All-solid-state battery

Abstract

To provide an all-solid battery reducing damages onto a solid electrolyte layer at the time of charging.SOLUTION: In an all-solid battery comprising positive electrode layers, solid electrolyte layers, and negative electrode collector foils, elastic bodies are arranged so as to each surround an outer periphery of the solid electrolyte layer. The elastic body comprises: an outer member that forms an outer periphery of the elastic body and is joined interposed from a thickness direction of the all-solid battery; and an inner member that forms an inner periphery of the elastic body. An inner peripheral surface of the inner member is a first inclined surface inclined toward the positive electrode layer side, and the solid electrolyte layer contacts the first inclined surface when the all-solid battery is in a completely discharged state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an all-solid-state battery, in which a structure consisting of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is sandwiched between a positive electrode current collector foil and a negative electrode current collector foil, a heat-resistant insulating member is arranged so as to surround the outer periphery of the structure, and the inner periphery of the insulating member and a region inside the inner periphery are heated and compressed in the stacking direction of the structure.

[0003] In Patent Document 1, the heat compression as described above prevents the thinning of the solid electrolyte layer and short circuits between the positive and negative electrodes caused by softening of the solid electrolyte layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5131283 Summary of the Invention [Problem to be solved by the invention]

[0005] When the all-solid-state battery of Patent Document 1 is charged, a lithium metal layer is deposited between the negative electrode layer and the negative electrode current collector foil, causing the thickness of the structure to expand by this amount, and the thickness of the insulating member to also expand accordingly. As a result, the solid electrolyte layer may be subjected to stress (frictional force) from the insulating member due to the expansion of the insulating member, which may cause damage.

[0006] An object of the present invention is to provide an all-solid-state battery that reduces damage to a solid electrolyte layer during charging. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention is an all-solid-state battery including a positive electrode layer, a solid electrolyte layer, and a negative electrode current collector foil, and includes an elastic body arranged so as to surround the outer periphery of the solid electrolyte layer, and the elastic body includes an outer member that forms the outer periphery of the elastic body and is sandwiched and joined from the thickness direction of the all-solid-state battery, and an inner member that forms the inner periphery of the elastic body. The inner periphery surface of the inner member is a first inclined surface that is inclined toward the positive electrode layer. The solid electrolyte layer is a first inclined surface that is inclined toward the positive electrode layer when the all-solid-state battery is in a fully discharged state. The solid-state battery is provided with a central portion that contacts the negative electrode current collector foil, a peripheral portion that forms the outer periphery of the solid electrolyte layer in a plan view, that is thinner than the central portion, and that is spaced apart from the negative electrode current collector foil, and an inclined portion that is disposed so as to go around between the central portion and the peripheral portion, that is connected to the main surface of the central portion that faces the negative electrode current collector foil and the main surface of the peripheral portion that faces the negative electrode current collector foil, and that has a second inclined surface that comes into contact with the first inclined surface when the all-solid-state battery is in a fully discharged state. . [Effects of the Invention]

[0008] Because the all-solid-state battery is pressed in the thickness direction, the solid electrolyte layer and the elastic body are in a mutually pressing relationship in the planar direction. Furthermore, when the all-solid-state battery is charged, a lithium metal layer is deposited between the negative electrode current collector foil and the solid electrolyte layer. The elastic body expands (stretches) in the thickness direction in response to changes in the thickness of the lithium metal layer, and the solid electrolyte layer is subjected to a frictional force from the lithium metal layer and the elastic body. However, according to the present invention, the solid electrolyte layer presses the first inclined surface of the inner member, so the stress is dispersed into a planar component (toward the outer periphery of the elastic body) and a thickness component (toward the negative electrode current collector foil). Therefore, even when the all-solid-state battery is charged and a lithium metal layer is deposited, the frictional force is reduced based on the magnitude of the thickness component. Furthermore, when the all-solid-state battery is charged, the inner member is displaced in a direction separating the first inclined surface and the solid electrolyte layer, and the frictional force is reduced based on the amount of displacement of the inner member. Furthermore, when the first inclined surface and the solid electrolyte layer are completely separated, the frictional force disappears. As a result, the frictional force generated between the solid electrolyte layer and the lithium metal layer and between the solid electrolyte layer and the elastic body can be reduced, thereby reducing damage to the solid electrolyte layer. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of the all-solid-state battery according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the all-solid-state battery of the first embodiment, in which the left side of the vertically extending dashed line in the drawing shows a fully discharged state, and the right side shows a fully charged state. [Figure 3]FIG. 3 is a cross-sectional view of an all-solid-state battery of a comparative example, in which the left side of the vertically extending dashed line in the figure shows a fully discharged state, and the right side shows a fully charged state. [Figure 4] FIG. 4 is a partially enlarged view (B) of FIG. 2, showing the case where a lithium metal layer is filled between the elastic body and the solid electrolyte layer. [Figure 5] FIG. 5(a) is a cross-sectional view of a first modified example of the all-solid-state battery of the first embodiment (corresponding to the partially enlarged view (A) of FIG. 2), and FIG. 5(b) is a cross-sectional view of a second modified example of the all-solid-state battery of the first embodiment (corresponding to the partially enlarged view (A) of FIG. 2). [Figure 6] FIG. 6 is a cross-sectional view of the all-solid-state battery according to the second embodiment. [Figure 7] FIG. 7 is a cross-sectional view of the all-solid-state battery of the third embodiment, in which the left side of the vertically extending dashed line in the drawing shows a fully discharged state, and the right side shows a fully charged state. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] FIG. 1 is a cross-sectional view of an all-solid-state battery 100 according to the first embodiment. The all-solid-state battery 100 according to the first 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 battery that houses multiple stacks of anode current collector foils 3, power generating element parts 1, and cathode current collector foils 2, each of which will be described below, sealed with a laminate layer (not shown) that is a battery exterior material. The stacked-type battery can be made compact and have a high capacity.

[0011] The all-solid-state battery 100 is formed by alternately stacking negative electrode current collector foils 3 and positive electrode current collector foils 2, with a power generating element 1 interposed between the negative electrode current collector foils 3 and positive electrode current collector foils 2 that are adjacent to each other in the stacking direction, and pressing them together in the stacking direction. The power generating element 1 basically has a stacked structure made up of a solid electrolyte layer 12 and a positive electrode layer 11.

[0012] 1, the power generating element 1, whose lower part is connected to the positive electrode current collector foil 2 and whose upper part is connected to the negative electrode current collector foil 3, is laminated in this order from below, a positive electrode layer 11 and a solid electrolyte layer 12. Also, in the power generating element 1, whose lower part is connected to the negative electrode current collector foil 3 and whose upper part is connected to the positive electrode current collector foil 2, is laminated in this order from below, a solid electrolyte layer 12 and a positive electrode layer 11.

[0013] In addition, an elastic body 4 and a frame material 5 are arranged to cover the side surfaces of the power generating element section 1, as will be described in detail later.

[0014] In the all-solid-state battery 100 of the first embodiment, by connecting the negative electrode current collector foils 3 in parallel and connecting the positive electrode current collector foils 2 in parallel, it is possible to electrically connect all of the power generating element parts 1 in parallel. Note that in this embodiment, the negative electrode current collector foils 3, power generating element parts 1, and positive electrode current collector foils 2 do not need to be stacked in multiple layers and may be single-layered.

[0015] The all-solid-state battery 100 of the first embodiment is configured in the shape of, for example, a circular or rectangular sheet before being housed in a battery exterior material. The appearance and internal electrical connection state (electrode structure) of the all-solid-state battery 100 of the present embodiment are not particularly limited.

[0016] The appearance of the all-solid-state battery 100 can be circular, elliptical, or rectangular in plan view. Alternatively, it may be cylindrical in shape, in which a single-layer or multiple-layer power generating element 1 is wound and housed. The electrode structure of the all-solid-state battery 100 may be either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). In other words, the configuration of the all-solid-state battery 100 other than the configuration described below is not particularly limited, regardless of whether it is publicly known or not.

[0017] 2 is a cross-sectional view of the all-solid-state battery 100 of the first embodiment, with the left side of the vertically extending dashed line in the figure showing a fully discharged state and the right side showing a fully charged state. Here, the fully discharged state refers to a state in which the open-circuit voltage of the all-solid-state battery 100 is equal to or lower than a predetermined lower limit voltage, and the fully charged state refers to a state in which the open-circuit voltage of the all-solid-state battery 100 is equal to or higher than a predetermined reference voltage that is higher than the above-mentioned lower limit voltage.

[0018] The positive electrode current collector foil 2 is a thin plate made of a metal such as aluminum (Al), and the negative electrode current collector foil 3 is a thin plate made of a metal such as stainless steel (SUS) or copper (Cu).

[0019] As described above, the power generating element 1 is interposed between the negative electrode current collector foil 3 and the positive electrode current collector foil 2, and basically has a laminated structure of a positive electrode layer 11 and a solid electrolyte layer 12. Furthermore, the power generating element 1 has a smaller area than the positive electrode current collector foil 2 and the negative electrode current collector foil 3 in a plan view, and is disposed inside the outer contours of the positive electrode current collector foil 2 and the negative electrode current collector foil 3.

[0020] The positive electrode layer 11 is disposed on both main surfaces of the positive electrode current collector foil 2 (in the case of a single layer, the main surface of the positive electrode current collector foil 2 facing the negative electrode current collector foil 3). The positive electrode layer 11 is preferably formed, for example, from NMC811 (lithium nickel cobalt manganese oxide) as a main raw material. The positive electrode layer 11 also 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 is capable of releasing lithium ions during charging and absorbing lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur.

[0021] The solid electrolyte layer 12 contains a solid electrolyte as a main component and is a layer interposed between the negative electrode current collector foil 3 and the positive electrode layer 11. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, but sulfide solid electrolytes are preferred. Examples of sulfide solid electrolytes include LPS-based (e.g., argyrodite (Li6PS5Cl), elastic modulus 1-30 GPa), LGPS-based (e.g., Li 10 GeP2S12 ) and materials having a modulus of elasticity higher than that of lithium metal (5 GPa) are preferred.

[0022] In the first embodiment, the solid electrolyte layer 12 is disposed on both main surfaces of the negative electrode current collector foil 3 (in the case of a single layer, the main surface of the negative electrode current collector foil 3 facing the positive electrode current collector foil 2). The solid electrolyte layer 12 is preferably disposed so that its outer shape accommodates the outer shape of the positive electrode layer 11 in a plan view.

[0023] The solid electrolyte layer 12 includes a central portion 121 that comes into contact with the negative electrode current collector foil 3 (when the all-solid-state battery 100 is in a fully discharged state), a peripheral portion 122 that forms the outer periphery of the solid electrolyte layer 12 in a planar view, that is thinner than the central portion 121, and that is spaced apart from the negative electrode current collector foil 3, and an inclined portion 123 that is arranged so as to go around between the central portion 121 and the peripheral portion 122, that is connected to the main surface of the central portion 121 that faces the negative electrode current collector foil 3 and the main surface of the peripheral portion 122 that faces the negative electrode current collector foil 3, and that includes a second inclined surface 123 a that comes into contact with the first inclined surface 42 a (when the all-solid-state battery 100 is in a fully discharged state).

[0024] The inner periphery of the peripheral portion 122 and the outer periphery of the inclined portion 123 are arranged so as to overlap with the outer periphery of the positive electrode layer 11 in a plan view.

[0025] As shown in FIG. 2 (and FIG. 1), an elastic body 4 and a frame member 5 are arranged to cover the outer periphery of the power generating element section 1.

[0026] The elastic body 4 has a frame shape that surrounds the outer shape of the periphery of the solid electrolyte layer 12. That is, if the solid electrolyte layer 12 is circular in plan view, the elastic body 4 has a circular ring shape, and if the solid electrolyte layer 12 is rectangular in plan view, the elastic body 4 has a rectangular frame shape.

[0027] The elastic body 4 is disposed so as to fill the space between the negative electrode current collector foil 3 and the solid electrolyte layer 12. The elastic body 4 includes an outer member 41 that forms the outer periphery of the elastic body 4 and is sandwiched and joined between the main surface of the negative electrode current collector foil 3 and the main surface of the peripheral edge portion 122, and an inner member 42 that forms the inner periphery of the elastic body 4.

[0028] As shown in the partially enlarged views (A) and (B) of Figure 2, the outer member 41 has a bonding layer 7 disposed on its bonding surface, and is bonded to the negative electrode current collector foil 3 and the peripheral portion 122 via the bonding layer 7.

[0029] The surface of the inner member 42 facing the negative electrode current collector foil 3 is joined to the negative electrode current collector foil 3 via a joining layer 7. However, the inner member 42 is integral with the outer member 41, and the inner member 42 does not necessarily have to be joined directly to the negative electrode current collector foil 3. The surface of the inner member 42 facing the solid electrolyte layer 12 is a first inclined surface 42a that is inclined toward the positive electrode layer 11.

[0030] Here, the first inclined surface 42a of the inner member 42 and the second inclined surface 123a of the inclined portion 123 of the solid electrolyte layer 12 overlap each other in a plan view, and are in contact (surface contact) with each other (when the all-solid-state battery 100 is in a fully discharged state).

[0031] The elastic body 4 (outer member 41, inner member 42) is preferably made of a material having a modulus of elasticity lower than that of lithium metal (5 GPa), and examples of such materials include polyethylene terephthalate (PET) (4 GPa), Kapton (registered trademark) (3.3 GPa), epoxy resin (2.4 GPa), polypropylene (PP) (2 GPa), polytetrafluoroethylene (PTFE) (0.5 GPa), and rubber (natural rubber, synthetic rubber) (0.1 GPa). In this embodiment, the modulus of elasticity preferably satisfies the relationship "modulus of elasticity of solid electrolyte layer 12" > "modulus of elasticity of lithium metal layer 13 (lithium metal)" > "modulus of elasticity of elastic body 4."

[0032] The frame material 5 is disposed so as to be sandwiched between the main surface of the positive current collector foil 2 and the main surface of the solid electrolyte layer 12 on the side of the positive current collector foil 2. Similarly to the elastic body 4, the frame material 5 has a circumferential frame shape that follows the outline of the solid electrolyte layer 12 in a planar view. The frame material 5 can be made of the same material as the elastic body 4. Although not shown in the drawings, the frame material 5 is bonded to the positive current collector foil 2 and the solid electrolyte layer 12 via a bonding layer 7, similar to the elastic body 4.

[0033] Examples of adhesives that can be used to form the bonding layer 7 include resin-based adhesives such as acrylic-modified silicone resin elastic adhesives (e.g., Super X (registered trademark) No. 8008, Super XG No. 777, and SX720W manufactured by Cemedine Co., Ltd.), two-component mixed curing epoxy-modified silicone elastic adhesives (e.g., EP001K manufactured by Cemedine Co., Ltd.), and other thermosetting resins such as epoxy resins and silicone resins. These adhesives have the property of absorbing stress and become strong, flexible rubber-like elastic bodies.

[0034] As shown to the right of the vertically extending dashed line in FIG. 2 , when the all-solid-state battery 100 of the first embodiment is charged (fully charged), lithium ions in the positive electrode layer 11 pass through the solid electrolyte layer 12 and are deposited as a lithium metal layer 13 between the negative electrode current collector foil 3 and the solid electrolyte layer 12. The lithium metal layer 13 is in contact with the negative electrode current collector foil 3 and the solid electrolyte layer 12. When discharging of the charged all-solid-state battery 100 begins, lithium ions pass from the lithium metal layer 13 through the solid electrolyte layer 12 and are occluded in the positive electrode layer 11. Upon full discharge, the lithium metal layer 13 disappears (to the left of the vertically extending dashed line in FIG. 2 ). In a fully discharged state, the solid electrolyte layer 12 is in contact with the negative electrode current collector foil 3, thereby electrically connecting the negative electrode current collector foil 3. In a fully charged state or a certain charge state less than the fully charged state, the solid electrolyte layer 12 is electrically connected to the negative electrode current collector foil 3 via the lithium metal layer 13.

[0035] At this time, the height of the elastic body 4 expands and contracts (stretches and contracts) in accordance with changes in the thickness of the lithium metal layer 13. In particular, since the elastic modulus of lithium metal is 5 GPa, by using a material having an elastic modulus of 5 GPa or less as the material for the elastic body 4, as described above, the elastic body 4 becomes less soft than the lithium metal layer 13, and the conformability of the elastic body 4 in the height direction (thickness direction of the all-solid-state battery 100) is improved.

[0036] Furthermore, by using the above adhesive in bonding layer 7, the height of bonding layer 7 can be adjusted to follow the change in thickness of lithium metal layer 13, thereby reducing the load on elastic body 4 accordingly.

[0037] [Comparison between Comparative Example and First Embodiment] 3 is a cross-sectional view of an all-solid-state battery 100A of the comparative example, with the left side of the vertically extending dashed line in the figure showing a fully discharged state and the right side showing a fully charged state. The all-solid-state battery 100A of the comparative example does not have the inclined portion 123 (second inclined surface 123a) of the solid electrolyte layer 12, as compared to the all-solid-state battery 100 of the first embodiment, and has a central portion 121 arranged following the outer periphery of the positive electrode layer 11 in a plan view, and a peripheral portion 122 arranged in a portion overlapping with the elastic body 4. Furthermore, the elastic body 4 is composed of only an outer member 41, and the inner member 42 is omitted.

[0038] The all-solid-state battery 100A (all-solid-state battery 100) is configured to receive a pressing force from the stacking direction (thickness direction) of the positive electrode current collector foil 2, the power generating element 1, and the negative electrode current collector foil 3, thereby improving the charge / discharge efficiency of the all-solid-state battery 100A (all-solid-state battery 100). For this reason, the solid electrolyte layer 12 is pressed from the thickness direction, and the solid electrolyte layer 12 accordingly applies a force that spreads in the planar direction to the elastic body 4. More specifically, as shown in the partially enlarged view (A) of FIG. 3, a force (arrow a in the figure) directed outward from the solid electrolyte layer 12 in the planar direction is applied to the elastic body 4, and the elastic body 4 applies this resistance force to the solid electrolyte layer 12. For this reason, the solid electrolyte layer 12 and the elastic body 4 are in a pressing relationship with each other in the planar direction.

[0039] 3B, when the all-solid-state battery 100A of the comparative example is charged, a lithium metal layer 13 is deposited between the negative electrode current collector foil 3 and the solid electrolyte layer 12, and the gap between the positive electrode current collector foil 2 and the negative electrode current collector foil 3 increases by the thickness of the lithium metal layer 13. At that time, the elastic body 4 expands (stretches) in the thickness direction by the thickness of the lithium metal layer 13.

[0040] However, lithium metal layer 13 also receives a pressing force from the thickness direction, and as a result, a force spreading in the planar direction is also generated in lithium metal layer 13. Therefore, a frictional force is generated between elastic body 4 and lithium metal layer 13, and elastic body 4 receives a tensile stress in the direction indicated by arrow b in the figure due to this frictional force.

[0041] Therefore, the amount of expansion of the portion of the elastic body 4 facing the lithium metal layer 13 in the thickness direction (the portion surrounded by the dashed line (C) in the figure) is smaller than the amount of expansion (uniform expansion amount) when the elastic body 4 expands (stretches) uniformly in the thickness direction.

[0042] On the other hand, the amount of expansion of the portion of the elastic body 4 facing the solid electrolyte layer 12 in the thickness direction (area (D) in the figure) is larger than the uniform amount of expansion by the amount that the amount of expansion of the portion of the elastic body 4 surrounded by the dashed line (C) in the figure is smaller.

[0043] Therefore, the stress (shear stress) at the joint between the central portion 121 and the peripheral portion 122 of the solid electrolyte layer 12, i.e., the portion surrounded by (E) in the figure, becomes larger than when the elastic body 4 expands uniformly in the thickness direction, and there is a risk that the solid electrolyte layer 12 will be damaged.

[0044] Furthermore, the frictional force that the solid electrolyte layer 12 receives from the elastic body 4 depends on the magnitude of the force (arrow a in the figure) with which the solid electrolyte layer 12 (and the lithium metal layer 13) presses the elastic body 4 outward in the planar direction, and is equal to the force with which the solid electrolyte layer 12 (and the lithium metal layer 13) presses the elastic body 4.

[0045] In addition, the outer periphery of the central portion 121 of the solid electrolyte layer 12, which is in contact with the elastic body 4, receives a frictional force from the elastic body 4 due to the expansion of the elastic body 4 caused by the deposition of the lithium metal layer 13, which may cause damage to the side surface of the central portion 121 of the solid electrolyte layer 12.

[0046] On the other hand, as shown in the partially enlarged view (A) of FIG. 2, in the all-solid-state battery 100 of the first embodiment, the second inclined surface 123a of the inclined portion 123 of the solid electrolyte layer 12 and the first inclined surface 42a of the inner member 42 of the elastic body 4 are in contact with each other.

[0047] In this case, the pressing force that the elastic body 4 receives from the solid electrolyte layer 12 is in the normal direction (arrow a in the figure) of the second inclined surface 123a and the first inclined surface 42a, and this force is distributed into a component that presses the elastic body 4 outward in the planar direction (arrow b in the figure) and a component that presses the elastic body 4 toward the positive electrode layer 11 (thickness direction) (arrow c in the figure).

[0048] Therefore, the magnitude of the force with which the solid electrolyte layer 12 presses the elastic body 4 outward in the planar direction (arrow b in the figure), i.e., the magnitude of the frictional force that the solid electrolyte layer 12 receives from the elastic body 4, decreases based on the magnitude of the force with which the elastic body 4 presses the positive electrode layer 11 side (arrow c in the figure).

[0049] More specifically, if the magnitude of the force with which the solid electrolyte layer 12 presses the elastic body 4 in the normal direction of the second inclined surface 123a is a, the component of the force with which the solid electrolyte layer 12 presses the elastic body 4 in the planar direction is b, and the component of the force with which the solid electrolyte layer 12 presses the elastic body 4 toward the positive electrode layer 11 (thickness direction) is c, then a 2 =b 2 +c 2 Therefore, in the all-solid-state battery 100 of the first embodiment, the frictional force that the solid electrolyte layer 12 receives from the elastic body 4 is (ab) / a=(a-(a 2 -c 2 ) 1 / 2 ) / a.

[0050] Furthermore, when the all-solid-state battery 100 of the first embodiment is charged and the lithium metal layer 13 is deposited between the negative electrode current collector foil 3 and the solid electrolyte layer 12, the first inclined surface 42a of the inner member 42 of the elastic body 4 is displaced in a direction away from the solid electrolyte layer 12 and the lithium metal layer 13, and therefore the pressing force that the solid electrolyte layer 12 and the lithium metal layer 13 apply to the first inclined surface 42a of the elastic body 4, i.e., the frictional force that the elastic body 4 receives from the solid electrolyte layer 12 and the lithium metal layer 13, decreases.

[0051] Therefore, the frictional force that elastic body 4 receives from lithium metal layer 13 and the frictional force that elastic body 4 receives from solid electrolyte layer 12 each decrease as the thickness of lithium metal layer 13 increases.

[0052] Therefore, the unevenness of the expansion of the elastic body 4, as in the comparative example, is reduced, and the stress on the joint portion between the inclined portion 123 and the peripheral portion 122 of the solid electrolyte layer 12 (the specific region surrounded by the dashed circle (E) in the enlarged partial view (B) of FIG. 2) is reduced accordingly, thereby reducing damage to the joint portion of the solid electrolyte layer 12. Similarly, the frictional force of the solid electrolyte layer 12 with respect to the second inclined surface 123a is reduced, thereby reducing damage to the inclined portion 123 (second inclined surface 123a).

[0053] 2B, as the deposition of the lithium metal layer 13 progresses, the inner member 42 (first inclined surface 42a) of the elastic body 4 is completely separated from the inclined portion 123 (second inclined surface 123a) of the solid electrolyte layer 12 and the lithium metal layer 13. At this time, a gap 6 is formed by the first inclined surface 42a, the second inclined surface 123a, and the lithium metal layer 13.

[0054] This allows the elastic body 4 to expand uniformly in the thickness direction, further reducing stress in the specific region surrounded by the dashed circle (E) in the partially enlarged view (B) of Figure 2. Furthermore, since the inclined portion 123 (second inclined surface 123a) of the solid electrolyte layer 12 is spaced apart from the inner member 42 (first inclined surface 42a) of the elastic body 4, frictional force with the inclined portion 123 (second inclined surface 123a) of the solid electrolyte layer 12 is avoided, and damage to the inclined portion 123 (second inclined surface 123a) can be reduced.

[0055] [Lithium metal layer 13] FIG. 4 is a partially enlarged view (B) of FIG. 2 , showing a case where the lithium metal layer 13 is filled between the elastic body 4 and the solid electrolyte layer 12. As described above, as the deposition of the lithium metal layer 13 progresses, a gap 6 is formed between the elastic body 4 and the solid electrolyte layer 12. The gap 6 is located inside the outer shape of the negative electrode current collector foil 3 and the outer shape of the positive electrode current collector foil 2 in a plan view. Therefore, the lithium metal layer 13 may be deposited (filled) in this space. Even in this case, the elastic body 4 completely seals the gap 6, preventing leakage of lithium metal to the outside. Furthermore, since the lithium metal fills the gap 6, an increase in the thickness of the lithium metal layer 13 (the distance between the negative electrode current collector foil 3 and the solid electrolyte layer 12) can be suppressed. This suppresses expansion (extension) of the elastic body 4 and reduces the burden on the elastic body 4.

[0056] It should be noted that although there are cases where the lithium metal in the lithium metal layer 13 propagates through the interface between the solid electrolyte layer 12 and the elastic body 4, reaches the positive electrode layer 11, and causes a short circuit, the peripheral portion 122 acts as a barrier against the lithium metal, thereby reducing the possibility of a short circuit in the all-solid-state battery 100.

[0057] [Modification of the first embodiment] FIG. 5(a) is a cross-sectional view (partially enlarged view (A) of FIG. 2) of a first modified example of the all-solid-state battery 100 of the first embodiment, and FIG. 5(b) is a cross-sectional view (partially enlarged view (A) of FIG. 2) of a second modified example of the all-solid-state battery 100 of the first embodiment.

[0058] 5(a), in the first modification, inner member 42 of elastic body 4 has inclined surface 42b with a gentle inclination angle and inclined surface 42c with a steeper inclination angle than inclined surface 42b. Inclined portion 123 of solid electrolyte layer 12 has inclined surface 123b in surface contact with inclined surface 42b and inclined surface 123c in surface contact with inclined surface 42c.

[0059] 5(b), in the second modification, the first inclined surface 42a of the inner member 42 of the elastic body 4 is a curved inclined surface that is convex. The second inclined surface 123a of the inclined portion 123 of the solid electrolyte layer 12 is a curved inclined surface that is concave and is in surface contact with the first inclined surface 42a.

[0060] In any of the modified examples, it is preferable that the first inclined surface 42a (inclined surfaces 42b, 42c) of the inner member 42 of the elastic body 4 is inclined so as to face the positive electrode layer 11, that is, that the surface of the inner member 42 that is joined to the negative electrode current collector foil 3 and the first inclined surface 42a (inclined surfaces 42b, 42c) are disposed so as to form an angle of less than 90 degrees. As a result, as the lithium metal layer 13 is deposited, the elastic body 4 is displaced in a direction away from the solid electrolyte layer 12, thereby reducing the frictional force between the solid electrolyte layer 12 and the elastic body 4.

[0061] [Effects of the first embodiment] According to the all-solid-state battery 100 of the first embodiment, in the all-solid-state battery 100 including the positive electrode layer 11, the solid electrolyte layer 12, and the negative electrode current collector foil 3, the elastic body 4 is arranged so as to surround the outer periphery of the solid electrolyte layer 12, and the elastic body 4 includes an outer member 41 that forms the outer periphery of the elastic body 4 and is sandwiched and joined from the thickness direction of the all-solid-state battery 100, and an inner member 42 that forms the inner periphery of the elastic body 4, and the inner surface of the inner member 42 is a first inclined surface 42a that is inclined toward the positive electrode layer 11, and the solid electrolyte layer 12 (second inclined surface 123a) is in contact with the first inclined surface 42a when the all-solid-state battery 100 is in a fully discharged state.

[0062] Because the all-solid-state battery 100 is pressed in the thickness direction, the solid electrolyte layer 12 and the elastic body 4 are in a mutually pressing relationship in the planar direction. Furthermore, when the all-solid-state battery 100 is charged, a lithium metal layer 13 is deposited between the negative electrode current collector foil 3 and the solid electrolyte layer 12. The elastic body 4 expands (stretches) in the thickness direction in response to changes in the thickness of the lithium metal layer 13, and the solid electrolyte layer 12 is subjected to a frictional force from the lithium metal layer 13 and the elastic body 4. However, because of the above configuration, the solid electrolyte layer 12 presses the first inclined surface 42a of the inner member 42, and the stress is dispersed into a component in the planar direction (toward the outer periphery of the elastic body 4) and a component in the thickness direction (toward the negative electrode current collector foil 3). Therefore, even when the all-solid-state battery 100 is charged and the lithium metal layer 13 is deposited, the frictional force is reduced based on the magnitude of the component in the thickness direction. Furthermore, when the all-solid-state battery 100 is charged, the inner member 42 is displaced in a direction separating the first inclined surface 42a from the solid electrolyte layer 12, and the frictional force is reduced based on the amount of displacement of the inner member 42. Furthermore, when the first inclined surface 42a and the solid electrolyte layer 12 are completely separated from each other, the frictional force disappears. As a result, the frictional force generated between the solid electrolyte layer 12 and the lithium metal layer 13 and the elastic body 4 is reduced, and damage to the solid electrolyte layer 12 can be reduced.

[0063] In the first embodiment, the solid electrolyte layer 12 includes: a central portion 121 that comes into contact with the negative electrode current collector foil 3 when the all-solid-state battery 100 is in a fully discharged state; a peripheral portion 122 that forms the outer periphery of the solid electrolyte layer 12 in a planar view, that is thinner than the central portion 121, and that is spaced apart from the negative electrode current collector foil 3; and an inclined portion 123 that is arranged so as to go around between the central portion 121 and the peripheral portion 122, that is connected to a main surface of the central portion 121 that faces the negative electrode current collector foil 3 and a main surface of the peripheral portion 122 that faces the negative electrode current collector foil 3, and that includes a second inclined surface 123 a that comes into contact with the first inclined surface 42 a when the all-solid-state battery 100 is in a fully discharged state, and the outer member 41 is sandwiched and joined between the negative electrode current collector foil 3 and the peripheral portion 122.

[0064] In the above configuration, when the all-solid-state battery 100 is charged (the lithium metal layer 13 is deposited), stress is concentrated at the boundary between the inclined portion 123 and the peripheral portion 122 of the solid electrolyte layer 12 due to the frictional force between the elastic body 4 and the lithium metal layer 13 and the frictional force between the elastic body 4 and the solid electrolyte layer 12 (a specific region surrounded by a dashed circle (E) in the enlarged partial view (B) of FIG. 2). However, as described above, when the all-solid-state battery 100 is charged, the inner member 42 is displaced in a direction separating the first inclined surface 42a and the solid electrolyte layer 12. Therefore, both of the frictional forces are reduced, which reduces the concentration of stress in the specific region and reduces damage to the solid electrolyte layer 12.

[0065] Furthermore, although there are cases where the lithium metal in the lithium metal layer 13 propagates through the interface between the solid electrolyte layer 12 and the elastic body 4 and reaches the positive electrode layer 11, causing a short circuit, the peripheral portion 122 acts as a barrier to the lithium metal, thereby reducing the risk of a short circuit in the all-solid-state battery 100.

[0066] In the first embodiment, a bonding layer 7 made of an elastic adhesive is disposed on the bonding surface of the elastic body 4. This allows the height (thickness) of the elastic body 4 to expand and contract in accordance with changes in the thickness of the lithium metal layer 13, thereby reducing the load on the elastic body 4.

[0067] [Second embodiment] 6 is a cross-sectional view of an all-solid-state battery 100 of the second embodiment. In the all-solid-state battery 100 of the second embodiment, in the all-solid-state battery 100 of the first embodiment, the inner periphery of the inner member 42 (the boundary between the inner member 42 and the outer member 41) is disposed at a position overlapping with the outer periphery of the positive electrode layer 11 in a plan view or at a position outside the outer periphery of the positive electrode layer 11. As a result, the positive electrode layer 11 is disposed at a position overlapping with the outer periphery of the lithium metal layer 13 in a plan view or at a position inside the outer periphery. Therefore, the entire positive electrode layer 11 can be used as a region where a battery reaction (exchange of lithium ions) is possible, and it is possible to eliminate unused regions of the positive electrode layer 11 for the battery reaction.

[0068] [Third embodiment] 7 is a cross-sectional view of an all-solid-state battery 100 according to a third embodiment, with the left side of the vertically extending dashed line in the figure representing a fully discharged state and the right side representing a fully charged state. In the all-solid-state battery 100 according to the third embodiment, the peripheral edge 122 of the solid electrolyte layer 12 is omitted. As in the first embodiment, an insulating frame material 5 is disposed around the outer periphery of the positive electrode layer 11. As shown in the partially enlarged views (A) and (B) of FIG. 7, the outer member 41 of the elastic body 4 is sandwiched between the negative electrode current collector foil 3 and the frame material 5 and is bonded to the negative electrode current collector foil 3 and the frame material 5 via a bonding layer 7.

[0069] In the third embodiment, the solid electrolyte layer 12 also presses the first inclined surface 42a of the inner member 42, and therefore the stress is dispersed into a component in the surface direction (toward the outer periphery of the elastic body 4) and a component in the thickness direction (toward the negative electrode current collector foil 3) (see the partial enlarged view (A) of FIG. 2 ). Therefore, even when the all-solid-state battery 100 is charged and the lithium metal layer 13 is deposited, the frictional force is reduced based on the magnitude of the component in the thickness direction. Furthermore, when the all-solid-state battery 100 is charged, the inner member 42 is displaced in a direction separating the first inclined surface 42a and the solid electrolyte layer 12, and therefore the frictional force is reduced based on the amount of displacement of the inner member 42. Furthermore, as shown in the partial enlarged view (B) of FIG. 7 , when the first inclined surface 42a and the solid electrolyte layer 12 are completely separated, the frictional force disappears. As a result, the frictional force generated between the solid electrolyte layer 12 and the lithium metal layer 13 and the elastic body 4 is reduced, and damage to the solid electrolyte layer 12 can be reduced.

[0070] Here, the lithium metal layer 13 may be deposited between the elastic body 4 and the solid electrolyte layer 12 (see FIG. 4). In this case, the lithium metal layer 13 may travel along the interface between the elastic body 4 and the solid electrolyte layer 12 and reach the positive electrode layer 11 side, possibly causing a short circuit in the all-solid-state battery 100.

[0071] Therefore, it is preferable that the positive electrode layer 11 is disposed so that its outer shape is located inside the outer periphery of the inclined portion 123 of the solid electrolyte layer 12 in a plan view. That is, it is preferable that the solid electrolyte layer 12 is disposed so that its outer shape accommodates the outer shape of the positive electrode layer 11 inside in a plan view (this also applies to the first and second embodiments). This prevents the positive electrode layer 11 from contacting the interface between the solid electrolyte layer 12 and the elastic body 4, thereby reducing short-circuiting of the all-solid-state battery 100.

[0072] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate. [Explanation of symbols]

[0073] 100 all-solid-state battery, 1 power generation element, 11 positive electrode layer, 12 solid electrolyte, 13 lithium metal layer, 2 positive electrode current collector foil, 3 negative electrode current collector foil, 4 elastic body, 42a first inclined surface

Claims

1. In an all-solid-state battery including a positive electrode layer, a solid electrolyte layer, and a negative electrode current collecting foil, an elastic body is disposed around the outer periphery of the solid electrolyte layer; the elastic body includes an outer member that forms the outer periphery of the elastic body and is sandwiched and joined to the all-solid-state battery from a thickness direction; an inner member that forms an inner periphery of the elastic body, an inner circumferential surface of the inner member is a first inclined surface inclined toward the positive electrode layer, the solid electrolyte layer comprises: a central portion that comes into contact with the negative electrode current collector foil when the all-solid-state battery is in a fully discharged state; a peripheral portion that forms an outer periphery of the solid electrolyte layer in a plan view, that is thinner than the central portion, and that is spaced apart from the negative electrode current collector foil; and an inclined portion that is arranged so as to go around between the central portion and the peripheral portion, that is connected to a main surface of the central portion that faces the negative electrode current collector foil and a main surface of the peripheral portion that faces the negative electrode current collector foil, and that includes a second inclined surface that comes into contact with the first inclined surface when the all-solid-state battery is in a fully discharged state; the outer member is sandwiched and joined between the negative electrode current collecting foil and the peripheral edge portion.

2. an insulating frame material is disposed on the outer periphery of the positive electrode layer; The all-solid-state battery according to claim 1 , wherein the outer member is sandwiched and joined between the negative electrode current collector foil and the frame material.

3. 3. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer is disposed such that its outer shape accommodates the outer shape of the positive electrode layer in a plan view.

4. 4. The all-solid-state battery according to claim 1, wherein an inner periphery of the inner member is disposed at a position overlapping an outer periphery of the positive electrode layer or at a position outside the outer periphery of the positive electrode layer in a plan view.

5. 5. The all-solid-state battery according to claim 1, wherein a bonding layer made of an elastic adhesive is disposed on bonding surfaces of the outer member and the inner member with the negative electrode current collector foil and on a bonding surface of the outer member with the peripheral edge portion.

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