Secondary battery

Abstract

This secondary battery comprises: a negative electrode current collector foil; a positive electrode current collector foil; a battery element; and an insulating elastic member disposed to surround the battery element. The battery element has a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. The insulating elastic member has a base portion located next to the positive electrode layer, and a wide portion provided closer to the negative electrode current collector foil than the base portion. The width of the wide portion is greater than the width of the base portion.

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. The stacked structure consisting of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer is referred to as a battery element in this specification. Among such secondary batteries, those having a structure in which the side surfaces of the battery element are covered with a protective material such as resin are known.

[0003] In relation to the above, for example, Patent Document 1 (WO2020 / 137388A) discloses an all-solid-state battery including an electrode layer, a solid electrolyte layer containing a solid electrolyte, and a sealing layer containing a sealing material, wherein at least one of the electrode layer and the solid electrolyte layer contains a binder, and the glass transition temperature of the sealing material is higher than the glass transition temperature of the binder.

[0004] Battery elements may expand and contract during charging and discharging. For example, a known secondary battery is one configured so that metallic lithium is deposited on the negative electrode layer during charging. In such secondary batteries, the negative electrode layer expands significantly during charging. Conversely, the negative electrode layer contracts during discharging. In secondary batteries configured so that the battery elements are covered with a protective material, the expansion and contraction of the battery elements during charging and discharging can damage the protective material. Therefore, there is a need for a technology that can prevent damage to the protective material.

[0005] That is, an object of the present invention is to provide a secondary battery capable of preventing damage to a protective material caused by charging and discharging.

[0006] In one aspect, a secondary battery according to the present invention includes a negative electrode current collector foil, a positive electrode current collector foil, a battery element disposed between the positive electrode current collector foil and the negative electrode current collector foil in the stacking direction, and an insulating elastic member disposed so as to surround the battery element. The battery element includes a positive electrode layer connected to the positive electrode current collector foil, a negative electrode layer connected to the negative electrode current collector foil, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The insulating elastic member includes a base portion located on a side of the positive electrode layer and a wide portion provided closer to the negative electrode current collector foil than the base portion. The width of the wide portion is greater than the width of the base portion.

[0007] FIG. 1 is a schematic cross-sectional view showing a secondary battery according to a first embodiment. FIG. 2 is a cross-sectional view showing an enlarged view of a portion of the configuration of the secondary battery. FIG. 3A is a schematic cross-sectional view showing a secondary battery according to a reference example. FIG. 3B is a schematic cross-sectional view showing the configuration of the secondary battery according to the first embodiment during charging and discharging. FIG. 4 is a schematic cross-sectional view showing a modified example of the first embodiment. FIG. 5 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a second embodiment. FIG. 6 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a third embodiment. FIG. 7 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a fourth embodiment. FIG. 8 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a fifth embodiment. FIG. 9 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a sixth embodiment. FIG. 10 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to a seventh embodiment.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (1) First Embodiment Fig. 1 is a schematic cross-sectional view showing a secondary battery 1 according to a first embodiment. Fig. 2 is an enlarged cross-sectional view showing a portion of the configuration of the secondary battery 1. Figs. 1 and 2 show the configuration in a fully discharged state. The secondary battery according to this embodiment is a secondary battery that uses a solid electrolyte layer as the electrolyte layer. The secondary battery according to this embodiment includes so-called all-solid-state batteries.

[0009] 1 , a secondary battery 1 includes a negative electrode current collector foil 2, a positive electrode current collector foil 3, a battery element 4, and an insulating elastic member 8. The battery element 4 is disposed between the negative electrode current collector foil 2 and the positive electrode current collector foil 3 in the stacking direction. The insulating elastic member 8 is disposed so as to surround the battery element 4.

[0010] 1 , a plurality of negative electrode current collector foils 2, a plurality of positive electrode current collector foils 3, and a plurality of battery elements 4 are provided. Specifically, a plurality of negative electrode current collector foils 2 and a plurality of positive electrode current collector foils 3 are alternately arranged in the stacking direction. Each battery element 4 is sandwiched between each negative electrode current collector foil 2 and each positive electrode current collector foil 3.

[0011] The battery element 4 is a part that realizes the charge / discharge function. The battery element 4 has a positive electrode layer 7, a negative electrode layer 5, and a solid electrolyte layer 6, which are stacked in a stacking direction. The positive electrode layer 7 is connected to the positive electrode current collector foil 3. The negative electrode layer 5 is connected to the negative electrode current collector foil 2. The solid electrolyte layer 6 is disposed between the positive electrode layer 7 and the negative electrode layer 5.

[0012] 1 , when viewed along the stacking direction, the outer peripheral edges of the anode layer 5 and the solid electrolyte layer 6 are aligned. The outer peripheral edge of the cathode layer 7 is located more inward than the outer peripheral edges of the anode layer 5 and the solid electrolyte layer 6.

[0013] The battery element 4 is configured so that charging and discharging occur via lithium ions. During charging, lithium ions are conducted from the positive electrode layer 7 to the negative electrode layer 5 via the solid electrolyte layer 6. During discharging, lithium ions are conducted from the negative electrode layer 5 to the positive electrode layer 7 via the solid electrolyte layer 6. The negative electrode layer 5 is configured so that it expands and contracts more than the positive electrode layer 7 during charging and discharging. The thickness of the negative electrode layer 5 increases during charging and decreases during discharging.

[0014] The insulating elastic member 8 is provided to protect the battery element 4. That is, the insulating elastic member 8 functions as a protective material. The insulating elastic member 8 is arranged so as to surround the battery element 4 at least in the planar direction (the direction perpendicular to the stacking direction). That is, the insulating elastic member 8 is frame-shaped. The insulating elastic member 8 contacts the side surface of the battery element 4. No gap is formed between the side surface of the battery element 4 and the insulating elastic member 8. Furthermore, the insulating elastic member 8 is arranged so as to continuously cover the side surfaces of multiple battery elements 4. As shown in FIG. 1 , the portion of the insulating elastic member 8 covering the side surface of one battery element 4 and the portion covering the side surface of the adjacent battery element 4 are continuous in areas where no current collector foils (negative current collector foil 2 and positive current collector foil 3) are present.

[0015] The insulating elastic member 8 is provided so as to expand and contract in the stacking direction in accordance with the expansion and contraction of the negative electrode layer 5. For example, the insulating elastic member 8 is bonded to each current collector foil (positive electrode current collector foil 3 and negative electrode current collector foil 2) and the battery element 4. Therefore, when the negative electrode layer 5 expands, the insulating elastic member 8 is pulled by each current collector foil and the battery element 4 so as to increase its thickness. When the negative electrode layer 5 contracts, the insulating elastic member 8 also contracts.

[0016] In this specification, "adhesion" refers to two objects being in contact with each other in such a way that an attractive force acts on them without the application of an external force. Specifically, this refers to a state in which the surfaces of the objects are bonded together by chemical or physical forces, or both, and is different from a state in which the objects are simply in contact with each other. The insulating elastic member and the current collecting foil may be bonded via an adhesive. In this case, the two surfaces are bonded together by chemical or physical forces, or both, with the adhesive as the medium. On the other hand, if the insulating elastic member itself is a member that has adhesive properties, an adhesive does not necessarily have to be used.

[0017] Here, the insulating elastic member 8 has a base portion 9 and a wide portion 10. The base portion 9 is located to the side of the positive electrode layer 7. The wide portion 10 is a portion that is wider than the base portion 9. Note that the "width" here refers to the distance from the outer circumferential edge of the battery element 4 to the outer circumferential edge of the insulating elastic member 8 in a direction perpendicular to the stacking direction. For details, see FIG. 2. In FIG. 2, the width of the base portion 9 is shown as "width a." Furthermore, the width of the wide portion 10 is shown as "width b." Width b is larger than width a. Note that in FIG. 2, for reference, the boundary between the base portion 9 and the wide portion 10 is shown by a dotted line. However, in reality, the base portion 9 and the wide portion 10 are continuous, and no physical boundary exists.

[0018] The wide portion 10 is provided closer to the negative electrode current collector foil 2 than the base portion 9. That is, the wide portion 10 is provided at a position closer to the negative electrode current collector foil 2 than the base portion 9 in the stacking direction. Therefore, the insulating elastic member 8 is wider in the vicinity of the negative electrode layer 5.

[0019] The wide portion 10 extends so as to protrude laterally from the base portion 9. That is, the outer peripheral edge of the wide portion 10 is located outside the outer peripheral edge of the base portion 9.

[0020] The positive electrode current collector foil 3 and the negative electrode current collector foil 2 are provided to electrically connect the battery element 4 to an external device. The positive electrode current collector foil 3 and the negative electrode current collector foil 2 each have a portion connected to the battery element 4 and a portion extending laterally from the connection portion with the battery element 4. Specifically, each current collector foil (positive electrode current collector foil 3 and negative electrode current collector foil 2) extends laterally from the connection portion with the battery element 4, passing through the insulating elastic member 8. Although not shown, each current collector foil (positive electrode current collector foil 3 and negative electrode current collector foil 2) is connected to a tab at the end opposite the connection portion with the battery element 4.

[0021] The above is a schematic configuration of the secondary battery according to this embodiment. With the above configuration, even if the negative electrode layer 5 expands and contracts due to charge and discharge, damage to the insulating elastic member 8, which is a protective material, is prevented. This point will be explained below with reference to a reference example.

[0022] 3A is a schematic cross-sectional view showing a secondary battery according to a reference example. 3A(a) shows the configuration in a discharged state, and 3A(b) shows the configuration in a charged state. In the secondary battery according to the reference example, the insulating elastic member 8 does not have a wide portion 10. That is, the width of the insulating elastic member 8 is not wide near the negative electrode layer 5. Rather, the width of the insulating elastic member 8 is narrow in the portion surrounding the negative electrode layer 5 (see widths a and b in FIG. 3A).

[0023] In the secondary battery according to the reference example, when the thickness of the negative electrode layer 5 increases due to charging, the insulating elastic member 8 is pulled in the stacking direction, as shown in Fig. 3A(b). At this time, a large tensile force is applied to the insulating elastic member 8 in the stacking direction near the negative electrode layer 5. As a result, the insulating elastic member 8 may separate from the side surface of the battery element 4, causing a defect 11.

[0024] On the other hand, Figure 3B is a schematic cross-sectional view showing the configuration of the secondary battery according to this embodiment during charging and discharging. Figure 3B(a) shows the configuration in the discharged state, and Figure 3B(b) shows the configuration in the charged state. In the secondary battery according to this embodiment, a wide portion 10 is provided near the negative electrode layer 5. That is, the width of the insulating elastic member 8 is increased. Therefore, the insulating elastic member 8 can easily follow the expansion of the negative electrode layer 5. As a result, damage to the insulating elastic member 8 is prevented, unlike the reference example.

[0025] The above is a general description of the secondary battery according to this embodiment.

[0026] The position of the wide portion 10 is not particularly limited as long as it is closer to the negative electrode current collector foil 2 than the base portion 9 in the stacking direction.

[0027] In the example shown in Figure 2, the upper surface of the wide portion 10 (see "c" in Figure 2) is located closer to the positive electrode layer 7 than the upper surface of the solid electrolyte layer 6 (the boundary surface with the positive electrode layer 7). Therefore, a part of the wide portion 10 is located to the side of the positive electrode layer 7. In this way, a part of the wide portion 10 may be located to the side of the positive electrode layer 7.

[0028] On the other hand, the upper surface of the wide portion 10 does not necessarily have to be located closer to the positive electrode layer 7 than the upper surface of the solid electrolyte layer 6. Fig. 4 is a schematic cross-sectional view showing a modified example of this embodiment. In this modified example, the upper surface of the wide portion 10 (see "c" in Fig. 4) is located closer to the negative electrode layer 5 than the boundary surface between the solid electrolyte layer 6 and the positive electrode layer 7. Even with this configuration, the presence of the wide portion 10 makes it easier for the insulating elastic member 8 to follow the expansion of the negative electrode layer 5, thereby preventing damage to the insulating elastic member 8.

[0029] 2 and 4, at least a portion of the wide portion 10 is located to the side of the negative electrode layer 5 in the fully discharged state. That is, in the fully discharged state, the width of the insulating elastic member 8 at the portion located to the side of the negative electrode layer 5 is greater than the width of the base portion 9. With this configuration, the insulating elastic member 8 can more easily follow the expansion of the negative electrode layer 5, and damage to the insulating elastic member 8 is more reliably prevented. However, as will be described in other embodiments below (see FIGS. 7 and 8), the wide portion 10 does not necessarily have to be located to the side of the negative electrode layer 5. It is sufficient that the wide portion 10 is located closer to the negative electrode current collector foil 2 in the stacking direction than the base portion 9.

[0030] In this embodiment, as shown in Fig. 1, the secondary battery 1 includes a plurality of battery elements 4. However, the secondary battery 1 does not necessarily have to include a plurality of battery elements 4. The secondary battery 1 may include a single battery element 4.

[0031] In this embodiment, the outer peripheral edge of the anode layer 5 and the outer peripheral edge of the solid electrolyte layer 6 are aligned when viewed along the stacking direction, and the outer peripheral edge of the cathode layer 7 is located more inward than the outer peripheral edges of the anode layer 5 and the solid electrolyte layer 6. However, the outer peripheral edges of the anode layer 5 and the solid electrolyte layer 6 do not necessarily need to be aligned. Furthermore, the outer peripheral edge of the cathode layer 7 does not necessarily need to be more inward than the outer peripheral edges of the anode layer 5 and the solid electrolyte layer 6. (2) Second Embodiment Next, a second embodiment will be described. Unless otherwise specified, the same configuration as in the first embodiment can be adopted. FIG. 5 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to this embodiment.

[0032] 5, in this embodiment, the outer peripheral surface of the wide portion 10 is inclined with respect to the stacking direction. The outer peripheral surface of the wide portion 10 is inclined so as to face inward from the negative electrode current collector foil 2 side toward the positive electrode layer 7 side along the stacking direction.

[0033] According to this embodiment, damage to the insulating elastic member 8 is more reliably prevented. In the insulating elastic member 8, stress tends to concentrate at the boundary between the base portion 9 and the wide portion 10. Therefore, when a tensile force is applied to the insulating elastic member 8, the boundary between the base portion 9 and the wide portion 10 is likely to become the starting point of fracture. However, in this embodiment, the outer periphery of the wide portion 10 is inclined, so the angle (θ in the figure) formed between the outer periphery of the base portion 9 and the outer periphery of the wide portion 10 is greater than 90°. Therefore, stress is less likely to concentrate at the boundary between the wide portion 10 and the base portion 9. The boundary between the wide portion 10 and the base portion 9 is less likely to become the starting point of fracture. This more reliably prevents damage to the insulating elastic member 8. (3) Third Embodiment Next, a third embodiment will be described. Note that unless otherwise specified, the same configuration as in the first embodiment can be adopted. FIG. 6 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to this embodiment.

[0034] As shown in Fig. 6, the wide section 10 extends so as to protrude laterally from the base section 9. Here, as shown as part a in Fig. 6, the corner formed between the wide section 10 and the base section 9 (the corner formed between the upper surface of the wide section 10 and the outer peripheral surface of the base section 9) is rounded.

[0035] According to this embodiment, the boundary between the wide portion 10 and the base portion 9 is rounded, so that, as in the second embodiment, stress is less likely to concentrate at the boundary. Therefore, breakage originating from the boundary is less likely to occur. This more reliably prevents damage to the insulating elastic member 8. (4) Fourth Embodiment Next, a fourth embodiment will be described. Unless otherwise specified, the same configuration as in the previously described embodiments can be adopted. Figure 7 is a schematic cross-sectional view showing a portion of the secondary battery 1 according to this embodiment.

[0036] In describing the secondary battery 1 according to this embodiment, attention will first be focused on the negative electrode current collector foil 2. The portion of the negative electrode current collector foil 2 that is connected to the negative electrode layer 5 (i.e., the portion that is connected to the battery element 4) is referred to as the "negative electrode foil connection portion 2-1." Additionally, the portion that extends laterally from the negative electrode foil connection portion 2-1 toward the tab is referred to as the "negative electrode foil extension portion 2-2."

[0037] The insulating elastic member 8 has a negative current collector foil contact surface 12 that contacts the negative foil extension portion 2-2. Specifically, the negative foil extension portion 2-2 extends so as to penetrate laterally through the insulating elastic member 8. The insulating elastic member 8 and the negative foil extension portion 2-2 contact each other at the penetration portion of the negative foil extension portion 2-2. As a result, the negative current collector foil contact surface 12 is formed on the insulating elastic member 8.

[0038] When viewed along the stacking direction, the outer edge of the negative current collector foil contact surface 12 (position a in the figure) is located more inward than the outermost portion of the wide portion 10 (position b in the figure). Specifically, the outer peripheral surface of the wide portion 10 is inclined with respect to the stacking direction so that the outermost portion of the wide portion 10 is located more inward as it moves from the outermost portion toward the negative current collector foil 2. Therefore, the width of the negative current collector foil contact surface 12 is narrower than the width of the widest portion of the wide portion 10.

[0039] According to this embodiment, damage to the negative electrode current collector foil 2 is suppressed. When the negative electrode layer 5 expands during charging, the insulating elastic member 8 stretches in the stacking direction. When the insulating elastic member 8 stretches, a force is also applied to the negative electrode current collector foil 2 via the negative electrode current collector foil contact surface 12. That is, the negative electrode current collector foil 2 is pulled by the insulating elastic member 8. The wider the negative electrode current collector foil contact surface 12, the greater the force applied to the negative electrode current collector foil 2. This could result in damage to the negative electrode current collector foil 2. However, according to this embodiment, because the width of the negative electrode current collector foil contact surface 12 is narrow, the force applied from the insulating elastic member 8 to the negative electrode current collector foil 2 is not that great. This prevents damage to the negative electrode current collector foil 2.

[0040] In the example shown in FIG. 7 , the width of the portion of the insulating elastic member 8 located to the side of the negative electrode layer 5 is not wider than the width of the base portion 9. In other words, the portion of the insulating elastic member 8 located to the side of the negative electrode layer 5 does not correspond to the wide portion 10. The area surrounded by the dotted line in FIG. 7 corresponds to the wide portion 10. In this embodiment, the insulating elastic member 8 is less likely to follow the expansion of the negative electrode layer 5 than in the previously described embodiment, where the wide portion 10 is present to the side of the negative electrode layer 5. However, compared to the case where the wide portion 10 is not present, the insulating elastic member 8 is more likely to follow the expansion of the negative electrode layer 5. Therefore, a certain effect is achieved in terms of preventing damage to the insulating elastic member 8. (5) Fifth Embodiment Next, a fifth embodiment will be described. This embodiment can be considered a modification of the fourth embodiment. Unless otherwise specified, the same configuration as the fourth embodiment can be adopted. FIG. 8 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to this embodiment.

[0041] As shown in FIG. 8 , in this embodiment, when viewed along the stacking direction, the outer end of the negative electrode current collector foil contact surface 12 (see “a” in FIG. 8 ) is located more inward than the outer peripheral end of the base portion 9 (see “b” in FIG. 8 ).

[0042] According to this embodiment, the width of the negative electrode current collector foil contact surface 12 is further narrowed. Therefore, the force applied to the negative electrode current collector foil 2 via the insulating elastic member 8 when the negative electrode layer 5 expands is further reduced. This more reliably prevents damage to the negative electrode current collector foil 2. (6) Sixth Embodiment Next, a sixth embodiment will be described. Note that unless otherwise specified, the same configuration as in the previously described embodiments can be adopted. Figure 9 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to this embodiment.

[0043] In this embodiment, the position of the outer peripheral edge of the negative electrode current collector foil 2 is devised. Details are explained below. First, as in the fourth and fifth embodiments, the portion of the negative electrode current collector foil 2 that is connected to the negative electrode layer 5 is defined as the "negative electrode foil connection portion 2-1." Furthermore, the portion that extends laterally from the negative electrode foil connection portion 2-1 so as to be connected to the tab is defined as the "negative electrode foil extension portion 2-2."

[0044] When viewed along the stacking direction, the negative electrode current collector foil 2 does not protrude outward from the negative electrode layer 5 except for the negative electrode foil extension portion 2-2. Specifically, attention should be paid to portion a shown in Figure 9. In portion a, the outer peripheral edge of the negative electrode current collector foil 2 is aligned with the outer peripheral edge of the negative electrode layer 5.

[0045] According to this embodiment, the negative electrode current collector foil 2 does not protrude from the negative electrode layer 5, so the area of ​​contact between the negative electrode current collector foil 2 and the insulating elastic member 8 is reduced. Therefore, the force applied to the negative electrode current collector foil 2 via the insulating elastic member 8 when the negative electrode layer 5 expands is reduced. This more reliably prevents damage to the negative electrode current collector foil 2.

[0046] In the example shown in Fig. 9, the outer peripheral edge of the negative electrode current collector foil 2, excluding the negative electrode foil extension portion 2-2, is aligned with the outer peripheral edge of the negative electrode layer 5. However, the outer peripheral edge of the negative electrode current collector foil 2, excluding the negative electrode foil extension portion 2-2, may be located more inward than the outer peripheral edge of the negative electrode layer 5. (7) Seventh Embodiment Next, a seventh embodiment will be described. Unless otherwise specified, the same configuration as in the previously described embodiments can be adopted. Fig. 10 is a schematic cross-sectional view showing a portion of a secondary battery 1 according to this embodiment.

[0047] This embodiment is premised on the premise that the secondary battery 1 includes at least a pair of battery elements 4 (4-1 and 4-2). The pair of battery elements 4 (4-1 and 4-2) are arranged to sandwich the negative electrode current collector foil 2 in the stacking direction.

[0048] The portion of the insulating elastic member 8 that surrounds one battery element 4-1 is defined as the "first portion 8-1." The portion that surrounds the other battery element 4-2 is defined as the "second portion 8-2." The first portion 8-1 and the second portion 8-2 are continuous with each other at the wide portion 10.

[0049] As in the fourth to sixth embodiments, the portion of the negative electrode current collector foil 2 that is connected to the negative electrode layer 5 is defined as the "negative electrode foil connection portion 2-1." Furthermore, the portion that extends laterally from the negative electrode foil connection portion 2-1 so as to connect to the tab is defined as the "negative electrode foil extension portion 2-2." The negative electrode foil extension portion 2-2 extends from the negative electrode foil connection portion 2-1 so as to penetrate laterally through the wide portion 10. As in the sixth embodiment, the negative electrode current collector foil 2 does not protrude laterally from the negative electrode layer 5, except for the negative electrode foil extension portion 2-2.

[0050] In this embodiment, the thickness of the wide portion 10 is devised. Specifically, the region of the wide portion 10 that overlaps with the negative foil extending portion 2-2 is defined as the "overlapping region 10-1." Furthermore, the region of the wide portion 10 that does not overlap with the negative foil extending portion 2-2 is defined as the "non-overlapping region 10-2." The total thickness of the wide portion 10 excluding the thickness of the negative current collector foil 2 in the overlapping region 10-1 (thickness a+b in FIG. 10 ) is equal to the total thickness of the wide portion 10 in the non-overlapping region 10-2 (thickness c in FIG. 10 ).

[0051] According to the above-described configuration, the amount of elongation of the insulating elastic member 8 when the negative electrode layer 5 expands is uniform between the overlapping region 10-1 and the non-overlapping region 10-2. Therefore, the force applied from the insulating elastic member 8 to the battery element 4 and each current collector foil is uniform. This more reliably prevents damage to the secondary battery 1 due to expansion and contraction during charging and discharging. (8) Others The first to seventh embodiments of the present invention have been described above. Next, the materials of each part included in the secondary battery 1 described in the above-described embodiments will be described. (Insulating Elastic Member) The insulating elastic member may be any elastic member having insulating properties. The elastic modulus of the insulating elastic member is, for example, 0.01 GPa to 4 GPa, preferably 0.1 GPa to 2.5 GPa.

[0052] The insulating elastic member can be formed, for example, from a resin material. Examples of resin materials include elastomer resins, polyethylene resins, polypropylene resins, epoxy resins, ethylene-based copolymers, propylene-based copolymers, and the like. The insulating elastic member can be formed, for example, by fabricating a laminate including the battery element 4 and a current collector foil, then supplying a resin to the side of the laminate and curing it. (Solid Electrolyte Layer) The solid electrolyte layer is solid and may be made of any material that functions as an electrolyte layer in a secondary battery. The solid electrolyte layer 6 includes, 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 6 is, for example, 5 to 100 μm. (Positive Electrode Layer) The positive electrode layer may be made of a material that can release lithium ions during charging and absorb lithium ions during discharging. The positive electrode layer may be made of, for example, a material including a resin binder and a positive electrode active material dispersed in the resin binder. As the positive electrode active material, for example, a lithium metal composite oxide can be used. As the lithium metal composite oxide, for example, LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , and Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn２ 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, preferably 50 to 200 μm. (Negative Electrode Layer) The negative electrode layer may be a layer that deposits lithium during charging, or a layer that occludes lithium during charging. For example, the negative electrode layer may be formed from a material containing a resin binder and a negative electrode active material dispersed in the resin binder. Examples of the negative electrode active material that can be used include metallic lithium, silicon materials, tin materials, compounds containing silicon or tin (oxides, nitrides, alloys with other metals), and carbon materials (graphite, etc.).

[0053] The negative electrode layer may include a negative electrode intermediate layer. The negative electrode intermediate layer is a layer provided in a deposition-type all-solid-state battery for purposes such as protecting the solid electrolyte layer. A deposition-type all-solid-state battery is a secondary battery configured such that metallic lithium is deposited between the solid electrolyte layer and the negative electrode current collector foil during charging. In a deposition-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. For this reason, 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. A negative electrode intermediate layer used for such purposes is also included in the negative electrode layer of this embodiment. The negative electrode intermediate layer can be realized, for example, by a layer containing metal particles such as silver, carbon particles, and a binder resin. (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, a thin film of copper, copper alloy, nickel, or nickel alloy can be used as the negative electrode current collector foil. For example, an aluminum foil can be used as the positive electrode current collector foil. (All-Solid-State Battery) Preferably, the secondary battery according to this embodiment is a precipitation-type all-solid-state battery. That is, it is an all-solid-state battery configured such that metallic lithium is precipitated between the negative electrode current collector foil and the solid electrolyte layer during charging. In such secondary batteries, the negative electrode layer undergoes large expansion and contraction during charging and discharging. Therefore, damage to the insulating elastic member, which serves as a protective material, is likely to be a problem. However, according to the above-described embodiment, the presence of the wide portion prevents damage to the insulating member. Therefore, applying the above-described embodiment to a precipitation-type all-solid-state battery is particularly valuable. [Note] The main aspects and effects of the present invention are summarized below as a note.(Supplementary Note 1) A secondary battery comprising: a negative electrode current collector foil (2), a positive electrode current collector foil (3), a battery element (4) arranged between the positive electrode current collector foil (3) and the negative electrode current collector foil (2) in the stacking direction; and an insulating elastic member (8) arranged to surround the battery element (4), wherein the battery element (4) has a positive electrode layer (7) connected to the positive electrode current collector foil (3), a negative electrode layer (5) connected to the negative electrode current collector foil (2), and a solid electrolyte layer (6) arranged between the positive electrode layer (7) and the negative electrode layer (5), and the insulating elastic member (8) has a base portion (9) located on a side of the positive electrode layer (7) and a wide portion (10) provided on the negative electrode current collector foil (2) side of the base portion (9), and the width of the wide portion (10) is greater than the width of the base portion (9).

[0054] According to this configuration, the provision of the wide portion 10 allows the insulating elastic member 8 to easily follow the expansion of the negative electrode layer 5. As a result, damage to the insulating elastic member 8 is prevented. (Appendix 2) The secondary battery according to Appendix 1, wherein the outer peripheral surface of the wide portion 10 is inclined with respect to the stacking direction so as to face inward as it moves from the negative electrode current collector foil 2 side toward the positive electrode layer 7 side along the stacking direction.

[0055] This configuration prevents the insulating elastic member 8 from breaking at the boundary between the base portion 9 and the wide portion 10. This more reliably prevents damage to the insulating elastic member 8. (Appendix 3) The secondary battery according to appendix 1 or 2, wherein the wide portion 10 extends so as to protrude laterally from the base portion 9, and corners formed between the wide portion 10 and the base portion 9 are rounded.

[0056] According to this configuration, the insulating elastic member 8 is less likely to break at the boundary between the base portion 9 and the wide portion 10. That is, damage to the insulating elastic member 8 is more reliably prevented. (Appendix 4) The secondary battery according to any one of Appendices 1 to 3, wherein the negative electrode current collector foil 2 has a negative electrode foil connection portion 2-1 connected to the negative electrode layer 5, and a negative electrode foil extension portion 2-2 extending laterally from the negative electrode foil connection portion 2-1 so as to be connected to the tab, the insulating elastic member 8 has a negative electrode current collector foil contact surface 12 in contact with the negative electrode foil extension portion 2-2, and when viewed along the stacking direction, the outer edge of the negative electrode current collector foil contact surface 12 is located more inward than the outermost portion of the wide portion 10.

[0057] According to this configuration, the width of the negative electrode current collector foil contact surface 12 is narrowed, and therefore the negative electrode current collector foil 2 is less likely to be pulled by the insulating elastic member 8. As a result, damage to the negative electrode current collector foil 2 is prevented. (Appendix 5) The secondary battery according to Appendix 4, wherein the outer edge of the negative electrode current collector foil contact surface 12 is located more inward than the outer peripheral edge of the base portion 9 when viewed along the stacking direction.

[0058] With this configuration, the width of the negative electrode current collector foil contact surface 12 is narrower, and therefore force from the insulating elastic member 8 is less likely to be applied to the negative electrode current collector foil 2. This more reliably prevents damage to the negative electrode current collector foil 2. (Appendix 6) The secondary battery according to any of Appendices 1 to 5, wherein the negative electrode current collector foil 2 has a negative electrode foil connection portion 2-1 connected to the negative electrode layer 5, and a negative electrode foil extension portion 2-2 extending laterally from the negative electrode foil connection portion 2-1 so as to be connected to the tab, and when viewed along the stacking direction, the negative electrode current collector foil 2 does not protrude outward from the negative electrode layer 5 except for the negative electrode foil extension portion 2-2.

[0059] According to this configuration, the area of ​​contact between the negative electrode current collector foil 2 and the insulating elastic member 8 is reduced. Therefore, the stress applied to the negative electrode current collector foil 2 via the insulating elastic member 8 is reduced, and damage to the negative electrode current collector foil 2 is more reliably prevented. (Appendix 7) In the secondary battery according to Appendix 6, at least one pair of battery elements 4 is provided, and the pair of battery elements (4-1, 4-2) are arranged to sandwich the negative electrode current collector foil 2 in the stacking direction, and the insulating elastic member 8 has a first portion 8-1 that surrounds one of the pair of battery elements in the surface direction and a second portion 8-2 that surrounds the other of the pair of battery elements in the surface direction, and the first portion 8-1 and the second portion 8-2 are connected at their wide portions 10. anode foil extending portion 2-2 extends from anode foil connecting portion 2-1 so as to penetrate laterally through wide portion 10, wide portion 10 has an overlapping region 10-1 that overlaps with anode foil extending portion 2-2 and a non-overlapping region 10-2 that does not overlap with anode foil extending portion 2-2, and a total thickness of wide portion 10 excluding the thickness of anode current collector foil 2 in overlapping region 10-1 is equal to the total thickness of wide portion 10 in non-overlapping region 10-2.

[0060] With this configuration, the amount of elongation of the insulating elastic member 8 is uniform between the overlapping region 10-1 and the non-overlapping region 10-2. This uniformizes the force applied from the insulating elastic member 8 to the battery element 4 and each current collecting foil. This more reliably prevents damage to the secondary battery 1 due to expansion and contraction during charging and discharging. (Appendix 8) The secondary battery according to any one of Appendices 1 to 7, wherein the insulating elastic member 8 has an elastic modulus of 0.01 GPa or more and 4 GPa or less.

[0061] With this configuration, the insulating elastic member 8 can more easily follow the expansion of the negative electrode layer, and damage to the insulating elastic member 8 can be more reliably prevented.

Claims

1. A secondary battery comprising: a negative electrode current collector foil; a positive electrode current collector foil; a battery element arranged between the positive electrode current collector foil and the negative electrode current collector foil in the stacking direction; and an insulating elastic member arranged to surround the battery element, wherein the battery element has a positive electrode layer connected to the positive electrode current collector foil, a negative electrode layer connected to the negative electrode current collector foil, and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, and the insulating elastic member has a base portion located on one side of the positive electrode layer and a wide portion provided on the negative electrode current collector foil side of the base portion, and the width of the wide portion is greater than the width of the base portion.

2. A secondary battery according to claim 1, wherein the outer peripheral surface of the wide portion is inclined with respect to the stacking direction so as to face inward from the negative electrode current collecting foil side toward the positive electrode layer side along the stacking direction.

3. A secondary battery according to claim 1 or 2, wherein the wide portion extends so as to protrude laterally from the base portion, and corners formed between the wide portion and the base portion are rounded.

4. A secondary battery as defined in claim 1 or 2, wherein the negative electrode current collector foil has a negative electrode foil connection portion connected to the negative electrode layer, and a negative electrode foil extension portion extending laterally from the negative electrode foil connection portion so as to be connected to a tab, the insulating elastic member has a negative electrode current collector foil contact surface in contact with the negative electrode foil extension portion, and when viewed along the stacking direction, the outer edge of the negative electrode current collector foil contact surface is located more inward than the outermost portion of the wide portion.

5. A secondary battery according to claim 4, wherein, when viewed along the stacking direction, the outer edge of the contact surface of the negative electrode current collector foil is located inside the outer circumferential edge of the base portion.

6. A secondary battery as claimed in claim 1 or 2, wherein the negative electrode current collector foil has a negative electrode foil connection portion connected to the negative electrode layer, and a negative electrode foil extension portion extending laterally from the negative electrode foil connection portion so as to be connected to a tab, and when viewed along the stacking direction, the negative electrode current collector foil does not protrude outward from the negative electrode layer except for the negative electrode foil extension portion.

7. A secondary battery according to claim 6, wherein at least one pair of the battery elements are provided, the pair of battery elements are arranged in the stacking direction so as to sandwich the negative electrode current collector foil, the insulating elastic member has a first portion surrounding one of the pair of battery elements in the surface direction and a second portion surrounding the other of the pair of battery elements in the surface direction, the first portion and the second portion are continuous at the wide portion, the negative electrode foil extension portion extends from the negative electrode foil connection portion so as to penetrate laterally through the wide portion, the wide portion has an overlapping region that overlaps with the negative electrode foil extension portion and a non-overlapping region that does not overlap with the negative electrode foil extension portion, and the total thickness of the wide portion excluding the thickness of the negative electrode current collector foil in the overlapping region is equal to the total thickness of the wide portion in the non-overlapping region.

8. A secondary battery according to claim 1 or 2, wherein the insulating elastic member has an elastic modulus of 0.01 GPa or more and 4 GPa or less.

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