Secondary battery

Abstract

This secondary battery is provided with: a negative electrode layer; a solid electrolyte layer; a positive electrode layer; an inner elastic body disposed on the solid electrolyte layer so as to surround a side surface of the positive electrode layer; and an outer elastic body disposed so as to surround outer side surfaces of the negative electrode layer, the solid electrolyte layer, and the inner elastic body. The inner elastic body and the outer elastic body both exhibit electrical insulation and non-ionic conductivity. The elastic modulus of the inner elastic body is greater than the elastic modulus of the outer elastic body.

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. Among such secondary batteries, some are known to have a structure in which the sides of the battery element are surrounded by a frame material such as resin for various reasons.

[0003] In relation to the above, for example, Patent Document 1 (JP2022-63685A) describes a battery including an electrode assembly and a laminated exterior body, in which a resin layer A and a resin layer B having different Young's moduli are provided on predetermined portions of the side surface of the electrode assembly. According to Patent Document 1, by using resin layers having different Young's moduli, it is possible to suppress damage to the laminated exterior body.

[0004] The inventors expect the frame material surrounding the battery element to have the function of applying a uniform load to each layer. In secondary batteries using solid electrolytes, the battery element needs to be pressurized in the stacking direction to obtain good charge / discharge characteristics. However, in secondary batteries, the electrode layers may be displaced. As a result, a portion of the edge of the electrode layer may protrude from the other layers. It becomes difficult to apply a load to the protruding portion in the stacking direction. As a result, it becomes difficult to apply a uniform load to each layer. In contrast, if a frame material is arranged to surround the battery element, such displacement can be absorbed. Therefore, a uniform load can be applied to each electrode layer.

[0005] From the viewpoint of applying a load uniformly to each electrode layer, it is desirable that the frame material surrounding the battery element has a certain degree of hardness.

[0006] However, some secondary batteries are known to have a negative electrode layer that expands and contracts significantly during charging and discharging. For example, Li-precipitation secondary batteries are known. Li-precipitation secondary batteries are secondary batteries configured so that metallic lithium is precipitated in the negative electrode layer during charging. In such secondary batteries, the thickness of the negative electrode layer changes significantly during charging and discharging. In secondary batteries in which the negative electrode layer expands and contracts significantly, if the frame material surrounding the battery element is hard, the frame material cannot follow the expansion and contraction of the negative electrode layer, which can cause problems.

[0007] Therefore, an object of the present invention is to provide a secondary battery that allows expansion and contraction of the negative electrode layer while allowing a load to be applied uniformly to each layer.

[0008] In one aspect, a secondary battery according to the present invention includes an anode layer, a solid electrolyte layer disposed on the anode layer, a cathode layer disposed on the solid electrolyte layer, the outer peripheral edge of the cathode layer being located inside the outer peripheral edge of the solid electrolyte layer when viewed along the stacking direction, a frame-shaped inner elastic body disposed on the solid electrolyte layer so as to surround a side surface of the cathode layer, and a frame-shaped outer elastic body disposed so as to surround outer side surfaces of the anode layer, the solid electrolyte layer, and the inner elastic body. Both the inner elastic body and the outer elastic body are insulating and non-ion conductive. The elastic modulus of the inner elastic body is greater than that of the outer elastic body.

[0009] FIG. 1 is a schematic cross-sectional view showing a secondary battery according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing the configuration of a secondary battery according to a reference example during charging and discharging. FIG. 3 is a schematic cross-sectional view showing the configuration of a secondary battery according to the first embodiment during charging and discharging. FIG. 4 is an enlarged cross-sectional view showing a secondary battery according to a second embodiment. FIG. 5 is an enlarged cross-sectional view showing a secondary battery according to a third embodiment. FIG. 6 is an enlarged cross-sectional view showing a secondary battery according to a fourth embodiment. FIG. 7 is an enlarged cross-sectional view showing a secondary battery according to a fifth embodiment. FIG. 8 is an enlarged cross-sectional view showing a secondary battery according to a sixth embodiment. FIG. 9 is an enlarged cross-sectional view showing a secondary battery according to a seventh embodiment.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] (1) First Embodiment Fig. 1 is a schematic cross-sectional view showing a secondary battery 1 according to a first embodiment. Fig. 1 shows the configuration in a discharged state. The secondary battery 1 according to this embodiment is a secondary battery using a solid electrolyte layer as the electrolyte layer. The secondary battery 1 according to this embodiment includes so-called all-solid-state batteries.

[0012] As shown in Fig. 1, the secondary battery 1 includes a negative electrode current collector foil 2, a battery element 11, a positive electrode current collector foil 3, an inner elastic body 7, and an outer elastic body 8. In the example shown in Fig. 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 11 are provided. Specifically, a plurality of negative electrode current collector foils 2 and a plurality of positive electrode current collector foils 3 are arranged alternately in the stacking direction, with each battery element 11 sandwiched between them.

[0013] The battery element 11 is a part that realizes the function of a battery. The battery element 11 has an anode layer 4, a solid electrolyte layer 5, and a cathode layer 6. The anode layer 4 is disposed on the anode current collector foil 2. The cathode layer 6 is disposed on the cathode current collector foil 3. The solid electrolyte layer 5 is disposed between the anode layer 4 and the cathode layer 6. In other words, the anode layer 4 is disposed on the anode current collector foil 2, the solid electrolyte layer 5 is disposed on the anode layer 4, the cathode layer 6 is disposed on the solid electrolyte layer 5, and the cathode current collector foil 3 is disposed on the cathode layer 6.

[0014] When viewed along the stacking direction, the outer circumferential edge of the positive electrode layer 6 is located inside the outer circumferential edges of the solid electrolyte layer 5 and the negative electrode layer 4. In addition, the outer circumferential edge of the negative electrode layer 4 is located inside the outer circumferential edge of the solid electrolyte layer 5.

[0015] The secondary battery 1 according to this embodiment is a Li deposition type secondary battery. Specifically, during charging, lithium ions migrate from the positive electrode layer 6 to the negative electrode layer 4 via the solid electrolyte layer 5. The lithium ions that migrate to the negative electrode layer 4 are deposited as metallic lithium. On the other hand, during discharging, the metallic lithium contained in the negative electrode layer 4 migrates to the positive electrode layer 6 as lithium ions and is absorbed into the positive electrode layer 6. With this configuration, metallic lithium is repeatedly deposited and removed from the negative electrode layer 4 during charging and discharging. Therefore, the thickness of the negative electrode layer 4 changes significantly during charging and discharging.

[0016] The positive electrode current collector foil 3 and the negative electrode current collector foil 2 are provided to electrically connect the battery element 11 to an external device. As described above, the positive electrode current collector foil 3 is disposed on the positive electrode layer 6 and electrically connected to the positive electrode layer 6. The positive electrode current collector foil 3 also has a portion extending laterally from the connection portion with the positive electrode layer 6. Although not shown, the positive electrode current collector foil 3 is connected to a tab at the end opposite the connection portion with the positive electrode layer 6. The negative electrode current collector foil 2 also has a configuration similar to that of the positive electrode current collector foil 3. That is, the negative electrode current collector foil 2 is disposed on the negative electrode layer 4 and electrically connected to the negative electrode layer 4. The negative electrode current collector foil 2 also has a portion extending laterally from the connection portion with the negative electrode layer 4 and is connected to a tab (not shown) at the end opposite the connection portion with the negative electrode layer 4.

[0017] Next, the inner elastic body 7 and the outer elastic body 8 will be described.

[0018] The inner elastic body 7 is frame-shaped. The inner elastic body 7 is disposed on the solid electrolyte layer 5 so as to surround the side surfaces of the positive electrode layer 6. The inner elastic body 7 is insulating and non-ion conductive. The inner elastic body 7 has a higher elastic modulus than the outer elastic body 8. In this specification, "non-ion conductive" means having the function of blocking lithium ions. The inner elastic body 7 surrounds the side surfaces of the positive electrode layer 6 without any gaps. In other words, there are no gaps between the inner elastic body 7 and the side surfaces of the positive electrode layer 6.

[0019] The outer elastic body 8 is also frame-shaped. The outer elastic body 8 is arranged so as to surround the outer side surfaces of the negative electrode layer 4, the solid electrolyte layer 5, and the inner elastic body 7. The outer elastic body 8 is provided continuously for the plurality of battery elements 11. That is, the portion of the outer elastic body 8 that surrounds the side surface of one battery element 11 and the portion that surrounds the side surface of the adjacent battery element 11 are continuous, except for the portions where the current collecting foils (2 and 3) extend toward the tabs.

[0020] The secondary battery 1 is compressed in the stacking direction. Although not shown, for example, a pair of end plates are arranged on the outside of the configuration shown in Fig. 1. Each battery element 11 is compressed via the pair of end plates.

[0021] The above is a schematic configuration of the secondary battery 1 according to this embodiment. With the above configuration, it is possible to apply a load uniformly to each layer while allowing expansion and contraction of the negative electrode layer 4. This point will be explained below with reference to a reference example.

[0022] 2A and 2B are schematic cross-sectional views showing the configuration of a secondary battery according to a reference example during charging and discharging. Fig. 2 shows an enlarged view of the configuration at the end of the secondary battery. Fig. 2A shows the configuration in a discharging state, and Fig. 2B shows the configuration in a charging state. In the secondary battery according to this reference example, the outer side surface of the battery element 11 is surrounded by a single member (frame material 9).

[0023] During charging, as described above, metallic lithium is precipitated in the anode layer 4. Therefore, as shown in FIG. 2( b), the thickness of the anode layer 4 increases. That is, the anode layer 4 expands in the stacking direction. As the anode layer 4 expands, the frame material 9 is also stretched in the stacking direction. If the frame material 9 is made of a hard material, it may not be able to keep up with the expansion of the anode layer and may break. On the other hand, if the frame material 9 is made of a highly flexible material, the load is likely to be released to the outside of the frame material 9. Therefore, it becomes difficult for a sufficient load to be applied to the anode layer 4 in the portion located outside the positive electrode layer 6 (see portion A in FIG. 2).

[0024] Meanwhile, FIG. 3 is a schematic cross-sectional view showing the configuration of the secondary battery 1 according to this embodiment during charging and discharging. FIG. 3 shows an enlarged view of the end of the battery element 11. FIG. 3(a) shows the configuration in a discharged state, and FIG. 3(b) shows the configuration in a charged state. According to this embodiment, an outer elastic body 8 with a low elastic modulus is disposed in the portion surrounding the negative electrode layer 4. Therefore, even if the negative electrode layer 4 expands significantly during charging, the outer elastic body 8 follows the negative electrode layer 4 and is less likely to break. In other words, expansion and contraction of the negative electrode layer 4 is tolerated. On the other hand, an inner elastic body 7 is disposed in the portion surrounding the positive electrode layer 6. Because the elastic modulus of the inner elastic body 7 is greater than that of the outer elastic body 8, a load applied to the inner elastic body 7 along the stacking direction is less likely to be released outward. Therefore, a sufficient load can be applied to the negative electrode layer 4 even in the portion located outside the positive electrode layer 6 (see portion A in FIG. 3). A uniform load can be applied to each layer.

[0025] In addition, according to this embodiment, the inner elastic body 7 and the outer elastic body 8 are non-ionically conductive. This prevents lithium from being deposited on the sides of each electrode layer (positive electrode layer 6 and negative electrode layer 4). If lithium were to be deposited on the sides of each electrode layer (positive electrode layer 6 and negative electrode layer 4), the deposited lithium would be less likely to contribute to the charge / discharge reaction, resulting in a decrease in cycle characteristics. Furthermore, if lithium were to grow from the side surfaces of each electrode layer (positive electrode layer 6 and negative electrode layer 4) around the edges of the solid electrolyte layer 5, there is a possibility that the electrode layers would short-circuit. In contrast, according to this embodiment, lithium deposition on the sides of each electrode layer is suppressed, thereby maintaining cycle characteristics and preventing short-circuiting.

[0026] The first embodiment has been described above.

[0027] In this embodiment, as shown in Fig. 1, the secondary battery 1 includes a plurality of battery elements 11. However, the secondary battery 1 does not necessarily have to include a plurality of battery elements 11. The secondary battery 1 may include a single battery element 11.

[0028] (2) Second Embodiment Next, a second embodiment will be described. Note that detailed description of the second embodiment will be omitted for the fact that the same configuration as the first embodiment can be adopted.

[0029] FIG. 4 is an enlarged cross-sectional view showing a secondary battery 1 according to a second embodiment. FIG. 4 shows the configuration of an end of a battery element 11. FIG. 4 shows the configuration of a portion of the end of the battery element 11 that is different from the end on the side where the positive electrode current collector foil 3 extends toward the tab. In the following description, the end of the battery element 11 on the side where the positive electrode current collector foil 3 extends toward the tab may be referred to as the "positive electrode tab-side end." Meanwhile, the end of the battery element 11 other than the positive electrode tab-side end may be referred to as the "non-positive electrode tab-side end."

[0030] In this embodiment, the adhesive portions between the components of the secondary battery 1 are devised. 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.

[0031] Specifically, in Fig. 4, the bonded portions of the components are shown as "bonded regions 10." As shown in Fig. 4, the inner circumferential surface of the outer elastic body 8 is bonded to the outer circumferential surfaces of the inner elastic body 7 and the solid electrolyte layer 5. These are bonded via, for example, an adhesive. The adhesive is preferably insulating.

[0032] On the other hand, the inner peripheral surface of the outer elastic body 8 is in contact with the outer peripheral surface of the negative electrode layer 4 but is not "bonded" thereto.

[0033] 4, the outer peripheral edge of the positive current collector foil 3 is spaced apart from the outer elastic body 8, except for the portion extending toward the tab. In other words, the outer peripheral edge of the positive current collector foil 3 is located inside the inner peripheral surface of the outer elastic body 8, except for the portion extending toward the tab.

[0034] According to this embodiment, it is possible to more reliably prevent short circuits due to lithium deposition. In a Li deposition-type secondary battery 1, lithium may deposit from the edge of the negative electrode layer 4 so as to wrap around the solid electrolyte layer 5. If such lithium reaches the positive electrode layer 6 or the positive electrode current collector foil 3, a short circuit occurs. However, according to this embodiment, the growth of lithium that wraps around the edge is prevented in the bonding region 10. Therefore, it is possible to prevent short circuits due to the growth of lithium that wraps around the edge.

[0035] In the example shown in Fig. 4, bonding region 10 is provided over the entire outer peripheral surface of inner elastic body 7. This configuration is preferable because it reduces the number of lithium deposition paths that could cause a short circuit. However, bonding region 10 does not necessarily have to be provided over the entire outer peripheral surface of inner elastic body 7. If bonding region 10 is provided over at least a portion of the outer peripheral surface of inner elastic body 7, lithium growth is prevented in that portion, thereby achieving a certain effect in preventing short circuits.

[0036] 4, the adhesive region 10 is provided only on a part of the outer peripheral surface of the solid electrolyte layer 5. However, the adhesive region 10 may be provided over the entire outer peripheral surface of the solid electrolyte layer 5.

[0037] (3) Third Embodiment Next, a third embodiment will be described. Note that detailed description will be omitted for the fact that the same configuration as the previously described embodiments can be adopted.

[0038] Fig. 5 is an enlarged cross-sectional view showing a secondary battery 1 according to a third embodiment. Fig. 5 shows the configuration of an end of a battery element 11. Fig. 5 also shows the configuration of an end of the battery element 11 on the non-positive electrode tab side. In Fig. 5, as in the second embodiment (Fig. 4), the adhesive portions between the components are shown as "adhesive regions 10."

[0039] 5 , in this embodiment, the positive electrode current collector foil 3 is also bonded to the outer elastic body 8 at the end on the non-positive electrode tab side. More specifically, the outer peripheral end (end face) of the positive electrode current collector foil 3 is bonded to the inner peripheral surface of the outer elastic body 8 (see part A in FIG. 5 ).

[0040] According to this embodiment, the positive electrode current collector foil 3 and the outer elastic body 8 are bonded to each other, which reduces the number of paths through which lithium can reach the positive electrode current collector foil 3 from the side surface of the negative electrode layer 4. This makes it possible to more reliably prevent short circuits.

[0041] 5 , the outer elastic body 8 is also bonded to the inner elastic body 7 and the solid electrolyte layer 5, as in the second embodiment. This configuration more reliably prevents short circuits due to lithium deposition. However, in this embodiment, it is sufficient that the positive electrode current collector foil 3 and the outer elastic body 8 are bonded, and the presence or absence of the bonding region 10 in other parts is not limited. If only part of the contact area between the positive electrode current collector foil 3 and the outer elastic body 8 is bonded, short circuits due to lithium can be prevented in that area, thereby achieving a certain effect in terms of short circuit prevention.

[0042] (4) Fourth Embodiment Next, a fourth embodiment will be described. This embodiment can be considered a modification of the third embodiment. Detailed description of the same configuration as the third embodiment will be omitted.

[0043] Fig. 6 is an enlarged cross-sectional view showing the secondary battery 1 according to this embodiment. Fig. 6 shows the configuration of the end of the battery element 11. Fig. 6 also shows the configuration of the end on the non-positive electrode tab side. In Fig. 6, as in the second embodiment (Fig. 4) and the like, the adhesive portions between the components are shown as "adhesive regions 10."

[0044] 6 , at the non-positive electrode tab side end, the outer peripheral end of the positive electrode current collector foil 3 is located between the inner peripheral surface and the outer peripheral surface of the outer elastic body 8. In other words, the outer peripheral end of the positive electrode current collector foil 3 is present inside the outer elastic body 8. The contact portions between the positive electrode current collector foil 3 and the outer elastic body 8 are bonded together.

[0045] In this embodiment as well, the positive electrode current collector foil 3 and the outer elastic body 8 are bonded together, which further reduces the number of paths through which lithium can reach the positive electrode current collector foil 3 from the negative electrode layer 4 at the end portion. This makes it possible to more reliably prevent short circuits.

[0046] (5) Fifth Embodiment Next, a fifth embodiment will be described. Detailed description will be omitted for the fact that the same configuration as the above-described embodiments can be adopted.

[0047] Fig. 7 is an enlarged cross-sectional view showing the secondary battery 1 according to this embodiment. Fig. 7 shows the configuration of the end portion of the battery element 11. In Fig. 7, as in the second embodiment (Fig. 4) and the like, the adhesive portions between the components are shown as "adhesive regions 10."

[0048] 7, in this embodiment, an adhesive region 10 exists on the side surface of the negative electrode layer 4 (see part A in FIG. 7). That is, the inner peripheral surface of the outer elastic body 8 and the outer peripheral surface of the negative electrode layer 4 are adhered to each other.

[0049] According to the above-described configuration, the outer elastic body 8 does not separate from the side surface of the negative electrode layer 4, which more reliably prevents lithium from being deposited on the side surface of the negative electrode layer 4. As a result, short circuits can be more reliably prevented.

[0050] 7 , adhesive region 10 is provided not only on the side surface of negative electrode layer 4 but also in a position that covers the end portion of solid electrolyte layer 5 and the outer peripheral surface of inner elastic body 7. If adhesive region 10 is provided in such a position, it is possible to more reliably prevent a short circuit due to lithium precipitation that wraps around the end portion.

[0051] However, in this embodiment, it is sufficient that the side surface of the negative electrode layer 4 and the inner circumferential surface of the outer elastic body 8 are bonded together, and there is no particular limitation on the presence or absence of the bonding region 10 in other parts. If the side surface of the negative electrode layer 4 and the inner circumferential surface of the outer elastic body 8 are bonded together, a certain effect in preventing short circuits can be obtained.

[0052] (6) Sixth Embodiment Next, a sixth embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0053] Fig. 8 is an enlarged cross-sectional view showing the secondary battery 1 according to this embodiment. Fig. 8 shows the configuration of the end of the battery element 11. Fig. 8 also shows the configuration of the end on the positive electrode tab side. In Fig. 8, as in the second embodiment (Fig. 4) and the like, the adhesive portions between the components are shown as "adhesive regions 10."

[0054] At the positive electrode tab side end, the outer peripheral edge of the positive electrode current collector foil 3 is located outward from the outer peripheral edge of the outer elastic body 8 when viewed along the stacking direction. Part of the positive electrode current collector foil 3 is in contact with the inner elastic body 7 and the outer elastic body 8.

[0055] 8 , in this embodiment, the entire contact area between the positive current collector foil 3 and the inner elastic body 7 is an adhesive region 10. In addition, the entire contact area between the positive current collector foil 3 and the outer elastic body 8 is also an adhesive region 10. In other words, the positive current collector foil 3 is adhered to the inner elastic body 7 and the outer elastic body 8 at all contact areas.

[0056] According to the above-described configuration, the number of paths through which lithium can reach the positive electrode layer 6 or the positive electrode current collector foil 3 from the side surface of the negative electrode layer 4 is reduced. Therefore, it is possible to more reliably prevent short circuits at the ends via lithium.

[0057] Preferably, as shown in Fig. 8, the inner circumferential surface of the inner elastic body 7 and the outer circumferential surface of the positive electrode layer 6 are also bonded. The inner elastic body 7 and the solid electrolyte layer 5 are also bonded. By bonding these interfaces, the paths for lithium to reach the positive electrode layer 6 from the side surface of the negative electrode layer 4 are reduced, thereby more reliably preventing short circuits.

[0058] In the preferred example shown in Figure 8, the inner circumferential surface of the inner elastic body 7 and the outer circumferential surface of the positive electrode layer 6 are bonded to each other at all contact areas. However, in this preferred example, the inner circumferential surface of the inner elastic body 7 and the outer circumferential surface of the positive electrode layer 6 do not necessarily have to be bonded to each other at all contact areas. If the inner circumferential surface of the inner elastic body 7 and the outer circumferential surface of the positive electrode layer 6 are bonded to each other at least in part of the contact area, lithium deposition can be prevented at the bonded area, thereby achieving a certain effect in preventing short circuits. Similarly, the inner elastic body 7 and the solid electrolyte layer 5 do not necessarily have to be bonded to each other at all contact areas. If they are bonded to each other in part of the contact area, a certain effect in preventing short circuits can be achieved.

[0059] (7) Seventh Embodiment Next, a seventh embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0060] Fig. 9 is an enlarged cross-sectional view showing the secondary battery 1 according to this embodiment. Fig. 9 shows the configuration of the end of the battery element 11. Fig. 9 shows the configuration of a portion of the end of the battery element 11 where the negative electrode current collector foil 2 extends toward the tab. In Fig. 9, as in the second embodiment (Fig. 4) and the like, the adhesive portions between the components are shown as "adhesive regions 10."

[0061] 9 , at least the portion of the end of the negative electrode current collector foil 2 that extends toward the tab is located outside the outer peripheral edge of the outer elastic body 8. At least a portion of the negative electrode current collector foil 2 is in contact with the outer elastic body 8.

[0062] In this embodiment, an adhesive region 10 is provided on the outer periphery of the outer elastic body 8. That is, the outer periphery of the outer elastic body 8 is adhered to the negative electrode current collector foil 2.

[0063] According to this embodiment, it is possible to prevent the outer elastic body 8 from peeling off from the negative electrode current collector foil 2. This makes it difficult for the outer elastic body 8 to separate from the side surface of the negative electrode layer 4. This makes it possible to prevent lithium that does not contribute to charge and discharge (inactive lithium) from being deposited on the side surface of the negative electrode layer 4, thereby improving the cycle characteristics.

[0064] (8) Others The embodiments of the present invention have been described above using Embodiments 1 to 7. Next, the materials of each part included in the secondary battery described in the above embodiments will be described.

[0065] (Inner elastic body and outer elastic body) The inner elastic body and outer elastic body can be formed, for example, from a resin material. Examples of resin materials include rubber (e.g., silicone rubber). The inner elastic body has a modulus of elasticity of, for example, 0.1 to 4 GPa. The outer elastic body has a modulus of elasticity of, for example, 0.1 to 20 MPa.

[0066] (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.

[0067] (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 ４In 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.

[0068] (Negative Electrode Layer) The negative electrode layer may be any layer as long as it is configured so that metallic lithium is deposited during charging and that metallic lithium is released during discharging.

[0069] In this specification, the concept of "negative electrode layer" includes a "negative electrode intermediate layer." A negative electrode intermediate layer is a layer provided in a Li-precipitation-type all-solid-state battery for the purpose of protecting the solid electrolyte layer, etc. As described above, a Li-precipitation-type all-solid-state battery is a secondary battery configured so that metallic lithium is deposited between the solid electrolyte layer and the negative electrode current collector foil during charging. In a Li-precipitation-type all-solid-state battery, the deposited metallic lithium functions as a 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 a purpose is also included in the negative electrode layer in this embodiment. In a Li-precipitation-type all-solid-state battery having such a negative electrode intermediate layer, metallic lithium is hardly present on the negative electrode side during discharge. Therefore, in the discharged state, the negative electrode layer can be said to be composed of the negative electrode intermediate layer. On the other hand, in the charged state, metallic lithium exists between the negative electrode intermediate layer and the negative electrode current collector foil. In the charged state, the negative electrode layer can be said to be composed of the negative electrode intermediate layer and metallic lithium. 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.

[0070] (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.

[0071] [Supplementary Note] The present invention has been described above with reference to the embodiments. Next, the main aspects and effects of the present invention will be summarized as supplementary notes.

[0072] (Supplementary Note 1) A secondary battery comprising: an anode layer 4; a solid electrolyte layer 5 disposed on the anode layer; and a cathode layer 6 disposed on the solid electrolyte layer, wherein an outer peripheral edge of the cathode layer is located more inward than the outer peripheral edge of the solid electrolyte layer when viewed along the stacking direction; an inner elastic body 7 that is frame-shaped and disposed on the solid electrolyte layer so as to surround a side surface of the cathode layer; and an outer elastic body 8 that is frame-shaped and disposed so as to surround outer side surfaces of the anode layer 4, the solid electrolyte layer 5, and the inner elastic body 7, wherein both the inner elastic body 7 and the outer elastic body 8 are insulating and non-ion conductive, and the elastic modulus of the inner elastic body 7 is greater than that of the outer elastic body 8.

[0073] With this configuration, the inner elastic body 7 with a high elastic modulus is provided on the side of the positive electrode layer, so that a sufficient load can be applied to the negative electrode layer 4 even outside the positive electrode layer 6. This allows a uniform load to be applied to each layer included in the battery element 11. Furthermore, the outer elastic body 8 with a low elastic modulus is disposed around the negative electrode layer 4, allowing expansion and contraction of the negative electrode layer 4. Furthermore, the inner elastic body 7 and the outer elastic body 8 are non-ion conductive, so that lithium deposition that would wrap around the solid electrolyte layer is prevented, preventing short circuits.

[0074] (Supplementary Note 2) The secondary battery according to Supplementary Note 1, wherein the inner circumferential surface of the outer elastic body 8 is bonded to the outer circumferential surfaces of the inner elastic body 7 and the solid electrolyte layer 5.

[0075] The above-described structure prevents lithium from growing at the bonded portion, thereby preventing short circuits caused by lithium depositing at the ends of the battery element 11.

[0076] (Appendix 3) The secondary battery according to appendix 1 or 2, further comprising a positive electrode current collector foil 3 disposed on the positive electrode layer 6, the positive electrode current collector foil 3 being adhered to the outer elastic body 8.

[0077] According to the above-described configuration, the number of paths for lithium to reach the positive electrode current collector foil 3 from the side surface of the negative electrode layer 4 is reduced, so that short circuits are more reliably prevented.

[0078] (Appendix 4) The secondary battery according to any one of appendices 1 to 3, wherein the inner circumferential surface of the outer elastic body 8 and the outer circumferential surface of the negative electrode layer 4 are bonded to each other.

[0079] According to the above-described configuration, the outer elastic body 8 is less likely to separate from the side surface of the negative electrode layer 4, thereby preventing lithium from being deposited on the side surface of the negative electrode layer 4. This makes it more difficult for lithium to reach the components on the positive electrode side from the side surface of the negative electrode layer 4, thereby more reliably preventing short circuits.

[0080] (Appendix 5) The secondary battery according to any one of Appendices 1 to 4, further comprising a positive electrode current collector foil 3 disposed on the positive electrode layer 6, the positive electrode current collector foil 3 being in contact with an inner elastic body 7 and an outer elastic body 8, the positive electrode current collector foil 3 and the inner elastic body 7 being bonded together at all contacting portions, and the positive electrode current collector foil 3 and the outer elastic body 8 being bonded together at all contacting portions.

[0081] According to the above-described configuration, the number of paths for lithium to reach the positive electrode current collector foil 3 from the side surface of the negative electrode layer 4 is reduced, so that short circuits are more reliably prevented.

[0082] (Appendix 6) The secondary battery according to Appendix 5, wherein the inner circumferential surface of the inner elastic body 7 and the outer circumferential surface of the positive electrode layer 6 are bonded together, and the inner elastic body 7 and the solid electrolyte layer 5 are bonded together.

[0083] According to the above-described configuration, the number of paths for lithium to reach the positive electrode layer 6 from the side surface of the negative electrode layer 4 is reduced, so that short circuits are more reliably prevented.

[0084] (Supplementary Note 7) The secondary battery according to any one of Supplementary Notes 1 to 6, further comprising: a negative electrode current collector foil 2 disposed on the negative electrode layer 4; at least a part of an outer peripheral edge of the negative electrode current collector foil 2 is located outward from an outer peripheral edge of the outer elastic body 8 when viewed along the stacking direction; and the outer periphery of the outer elastic body 8 is bonded to the negative electrode current collector foil 2.

[0085] The above-described configuration can prevent the outer elastic body 8 from peeling off from the negative electrode current collector foil 2. As a result, the outer elastic body 8 is less likely to separate from the side surface of the negative electrode layer 4. This can prevent lithium that does not contribute to charge and discharge (inactive lithium) from being deposited on the side surface of the negative electrode layer 4.

Claims

1. A secondary battery comprising: an anode layer; a solid electrolyte layer disposed on the anode layer; a cathode layer disposed on the solid electrolyte layer, wherein an outer peripheral edge of the cathode layer is located more inward than an outer peripheral edge of the solid electrolyte layer when viewed along the stacking direction; an inner elastic body that is frame-shaped and disposed on the solid electrolyte layer so as to surround a side surface of the positive electrode layer; and an outer elastic body that is frame-shaped and disposed so as to surround outer side surfaces of the anode layer, the solid electrolyte layer, and the inner elastic body, wherein the inner elastic body and the outer elastic body are both insulating and non-ion conductive, and the elastic modulus of the inner elastic body is greater than the elastic modulus of the outer elastic body.

2. A secondary battery according to claim 1, wherein the inner peripheral surface of the outer elastic body is bonded to the outer peripheral surfaces of the inner elastic body and the solid electrolyte layer.

3. A secondary battery according to claim 1 or 2, further comprising a positive electrode current collector foil disposed on said positive electrode layer, said positive electrode current collector foil being in contact with said outer elastic body, and said outer elastic body and said positive electrode current collector foil being bonded together.

4. A secondary battery according to claim 1 or 2, wherein the inner peripheral surface of the outer elastic body and the outer peripheral surface of the negative electrode layer are bonded together.

5. A secondary battery according to claim 1 or 2, further comprising a positive electrode current collecting foil disposed on the positive electrode layer, the positive electrode current collecting foil being in contact with the inner elastic body and the outer elastic body, the positive electrode current collecting foil and the inner elastic body being bonded at all contacting portions, and the positive electrode current collecting foil and the outer elastic body being bonded at all contacting portions.

6. A secondary battery according to claim 5, wherein the inner circumferential surface of the inner elastic body and the outer circumferential surface of the positive electrode layer are bonded together, and the inner elastic body and the solid electrolyte layer are bonded together.

7. A secondary battery according to claim 1 or 2, further comprising a negative electrode current collector foil disposed on the negative electrode layer, wherein at least a portion of the outer peripheral edge of the negative electrode current collector foil is located outside the outer peripheral edge of the outer elastic body when viewed along the stacking direction, and the outer periphery of the outer elastic body is bonded to the negative electrode current collector foil.

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