the substantially planar surface of the substrate 22 as illustrated) from the back surface S of at least 1 micron₃To the rear surface S₄Measured) thickness T₃. The anode stem 32 can be significantly thicker, but generally will not have a thickness in excess of 100 microns. For example, in one embodiment, the anode stem 32 will have a thickness of about 1 micron to about 50 microns. Typically, the anode stem will have a height (measured in a direction perpendicular to a reference plane, i.e., the substantially planar surface of the substrate 22 as illustrated) of at least about 50 microns, more typically at least about 100 microns. In general, however, the anode stem 32 will typically have a height of no greater than about 10000 microns, more typically no greater than about 5000 microns. For example, in one embodiment, the anode stems 32 will have a thickness of about 5 to about 50 microns and a height of about 50 to about 5000 microns. By way of further example, in one embodiment, the anode stems 32 will have a thickness of about 5 to about 20 microns and a height of about 100 to about 1000 microns. By way of further example onlyIn other words, the anode stem 32 will have a thickness of about 5 to about 20 microns and a height of about 100 to about 2000 microns.

The anode stem 32 may be electrically conductive or electrically insulating, depending on the application. For example, in one embodiment, the anode stem 32 may be electrically conductive and may include a current collector for the anode active material layers 30, 31. In one such embodiment, the anode backbone comprises a polymer having at least about 10³A current collector of Siemens/cm conductivity. For another example, in one such embodiment, the anode stem comprises a stem having a diameter of at least about 10⁴A current collector of Siemens/cm conductivity. For another example, in one such embodiment, the anode stem comprises a stem having a diameter of at least about 10⁵A current collector of Siemens/cm conductivity. In another embodiment, the anode backbone 32 is relatively non-conductive. For example, in one embodiment, the anode trunk 32 has a conductivity of less than 10 siemens/cm. For another example, in one embodiment, the anode trunk 32 has a conductivity of less than 1 siemens/cm. For another example, in one embodiment, the anode stem 32 has a diameter of less than 10^-1Conductivity of Siemens/cm.

Anode backbone 32 can comprise any material that can be shaped, such as metal, semiconductor, organic, ceramic, and glass. Presently preferred materials include semiconductor materials such as silicon and germanium. Alternatively, however, carbon-based organic materials or metals, such as aluminum, copper, nickel, cobalt, titanium, and tungsten, may also be included in the anode backbone structure. In one exemplary embodiment, the anode stem 32 comprises silicon. For example, the silicon may be single crystal silicon, polycrystalline silicon, amorphous silicon, or a combination thereof.

The anode active material layers 30, 31 are microstructured to provide a significant void volume fraction to accommodate volume expansion and contraction as lithium ions (or other carrier ions) are incorporated into or exit the anode active material layers 30, 31 during charge and discharge. Typically, the void volume fraction of the anode active material layer is at least 0.1. Typically, however, the void volume fraction of the anode active material layer is not greater than 0.8. For example, in one embodiment, the void volume fraction of the anode active material layer is about 0.15 to about 0.75. For another example, in one embodiment, the void volume fraction of the anode active material layer is about 0.2 to about 0.7. For another example, in one embodiment, the void volume fraction of the anode active material layer is about 0.25 to about 0.6.

Depending on the composition of the microstructured anode active material layer and its method of formation, the microstructured anode active material layer may comprise a layer of macroporous, microporous, or mesoporous material or a combination thereof, such as a combination of micropores and mesopores or a combination of mesopores and macropores. Microporous materials are typically characterized by pore sizes of less than 10nm, wall sizes of less than 10nm, pore depths of 1-50 microns, and pore morphology generally characterized by "sponge-like" and irregular appearance, non-smooth walls, and branched pores. Mesoporous materials are typically characterized by a pore size of 10-50nm, a wall size of 10-50nm, a pore depth of 1-100 microns, and a pore morphology that is generally characterized by branched pores that are somewhat well defined or dendritic pores. Macroporous materials are typically characterized by a pore size greater than 50nm, a wall size greater than 50nm, a pore depth of 1-500 microns, and a pore morphology that may be variable, straight, branched, or dendritic, with smooth walls or rough walls. Further, the void volume may include open or closed voids, or a combination thereof. In one embodiment, the void volume comprises open voids, i.e., the anode active material layer comprises voids at the front surface of the anode material layer (e.g., surface S as illustrated in FIG. 2)₁、S₂) Has openings that open toward the separator and the cathode active material, and through which lithium ions (or other carrier ions) can enter or exit the anode active material layer; for example, lithium ions may enter the anode active material layer through the void openings after exiting the cathode material and traveling generally in the direction indicated by arrow 23 to the anode active material. In another embodiment, the void volume comprises closed voids, i.e., the voids comprised by the anode active material layer are surrounded by the anode active material. In general, open voids may provide a greater interfacial surface area for the carrier ions, while closedThe voids are less susceptible to a solid electrolyte interface ("SEI"), while each void provides a space for the expansion of the anode active material layer upon entry of a carrier ion. Therefore, in certain embodiments, it is preferred that the anode active material layer comprises a combination of open and closed voids.

The anode active material layers 30, 31 include an anode active material capable of absorbing and releasing carrier ions (e.g., lithium). The material includes a carbon material such as graphite, or any of certain metals, semi-metals, alloys, oxides, and compounds capable of forming alloys with lithium. Specific examples of metals or semimetals that can constitute the anode material include tin, lead, magnesium, aluminum, boron, gallium, silicon, indium, zinc, germanium, bismuth, cadmium, antimony, gold, silver, zinc, arsenic, hafnium, yttrium, and palladium. In one exemplary embodiment, the anode active material layers 30, 31 include aluminum, tin, or silicon or oxides thereof, nitrides thereof, fluorides thereof, or other alloys thereof. In another exemplary embodiment, the anode active material layers 30, 31 comprise microstructured silicon or an alloy thereof. In a particularly preferred embodiment, the anode active material layer 30, 31 comprises porous silicon or an alloy thereof, fibers of silicon or an alloy thereof (e.g. nanowires), a combination of porous silicon or an alloy thereof and fibers of silicon or an alloy thereof (e.g. nanowires), or other forms of microstructured silicon or an alloy thereof having a void volume fraction of at least 0.1. In each of the embodiments and examples cited in this paragraph and elsewhere in this patent application, the anode active material layer may be monolithic or a collection of particles.

Typically, the anode active material layers 30, 31 have front surfaces S, respectively₁、S₂Respectively have a rear surface S₃、S₄And each has a thickness T (measured in a direction parallel to the surface of the substrate 22) of at least 1 micron₁、T₂. Typically, however, each of the anode active material layers 30, 31 will have a thickness of no more than 200 microns. For example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 1 to about 100 microns. As another example, in one embodiment, the anode is activeThe material layers 30, 31 have a thickness of about 2 to about 75 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 have a thickness of about 10 to about 100 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 have a thickness of about 5 to about 50 microns. By way of further example, in one such embodiment, the anode active material layers 30, 31 have a thickness of about 1 to about 100 microns and comprise microstructured silicon and/or alloys thereof, such as nickel silicide. Further, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 1 to about 50 microns and comprise microstructured silicon and/or alloys thereof, such as nickel silicide. Generally, the anode active material layers 30, 31 will have a height H (measured in a direction perpendicular to a reference plane, i.e., the substantially planar surface of the substrate 22 as illustrated) of at least about 50 microns, more typically at least about 100 microns_A. In general, however, the anode active material layers 30, 31 will typically have a height H of no more than about 10000 microns, more typically no more than about 5000 microns_A. For example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 1 to about 200 microns and a height of about 50 to about 5000 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 1 to about 50 microns and a height of about 100 to about 1000 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 5 to about 20 microns and a height of about 100 to about 1000 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 10 to about 100 microns and a height of about 100 to about 1000 microns. By way of further example, in one embodiment, the anode active material layers 30, 31 will have a thickness of about 5 to about 50 microns and a height of about 100 to about 1000 microns.

In one embodiment, the microstructured anode active material layer 30, 31 comprises porous aluminum, tin or silicon or alloys thereof. Can be formed by anodization, by etching (e.g., by depositing gold, platinum, or gold/palladium on a (100) surface of single crystal silicon and etching the surface with a mixture of hydrofluoric acid and hydrogen peroxide)Or by other methods known in the art, such as patterned chemical etching. In addition, the anode active material layer will generally have a porosity fraction of at least about 0.1 but less than 0.8 and a thickness of about 1 to about 100 microns. For example, in one embodiment, the anode active material layers 30, 31 comprise porous silicon, have a thickness of about 5 to about 100 microns, and have a porosity of about 0.15 to about 0.75. By way of further example, in one embodiment, the anode active material layers 30, 31 comprise porous silicon, have a thickness of about 10 to about 80 microns, and have a porosity of about 0.15 to about 0.7. By way of further example, in one embodiment, the anode active material layers 30, 31 comprise porous silicon, have a thickness of about 20 to about 50 microns, and have a porosity of about 0.25 to about 0.6. By way of further example, in one embodiment, the anode active material layers 30, 31 comprise a porous silicon alloy (e.g., nickel silicide), have a thickness of about 5 to about 100 microns, and have a porosity of about 0.15 to about 0.75. In each of the above embodiments, the thickness of the anode active material layer will typically exceed the hole depth. In other words, the base of the pores (e.g., the surface of the pores adjacent to the anode stem 32 (see fig. 2)) typically does not appear at the boundary between the anode active material layer and the anode stem (i.e., surface S shown in fig. 2)₃And S₄) At least one of (1) and (b); in contrast, the boundary between the anode active material layer and the anode stem will occur at a greater depth (e.g., a greater distance measured in the direction of arrow 23 in fig. 2) from the base of the hole.

Although there may be significant variation from hole to hole, the pores of porous silicon (or alloys thereof) have a predominant axis (sometimes referred to as the central axis) in the direction of the chemical or electrochemical etching process. Referring now to fig. 3, when the anode active material layer 32 comprises porous silicon, the pores 60 will have a preponderance (predominantly) and sides S₁(see FIG. 2) a major axis 62 that is perpendicular and substantially parallel to a reference plane, which in this embodiment is a planar surface of the substrate 22. It is noted that when the battery cells are vertically stacked as illustrated in fig. 2, the major axis of the hole is aligned with the stacking direction of the battery cells (i.e., when the stacking direction is as illustrated in fig. 2)The major axes of the holes lie in the X-Y plane when in the Z direction) are substantially orthogonal.

In another embodiment, the microstructured anode active material layers 30, 31 comprise fibers of aluminum, tin, or silicon, or alloys thereof. The individual fibers may have a diameter (thickness dimension) of about 5nm to about 10000nm and a length that generally corresponds to the thickness of the microstructured anode active material layers 30, 31. The fibers (nanowires) of silicon may be formed, for example, by chemical vapor deposition or other techniques known in the art, such as vapor-liquid-solid (VLS) growth and solid-liquid-solid (SLS) growth. In addition, the anode active material layer will generally have a porosity of at least about 0.1 but less than 0.8 and a thickness of about 1 to about 200 microns. For example, in one embodiment the anode active material layers 30, 31 comprise silicon nanowires, have a thickness of about 5 to about 100 microns, and have a porosity of about 0.15 to about 0.75. By way of further example, in one embodiment, the anode active material layers 30, 31 comprise silicon nanowires, have a thickness of about 10 to about 80 microns, and have a porosity of about 0.15 to about 0.7. By way of further example, in one such embodiment, the anode active material layers 30, 31 comprise silicon nanowires, have a thickness of about 20 to about 50 microns, and have a porosity of about 0.25 to about 0.6. By way of further example, in one embodiment, the anode active material layers 30, 31 comprise nanowires of a silicon alloy (e.g., nickel silicide), have a thickness of about 5 to about 100 microns, and have a porosity of about 0.15 to about 0.75.

Although there may be significant differences from fiber to fiber, nanowires of aluminum, tin or silicon (or alloys thereof) have a major axis (sometimes referred to as the central axis) predominantly perpendicular to the anode backbone (at the point where the nanowire is attached to the microstructured anode active material layer) and parallel to the surface of the substrate supporting the backbone (see fig. 2). It is noted that when the battery cells are vertically stacked as shown in fig. 2, the major axis of the fibers is substantially orthogonal to the stacking direction of the battery cells.

In another embodiment, the microstructured anode active material layer 30, 31 comprises nanowires of silicon or alloys thereof and porous silicon or alloys thereof. In this embodiment, the anode active material layer will generally have a porosity of at least about 0.1 but less than 0.8 and a thickness of about 1 to about 100 microns, as previously described in connection with porous silicon and silicon nanowires.

Referring again to fig. 2, the substrate 22 serves as a rigid backplate (backplane) and may be constructed of any of a variety of materials. For example, the substrate 22 may comprise any of a ceramic, glass, polymer, or a range of other materials that provide sufficient rigidity to the overall structure. In one embodiment, the substrate 22 is insulating; for example, the substrate 22 may have a conductivity of less than 10 siemens/cm. In one exemplary embodiment, the substrate 22 may comprise a silicon-on-insulator structure. However, in other embodiments, the substrate 22 may be removed after the electrochemical stack is formed.

Referring now to fig. 4A-4E, anode structures 24 and cathode structures 26 protrude from the same reference plane, in this embodiment, the planar surface of substrate 22, and alternate in a periodic manner. Furthermore, in each of fig. 4A-4E, each anode structure 24 includes at least one side surface located between its bottom and top surfaces, as described more fully in connection with fig. 2, to support a group of microstructured anode active material layers 30. For example, when the anode structure 24 is cylindrical (fig. 4A), the microstructured anode active material layer extends at least partially and preferably completely around the perimeter of the side. By way of further example, when the anode structure 24 has two (or more) sides, for example as illustrated in fig. 4B-4E, the anode active material layer at least partially covers, and preferably completely covers, at least one of the sides. Furthermore, each microstructured anode active material layer in the group has a height (measured in a direction perpendicular to the substrate 22) and the layers are arranged such that: a linear distance (D) between at least two layers of the group, such as layers 30A and 30B, measured in a direction substantially parallel to the planar surface of substrate 22_L) Greater than the maximum height of any layer in the group (i.e., there is a linear distance D separated in the group of anode active material layers)_LAt least one pair of anode active material layers, the straight distance D_LExceeds the height H of the anode active material layer having the largest height among all the anode active material layers in the group_A). For example, in one embodiment, a straight-line distance (D) between at least two layers in the group (e.g., layers 30A and 30B)_L) At least 2 times, and in certain embodiments, substantially at least 5 times or even at least 10 times, the maximum height of any layer in the group. As another example, in one embodiment, the linear distance (D) between most of the layers in the group_L) At least 2 times, and in other embodiments substantially at least 5 times or even at least 10 times, the maximum height of any layer in the group.

Fig. 4A shows a three-dimensional assembly with an anode structure 24 and a cathode structure 26 in the shape of pillars (pilars). Each post includes a stem having sides (not shown) that project perpendicularly from the base 22. The side of each stem supports an anode active material layer 30, and the layers 30 are arranged such that: the straight-line distance between at least two layers in the group (e.g., the straight-line distance between layers 30A and 30B) is greater than the maximum height of any layer in the group. For example, in one embodiment, the linear distance (D) between members of at least one pair of anode active material layers in a group (i.e., at least one of any possible pair of two anode active material layers in a group)_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. For another example, in one embodiment, the linear distance (D) between most of the anode active material layers in a group_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group.

Fig. 4B shows a three-dimensional assembly with a cathode structure 26 and an anode structure 24 in the shape of plates (plates). Each plate includes a stem having sides (not shown) projecting perpendicularly from the base 22. The side of each stem supports an anode active material layer 30, and the layers 30 are arranged such that: linear distance between at least two layers in a groupGreater than the maximum height of any layer in the group, e.g., the straight-line distance between layers 30A and 30B. For example, in one embodiment, the linear distance (D) between members of at least one pair of anode active material layers in a group (i.e., at least one of any possible pair of two anode active material layers in a group)_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. For another example, in one embodiment, the linear distance (D) between most of the anode active material layers in a group_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group.

Fig. 4C shows a three-dimensional assembly of cathode structure 26 and anode structure 24 having concentric circular shapes. Each concentric circle includes a stem having sides (not shown) projecting perpendicularly from the base 22. The side of each stem supports an anode active material layer 30, and the layers 30 are arranged such that: the straight-line distance between at least two layers in the group (e.g., the straight-line distance between layers 30A and 30B) is greater than the maximum height of any layer in the group. For example, in one embodiment, the linear distance (D) between members of at least one pair of anode active material layers in a group (i.e., at least one of any possible pair of two anode active material layers in a group)_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. For another example, in one embodiment, the linear distance (D) between most of the anode active material layers in a group_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group.

Fig. 4D shows a three-dimensional assembly with a corrugated cathode structure 26 and an anode structure 24. Each wave includes a stem having sides (not shown) projecting perpendicularly from the base 22. Side of each trunkThe anode active material layer 30 is supported, and the layer 30 is disposed such that: the straight-line distance between at least two layers in the group (e.g., the straight-line distance between layers 30A and 30B) is greater than the maximum height of any layer in the group. For example, in one embodiment, the straight-line distance (D) between two members of any pair of anode active material layers in a group (i.e., any possible pair of two anode active material layers in a group)_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. For another example, in one embodiment, the linear distance (D) between most of the anode active material layers in a group_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group.

Fig. 4E shows a three-dimensional assembly of cathode structures 26 and anode structures 24 having a honeycomb pattern. The cathode structure 26 is a cylinder located at the center of each unit cell of the honeycomb structure, and the walls of each unit cell of the honeycomb structure include an interconnected backbone network (system) having sides (not shown) protruding perpendicularly from the base 22. The side of the backbone network (system) supports the anode active material layer 30, and the layer 30 is arranged such that: the straight-line distance between at least two layers in the group (e.g., layers 30A and 30B) is greater than the maximum height of any layer in the group. For example, in one embodiment, the straight-line distance (D) between two members of any pair of anode active material layers in a group (i.e., any possible pair of two anode active material layers in a group)_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. For another example, in one embodiment, the linear distance (D) between most of the anode active material layers in a group_L) At least 2 times, and in certain embodiments substantially, e.g., at least 5 times or even at least 10 times, the maximum height of any anode active material layer in the group. In the alternativeIn an embodiment, the three-dimensional assembly is a honeycomb structure, but the relative positions of the anode structure and the cathode structure are reversed relative to the embodiment shown in fig. 4E, i.e., in an alternative embodiment, the anode structure is cylindrical (having sides supporting the anode active material layer) and the walls of each unit cell include the cathode active material.

Independent of the geometry of the anode structure, in one embodiment, the electrochemical stack comprises a group of microstructured anode active material layers, the group having at least 20 anode active material layers as members. For example, in one embodiment, the group includes at least 50 members. For another example, in one embodiment, the group includes at least 100 members. In other embodiments, the group may include at least 150, at least 200, or even at least 500 members.

Referring now to fig. 5, the die stack 14 includes three dies, each die 20 including a substrate 22 and an electrochemical stack including an alternating sequence of anode structures 24 and cathode structures 26 protruding from the substrate 22. Each anode structure 24 includes an anode stem 32, a microstructured anode active material layer 31, and an anode current collector 28. Each anode active material layer 31 of the anode structure 24 has a height H (measured in a direction orthogonal to the substrate 22)_A. Each cathode structure 26 includes a cathode material 27, a cathode current collector 34, and a cathode backbone 36. A separator 38 is located between each anode structure 24 and each cathode structure 26. In one embodiment, substrate 22 is removed and anode structure 24 and cathode structure 26 protrude from a common reference plane that is parallel to substrate 22.

For ease of illustration, only two anode structures 24 and only one cathode structure 26 are shown in fig. 5 for each die 20, and only three dies are present in the vertical stack shown in fig. 5; however, in practice, each die will typically comprise an electrochemical stack comprising an alternating sequence of anode structures and cathode structures, the number of anode structures and cathode structures per electrochemical stack and the number of dies in a vertical stack depending on the application. For lithium ion batteries for portable electronic devices, such as mobile phones and computers, for example, each die may contain from about 20 to about 500 anode structures, and an approximately equal number of cathode structures. For example, in one embodiment, each die contains at least 20, at least 50, at least 100, at least 150, at least 200, or even at least 500 anode structures and an approximately equal number of cathode structures. The size of the die may also vary substantially depending on the application. For lithium ion batteries for portable electronic devices, such as mobile phones and computers, for example, each die may have dimensions of 50mm (l) by 50mm (w) by 5mm (h). Furthermore, in one embodiment, the dies are preferably stacked relative to each other in a direction orthogonal to the stacking direction of the anode structure, the separator layer and the cathode structure within the electrochemical stack of the dies; in other words, each die is preferably stacked in a direction orthogonal to the substantially planar surface (or common reference plane) of each substrate 22 of a single die. In an alternative embodiment, the dies are preferably stacked relative to each other in a direction parallel to the stacking direction of the anode structure, the separator layer and the cathode structure within the electrochemical stack of the dies; in other words, each die is preferably stacked in a direction lying in a plane parallel to the substantially planar surface (or common reference plane) of each substrate 22 of a single die.

The substrate 22 serves as a rigid backplate and may be constructed of any of a variety of materials. As previously mentioned, the substrate 22 may comprise any of a ceramic, glass, polymer, or range of other materials that provide sufficient rigidity and electrical insulation to the overall structure. In one embodiment, the substrate 22 is removed or omitted (assuming that some structure or means is provided to avoid electrical shorting between the anode and cathode structures), and the anode and cathode structures protrude from a common reference plane (rather than the common substrate).

The overall size of the anode structure 24 may depend in part on the application and in part on manufacturing considerations. For lithium ion batteries for portable electronic devices, such as mobile phones and computers, for example, each anode structure 24 will typically beAnd has a height (measured in a direction perpendicular to substrate 22) of at least about 50 microns, and more typically at least about 100 microns. In general, however, the anode structure will typically have a height of no greater than about 10000 microns, more typically no greater than about 5000 microns. Furthermore, the linear distance between at least one pair (not shown) of anode active material layers 31 of the same electrochemical stack 20 preferably exceeds the maximum height H of the members of the group of anode active material layers in the same electrochemical stack_A。

Referring again to fig. 5, each anode structure 24 includes an anode current collector layer 28, the anode current collector layer 28 overlying and in contact with an anode active material layer 31, which in turn overlies and is in contact with an anode stem 32. Thus, as the carrier ions move between the anode active material and the cathode active material in such an electrochemical stack, they pass through the anode current collector layer 28 located between the separator and the anode active material layer. In this embodiment, the anode current collector layer 28 comprises an ion-permeable conductor having sufficient ion permeability to the carrier ions to facilitate movement of the carrier ions from the separator to the anode active material layer, and sufficient electrical conductivity to enable it to function as a current collector.

The anode current collector layer, by virtue of being located between the anode active material layer and the separator, can facilitate more uniform transport of carrier ions by distributing the current from the anode current collector across the surface of the anode active material layer. This in turn may promote more uniform insertion and extraction of carrier ions, thereby reducing stress in the anode active material during cycling; the anode current collector layer thus distributes the current to the surface of the anode active material layer facing the separator, so that the reactivity of the anode active material layer of the carrier ions will be greatest where the concentration of the carrier ions is greatest.

In this embodiment, the anode current collector layer comprises an ion-permeable conductor that is both ionically and electrically conductive. In other words, the anode current collector layer has a thickness, an electrical conductivity, and an ionic conductivity of carrier ions that facilitates movement of carrier ions between the active electrode material layer directly adjacent one side of the ionically permeable conductor layer and the separator layer directly adjacent the other side of the anode current collector layer in the electrochemical stack. On a relative basis, the anode current collector layer has a conductivity greater than its ionic conductivity in the presence of an applied current to store energy in the device or an applied load to discharge the device. For example, the ratio of the electrical conductivity of the anode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 1000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the anode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 5000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the anode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 10000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the anode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 50000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the anode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 100000:1 when there is an applied current to store energy in the device or an applied load to discharge the device.

In one embodiment and when there is an applied current to store energy in the device or an applied load to discharge the device, for example when the secondary battery is charging or discharging, the anode current collector layer has an ionic conductivity comparable to that of the adjacent separator layer. For example, in one embodiment, the anode current collector layer has an ionic conductivity (of the carrier ions) that is at least 50% (i.e., a ratio of 0.5: 1) of the ionic conductivity of the separator layer when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the anode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the anode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1.25:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the anode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1.5:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the anode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 2:1 when there is an applied current to store energy in the device or there is an applied load to discharge the device.

In one embodiment, the anode current collector layer also has an electrical conductivity that is substantially greater than an electrical conductivity of the anode active material layer. For example, in one embodiment, the ratio of the electrical conductivity of the anode current collector layer to the electrical conductivity of the anode active material layer is at least 100:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the anode current collector layer to the electrical conductivity of the anode active material layer is at least 500:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the anode current collector layer to the electrical conductivity of the anode active material layer is at least 1000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the anode current collector layer to the electrical conductivity of the anode active material layer is at least 5000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the anode current collector layer to the electrical conductivity of the anode active material layer is at least 10000:1 when there is an applied current to store energy in the device or an applied load to discharge the device.

The thickness of the anode current collector layer in this embodiment (i.e., the shortest distance between the separator between which the anode current collector layer is sandwiched and the anode active material layer) will depend on the composition of the layer and the performance specifications of the electrochemical stack. Typically, when the anode current collector layer is an ion-permeable conductor layer, it will have a thickness of at least about 300 angstroms. For example, in some embodiments, it may have a thickness in the range of about 300 and 800 angstroms. More typically, however, it will have a thickness greater than about 0.1 microns. Typically, the ion-permeable conductor layer will have a thickness of no greater than about 100 microns. Thus, for example, in one embodiment, the anode current collector layer will have a thickness in the range of about 0.1 to about 10 microns. For another example, in certain embodiments, the anode current collector layer will have a thickness in the range of about 0.1 to about 5 microns. For another example, in certain embodiments, the anode current collector layer will have a thickness in the range of about 0.5 to about 3 microns. Generally, it is preferred that the thickness of the anode current collector layer is substantially uniform. For example, in one embodiment, it is preferred that the anode current collector layer have a thickness non-uniformity of less than about 25%, wherein the thickness non-uniformity is defined as the maximum thickness of the layer minus the minimum thickness of the layer divided by the average layer thickness. In certain embodiments, the thickness difference is even smaller. For example, in certain embodiments, the anode current collector layer has a thickness non-uniformity of less than about 20%. For another example, in certain embodiments, the anode current collector layer has a thickness non-uniformity of less than about 15%. In certain embodiments, the ionically permeable conductor layer has a thickness non-uniformity of less than about 10%.

In a preferred embodiment, the anode current collector layer is an ion-permeable conductor layer comprising an electrically conductive component and an ion-conductive component that contribute to ion permeability and electrical conductivity. Typically, the conductive composition will comprise a continuous conductive material (e.g., a continuous metal or metal alloy), a film, or a composite material comprising a continuous conductive material (e.g., a continuous metal or metal alloy) in the form of a mesh or patterned surface. Furthermore, the ion-conducting component will typically comprise pores, such as interstitial spaces, spaces between layers of material comprising a patterned metal or metal alloy, pores in a metal film, or a solid ion conductor with sufficient diffusivity for carrier ions. In particular embodiments, the ion-permeable conductor layer comprises a deposited porous material, ion-transport material, ion-reactive material, composite material, or physical porous material. For example, if porous, the ion-permeable conductor layer may have a void fraction of at least about 0.25. In general, however, the void fraction will typically not exceed about 0.95. More typically, when the ion-permeable conductor layer is porous, the void fraction may be in the range of about 0.25 to about 0.85. In certain embodiments, for example, when the ion-permeable conductor layer is porous, the void fraction may be in the range of about 0.35 to about 0.65.

In the embodiment illustrated in fig. 5, the anode current collector layer 28 is a separate (sole) anode current collector for the anode active material layer 31. In other words, in this embodiment, the anode trunk 32 does not include an anode current collector. However, in certain other embodiments, the anode stem 32 may optionally include an anode current collector.

Each cathode structure 26 may contain any of a range of cathode active materials 27, including mixtures of cathode active materials. For example, for lithium ion batteries, cathode materials, e.g. LiCoO₂、LiNi_0.5Mn_1.5O₄、Li(Ni_xCo_yAl₂)O₂、LiFePO₄、Li₂MnO₄、V₂O₅And molybdenum oxysulfide. The cathode active material may be deposited to form the cathode structure by any of a range of techniques including, for example, electrophoretic deposition, electrodeposition, co-deposition, or slurry deposition. In one exemplary embodiment, one or a combination of the above-described cathode active materials in the form of particles is electrophoretically deposited. In another exemplary embodiment, such as V₂O₅The anode active material of (2) is electrodeposited. In another exemplary embodiment, one or a combination of the above-described cathode active materials in particle form are co-deposited in a conductive matrix such as polyaniline. In another exemplary embodiment, one or a combination of the above-described cathode active materials in the form of particles is deposited by the slurry. Independently of the deposition method, the cathode active material layer will typically have a thickness between 1 micron and 1 mm. In particular embodiments, the layer thickness is between 5 and 200 microns, and in particular embodiments, the layer thickness is between 10 and 150 microns.

Each cathode structure also includes a cathode current collector 34, and in the embodiment illustrated in fig. 5, the cathode current collector 34 overlies a cathode support 36. The cathode Current collector 34 may include any metal previously identified for an anode Current collector, for example, in one embodiment, the cathode Current collector 34 includes aluminum, carbon, chromium, gold, nickel, NiP, palladium, platinum, rhodium, ruthenium, alloys of silicon and nickel, titanium, or combinations thereof (see "Current collectors for reactive electrodes of lithium-based batteries" by A. H. Whitehead and M. Schreiber, Journal of the electrochemical society,152(11) A2105-A2113 (2005)). By way of further example, in one embodiment, the cathode current collector layer 34 comprises gold or an alloy thereof, such as gold silicide. By way of further example, in one embodiment, the cathode current collector layer 34 comprises nickel or an alloy thereof, such as nickel silicide.

Similarly, the cathode support 36 may comprise any material previously identified for the anode backbone. Presently preferred materials include semiconductor materials such as silicon and germanium. Alternatively, however, carbon-based organic materials or metals, such as platinum, rhodium, aluminum, gold, nickel, cobalt, titanium, tungsten, and alloys thereof, may also be included in the cathode support structure. Typically, the cathode support will have a thickness of at least about 50 microns, more typically at least about 100 microns, and any of a range of thicknesses (including a minimum) allowed by the manufacturing method used. In general, however, the cathode support 36 will typically have a height of no greater than about 10000 microns, more typically no greater than about 5000 microns. Further, in this embodiment, the cathode current collector 34 will have a thickness in the range of about 0.5 to 50 microns.

In an alternative embodiment, the positions of the cathode current collector layer and the cathode active material layer are reversed relative to their positions shown in fig. 5. In other words, in certain embodiments, the cathode current collector layer is located between the separator layer and the cathode active material layer. In such embodiments, the cathode current collector for the immediately adjacent cathode active material layer comprises an ion-permeable conductor having the composition and structure described in connection with the anode current collector layer; that is, the cathode current collector layer includes an ion-permeable conductor material layer that is both ionically and electrically conductive. In this embodiment, the cathode current collector layer has a thickness, electrical conductivity, and ionic conductivity of the carrier ions that facilitate movement of the carrier ions between the cathode active electrode material layer directly adjacent one side of the cathode current collector layer and the separator layer directly adjacent the other side of the cathode current collector layer in the electrochemical stack. On a relative basis, in this embodiment, the cathode current collector layer has a conductivity greater than its ionic conductivity when there is an applied current to store energy in the device or an applied load to discharge the device. For example, the ratio of the electrical conductivity of the cathode collector layer to the ionic conductivity (of the carrier ions) is typically at least 1000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the cathode collector layer to the ionic conductivity (of the carrier ions) is typically at least 5000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the cathode collector layer to the ionic conductivity (of the carrier ions) is typically at least 10000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the cathode current collector layer to the ionic conductivity (of the carrier ions) is typically at least 50000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in one such embodiment, the ratio of the electrical conductivity of the cathode collector layer to the ionic conductivity (of the carrier ions) is typically at least 100000:1 when there is an applied current to store energy in the device or an applied load to discharge the device.

In this embodiment, the cathode current collector layer has an ionic conductivity comparable to that of the adjacent separator layer when there is an applied current to store energy in the device or an applied load to discharge the device, for example, when the secondary battery is being charged or discharged. For example, in one embodiment, the cathode current collector layer has an ionic conductivity (of the carrier ions) that is at least 50% (i.e., a ratio of 0.5: 1) of the ionic conductivity of the separator layer when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the cathode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the cathode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1.25:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the cathode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 1.5:1 when there is an applied current to store energy in the device or an applied load to discharge the device. By way of further example, in certain embodiments, the ratio of the ionic conductivity (of the carrier ions) of the cathode current collector layer to the ionic conductivity (of the carrier ions) of the separator layer is at least 2:1 when there is an applied current to store energy in the device or there is an applied load to discharge the device.

In this embodiment, in which the cathode current collector layer is located between the cathode active material layer and the separator, the cathode current collector includes an ionically permeable conductor layer having a conductivity that is substantially greater than the conductivity of the cathode active material layer. For example, in one embodiment, the ratio of the electrical conductivity of the cathode current collector layer to the electrical conductivity of the cathode active material layer is at least 100:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the cathode current collector layer to the electrical conductivity of the cathode active material layer is at least 500:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the cathode current collector layer to the electrical conductivity of the cathode active material layer is at least 1000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the cathode current collector layer to the electrical conductivity of the cathode active material layer is at least 5000:1 when there is an applied current to store energy in the device or an applied load to discharge the device. For another example, in certain embodiments, the ratio of the electrical conductivity of the cathode current collector layer to the electrical conductivity of the cathode active material layer is at least 10000:1 when there is an applied current to store energy in the device or there is an applied load to discharge the device.

The thickness of the cathode current collector layer in this embodiment (i.e., the shortest distance between the separator and the cathode active material layer between which the cathode current collector layer is sandwiched) will depend on the composition of the layer and the performance specifications of the electrochemical stack. Typically, when the cathode collector layer is an ion-permeable conductor layer, it will have a thickness of at least about 300 angstroms. For example, in some embodiments, it may have a thickness in the range of about 300 and 800 angstroms. More typically, however, it will have a thickness greater than about 0.1 microns. In this embodiment, the cathode current conductor will typically have a thickness of no greater than about 100 microns. Thus, for example, in one embodiment, the cathode current collector layer will have a thickness in the range of about 0.1 to about 10 microns. For another example, in certain embodiments, the cathode current collector layer will have a thickness in the range of about 0.1 to about 5 microns. For another example, in certain embodiments, the cathode current collector layer will have a thickness in the range of about 1 to about 3 microns. In general, it is preferable that the thickness of the cathode current collector layer is substantially uniform. For example, in one embodiment, it is preferred that the ionically permeable conductor layer have a thickness non-uniformity (cathode current conductor) of less than about 25%, where the thickness non-uniformity is defined as the maximum thickness of the layer minus the minimum thickness of the layer divided by the average layer thickness. In certain embodiments, the thickness difference is even smaller. For example, in certain embodiments, the cathode current collector layer has a thickness non-uniformity of less than about 20%. For another example, in certain embodiments, the cathode current collector layer has a thickness non-uniformity of less than about 15%. In certain embodiments, the cathode current collector layer has a thickness non-uniformity of less than about 10%.

In a preferred embodiment, the cathode current collector layer is an ion-permeable conductor layer that includes a conductive component that contributes to ion permeability and conductivity and an ion-conductive component, as described in connection with the anode current collector. Typically, the conductive composition will comprise a continuous conductive material (e.g., a continuous metal or metal alloy), a film, or a composite material comprising a continuous conductive material (e.g., a continuous metal or metal alloy) in the form of a mesh or patterned surface. Furthermore, the ion-conducting component will typically comprise pores, such as grid gaps, spaces between layers of material comprising a patterned metal or metal alloy, pores in a metal film, or a solid ion conductor with sufficient diffusivity for carrier ions. In particular embodiments, the ion-permeable conductor layer comprises a deposited porous material, ion-transport material, ion-reactive material, composite material, or physical porous material. For example, if porous, the ion-permeable conductor layer may have a void fraction of at least about 0.25. In general, however, the void fraction will typically not exceed about 0.95. More typically, when the ion-permeable conductor layer is porous, the void fraction may be in the range of about 0.25 to about 0.85. In certain embodiments, for example, when the ion-permeable conductor layer is porous, the void fraction may be in the range of about 0.35 to about 0.65.

In one embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e., anode collector layer or cathode collector layer) comprises a mesh between the separator layer and the electrode active material layer. The grid has gaps defined by grid lines of conductive material. For example, when the electrode active material layer is an anode active material layer, the mesh may include wires of carbon, cobalt, chromium, copper, nickel, titanium, or an alloy of one or more thereof. By way of further example, when the electrode active material layer is a cathode active material layer, the mesh may include wires of aluminum, carbon, chromium, gold, NiP, palladium, rhodium, ruthenium, titanium, or an alloy of one or more thereof. Typically, the thickness of the mesh (i.e., the diameter of the mesh lines) is at least about 2 microns. In one exemplary embodiment, the mesh has a thickness of at least about 4 microns. In another exemplary embodiment, the mesh has a thickness of at least about 6 microns. In another exemplary embodiment, the mesh has a thickness of at least about 8 microns. In each of the above embodiments, the open area fraction of the mesh (i.e., the fraction of voids between the constituent mesh lines of the mesh) is preferably at least 0.5. For example, in each of the above embodiments, the open area fraction of the mesh may be at least 0.6. As another example, in each of the above embodiments, the open area fraction of the mesh may be at least 0.75. As another example, in each of the above embodiments, the open area fraction of the mesh may be at least 0.8. However, in general, in each of the above-described embodiments, the ratio of the average distance between the grid lines to the thickness of the electrode active material layer is not more than 100:1, respectively. For example, in each of the above-described embodiments, the ratio of the average distance between the grid lines to the thickness of the electrode active material layer is not more than 50:1, respectively. As another example, in each of the above-described embodiments, the ratio of the average distance between the grid lines to the thickness of the electrode active material layer is not more than 25:1, respectively. Advantageously, one or both ends of the mesh may be welded or otherwise connected to metal tabs or other connections to enable the collected current to be carried to the environment outside the battery.

In one embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e. anode collector layer or cathode collector layer) comprises a grid of metal or its alloys as described previously, and the interstices between the grid lines are open, filled with a porous material impregnated with an electrolyte, or they may contain such a non-porous material: the carrier ions can diffuse through the non-porous material. When filled with a porous material, the porous material will typically have a void fraction of at least about 0.5, and in certain embodiments, the void fraction will be at least 0.6, 0.7, or even at least about 0.8. Exemplary porous materials include, for example, SiO₂、Al₂O₃SiC or Si₃N₄And an agglomerate of a particulate polymer such as polyethylene, polypropylene, polymethylmethacrylate, and copolymers thereof. Exemplary non-porous materials that can be placed in the interstices of the mesh include solid ionic conductors, such as Na₃Zr₂Si₂PO₁₂(NASICON)、Li_2+2xZn_1-xGeO₄(LISICON) and lithium phosphorus oxynitride (LiPON).

In one embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e., anode collector layer or cathode collector layer) comprises an electrically conductive wire deposited or otherwise formed on a surface of an immediately adjacent separator layer or an immediately adjacent electrode active material layer (i.e., an immediately adjacent anode active material layer or an immediately adjacent cathode active material layer). In this embodiment, the conductive wire may comprise any metal (or alloy thereof) previously determined in connection with the composition of the mesh. For example, when the ion-permeable conductor layer is located between the separator layer and the anode active material layer, the conductive line may comprise carbon, cobalt, chromium, copper, nickel, titanium, or an alloy of one or more thereof. When an ion-permeable conductor layer is located between the separator layer and the cathode active material layer, the conductive line can include aluminum, carbon, chromium, gold, NiP, palladium, rhodium, ruthenium, titanium, or an alloy of one or more thereof. Typically, the conductive lines will have a thickness of at least about 2 microns. In one exemplary embodiment, the conductive line has a thickness of at least about 4 microns. In another exemplary embodiment, the conductive line has a thickness of at least about 6 microns. In another exemplary embodiment, the conductive line has a thickness of at least about 8 microns. In each of the above embodiments, the ratio of the average distance between the conductive lines to the thickness of the electrode active material layer is not more than 100:1, respectively. For example, in each of the above-described embodiments, the ratio of the average distance between the conductive lines to the thickness of the electrode active material layer is not more than 50:1, respectively. As another example, in each of the above-described embodiments, the ratio of the average distance between the conductive lines to the thickness of the electrode active material layer is not greater than 25:1, respectively. Advantageously, one or more ends of the conductive wires may be welded or otherwise connected to metal tabs or other connections to enable the collected current to be carried to the environment outside the battery.

In one embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e. anode collector layer or cathode collector layer) comprises electrically conductive wires of a metal or an alloy thereof as described previously, the spaces on the surface of the coated material may be open, they may be filled with a porous material impregnated with an electrolyte, or they may contain such a non-porous material: the carrier ions can diffuse through the non-porous material. When filled with a porous material, the porous material will typically have a void fraction of at least about 0.5, and in certain embodiments, the void fraction will be at least 0.6, 0.7, or even at least about 0.8. Exemplary porous materials include, for example, SiO₂、Al₂O₃SiC or Si₃N₄And an agglomerate of a particulate polymer such as polyethylene, polypropylene, polymethylmethacrylate, and copolymers thereof. Exemplary non-porous materials that can be placed between conductive wires include solid ionic conductors, such as Na₃Zr₂Si₂PO₁₂(NASICON)、Li_2+2xZn_1-xGeO₄(LISICON) and lithium phosphorus oxynitride (LiPON).

In one embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e. the anode collector layer or the cathode collector layer) comprises a porous layer or membrane, such as a porous metal layer. For example, when the electrode active material layer is an anode active material layer, the porous layer may include a porous layer of carbon, cobalt, chromium, copper, nickel, titanium, or an alloy of one or more thereof. By way of further example, when the electrode active material layer is a cathode active material layer, the porous layer may include a porous layer of aluminum, carbon, chromium, gold, NiP, palladium, rhodium, ruthenium, titanium, or an alloy of one or more thereof. Exemplary deposition techniques to form such porous layers include electroless deposition, electrodeposition, vacuum deposition techniques such as sputtering, displacement plating, vapor deposition techniques such as chemical vapor deposition and physical vapor deposition, co-deposition followed by selective etching, and slurry coating of metal particles using a binder. Generally, it is preferred that such porous layers have a void fraction of at least 0.25. For example, in one embodiment, the porous metal layer will have a void fraction of at least 0.4, at least 0.5, at least 0.6, at least 0.7, up to about 0.75. To provide the desired conductivity, the layer will typically have a thickness of at least about 1 micron. In certain embodiments, the layer will have a thickness of at least 2 microns. In certain embodiments, the layer will have a thickness of at least 5 microns. In general, however, the layer will typically have a thickness of no more than 20 microns, more typically no more than about 10 microns. Alternatively, such a metal layer or film may contain a binder, such as polyvinylidene fluoride (PVDF), or other polymeric or ceramic materials.

In yet another alternative embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e. the anode collector layer or the cathode collector layer) comprises a metal-filled ion-conducting polymer composite membrane. For example, the ion-permeable conductor layer may comprise an ion-conducting membrane such as polyethylene oxide or a gelled polymer electrolyte containing a conductive element such as aluminum, carbon, gold, titanium, rhodium, palladium, chromium, NiP, or ruthenium, or alloys thereof. Typically, however, solid-state ionic conductors have relatively low ionic conductivity, and thus the layer needs to be relatively thin to provide the desired ionic conductivity. For example, such layers may have a thickness in the range of about 0.5 to about 10 microns.

In yet another alternative embodiment, the ion-permeable conductor layer comprised by the electrode collector layer (i.e. the anode collector layer or the cathode collector layer) comprises a porous layer of a metal or metal alloy, preferably which does not form intermetallic compounds with lithium. In this embodiment, for example, the ionically permeable conductor layer may comprise at least one metal selected from copper, nickel and chromium or alloys thereof. For example, in one such embodiment, the electrode current collector layer comprises porous copper, porous nickel, a porous alloy of copper or nickel, or a combination thereof. By way of further example, in one such embodiment, the electrode current collector layer comprises porous copper or an alloy thereof, such as porous copper silicide. By way of further example, in one such embodiment, the electrode current collector layer comprises porous nickel or a porous alloy thereof, such as porous nickel silicide. In each of the above-described embodiments recited in this paragraph, the thickness of the electrode collector layer (i.e., the shortest distance between an immediately adjacent electrode active material layer and an immediately adjacent separator layer) will generally be at least about 0.1 microns, typically in the range of about 0.1 to 10 microns. In each of the above embodiments recited in this paragraph, the electrode current collector layer may be porous with a void fraction in the range of about 0.25 to about 0.85, and in particular embodiments, in the range of about 0.35 to about 0.45.

In a preferred embodiment, the anode current collector layer is formed by a method comprising a displacement plating step. In this embodiment, the anode active material layer preferably includes silicon, and the layer is contacted with a solution containing metal ions and a dissolving component for dissolving part of the silicon. Silicon is dissolved, the metal in the solution is reduced by electrons provided by the dissolution of silicon, and the metal is deposited on the anode active material layer and annealed to form a metal-silicon alloy layer. "dissolution component" refers to a component that promotes dissolution of the semiconductor material. The dissolved components include fluorides, chlorides, peroxides, hydroxides, permanganates, and the like. Preferred dissolution components are fluorides and hydroxides. The most preferred dissolution component is fluoride. The metal may be any of the above metals, preferably nickel and copper. Advantageously, the resulting layer will be porous, having a void fraction of about 0.15 to about 0.85. Furthermore, the thickness of the resulting ion-permeable conductor layer can be controlled between about 100 nanometers and 3 microns; thicker layers may be formed if desired.

Referring again to fig. 5, a separator layer 38 is located between each anode structure 24 and each cathode structure 26. The separator layer 38 may comprise any material conventionally used as a secondary battery separator including, for example, microporous polyethylene, polypropylene, TiO₂、SiO₂、Al₂O₃And so on (P.Arora and J.Zhang, "Battery Separators" chemical reviews2004,104, 4419-4462). Such materials may be deposited, for example, by electrophoretic deposition of a particulate separator material, slurry deposition of a particulate separator material (including spin coating or spray coating), or sputter coating of an ion conducting particulate separator material. Separator layer 38 can have a thickness (distance separating adjacent anode structures and adjacent cathode structures) of, for example, about 5 to 100 microns and a void fraction of about 0.25 to about 0.75.

In operation, the separator may be permeated with a nonaqueous electrolyte containing any nonaqueous electrolyte conventionally used for nonaqueous electrolyte secondary batteries. Typically, the nonaqueous electrolyte includes a lithium salt dissolved in an organic solvent. Exemplary lithium salts include: inorganic lithium salts, e.g. LiClO₄、LiBF₄、LiPF₆、LiAsF₆LiCl and LiBr; and organic lithium salts, e.g. LiB (C)₆H₅)₄、LiN(SO₂CF₃)₂、LiN(SO₂CF₃)₃、LiNSO₂CF₃、LiNSO₂CF₅、LiNSO₂C₄F₉、LiNSO₂C₅F₁₁、LiNSO₂C₆F₁₃And LiNSO₂C₇F₁₅. Exemplary organic solvents that dissolve the lithium salt include cyclic esters, chain esters, cyclic ethers, and chain ethers. Specific examples of the cyclic ester include propylene carbonate, butylene carbonate, γ -butyrolactone, vinylene carbonate, 2-methyl- γ -butyrolactone, acetyl- γ -butyrolactone and γ -valerolactone. Specific examples of the chain ester include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, butyl methyl carbonate, propyl methyl carbonate, butyl ethyl carbonate, propyl ethyl carbonate, butyl propyl carbonate, alkyl propionate, dialkyl malonate, and alkyl acetate. Specific examples of the cyclic ether include tetrahydrofuran, alkyltetrahydrofuran, dialkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1, 3-dioxolane, alkyl-1, 3-dioxolane, and 1, 4-dioxolane. Specific examples of the chain ether include 1, 2-dimethoxyethane, 1, 2-diethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.

Referring now to FIG. 6, anode structure 24 has a bottom surface B adjacent substrate 22, a top surface T remote from substrate 22, and side surfaces S extending from top surface T to bottom surface B₁、S₂. Side S₁Intersects the surface of the substrate 22 at an angle α, and has a side S₂α and is approximately equal and between 80 and 100 in a preferred embodiment, for example, α and is approximately equal and 90 + -5 in one embodiment α and is approximately equal and about 90 independent of the angle of intersection, it is generally preferred that each side S22 intersects the surface of the substrate 22₁And S₂Most of the surface area of (2) and the reference planeIn this embodiment, the surface of substrate 22 is substantially vertical; in other words, it is generally preferred that each side S is₁And S₂Lies in a plane that intersects a reference plane (as illustrated, the surface of substrate 22) at an angle of between about 80 ° and 100 °, and more preferably at an angle of 90 ° ± 5 °. It is also generally preferred that the top surface T and the side surfaces S₁And S₂Substantially perpendicular and substantially parallel to the surface of substrate 22. For example, in one presently preferred embodiment, substrate 22 has a substantially planar surface, and anode structure 24 has a top surface T that is substantially parallel to the planar surface of substrate 22, and side surfaces S₁And S₂Substantially perpendicular to the planar surface of substrate 22.

Referring now to fig. 7, the porous layer 31 includes an anode active material having pores 60 and a pore axis 62. In a preferred embodiment, the anode active material comprises porous silicon or a silicon alloy, such as nickel silicide. Although the apertures 60 may vary in size, shape, and symmetry, the aperture axes 62(i) are adjacent the sides S₁Is predominantly perpendicular to the side S in the region of the porous layer 31₁(ii) adjacent to the side S₂Is predominantly perpendicular to the side S in the region of the porous layer 31₂And (iii) is predominantly perpendicular to the top surface T in the region of the porous layer 31 adjacent to the top surface T (see fig. 6). Thus, at the side S₁And S₂The hole axis 62(i) is adjacent to the side S when substantially perpendicular to the surface of the substrate 22₁And S₂Is predominantly parallel to the surface of substrate 22, and (iii) is predominantly perpendicular to the surface of substrate 22 in the region of porous layer 31 adjacent top surface T (see fig. 6). Further, in one embodiment, the pore size, wall size, pore depth, and pore morphology in the region of the porous layer 31 adjacent the top surface T may be different from the region adjacent the surface S₁And S₂The wall size, pore depth and pore morphology in the region of the porous layer 31.

Fig. 8-9 show schematic representations of one embodiment of a method for making the anode stems and cathode supports of the present invention. Referring now to fig. 8, a silicon wafer 50 is attached to the substrate 22 by conventional means. The base 22 may be the same size as the substrate, or larger or smaller in size. For example, the wafer 50 and substrate 22 may be anodically bonded together, bonded using an adhesive, or a polymer layer may be formed in situ. As previously described, the substrate 50 may include a layer of glass, ceramic, polymer, or other material that provides sufficient rigidity during subsequent processing steps. Alternatively, silicon-on-insulator wafers may be used as starting materials.

Referring now to fig. 9, a photoresist is patterned (pattern) onto a wafer 50 to provide the desired backbone structure, and chemically etched to provide the anode backbone and cathode support. The resulting anode trunk 32 has a length L_ABHeight H_ABAnd width W_ABWherein the height H_ABIs measured in a direction perpendicular to the surface of the substrate 22, and has a length L_ABAnd width W_ABMeasured in a direction parallel to the surface of substrate 22. Typically, W_ABWill be at least 5 microns, H_ABWill be at least 50 microns, and L_ABWill be at least 1000 microns. The resulting cathode support 36 has a length L_CBHeight H_CBAnd width W_CBWherein the height H_CBIs measured in a direction perpendicular to the surface of the substrate 22, and a length L_CBAnd width W_CB。

After the anode stems and cathode support are formed in the illustrated embodiment, the cathode support is masked and the anode stems 32 are processed to form a microstructured silicon layer on the anode stems 32 having a void volume fraction of at least 0.1, as previously described. The masking of the cathode may then be removed and an anode current collector formed on the anode active material layer and a cathode current collector formed on the cathode support. After selective deposition of the cathode material on the cathode current collector, a separator may be deposited between the cathode material and the anode current collector, the individual current collectors are connected to the cell tabs, and the entire assembly is inserted into a conventional battery case, filled with a conventional lithium battery electrolyte containing a lithium salt and a mixture of organic carbonates (propylene carbonate + ethylene carbonate), and sealed using a vacuum sealer, with the wires extending out of the case to establish electrical connections. In an alternative embodiment, two or more die, each containing one or more anodes and one or more cathodes assembled as described above, are placed in a stack and electrically connected to the cell tabs before the entire assembly is inserted into a conventional battery case or the like to form a cell.

Referring now to fig. 10, one embodiment of a three-dimensional battery 10 of the present invention includes a battery housing 12, a die stack 14, and tabs 16, 18 for electrically connecting the die stack 14 to an external energy source or consumer (not shown). For lithium ion batteries for portable electronic devices such as mobile phones and computers, for example, the battery housing 12 may be a cartridge or other conventional battery housing. The die stack 14 includes several dies, each of which includes a cell having an interdigitated anode and cathode sequence, with the anode electrically connected to the contact 16 and the cathode electrically connected to the contact 18. The number of dies in the vertical stack is not critical and may for example be in the range of 1 to 50, typically 2 to 20 dies in the stack.

Referring now to fig. 11, in one embodiment, an electrochemical stack 610 includes a reference plane 601 and a stem 603 projecting perpendicularly from the reference plane 601. The cathode element of the electrochemical stack 610 includes a cathode current collector layer 620 and a cathode active material layer 618. The anode element of the electrochemical stack 610 includes an anode active material layer 612 and an ion-permeable conductor layer 614, the ion-permeable conductor layer 614 also serving as an anode current collector layer. Preferably, the thickness of the ion-permeable conductor layer 614 at the top of the backbone 603 (i.e., the surface of the backbone away from the reference plane 601) is greater than the thickness of the ion-permeable layer at the side of the backbone 603 (the surface between the top and the reference plane 601); for example, in one embodiment, the thickness of the ion-permeable conductor at the top of the trunk is 110% to 2000% of the thickness of the ion-permeable conductor at the sides. For another example, in one embodiment, the thickness of the top of the trunk is 200% to 1000% of the thickness of the ion-permeable conductor at the sides. In one embodiment, the permeability of the ion-permeable conductor at the top of the trunk is less permeable to, and may even be impermeable to, carrier ions (e.g., lithium ions) than the side ion-permeable conductors. A separator layer 616 is located between the ion-permeable conductor layer 614 and the cathode active material layer 618. The cathode collector layer 620 is electrically connected to a cathode contact (not shown) and the ion-permeable conductor layer 614 is electrically connected to an anode contact (not shown). For ease of illustration, only one anode trunk and only two cathode trunks are shown in fig. 11; however, in practice, the electrochemical stacks will typically comprise an alternating sequence of anode and cathode stems, with the number of each stack depending on the application.

Referring now to fig. 12, in one embodiment, an electrochemical stack 610 includes a reference plane 601 and a stem 603 projecting substantially perpendicularly from the reference plane 601. The cathode element of the electrochemical stack 610 includes a cathode current collector layer 620 and a cathode active material layer 618. Each anode element of electrochemical stack 610 includes a height H (measured from reference plane 601 and in a direction perpendicular to reference plane 601)_AAnd an ion-permeable conductor layer 614 that also serves as an anode current collector layer. A separator layer 616 is located between the ion-permeable conductor layer 614 and the cathode active material layer 618. In this embodiment, an anode active material layer 612 is located on the top and sides of the stems 603 and a cathode active material layer 618 is adjacent the top and sides of the stems 603. As a result, during charging and discharging of an energy storage device comprising the electrochemical stack 610, the carrier ions move simultaneously in two directions relative to the reference plane 601: the carrier ions move in a direction generally parallel to the reference plane 601 (to enter or exit the anode active material 612 on the side of the trunk 603) and move in a direction generally orthogonal to the reference plane 601 (to enter or exit the anode active material 612 at the top surface of the trunk 603). The cathode collector layer 620 is electrically connected to a cathode contact (not shown) and the ion-permeable conductor layer 614 is electrically connected to an anode contact (not shown). For ease of illustration, only three anode stems and only two cathode stems are shown in FIG. 12, and the viewsIs incomplete, with a portion broken away to illustrate that the anodic and cathodic elements to the left of the break shown in the figure are not two anodic and one cathodic elements directly adjacent to the right of the break shown in the figure; however, in practice, the electrochemical stacks typically comprise an alternating sequence of anode stems and cathode stems, wherein the number of each stack depends on the application, as previously described. As illustrated, the electrochemical stack 610 includes a linear distance D separated from each other_LAt least one pair of anode active material layers 612, the straight distance D_LExceeds the maximum height H of a member of the group of anode active material layers comprised by the electrochemical stack 610_A(in other words, there is a linear distance D separating the groups of anode active material layers comprised by the electrochemical stack 610_LAt least one pair of anode active material layers, the straight distance D_LExceeds the height H of the anode active material layer having the largest height among all the anode active material layers in the group_A). Thus, for example, one or more intervening cathode active material layers 618 and anode active material layers 612 comprised by the electrochemical stack 610 are separated from each other by a linear distance D_LMay be spaced apart from each other (see, e.g., fig. 4A, 4B, 4C, 4D, and 4E and associated description).

Referring now to fig. 13, in one embodiment, electrochemical stack 710 includes interdigitated anode active material layer 712 and cathode active material layer 718. The cathode element of the electrochemical stack 710 further comprises a cathode current collector layer 720 and the anode element of the electrochemical stack comprises an ion-permeable conductor layer 714 that can serve as an anode current collector. A separator 716 is located between the ion-permeable conductor layer 714 and the cathode active material layer 718. Support layers 705, 707 provide mechanical support for interdigitated anode active material layer 712. Although not shown in fig. 12, in one embodiment, as illustrated in fig. 2 and shown in connection with fig. 2, the anode active material layer 712 and the cathode active material layer 718 may be supported by a backbone.

The following non-limiting examples are provided to further illustrate the present invention.

Examples of the invention

Example 1

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.A hard mask layer of silicon dioxide is sputter deposited on top of the device silicon layer. The wafer was then spin coated with a 5 μm resist and then patterned with a mask to obtain a honeycomb structure having a honeycomb wall thickness of 100 μm and a gap thickness of 200 μm. The photoresist is then used as a photomask to remove the silicon dioxide by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide and photoresist is used as a mask for silicon removal. DRIE is performed until the silicon in the cell gap that constitutes the device layer is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone.

The top masking oxide layer was removed by soaking the sample in a dilute (5:1) Buffered Oxide Etch (BOE): aqueous solution for 1 minute. The dissolution time is adjusted so that the insulating oxide layer at the bottom of the trench is not completely etched away.

The silicon sample is then inserted into an evaporation chamber, andis deposited on the sample surface. The process causes Au to be deposited on the top of the honeycomb structure, its sidewalls, and the bottom oxide layer. The silicon backing layer is now protected by an adhesive tape mask. The sample was then immersed in a 1:1 volume solution of 30C hydrofluoric acid (49%) and hydrogen peroxide (30%) to form a porous silicon layer. Adjusting by changing etching timeThe pore silicon depth. The approximate rate of formation of porous silicon is 750-1000 nm/min. When a target pore depth of 30 μm was reached, this portion was removed and dried. The resulting porous silicon layer had a void volume fraction of about 0.3.

The samples were then dried, cross sectioned and photographed. As illustrated in fig. 14, the pores of the dried and cross-sectioned sample are predominantly oriented in a direction parallel to the base oxide layer.

Example 2

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.Is sputter deposited on top of the device layer, followed byA hard mask layer of silicon dioxide. The wafer was then spin coated with 5 μm resist and then patterned with a mask to obtain a combshaped structure having two staggered cells isolated from each other as shown in fig. 3. The two staggered cells also have a land pad (plating pad) on each side, which can be isolated and used as a contact pad for handling and for the final cell. The photoresist is then used as a photomask to remove the silicon dioxide and palladium by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide, photoresist and Pd is used as a mask for silicon removal. DRIE is performed until the silicon constituting the device layer in the mask gap is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone. At this point, the two cells have been electrically isolated by DRIE.

The top masking oxide layer was removed by soaking the sample in a dilute (5:1) Buffered Oxide Etch (BOE) solution for 1 minute. The dissolution time is adjusted so that the insulating oxide layer at the bottom of the trench is not completely etched away.

One of the isolated pairs of honeycomb structures is electrically connected by a palladium conductor and immersed in an electrophoretic resist bath. A commercially available electrophoretic resist (Shipley eage) was used and the honeycomb was electrophoretically deposited at 50V for 120 seconds to form a resist coating. The die is baked at 120C to harden the resist. The resist serves as a protective layer during the subsequent metal deposition step.

The silicon sample is then inserted into an evaporation chamber, andis deposited on the sample surface. The Au deposition process causes Au to be deposited on the top of the honeycomb, its sidewalls, and the bottom oxide layer. However, there is a photoresist on one of the honeycombs, which brings the Au in contact with the silicon on only one of the two honeycomb structures. The silicon backing layer is also protected at this time by an adhesive tape mask. The sample was then immersed in a 1:1 volume solution of 30C hydrofluoric acid (49%) and hydrogen peroxide (30%) to form a porous silicon layer. The porous silicon depth was adjusted by changing the etching time. The approximate rate of formation of porous silicon is 750-1000 nm/min. When a target pore depth of 30 μm was reached, this portion was removed and dried. The resulting porous silicon layer had a void volume fraction of about 0.3.

Porous silicon is formed only on such a honeycomb group (comb-set): the honeycomb set did not have an electrophoretic resist patterned thereon. The porous silicon pack can then be used as an anode in a lithium ion battery. The electrophoretic resist was then stripped in acetone for 15 minutes.

Example 3

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.Is sputter deposited on top of the device layer, followed byA hard mask layer of silicon dioxide. The wafer was then spin coated with a 5 μm resist and then patterned with a mask to obtain a honeycomb structure having two staggered honeycombs spaced apart from each other as shown in fig. 3. The two staggered honeycombs also have a land pad on each side that can be isolated and used as a contact pad for processing and for the final cell. The photoresist is then used as a photomask to remove the silicon dioxide and palladium by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide, photoresist and Pd is used as a mask for silicon removal. DRIE is performed until the silicon constituting the device layer in the mask gap is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone. At this point, the two cells have been electrically isolated by DRIE.

The top masking oxide layer was removed by soaking the sample in a dilute (5:1) Buffered Oxide Etch (BOE) solution for 1 minute. The dissolution time is adjusted so that the insulating oxide layer at the bottom of the trench is not completely etched away.

One of the isolated pairs of honeycomb structures is electrically connected by a palladium conductor and immersed in an electrophoretic resist bath. A commercially available electrophoretic resist (Shipley eage) was used and the honeycomb was electrophoretically deposited at 50V for 120 seconds to form a resist coating. The die is baked at 120C to harden the resist.

The silicon sample is then inserted into an evaporation chamber, andis deposited on the sample surface. The Au deposition process causes Au to be deposited on the honeycomb, its sidewalls, and the bottom oxide layer. However, there is a photoresist on one of the honeycombs, which brings the Au in contact with the silicon on only one of the two honeycomb structures. The silicon backing layer is now protected by an adhesive tape mask. The sample was then immersed in acetone for 15 minutes to remove the electrophoretic resist along with the evaporated Au on top of the electrophoretic resist. This isolates the Au nanoclusters into one of two isolated honeycombs.

Silicon nanowires are then grown on top of one of the honeycomb structures by a CVD method. The sample was inserted into the CVD chamber and heated to 550C. Silane gas was introduced into the chamber and the reactor pressure was maintained at 10 torr. Silicon nanowires are grown on a surface on which Au has been deposited. The deposition rate was 4 μm/hr; and deposition was carried out up to a target nanowire thickness of 20 μm. Since Au is in contact with only one of the silicon wavesets (wavesets), the lines start to grow from this waveset to the outside in a direction parallel to the bottom oxide layer. The resulting silicon nanowire layer had a void volume fraction of about 0.5.

Example 4

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.Is sputter deposited on top of the device layer, followed byA hard mask layer of silicon dioxide. The wafer was then spin coated with a 5 μm resist and then patterned with a mask to obtain a honeycomb structure having two staggered honeycombs spaced apart from each other as shown in fig. 3. The two staggered honeycombs also have a land pad on each side that can be isolated and used as a contact pad for processing and for the final cell. Then using light inductionThe resist acts as a photomask to remove the silicon dioxide and palladium by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide, photoresist and Pd is used as a mask for silicon removal. DRIE is performed until the silicon constituting the device layer in the mask gap is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone. At this point, the two cells have been electrically isolated by DRIE.

A second photoresist is applied over most of the wafer and exposed with a second mask to expose small area openings over each honeycomb pattern. This is then used to remove the silicon dioxide and expose the Pd layer by ion milling.

The honeycomb structure to be used as anode is immersed in HF/H in DMSO contained₂O (2M/2.5M) and an anodic potential is applied against the Pt counter electrode. The silicon honeycomb to be anodized to form porous silicon is connected by Pd in the open vias. The current density was maintained at 3mA/cm²And anodizing was performed for 60 minutes to produce a pore depth of-20 μm. The resulting porous silicon layer had a void volume fraction of about 0.4. This process limits the porous silicon formation to only one of the two honeycomb structures.

Example 5

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.Is sputter deposited on top of the device layer, followed byA hard mask layer of silicon dioxide. The wafer was then spin coated with a 5 μm resist and then patterned with a mask to obtain a honeycombA honeycomb structure having two staggered cells isolated from each other. The two staggered honeycombs also have a land pad on each side that can be isolated and used as a contact pad for processing and for the final cell. The photoresist is then used as a photomask to remove the silicon dioxide and palladium by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide, photoresist and Pd is used as a mask for silicon removal. DRIE is performed until the silicon constituting the device layer in the mask gap is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone. At this point, the two cells have been electrically isolated by DRIE.

At this point, the sample was thermally oxidized to form 0.25 μm SiO on top of all exposed silicon surfaces₂And (3) a layer. The SiO₂Is deposited to serve as a mask for the electrochemical etching of silicon. Subsequently, the substrate is etched using a sputter deposition technique,is deposited on top of the oxide layer. The thickness of the Au layer is optimized to obtain Au in the form of islands rather than a complete film. The Au in island form is then used as a masking layer for etching the thermal oxide layer underneath it.

A second photoresist is applied over most of the wafer and exposed with a second mask to expose the land pad area on each honeycomb pattern. This is then used to remove Au and SiO by wet chemical etching₂And (3) a layer. Au was removed using commercial KI/I2 solution and SiO was removed using a buffered oxide etch solution₂Layer to expose the Pd top layer for subsequent electrical contact.

The sample was then dipped in acetone to strip the photoresist, which was then dipped in a 1:25 BOE: aqueous solution. BOE solution in Au particlesEtching SiO in the lower honeycomb side wall₂Layer and transfer the pattern of Au into the oxide. The etch stops after 90 seconds, which is sufficient to etch the oxide and expose the Si without undercutting the oxide layer under the Au (undercut). After rinsing and drying, the samples were ready for electrochemical dissolution.

The contact pads that were exposed in the previous step are used to make electrical connections for the sample during the silicon anodic etching process. Using a Pt counter electrode, this was connected as the working electrode and was electrochemically driven to dissolve silicon from the exposed areas of the connected honeycomb structure. The sample was soaked in a solution containing 1 part by volume of ethanol, one part of 49% HF and 10 parts by volume of water; and at 15mA/cm²Is driven as an anode. The exposed silicon was dissolved, leaving a microstructured silicon layer that replicated the Au nanocluster distribution including fibers and voids and having a void volume fraction of about 0.5.

Example 6

Silicon-on-insulator (SOI) wafers having a layer thickness of 100 μm/1 μm/675 μm (device layer/insulating layer/backing layer) were used as samples.Is sputter deposited on top of the device layer, followed byA hard mask layer of silicon dioxide.

The wafer was then spin coated with 5 μm resist and patterned with a mask to obtain a honeycomb structure having two staggered honeycombs isolated from each other as shown in fig. 3. The design shows a structure resulting in two separate honeycomb structures, each terminating in a land pad adapted to make electrical contact. The patterned photoresist is then used as a photomask to remove the silicon dioxide and palladium by ion milling.

Using Deep Reactive Ion Etching (DRIE) in a fluoride plasma, a combination of silicon dioxide, photoresist and Pd is used as a mask for silicon removal. DRIE is performed until the silicon constituting the device layer in the mask gap is completely removed, stopping on the oxide layer. The overetch time used was 10% of the total DRIE time to remove the silicon islands in the trench floor. Any top photoresist is removed by stripping in acetone. At this point, the two cells are electrically isolated by DRIE.

The top masking oxide layer was then removed by soaking the sample in a dilute (5:1) Buffered Oxide Etch (BOE) solution for 1 minute. The dissolution time is adjusted so that the insulating oxide layer at the bottom of the trench is not completely etched away.

One of the isolated pairs of honeycomb structures is electrically connected by a palladium conductor and immersed in an electrophoretic resist bath. A commercially available electrophoretic resist (Shipley eage) was used and the honeycomb was electrophoretically deposited at 50V for 120 seconds to form a resist coating. The die is baked at 120C to harden the resist.

The silicon sample is then inserted into an evaporation chamber, andis deposited on the sample surface. The Au deposition process causes Au to be deposited on the top of the honeycomb structure, on its sidewalls, and on the bottom oxide layer. However, there is a photoresist on one of the honeycombs, which brings the Au in contact with the silicon on only one of the two honeycomb structures. The silicon backing layer is now protected by an adhesive tape mask. The sample was then immersed in acetone for 15 minutes to remove the electrophoretic resist along with the evaporated Au on top of the electrophoretic resist. This isolates the Au nanoclusters into one of two isolated honeycombs.

Silicon nanowires are then grown on top of one of the honeycomb structures by a CVD method. The sample was inserted into the CVD chamber and heated to 550C. Silane gas was introduced into the chamber and the reactor pressure was maintained at 10 torr. Silicon nanowires are grown on a surface on which Au has been deposited. The deposition rate was 4 μm/hr; and deposition was carried out up to a target nanowire thickness of 20 μm. The resulting silicon nanowire layer had a void volume fraction of about 0.5 and was used as an anode for a lithium ion battery.

The honeycomb without the silicon nanowires attached was electrophoretically deposited with a lithium ion battery cathode material. The electrophoretic deposition solution contains a cathode material (LiCoO)₂) 15 wt% carbon black and 150ppm iodine in acetone solution. The solution mixture was stirred overnight to disperse the particles uniformly. Pd contact pads are used as terminals for electrical connections for cathode deposition. A Pt counter electrode was used. The samples were deposited for 3 minutes at 100V to deposit a 40 μm thick cathode structure.

The sample is then sent to a spin coater where a macroporous separator is applied to the cell. In this case, the macroporous separator is a combination of fine glass frit (<2 μm diameter) dispersed in acetone with 2 volume percent PVDF binder. The slurry is applied to the tube core and excess slurry is spun off to fill and planarize the separator layer. The drying process causes the solvent to evaporate and form a macroporous separator layer.

The contact pads are then used to wire bond the Au wires to serve as connection points for the battery. The entire assembly was inserted into a conventional battery case, filled with a conventional lithium battery electrolyte containing a lithium salt and a mixture of organic carbonates (propylene carbonate + ethylene carbonate). The cassette is then sealed using a vacuum sealer, wherein the wires extend outside the cassette to form the electrical connections.

Example 7

The process of example 6 is repeated except that five dies are stacked on top of each other and each wire from each die's connection pad is connected to a tab of each electrode.

The entire assembly was inserted into a conventional battery case, filled with a conventional lithium battery electrolyte containing a lithium salt and a mixture of organic carbonates (propylene carbonate + ethylene carbonate). The cassette is then sealed using a vacuum sealer, wherein the wires extend outside the cassette to form the electrical connections.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

When introducing elements of the present invention or one or more preferred embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes could be made in the above articles, compositions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims (39)

1. An electrochemical stack for use in an energy storage device, the stack comprising a group of cathode structures, separator layers, and anode structures arranged in a stack, the cathode structures having a cathode active material layer, the group of anode structures having a height H of at least 50 microns measured in a direction orthogonal to a reference plane_AEach member of the group of anode structures comprises a microstructured anode active material layer having a front surface, a back surface, a thickness T measured from the front surface to the back surface, and an empty space of at least 0.1An aperture volume fraction, the front and rear surfaces being perpendicular to the reference plane, the thickness T being at least 1 micron and measured in a direction parallel to the reference plane, the stacking direction of the cathode structure, the separator layer and the anode structure being parallel to the reference plane, wherein the direction in which carrier ions move between the cathode active material layer of the cathode structure and the microstructured anode active material layer of the anode structure during a charging or discharging process is parallel to the reference plane, the microstructured anode active material layer comprising a fibrous or porous anode active material oriented such that: (i) the anode active material fibers comprised by the microstructured material layer are attached to the back surface of the microstructured anode active material layer and predominantly have a central axis parallel to the reference plane at the attachment points of the fibers to the back surface of the microstructured anode active material layer, and (ii) the pores of the porous anode active material comprised by the microstructured material layer predominantly have a main axis parallel to the reference plane, wherein the linear distance D between at least two members of the group measured in a direction parallel to the reference plane_LH greater than the group_AIs measured.

2. The electrochemical stack of claim 1 wherein each member of the group of the anode structures comprises aluminum, tin, silicon, or alloys thereof.

3. The electrochemical stack of claim 1 wherein each member of the population of the anode structure comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

4. The electrochemical stack of claim 1 wherein each member of the population of the anode structures comprises silicon or an alloy thereof and has a thickness of 1 to 100 microns.

5. The electrochemical stack of claim 1 wherein, for each member of the group of the anode structures, H_AIs greater than T.

6. The electrochemical stack of claim 1 wherein each member of the population of the anode structure comprises porous silicon or an alloy thereof, having a void volume fraction of at least 0.1 but less than 0.8 and a thickness of 1 to 200 microns.

7. The electrochemical stack of claim 1 wherein each member of the population of the anode structures is supported by a backbone having an electrical conductivity of less than 10 siemens/cm.

8. The electrochemical stack of claim 1 wherein H of the group of the anode structures_AIs less than 5000 microns.

9. The electrochemical stack of claim 1 wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone having an electrical conductivity of less than 10 siemens/cm, and the H of the population of the anode structures_AIs less than 5000 microns.

10. The electrochemical stack of claim 1 wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone having an electrical conductivity of less than 1 siemens/cm, and the H of the population of the anode structures_AIs less than the maximum value of1000 microns.

11. The electrochemical stack of claim 1 wherein the population of the anode structures comprises at least 20 members.

12. The electrochemical stack of claim 1 wherein the anode structure comprises an anode current collector, the cathode structure comprises a cathode current collector, and the anode current collector or the cathode current collector comprises an ion-permeable conductor layer.

13. The electrochemical stack of claim 1, wherein the anode structure comprises an anode current collector layer, and the anode current collector layer is disposed between the anode active material layer and a separator layer.

14. The electrochemical stack of claim 13 wherein each member of the population comprises nanowires of silicon or an alloy thereof or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone, and the H of the population_AIs less than 5000 microns.

15. The electrochemical stack of claim 1 wherein the cathode structure comprises a cathode current collector layer, and the cathode current collector layer is disposed between a cathode active material layer and a separator layer.

16. An energy storage device comprising a carrier ion, the carrier ion being a lithium, sodium or potassium ion, a non-aqueous electrolyte and the electrochemical stack of claim 1.

17. The energy storage device of claim 16, wherein the carrier ions are lithium ions.

18. The energy storage device of claim 16, wherein the group of the anode structures comprises at least 20 members.

19. The energy storage device of claim 16, wherein each member of the population of the anode structures comprises silicon or an alloy thereof and has a thickness of 1 to 100 microns.

20. The energy storage device of claim 16, wherein, for each member of the group of the anode structures, H_AIs greater than T.

21. The energy storage device of claim 16, wherein each member of the population of the anode structure comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

22. The energy storage device of claim 16, wherein each member of the population of the anode structure comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of 1 to 200 microns.

23. The energy storage device of claim 16, wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone, and H of the population of the anode structures_AIs less than 5000 microns.

24. The energy storage device of claim 16, wherein each member of the population of the anode structure comprises nanowires of silicon or an alloy thereof or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is comprised of a backboneA support, said backbone having an electrical conductivity of less than 10 Siemens/cm, and H of said group of said anode structures_AIs less than 1000 microns.

25. The energy storage device of claim 16, wherein the anode structure comprises an anode current collector, the cathode structure comprises a cathode current collector, and the anode current collector or the cathode current collector comprises an ion-permeable conductor layer.

26. The energy storage device of claim 16, wherein the anode structure comprises an anode current collector layer, and the anode current collector layer is disposed between the anode active material layer and a separator layer.

27. The energy storage device of claim 26, wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone, and H of the population of the anode structures_AIs less than 5000 microns.

28. A secondary battery comprising carrier ions which are lithium, sodium or potassium ions, a non-aqueous electrolyte and at least two electrochemical stacks as claimed in claim 1 stacked on each other in a direction orthogonal to the reference plane.

29. The secondary battery according to claim 28, wherein the carrier ions are lithium ions.

30. The secondary battery of claim 28 wherein the group of the anode structures comprises at least 20 members.

31. The secondary battery of claim 28 wherein each member of the population of the anode structure comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

32. The secondary battery of claim 28 wherein each member of the group of the anode structures comprises silicon or an alloy thereof and has a thickness of 1 to 100 microns.

33. The secondary battery of claim 28 wherein, for each member of the group of the anode structures, H_AIs greater than T.

34. The secondary battery of claim 28 wherein each member of the population of the anode structure comprises porous silicon or an alloy thereof, having a void volume fraction of at least 0.1 but less than 0.8 and a thickness of 1 to 200 microns.

35. The secondary battery of claim 28 wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone, and H of the population of the anode structures_AIs less than 5000 microns.

36. The secondary battery of claim 28 wherein each member of the population of the anode structure comprises nanowires or porous silicon or alloys thereof of silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone having an electrical conductivity of less than 10 siemens/cm, and H of the population of the anode structure_AIs less than 1000 microns.

37. The secondary battery of claim 28 wherein the anode structure comprises an anode current collector, the cathode structure comprises a cathode current collector, and the anode current collector or the cathode current collector comprises an ion-permeable conductor layer.

38. The secondary battery according to claim 28, wherein the anode structure comprises an anode current collector layer, and the anode current collector layer is disposed between the anode active material layer and a separator layer.

39. The secondary battery of claim 28 wherein each member of the population of the anode structures comprises nanowires of silicon or alloys thereof or porous silicon or alloys thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of 1 to 200 microns, and is supported by a backbone, and H of the population of the anode structures_AIs less than 5000 microns.