All-solid-state batteries

Abstract

To provide an all-solid-state battery that reduces the precipitation of lithium metal during discharge.SOLUTION: An all-solid-state battery 100 includes a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 containing lithium metal. The all-solid-state battery 100 further includes a low ion conductivity portion 14 arranged around the periphery of the positive electrode layer 11 and having a lower lithium-ion conductivity than the positive electrode layer 11. The low ion conductivity portion 14 overlaps the periphery of the negative electrode layer 13 in plan view.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, after forming an electrode, an ultraviolet-curable resin frame is transferred and attached so as to cover the outer periphery of the electrode.

[0003] In Patent Document 1, the above-mentioned technology is used to prevent short circuits and material slippage at the end portions in the planar direction of the all-solid-state battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-4697 Summary of the Invention [Problem to be solved by the invention]

[0005] When a resin frame is transferred as in Patent Document 1, stress concentration occurs in the outer periphery of the solid electrolyte layer due to hardening shrinkage of the resin frame, resulting in high density. As a result, the current density during discharge becomes high in this outer periphery, and precipitation of lithium metal (lithium dendrites) becomes prominent in the positive electrode layer and other parts adjacent to this outer periphery.

[0006] An object of the present invention is to provide an all-solid-state battery that reduces the deposition of lithium metal during discharge. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing lithium metal, and the outer periphery of the positive electrode layer is and adheres to the positive electrode layer. The low ion conductive portion is arranged so as to overlap the outer periphery of the negative electrode layer in a plan view, and has a low ion conductive portion having a lower lithium ion conductivity than the positive electrode layer. The region occupied by the material of the positive electrode layer and the region occupied by the insulating material are alternately arranged along the circumferential direction of the low ion conductive portion. . [Effects of the Invention]

[0008] According to the present invention, the low ion conductive portion is arranged at a stress concentration location in the region in the all-solid-state battery that can transfer lithium ions, thereby reducing the deposition of lithium metal during discharge. [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 main part 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 the fully charged state, and the right side shows the fully discharged state. [Figure 3] FIG. 3 is a graph showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery of the first embodiment. [Figure 4] FIG. 4 is a diagram showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery of the first comparative example. [Figure 5] FIG. 5 is a graph showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery of the second comparative example. [Figure 6] FIG. 6 is a diagram showing a first example of an arrangement mode of the low ion conductive portion constituting the all-solid-state battery of the first embodiment. [Figure 7] FIG. 7 is a diagram showing a second example of the arrangement of the low ion conductive portion constituting the all-solid-state battery according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing the blending ratio of the positive electrode material and the insulating material in the all-solid-state battery of the second embodiment, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress. [Figure 9] FIG. 9 is a diagram showing a first example of an arrangement of low ion conductive sections constituting the all-solid-state battery according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing a second example of the arrangement of the low ion conductive portion constituting the all-solid-state battery according to the second embodiment. [Figure 11] FIG. 11 is a diagram showing the blending ratio of the positive electrode material and the insulating material in the all-solid-state battery of the third embodiment, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress. [Figure 12] FIG. 12 is a cross-sectional view of the main part of the all-solid-state battery of the fourth embodiment, in which the left side of the vertically extending dashed line in the drawing shows the fully charged state, and the right side shows the fully discharged state. [Figure 13] FIG. 13 is a cross-sectional view of a main part of an all-solid-state battery according to the fifth embodiment. [Figure 14] 14A and 14B are diagrams showing a part of the manufacturing process of the all-solid-state battery of the first embodiment, in which FIG. 14A is a cross-sectional view before press molding, FIG. 14B is a cross-sectional view after press molding, FIG. 14C is a plan view after press molding, and FIG. 14D is a cross-sectional view after press molding (modified example). 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 has a stacked structure of a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13.

[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 the bottom up, with a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13. 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 the bottom up, with a negative electrode layer 13, a solid electrolyte layer 12, and a positive electrode layer 11.

[0013] Furthermore, a low ion-conductive portion 14 and an insulating layer 4 are arranged to cover the outer periphery (side surface) of the positive electrode layer 11, 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 charged state, and the right side showing a fully discharged 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 has a laminated structure of the positive electrode layer 11, the solid electrolyte layer 12, and the negative electrode layer 13. The positive electrode layer 11 and the negative electrode layer 13 have smaller areas than the positive electrode current collector foil 2 and the negative electrode current collector foil 3 in a plan view, and are arranged to be inside the outer periphery of the positive electrode current collector foil 2 and the outer periphery of 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 preferably contains a sulfur-containing positive electrode active material. 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, and 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 positive electrode layer 11 and the negative electrode layer 13. 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)), LGPS-based (e.g., Li 10 GeP2S 12 ) materials are preferred.

[0022] The negative electrode layer 13 is disposed on both main surfaces of the negative electrode current collector foil 3 (in the case of a single layer, the surface of the negative electrode current collector foil 3 facing the positive electrode current collector foil 2). The negative electrode layer 13 is composed of a negative electrode active material containing at least lithium metal or a lithium alloy. Alternatively, any material can be used as the material for the negative electrode layer 13 as long as it can absorb lithium ions during charging and release lithium ions during discharging.

[0023] The low ion-conductive portion 14 is formed by mixing, for example, the material of the positive electrode layer 11 (positive electrode material 111, see FIG. 6 etc.) and the material of the insulating layer 4 (insulating material 41, see FIG. 6 etc.), and is arranged so as to form a frame shape surrounding the outer periphery of the positive electrode layer 11. That is, in plan view, the low ion-conductive portion 14 is ring-shaped if the positive electrode layer 11 is circular, and is rectangular-shaped if the positive electrode layer 11 is rectangular. The positional relationship between the material of the positive electrode layer 11 and the material of the insulating layer 4 in the low ion-conductive portion 14 will be described later.

[0024] The insulating layer 4 is arranged in a frame shape surrounding the outer periphery of the low ion conductive portion 14. As the material of the insulating layer 4, ultraviolet curing resins such as Aronix (registered trademark) and Aronoxetane (registered trademark) can be used. As the material of the insulating layer 4, thermosetting resins such as polyethylene terephthalate (PET) and epoxy resin can also be used. Other materials that can be used for the insulating layer 4 include Kapton (registered trademark), polypropylene (PP), polytetrafluoroethylene (PTFE), rubber (natural rubber, synthetic rubber), etc.

[0025] As shown in the right-hand portion of the dashed-dotted line in FIG. 2 and in the partial detailed view, in a fully discharged state of the all-solid-state battery 100 of the first embodiment, lithium ions are released from the anode layer 13 in a region of the anode layer 13 that is inside the outer periphery of the cathode layer 11 in a plan view and that is in contact with the solid electrolyte layer 12, pass through the solid electrolyte layer 12, and are then occluded by the cathode layer 11. Therefore, the region of the anode layer 13 from which the lithium ions have been released forms a gap 131, and the thickness of the anode layer 13 is reduced by the amount of the gap 131. Meanwhile, the all-solid-state battery 100 of the first embodiment is pressed from the thickness direction. Therefore, in reality, the gap 131 disappears and the anode layer 13 and the anode current collector foil 3 deform toward the solid electrolyte layer 12. However, for convenience, the figure shows the state in which the gap 131 is formed. In this way, gap 131 practically disappears, so that contact between the surface of solid electrolyte layer 12 of negative electrode layer 13 and solid electrolyte layer 12 is maintained, and electrical connection between negative electrode layer 13 and solid electrolyte layer 12 is also maintained. Note that the region where gap 132 is formed may be formed as a region where the lithium density is lower than in other parts of negative electrode layer 13.

[0026] As described above, the all-solid-state battery 100 of the first embodiment is pressed in the thickness direction. Therefore, concentrated stress is applied to the solid electrolyte layer 12 at a position that overlaps the outer periphery of the anode layer 13 in a plan view. This increases the density of the material of the solid electrolyte layer 12 (and the current density during charging and discharging) in the portion where the concentrated stress is applied, and also increases the amount of lithium ions exchanged. Therefore, a gap 132 (or an area with low lithium density) may occur in the area of ​​the outer periphery of the anode layer 13 that contacts the solid electrolyte layer 12. Note that lithium metal is likely to precipitate in areas of the solid electrolyte layer 12 that are subjected to concentrated stress (see FIG. 3 and other figures) from the anode layer 13 and where the amount of lithium ions exchanged is not zero.

[0027] On the other hand, when the all-solid-state battery 100 in a fully discharged state is charged, the lithium ions absorbed in the positive electrode layer 11 pass through the solid electrolyte layer 12 and are absorbed in the gaps 131 and 132 of the negative electrode layer 13, and both are lost.

[0028] [Manufacturing process of all-solid-state battery 100] 14A and 14B are diagrams showing a part of the manufacturing process of the all-solid-state battery 100 of the first embodiment, in which FIG. 14A is a cross-sectional view before press molding, FIG. 14B is a cross-sectional view after press molding, FIG. 14C is a plan view after press molding, and FIG. 14D is a cross-sectional view after press molding (modified example).

[0029] 14(a), in the manufacturing process of the all-solid-state battery 100, for example, a rectangular NMC811 (nickel cobalt manganese oxide lithium: positive electrode layer 11) and a rectangular frame-shaped PTFE (insulating layer 4, low ion conductive portion 14) are prepared. At this time, they are arranged so that the periphery of the NMC811 (positive electrode layer 11) and the periphery of the opening of the PTFE (insulating layer 4, low ion conductive portion 14) overlap each other in a plan view.

[0030] As shown in Figures 14(b) and 14(c), when pressed from the thickness direction, the NMC811 (positive electrode layer 11) and the PTFE (insulating layer 4, low ion conductive portion 14) become one body. In the area where the NMC811 (positive electrode layer 11) and the PTFE (insulating layer 4, low ion conductive portion 14) overlap in plan view, the NMC811 and the PTFE are mixed to form the low ion conductive portion 14.

[0031] As shown in FIG. 14(d), the low ion conductive portion 14 may be formed in such a manner that the NMC811 (positive electrode layer 11) and the PTFE (insulating layer 4, low ion conductive portion 14) are separated from each other in the area where they overlap in a planar view.

[0032] Then, the integrated body is placed on an aluminum foil (positive electrode current collector foil 2), and argyrodite (solid electrolyte layer 12), a lithium alloy (negative electrode layer 13), and a stainless steel foil (negative electrode current collector foil 3) are layered on top of the integrated body in this order, and pressed in the layering direction to form a shape.

[0033] [Amount of lithium metal deposited in all-solid-state battery 1001 of the first comparative example] FIG. 4 is a diagram showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery 1001 of the first comparative example.

[0034] The all-solid-state battery 1001 of the first comparative example does not include the low ion conductive portion 14, as compared with the all-solid-state battery 100 of the first embodiment.

[0035] 4, in the all-solid-state battery 1001 of the first comparative example, the anode layer 13 is sandwiched between the anode current collector foil 3 and the solid electrolyte layer 12. The anode layer 13 is disposed inside the outer periphery of the anode current collector foil 3 and the outer periphery of the solid electrolyte layer 12 in a plan view. The outer periphery of the anode layer 13 is disposed so as to overlap with the insulating layer 4 in a plan view.

[0036] The positive electrode layer 11 and the insulating layer 4 are sandwiched between the solid electrolyte layer 12 and the positive electrode current collector foil 2. The positive electrode layer 11 is disposed so as to be located inside the outer periphery of the negative electrode layer 13 in a plan view.

[0037] A gap 5 is formed between the positive electrode layer 11 and the insulating layer 4. Such a gap 5 occurs when the resin frame is transferred as in Patent Document 1 mentioned above.

[0038] In the all-solid-state battery 1001 of the first comparative example, when pressed from the thickness direction, a local concentrated stress A (compressive stress) is generated in the thickness direction at a position (D3) where the solid electrolyte contacts the outer periphery of the negative electrode layer 13.

[0039] Furthermore, insulating layer 4 is formed of an ultraviolet curing resin or the like as described above, and shrinks to a certain extent when cured. Therefore, in a region of solid electrolyte layer 12 that is outside the outer periphery of positive electrode layer 11 in a plan view, a stress is applied that deforms solid electrolyte layer 12 toward positive electrode current collector foil 2, centered at position (D2) where solid electrolyte layer 12 contacts the outer periphery of positive electrode layer 11, and concentrated stress B (compressive stress) is generated at position (D2) of solid electrolyte layer 12.

[0040] Here, the concentrated stress A and the concentrated stress B each have a distribution that peaks at the position overlapping the vertical dashed line in the figure, decreases with increasing distance from that position in the surface direction, and converges to zero.

[0041] In the all-solid-state battery 1001 of the first comparative example, only the positive electrode layer 11 is capable of conducting lithium ions between the solid electrolyte layer 12 and the positive electrode current collector foil 2. Therefore, the lithium ion conductivity of the all-solid-state battery 1001 of the first comparative example is a constant value (indicated as "1" in the figure) in the positive electrode layer 11 and is zero in the gap 5 and the insulating layer 4.

[0042] In the all-solid-state battery 1001, the region where lithium ions can be exchanged is the region where the anode layer 13, the solid electrolyte layer 12, and the cathode layer 11 all overlap in a planar view. In the first comparative example, lithium ions can be exchanged up to the outer periphery of the cathode layer 11. Therefore, the amount of lithium ions exchanged in the all-solid-state battery 1001 of the first comparative example is a constant value (indicated as "1" in the figure) at a position (D2) that overlaps with the outer periphery of the cathode layer 11 in a planar view or in a region inside the periphery, and is zero in a region outside the position (D2) that is the outer periphery of the cathode layer 11.

[0043] The amount of lithium metal deposited in the positive electrode layer 11 is proportional to the product of the amount of lithium ions transferred and multiplied by the concentrated stress. Therefore, the amount of lithium metal deposited in the first modification example becomes larger than zero from a position (where concentrated stress B rises) a predetermined distance inward from the position (D2) on the outer periphery of the positive electrode layer 11 toward the outer periphery of the positive electrode layer 11, reaches a peak (indicated by "1" in the figure) at the position (D2) on the outer periphery of the positive electrode layer 11, and becomes zero in a region outside the outer periphery of the positive electrode layer 11 in a plan view.

[0044] [Amount of lithium metal deposited in the all-solid-state battery 1002 of the second comparative example] FIG. 4 is a diagram showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery 1002 of the first comparative example.

[0045] The all-solid-state battery 1002 of the second comparative example does not include the low ion conductive portion 14, as in the first comparative example.

[0046] As shown in FIG. 5, in the all-solid-state battery 1002 of the second comparative example, the solid electrolyte layer 12 is disposed inside the outer periphery of the negative electrode layer 13 and the outer periphery of the positive electrode layer 11 in a plan view.

[0047] The insulating layer 4 contacts the outer periphery of the positive electrode layer 11 and protrudes onto the main surface of the positive electrode layer 11 on the side of the negative electrode layer 13, and contacts the outer periphery of the solid electrolyte layer 12 and the negative electrode layer 13. Such protrusion occurs when a resin frame is transferred as in Patent Document 1.

[0048] In the all-solid-state battery 1002 of the second comparative example, when pressed from the thickness direction, a local concentrated stress A (compressive stress) is applied in the thickness direction to the position (D3) where the insulating layer 4 comes into contact with the outer periphery of the negative electrode layer 13.

[0049] Furthermore, insulating layer 4 is formed of ultraviolet curable resin or the like as described above, and shrinks to some extent when cured. Therefore, concentrated stress B (compressive stress) that shrinks insulating layer 4 in the thickness direction is generated at the outer periphery (position (D1)) of solid electrolyte layer 12.

[0050] In the all-solid-state battery 1002 of the second comparative example, only the positive electrode layer 11 is capable of conducting lithium ions between the solid electrolyte layer 12 and the positive electrode current collector foil 2. Therefore, the lithium ion conductivity of the all-solid-state battery 1002 of the first comparative example is a constant value (indicated as "1" in the figure) in the positive electrode layer 11, and is zero in the region outside the outer periphery of the positive electrode layer 11.

[0051] In the all-solid-state battery 1002 of the second comparative example, if considered in the same manner as above, the region where lithium ions can be exchanged is a position (D1) where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view and a region inside this position (D1). Therefore, the amount of lithium ions exchanged in the all-solid-state battery 1002 of the second comparative example is a constant value (indicated as "1" in the figure) in the position (D1) of the positive electrode layer 11 where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view and a region inside this position (D1), and is zero in the region outside the position (D1) where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view.

[0052] Considering the same as above, the amount of lithium metal deposition in the second modified example becomes larger than zero from a position (position where concentrated stress B rises) that is a predetermined distance inward from a position (D1) where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view, toward the outer periphery of the positive electrode layer 11, reaches a peak (indicated as "1" in the figure) at the position (D1) where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view, and becomes zero in a region outside the position (D1) where the positive electrode layer 11 overlaps with the outer periphery of the solid electrolyte layer 12 in a planar view.

[0053] In the all-solid-state battery 1001 of the first comparative example and the all-solid-state battery 1002 of the second comparative example, concentrated stress A occurs in a region where the amount of lithium ion transfer is zero, and concentrated stress B occurs in a region where the amount of lithium ion transfer is a constant value. Therefore, in the all-solid-state battery 1001 and the all-solid-state battery 1002, precipitation of lithium metal becomes noticeable in the areas where concentrated stress B is applied.

[0054] [Amount of Lithium Metal Precipitated in the All-Solid-State Battery 100 of the First Embodiment] FIG. 3 is a diagram showing the lithium ion conductivity, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress in the all-solid-state battery 100 of the first embodiment.

[0055] 3, in the all-solid-state battery 100 of the first embodiment, the negative electrode layer 13 is sandwiched between the negative electrode current collector foil 3 and the solid electrolyte layer 12. The negative electrode layer 13 is disposed on the outer periphery of the negative electrode current collector foil 3 and inside the outer periphery of the solid electrolyte layer 12 in a plan view.

[0056] The positive electrode layer 11, the low ion-conductive portion 14, and the insulating layer 4 are sandwiched between the solid electrolyte layer 12 and the positive electrode current collector foil 2. The positive electrode layer 11 is disposed so as to be located inside the outer periphery of the negative electrode layer 13 in a plan view.

[0057] The low ion-conductive portion 14 is disposed so as to overlap the outer periphery of the negative electrode layer 13 in plan view. More specifically, the inner periphery of the low ion-conductive portion 14 is in contact with the outer periphery of the solid electrolyte layer 12 and is disposed inside the outer periphery of the negative electrode layer 13 in plan view. The outer periphery of the low ion-conductive portion 14 is in contact with the inner periphery of the insulating layer 4 and is disposed outside the outer periphery of the negative electrode layer 13 in plan view.

[0058] In the all-solid-state battery 100 of the first embodiment, when pressed in the thickness direction, a local concentrated stress A (compressive stress) is generated in the thickness direction at a position (D3) where the low ion conductive portion 14 contacts the outer periphery of the negative electrode layer 13.

[0059] Furthermore, insulating layer 4 is formed of an ultraviolet curable resin or the like as described above, and shrinks to a certain extent when cured. Therefore, at position (D4) where the boundary between low ion conductive portion 14 and insulating layer 4 overlaps in a plan view of solid electrolyte layer 12, a stress is applied that deforms the portion of solid electrolyte layer 12 on the outer periphery of position (D4) toward positive electrode layer 11, with position (D4) as the center, and concentrated stress B (compressive stress) is generated at position (D4) of solid electrolyte layer 12.

[0060] In the all-solid-state battery 100 of the first embodiment, the portions capable of conducting lithium ions between the solid electrolyte layer 12 and the positive electrode current collector foil 2 are the positive electrode layer 11 and the low ion conductive portion 14. Therefore, the lithium ion conductivity between the solid electrolyte layer 12 and the positive electrode current collector foil 2 of the first embodiment is a first predetermined value (shown as "1" in the figure) in the positive electrode layer 11, a second predetermined value (for example, "0.5") that is lower than the first predetermined value in the low ion conductive portion 14, and zero in the insulating layer 4.

[0061] In the all-solid-state battery 100 of the first embodiment, the region where lithium ions can be exchanged is a portion where the negative electrode layer 13, the solid electrolyte layer 12, and the positive electrode layer 11 or the low ion conductive portion 14 all overlap in a planar view. Therefore, the amount of lithium ions exchanged is a first predetermined value (indicated as "1" in the figure) in the positive electrode layer 11, a second predetermined value (for example, "0.5") lower than the first predetermined value in the low ion conductive portion 14 at a position (D3) where the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode current collector foil 3 in a planar view and in a region inside the position (D3), and is zero in the low ion conductive portion 14 in a region outside the outer periphery of the negative electrode current collector foil 3 in a planar view and in the insulating layer 4.

[0062] In the first embodiment, if considered in the same manner as above, the amount of lithium metal deposition in the low ion conductive portion 14 becomes larger than zero from a position (D3) at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view, which is a predetermined distance toward the inner periphery of the low ion conductor (the position where concentrated stress A rises), toward the outer periphery of the low ion conductive portion 14, reaches a peak (shown as a value lower than "1" in the figure) at the position (D3) at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view, and becomes zero in the region outside the position (D3) at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view, and in the insulating layer 4.

[0063] In the all-solid-state battery 100 of the first embodiment, concentrated stress B occurs in a region where the amount of lithium ion transfer is zero, and concentrated stress A occurs in a region where the amount of lithium ion transfer is constant. Therefore, in the all-solid-state battery 100 of the first embodiment, lithium metal precipitation occurs in the area where concentrated stress A is applied, but the position where concentrated stress A occurs is the low ion conductive portion 14, where the amount of lithium ion transfer is set lower than that of the positive electrode layer 11. Therefore, the amount of lithium metal precipitation in the first embodiment is reduced.

[0064] In the discharged state of the all-solid-state battery 100 of the first embodiment, as described above, a gap 132 is generated on the solid electrolyte layer 12 side of the outer periphery of the anode layer 13. However, since the width of the gap 132 is narrow, the anode layer 13 is not deformed, and the gap 132 may not disappear even when subjected to a pressing force in the thickness direction.

[0065] [Arrangement of low ion conductive portion 14 in first embodiment] Fig. 6 is a diagram showing a first example of an arrangement of the low ion conductive section 14 constituting the all-solid-state battery 100 of the first embodiment. Fig. 7 is a diagram showing a second example of an arrangement of the low ion conductive section 14 constituting the all-solid-state battery 100 of the first embodiment. In Figs. 6 and 7, the vertical direction indicates the circumferential direction of the low ion conductive section 14.

[0066] As shown in FIG. 6 , in a first example, the low ion conductive portion 14 is formed by uniformly distributing the material of the positive electrode layer 11 (positive electrode material 111) and the material of the insulating layer 4 (insulating material 41). The lithium ion conductivity of the low ion conductive portion 14 depends on the ratio of the positive electrode material 111 (number of moles) to the sum (number of moles) of the positive electrode material 111 and the insulating material 41. Note that the positive electrode material 111 contained in the low ion conductive portion 14 does not need to be the same as the material of the positive electrode layer 11, and the insulating material 41 contained in the low ion conductive portion 14 does not need to be the same as the material of the insulating layer 4.

[0067] 7, in a second example, low ion conductive portion 14 is formed by arranging regions occupied by the material of positive electrode layer 11 and regions occupied by insulating material 41 alternately along the circumferential direction of low ion conductive portion 14. The lithium ion conductivity in low ion conductive portion 14 varies depending on the length ratio of the region occupied by the material of positive electrode layer 11 to the region occupied by insulating material 41 in the circumferential direction of low ion conductive portion 14.

[0068] [Effects of the first embodiment] According to the all-solid-state battery 100 of the first embodiment, the all-solid-state battery 100 includes a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 containing lithium metal, and further includes a low ion-conductive portion 14 that is arranged around the outer periphery of the positive electrode layer 11 and has lower lithium ion conductivity than the positive electrode layer 11, and the low ion-conductive portion 14 overlaps the outer periphery of the negative electrode layer 13 in a planar view. More specifically, the inner periphery of the low ion-conductive portion 14 is arranged inside the outer periphery of the negative electrode layer 13 in a planar view, and the outer periphery of the low ion-conductive portion 14 is arranged outside the outer periphery of the negative electrode layer 13 in a planar view.

[0069] With the above configuration, the low ion conductive portion 14 is disposed at a stress concentration location within the region of the all-solid-state battery 100 that can exchange lithium ions. That is, stress concentration occurs at a position where the low ion conductive portion 14 contacts the outer periphery of the negative electrode layer 13 in a plan view. Furthermore, the low ion conductive portion 14 has a lower lithium ion conductivity than the solid electrolyte layer 12, and therefore exchanges fewer lithium ions. This reduces the deposition of lithium metal during discharge.

[0070] In the first embodiment, an insulating layer 4 is disposed on the outer periphery of the low ion conductive portion 14. The curing and shrinkage of the insulating layer 4 may apply concentrated stress to the low ion conductive portion 14, but the position to which the concentrated stress is applied is outside the area where lithium ions can be exchanged. Therefore, it is possible to reduce the deposition of lithium metal during discharge, which is caused by the concentrated stress generated by the curing and shrinkage of the insulating layer 4.

[0071] In the first embodiment, the low ion-conductive section 14 is a mixture of the material of the positive electrode layer 11 and the insulating material 41. This allows the low ion-conductive section 14 to be constructed with a simple configuration.

[0072] In the first embodiment, the low ion-conductive portion 14 is formed by arranging regions occupied by the material of the positive electrode layer 11 and regions occupied by the insulating material 41 alternately along the circumferential direction of the low ion-conductive portion 14. This allows the low ion-conductive portion 14 to be constructed with a simple configuration.

[0073] [Second embodiment] FIG. 8 is a diagram showing the blending ratio of the positive electrode material 111 and the insulating material 41 in the all-solid-state battery 100 of the second embodiment, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and the concentrated stress.

[0074] The all-solid-state battery 100 of the second embodiment has a configuration similar to that of the all-solid-state battery 100 of the first embodiment. The low ion-conductive portion 14 of the all-solid-state battery 100 of the second embodiment is a mixture of a positive electrode material 111 and an insulating material 41. However, in the low ion-conductive portion 14, the mixing ratio of the positive electrode material 111 (the material of the positive electrode layer 11) to the insulating material 41 is arranged so as to decrease toward the periphery of the low ion-conductive portion 14.

[0075] At the inner periphery of low ion conductive section 14, the proportion of positive electrode material 111 is nearly 100% and the proportion of insulating material 41 is nearly 0%. Furthermore, toward the outer periphery of low ion conductive section 14, the proportion of positive electrode material 111 decreases and the proportion of insulating material 41 increases. At the outer periphery of low ion conductive section 14, the proportion of positive electrode material 111 is nearly 0% and the proportion of insulating material 41 is nearly 100%.

[0076] 8, the composition ratio of the positive electrode material 111 changes continuously from the positive electrode layer 11 to the low ion conductive portion 14 and to the insulating layer 4. The composition ratio of the positive electrode material 111 is 100% (indicated as "1" in the figure) in the positive electrode layer 11, decreases as one moves from the inner periphery to the outer periphery of the low ion conductive portion 14, and becomes 0% at the outer periphery of the low ion conductive portion 14 and at the insulating layer 4. On the other hand, the composition ratio of the insulating material 41 is 0% in the positive electrode layer 11, increases as one moves from the inner periphery to the outer periphery of the low ion conductive portion 14, and becomes 100% (indicated as "1" in the figure) at the outer periphery of the low ion conductive portion 14 and at the insulating layer 4.

[0077] 8, in the fully discharged state of the all-solid-state battery 100 of the second embodiment, or in a predetermined discharged state that does not reach the fully discharged state, lithium metal disappears from the negative electrode layer 13, causing gaps 131 to form in the negative electrode layer 13. Note that, in the second embodiment, the lithium ion conductivity of the low ion conductive portion 14 at a position facing the outer periphery of the negative electrode layer 13 is lower than in the first embodiment, and therefore gaps 132 (FIGS. 2 and 3) are not formed in the outer periphery of the negative electrode layer 13.

[0078] The gaps 131 are formed almost uniformly to a predetermined depth in the region of the negative electrode layer 13 that overlaps with the positive electrode layer 11 in a plan view and in the position that overlaps with the boundary between the positive electrode layer 11 and the low ion conductive portion 14 in a plan view. Meanwhile, in the region of the gaps 131 that overlaps with the low ion conductive portion 14 in a plan view, the depth of the gaps 131 becomes shorter toward the outer periphery of the negative electrode layer 13 due to a change in the proportion of the positive electrode material 111, and the gaps disappear at a position where the proportion of the positive electrode material 111 has decreased to a predetermined proportion.

[0079] In the second embodiment, the amount of lithium ions exchanged in the solid electrolyte layer 12 is a predetermined value (shown as "1" in the figure) in the positive electrode layer 11, but decreases in the low ion conductive portion 14 toward the outer periphery of the low ion conductive portion 14, and becomes zero at a position (D3) overlapping the outer periphery of the negative electrode layer 13 in a planar view and at positions outside the position (D3).

[0080] In the second embodiment, the amount of lithium metal precipitated in the low ion conductive portion 14 becomes larger than zero from a position (D3) where the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view, which is a predetermined distance toward the inner periphery of the low ion conductive portion 14 (the position where concentrated stress A rises), toward the outer periphery of the low ion conductive portion 14, reaches a peak (shown as a value lower than "1" in the figure) at the position (D3) where the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view, and becomes zero in the region outside the position (D3) where the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 in a planar view.

[0081] In the all-solid-state battery 100 of the second embodiment, concentrated stress B occurs in a region where the amount of lithium ion transfer is zero, and concentrated stress A occurs in a region where the amount of lithium ion transfer is not zero. Therefore, in the all-solid-state battery 100 of the second embodiment, lithium metal precipitation may occur in the area where concentrated stress A is applied, but the position where concentrated stress A occurs is the low ion conductive portion 14, where the amount of lithium ion transfer is set lower than that of the positive electrode layer 11. Therefore, the amount of lithium metal precipitation in the second embodiment is reduced.

[0082] [Arrangement of low ion conductive portion 14 in second embodiment] Fig. 9 is a diagram showing a first example of an arrangement mode of the low ion conductive section 14 constituting the all-solid-state battery 100 of the second embodiment. Fig. 10 is a diagram showing a second example of an arrangement mode of the low ion conductive section 14 constituting the all-solid-state battery 100 of the second embodiment.

[0083] 9 and 10, the low ion-conductive portion 14 is a mixture of a positive electrode material 111 and an insulating material 41, and the proportion of the positive electrode material 111 decreases toward the periphery of the low ion-conductive portion 14. At the same time, the proportion of the insulating material 41 increases toward the periphery of the low ion-conductive portion 14.

[0084] In the first example shown in Figure 9, the arrangement pattern of the positive electrode material 111 and the insulating material 41 is arbitrary (random), but they are arranged so that the proportion of the positive electrode material 111 decreases and the proportion of the insulating material 41 increases toward the periphery of the low ion conductive section 14.

[0085] In the second example shown in Figure 10, the low ion conductive portion 14 is formed by a pair of region groups, each group consisting of a first region 141 occupied by a positive electrode material 111 and a second region 142 occupied by an insulating material 41, arranged along the circumferential direction of the low ion conductive portion 14.

[0086] The first region 141 has a triangular shape with its base coincident with the inner periphery of the low ion conductive section 14, and the second region 142 has a triangular shape with its base coincident with the outer periphery of the low ion conductive section 14. The first region 141 and the second region 142 are arranged such that the hypotenuse of the triangle of the first region 141 and the hypotenuse of the triangle of the second region 142 face each other.

[0087] By configuring as described above, it is possible to easily create a configuration in which the lithium ion conductivity decreases toward the periphery of low ion conductive portion 14.

[0088] [Third embodiment] 11 is a diagram showing the blending ratio of the positive electrode material 111 and the insulating material 41, the amount of lithium ions transferred, and the product of the amount of lithium ions transferred and concentrated stress in an all-solid-state battery 100 of the third embodiment. The all-solid-state battery 100 of the third embodiment is similar to the all-solid-state battery 100 of the second embodiment, but in the anode layer 13 sandwiched between the solid electrolyte layer 12 and the anode current collector foil 3, the area of ​​the main surface of the anode layer 13 that contacts the solid electrolyte layer 12 is larger than the area of ​​the main surface of the anode layer 13 that contacts the anode current collector foil 3. That is, the outer periphery of the anode layer 13 is an inclined surface that is inclined toward the anode current collector foil 3, and in a plan view, the outer periphery of the anode layer 13 on the solid electrolyte layer 12 side is disposed outside the outer periphery of the anode layer 13 on the anode current collector foil 3 side.

[0089] In the third embodiment, the solid electrolyte layer 12 receives concentrated stress A from the negative electrode layer 13 at a position (D3a) where the solid electrolyte layer 12 overlaps with the outer periphery of the negative electrode layer 13 on the negative electrode current collector foil 3 side in a plan view. However, the concentrated stress A in the third embodiment is diffused from the position (D3a) where the solid electrolyte layer 12 overlaps with the outer periphery of the negative electrode layer 13 on the negative electrode current collector foil 3 side in a plan view toward the position (D3b) where the solid electrolyte layer 12 overlaps with the outer periphery of the negative electrode layer 13, and the peak of the concentrated stress A is accordingly smaller.

[0090] Therefore, unlike the second embodiment, a gap 132 (FIG. 8) does not occur at the position (D3a) where the negative electrode layer 13 of the third embodiment overlaps with the outer periphery of the negative electrode current collector foil 3 side, or even if a gap occurs, it is smaller than in the second embodiment.

[0091] In the third embodiment, the distribution of the amount of lithium ions exchanged is similar to that in the second embodiment, but becomes zero at a position (D3b) where the solid electrolyte layer 12 overlaps with the outer periphery of the negative electrode layer 13 on the solid electrolyte layer 12 side in a plan view of the solid electrolyte layer 12.

[0092] In the third embodiment, the amount of lithium metal deposited in the solid electrolyte layer 12 becomes greater than zero from a position (D3a) in the low ion conductive portion 14 at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 on the negative electrode current collector foil 3 side in a plan view, a predetermined distance toward the inner periphery of the low ion conductive portion 14 (the position where the concentrated stress A rises), and reaches a peak (a value lower than "1" in the figure) at the position (D3a) at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 on the negative electrode current collector foil 3 side in a plan view. However, the amount of lithium metal deposited in the solid electrolyte layer 12 decreases as the area moves outward from the position (D3b) at which the low ion conductive portion 14 overlaps with the outer periphery of the negative electrode layer 13 on the solid electrolyte layer 12 side in a plan view, a predetermined distance toward the inner periphery of the low ion conductive portion 14 (the position where the concentrated stress A becomes zero).

[0093] The concentrated stress A in the all-solid-state battery 100 of the third embodiment is more dispersed than the concentrated stress A in the second embodiment, and therefore the peak is smaller, and the amount of lithium metal precipitated in the low ion conductive portion 14 is accordingly smaller.

[0094] [Fourth embodiment] 12 is a cross-sectional view of a main part of the all-solid-state battery 100 of the fourth embodiment, with the left side of the vertically extending dashed line in the figure showing a fully charged state and the right side showing a fully discharged state. The all-solid-state battery 100 of the fourth embodiment is configured so that there is no anode layer 13 in a fully discharged state (at the time of manufacture), and lithium metal is deposited as the anode layer 13 between the anode current collector foil 3 and the solid electrolyte layer 12 when the all-solid-state battery 100 is charged.

[0095] That is, the all-solid-state battery 100 of the fourth embodiment includes a power generating element 1 in which a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 are laminated, and the negative electrode layer 13 is made of lithium metal, and when the power generating element 1 is in a fully discharged state, the lithium metal is released as lithium ions toward the positive electrode layer side, so that the negative electrode layer 13 is thinner than the negative electrode layer 13 when the power generating element 1 is in a charged state, or the negative electrode layer 13 disappears. Note that when fully discharged, the negative electrode current collector foil 3 and the solid electrolyte layer 12 are in contact with each other.

[0096] In the fourth embodiment, the low ion conductive portion 14 is arranged so that its inner periphery is located inside the outer periphery of the positive electrode current collector foil 2 in a plan view, and its outer periphery is located inside the outer periphery of the positive electrode current collector foil 2.

[0097] As a result, the negative electrode layer 13 is disposed so that its outer periphery overlaps the outer periphery of the positive electrode current collector foil 2. Furthermore, the negative electrode layer 13 is disposed so that its inner periphery is located inside the outer periphery of the low ion conductive portion 14 in a plan view, and its outer periphery is located inside the outer periphery of the low ion conductive portion 14. In this way, the all-solid-state battery 100 in which the thickness of the negative electrode layer 13 varies can also achieve the same effects as those of the first embodiment and the like.

[0098] Furthermore, as a modified example of the all-solid-state battery 100 of the fourth embodiment, a configuration can be adopted in which a lithium metal anode layer 13 is disposed between the anode current collector foil 3 and the solid electrolyte layer 12, and the all-solid-state battery 100 is charged to cause lithium ions that have migrated from the positive electrode layer 11 to accumulate as lithium metal in the anode layer 13, thereby increasing the thickness of the anode layer 13.

[0099] [Fifth embodiment] 13 is a cross-sectional view of a main part of an all-solid-state battery 100 according to the fifth embodiment. The all-solid-state battery 100 according to the fifth embodiment is similar to that according to the fourth embodiment, but the low ion conductive portion 14 is configured such that the ratio of the positive electrode material 111 and the insulating material 41 varies, as in the second and third embodiments.

[0100] As a result, when the all-solid-state battery 100 of the fifth embodiment is charged, the amount of lithium metal deposited in the region between the negative electrode current collector foil 3 and the solid electrolyte layer 12 (the region where the negative electrode layer 13 is formed) that overlaps with the low ion conductive portion 14 in a planar view decreases toward the outer periphery of the low ion conductive portion 14 in a planar view, and becomes zero at a position along the way.

[0101] Therefore, as shown in FIG. 13 , when the all-solid-state battery 100 is charged, the anode layer 13 is deposited, and the outer periphery of the anode layer 13 forms an inclined surface that is inclined toward the anode current collector foil 3, and the anode layer 13 is deposited such that the area of ​​the main surface of the anode layer 13 on the solid electrolyte layer 12 side is larger than the area of ​​the main surface of the anode layer 13 on the anode current collector foil 3 side.

[0102] Therefore, similarly to the third embodiment, the concentrated stress A is diffused, and therefore deposition of lithium metal in the low ion conductive portion 14 during discharge can be suppressed.

[0103] Furthermore, in the all-solid-state battery 100 of the fifth embodiment, the insulating layer 4 is made of the same material as the solid electrolyte layer 12 and is formed integrally with the solid electrolyte layer 12. This makes it possible to avoid the occurrence of stress (concentrated stress B, see FIG. 11 ) due to contraction of the insulating layer 4 and the like. In particular, when the stress is large, the stress may extend to the region where concentrated stress A occurs, which may cause lithium metal to precipitate in the low ion conductive portion 14, but this can also be avoided. [Explanation of symbols]

[0104] 100 all-solid-state battery, 1 power generation element part, 11 positive electrode layer, 12 solid electrolyte, 13 negative electrode layer, 14 low ionic conductivity part, 2 positive electrode current collecting foil, 3 negative electrode current collecting foil, 4 elastic layer

Claims

1. An all-solid-state battery including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing lithium metal, a low ion conductive portion that is disposed around the outer periphery of the positive electrode layer and in close contact with the positive electrode layer, and has a lithium ion conductivity lower than that of the positive electrode layer; The low ion conductive portion overlaps the outer periphery of the negative electrode layer in a plan view, and a region occupied by a material of the positive electrode layer and a region occupied by an insulating material are alternately arranged along the circumferential direction of the low ion conductive portion to form an all-solid-state battery.

2. An all-solid-state battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing lithium metal, a low ion conductive portion that is disposed around the outer periphery of the positive electrode layer and in close contact with the positive electrode layer, and has a lithium ion conductivity lower than that of the positive electrode layer; the low ion conductive portion overlaps an outer periphery of the negative electrode layer in a plan view, and is formed by a pair of region groups, each of which includes a first region occupied by a material of the positive electrode layer and a second region occupied by an insulating material, being arranged along a circumferential direction of the low ion conductive portion; the first region has a triangular shape with the inner periphery of the low ionic conductivity portion as its base, the second region has a triangular shape with the outer periphery of the low ionic conductivity portion as its base, The first region and the second region are an oblique side of the triangle of the first region and an oblique side of the triangle of the second region are arranged to face each other.

3. 3. The all-solid-state battery according to claim 1, wherein an inner periphery of the low ion conductive portion is disposed inside an outer periphery of the negative electrode layer in a planar view, and an outer periphery of the low ion conductive portion is disposed outside an outer periphery of the negative electrode layer in a planar view.

4. The all-solid-state battery according to claim 1 , wherein an insulating layer is disposed on an outer periphery of the low ion conductive portion.

5. The all-solid-state battery according to claim 4 , wherein the insulating layer is formed from the material of the solid electrolyte layer.

6. The all-solid-state battery according to claim 1 , wherein the low ion-conductive portion is a mixture of a material of the positive electrode layer and an insulating material.

7. In the low ion conductive portion, the blending ratio of the material of the positive electrode layer to the insulating material is The all-solid-state battery according to claim 6 , wherein the low ion conductive portions are arranged so as to decrease in thickness toward the periphery.

8. the negative electrode layer is sandwiched between the solid electrolyte layer and a negative electrode current collector foil, 8. The all-solid-state battery according to claim 1, wherein an area of ​​a main surface of the negative electrode layer in contact with the solid electrolyte layer is larger than an area of ​​a main surface of the negative electrode layer in contact with the negative electrode current collector foil.

9. a power generating element part in which the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are stacked, 9. The all-solid-state battery according to claim 1, wherein the negative electrode layer is formed of the lithium metal, and when the power-generating element unit is in a fully discharged state, the lithium metal is released to the positive electrode layer side, thereby making the negative electrode layer thinner than the negative electrode layer when the power-generating element unit is in a charged state, or the negative electrode layer disappears.

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