Secondary battery

Abstract

This secondary battery is provided with: a battery element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer; and an insulating elastic member disposed so as to surround a side surface of the battery element. The battery element and the insulating elastic member are pressed so as to be compressed in the lamination direction. A notch is provided on the outer peripheral surface of the insulating elastic member.

Description

secondary battery

[0001] The present invention relates to a secondary battery.

[0002] Known secondary batteries have a structure in which a negative electrode current collector foil, a negative electrode layer, a solid electrolyte layer, a positive electrode layer, and a positive electrode current collector foil are stacked in this order. In this specification, the stacked structure consisting of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer is sometimes referred to as a battery element.

[0003] In such secondary batteries, a frame material may be disposed so as to surround the side surfaces of the battery element for various reasons.

[0004] For example, Patent Document 1 (JP2018-116812A) discloses a "method for manufacturing an all-solid-state lithium-ion battery, the method comprising: a first step of stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer to form a stacked battery having both end surfaces and side surfaces in the stacking direction; a second step of charging the stacked battery to a charge rate of 100% or more and 112% or less; a third step of covering at least the side surfaces of the charged stacked battery with an uncured thermosetting resin; and a fourth step of heating and curing the thermosetting resin." According to the description in Patent Document 1, this manufacturing method is capable of suppressing cracking of the cured resin due to expansion of the negative electrode during charging, even when discharge and charge are repeated.

[0005] On the other hand, in secondary batteries using a solid electrolyte layer, an extremely large restraining load is applied to obtain desired charge / discharge characteristics. The restraining load is also applied to the frame material. As a result, the frame material may be damaged by compressive stress.

[0006] Therefore, an object of the present invention is to provide a technique capable of preventing damage to a frame material due to a restraining load in a secondary battery having a configuration in which a battery element is surrounded by a frame material.

[0007] In one aspect, the secondary battery according to the present invention is a battery element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer, the positive electrode layer and the negative electrode layer being arranged to sandwich the solid electrolyte layer in the stacking direction, and an insulating elastic member being arranged to surround the side surface of the battery element. The battery element and the insulating elastic member are pressurized so as to be compressed in the stacking direction. A notch is provided on the outer peripheral surface of the insulating elastic member.

[0008] Fig. 1 is a schematic cross-sectional view showing a secondary battery according to an embodiment. Fig. 2 is a schematic cross-sectional view showing an enlarged view of the configuration of an end portion of a battery element. Fig. 3 is a schematic cross-sectional view showing the configuration of a secondary battery during charging and discharging. Fig. 4 is a schematic plan view showing a preferred embodiment in which a notch is provided on the side of a positive electrode current collector foil. Fig. 5 is a schematic cross-sectional view showing an example of the shape of the notch.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] 1 is a schematic cross-sectional view showing a secondary battery 1 according to an embodiment. The secondary battery 1 according to this embodiment is a secondary battery using a solid electrolyte layer as an electrolyte layer. The secondary battery 1 according to this embodiment includes so-called all-solid-state batteries.

[0011] 1 , the secondary battery 1 includes battery elements 2 (2-1 to 2-6), a positive electrode current collector foil 8, a negative electrode current collector foil 9, and an insulating elastic member 6. The battery element 2 is sandwiched between the positive electrode current collector foil 8 and the negative electrode current collector foil 9 in the stacking direction. The side surfaces of the battery element 2 are surrounded by the insulating elastic member 6.

[0012] In the example shown in Fig. 1, a plurality of battery elements 2, positive electrode current collector foils 8, and negative electrode current collector foils 9 are provided. That is, a plurality of battery elements 2 (2-1 to 2-6) are stacked with the respective current collector foils (8 and 9) interposed therebetween. However, it is not necessary to provide a plurality of these. A single battery element 2, positive electrode current collector foil 8, and negative electrode current collector foil 9 may each be provided.

[0013] The secondary battery 1 is pressurized so as to be compressed in the stacking direction. For example, although not shown, a pair of end plates are arranged on both sides of the configuration shown in Fig. 1 in the stacking direction. A restraining load is applied to the battery element 2 and the insulating elastic member 6 along the stacking direction via the pair of end plates. The magnitude of the restraining load is, for example, 0.5 MPa or more, preferably 1 MPa or more.

[0014] The battery element 2 is configured to function as a battery. The battery element 2 has a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5. The positive electrode layer 4 and the negative electrode layer 5 are arranged to sandwich the solid electrolyte layer 3 in the stacking direction. The battery element 2 is arranged between the positive electrode current collector foil 8 and the negative electrode current collector foil 9 so that the positive electrode layer 4 faces the positive electrode current collector foil 8 side and the negative electrode layer 5 faces the negative electrode current collector foil 9 side.

[0015] 1, the outer peripheral edges of the solid electrolyte layer 3 and the negative electrode layer 5 are located outside the outer peripheral edge of the positive electrode layer 4 when viewed along the stacking direction. However, the positional relationship of the outer peripheral edges of the layers is not limited to this.

[0016] The battery element 2 is configured so that the thickness of the negative electrode layer 5 increases during charging and decreases during discharging. Since the negative electrode layer 5 expands and contracts, the entire battery element 2 also expands and contracts during charging and discharging.

[0017] The positive electrode current collector foil 8 and the negative electrode current collector foil 9 are provided to electrically connect the battery element 2 to an external device. Each current collector foil (8 and 9) extends laterally from the connection portion with the battery element 2. Although not shown, each current collector foil is gathered at the end opposite the battery element 2 and connected to a tab. The positive electrode current collector foil 8 and the negative electrode current collector foil 9 extend from the battery element 2 toward opposite sides.

[0018] The insulating elastic member 6 is, as its name suggests, an insulating and elastic body, and covers the side surfaces of the battery element 2 without leaving any gaps.

[0019] One of the roles of the insulating elastic member 6 is to apply pressure uniformly to the battery element 2. The positions of the layers constituting the battery element 2 may shift when stacked. Such positional shifts or the like may result in unevenness on the side surface of the battery element 2. If unevenness is formed, it becomes difficult to apply a sufficient load to the side surface of the battery element 2. In other words, it becomes difficult to apply a uniform load to the battery element 2. However, by arranging the insulating elastic member 6, it is possible to absorb the unevenness. Therefore, it is possible to apply a uniform load to the battery element 2.

[0020] In this embodiment, a notch 7 is provided on the outer peripheral surface of the insulating elastic member 6. The notch 7 extends from the outer peripheral surface toward the inside (toward the battery element 2).

[0021] In this specification, the term "notch" is a term that specifies the "shape" of the insulating elastic member 6, but does not specify the method for forming the shape. In other words, the notch 7 is not limited to a shape that can be obtained by first molding the insulating elastic member 6 in a shape without the notch 7 and then "cutting" the outer periphery of the molded insulating elastic member 6. For example, the notch 7 may be formed simultaneously with molding the insulating elastic member 6 by using a mold having a shape corresponding to the notch 7.

[0022] According to this embodiment, the provision of the notches 7 prevents damage to the insulating elastic member 6. This will be described below with reference to FIG.

[0023] FIG. 2 is a schematic cross-sectional view showing an enlarged view of the configuration at the end of the battery element 2. FIG. 2 shows the configuration before and after the application of a restraint load. FIG. 2(a) shows the configuration before the application of the restraint load. That is, the configuration in a state where no external force is applied is shown. On the other hand, FIG. 2(b) shows the configuration after the application of the restraint load. As shown in FIG. 2, when a restraint load is applied in the stacking direction, the insulating elastic member 6 is compressed and the notch 7 is crushed. At this time, the compressive stress generated in the insulating elastic member 6 is relieved at the notch 7. Therefore, even when an extremely large restraint load is applied to the frame material (insulating elastic member 6), damage to the insulating elastic member 6 is prevented.

[0024] Furthermore, according to this embodiment, since the insulating elastic member 6 is an elastic body, expansion and contraction of the battery element 2 during charging and discharging is permitted even when the expansion and contraction amount of the battery element 2 is particularly large. This point will be explained with reference to FIG. 3 . FIG. 3 is a schematic cross-sectional view showing the configuration of the secondary battery 1 during charging and discharging. FIG. 3( a ) shows the configuration in the discharging state. FIG. 3( b ) shows the configuration in the charging state. As described above, during charging, the negative electrode layer 5 thickens and the battery element 2 expands. As the battery element 2 expands, the frame material surrounding the battery element 2 is also pulled in the stacking direction. That is, tensile stress is generated in the frame material. Here, if the frame material surrounding the battery element 2 were made of a hard material (e.g., a thermosetting resin), the frame material would not follow the expansion of the battery element 2. As a result, the tensile stress could crack the frame material. However, according to this embodiment, the frame material is an elastic body (insulating elastic member 6). Therefore, the insulating elastic member 6 can expand and contract in response to the expansion of the battery element 2. Even if the battery element 2 expands, the insulating elastic member 6 follows the battery element 2 and does not break.

[0025] Furthermore, the incisions 7 do not divide the insulating elastic member 6. If the insulating elastic member 6 were divided in the stacking direction, the function required of the insulating elastic member 6, such as applying a load uniformly to the battery element 2, may be impaired. However, since the incisions 7 do not divide the insulating elastic member 6, the function of applying a load uniformly to the battery element 2 is maintained.

[0026] The above is an outline of this embodiment. Next, each component included in the secondary battery 1 will be described in detail.

[0027] (Insulating Elastic Member) The insulating elastic member 6 may be any member that has insulating properties and is an elastic body. For example, a member made of resin can be used as the insulating elastic member 6. Examples of such insulating elastic members 6 include those made of rubber and elastomer resin, polyethylene resin, polypropylene resin, epoxy resin, ethylene copolymer, propylene copolymer, etc. The elastic modulus of the insulating elastic member is, for example, 20 MPa or less, preferably 10 MPa or less. The width of the insulating elastic member is, for example, 0.3 to 2 cm, preferably 0.5 to 1.5 cm.

[0028] (Notches) As described above, the notches 7 are provided on the outer peripheral surface of the insulating elastic member 6 .

[0029] The notch 7 may be provided at any position in the stacking direction. However, the notch 7 is preferably provided at a position different from the portion surrounding the negative electrode layer 5. In other words, the notch 7 is provided at a position that does not overlap with the negative electrode layer 5 when viewed from the side. The portion of the insulating elastic member 6 that stretches in response to the expansion of the negative electrode layer 5 is the portion surrounding the negative electrode layer 5. If the notch 7 is provided in such a portion, the insulating elastic member 6 is likely to break when the negative electrode layer 5 expands. In contrast, if the notch 7 is provided at a position different from the position surrounding the negative electrode layer 5, the insulating elastic member 6 is less likely to break even if the negative electrode layer 5 expands.

[0030] In the example shown in FIG. 1 , the notch 7 is provided on a side of the positive current collector foil 8. In other words, the notch 7 is provided on the same plane as the positive current collector foil 8. Specifically, in the example shown in FIG. 1 , multiple battery elements 2 (2-1 to 2-6) are provided. More specifically, the secondary battery 1 includes at least a pair of battery elements 2 that sandwich the positive current collector foil 8 in the stacking direction (for example, note the relationship between battery element 2-1 and battery element 2-2). Here, when viewed along the stacking direction, the outer peripheral edge of the positive current collector foil 8 is located inside the insulating elastic member 6, except for the portion extending toward the tab. The insulating elastic member 6 continuously covers the side surfaces of the multiple battery elements 2 outside the outer peripheral edge of the positive current collector foil 8. In other words, the outer peripheral edge of the positive current collector foil 8 is covered by the insulating elastic member 6, except for the portion extending toward the tab. The notch 7 is provided in a position that covers the outer peripheral edge of the positive current collector foil 8. Such a position is the farthest position from the negative electrode layer 5. If the notch 7 is provided at the position farthest from the negative electrode layer 5, the strength of the position surrounding the negative electrode layer 5 is less likely to be impaired. Therefore, even if the negative electrode layer 5 expands, the insulating elastic member 6 is less likely to break.

[0031] On the other hand, the notch 7 may be provided on the side of the positive electrode layer 4. That is, the notch 7 may be provided in a position surrounding the positive electrode layer 4. In this case, the insulating elastic member 6 is less likely to break due to the expansion of the negative electrode layer 5, compared to when the notch 7 is provided in a portion surrounding the negative electrode layer 5.

[0032] Next, the shape of the notch 7 when viewed along the stacking direction will be described. The notch 7 is preferably provided continuously in the circumferential direction. FIG. 4 is a schematic plan view showing a preferred embodiment of the notch 7. The example shown in FIG. 4 illustrates a case in which the notch 7 is provided on the side of the positive current collector foil 8. FIG. 4 shows the positional relationship between the battery element 2, the positive current collector foil 8, the insulating elastic member 6, and the notch 7. As shown in FIG. 4, the positive current collector foil 8 has a positive electrode connection portion 8-1 and a positive electrode tab extension portion 8-2. The positive electrode connection portion 8-1 is a portion connected to the positive electrode layer of the battery element 2. The positive electrode tab extension portion 8-2 is a portion extending laterally from the positive electrode connection portion 8-1 toward the tab (not shown). The positive electrode tab extension portion 8-2 extends through the insulating elastic member 6. Here, the notch 7 is provided continuously at a position surrounding the positive electrode current collector foil 8 in the circumferential direction, excluding the positive electrode tab extension portion 8-2. Note that "provided continuously" means that the notch 7 is provided without any breaks.

[0033] 4, the insulating elastic member 6 has a rectangular shape when viewed along the stacking direction. The positive electrode current collector foil 8 also has a rectangular shape. When viewed along the stacking direction, the positive electrode tab extension 8-2 protrudes laterally from one of the four sides of the insulating elastic member 6. The notch 7 is provided continuously along three sides excluding the side from which the positive electrode tab extension 8-2 protrudes.

[0034] As described above, if the notches 7 are provided continuously in the circumferential direction, it becomes more difficult for compressive stress to concentrate in any part, thereby more reliably preventing damage to the insulating elastic member 6 due to the restraining load.

[0035] In the example shown in FIG. 4 , the notch 7 is provided on the same plane as the positive electrode current collector foil 8. Therefore, the notch 7 cannot be provided in the portion where the positive electrode tab extension portion 8-2 is present. In contrast, if the notch 7 is provided on a different plane from the current collector foil (8, 9) (for example, if the notch 7 is provided on the side of the positive electrode layer 4), the notch 7 can be provided so as to continuously surround the entire periphery of the battery element 2. By adopting such a configuration, damage to the insulating elastic member 6 due to the restraint load can be more reliably prevented.

[0036] Next, we will explain a suitable cross-sectional shape of the notch 7. As shown in Fig. 2(a), the notch 7 is preferably V-shaped in cross section when no external force is applied.

[0037] If the notches 7 are V-shaped, breakage of the insulating elastic member 6 due to the restraint load is more reliably prevented. As described above, a restraint load is applied to the insulating elastic member 6. As a result, the insulating elastic member 6 is compressed so that the space formed by the notches 7 disappears, as shown in FIG. 2( b). If the notches 7 were rectangular or similar in cross section, a space might remain in the notches 7 even after the restraint load is applied. In such cases, a concentrated portion of compressive stress is likely to occur. As a result, the insulating elastic member 6 is more likely to break. In contrast, if the notches 7 are V-shaped, no space remains after the restraint load is applied. This makes it less likely that a concentrated portion of compressive stress will occur, and breakage of the insulating elastic member 6 is more reliably prevented.

[0038] The notch 7 preferably has a certain depth from the viewpoint of effectively alleviating compressive stress. FIG. 5 is a schematic cross-sectional view showing a preferred example of the notch 7. In the example shown in FIG. 5, the outer end (end A) of the solid electrolyte layer 3 is located outward from the outer ends of the positive electrode layer 4 and the positive current collector foil 8 when viewed along the stacking direction. The notch 7 is provided at a position different from the solid electrolyte layer 3 when viewed from the side. Specifically, the notch 7 is provided on the side of the positive electrode current collector foil 8. When viewed along the stacking direction, the inner end (see end B in FIG. 5) of the notch 7 is located more inward than the outer end (see end A in FIG. 5) of the solid electrolyte layer 3. If the notch 7 is provided to such a depth, damage due to compressive stress can be more reliably prevented.

[0039] For example, the depth of the notch 7 is 20% or more, preferably 50% or more, of the width of the insulating elastic member 6 (the width at the portion where the notch 7 is provided).

[0040] (Battery Element) Next, the battery element 2 will be described. As described above, the secondary battery 1 according to this embodiment is configured to allow large expansion and contraction of the battery element 2. Therefore, this embodiment is particularly valuable for secondary batteries 1 in which the amount of expansion and contraction of the battery element 2 due to charging and discharging is particularly large.

[0041] As described above, an example of a secondary battery that expands and contracts significantly during charging and discharging is a Li-precipitation-type all-solid-state battery. That is, the battery element 2 is preferably configured so that metallic lithium is deposited in the anode layer 5 during charging. In a Li-precipitation-type all-solid-state battery, lithium ions migrate from the cathode layer 4 to the anode layer 5 via the solid electrolyte layer 3 during charging. The lithium ions that migrate to the anode layer 5 are deposited as metallic lithium. The deposited metallic lithium functions as the anode active material. On the other hand, during discharging, the metallic lithium contained in the anode layer 5 migrates as lithium ions to the cathode layer 4 and is absorbed by the cathode layer 4. The deposition and disappearance of metallic lithium in the anode layer 5 is repeated during charging and discharging. Therefore, the expansion and contraction of the battery element 2 during charging and discharging is larger than that of other secondary batteries. However, according to this embodiment, even when the expansion and contraction of the battery element 2 is particularly large, as in a Li-precipitation-type all-solid-state battery, expansion and contraction during charging and discharging can be tolerated.

[0042] (Negative Electrode Layer) The negative electrode layer may be any layer configured to accept lithium during charging and release lithium during discharging.

[0043] In addition, when the secondary battery 1 is a Li-precipitation type all-solid-state battery, metallic lithium may not be present on the negative electrode side as a negative electrode active material in a fully discharged state. However, even in such a type of battery, metallic lithium precipitated on the negative electrode side during charging can be said to function as a negative electrode layer, and therefore the secondary battery 1 according to this embodiment is included.

[0044] The negative electrode layer may include a negative electrode intermediate layer. The negative electrode intermediate layer is a layer provided in a Li-precipitation-type all-solid-state battery for purposes such as protecting the solid electrolyte layer. In a Li-precipitation-type all-solid-state battery, the deposited metallic lithium functions as the negative electrode active material. However, if the deposited metallic lithium comes into direct contact with the solid electrolyte layer, the solid electrolyte layer may be damaged. Therefore, a negative electrode intermediate layer is provided between the solid electrolyte layer and the negative electrode current collector foil. The metallic lithium is deposited between the negative electrode intermediate layer and the negative electrode current collector foil. The presence of the negative electrode intermediate layer protects the solid electrolyte layer from the metallic lithium. Furthermore, the provision of the negative electrode intermediate layer can also control the location of metallic lithium deposition. A negative electrode intermediate layer used for such purposes is also included in the negative electrode layer in this embodiment. In a Li-precipitation-type all-solid-state battery having a negative electrode intermediate layer, metallic lithium is hardly present on the negative electrode side in a discharged state. Therefore, it can be said that the negative electrode layer is composed of the negative electrode intermediate layer in a discharged state. On the other hand, in a charged state, metallic lithium is present between the negative electrode intermediate layer and the negative electrode current collector foil, and in a charged state, the layer containing the negative electrode intermediate layer and the deposited metallic lithium can be said to be the negative electrode layer.

[0045] The negative electrode intermediate layer can be realized by, for example, a layer containing metal particles such as silver particles, carbon particles, and a binder resin.

[0046] (Solid Electrolyte Layer) The solid electrolyte layer is solid and may be made of any material as long as it functions as an electrolyte layer in a secondary battery. The solid electrolyte layer may include, for example, a resin binder and a solid electrolyte dispersed in the resin binder. The solid electrolyte preferably includes a sulfide solid electrolyte. The thickness of the solid electrolyte layer is, for example, 5 to 100 μm.

[0047] (Positive Electrode Layer) The positive electrode layer may be formed of a material that can release lithium ions during charging and absorb lithium ions during discharging. The positive electrode layer may be formed of a material containing, for example, a resin binder and a positive electrode active material dispersed in the resin binder. For example, a lithium metal composite oxide may be used as the positive electrode active material. For example, the lithium metal composite oxide may be LiCoO ２ , LiMnO ２, LiNiO ２ , LiVO ２ , and Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ , and LiNi ０．５ Mn １．５ O ４ spinel-type compounds such as LiFePO ４ , and LiMnPO ４ Olivine type compounds such as Li ２ FeSiO ４ , and Li ２ MnSiO ４ In addition, Si-containing compounds such as Li ４ Ti ５ O １２ The thickness of the positive electrode layer is, for example, 10 to 500 μm, and preferably 50 to 200 μm.

[0048] (Negative electrode current collector foil and positive electrode current collector foil) The negative electrode current collector foil and positive electrode current collector foil are not particularly limited. For example, the negative electrode current collector foil may be a thin film of copper, a copper alloy, nickel, a nickel alloy, or the like. The positive electrode current collector foil may be, for example, an aluminum foil.

[0049] [Supplementary Note] The embodiments of the present invention have been described above. Next, the main aspects and effects of the present invention will be summarized as supplementary notes.

[0050] (Supplementary Note 1) A secondary battery comprising: a battery element 2 having a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5, the positive electrode layer 4 and the negative electrode layer 5 being arranged so as to sandwich the solid electrolyte layer 3 in the stacking direction; and an insulating elastic member 6 being arranged so as to surround a side surface of the battery element 2, the battery element 2 and the insulating elastic member 6 being pressurized so as to be compressed in the stacking direction, and a notch 7 being provided on the outer peripheral surface of the insulating elastic member 6.

[0051] With this configuration, the frame material surrounding the battery element 2 is the insulating elastic member 6, which is an elastic body, so the frame material is less likely to break even when the battery element 2 expands and contracts particularly greatly. Furthermore, because the notches 7 are provided, compressive stress is alleviated even when a large restraining load is applied to the insulating elastic member 6, which is the frame material. Therefore, damage to the insulating elastic member 6 due to the restraining load is also prevented.

[0052] (Supplementary Note 2) The secondary battery according to Supplementary Note 1, wherein the battery element 2 is configured so that metallic lithium is deposited on the negative electrode layer 5 during charging.

[0053] In a secondary battery having such a configuration, the battery element 2 expands and contracts particularly greatly during charging and discharging, and therefore it is highly valuable to employ a configuration that allows for large expansion and contraction.

[0054] (Supplementary Note 3) The secondary battery according to Supplementary Note 1 or 2, wherein the notch 7 is provided on a side of the positive electrode layer 4.

[0055] With this configuration, there is no need to provide the notch 7 at a position surrounding the negative electrode layer 5, and therefore the insulating elastic member 6 is less likely to break when the negative electrode layer 5 expands.

[0056] (Appendix 4) The secondary battery according to any one of Appendices 1 to 3, further comprising a positive electrode current collector foil 8 connected to the positive electrode layer 4, at least a pair of battery elements 2 is provided, the pair of battery elements 2 are arranged to sandwich the positive electrode current collector foil 8 in the stacking direction, the insulating elastic member 6 continuously covers the side surfaces of the pair of battery elements 2 outside the outer peripheral edge of the positive electrode current collector foil 8, and the notch 7 is provided on the side of the positive electrode current collector foil 8.

[0057] With this configuration, there is no need to provide the notch 7 at a position surrounding the negative electrode layer 5, and therefore the insulating elastic member 6 is less likely to break when the negative electrode layer 5 expands.

[0058] (Supplementary Note 5) The secondary battery according to Supplementary Note 4, wherein the positive electrode current collector foil 8 has a positive electrode connection portion 8-1 that is a portion connected to the positive electrode layer 4, and a positive electrode tab extension portion 8-2 that extends laterally from the positive electrode connection portion 8-1 toward the tab, the positive electrode tab extension portion 8-2 extends through the insulating elastic member 6, and the notches 7 are provided continuously at positions that surround the positive electrode current collector foil 8 in the circumferential direction, excluding the positive electrode tab extension portion 8-2.

[0059] With this configuration, the notches 7 are provided continuously, which further reduces the compressive stress that occurs in the insulating elastic member 6 when a restraining load is applied, thereby more reliably preventing the insulating elastic member 6 from breaking.

[0060] (Appendix 6) A secondary battery according to any one of Appendices 1 to 5, wherein the insulating elastic member 6 is compressed in the stacking direction so that the space formed by the notch 7 disappears, and the notch 7 has a V-shape in cross section when no external force is applied to the insulating elastic member 6.

[0061] With this configuration, compressive stress when a restraining load is applied is more easily alleviated, thereby more reliably preventing the insulating elastic member 6 from breaking.

[0062] (Appendix 7) The secondary battery according to any one of Appendices 1 to 6, wherein the notch 7 is provided at a position different from the solid electrolyte layer 3 when viewed from the side, and an inner end of the notch 7 is located more inward than an outer peripheral end of the solid electrolyte layer 3 when viewed along the stacking direction.

[0063] With this configuration, the depth of the notches 7 is ensured to a certain extent, which makes it easier to alleviate the compressive stress when a restraining load is applied, thereby more reliably preventing the insulating elastic member 6 from breaking.

Claims

1. A secondary battery comprising: a battery element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer, the positive electrode layer and the negative electrode layer being arranged so as to sandwich the solid electrolyte layer in the stacking direction; and an insulating elastic member being arranged so as to surround a side surface of the battery element, the battery element and the insulating elastic member being pressurized so as to be compressed in the stacking direction, and a notch being provided on the outer peripheral surface of the insulating elastic member.

2. A secondary battery according to claim 1, wherein the battery element is configured so that metallic lithium is deposited on the negative electrode layer during charging.

3. A secondary battery according to claim 1 or 2, wherein the cut is provided on a side of the positive electrode layer.

4. A secondary battery as defined in claim 1 or 2, further comprising a positive electrode current collector foil connected to the positive electrode layer, at least one pair of battery elements being provided so as to sandwich the positive electrode current collector foil in the stacking direction, the insulating elastic member continuously covering the side surfaces of the pair of battery elements outside the outer peripheral edge of the positive electrode current collector foil, and the notch being provided on the side of the positive electrode current collector foil.

5. A secondary battery as claimed in claim 4, wherein the positive electrode current collector foil has a positive electrode connection portion which is connected to the positive electrode layer, and a positive electrode tab extension portion which extends laterally from the positive electrode connection portion towards a tab, the positive electrode tab extension portion extending through the insulating elastic member, and the cuts are provided continuously at positions which surround the positive electrode current collector foil in the circumferential direction, excluding the positive electrode tab extension portion.

6. A secondary battery according to claim 1 or 2, wherein the insulating elastic member is compressed in the stacking direction so that the space formed by the notch disappears, and the notch has a V-shape in cross section when no external force is applied to the insulating elastic member.

7. A secondary battery according to claim 1 or 2, wherein the notch is provided at a position different from that of the solid electrolyte layer when viewed from the side, and the inner end of the notch is located more inward than the outer peripheral edge of the solid electrolyte layer when viewed along the stacking direction.

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