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 that has a frame shape and is disposed so as to surround the battery element. The battery element has a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, the solid electrolyte layer covers a side surface of the positive electrode layer and does not cover a side surface of the negative electrode layer, and the insulating elastic member covers the outer side surfaces of the solid electrolyte layer and the negative electrode layer so that the solid electrolyte layer does not come into contact with the negative electrode current collector foil.

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 referred to as a battery element. Among such secondary batteries, there is known a structure in which the side surfaces of the battery element are covered with a frame material such as resin.

[0003] In relation to the above, for example, Patent Document 1 (WO 2020 / 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. In particular, Patent Document 1 (FIG. 1A) discloses a battery in which the side surface of the anode layer is covered with the solid electrolyte layer, and the outer periphery of the solid electrolyte layer is in contact with the anode current collector.

[0004] Incidentally, a Li-precipitation type secondary battery is known. A Li-precipitation type secondary battery is a secondary battery configured so that metallic lithium is precipitated on the negative electrode layer during charging. In such a Li-precipitation type secondary battery, if a configuration is adopted in which the side surface of the negative electrode layer is covered with a solid electrolyte layer as described in Patent Document 1, the location of metallic lithium precipitation may not be controllable. For example, metallic lithium may precipitate while destroying the solid electrolyte layer.

[0005] Furthermore, in a secondary battery using a solid electrolyte layer, it is desirable that the battery elements be uniformly pressurized in order to obtain good charge / discharge characteristics.

[0006] Therefore, an object of the present invention is to provide a secondary battery in which the location of deposition of metallic lithium is controlled and the battery elements are uniformly pressurized.

[0007] 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, and a frame-shaped insulating elastic member disposed so as to surround the battery element. 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 disposed between the positive electrode layer and the negative electrode layer. The solid electrolyte layer covers the side surface of the positive electrode layer but not the side surface of the negative electrode layer. The insulating elastic member covers the outer side surfaces of the solid electrolyte layer and the negative electrode layer so that the solid electrolyte layer does not contact the negative electrode current collector foil.

[0008] 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 during charging and discharging. FIG. 3 is a cross-sectional view showing an enlarged portion of a secondary battery according to a second embodiment. FIG. 4 is a schematic cross-sectional view showing a secondary battery according to a third embodiment. FIG. 5 is a schematic cross-sectional view showing a secondary battery according to a fourth embodiment. FIG. 6 is a schematic cross-sectional view showing a secondary battery according to a fifth embodiment. FIG. 7 is a cross-sectional view showing an enlarged portion of a secondary battery according to a sixth embodiment. FIG. 8 is a cross-sectional view showing an enlarged portion of a secondary battery according to a seventh embodiment.

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

[0010] (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 according to this embodiment is a secondary battery using a solid electrolyte layer as the electrolyte layer. The secondary battery according to this embodiment includes so-called all-solid-state batteries.

[0011] 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 5. 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 5 is frame-shaped. The insulating elastic member 5 is disposed so as to surround the battery element 4 in the planar direction (the direction perpendicular to the stacking direction).

[0012] 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 4 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 4 sandwiched between them. Each current collector foil (2, 3) extends laterally from a connection portion with the battery element 4. Although not shown, each current collector foil (2, 3) is bundled at its end and connected to a tab.

[0013] The battery element 4 is a part that realizes the charge / discharge function. The battery element 4 has a positive electrode layer 6, a solid electrolyte layer 7, and a negative electrode layer 8. These are stacked in the stacking direction. The positive electrode layer 6 is connected to the positive electrode current collector foil 3. The negative electrode layer 8 is connected to the negative electrode current collector foil 2. The solid electrolyte layer 7 is disposed between the positive electrode layer 6 and the negative electrode layer 8.

[0014] Here, the solid electrolyte layer 7 covers not only the top surface (the surface opposite to the surface in contact with the positive current collector foil 3) of the positive electrode layer 6, but also the side surface. Specifically, when viewed along the stacking direction, the solid electrolyte layer 7 is wider than the positive electrode layer 6. That is, when viewed along the stacking direction, the outer side surface of the solid electrolyte layer 7 is located outside the outer peripheral edge of the positive electrode layer 6. The solid electrolyte layer 7 is curved at its outer periphery so as to cover both the top surface and the side surface of the positive electrode layer 6.

[0015] On the other hand, the side surfaces of the negative electrode layer 8 are not covered with the solid electrolyte layer 7 .

[0016] When viewed along the stacking direction, the outer peripheral edge of the negative electrode layer 8 is located further outward than the outer peripheral edge of the positive electrode layer 6. When viewed along the stacking direction, the outer peripheral edge of the solid electrolyte layer 7 is located further outward than the outer peripheral edge of the negative electrode layer 8.

[0017] The battery element 4 is configured so that metallic lithium is deposited in the anode layer 8 during charging. That is, during charging, lithium ions are conducted from the cathode layer 6 to the anode layer 8 via the solid electrolyte layer 7, and metallic lithium is deposited in the anode layer 8. Due to the deposition of metallic lithium, the anode layer 8 expands significantly. On the other hand, during discharging, lithium ions are conducted from the anode layer 8 to the cathode layer 6 via the solid electrolyte layer 7, and lithium is absorbed in the cathode layer 6. During discharging, metallic lithium is lost from the anode layer 8, causing the anode layer 8 to contract. Therefore, the thickness of the anode layer 8 changes significantly during charging and discharging. On the other hand, the thickness of the positive electrode layer 6 changes less during charging and discharging than that of the anode layer 8.

[0018] The insulating elastic member 5 is provided to protect the battery element 4. The insulating elastic member 5 is also provided to apply pressure to the battery element 4 uniformly.

[0019] The insulating elastic member 5 covers the outer side surfaces of the solid electrolyte layer 7 and the negative electrode layer 8. There is no gap between the inner side surface of the insulating elastic member 5 and the outer side surfaces of the solid electrolyte layer 7 and the negative electrode layer 8. Therefore, the insulating elastic member 5 separates the solid electrolyte layer 7 from the negative electrode current collector foil 2. In other words, the solid electrolyte layer 7 and the negative electrode current collector foil 2 do not come into contact with each other.

[0020] The insulating elastic member 5 is disposed so as to continuously cover the side surfaces of the plurality of battery elements 4. That is, as shown in Fig. 1 , the portion of the insulating elastic member 5 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 a portion where no current collector foils (positive electrode current collector foil 3 and negative electrode current collector foil 2) are present.

[0021] The positive electrode current collector foil 3 and the negative electrode current collector foil 2 are each 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 an electrode layer (positive electrode layer 6 or negative electrode layer 8) and a portion extending laterally from the portion connected to the electrode layer. Except for the current collector foils arranged at the outermost positions in the stacking direction, each current collector foil (2, 3) extends laterally from the portion connected to the electrode layer so as to penetrate through the solid electrolyte layer 7 and the insulating elastic member 5. Although not shown, as described above, the current collector foils (2, 3) are bundled at the end opposite the battery element 4 and connected to a tab.

[0022] The secondary battery 1 is compressed in the stacking direction. Although not shown, for example, a pair of end plates are disposed on the outside of the configuration shown in Fig. 1. Each battery element 4 is compressed via the pair of end plates.

[0023] Next, the operation of the secondary battery 1 during charging and discharging will be described. Fig. 2 is a schematic cross-sectional view showing the configuration of the secondary battery 1 during charging and discharging. Fig. 2 shows an enlarged view of the configuration at the portion where the negative electrode current collector foil 2 penetrates the insulating elastic member 5. Fig. 2(a) shows the configuration in a discharging state, and Fig. 2(b) shows the configuration in a charging state.

[0024] As described above, during charging, lithium contained in the positive electrode layer 6 migrates as lithium ions to the negative electrode layer 8 through the solid electrolyte layer 7. The lithium ions are precipitated as metallic lithium in the negative electrode layer 8. The precipitation of metallic lithium increases the thickness of the negative electrode layer 8, as shown in FIG. 2(b).

[0025] According to this embodiment, the location of metallic lithium deposition is controlled. If the solid electrolyte layer 7 were disposed to cover the side surface of the negative electrode layer 8 and its outer periphery were in contact with the negative electrode current collector foil 2, there would be less room for the negative electrode layer 8 to expand. Therefore, metallic lithium may unintentionally deposit in locations other than the negative electrode layer 8. In particular, metallic lithium may deposit while destroying the solid electrolyte layer 7. In contrast, according to this embodiment, the solid electrolyte layer 7 and the negative electrode current collector foil 2 are separated by the insulating elastic member 5. The side surface of the negative electrode layer 8 is covered by the insulating elastic member 5, but not by the solid electrolyte layer 7. Because the insulating elastic member 5 is elastic, it can expand and contract. Therefore, in the secondary battery 1 according to this embodiment, there is room for the negative electrode layer 8 to expand and contract in the stacking direction. This prevents metallic lithium from depositing in unintended locations. Furthermore, metallic lithium deposition that would destroy the solid electrolyte layer 7 can also be prevented.

[0026] Additionally, according to this embodiment, the positive electrode layer 6, which has a small expansion and contraction amount, is covered by the solid electrolyte layer 7, including its side surfaces. Furthermore, the outer side surfaces of the negative electrode layer 8 and the solid electrolyte layer 7 are covered by the insulating elastic member 5. By adopting this configuration, the battery element 4 can be uniformly pressurized. Specifically, in this embodiment, the outer peripheral edge of the negative electrode layer 8 is located further outward than the outer peripheral edge of the positive electrode layer 6. That is, the positions of the electrode layers are not aligned. If the side surfaces of the positive electrode layer 6 were not covered by the solid electrolyte layer 7, gaps would be formed on the sides of the positive electrode layer 6. Such gaps would prevent a load from being applied to the end of the negative electrode layer 8 in the stacking direction. However, according to this embodiment, since the side surfaces of the positive electrode layer 6 are covered by the solid electrolyte layer 7, a load can be applied even to the portion of the negative electrode layer 8 that protrudes from the positive electrode layer 6. Furthermore, in this embodiment, the positions of the outer side surfaces of the solid electrolyte layer 7 and the outer peripheral edge of the negative electrode layer 8 are not aligned. Therefore, if the insulating elastic member 5 were not provided, it would be difficult to apply a load to the end of the solid electrolyte layer 7. However, according to this embodiment, since the insulating elastic member 5 is provided, a load can also be applied to the end of the solid electrolyte layer 7. In other words, the battery element 4 can be pressurized uniformly.

[0027] The first embodiment has been described above.

[0028] 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.

[0029] (2) Second Embodiment Next, a second embodiment will be described. Note that detailed description will be omitted for the points where the same configuration as the previously described embodiment can be adopted.

[0030] 3 is an enlarged cross-sectional view of a portion of the secondary battery 1 according to this embodiment, showing the configuration of the portion where the negative electrode current collector foil 2 extends so as to penetrate the insulating elastic member 5.

[0031] In this embodiment, a corner following portion e is added to the negative electrode layer 8 in order to more reliably control the location where metallic lithium is deposited.

[0032] In detail, as shown in FIG. 3 , the solid electrolyte layer 7 has an electrolyte layer outer side surface "a", a negative electrode-facing surface "b", and an electrolyte layer corner "c". The electrolyte layer outer side surface "a", as its name suggests, is the outer side surface of the solid electrolyte layer 7. The negative electrode-facing surface "b" is the surface facing the negative electrode layer 8 (the surface in contact with the negative electrode layer 8). The electrolyte layer corner "c" is a corner formed between the electrolyte layer outer side surface "a" and the negative electrode-facing surface "b". The electrolyte layer corner "c" is formed by a curved surface that bulges outward.

[0033] The negative electrode layer 8 has a current collector foil connection portion "d" and the above-mentioned corner following portion "e". The current collector foil connection portion "d" is a portion that contacts the negative electrode current collector foil 2. The corner following portion "e" is a portion that extends from the end of the current collector foil connection portion "d" so as to follow the electrolyte layer corner portion "c". The corner following portion "e" is covered by the insulating elastic member 5. Therefore, the corner following portion "e" is separated from the negative electrode current collector foil 2. In the portion where the negative electrode current collector foil 2 penetrates the insulating elastic member 5, the space between the corner following portion "e" and the negative electrode current collector foil 2 is filled with the insulating elastic member 5.

[0034] According to this embodiment, since the corner following portion "e" is provided, the location of metallic lithium deposition can be more reliably controlled. If the corner following portion "e" were not provided, metallic lithium could be deposited in an uncontrollable manner on the electrolyte layer corner "c". However, according to this embodiment, the negative electrode layer 8 (corner following portion "e") is provided in advance on the electrolyte layer corner "c". Therefore, deposition of metallic lithium on the electrolyte layer corner "c" is permitted. This suppresses deposition of metallic lithium in unexpected locations, and more reliably prevents damage to the secondary battery 1.

[0035] (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.

[0036] 4 is a schematic cross-sectional view showing a secondary battery 1 according to this embodiment. In this embodiment, the configuration of the contact portion between the solid electrolyte layer 7 and the positive electrode current collector foil 3 is devised. Specifically, an insulating treatment layer 9 is provided at the contact portion between the solid electrolyte layer 7 and the positive electrode current collector foil 3.

[0037] Specifically, the positive electrode current collector foil 3 has a positive electrode foil connection portion 3-1 and a positive electrode foil excess portion 3-2. The positive electrode foil connection portion 3-1 is a portion connected to the positive electrode layer 6. The positive electrode foil excess portion 3-2 is a portion that protrudes from the positive electrode layer 6.

[0038] The portion of the solid electrolyte layer 7 that covers the side surface of the positive electrode layer 6 is defined as a side surface covering portion 10. The side surface covering portion 10 is connected to the top and bottom surfaces of the positive electrode foil excess portion 3-2. An insulating treatment layer 9 is provided between the side surface covering portion 10 and the positive electrode foil excess portion 3-2.

[0039] According to this embodiment, it is possible to prevent a short circuit via metallic lithium. As described above, metallic lithium is deposited on the negative electrode layer 8 during charging. At this time, the metallic lithium may grow from the end of the negative electrode layer 8, wrapping around the outer side surface of the solid electrolyte layer 7, and may reach the positive electrode current collector foil 3. As a result, a short circuit may occur between the negative electrode layer 8 and the positive electrode layer 6. However, according to this embodiment, the provision of the insulating treatment layer 9 makes it possible to prevent such a short circuit.

[0040] (4) Fourth Embodiment Next, a fourth 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.

[0041] 5 is a schematic cross-sectional view showing a secondary battery 1 according to this embodiment. In this embodiment, the solid electrolyte layer 7 and the positive electrode current collector foil 3 are devised in their configurations.

[0042] In this embodiment, it is assumed that the secondary battery 1 includes at least a pair of battery elements (4-1 and 4-2). The pair of battery elements (4-1 and 4-2) are arranged to sandwich the positive electrode current collector foil 3 in the stacking direction.

[0043] The solid electrolyte layer 7 of one battery element 4 - 1 and the solid electrolyte layer 7 of the other battery element 4 - 2 are continuous at a position outside the outer circumferential edge of the positive electrode current collector foil 3 .

[0044] Specifically, the positive electrode current collector foil 3 has a positive electrode foil connection portion 3-1 and a positive electrode foil extension portion 3-3. The positive electrode foil connection portion 3-1 is a portion connected to the positive electrode layer 6. The positive electrode foil extension portion 3-3 is a portion extending laterally from the positive electrode foil connection portion 3-1 so as to be connected to a tab (not shown). The positive electrode foil extension portion 3-3 extends laterally from the positive electrode foil connection portion 3-1 so as to penetrate through the solid electrolyte layer 7 and the insulating elastic member 5.

[0045] The outer peripheral edge of the positive current collector foil 3, excluding the positive foil extension 3-3, is located inside the inner side surface of the solid electrolyte layer 7. In other words, the outer peripheral edge of the positive current collector foil 3, excluding the positive foil extension 3-3, is covered with the solid electrolyte layer 7.

[0046] According to the above-described configuration, it is possible to prevent a short circuit via metallic lithium, as in the third embodiment. That is, since the outer peripheral edge of the positive current collector foil 3, except for the positive foil extension portion 3-3, is covered with the solid electrolyte layer 7, even if metallic lithium grows around the outer side surface of the solid electrolyte layer 7, the metallic lithium does not come into contact with the outer peripheral edge of the positive current collector foil 3. Therefore, it is possible to prevent a short circuit.

[0047] (5) Fifth Embodiment Next, a fifth embodiment will be described. This embodiment can be considered a modification of the fourth embodiment. Detailed description of the features that can employ the same configuration as the fourth embodiment will be omitted.

[0048] 6 is a schematic cross-sectional view showing a secondary battery 1 according to this embodiment. In this embodiment, an insulating treatment layer 11 is further added to the fourth embodiment.

[0049] The insulating layer 11 is provided between the outer peripheral edge of the positive current collector foil 3 in the planar direction and the solid electrolyte layer 7. In addition, an insulating layer 9 is provided in the portion where the positive foil extension portion 3-3 penetrates the solid electrolyte layer 7, as in the third embodiment (see FIG. 4).

[0050] According to this embodiment, short circuits are more reliably prevented. The positive electrode layer 6 may expand and contract due to charging and discharging, although not as much as the negative electrode layer 8. The expansion and contraction of the positive electrode layer 6 may cause cracks in the solid electrolyte layer 7. The solid electrolyte layer 7 is prone to cracking on the sides of the positive electrode current collector foil 3. As described above, metallic lithium may grow from the end of the negative electrode layer 8 so as to wrap around the outer side surface of the solid electrolyte layer 7. The grown metallic lithium may come into contact with the positive electrode current collector foil 3 through cracks in the solid electrolyte layer 7. However, according to this embodiment, since the insulating treatment layer 11 is provided, short circuits are prevented even if cracks occur in the solid electrolyte layer 7.

[0051] (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.

[0052] 7 is an enlarged cross-sectional view of a portion of the secondary battery 1 according to this embodiment. In this embodiment, the structure of the adhesive portion between the insulating elastic member 5 and the battery element 4 is devised.

[0053] In Figure 7, the adhesive portion between the insulating elastic member 5 and the battery element 4 is shown as adhesive portion "a." As shown in Figure 7, the insulating elastic member 5 is adhered to the outer side surface of the solid electrolyte layer 7. On the other hand, although the insulating elastic member 5 is in contact with the side surface of the negative electrode layer 8, it is not "adhered" to it. In this specification, "adhesion" refers to two objects being in contact with each other in such a manner 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 they are simply in contact with each other.

[0054] According to this embodiment, the insulating elastic member 5 and the outer side surface of the solid electrolyte layer 7 are bonded together, so that a gap is unlikely to form between the insulating elastic member 5 and the solid electrolyte layer 7. This prevents metallic lithium from being deposited in the gap between the insulating elastic member 5 and the solid electrolyte layer 7. In other words, the deposition of metallic lithium that would wrap around the outer side surface of the solid electrolyte layer 7 is suppressed, making it possible to more reliably prevent a short circuit.

[0055] The insulating elastic member 5 and the solid electrolyte layer 7 may be bonded via an adhesive. In this case, the two surfaces are bonded by chemical or physical forces, or both, using the adhesive as a medium. On the other hand, if the insulating elastic member 5 itself is a member that has adhesive properties, an adhesive need not necessarily be used.

[0056] (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.

[0057] 8 is an enlarged cross-sectional view of a portion of the secondary battery 1 according to this embodiment. In this embodiment, the width of the insulating elastic member 5 is devised. Specifically, the width of the insulating elastic member 5 is wider in the portion surrounding the negative electrode layer 8 (see width b in FIG. 8 ) than in the portion surrounding the positive electrode layer 6 (see width a in FIG. 8 ). Note that the "width" of the insulating elastic member 5 here refers to the distance from the inner peripheral edge to the outer peripheral edge of the insulating elastic member 5 in the planar direction.

[0058] Specifically, as shown in FIG. 8 , the side surface of the positive electrode layer 6 is inclined with respect to the stacking direction. The side surface of the positive electrode layer 6 is inclined so that the width of the positive electrode layer 6 increases as the portion thereof approaches the positive current collector foil 3. The outer side surface of the solid electrolyte layer 7 is also inclined in accordance with the inclination of the side surface of the positive electrode layer 6. That is, the outer side surface of the solid electrolyte layer 7 is inclined so that the further away from the negative electrode layer 8 it is, the more outward in the planar direction it is. The inner side surface of the insulating elastic member 5 is also inclined in accordance with the outer side surface of the solid electrolyte layer 7. On the other hand, the outer side surface of the insulating elastic member 5 is not inclined but extends along the stacking direction. Therefore, the width of the insulating elastic member 5 increases as the portion thereof approaches the negative electrode layer 8.

[0059] The above-described configuration prevents damage to the secondary battery 1 due to expansion and contraction during charging and discharging. During charging, the thickness of the negative electrode layer 8 increases significantly. As the thickness of the negative electrode layer 8 increases, the insulating elastic member 5 also stretches along the stacking direction in the portion surrounding the negative electrode layer 8. If the width of the insulating elastic member 5 is narrow in the portion surrounding the negative electrode layer 8, the insulating elastic member 5 is likely to separate from the side surface of the negative electrode layer 8. This makes it difficult for the insulating elastic member 5 to follow the expansion of the negative electrode layer 8. As a result, the secondary battery 1 may be damaged. However, in this embodiment, the width of the insulating elastic member 5 is wide in the portion surrounding the negative electrode layer 8, so the insulating elastic member 5 can easily follow the expansion and contraction of the negative electrode layer 8. This prevents damage to the secondary battery 1.

[0060] (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.

[0061] (Insulating Elastic Member) The insulating elastic member may be any elastic member having insulating properties. The insulating elastic member has a modulus of elasticity of, for example, 0.01 GPa to 4 GPa, preferably 0.1 GPa to 2.5 GPa.

[0062] The insulating elastic member can be formed, for example, from a resin material, etc. Examples of the resin material include elastomer resin, polyethylene resin, polypropylene resin, epoxy resin, ethylene copolymer, propylene copolymer, etc. The insulating elastic member can be formed, for example, by producing a laminate including the battery element 4 and the current collector foil, supplying a resin to the side surface of the laminate, and curing the resin.

[0063] (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.

[0064] (Positive Electrode Layer) The positive electrode layer may be formed of a material that can release lithium ions during charging and absorb lithium ions during discharging. The positive electrode layer may be formed of a material containing, for example, a resin binder and a positive electrode active material dispersed in the resin binder. For example, a lithium metal composite oxide may be used as the positive electrode active material. For example, the lithium metal composite oxide may be LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , and Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ , and LiNi ０．５ Mn １．５ O ４ spinel-type compounds such as LiFePO ４ , and LiMnPO ４ Olivine type compounds such as Li ２ FeSiO ４ , and Li ２ MnSiO ４ In addition, 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.

[0065] (Negative Electrode Layer) The negative electrode layer may be any layer configured to deposit metallic lithium during charging and release metallic lithium during discharging. For example, the negative electrode layer contains metallic lithium as a negative electrode active material.

[0066] The negative electrode layer includes a negative electrode intermediate layer. The 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 such 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. Therefore, a negative electrode intermediate layer is provided between the solid electrolyte layer and the negative electrode current collector foil. The metallic lithium is deposited between the negative electrode intermediate layer and the negative electrode current collector foil. The presence of the negative electrode intermediate layer protects the solid electrolyte layer from metallic lithium. The 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.

[0067] (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.

[0068] [Addendum] The main aspects and effects of the present invention are summarized below as appendices.

[0069] (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) disposed between the positive electrode current collector foil and the negative electrode current collector foil; and a frame-shaped insulating elastic member (5) disposed so as to surround the battery element, wherein the battery element (4) has a positive electrode layer (6) connected to the positive electrode current collector foil, a negative electrode layer (8) connected to the negative electrode current collector foil, and a solid electrolyte layer (7) disposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer (7) covers a side surface of the positive electrode layer (6) but does not cover a side surface of the negative electrode layer (8), and the insulating elastic member (5) covers outer side surfaces of the solid electrolyte layer (7) and the negative electrode layer (8) so that the solid electrolyte layer (7) does not come into contact with the negative electrode current collector foil (2).

[0070] With this configuration, it is possible to control the location of deposition of metallic lithium during charging, thereby preventing damage to the solid electrolyte layer 7. Also, it is possible to apply pressure uniformly to the battery elements.

[0071] (Supplementary Note 2) In the secondary battery according to Supplementary Note 1, the solid electrolyte layer 7 has an anode-facing surface that is a surface facing the anode layer, an electrolyte layer outer side surface that is an outer side surface, and an electrolyte layer corner that is a corner formed between the anode-facing surface and the outer side surface of the solid electrolyte layer, and the anode layer 8 has a current collector foil connection portion that is a portion that contacts the anode current collector foil, and a corner following portion that extends from an end of the current collector foil connection portion so as to follow the electrolyte layer corner portion.

[0072] According to this configuration, the negative electrode layer 8 is provided in advance at the corners of the solid electrolyte layer 7, so that deposition of metallic lithium at the corners is permitted, and uncontrolled deposition of metallic lithium at the corners can be prevented.

[0073] (Supplementary Note 3) The secondary battery according to Supplementary Note 1 or 2, wherein the positive electrode current collector foil 3 has a positive electrode foil excess portion 3-2 that protrudes from the positive electrode layer when viewed along the stacking direction, a portion of the solid electrolyte layer 7 that covers a side surface of the positive electrode layer is defined as a side surface covering portion 10, and the side surface covering portion 10 is connected to the positive electrode foil excess portion 3-2 via an insulating treatment layer 9.

[0074] According to this configuration, since the insulating treatment layer 9 is provided, even if metallic lithium is deposited so as to wrap around the outer side surface of the solid electrolyte layer 7, the metallic lithium does not come into contact with the positive electrode current collector foil 3. This makes it possible to prevent a short circuit.

[0075] (Appendix 4) The secondary battery according to any one of Appendices 1 to 3, wherein the battery elements 4 are provided in pairs so as to sandwich the positive electrode current collector foil 3 in the stacking direction, and the solid electrolyte layer of one of the pair of battery elements and the solid electrolyte layer of the other of the pair of battery elements are continuous at a position outside the outer peripheral edge of the positive electrode current collector foil 3.

[0076] According to this configuration, the outer peripheral edge of the positive electrode current collector foil 3 is covered with the solid electrolyte layer 7, so that even if metallic lithium is deposited so as to wrap around the outer side surface of the solid electrolyte layer 7, the metallic lithium does not come into contact with the positive electrode current collector foil 3. This makes it possible to prevent a short circuit.

[0077] (Appendix 5) The secondary battery according to appendix 4, wherein an insulating treatment layer 11 is provided between the outer peripheral edge of the positive electrode current collector foil 3 and the solid electrolyte layer 7 in the surface direction.

[0078] According to this configuration, since the insulating treatment layer 11 is provided, even if the solid electrolyte layer 7 cracks, metallic lithium grown from the negative electrode side does not come into contact with the positive electrode current collector foil 3. This makes it possible to prevent a short circuit.

[0079] (Appendix 6) The secondary battery according to any one of appendices 1 to 5, wherein the insulating elastic member 5 is bonded to an outer side surface of the solid electrolyte layer 7, and is not bonded to a side surface of the negative electrode layer 8.

[0080] This configuration can prevent a gap from being formed between the insulating elastic member 5 and the solid electrolyte layer 7. This can prevent metallic lithium from being deposited between the insulating elastic member 5 and the solid electrolyte layer 7, thereby preventing a short circuit.

[0081] (Supplementary Note 7) The secondary battery according to any one of Supplementary Notes 1 to 6, wherein the width of the insulating elastic member 5 is wider at a portion surrounding the negative electrode layer than at a portion surrounding the positive electrode layer.

[0082] With this configuration, the insulating elastic member 5 can easily follow the expansion and contraction of the negative electrode layer 8. This can prevent damage to the secondary battery 1.

[0083] (Supplementary Note 8) The secondary battery according to any one of Supplementary Notes 1 to 7, wherein the insulating elastic member has an elastic modulus of 0.01 GPa or more and 4 GPa or less.

[0084] With this configuration, the insulating elastic member 5 can easily follow the expansion and contraction of the negative electrode layer 8. This can prevent damage to the secondary battery 1.

Claims

1. A secondary battery comprising: 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; and a frame-shaped insulating elastic member disposed so as 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 disposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer covers a side surface of the positive electrode layer but does not cover a side surface of the negative electrode layer, and the insulating elastic member covers outer side surfaces of the solid electrolyte layer and the negative electrode layer so that the solid electrolyte layer does not come into contact with the negative electrode current collector foil.

2. A secondary battery as defined in claim 1, wherein the solid electrolyte layer has an anode-facing surface that is the surface facing the anode layer, an electrolyte layer outer side surface that is the outer side surface, and an electrolyte layer corner that is a corner formed between the anode-facing surface and the outer side surface of the solid electrolyte layer, and the anode layer has a current collector foil connection portion that is a portion that contacts the anode current collector foil, and a corner following portion that extends from an end of the current collector foil connection portion so as to follow the electrolyte layer corner portion.

3. A secondary battery according to claim 1 or 2, wherein the positive electrode current collector foil has a positive electrode foil excess portion that protrudes from the positive electrode layer when viewed along the stacking direction, the portion of the solid electrolyte layer that covers the side surface of the positive electrode layer is defined as a side surface covering portion, and the side surface covering portion is connected to the upper and lower surfaces of the positive electrode foil excess portion via an insulating treatment layer.

4. A secondary battery according to claim 1 or 2, wherein the battery elements are provided in pairs so as to sandwich the positive electrode current collector foil in the stacking direction, and the solid electrolyte layer of one of the pair of battery elements and the solid electrolyte layer of the other of the pair of battery elements are continuous at a position outside the outer peripheral edge of the positive electrode current collector foil.

5. A secondary battery according to claim 4, wherein an insulating layer is provided between the outer peripheral edge of the positive electrode current collector foil in the surface direction and the solid electrolyte layer.

6. A secondary battery according to claim 1 or 2, wherein the insulating elastic member is bonded to the outer side surface of the solid electrolyte layer, but is not bonded to the side surface of the negative electrode layer.

7. A secondary battery according to claim 1 or 2, wherein the width of the insulating elastic member is wider at the portion surrounding the negative electrode layer than at the portion surrounding the positive electrode layer.

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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