KR20250093037A - Lithium metal electrode for a lithium secondary battery and a method of making the same - Google Patents

Abstract

The present invention relates to a lithium metal electrode and a method for manufacturing the same. The lithium metal electrode of the present invention comprises a current collector comprising Fe and Ni and a metal layer positioned on at least one surface of the current collector and comprising a lithium alloy.

Description

{LITHIUM METAL ELECTRODE FOR A LITHIUM SECONDARY BATTERY AND A METHOD OF MAKING THE SAME}

The present invention relates to a lithium secondary battery, and more specifically, to a lithium metal electrode for a lithium secondary battery and a method for manufacturing the same.

In order to reduce the cost and increase the energy density of secondary batteries, it is essential to use lithium metal electrodes as the negative electrodes of lithium secondary batteries. Specifically, all-solid-state batteries are attracting attention as next-generation batteries for high energy density, such as those for electric vehicles (EVs).

All-solid-state batteries have many advantages, including superior stability because they do not use liquid electrolytes, high-voltage operation, improved energy density of the battery pack due to reduced cooling and safety-related auxiliary materials, and operation over a wide temperature range. In order to achieve practical high energy density in such all-solid-state batteries, thick and low-capacity graphite-based negative electrode materials must be replaced with thin and high-capacity lithium, and considering cost-effectiveness and energy density, a thin-film lithium metal electrode with a thickness of 10 to 20 ㎛ is practically required.

In general, for lithium metal electrodes, Cu is used in large quantities as a current collector. However, there is a problem that it is difficult to apply the current collector because Cu is corroded in a sulfide-based all-solid-state battery. To solve this problem, interest in using Ni or STS as a current collector is increasing. However, although Ni has better corrosion resistance than Cu, it still has a corrosion problem. Although STS has excellent corrosion resistance, it is not economical in terms of process to make it less than 20 ㎛ thick for application to a current collector, and there is a problem that surface treatment is difficult.

Therefore, research is needed on lithium metal electrodes that can replace existing current collectors and have stable and excellent life characteristics, including corrosion-resistant current collectors.

According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery provides a lithium metal battery having excellent corrosion resistance and battery life characteristics.

According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

According to one embodiment of the present invention, a lithium metal electrode may include a current collector including Fe and Ni and a metal layer positioned on at least one surface of the current collector and including a lithium alloy. In one embodiment, a protective layer positioned on the metal layer may be included.

In one embodiment, the current collector including Fe and Ni may include 10 to 90 wt % of Fe and the remainder Ni, based on 100 wt % of the alloy in the current collector. In one embodiment, the current collector including Fe and Ni may include 55 to 70 wt % of Fe and the remainder Ni, based on 100 wt % of the alloy in the current collector.

In one embodiment, the metal layer can include at least one lithium-philic metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). In one embodiment, the metal layer including the lithium-philic metal can have a thickness of 20 to 300 nm.

In one embodiment, the standard deviation of the thickness of the metal layer including the lithium-friendly metal may be 90 nm or less. In one embodiment, the molar ratio of the lithium-friendly metal in the metal layer including the lithium alloy may be higher toward the current collector.

According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode may include a step of preparing a current collector including Fe and Ni, and a step of forming a coating layer on at least one surface of the current collector using a coating composition including a lithium-philic component. In one embodiment, after the step of forming the coating layer, the method may include a step of forming a protective layer on a surface of the coating layer, a step of positioning the current collector on which the coating layer and the protective layer are formed in a plating solution, and then positioning a lithium source at a predetermined distance from the protective layer, and a step of applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which the lithium-philic component included in the coating layer and lithium precipitated from the lithium source are alloyed.

In one embodiment, the step of preparing a current collector including Fe and Ni may include 10 to 90 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector. In one embodiment, the current collector including Fe and Ni may include 55 to 70 wt% of Fe and the remainder Ni, based on 100 wt% of the alloy in the current collector.

In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-philic component can control the thickness of the coating layer to be in the range of 20 to 300 nm. In one embodiment, the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-philic component can control the thickness standard deviation of the coating layer to be in the range of 10 to 90 nm.

In one embodiment, in the step of forming a coating layer on at least one surface of a current collector using a coating composition including the lithium-friendly component, the coating layer may include at least one lithium-friendly metal among gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).

According to one embodiment of the present invention, a lithium metal electrode for a lithium secondary battery includes an alloy layer containing Fe and Ni within a current collector, thereby providing a lithium metal battery having excellent corrosion resistance and life characteristics.

According to another embodiment of the present invention, a method for manufacturing a lithium metal electrode for a lithium secondary battery provides a method for manufacturing a lithium metal electrode for a lithium secondary battery having the advantages described above.

FIGS. 1A and 1B illustrate a lithium metal electrode manufactured according to one embodiment.
Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.
FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of an alloy material coating layer plated on a current collector according to one embodiment of the present invention.
Figure 4 shows a cross-sectional structure when lithium is deposited between a protective layer and a current collector by an electrodeposition process according to one embodiment.
Figures 5a and 5b show the appearance when lithium is deposited according to examples and comparative examples of the present invention.
FIG. 6 is a photograph showing an evaluation of the corrosion resistance of a lithium metal battery according to an embodiment and a comparative example of the present invention.
Figure 7 shows the cell life evaluation of an all-solid-state battery using examples and comparative examples of the present invention.

The terms first, second, and third, etc. are used to describe, but are not limited to, various parts, components, regions, layers, and/or sections. These terms are only used to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms include the plural forms as well, unless the context clearly dictates otherwise. The word "comprising," as used herein, specifies particular features, regions, integers, steps, operations, elements, and/or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components.

When a part is referred to as being "on" or "on" another part, it may be directly on or above the other part, or there may be other parts intervening. In contrast, when a part is referred to as being "directly on" another part, there are no other parts intervening.

Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined.

FIGS. 1A and 1B illustrate a lithium metal electrode (100) manufactured according to one embodiment.

Referring to FIG. 1a, a lithium metal electrode (100) according to one embodiment includes a current collector (11) and a metal layer (12) positioned on at least one surface of the current collector (11), and also includes a protective layer (30) positioned on the other surface of the metal layer (12) facing the current collector (11).

The current collector (11) may be a member for electrical connection within a lithium secondary battery. The current collector (11) may have a form of a foil, but is not limited thereto, and may have, for example, a form of a mesh, a foam, a rod, a wire, or a sheet made by weaving a wire (fiber).

The current collector (11) may use a material that is electrically conductive and has limited reaction with lithium. Specifically, the material of the current collector (11) may use any one or a combination of, for example, copper, nickel, titanium, stainless steel, iron, gold, platinum, silver, tantalum, ruthenium, and alloys thereof, carbon, conductive polymers, and composite fibers having a conductive layer coated on a non-conductive polymer.

In one embodiment, the thickness of the current collector (11) may be 1 μm to 50 μm. If the thickness of the current collector (11) is excessively thick, there is a problem that the battery weight increases and the energy density of the battery decreases. If the thickness of the current collector (11) is excessively thin, there is a risk of overheating damage during high current operation and damage due to tension during the battery manufacturing process.

In one embodiment, the current collector (11) may include Fe and Ni. Specifically, the current collector (11) may include an alloy including Fe and Ni. Since the current collector (11) includes Fe and Ni, it has the advantage of having a low coefficient of thermal expansion, which is advantageous for battery application, excellent corrosion resistance, and at the same time, easy surface treatment, which is advantageous for application to an all-solid-state battery.

In one embodiment, the current collector (11) may include 10 to 90 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector (11). The Fe and Ni in the current collector (11) satisfy the above-described range and have the following advantages.

Fe: 10 to 90 wt%

Fe is included in an appropriate amount in the current collector (11), thereby increasing corrosion resistance and providing economic benefits. Fe may be included in an amount of 10 to 90 wt% based on 100 wt% of the current collector (11). Specifically, Fe may be included in an amount of 55 to 70 wt%, and more specifically, 60 to 70 wt%, based on 100 wt% of the current collector (11).

If the content of the above Fe is outside the upper or lower limit of the above-mentioned range, there is a problem that the reactivity with the electrolyte increases compared to the value within the appropriate range.

Ni: 10 to 90 wt%

Ni is included in the current collector (11), thereby having the advantage of increased corrosion resistance. Ni may include the remainder, specifically, 90 to 10 wt%, excluding 10 to 90 wt% of Fe, based on 100 wt% of the current collector (11). For example, when Fe is 10 wt%, Ni may be 90 wt%.

If the content of the above Ni is excessive, there is a problem that cell instability increases and reproducibility is poor. If the content of the above Ni is insufficient, there is a problem that the corrosion resistance effect of Ni is insufficient.

The metal layer (12) is positioned on the current collector (11) and may include a lithium alloy layer (21) including a lithium alloy and a lithium metal layer (41) positioned on the lithium alloy layer (21). The lithium alloy layer (21) may be a layer including a lithium alloy in which a lithium-friendly component included in the metal layer (12) and lithium precipitated from the lithium source (40) are alloyed by applying a current between the current collector (11) and the lithium source (40 in FIG. 2).

In order to form a metal layer (12), if a high current is applied to perform the electrodeposition process in order to increase the lithium deposition rate, there is a problem that the performance of the lithium secondary battery deteriorates. However, in the case of forming a metal layer (12) with a structure including a lithium alloy layer (21) including a lithium component as in the present embodiment, even if a high current is applied to perform the electrodeposition process, it is possible to prevent excessive generation of fine lithium particles or destruction of the protective layer (30) in the electrodeposition process.

Specifically, since the metal layer (12) of one embodiment includes a lithium alloy layer (21) containing a lithium component, when a high current is applied in the electrodeposition process to form a lithium metal layer (41) on the lithium alloy layer (21), the initially formed lithium particles can be induced to grow well, thereby forming particles having a coarse structure, and at the same time, the lithium metal layer (41), and consequently the metal layer (12), can have a uniform surface.

Therefore, the performance of a secondary battery using the lithium metal electrode according to the present embodiment, specifically, the charge/discharge characteristics, can be significantly improved. In addition, since a high-performance lithium metal electrode for a secondary battery can be manufactured even when a high current is applied to perform the electrodeposition process at a high speed, the productivity of the lithium metal electrode for a secondary battery can also be significantly improved.

In this embodiment, the lithium alloy layer (21) includes a lithium-friendly metal. When the lithium alloy layer (21) includes a lithium-friendly metal, the diffusion of lithium ions becomes smooth due to the decrease in the surface energy of lithium ions on the surface of the lithium-friendly metal. Accordingly, there is an advantage in that the lithium ion conductivity is improved and the electrodeposition of the lithium metal layer is performed uniformly. The metal layer (12) plays a role in helping lithium to be deposited more effectively under the protective layer (30) during the charging process of the battery.

In one embodiment, a lithium-friendly metal layer may be further included between the lithium alloy layer (21) and the current collector (11). Specifically, some of the lithium-friendly metal may form an alloy with lithium within the lithium alloy layer (21), and some may remain on the surface of the current collector. Specifically, in one embodiment, the molar ratio of the lithium-friendly metal may increase toward the current collector. This means that some of the lithium-friendly metal applied on the current collector forms an alloy with lithium during the electrolytic plating process to form a lithium alloy layer (21), and some of the remaining lithium-friendly metal remains on the current collector.

The lithium alloy layer (21) may be an alloy composed of lithium and a lithium-friendly metal, wherein the lithium-friendly metal may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn). Specifically, the lithium-friendly metal may include tin (Sn). Specifically, the lithium-friendly metal includes tin, so that it is advantageously applied to a current collector (11) including Fe and Ni, and lithium dendrite growth can be prevented, thereby implementing a stable and long-life lithium metal battery.

In one embodiment, the thickness of the metal layer including the lithium-friendly metal may be 20 to 300 nm. Specifically, the metal layer including the lithium-friendly metal may be a lithium alloy layer (21). The thickness of the metal layer including the lithium-friendly metal may be 25 to 200 nm, specifically, 50 to 150 nm.

If the thickness exceeds the upper limit of the above-mentioned range, there is a problem of reduced thickness uniformity. If the thickness exceeds the lower limit of the above-mentioned range, there is a problem of disadvantage in cell driving characteristics.

In one embodiment, the thickness standard deviation of the metal layer including the lithium-friendly metal may be 90 nm or less. Specifically, the thickness standard deviation of the metal layer including the lithium-friendly metal, for example, the lithium alloy layer (21), may be 90 nm or less, specifically, 10 to 90 nm, specifically, 12.5 to 87.1 nm, more specifically, 45 to 65 nm, and more specifically, 50 to 55 nm.

The thickness standard deviation of the metal layer including the lithium-friendly metal refers to a value measured by extracting multiple random parts of the sample and using the Cross-section polishing (CP) and Focused ion beam (FIB) methods, and when the thickness standard deviation satisfies the above-mentioned range, the uniformity satisfies a certain range condition, so that lithium dendrite growth can be effectively prevented, which has an advantage. When the thickness standard deviation of the metal layer including the lithium-friendly metal exceeds the upper limit of the above-mentioned range, there is a problem that the uniformity of the metal layer greatly differs, which is disadvantageous for lithium dendrite growth inhibition. In one embodiment, the thickness of the metal layer (12) may be in the range of 1 ㎛ to 100 ㎛, more specifically, 5 ㎛ to 30 ㎛. When the thickness of the metal layer (12) is excessively thick, when the lithium metal electrode of the present embodiment is applied to a secondary battery, there is a problem that the weight and volume of the battery increase, thereby lowering the energy density. In addition, since the time and cost of the electrodeposition process increase in proportion to the thickness when forming the metal layer (12), it is preferable that the thickness of the metal layer (12) be 100 ㎛ or less.

When the thickness of the metal layer (12) is excessively thin, there is a problem that the charge/discharge life of the battery is reduced when the lithium metal electrode of the present embodiment is applied to a secondary battery. Specifically, during charging/discharging of the battery, lithium ions move between the negative electrode and the positive electrode, and a sufficient amount of lithium-friendly metal must be distributed on the negative electrode so that the lithium-friendly metal maintains the force of attracting lithium ions even when the battery is repeatedly charged/discharged, thereby enabling stable behavior. Therefore, if the lithium-friendly metal is present in an excessive amount, the charge/discharge life of the battery is reduced. The protective layer (30) is located on the metal layer (12) and may include amorphous carbon. When only lithium metal is used as the negative electrode in an all-solid-state battery, high resistance is generated by the reaction between the all-solid-state electrolyte and lithium, and lithium dendrites are continuously generated or high-resistance lithium byproducts are generated due to local unevenness in the current density during the charge/discharge process, resulting in a failure or a decrease in battery capacity due to a short circuit or overvoltage during charge/discharge.

According to one embodiment, a lithium metal electrode can further improve structural safety as well as output characteristics and life characteristics of the lithium metal electrode by including a protective layer including amorphous carbon.

Specifically, the lithium metal electrode of the present embodiment includes a protective layer (30) containing amorphous carbon, thereby not only improving ion conductivity, but also improving the strength of the protective layer (30), and preventing short circuits between electrodes by physically blocking dendrites when they grow on the lithium electrode, thereby improving the charge/discharge life.

The above amorphous carbon may be at least one selected from the group consisting of Acetylene Black, Super P Black, Carbon Black, Denka Black, Activated Carbon, Graphite, Hard Carbon, and Soft Carbon, but is not limited thereto.

In one embodiment, the protective layer (30) may include a binder. The binder may be an aqueous binder, and the aqueous binder may be, but is not limited to, a rubber-based binder selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), and acrylic rubber, and at least one selected from the group consisting of polymer resins such as hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride.

Here, the binder may be added in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight, based on the weight of the slurry formed by mixing the amorphous carbon and water. When the content of the binder satisfies the above-mentioned range, the particles constituting the protective layer are efficiently bound to form a protective layer with excellent performance without causing a decrease in battery energy density due to an increase in weight and volume, thereby further improving the life characteristics of the secondary battery.

If the content of the binder is excessively less than the above-mentioned range, there is a problem that the bonding force between particles is reduced when forming a protective layer, and if the content of the binder is excessively more than the above-mentioned range, not only does it cause a reduction in energy density, but also the resistance of the protective layer significantly increases, which causes a problem of interfering with lithium ion conduction.

In one embodiment, the thickness of the protective layer (30) may be 0.01 ㎛ to 50 ㎛. Specifically, the thickness of the protective layer (30) may be in the range of 1 ㎛ to 20 ㎛. When the thickness of the protective layer satisfies the above-described range, lithium dendrites are prevented from being formed on the surface of the protective layer, and lithium ions can be well penetrated and conducted inside the protective layer, thereby allowing lithium to be precipitated from the lower surface of the protective layer.

If the thickness of the protective layer is excessively thin, there is a problem that it cannot function as a protective layer. If the thickness of the protective layer is excessively thick, the resistance of the protective layer is excessively large, which may cause an increase in overvoltage during the operation of the secondary battery, and there is a problem that the battery energy density is reduced due to an increase in weight and volume. However, the thickness of the protective layer can be variably adjusted according to the design of the secondary battery structure.

In one embodiment, the lithium metal electrode may further include a film layer disposed in at least a portion of the interior of the protective layer (30), between the metal layer (12) and the protective layer (30), and on the protective layer (30). Specifically, the film layer may be disposed in at least a portion of the interior of the protective layer (30), may be disposed between the metal layer (12) and the protective layer (30), may be disposed simultaneously inside the protective layer (30) and between the metal layer (12) and the protective layer (30), and may be disposed on the protective layer (30).

The above film layer is formed during the manufacturing process of the metal layer (12) by a reaction between the lithium metal of the electrodeposited lithium source (40) and the plating solution, and the thickness, composition, characteristics, etc. of the film can be controlled by adjusting the composition of the plating solution used and the conditions of the electrodeposition process.

In one embodiment, the film layer may include at least a portion of LiF. The LiF may be formed by including a solvent having a high dielectric constant among at least one of a plurality of solvents used in the electrodeposition process. Specifically, by increasing the salt decomposition dissociation degree of the solvent of the plating solution for electrodeposition, the salt decomposition reaction may be suppressed and the solvent decomposition reaction may be promoted during electrodeposition, thereby allowing a sufficient LiF film to be formed inside and/or on the surface of the protective layer. By including the film layer including at least a portion of LiF, the lifespan may be improved and dendrite growth may be prevented due to the high ion conductivity during battery operation.

The thickness of the film layer may be 2 nm to 2 ㎛. Specifically, the thickness of the film layer may be specifically in the range of 10 nm to 500 nm. If the thickness of the film layer is excessively thick, the lithium ion conductivity decreases and the interfacial resistance increases, which causes a problem in that the charge/discharge characteristics deteriorate when applied to a battery. If the thickness of the film layer is excessively thin, the film layer may be easily lost during the process of applying the lithium metal electrode according to the embodiment to a battery. Therefore, the film layer may have a thin thickness within the range satisfying the thickness range and may be uniformly and densely formed on the entire surface of the metal layer (12) or the protective layer (30).

Referring to FIG. 1b, in one embodiment, a lithium metal electrode (100) includes a current collector (11) and a metal layer (12) positioned on at least one surface of the current collector (11) and configured by mixing lithium and a lithium alloy. Here, the lithium alloy may be formed by alloying a lithium-affinity component included in the metal layer (12) formed on the current collector (11) with lithium precipitated from the lithium source (40) by applying a current between the current collector (11) and a lithium source (40).

The above metal layer (12) may include a lithium-friendly metal. Here, the lithium-friendly metal may include tin, and a detailed description thereof may be provided with reference to FIG. 1a.

In one embodiment, the metal layer (12) is in a form that includes a lithium-friendly metal. When the metal layer (12) including a lithium-friendly metal is formed in this way, the free energy for nucleation of lithium particles can be lowered at the initial stage of nucleation in the electrodeposition process, so that a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

In one embodiment, The thickness of the metal layer (12) including the annotation may be 20 to 300 nm. A detailed description thereof is the same as that described in Fig. 1a, within a range that does not contradict it.

In one embodiment, the metal layer (12) includes a protective layer (30) positioned on the surface of the metal layer (12), and may further include a film layer on the inside and/or surface of the protective layer (30). For a detailed description of the protective layer (30) and the film layer, refer to the description above with reference to FIG. 1A.

Figure 2 is a schematic diagram of a method for manufacturing a lithium metal electrode of the present invention.

Referring to FIG. 2, a method for manufacturing a lithium metal electrode according to one embodiment includes a step of preparing a current collector (11), a step of forming a coating layer (20) on at least one surface of the current collector (11) using a coating composition including a lithium-philic component, a step of forming a protective layer (30) on the surface of the coating layer (20) using a slurry including amorphous carbon, a step of positioning the current collector (11) on which the coating layer (20) and the protective layer (30) are formed in a plating solution (50), and then positioning a lithium source (40) at a predetermined distance from the protective layer (30), and a step of applying a current between the current collector (11) and the lithium source (40) to form a metal layer including a lithium alloy in which the lithium-philic component included in the coating layer and lithium precipitated from the lithium source (40) are alloyed.

The step of preparing a current collector (11) may be a step of preparing a current collector including Fe and Ni. The step of preparing the current collector including Fe and Ni may include 10 to 90 wt% of Fe and the remainder of Ni based on 100 wt% of the alloy in the current collector. Specifically, the current collector including Fe and Ni may include 55 to 70 wt% of Fe and the remainder of Ni based on 100 wt% of the alloy in the current collector. The detailed description of the Fe and Ni is the same as that described above with reference to FIGS. 1A and 1B without contradiction.

When the contents of Fe and Ni in the current collector (11) satisfy the above-mentioned range, not only is the corrosion resistance of the current collector increased, but most of the reproducibility problems can be solved, which is an advantage. If the content of Fe is outside the upper or lower limit of the above-mentioned range, there is a problem that the reactivity between the current collector and the electrolyte increases. If the content of Ni is excessive, there is a problem that cell instability increases and reproducibility is poor. If the content of Ni is insufficient, there is a problem that the corrosion resistance effect of Ni is insufficient.

The step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition including a lithium-friendly component may coat a lithium-friendly metal, which is an alloy material, on at least one surface of the current collector. As described above with reference to FIGS. 1A and 1B , the lithium-friendly metal may include at least one of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn), and specifically, may include tin (Sn).

The coating layer (20) may be formed by, after the process described below, forming a lithium alloy layer (21) by forming an alloy between lithium and a lithium-friendly metal, as described above in FIGS. 1A and 1B. In one embodiment, the coating layer (20) may be specifically disposed between a current collector (11) and a protective layer (30), and then forming a lithium alloy layer (21) through electrolytic plating.

In one embodiment, the step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition including a lithium-friendly component can control the thickness of the coating layer to a range of 20 to 300 nm. Specifically, the thickness of the coating layer can be 25 to 200 nm, specifically, 50 to 150 nm.

In one embodiment, the step of forming a coating layer (20) on at least one surface of a current collector (11) using a coating composition including a lithium-friendly component can control the thickness standard deviation of the coating layer to 90 nm or less. Specifically, the thickness standard deviation of the coating layer can be 12.5 to 87.1 nm, more specifically, 45 to 65 nm, and even more specifically, 50 to 55 nm.

In one embodiment, the step of forming the coating layer (20) may be performed using at least one of electrolytic and electroless plating, sputtering, electron beam, and thermal vapor deposition. For example, the step of forming the coating layer may be coated using an electrolytic plating method.

A protective layer (30) can be formed on the surface of the coating layer (20) using a slurry containing amorphous carbon. The protective layer (30) can be applied by mixing the amorphous carbon and a binder in water using at least one of a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush application method. The protective layer (30) can further include a binder.

Meanwhile, in the step of forming the protective layer (30), the thickness of the protective layer formed on the surface of the alloy material coating layer may be in the range of 0.01 ㎛ to 50 ㎛, more specifically, 1 ㎛ to 20 ㎛.

If the thickness exceeds the upper limit of the above-mentioned range, there is a problem of top-surface deposition in which lithium is deposited on the protective layer. If the thickness exceeds the lower limit of the above-mentioned range, there is a problem that is detrimental to the cell operating characteristics.

After the step of forming the protective layer (30), a step of positioning a current collector in which the coating layer (20) and the protective layer (30) are sequentially formed in the plating solution (50), a step of positioning a lithium supply source (40) at a predetermined distance from the current collector (11), and a step of applying current between the current collector (11) and the lithium supply source (40) to form a metal layer (12) are performed.

Specifically, after positioning a current collector (11) having a coating layer (20) and a protective layer (30) formed within a plating solution, a lithium supply source (40) is positioned at a predetermined distance from the protective layer (30). The lithium supply source (40) may be, for example, lithium metal, a lithium alloy, a foil in which the lithium metal or lithium alloy is pressed onto a current collector, a plating solution in which a lithium salt is dissolved, etc.

The plating solution (50) can be prepared by dissolving a lithium salt in a plurality of solvents. Specifically, the lithium salt can be LiCl, LiBr, LiI, LiCO ₃ , LiNO ₃ , LiFSI, LiTFSI, LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiN(SO ₂ CF ₃ ) ₂ , LiBOB, or a combination thereof. The concentration of the lithium salt can be 1.0 to 3.0 M based on the total electrolyte.

Specifically, in the present embodiment, the plating solution (50) is characterized by including a nitrogen-based compound as at least one of the lithium salt and a plurality of solvents. The nitrogen-based compound may include, for example, at least one selected from the group consisting of lithium nitrate, lithium bis fluorosulfonyl imide, lithium bis trifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin.

Among the above nitrogen compounds, at least one of lithium nitrate, lithium bis fluorosulfonyl imide, and lithium bis trifluoromethane sulfonimide can be used as a lithium salt.

Among the above nitrogen compounds, at least one of caprolactam (e-caprolactam), methyl caprolactam (N-methyl-e-caprolactam), triethylamine, and tributylamin can be used as a non-aqueous solvent.

The above plating solution (30) may be manufactured using only the nitrogen-based compound, but may include a general non-aqueous solvent as an auxiliary solvent in consideration of the viscosity of the plating solution (30), etc.

The auxiliary solvent may include, for example, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and 1,3,5-trioxane.

In one embodiment, the auxiliary solvent may be included in an amount of 5 to 70 wt%, preferably 10 to 60 wt%, relative to 100 wt% of the total plating solution (50), but is not limited thereto. However, when the auxiliary solvent is included within the above range, the viscosity of the plating solution (50) may be appropriate, thereby shortening the time required for the formation process of the lithium metal layer (12), but is not limited thereto.

In one embodiment, the plating solution (50) may further include a fluorine-based compound. When the plating solution (50) further includes the fluorine-based compound, there is an advantage in that the properties of the film layer formed on the lithium metal layer (12) can be improved.

The above fluorine compounds include, for example, lithium difluoro phosphate, lithium hexafluorophosphate, lithium difluoro bisoxalato phosphate, lithium tetrafluoro oxalato phosphate, lithium difluoro oxalate borate, lithium difluoro oxalato borate, lithium tetrafluoro oxalato borate, fluoroethylene carbonate, difluoroethylene carbonate, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. It may include at least one selected from the group consisting of 2,2,3,3-Tetrafluoropropyl ether.

The above fluorine compound may be included in an amount of 0.1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, relative to 100 wt% of the total plating solution (50). When the fluorine compound is included within the above range, the interaction between the nitrogen compound and the fluorine compound in the plating solution (50) is favorable, so that there is an excellent advantage in improving the properties of the film layer formed on the lithium metal layer (12). In addition, there is an advantage in that the electrochemical properties are excellent because excessive generation of LiF, etc. due to direct reaction between the fluorine compound and lithium is suppressed.

Next, after positioning an insulating film between the current collector (11) and the lithium supply source (40), the current collector (11), the lithium supply source (40), and the insulating film can be laminated and restrained in both directions using a restraining device. The restraining device can use a method generally used in the art, such as a manual clamping method, a uniaxial pressurizing method such as hydraulic pressure or pneumatic pressure, as a non-limiting example.

In the step of applying the current to form a lithium metal layer (12) on at least one surface of the current collector (11), the current density of the current applied may be in the range of 0.1 mA/cm ² to 100 mA/cm ² , more specifically, in the range of 0.2 mA/cm ² to 50 mA/cm ² , in the range of 5 mA/cm ² to 30 mA/cm ² , or in the range of 7 mA/cm ² to 25 mA/cm ² .

In one embodiment, the time for applying the current can be in the range of 0.05 hours to 50 hours, more specifically in the range of 0.25 hours to 25 hours.

In one embodiment, the step of applying the current to form a lithium metal layer (12) on at least one surface of the current collector (11) may be performed at least once at different current densities. The step of applying the current may be performed in multiple stages. Specifically, the step of applying the current in multiple stages may be performed by increasing the current density from a low current density to a high current density step by step over a predetermined time period. For example, the step of applying the current may be performed by stepwise increasing the current in the order of 0.1 to 0.3 mA/cm ² , 0.3 to 0.7 mA/cm ² , and 0.8 to 1.5 mA/cm ² .

In one embodiment, the step of applying the current to form a lithium metal layer (12) on at least one surface of the current collector (11) may include a step of electrodepositing at a maximum current density in a range of 6 to 12 mA/cm ² . Specifically, the maximum current density may be performed in a range of 8 to 12 mA/cm ² . The maximum current density refers to a limit of the current density at which lithium electrodeposited in the electrodeposition process can precipitate lithium between the protective layer (30) and the current collector (11).

The step of electrodeposition at the above maximum current density may be a final step performed after the step of depositing in multiple stages, for example, for lithium deposition between the current collector (11) and the protective layer (30). Since the above maximum current density satisfies the above-mentioned range, lithium is appropriately deposited between the current collector (11) and the protective layer (30), so that there is an advantage of excellent life characteristics of the battery and bonding strength between the current collector (11) and the protective layer (30).

If the maximum current density exceeds the upper limit of the above-mentioned range, there is a problem in that the targeted stabilized electrode structure cannot be secured because lithium is deposited on the surface of the protective layer (30). If the maximum current density exceeds the lower limit of the above-mentioned range, there is a problem in that the productivity decreases because the time for lithium to be deposited increases.

In one embodiment, in the step of forming a lithium metal layer on at least one surface of the current collector (11) by applying the current, the step of electrodepositing the deposited lithium may include a step of depositing the lithium in a thickness range of 3 to 15 μm. Specifically, the deposited lithium may be deposited in a thickness range of 5 to 12 μm. The thickness of the deposited lithium may refer to the vertical height of lithium arranged between the current collector (11) and the protective layer (30).

If the thickness of the precipitated lithium exceeds the upper limit of the thickness mentioned above, there is a problem that not only the energy density of the battery decreases, but also the process time and the amount of metal raw materials used in forming the metal layer increase. If the thickness of the precipitated lithium exceeds the lower limit of the thickness mentioned above, there is a problem that the initial coulombic efficiency decreases due to the initial irreversibility and the charge/discharge performance deteriorates due to the insufficient excess lithium.

In one embodiment, in the step of forming a lithium metal layer (12) on at least one surface of the current collector (11) by applying the current, the thickness of the metal layer (12) including a lithium alloy can be controlled to 1 to 100 ㎛. For a detailed description of the thickness of the metal layer (12), reference can be made to the contents of the aforementioned Fig. 1.

In this way, in this embodiment, it is possible to manufacture a lithium metal electrode (100) in which a metal layer including a lithium metal layer (12) having a coarse particle structure is formed by preventing excessive generation of fine lithium particles even under high current conditions and inducing the initially formed lithium particles to grow well. In addition, the metal layer manufactured in this way also has excellent surface uniformity.

According to another embodiment of the present invention, a lithium secondary battery includes a cathode, an anode, and an electrolyte positioned between the cathode and the anode. Here, the anode may be a lithium metal electrode according to the present invention.

In one embodiment, a lithium secondary battery may include an electrode assembly including a cathode including a cathode active material, an anode being a lithium metal electrode of the present invention, and a separator disposed between the cathode and the anode. This electrode assembly may be wound or folded and accommodated in a battery case.

Thereafter, an electrolyte may be injected into the battery case and sealed to complete the secondary battery. At this time, the battery case may have a shape such as a cylindrical shape, a square shape, a pouch shape, or a coin shape.

The positive electrode may include a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer may include a Li compound including, for example, at least one metal selected from Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce, and at least one non-metallic element selected from the group consisting of O, F, S, P, and combinations thereof.

In one embodiment, a conductive material may be further added to the positive electrode active material layer. The conductive material may be, for example, but is not limited to, carbon black and fine graphite particles, fine carbon such as acetylene black, nano metal particle paste, etc.

The above positive electrode current collector serves to support the positive electrode active material layer. As the positive electrode current collector, for example, an aluminum foil, a nickel foil, or a combination thereof may be used, but is not limited thereto.

As the electrolyte to be filled in the above lithium secondary battery, a non-aqueous electrolyte or a solid electrolyte may be used. Specifically, the electrolyte may be a solid electrolyte. The non-aqueous electrolyte may include, for example, a lithium salt such as lithium hexafluorophosphate or lithium perchlorate, and a solvent such as ethylene carbonate, propylene carbonate or butylene carbonate. In addition, the solid electrolyte may use, for example, a gel polymer electrolyte in which an electrolyte is impregnated in a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N.

The above separator can be any membrane that is commonly used in lithium secondary batteries to separate the positive and negative electrodes and provide a passage for lithium ions to move. Specifically, the separator can be one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. The separator can be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and can be in the form of a non-woven fabric or a woven fabric. Meanwhile, when a solid electrolyte is used as the electrolyte, the solid electrolyte can also serve as the separator.

Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims described below.

<Experimental example>

Manufacturing of cathodes for lithium secondary batteries

<Example 1>

<Manufacturing the entire house>

An Fe-Ni current collector (11) was manufactured by a rolling or electrolytic method. At this time, the Fe-Ni current collector (11) was manufactured by controlling Fe: 90 wt% and Ni: 10 wt% based on 100 wt% of the alloy of Fe and Ni.

<Coating layer formation>

Thereafter, a coating layer (20) was formed on both sides of the manufactured collector by an electroplating method. At this time, tin (Sn) was used as the coating layer, and the plating thickness was controlled to about 100 nm.

FIG. 3 is a scanning electron microscope (SEM) photograph showing the structure and thickness of a coating layer (20) plated on a collector (11) according to one embodiment of the present invention.

Referring to FIG. 3, it can be confirmed that the coating layer (20) plated on the current collector (11) of the present invention has a thickness of about 100 nm and a standard deviation of the thickness of 48.5 nm.

<Formation of protective layer>

Afterwards, a protective layer (30) of about 5 ㎛ was formed on the upper surface of the coating layer (20) by slurry coating using a comma coater. Specifically, the protective layer (30) was formed by mixing acetylene black, which is an amorphous carbon, and a binder. At this time, the binder was prepared by adding 3.0 wt% of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), respectively.

<Lithium deposition process>

Thereafter, lithium was removed from the lithium source (40) using an electrodeposition process to form a lithium alloy or pure lithium metal between the protective layer (30) and the current collector (11), and lithium was deposited between the protective layer (30) and the current collector (11). The plating solution (50) used in this type of electrodeposition was prepared by mixing 1,2-dimethoxyethane (DME) as a first solvent and sulfolane (SL) as a second solvent in a molar ratio of 90:10 in a composite solvent, adding lithium bis(fluorosulfonyl)imide and lithium nitrate, which are nitrogen compounds, in amounts of 40 wt% and 5 wt%, respectively, based on 100 wt% of the plating solution, and adding fluoroethylene carbonate, which is a fluorine compound, in an amount of 5 wt% based on 100 wt% of the plating solution. As a lithium source (40), a lithium metal plate having a purity of 99.9% or higher and a thickness of 500 ㎛ was pressed onto a copper current collector (Cu plate) and used.

After electrically insulating the lithium source (40) and the current collector (11) in the plating solution (50), lithium was deposited between the current collector (11) and the protective layer (30) by applying current using a power supply device with the lithium source (40) and the current collector (11) as (+) and (-) electrodes, respectively.

The current density of the electrodeposition process was increased stepwise in the order of 0.2 mA/cm ² , 0.5 mA/cm ² , and 1 mA/cm ² , and deposition was performed for 5 minutes each, after which the maximum current density was set to 10 mA/cm ² . The deposition time at the maximum current density was calculated as the time required for a final accumulated lithium thickness of 10 ㎛ to be deposited, and was variably set according to the size of the maximum current density.

Figure 4 shows a cross-sectional structure when lithium is deposited between a protective layer (30) and a current collector (11) by an electrodeposition process according to one embodiment.

Referring to FIG. 4, it can be confirmed that lithium is deposited between the protective layer (30) and the current collector (11) by the aforementioned electrodeposition process. The maximum current density means the limit of the current density at which lithium deposited in the electrodeposition process can deposit lithium between the protective layer (30) and the current collector (11), and at a current density higher than the maximum current density value, lithium is deposited on the surface of the protective layer (30), so the target structure cannot be confirmed.

<Comparative Example 1>

A lithium metal electrode was manufactured in the same manner as in Example 1, except that in the step of forming the entire electrode, no Fe was included and only 100 wt% of Ni was included.

<Comparative Example 2>

A lithium metal electrode was manufactured in the same manner as in Example 1, except that it contained no Ni at all in the step of forming the entire electrode, contained only 100 wt% of Fe, and had a maximum electrodepositable current of 4 mA/cm ² .

All-solid-state battery manufacturing

By applying the negative electrode manufactured according to the above-described examples and comparative examples, an all-solid-state battery was manufactured, and the charge-discharge life was evaluated. In order to evaluate the all-solid-state battery cell, a pressurized dedicated evaluation cell from TerraLeader, which can maintain an inert atmosphere, was used. For the manufacture of the all-solid-state battery cell, a sulfide-based argyrodite (Li ₆ P ₅ Cl) solid electrolyte was used, and the electrolyte was in the form of a pellet and had a thickness of about 0.7 mm. In order to secure a dense electrolyte, it was pressurized at a pressure of 370 MPa.

On one side of the electrolyte, lithium having a thickness of 0.5 mm was attached as a reference electrode, and on the opposite side, the negative electrode manufactured by the examples and comparative examples was attached. The reference electrode and the evaluation electrode were pressurized at a pressure of 50 MPa.

On one side of the electrolyte, lithium having a thickness of 0.5 mm was attached as a reference electrode, and on the opposite side, a negative electrode manufactured by the examples and comparative examples was attached.

<Evaluation Example 1>: Control of Fe-Ni content in the entire collector

Table 1 below shows the maximum electrodeposition current and the number of charge/discharge cycles when the content ratio of Fe and Ni in the collector was changed. The standard deviation of the coating layer thickness, the maximum electrodeposition current, and the number of charge/discharge cycles were measured by the following methods.

Standard deviation of coating layer thickness (nm) : Multiple random sections of the sample were extracted and measured using the cross-section polishing (CP) and focused ion beam (FIB) methods.

Maximum current density (mA/cm2 ⁾ : The maximum current density is the limit of the current density at which lithium deposited according to the above process can precipitate lithium between the protective layer and the current collector, and the maximum current density was measured.

Number of Charge/Discharge Performance Times (cycles) : The reference electrode and evaluation electrode were attached to the solid electrolyte at a pressure of 50 MPa, and were pressurized at 16 MPa in a dedicated evaluation cell during the charge/discharge evaluation. The charge/discharge evaluation was performed by defining one cycle as charging for 0.5 hour at a constant current of 2 mA/cm ² and discharging for 0.5 hour at a constant current of 2 mA/cm ² . The charge/discharge life was defined as the end of the life when a short circuit occurred between the reference electrode and the evaluation electrode during the charge/discharge process or when the voltage between the two electrodes exceeded 2 V.

division Total alloy content Coating layer Maximum
Electrodeposition
electric current
[mA/cm ² ] Charge and discharge
Performance
number
[episode] Fe
[wt%] Ni
[wt%] Sn
thickness
[nm] Sn
Thickness standard deviation
[nm] Example 1 90 10 100 48.5 10 637 Comparative Example 1 0 100 100 61.9 12 122 Comparative Example 2 100 0 100 41.3 4 336

Looking at Table 1 above, it was confirmed that Example 1, which includes both Fe and Ni as alloy components in the current collector, had a high number of charge/discharge performance cycles. In contrast, Comparative Examples 1 and 2, which include only Fe or Ni as alloy components in the current collector, had low number of charge/discharge performance cycles.

<Evaluation Example 2> - Fe:Ni content control

<Example 2>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the weight % of Fe:Ni was changed to 64 wt %:36 wt % in the step of forming the entire collector, and the maximum electrodepositable current was 12 mA/cm ² .

<Example 3>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the weight % of Fe:Ni was changed to 10 wt %:90 wt % in the step of forming the entire electrode, and the maximum electrodepositable current was 12 mA/cm ² .

Table 2 below shows the maximum electrodeposition current and the number of charge/discharge cycles when the content ratio of Fe and Ni in the collector was changed. The standard deviation of the Sn layer thickness, the maximum electrodeposition current, and the number of charge/discharge cycles were measured by the following methods.

division Total alloy content Coating layer Maximum
Electrodeposition
electric current
[mA/cm ² ] Charge and discharge
Performance
number
[episode] Fe
[wt%] Ni
[wt%] Sn
thickness
[nm] Sn
Thickness standard deviation
[nm] Example 1 90 10 100 48.5 10 637 Example 2 64 36 100 52.1 12 712 Example 3 10 90 100 59.4 12 705

Looking at Table 2 above, it was confirmed that the number of charge/discharge performance cycles was excellent when both Fe and Ni were included in the collector, as in Examples 1 to 3. At this time, when Examples 1 and 3 were compared with Example 2, it was confirmed that the number of charge/discharge performance cycles of Example 2 was more excellent.

<Evaluation Example 3> - Coating Layer Thickness Control

<Example 4>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the coating layer was controlled to 25 nm in the step of forming the coating layer.

<Example 5>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 200 nm and the maximum deposition current was controlled to 8 mA/cm ² in the step of forming the coating layer.

<Comparative Example 3>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 500 nm and the maximum deposition current was controlled to 6 mA/cm ² in the step of forming the coating layer.

<Comparative Example 4>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 10 nm and the maximum deposition current was controlled to 6 mA/cm ² in the step of forming the coating layer.

<Comparative Example 5>

A lithium metal electrode and an all-solid-state battery were manufactured in the same manner as in Example 2, except that the thickness of the Sn layer was controlled to 0 nm in the step of forming the coating layer.

Figures 5a and 5b show the appearance when lithium is deposited according to examples and comparative examples of the present invention.

FIG. 5a and FIG. 5b illustrate the appearance of the electrodeposition of Example 2 and Comparative Example 4 when electrodeposition was performed at 12 mA/cm ² , respectively. Specifically, they illustrate the appearance when lithium was deposited between the current collector and the protective layer when electrodeposition was performed at the maximum current density, and when electrodeposition was performed at a current density exceeding the maximum current density. When electrodeposition was performed below the maximum possible current density, the deposited lithium was deposited under the black protective layer, so a black protective layer was observed in appearance, and when electrodeposition was performed at a current density exceeding this, lithium was deposited on the upper surface of the protective layer, and it was confirmed that gray lithium was deposited on the upper surface of the protective layer.

Table 3 below shows the maximum deposition current and the number of charge/discharge cycles when the thickness of the coating layer on the collector was changed. The standard deviation of the coating layer thickness, the maximum deposition current, and the number of charge/discharge cycles were measured by the following methods.

division Total alloy content Coating layer Maximum
Electrodeposition
electric current
[mA/cm ² ] Charge and discharge
Performance
number
[episode] Fe
[wt%] Ni
[wt%] Sn
thickness
[nm] Sn layer
Thickness standard deviation
[nm] Example 2 64 36 100 52.1 12 712 Example 4 64 36 25 59.4 12 694 Example 5 64 36 200 14.7 8 682 Comparative Example 3 64 36 500 87.1 6 319 Comparative Example 4 64 36 10 61.9 4 401 Comparative Example 5 64 36 0 0 - -

Looking at Table 2 above, it was confirmed that when the Sn thickness and the Sn thickness standard deviation satisfied the range of the present invention, as in Examples 2, 4, and 5, the charge/discharge performance number of 600 or more was excellent. However, when the Sn thickness was excessively thick, as in Comparative Example 3, it was confirmed that the charge/discharge performance number of times was reduced, and when the Sn thickness was excessively thin, as in Comparative Example 4, it was confirmed that the charge/discharge performance number of times was good. In addition, as in Comparative Example 5, when the coating layer was not formed at all on the current collector, the experiment was conducted by lowering the current density to 0.5 mA/cm ² under the conditions of Example 1 in order to measure the maximum deposition current, but even at that current, the phenomenon of lithium precipitation on the upper surface of the protective layer was observed. In this way, it was confirmed that it was difficult to measure the maximum deposition current density because lithium was deposited on the upper surface of the protective layer even at a sufficiently low current density.

In addition, when cells were manufactured without a coating layer, as in Comparative Example 5, it was confirmed that approximately 80% of the cells did not undergo normal cycle progression and had an internal short circuit problem.

In addition, looking at Table 3 above, no difference was observed in the standard deviation of the coating layer thickness depending on the composition of the current collector, but it was confirmed that the standard deviation tended to increase as the Sn plating thickness increased.

FIG. 6 is a photograph showing an evaluation of the corrosion resistance of a lithium metal battery according to an embodiment and a comparative example of the present invention.

Referring to FIG. 6, the photographs are of the solid electrolyte surface in contact with the current collector after the cell was disassembled to fabricate an all-solid-state cell using a sulfide-based solid electrolyte according to an embodiment and a comparative example of the present invention. In this case, from the left, it shows that current collectors of Cu 100 wt%, Fe 100 wt%, Ni 100 wt%, Fe 10 wt% and Ni 90 wt%, Fe 64 wt% and Ni 36 wt%, and Fe 90 wt% and Ni 10 wt% were used.

Referring to Fig. 6, it can be confirmed that when Cu, Fe, or Ni is used alone in the current collector, corrosion is severe. In contrast, in the case of a current collector containing Fe and Ni simultaneously, it was confirmed that corrosion resistance was excellent compared to when Cu, Fe, or Ni was used alone. In addition, in the current collector containing Fe and Ni simultaneously, it was confirmed that corrosion resistance was the best when Fe was 64% and Ni was 36%.

Figure 7 shows the cell life evaluation of an all-solid-state battery using examples and comparative examples of the present invention.

Figure 7 shows the cell life evaluation of the all-solid-state battery using the lithium electrode of Example 2 of the present invention and Comparative Example 1. Looking at Figure 5, when Fe and Ni as alloy components in the current collector were controlled within the range of the present invention, it was confirmed that the cell life characteristics were excellent at 712 cycles. In contrast, when only Ni was used as the alloy component in the current collector, it was confirmed that the cell life characteristics were inferior at 122 cycles.

The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (15)

A current collector comprising Fe and Ni; and
A lithium metal electrode comprising a metal layer comprising a lithium alloy and positioned on at least one surface of the above-mentioned collector.
In the first paragraph,
A lithium metal electrode comprising a protective layer positioned on the above metal layer.
In the first paragraph,
A current collector including the above Fe and Ni is a lithium metal electrode including 10 to 90 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.
In the first paragraph,
A current collector including the above Fe and Ni is a lithium metal electrode including 55 to 70 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.

In the first paragraph,
A lithium metal electrode wherein the metal layer includes at least one lithium-philic metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).
In the first paragraph,
A lithium metal electrode having a thickness of the metal layer including the lithium-friendly metal of 20 to 300 nm.
In the first paragraph,
A lithium metal electrode having a standard deviation of the thickness of the metal layer including the lithium-friendly metal of 90 nm or less.
In the first paragraph,
A lithium metal electrode having a higher molar ratio of lithium-friendly metal in the metal layer including the lithium alloy as it moves toward the current collector.

A step of preparing a collector containing Fe and Ni; and
A method for manufacturing a lithium metal electrode, comprising the step of forming a coating layer on at least one surface of a current collector using a coating composition containing a lithium-friendly component.
In Article 9,
After the step of forming the above coating layer,
A step of forming a protective layer on the surface of the coating layer;
A step of positioning a current collector having the coating layer and protective layer formed in the plating solution and then positioning a lithium supply source at a predetermined distance from the protective layer; and
A method for manufacturing a lithium metal electrode, comprising the step of applying a current between the current collector and the lithium source to form a metal layer including a lithium alloy in which a lithium-friendly component included in the coating layer and lithium precipitated from the lithium source are alloyed.
In Article 9,
The step of preparing a current collector including the above Fe and Ni is a method for manufacturing a lithium metal electrode including 10 to 90 wt% of Fe and the remainder of Ni based on 100 wt% of the alloy in the current collector.
In Article 11,
A method for producing a lithium metal electrode, wherein the current collector including the above Fe and Ni comprises 55 to 70 wt% of Fe and the remainder of Ni, based on 100 wt% of the alloy in the current collector.
In Article 9,
A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly component controls the thickness of the coating layer to a range of 20 to 300 nm.
In Article 9,
A method for manufacturing a lithium metal electrode, wherein the step of forming a coating layer on at least one surface of a current collector using a coating composition containing the lithium-friendly component controls the thickness standard deviation of the coating layer to 10 to 90 nm.
In Article 9,
A method for manufacturing a lithium metal electrode, wherein the coating layer is formed on at least one surface of a current collector using a coating composition including the lithium-friendly component, and the coating layer includes at least one lithium-friendly metal among gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), and tin (Sn).