JP7613400B2 - Battery Stack - Google Patents

Description

This disclosure relates to a battery stack.

Patent Document 1 discloses a solid-state battery including a solid-state battery body in which positive electrode layers and negative electrode layers are alternately stacked with a solid electrolyte layer interposed therebetween; end electrodes electrically connected to the positive electrode layers and the negative electrode layers, respectively, and disposed on each of two side surfaces of the solid-state battery body; and a bottom electrode electrically connected to the end electrodes and disposed on the bottom side of the solid-state battery body.

International Publication No. 2021/132504

The inventors have investigated how to suppress an increase in the internal resistance of a battery stack having a specified structure, in which the power generating element contains a component that contains sulfur, such as a sulfide solid electrolyte and/or a sulfur-based active material.

The present disclosure aims to provide a battery stack that can suppress an increase in internal resistance.

The present inventors have found that the above object can be achieved by the following means:
Aspect 1
one or more power generating elements each having a negative electrode layer, a solid electrolyte layer, and a positive electrode layer stacked in this order;
a negative electrode terminal disposed on a side surface of the power generating element and electrically connected to the negative electrode layer, and a positive electrode terminal disposed on a side surface of the power generating element and electrically connected to the positive electrode layer,
The power generating element contains sulfur,
The negative electrode terminal and the positive electrode terminal are sintered bodies or fused bodies of metals having a melting point in the range of 260°C to 300°C.
Battery stack.
Aspect 2
the negative electrode layer has a structure in which a negative electrode current collector layer and a negative electrode active material layer are laminated on each other, and the negative electrode terminal is electrically connected to the negative electrode current collector layer; and the positive electrode layer has a structure in which a positive electrode current collector layer and a positive electrode active material layer are laminated on each other, and the positive electrode terminal is electrically connected to the positive electrode current collector layer.
2. The battery stack of claim 1.
Aspect 3
3. The battery stack of claim 1 or 2, wherein the metal is a Sn alloy.
Aspect 4
The battery stack of aspect 3, wherein the Sn alloy is an alloy of Sn and Au or Ni.
Aspect 5
A battery stack according to any one of Aspects 1 to 4, wherein a power generating element is sealed by an exterior body, the negative electrode terminal, and the positive electrode terminal.
Aspect 6
The battery stack according to any one of aspects 1 to 5, wherein the sulfur is contained in a sulfide solid electrolyte and/or a sulfur-based active material.
Aspect 7
The battery stack according to any one of Aspects 1 to 6, wherein the negative electrode terminal and the positive electrode terminal extend to a portion of at least one end face in the stacking direction of the battery stack.
Aspect 8
The battery stack according to any one of aspects 1 to 7, which is a lithium ion secondary battery.

This disclosure provides a battery stack that can suppress an increase in internal resistance.

FIG. 1 is a schematic diagram of a battery stack 100 according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram of a battery stack 200 according to a second embodiment of the present disclosure.

The following describes in detail the embodiments of the present disclosure. Note that the present disclosure is not limited to the following embodiments, and can be modified in various ways within the scope of the disclosure.

The battery stack of the present disclosure is a battery stack in which one or more power generating elements, each having a negative electrode layer, a solid electrolyte layer, and a positive electrode layer stacked in this order, are stacked, and the battery stack has a negative electrode terminal arranged on the side of the power generating element and electrically connected to the negative electrode layer, and a positive electrode terminal arranged on the side of the power generating element and electrically connected to the positive electrode layer, the power generating element contains sulfur, and the negative electrode terminal and the positive electrode terminal are sintered bodies or fused bodies of metals having melting points in the range of 260°C to 300°C.

The battery stack may be configured as follows: one or more power generating elements each having a negative electrode layer, a solid electrolyte layer, and a positive electrode layer stacked in that order; a negative electrode terminal electrically connected to the negative electrode layer and disposed on a side of the power generating element; and a positive electrode terminal electrically connected to the positive electrode layer and disposed on a side of the power generating element.

A battery stack having such a configuration can be expected to be used by fixing it to a substrate, such as a printed circuit board, with solder or the like.

However, sulfur-containing components that may be used in the power generating element, such as sulfide solid electrolytes and/or sulfur-based active materials, may chemically react with water. Therefore, when the power generating element contains sulfur, the battery stack is required to have sufficient sealing properties.

In order to provide sufficient sealing to the battery stack, it is possible to form the external terminals, i.e., the negative and positive terminals, by sintering or melt bonding.

However, when heated to high temperatures, sulfur can chemically react with other components of the power generating element and with external terminals, etc.

Therefore, if the sintering or melting temperature of the metal used in the external terminals is high, when the external terminals are formed by sintering or melt bonding during the manufacture of the battery stack, the sulfur contained in the power generating element may react chemically with the metal forming the external terminals, and/or the sulfur in the power generating element may react with other components, resulting in a decrease in the internal resistance of the manufactured battery stack.

In this regard, in the battery stack of the present disclosure, the external terminals are sintered or fused metals having a melting point in the range of 260°C to 300°C. Such metals have a melting point of 260°C or higher, which is higher than the general heating temperature in the solder reflow process used to join the battery stack to a printed circuit board or the like. Therefore, melting of the external terminals when joining the battery stack to a printed circuit board or the like can be suppressed. Melting of the external terminals may cause problems such as a decrease in the sealing ability of the battery stack in some cases.

In addition, because such metals have a melting point of 300°C or less, they can be melted at a temperature lower than the reaction temperature of the sulfur that can be used in the power generation element to form the external terminals. This makes it possible to suppress an increase in the internal resistance of the battery stack due to the reaction of the sulfur in the power generation element during the manufacture of the battery stack.

The battery stack of the present disclosure can have a configuration, for example, as shown in Figure 1.

Figure 1 is a schematic diagram of a battery stack 100 according to a first embodiment of the present disclosure. More specifically, Figure 1 is a cross-sectional view of the stacking direction of the battery stack 100 according to the first embodiment of the present disclosure.

As shown in FIG. 1, the battery stack 100 according to the first embodiment of the present disclosure includes a plurality of power generating elements 110, each of which has a negative electrode layer 111, a solid electrolyte layer 112, and a positive electrode layer 113 stacked in this order, and includes a negative electrode terminal 141 electrically connected to the negative electrode layer 111 and disposed on a side of the power generating element 110, and a positive electrode terminal 142 electrically connected to the positive electrode layer 113 and disposed on a side of the power generating element 110. In addition, an exterior body 130 is disposed on both sides of the battery stack 100 in the stacking direction and on a side (not shown) on which no external terminal is disposed, thereby sealing the power generating element 110 with the exterior body 130, the negative electrode terminal 141, and the positive electrode layer 113.

In addition, an insulating electrode end layer 120 is disposed between the negative electrode active material layer and the exterior body 130 and between the solid electrolyte layers of adjacent power generating elements 110, thereby suppressing electrical contact between the negative electrode layer 111 and the exterior body 130, between the negative electrode layer 111 and the positive electrode terminal 142, and/or between the positive electrode layer 113 and the negative electrode terminal 141.

Here, the power generating element 110 contains sulfur, and the negative electrode terminal 141 and the positive electrode terminal 142 are sintered or fused bodies of metals having a melting point in the range of 260°C to 300°C.

Also, as shown in FIG. 2, in the battery stack 200 according to the second embodiment of the present disclosure, the negative electrode layer 211 has a structure in which the negative electrode collector layer 211a and the negative electrode active material layer 211b are stacked on each other, and the negative electrode terminal 241 can be electrically connected to the negative electrode collector layer 211a. Similarly, the positive electrode layer 213 has a structure in which the positive electrode collector layer 213a and the positive electrode active material layer 213b are stacked on each other, and the positive electrode terminal 242 can be electrically connected to the positive electrode collector layer 213a.

The battery stack of the present disclosure may be a lithium-ion secondary battery.

《Power Generation Element》
In the present disclosure, the power generating element is formed by laminating an anode layer, a solid electrolyte layer, and a cathode layer in this order.

The battery stack has a structure in which one or more power generating elements are stacked, particularly a structure in which multiple power generating elements are stacked in a monopolar structure. Here, when the battery stack has only one power generating element, the battery stack has the configuration of a single cell. When the battery stack has a structure in which multiple power generating elements are stacked, the stacking direction of each power generating element in the battery stack is the same as the stacking direction of the negative electrode layer, solid electrolyte layer, and positive electrode layer in the power generating element.

The power generating element contains sulfur. Here, the sulfur can be contained, for example, in a sulfide solid electrolyte and/or a sulfur-based active material. The sulfur can be contained in any of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer.

The sulfide solid electrolyte may be, for example, a sulfide-based amorphous solid electrolyte, a sulfide-based crystalline solid electrolyte, or an argyrodite-type solid electrolyte. More specifically, examples of sulfide solid electrolytes include _Li2S - _{P2S5 -} based ( _Li7P3S11 , _{Li3PS4 , Li8P2S9} , _etc. ), Li2S _{-SiS2 , LiI} - _{Li2S - SiS2} , _{LiI - Li2S} - _P2S5 , LiI- _LiBr - _{Li2S - P2S5 ,} Li2S- _{P2S5 - GeS2} ( _Li13GeP3S16 , _{Li10GeP2S12 , etc.} ), LiI _{- Li2S - P2O5 , LiI} - _Li3PO4 - _P2S5 , Li _7-x PS _6-x Cl _x , and the like; or combinations thereof.

The sulfur-based active material is an active material containing at least S element. The sulfur-based active material may or may not contain Li element. Examples of the sulfur-based active material include elemental sulfur, lithium sulfide (Li ₂ S), and lithium polysulfide (Li ₂ S _x , 2≦x≦8).

<Negative electrode layer>
The negative electrode layer may have a structure in which, for example, a negative electrode current collector layer and a negative electrode active material layer are laminated on each other, and in this case, the negative electrode terminal may be electrically connected to the negative electrode current collector layer. Note that the negative electrode layer may not have a negative electrode current collector layer, and in this case, the negative electrode terminal may be electrically connected to the negative electrode active material layer by directly contacting the negative electrode current collector layer.

(Negative Electrode Active Material Layer)
The negative electrode active material layer contains a negative electrode active material and, optionally, a solid electrolyte. In addition, the negative electrode active material layer may contain additives used in the negative electrode active material layer of a lithium ion battery, such as a conductive assistant or a binder, depending on the intended use or purpose.

The negative electrode active material may be, for example, a material capable of absorbing and releasing metal ions such as lithium ions. Examples of the material capable of absorbing and releasing metal ions such as lithium ions include, but are not limited to, an alloy-based negative electrode active material or a carbon material.

The alloy-based negative electrode active material is not particularly limited, and examples thereof include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of the Si alloy-based negative electrode active material include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. The Si alloy-based negative electrode active material may also include elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, and the like. The Sn alloy-based negative electrode active material may also include tin, tin oxide, tin nitride, and solid solutions thereof. The Sn alloy-based negative electrode active material may also include elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, and the like. Among these, the Si alloy-based negative electrode active material is preferred.

The carbon material is not particularly limited, but examples include hard carbon, soft carbon, graphite, etc.

The solid electrolyte is not particularly limited, and any material that can be used as a solid electrolyte in an all-solid-state battery can be used. More specifically, examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and polymer electrolytes.

Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include _Li2S - _{P2S5 system} ( _{Li7P3S11 , Li3PS4} , _Li8P2S9 , etc.), _Li2S - _SiS2 , _LiI - _{Li2S - SiS2} , _LiI - _Li2S - _P2S5 , _{LiI - LiBr} - _Li2S - _P2S5 , Li2S- _{P2S5 -GeS2 (} Li13GeP3S16, _{Li10GeP2S12 , etc.} ) _{, LiI - Li2S - P2O5 ,} LiI _{- Li3PO4 - P2S5} , Li _7-x PS _6-x Cl _x , and the like; or combinations thereof.

Examples of oxide solid electrolytes include, but _{are not limited to} , _{Li7La3Zr2O12 ,} Li7 _{-xLa3Zr1 - xNbxO12 , Li7-3xLa3Zr2AlxO12, Li3xLa2/3-xTiO3 , Li1 + xAlxTi2 - x} ( _PO4 ) ₃ , Li1 ₊ xAlxGe2 _{-x ( PO4 ) 3} , _{Li3PO4 ,} or _{Li3 + xPO4-xNx ( LiPON )} .

The sulfide solid electrolyte, the oxide solid electrolyte, and the nitride solid electrolyte may be glass, glass ceramics, or a crystalline material. Glass can be obtained by amorphous processing of a raw material composition (e.g., a mixture of _Li2S and _{P2S5 )} . Examples of amorphous processing include mechanical milling. Mechanical milling may be dry mechanical milling or wet mechanical milling, with the latter being preferred. This is because the raw material composition can be prevented from adhering to the wall surface of a container or the like. Glass ceramics can be obtained by heat treating glass. Crystalline materials can be obtained, for example, by performing a solid-phase reaction process on the raw material composition.

Examples of polymer electrolytes include, but are not limited to, polyethylene oxide (PEO) and polypropylene oxide (PPO).

The binder may be, for example, but is not limited to, a material such as polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), butadiene rubber (BR), or styrene butadiene rubber (SBR), or a combination thereof.

As the conductive assistant, known materials can be used, for example, carbon materials and metal particles. As the carbon material, for example, at least one selected from the group consisting of carbon black such as acetylene black and furnace black, vapor grown carbon fiber (VGCF), carbon nanotubes, and carbon nanofibers can be used, and from the viewpoint of electronic conductivity, at least one selected from the group consisting of VGCF, carbon nanotubes, and carbon nanofibers may be used. As the metal particles, for example, particles of nickel, copper, iron, stainless steel, etc. can be used.

(Negative electrode current collector layer)
The material used for the negative electrode current collector layer may be, but is not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, carbon, etc. Among these, the material for the negative electrode current collector layer is preferably copper.

The shape of the negative electrode current collector layer is not particularly limited, and examples include a foil-shaped, plate-shaped, or mesh-shaped electronically conductive material, and a layer-shaped material formed from an electronically conductive material powder and a binder. Of these, a foil-shaped electronically conductive material is preferred.

<Solid electrolyte layer>
The solid electrolyte layer can contain a solid electrolyte and optionally a binder.

The solid electrolyte and binder may be any of those described above in relation to the "negative electrode active material layer."

<Positive electrode layer>
The positive electrode layer may have a structure in which a positive electrode current collector layer and a positive electrode active material layer are laminated on each other, and in this case, the positive electrode terminal may be electrically connected to the positive electrode current collector layer. Note that the positive electrode layer may not have a positive electrode current collector layer, and in this case, the positive electrode terminal may be electrically connected to the positive electrode active material layer by directly contacting the positive electrode current collector layer.

(Positive Electrode Active Material Layer)
The positive electrode active material layer contains a positive electrode active material and, optionally, a solid electrolyte. In addition, the positive electrode active material layer may contain additives used in the positive electrode active material layer of a lithium ion battery, such as a conductive assistant or a binder, depending on the intended use or purpose.

The positive electrode active material may be, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , or a different element-substituted Li-Mn spinel having a composition represented by Li _1+x Mn _2-xy M _y O ₄ (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn), but is not limited to these.

In addition, such a positive electrode active material may be, for example, a sulfur-based active material. Here, the sulfur-based active material is an active material containing at least an S element. The sulfur-based active material may or may not contain an Li element. Examples of the sulfur-based active material include elemental sulfur, lithium sulfide (Li ₂ S), and lithium polysulfide (Li ₂ S _x , 2≦x≦8).

The solid electrolyte, conductive additive, and binder may be any of those described above in relation to the "negative electrode active material layer."

(Positive electrode current collector layer)
The material used for the positive electrode current collector layer may be, but is not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, carbon, etc. Among these, the material for the positive electrode current collector layer is preferably aluminum.

The shape of the positive electrode current collector layer is not particularly limited, and examples thereof include a foil-shaped, plate-shaped, or mesh-shaped electronically conductive material. Examples of the material include a layer-shaped material formed from an electronically conductive material powder and a binder. Among these, a foil-shaped electronically conductive material is preferred.

Negative and positive terminals
The battery stack of the present disclosure has a negative electrode terminal that is electrically connected to the negative electrode layer and is disposed on a side surface of the power generating element, and a positive electrode terminal that is electrically connected to the positive electrode layer and is disposed on a side surface of the power generating element.

The negative and positive terminals are sintered or fused metals with a melting point in the range of 260°C to 300°C.

The metal that can be used for the negative and positive terminals can be any metal or metal alloy that has a melting point in the range of 260°C to 300°C. Examples of such metals include Pb and Sn alloys. Examples of Sn alloys include alloys of Sn with Au or Ni.

The melting point of the metal that can be used for the negative and positive terminals may be 260°C or more, 265°C or more, 270°C or more, or 275°C or more, and may be 300°C or less, 295°C or less, 290°C or less, 285°C or less, or 280°C or less.

The negative and positive terminals can extend to at least a portion of one end face of the battery stack in the stacking direction. When the battery stack has such a configuration, the end faces to which the negative and positive terminals extend can be fixed to the printed circuit board, for example with solder, to electrically connect the battery stack to the circuit on the printed circuit board.

More specifically, as shown in FIG. 1, the negative electrode terminal 141 and the positive electrode terminal 142 can extend to a portion of the end face of the battery stack 100 in the stacking direction (the upper and lower sides of the battery stack 100 in FIG. 1).

Exterior Body
In the battery stack of the present disclosure, the power generating element is preferably sealed by the exterior body, the negative electrode terminal, and the positive electrode terminal.

Here, the exterior body may be any material capable of sealing the power generating element, such as resin or ceramics.

REFERENCE SIGNS LIST 100 and 200 Battery stack 110 and 210 Power generating element 111 and 211 Negative electrode layer 112 and 212 Solid electrolyte layer 113 and 213 Positive electrode layer 120 and 220 Electrode end layer 130 and 230 Exterior body 141 and 241 Negative electrode terminal 142 and 242 Positive electrode terminal 211a Negative electrode current collector layer 211b Negative electrode active material layer 213a Positive electrode current collector layer 213b Positive electrode active material layer

Claims (7)

one or more power generating elements each having a negative electrode layer, a solid electrolyte layer, and a positive electrode layer stacked in this order;
a negative electrode terminal disposed on a side surface of the power generating element and electrically connected to the negative electrode layer, and a positive electrode terminal disposed on a side surface of the power generating element and electrically connected to the positive electrode layer,
The power generating element contains sulfur,
The negative electrode terminal and the positive electrode terminal are sintered bodies or fused bodies of metals having a melting point in the range of 260°C to 300°C,
the negative electrode layer has a negative electrode active material layer and does not have a negative electrode current collector layer, the negative electrode terminal is in direct contact with the negative electrode active material layer and is thereby electrically connected to the negative electrode layer,
the positive electrode layer has a positive electrode active material layer and does not have a positive electrode current collector layer, and the positive electrode terminal is in direct contact with the positive electrode active material layer and is thereby electrically connected to the positive electrode layer;
Battery stack. The battery stack of claim 1 , wherein the metal is a Sn alloy. The battery stack according to claim 2 , wherein the Sn alloy is an alloy of Sn and Au or Ni. The battery stack according to any one of claims 1 to 3 , wherein a power generating element is sealed by an exterior body, the negative electrode terminal, and the positive electrode terminal. The battery stack according to any one of claims 1 to 4 , wherein the sulfur is contained in a sulfide solid electrolyte and/or a sulfur-based active material. 6. The battery stack according to claim 1 , wherein the negative electrode terminal and the positive electrode terminal extend to a portion of at least one end face of the battery stack in the stacking direction. The battery stack according to any one of claims 1 to 6 , which is a lithium ion secondary battery.

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