JP7801097B2 - All-solid-state battery and method for manufacturing the same - Google Patents

Description

The present invention relates to an all-solid-state battery and a method for manufacturing the same.

All-solid-state batteries are formed by sandwiching a laminated structure of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer between a pair of current collector plates and then heating and compressing it. However, it is known that this process can soften the solid electrolyte layer, which can lead to leakage to the outside.

In response to the above issue, Patent Document 1 discloses an all-solid-state battery that reduces leakage of the solid electrolyte layer by placing a heat-resistant insulating member between a pair of current collector plates to cover the outer periphery of the structure and then forming it by heating and compressing it.

Patent No. 5131283

In the configuration of Patent Document 1, the structure is bonded to an insulating member. Meanwhile, in all-solid-state batteries, repeated charge and discharge causes the anode layer to expand and contract in the thickness direction, and the structure also expands and contracts in the thickness direction to follow suit. However, if the Young's moduli (degree of expansion and contraction) of the solid electrolyte layer and the insulating member differ, there is a risk that the insulating member will apply stress to the solid electrolyte layer, causing damage.

The present invention aims to provide an all-solid-state battery that can reduce damage to the solid electrolyte layer during charging and discharging, and a method for manufacturing the same.

The all-solid-state battery according to the present invention is an all-solid-state battery in which a power generation element unit is disposed between a pair of current collectors, the power generation element unit being formed by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing a lithium alloy or lithium metal, and an elastic body is disposed so as to cover the outer periphery of the power generation element unit. In the all-solid-state battery, the elastic body is formed of a material having a lower Young's modulus than the solid electrolyte layer and is disposed apart from the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, so that a gap is formed between the power generation element unit consisting of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer and the elastic body .

According to the present invention, the elastic body has a lower Young's modulus than the solid electrolyte layer, allowing the elastic body to expand and contract in accordance with the expansion and contraction of the power generation element during charging and discharging. Since the solid electrolyte layer is separated from the elastic body, it is not subjected to stress from the elastic body, reducing damage to the solid electrolyte layer.

1A and 1B are schematic diagrams illustrating a unit cell included in the all-solid-state battery of the first embodiment, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view. 2A and 2B are schematic diagrams for explaining the arrangement of elastic bodies in a cell included in the all-solid-state battery of the first embodiment, where FIG. 2A is a plan view and FIG. 2B is a cross-sectional view. FIG. 3 is a schematic diagram for explaining the arrangement of an elastic adhesive in a unit cell included in the all-solid-state battery of the first embodiment, where FIG. 2(c) is a plan view and FIG. 3(b) is a cross-sectional view. FIG. 4 is a cross-sectional view of a cell included in the all-solid-state battery of the first embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. FIG. 5 is a cross-sectional view of a cell included in an all-solid-state battery of the comparative example, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. FIG. 6 is a schematic diagram showing a case where a crack occurs in the solid electrolyte layer. FIG. 7 is a diagram showing the relationship between the stress applied to the solid electrolyte layer and the cracks that occur in the solid electrolyte layer. FIG. 8 is a cross-sectional view of a cell included in the all-solid-state battery of the second embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. FIG. 9 is a cross-sectional view of an all-solid-state battery according to the third embodiment. FIG. 10 is a cross-sectional view of the all-solid-state battery according to the third embodiment when it is being charged. FIG. 11 is a cross-sectional view of an all-solid-state battery according to the fourth embodiment.

[Outline of the first embodiment]
An all-solid-state battery 100 according to a first embodiment of the present invention will be described.

Figure 1 is a schematic diagram illustrating a cell 9 included in the all-solid-state battery 100 of the first embodiment (a cell 9 manufactured by the manufacturing method for the all-solid-state battery 100 of the first embodiment), where Figure 1(a) is a plan view and Figure 1(b) is a cross-sectional view. Note that Figure 1(a) omits the laminate layer 5 arranged on the upper side of Figure 1(b).

The all-solid-state battery 100 of this embodiment is a secondary battery that can be charged and discharged multiple times. The all-solid-state battery 100 is a so-called stacked-type all-solid-state battery 100 that houses a structure (see FIG. 9, etc.) in which multiple stacked unit cells 9, described below, are sealed with a laminate layer 5, which is the battery exterior material. The stacked structure allows the battery to be compact and have a high capacity.

However, the unit cells 9 housed in the all-solid-state battery 100 to which the present invention is applied do not necessarily have to be multi-layered, and may be single-layered. The unit cells 9 are configured, for example, in the shape of a circular or rectangular sheet before being housed in the battery exterior material. Furthermore, there are no particular limitations on the appearance of the all-solid-state battery 100 of this embodiment, and on the internal electrical connection state (electrode structure).

The appearance of the all-solid-state battery 100 can be circular, elliptical, or rectangular in plan view. Alternatively, it may be cylindrical, containing a single-layer or multiple-layer cell 9 wound around itself. The electrode structure of the all-solid-state battery 100 may be either a non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). In other words, apart from the configuration of the cell 9 described below, the configuration of the all-solid-state battery 100 is not particularly limited, regardless of whether it is publicly known or not.

The unit cell 9 has a configuration in which a power generation element 1, which is made up of a laminated anode layer, solid electrolyte layer 12, and cathode layer 11, is sandwiched between a pair of opposing current collectors (anode current collector 3, cathode current collector 2). In addition, in the unit cell 9, an elastic body 4 is disposed between the pair of current collectors (anode current collector 3, cathode current collector 2) so as to cover the periphery of the power generation element 1 (cathode layer 11, solid electrolyte layer 12, anode layer (deposit layer 13 (Figure 4))).

The negative electrode current collector 3 has a rectangular shape, with a flexible extraction electrode 31 extending from one side of the rectangle. A negative electrode tab 32 (tab), which serves as a rigid terminal, is attached to the tip of the extraction electrode 31.

The negative electrode layer is formed as a deposit layer 13 on the surface of the negative electrode current collector 3 facing the positive electrode current collector 2 when the unit cell 9 is charged, and disappears when the unit cell 9 is discharged. The negative electrode layer (deposit layer 13) is composed of a negative electrode active material containing at least a lithium alloy or lithium metal. As such, the negative electrode layer (deposit layer 13) appears and disappears when the unit cell 9 is charged and discharged, resulting in a change in the dimension in the thickness direction. As an alternative to the negative electrode layer, a solid electrolyte containing lithium metal or a lithium alloy may be disposed as the negative electrode layer on the surface of the negative electrode current collector 3 facing the positive electrode current collector 2.

The positive electrode current collector 2 has a rectangular shape, with a flexible extraction electrode 21 extending from one side of the rectangle. A positive electrode tab 22 (tab), which serves as a rigid terminal, is attached to the tip of the extraction electrode 21.

The positive electrode layer 11 is formed on the surface of the positive electrode current collector 2 facing the negative electrode current collector 3. The positive electrode layer 11 preferably contains a positive electrode active material containing sulfur. The type of sulfur-containing positive electrode active material is not particularly limited, but examples include elemental sulfur (S) as well as particles or thin films of organic sulfur compounds or inorganic sulfur compounds. Any material can be used as long as it utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging.

The solid electrolyte layer 12 contains a solid electrolyte as its main component and is a layer interposed between the above-mentioned negative electrode layer (deposit layer 13) and positive electrode layer 11. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, with sulfide solid electrolytes being preferred.

The laminate layer 5 seals the cell 9 (particularly the power generation element 1). The sealing configuration of the laminate layer 5 is similar to that shown in Figure 8, which will be described later. The laminate layer 5 is used to prevent damage to the power generation element 1 and to protect the solid electrolyte layer 12, anode layer, and cathode layer 11 from moisture in the air. Furthermore, if the solid electrolyte layer 12 is a sulfide, hydrogen sulfide may be generated by reaction with moisture. Therefore, the laminate layer 5 serves to prevent this hydrogen sulfide gas from diffusing outside the cell 9.

Figure 2 is a schematic diagram illustrating the arrangement of the elastic body 4 in the cell 9 included in the all-solid-state battery 100 of the first embodiment, where Figure 2(a) is a plan view and Figure 2(b) is a cross-sectional view.

The elastic body 4 is formed from an insulating resin such as polyimide (e.g., Kapton (registered trademark)) or PTFE (polytetrafluoroethylene). The elastic body 4 is formed in a rectangular frame shape when the power generating element 1 is rectangular in plan view, and in a circular ring shape when the power generating element 1 is circular in plan view. The elastic body 4 is arranged to cover the entire circumference of the power generating element 1, preventing leakage to the outside of the power generating element 1. The elastic body 4 is also arranged so as to be spaced apart from the power generating element 1 in plan view. Note that the elastic body 4, including the materials mentioned above, preferably has a Young's modulus (longitudinal elastic modulus) of 5 GPa or less.

Figure 3 is a schematic diagram illustrating the arrangement of the elastic adhesive 42 in the cell 9 included in the all-solid-state battery 100 of the first embodiment, where Figure 2(3) is a plan view and Figure 3(b) is a cross-sectional view.

The elastic adhesive 42 may be a resin-based adhesive such as an acrylic-modified silicone resin-based elastic adhesive (e.g., Super X (registered trademark) No. 8008, Super XG No. 777, SX720W manufactured by Cemedine Co., Ltd.), a two-component curing epoxy-modified silicone-based elastic adhesive (e.g., EP001K manufactured by Cemedine Co., Ltd.), or a thermosetting resin such as an epoxy resin or silicone resin. As shown in Figure 3, the elastic adhesive 42 is applied to both sides of the elastic body 4.

[Manufacturing process of single cell 9]
The manufacturing process of the unit cell 9 is carried out in the following order: (1) forming the positive electrode layer 11, (2) forming the negative electrode layer, (3) disposing the elastic body 4, (4) heat compression, (5) tab welding, etc.

(1) Formation of Positive Electrode Layer 11 Aluminum foil (thickness: 10 to 20 μm) is prepared as the material for the positive electrode current collector 2 and the positive electrode lead electrode 21. Lithium nickel-cobalt manganese oxide, a _Li2S - _{P2S5 -} based sulfide solid electrolyte, and a binder (PVDF: polyvinylidene fluoride) are prepared as the material for the positive electrode layer 11, and these are placed in a planetary ball mill to be pulverized and mixed to form a mixture. The mixture is coated onto aluminum foil and dried at 80°C using a hot plate until the solvent evaporates. The mixture is then roll-pressed under the desired linear pressure and temperature control, and then cut (punched) to a predetermined size to form the positive electrode layer 11 (positive electrode current collector 2).

(2) Formation of Negative Electrode Layer/Solid Electrolyte Layer 12 Stainless steel foil (or copper foil) is prepared as the material for the negative electrode current collector 3 and the negative electrode lead electrode 31, and this is used as a lithium deposition-type negative electrode layer (negative electrode current collector 3 on which deposition layer 13 is deposited as the negative electrode layer). Then, a slurry composed of a _Li2S - _{P2S5 -} based sulfide solid electrolyte containing lithium metal (or lithium alloy), a binder (SBR: styrene butadiene rubber), and a solvent is prepared on the stainless steel foil. The slurry is then coated and dried on the stainless steel foil, and roll-pressed under the desired linear pressure and temperature control, and cut (punched) to a predetermined size to form a negative electrode layer (negative electrode current collector 3) on which a solid electrolyte layer 12 is disposed.

(3) Arrangement of Elastic Body 4 Kapton (registered trademark) or PTFE is prepared as the material for the elastic body 4, and the material is processed into a frame shape so that the positive electrode layer 11 is disposed inside to form the elastic body 4. A member in which the elastic body 4 is disposed between the positive electrode current collector 2 and the negative electrode current collector 3 is assembled, and an elastic adhesive 42 (e.g., a thermosetting resin) is injected between the positive electrode current collector 2 and the elastic body 4 and between the negative electrode current collector 3 and the elastic body 4 by an underfill method. The elastic adhesive 42 is then cured at a curing temperature of 100 to 150°C for a curing time of 1 to 2 hours.

(4) Heat Compression The above-mentioned members are compressed for 1 to 2 hours to form the unit cell 9. At this time, the adhesive strength of the elastic adhesive 42 is ensured by heating at 100 to 150°C.

(5) Tab welding, etc. In the formed unit cell 9, a positive electrode tab 22 (thickness: 200 to 400 μm) is attached to the tip of the extraction electrode 21, a negative electrode tab 32 (thickness: 200 to 400 μm) is attached to the tip of the extraction electrode 31, and the unit cell 9 is laminated and vacuum sealed with the laminate layer 5, thereby completing the unit cell 9.

[Comparative example cell 9]
Fig. 5 is a cross-sectional view of a cell 9 included in an all-solid-state battery 100 of a comparative example, with the left side of the dashed dotted line before charging and the right side after charging. Fig. 6 is a schematic diagram of a case where a crack 121 occurs in a solid electrolyte layer 12. Fig. 7 is a diagram showing the relationship between stress applied to the solid electrolyte layer 12 and the crack 121 that occurs in the solid electrolyte layer 12.

As mentioned above, it is known that when the cell 9 is charged, lithium precipitates on the negative electrode side. In this case, lithium precipitates on the solid electrolyte layer 12 side and appears as a precipitate layer 13 in the power generation element 1, causing the power generation element 1 to expand in the thickness direction by the amount of the precipitate layer 13 (Figure 5, right).

The comparative example shown in Figure 5 has a structure similar to that of Patent Document 1. In the comparative example, the power generation element 1 and the elastic body 4 are in contact (bonded). In the comparative example, repeated charging and discharging causes the power generation element 1 to expand and contract in the thickness direction, and the elastic body 4 expands and contracts in the thickness direction accordingly. If the Young's modulus (modulus of longitudinal elasticity) of the elastic body 4 differs from that of the solid electrolyte layer 12 of the power generation element 1, the magnitude of expansion and contraction of the power generation element 1 and the elastic body 4 will differ, and the elastic body 4 will apply stress (particularly tensile stress) to the side surface of the solid electrolyte layer 12, which may damage the solid electrolyte layer 12 in the form of, for example, cracks 121.

The inventors used comparative examples to study the stress that occurs during charging and the cracks 121 that may occur in the solid electrolyte layer 12. First, the thickness of the elastic body 4 (and power generating element 1) when the cell 9 is at a 0% charge level was taken as L + ΔL, and the stress was studied when the thickness of the elastic body 4 when the cell 9 is at a 100% charge level was L + ΔL. A cell 9 was prepared in which the elastic body 4 had a thickness of 128.6 μm when the cell 9 was at a 0% charge level. It was confirmed that the thickness of the elastic body 4 increased by 21.5 μm when the cell 9 was charged. The open-circuit voltage of the cell 9 after charging was complete was 4.25 V. In this case, the strain ε applied to the elastic body 4 was 21.5/128.6 = 0.168.

As shown in Figure 6, it is assumed that the thickness of the power generating element 1 is equal to the thickness of the elastic body 4, and the increase ΔL is due to the formation of the precipitate layer 13, ignoring changes in the thickness of the solid electrolyte layer 12 and positive electrode layer 11 of the power generating element 1.

The strain stress σ that the solid electrolyte layer 12 connected (joined) to the elastic body 4 receives from the elastic body 4 is σ = 0.168 × 23 = 3.853 GPa, assuming the Young's modulus of the solid electrolyte (argyorite) is 23 GPa.

On the other hand, if PTFE is used as the elastic body 4, its Young's modulus is 0.5 GPa, so the strain stress (tensile stress) σ that the elastic body 4 receives from the power generation element 1 is σ = 0.168 x 0.5 = 0.084 GPa. Furthermore, if Kapton (registered trademark) is used as the elastic body 4, its Young's modulus is 3.3 GPa, so the strain stress σ that the elastic body 4 receives from the power generation element 1 is σ = 0.168 x 3.3 = 0.554 GPa.

In either case, if the strain stress applied to the solid electrolyte layer 12 is greater than the strain stress applied to the elastic body 4, a crack 121 (cleavage) will occur in the solid electrolyte layer 12.

Solid electrolytes are materials with low toughness, like ceramics and glass, and the fracture surface (cleavage plane) of such materials is flat and shows almost no evidence of plastic deformation. To understand the mechanism by which crack 121 propagates without plastic deformation, it is necessary to consider the local stress increase ahead of the tip of crack 121.

According to continuum elasticity theory, stress concentration occurs near the tip of the sharp crack 121, and it is known that the local stress is σ _Local = σ (1 + (a/(2r)) ^1/2 ), which is expressed by the curve shown in Figure 7. Here, σ is the average tensile stress applied to the entire material, a is the length of the crack 121, and r is the distance from the tip of the crack 121.

As shown in Figure 7, σ _Local increases sharply near the tip of the crack 121. However, because materials such as ceramics and glass have high yield strength and do not easily undergo plastic deformation, the tensile stress near the tip of the crack 121 exceeds the ideal strength and breaks the interatomic bonds within the material. If this severing of interatomic bonds occurs continuously, the material cleaves. Furthermore, with repeated charge and discharge, the crack 121 extends in various directions and reaches the negative electrode layer (precipitation layer 13) and the positive electrode layer 11. If lithium metal (lithium dendrite) penetrates the crack 121, there is a risk of a short circuit between the negative electrode layer and the positive electrode layer 11 via the lithium metal.

Figure 4 is a cross-sectional view of a cell 9 included in the all-solid-state battery 100 of the first embodiment, with the left side showing the state before charging and the right side showing the state after charging.

On the other hand, as shown in FIG. 4 , in the all-solid-state battery 100 (single cell 9) of this embodiment, the elastic body 4 has a lower Young's modulus than the solid electrolyte layer 12. This allows the elastic body 4 (and elastic adhesive 42) to expand and contract in response to the expansion and contraction of the power generation element 1 during charging and discharging. Here, the elastic body 4 (and elastic adhesive 42) expands in the thickness direction by the thickness of the deposition layer 13. Therefore, the power generation element 1, positive electrode current collector 2, and negative electrode current collector 3 do not deform in any direction other than the thickness direction, thereby suppressing deterioration over time due to repeated charging and discharging. Furthermore, when the power generation element 1 expands (and contracts), the solid electrolyte layer 12 is separated from the elastic body 4, so it is not subjected to tensile stress from the elastic body 4. This reduces damage (cracks 121) to the solid electrolyte layer 12. Furthermore, short-circuiting between the positive electrode layer 11 and the negative electrode layer, which may occur when lithium metal precipitates during charging and penetrates into the cracks 121, can also be suppressed.

[Effects of the first embodiment]
According to the all-solid-state battery 100 (single cell 9) of the first embodiment, a power generation element 1 is disposed between a pair of current collectors (a positive electrode current collector 2, a negative electrode current collector 3), and is formed by laminating a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer (deposit layer 13) containing a lithium alloy or lithium metal. In the all-solid-state battery 100, further, an elastic body 4 is disposed so as to cover the outer periphery of the power generation element 1. The elastic body 4 is formed of a material having a lower Young's modulus than the solid electrolyte layer 12, and is disposed at a distance from the power generation element 1.

Furthermore, according to the manufacturing method for the all-solid-state battery 100 (single cell 9) of the first embodiment, a power generation element 1 is disposed between a pair of current collectors (positive electrode current collector 2, negative electrode current collector 3), and is composed of a laminate of a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer (deposit layer 13) containing a lithium alloy or lithium metal. Furthermore, in the manufacturing method for the all-solid-state battery 100, an elastic body 4 is disposed so as to cover the outer periphery of the power generation element 1. The elastic body 4 is formed from a material having a lower Young's modulus than the solid electrolyte layer 12, and is disposed at a distance from the power generation element 1.

With the above configuration and method, the elastic body 4 has a lower Young's modulus than the solid electrolyte layer 12, allowing the elastic body 4 to expand and contract in accordance with the expansion and contraction of the power generation element 1 during charging and discharging. During this process, the solid electrolyte layer 12 is separated from the elastic body 4, so it is not subjected to stress (especially tensile stress) from the elastic body 4, reducing damage (cracks 121) to the solid electrolyte layer 12. Additionally, short circuits between the positive electrode layer 11 and the negative electrode layer caused by lithium metal depositing during charging entering the cracks 121 can also be suppressed.

In the first embodiment, an elastic adhesive 42 is disposed between the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3). This allows the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3) to be stably fixed together. It also alleviates (absorbs) the stress that occurs when the power generating element 1 deforms. By using the elastic adhesive 42 in this way, the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3) can be fixed together while expanding and contracting in accordance with the expansion and contraction of the power generating element 1 during charging and discharging.

In the first embodiment, the elastic adhesive 42 is an acrylic-modified silicone resin-based elastic adhesive or a two-component mixed curing epoxy-modified silicone-based elastic adhesive. This results in a material with a low Young's modulus (longitudinal elastic modulus), allowing it to expand and contract in accordance with the expansion and contraction of the power generation element 1 during charging and discharging. Furthermore, even when the power generation element 1 expands during charging and discharging, it can expand and contract together with the elastic body 4 while fixing the elastic body 4 and the current collector. In addition, because it is a highly versatile adhesive material, it can be applied to the elastic body 4 and current collectors (positive electrode current collector 2, negative electrode current collector 3) at low cost.

In the first embodiment, the Young's modulus of the elastic body 4 is 5 GPa or less. By using an elastic body 4 with a Young's modulus of 5 GPa or less, such as Kapton (registered trademark) or PTFE, the elastic body 4 can expand and contract sufficiently to follow the expansion and contraction of the power generation element 1 during charging and discharging, thereby suppressing the concentration of stress on the power generation element 1 and the occurrence of cracks 121 (cleavage).

In the first embodiment, the solid electrolyte layer 12 is a sulfide-based solid electrolyte material. Because sulfide-based solid electrolytes are materials with high lithium ion conductivity, the internal resistance is low, resulting in an all-solid-state battery 100 (single cell 9) with high efficiency for use in gunfire.

Second Embodiment
Fig. 8 is a cross-sectional view of a cell 9 included in an all-solid-state battery 100 according to the second embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. Fig. 8 is a cross-sectional view of the cell 9 as seen from the same perspective as Fig. 1(b), and the cell 9 of the second embodiment has a similar configuration to that of the first embodiment. Note that the positive electrode current collector 2 and the negative electrode current collector 3 are not shown in Fig. 8.

The cell 9 of the second embodiment has a configuration in which the outer periphery of the positive electrode layer 11 is covered with a solid electrolyte layer 12. This reduces the risk of the positive electrode layer 11 leaking and short-circuiting with the negative electrode layer.

In the second embodiment, when charging is performed, a deposit layer 13 (negative electrode layer) appears on the negative electrode side, and the elastic body 4 (and elastic adhesive 42) expands by the thickness of the deposit layer 13, increasing the thickness of the cell 9.

[Third embodiment]
Fig. 9 is a cross-sectional view of the all-solid-state battery 100 according to the third embodiment. Fig. 10 is a cross-sectional view of the all-solid-state battery 100 according to the third embodiment when it is being charged.

The all-solid-state battery 100 of the third embodiment is produced by preparing a plurality (ten in the figure) of unit cells 9 before sealing with the laminate layer 5 of the second embodiment (or the first embodiment), stacking the adjacent unit cells 9 while alternately flipping them over so that the positive electrode layers 11 (positive electrode current collectors 2) face each other or the negative electrode layers (negative electrode current collectors 3) face each other, sealing the resulting stack of unit cells 9 with the laminate layer 5, and pressing the sealed stack using a restraining jig 6.

In addition, the positive electrode tabs 22 at the ends of the extraction electrodes 21 are connected (welded) in a stacked state. Similarly, the negative electrode tabs 32 at the ends of the extraction electrodes 31 are also connected (welded) in a stacked state. That is, in the third embodiment, all of the cells 9 are connected in parallel. Here, the positive electrode tabs 22 and negative electrode tabs 32 are positioned at the center in the thickness direction.

In the all-solid-state battery 100 of the third embodiment, when charging is performed, the entire laminate expands in the thickness direction, but the positional relationship between the positive electrode tab 22 and the negative electrode tab 32 and the adjacent unit cell 9 in the thickness direction remains almost unchanged before and after charging the all-solid-state battery 100. Therefore, with respect to the unit cell 9, no stress is generated that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, nor that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31.

On the other hand, the relative positions of the two cells 9 adjacent to the restraining jig 6 and the positive electrode tab 22 and negative electrode tab 32 change significantly when the all-solid-state battery 100 is charged. Therefore, for the two cells 9 adjacent to the restraining jig 6, a strong stress is generated that pulls the power generating element 1 toward the positive electrode tab 22 via the extraction electrode 21, and a strong stress is generated that pulls the power generating element 1 toward the negative electrode tab 32 via the extraction electrode 31.

However, in this embodiment, the elastic body 4a of the cell 9 adjacent to the restraining jig 6 is made of a material with a higher Young's modulus than the elastic bodies 4 of the other cells 9. For example, Kapton (registered trademark) (3.3 GPa) is used for the elastic body 4a adjacent to the restraining jig 6, and for example, PTFE (0.5 GPa) is used for the other elastic bodies 4.

The elastic body 4a, which has a high Young's modulus, can reduce displacement not only in response to stress in the thickness direction of the cell 9, but also in response to stress in the planar direction. Therefore, the elastic body 4a can suppress the stress that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and the stress that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31. Therefore, the stress that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and the stress that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31 can be reduced.

As a result, the tensile stress generated during charging and discharging of the power generating element 1 of the cell 9 adjacent to the restraining jig 6 can be reduced, thereby suppressing damage to the power generating element 1, particularly breakage of the outer corners 122.

[Fourth embodiment]
FIG. 11 is a cross-sectional view of the all-solid-state battery 100 according to the fourth embodiment.

The all-solid-state battery 100 of the fourth embodiment is formed by preparing a plurality (ten in the figure) of unit cells 9 before sealing with the laminate layer 5 of the first embodiment (or the second embodiment), stacking the cells 9 alternately upside down so that the positive electrode layers 11 (positive electrode current collectors 2) face each other or the negative electrode layers (negative electrode current collectors 3) face each other in adjacent unit cells 9, sealing the resulting stack of unit cells 9 with the laminate layer 5, and pressing the sealed stack using a restraining jig 6. Note that the laminate layer 5, extraction electrode 31, and negative electrode tab 32 that appear on the left side of the unit cells 9 in the figure are omitted from the illustration.

In addition, the positive electrode tabs 22 at the tips of the extraction electrodes 21 extending from the positive electrode current collector 2 of each cell 9 are stacked and connected, and the positive electrode tabs 22 are positioned closer to the restraining jig 6 shown in the lower part of Figure 11. Although not shown, the negative electrode tabs 32 at the tips of the extraction electrodes 31 extending from the negative electrode current collector 3 of each cell 9 are stacked and connected, and the negative electrode tabs 32 are positioned closer to the restraining jig 6 shown in the lower part of Figure 11. Therefore, in the fourth embodiment, all of the cells 9 are connected in parallel.

In the all-solid-state battery 100 of the fourth embodiment, when charging is performed, the entire laminate expands in the thickness direction, but the positional relationship between the adjacent cells 9 in the thickness direction at the positive electrode tab 22 and the negative electrode tab 32, i.e., the cell 9 adjacent to the restraining jig 6 shown at the bottom of Figure 11, remains almost unchanged before and after charging the all-solid-state battery 100. Therefore, with respect to the cell 9, no stress is generated that pulls the power generating element 1 toward the positive electrode tab 22 via the extraction electrode 21, nor that pulls the power generating element 1 toward the negative electrode tab 32 via the extraction electrode 31.

On the other hand, for cells 9 that are separated from the positive electrode tab 22 and negative electrode tab 32 in the thickness direction, particularly cells 9 adjacent to the restraining jig 6 shown in the upper part of Figure 11, the positional relationship between the positive electrode tab 22 and negative electrode tab 32 changes significantly when the all-solid-state battery 100 is charged. Therefore, for these cells 9, a strong stress is generated that pulls the power generating element 1 toward the positive electrode tab 22 via the extraction electrode 21, and a strong stress is generated that pulls the power generating element 1 toward the negative electrode tab 32 via the extraction electrode 31.

However, in the fourth embodiment, the elastic body 4a of the cell 9 adjacent to the restraining jig 6 shown in the upper part of Figure 11 is made of a material with a higher Young's modulus than the elastic bodies 4 of the other cells 9. For example, Kapton (registered trademark) (3.3 GPa) is used for the elastic body 4a adjacent to the upper restraining jig 6 in Figure 11, and for example, PTFE (0.5 GPa) is used for the other elastic bodies 4.

For the same reasons as in the third embodiment, in the fourth embodiment, the tensile stress generated during charging and discharging can be reduced for the power generating element 1 of the cell 9 adjacent to the restraining jig 6 shown in the upper part of Figure 11, thereby suppressing damage to the power generating element 1, particularly breakage of the outer corners 111.

Furthermore, in the fourth embodiment, the entire all-solid-state battery 100 is heated when the positive electrode tab 22 and the negative electrode tab 32 are welded, respectively, and this heat causes the all-solid-state battery 100 to expand in the thickness direction. Even in this case, the thickness-wise positional relationship between the cell 9 adjacent to the restraining jig 6 shown in the upper part of Figure 11 and the positive electrode tab 22 and the negative electrode tab 32 changes significantly. However, by using an elastic body 4a with a high Young's modulus as the elastic body 4 of the cell 9 as described above, the tensile stress generated when the positive electrode tab 22 and the negative electrode tab 32 are welded can be reduced, and damage to the power generation element 1, particularly breakage of the outer corners 111, can be suppressed.

In the all-solid-state batteries 100 of the third and fourth embodiments, a plurality of unit cells 9 each including a pair of current collectors (positive electrode current collector 2, negative electrode current collector 3), a power generating element 1, and an elastic body 4 are stacked, and the unit cells 9 are pressed in the thickness direction by a restraining jig 6. The extraction electrodes (extraction electrodes 21, 31) extending from the current collectors (positive electrode current collector 2, negative electrode current collector 3) are connected by tabs (positive electrode tab 22, negative electrode tab 32). In this all-solid-state battery 100, the Young's modulus of the elastic body 4a of the unit cell 9 closest to the restraining jig 6, or the elastic body 4a of the unit cell 9 separated from the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction (particularly, the elastic body 4a of the unit cell 9 closest to the restraining jig 6), is higher than the Young's modulus of the elastic body 4 of the unit cell 9 adjacent to the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction.

This reduces the tensile stress that may be applied to the power generation element 1 of the cell 9, which is separated from the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction, during charging and discharging, thereby preventing damage to the power generation element 1, particularly breakage of the outer corners 122 (corners 111). Furthermore, it reduces the tensile stress that occurs when welding the tabs (positive electrode tab 22, negative electrode tab 32) to the power generation element 1, thereby preventing damage to the power generation element 1, particularly breakage of the outer corners 111.

The above describes embodiments of the present invention, but these embodiments merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

REFERENCE SIGNS LIST 100 All-solid-state battery 1 Power generating element 11 Positive electrode layer 12 Solid electrolyte 13 Deposit layer 2 Positive electrode current collector 3 Negative electrode current collector 4 Elastic body 9 Single cell

Claims (7)

An all-solid-state battery in which a power generating element part is disposed between a pair of current collectors, the power generating element part being formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing a lithium alloy or lithium metal, and an elastic body is further disposed so as to cover the outer periphery of the power generating element part,
the elastic body is formed of a material having a lower Young's modulus than the solid electrolyte layer, and is disposed apart from the positive electrode layer, the solid electrolyte layer , and the negative electrode layer, and a gap is formed between the power generation element unit consisting of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer and the elastic body . The all-solid-state battery described in claim 1, wherein an elastic adhesive is disposed between the elastic body and the current collector. The all-solid-state battery described in claim 2, wherein the elastic adhesive is an acrylic-modified silicone resin-based elastic adhesive or a two-part mixed curing type epoxy-modified silicone-based elastic adhesive. The all-solid-state battery described in any one of claims 1 to 3, wherein the Young's modulus of the elastic body is 5 GPa or less. The all-solid-state battery described in any one of claims 1 to 4, wherein the solid electrolyte layer is a sulfide-based solid electrolyte material. In an all-solid-state battery formed by stacking a plurality of unit cells each including a pair of the current collectors, the power generating element portion, and the elastic body, pressing the unit cells in a thickness direction with a restraining jig, and connecting extraction electrodes extending from the current collectors with tabs,
6. The all-solid-state battery according to claim 1, wherein the Young's modulus of the elastic body of the unit cell that is closest to the restraining jig is higher than the Young's modulus of the elastic body of the unit cell that is adjacent to the tab in the thickness direction. A method for manufacturing an all-solid-state battery, comprising: disposing a power generating element unit between a pair of current collectors, the power generating element unit being formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing a lithium alloy or lithium metal; and further disposing an elastic body so as to cover the outer periphery of the power generating element unit;
a power generating element section including the positive electrode layer, the solid electrolyte layer, and the negative electrode layer; a power generating element section including the positive electrode layer , the solid electrolyte layer, and the negative electrode layer; a power generating element section including the positive electrode layer, the solid electrolyte layer, and the negative electrode layer ;