Secondary batteries

Abstract

A secondary battery according to the present invention comprises a porous body, a positive electrode and a negative electrode. The porous body has an electrolyte region which is loaded with a solid electrolyte and a non-loaded region which is not loaded with a solid electrolyte. The non-loaded region has a non-communication region in which both sides of the porous body in the stacking direction are not in communication with each other. The non-communication region is provided in a position where the non-communication region is continued to the outer peripheral part of the electrolyte region and surrounds the electrolyte region.

Description

Technical Field

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

Background Art

[0002] There is known a secondary battery in which a positive electrode and a negative electrode are provided so as to sandwich an electrolyte layer, and charge and discharge are performed by the movement of lithium ions between the positive electrode and the negative electrode. As such a secondary battery, there is known one having a configuration in which a solid electrolyte is supported on a sheet-like porous body. By supporting the solid electrolyte on the porous body, an independent electrolyte layer can be obtained even if it is thin.

[0003] Related technologies are disclosed, for example, in Patent Document 1 (JP2021-533542A). Patent Document 1 discloses a step of preparing a laminated structure by sequentially laminating a first protective layer, a film-like first solid electrolyte material, a porous base material, a film-like second solid electrolyte material, and a second protective layer, a step of pressing this laminated structure to push the first solid electrolyte material and the second solid electrolyte material into the porous base material and filling the pores of the porous base material with the solid electrolyte material, and a step of removing the first protective layer and the second protective layer. The pressing is performed by a roll press method, and a method for manufacturing a solid electrolyte membrane for an all-solid-state battery is disclosed. Since this solid electrolyte membrane is a composite of a porous polymer material such as a non-woven fabric and a solid electrolyte material, it can be manufactured in a thin film type of 70 μm or less while having excellent strength, which is advantageous for improving the energy density of the battery.

Summary of the Invention

[0004] By the way, in a secondary battery in which lithium ions are used for charge and discharge, lithium dendrites may grow from the negative electrode during charging. If the lithium dendrites grow so as to go around the end of the electrolyte layer, the positive electrode and the negative electrode will be short-circuited. This problem can also occur in a secondary battery having a configuration in which a solid electrolyte is supported on a porous body.

[0005] Therefore, the object of the present invention is to provide a technology that can prevent short circuits caused by lithium dendrites in a secondary battery having a configuration in which a solid electrolyte is supported on a porous body. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic cross-sectional view showing a secondary battery according to the first embodiment. [Figure 2] Figure 2 is a plan view showing a porous material. [Figure 3] Figure 3 is a schematic cross-sectional view showing a secondary battery according to the second embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing a secondary battery according to the third embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing a secondary battery according to the fourth embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view showing a secondary battery according to the fifth embodiment. [Figure 7] Figure 7 is a schematic cross-sectional view showing a secondary battery according to the sixth embodiment. [Figure 8] Figure 8 is a schematic cross-sectional view showing an example of a secondary battery according to the seventh embodiment. [Figure 9] Figure 9 is a schematic diagram showing another example of a secondary battery according to the seventh embodiment. [Modes for carrying out the invention]

[0007] Embodiments of the present invention will be described below with reference to the drawings.

[0008] First Embodiment The secondary battery 1 according to this embodiment is a secondary battery in which charging and discharging are performed by the movement of lithium ions. This secondary battery 1 is a so-called all-solid-state battery.

[0009] (Summary) Figure 1 is a schematic cross-sectional view of a secondary battery 1 according to this embodiment. As shown in Figure 1, the secondary battery 1 has a configuration in which a plurality of battery cells 2 are stacked. Specifically, the secondary battery 1 is provided with a plurality of positive electrode current collector foils 4 and a plurality of negative electrode current collector foils 3. The plurality of positive electrode current collector foils 4 and the plurality of negative electrode current collector foils 3 are arranged alternately in the stacking direction.

[0010] Each battery cell 2 is provided between adjacent positive electrode current collector foils 4 and negative electrode current collector foils 3. Each battery cell 2 is formed by a positive electrode 9, a negative electrode 8, and an electrolyte region 6. The electrolyte region 6 is a region provided on a sheet-like porous body 5, and is a region on which a solid electrolyte is supported. The electrolyte region 6 is sandwiched between the positive electrode 9 and the negative electrode 8. In other words, the positive electrode 9 and the negative electrode 8 are arranged above and below the porous body 5 so as to sandwich the electrolyte region 6. The positive electrode 9 is provided between the electrolyte region 6 and the positive electrode current collector foil 4, and the negative electrode 8 is provided between the electrolyte region 6 and the negative electrode current collector foil 3.

[0011] When viewed along the stacking direction, the external shapes of the positive electrode 9, negative electrode 8, and electrolyte region 6 are generally identical. However, they do not need to be perfectly identical; a slight misalignment is acceptable.

[0012] The secondary battery 1 described above generates electricity in the region where the positive electrode 9, the negative electrode 8, and the electrolyte region 6 overlap (hereinafter sometimes referred to as the power generation region). Specifically, during charging, lithium ions are conducted from the positive electrode 9 side to the negative electrode 8 side via the electrolyte region 6, and lithium ions are absorbed at the negative electrode 8 side. Alternatively, lithium is deposited at the negative electrode 8 side. On the other hand, during discharge, lithium ions move from the negative electrode 8 side to the positive electrode 9 side, and lithium is absorbed at the positive electrode 9.

[0013] In such a secondary battery 1, as previously described, lithium dendrites may grow from the end of the negative electrode 8. If the lithium dendrites grow to wrap around the end of the electrolyte region 6, a short circuit will occur between the positive electrode 9 and the negative electrode 8. Therefore, in this embodiment, the structure of the porous body 5 has been modified.

[0014] Figure 2 is a plan view showing the porous body 5. As shown in FIGS. 1 and 2, each porous body 5 is provided with a non-support region 7 in addition to the electrolyte region 6.

[0015] As described above, the electrolyte region 6 is a region where the solid electrolyte is supported, and is provided at the central portion of each porous body 5. In the electrolyte region 6, communication holes are provided in each porous body 5 so that lithium ions can be conducted. The communication holes are holes that penetrate each porous body 5. The solid electrolyte is supported in these communication holes.

[0016] On the other hand, the non-support region 7 is a region where the solid electrolyte is not supported. The non-support region 7 is provided at the outer peripheral portion of each porous body 5 and surrounds the electrolyte region 6.

[0017] The non-support region 7 is provided with a communication region 10 and a non-communication region 11.

[0018] The communication region 10 is a region where both sides of the porous body 5 communicate in the stacking direction. Specifically, both sides of the porous body 5 communicate through the communication holes.

[0019] On the other hand, the non-communication region 11 is a region where both sides of the porous body 5 do not communicate in the stacking direction. The non-communication region 11 is provided at a position surrounding the electrolyte region 6 and is continuous with the outer peripheral portion of the electrolyte region 6. The non-communication region 11 may be, for example, a region where there are no communication holes in the porous body 5 itself. Alternatively, the non-communication region 11 may be a region where there are communication holes in the porous body 5 itself but the communication holes are blocked.

[0020] According to the configuration as described above, since the non - communicating region 11 is provided, it is possible to prevent the growth of lithium dendrites that wind around the end of the electrolyte region 6. If the non - communicating region 11 is not provided, that is, when the upper and lower parts of the porous body 5 communicate with each other in the region outside the electrolyte region 6, lithium dendrites tend to grow so as to penetrate the porous body 5. Therefore, a short - circuit between the negative electrode 8 and the positive electrode 9 due to lithium dendrites can become a problem. However, in the present embodiment, since the non - communicating region 11 is provided outside the electrolyte region 6, it is possible to prevent the growth of lithium dendrites that short - circuit the positive electrode 9 and the negative electrode 8.

[0021] Subsequently, details of each part in the secondary battery 1 according to the present embodiment will be described.

[0022] (Porous body) The material of the porous body 5 may be any material that can support a solid electrolyte and is not particularly limited. For example, the porous body 5 can be produced by the materials and methods described below.

[0023] First, a porous sheet having through - holes is prepared. As the porous sheet having through - holes, for example, a non - woven fabric, a porous separator, and a sheet formed with through - holes by lithography processing can be used. As the non - woven fabric, for example, a polyester non - woven fabric, a polyethylene non - woven fabric, and a non - woven fabric made of cellulose fibers can be used.

[0024] Subsequently, a slurry having a solid electrolyte is applied to the region where the electrolyte region 6 is to be formed and dried. Thereby, the electrolyte region 6 is formed.

[0025] In addition, the communication holes around the electrolyte region 6 are blocked, forming a non-communication region 11. For example, if a material that melts with heat is used as the porous sheet, the communication holes can be blocked by partially heating and melting the porous sheet. Alternatively, the communication holes can be blocked by filling the porous sheet with a resin material or the like so that the communication holes are filled. Alternatively, as will be explained in the embodiments described later, the communication holes can also be blocked by placing a covering material on the upper or lower surface of the porous sheet.

[0026] The above is an example of a method for producing a porous body 5 using a porous sheet having interconnected holes.

[0027] On the other hand, the porous body 5 can also be fabricated using a porous sheet that does not originally have interconnecting pores (for example, a porous sheet with closed pores). In this case, interconnecting pores are first formed only in certain areas (areas intended to become the electrolyte area 6 and the interconnecting area 10) by lithography or the like. Next, a slurry containing a solid electrolyte is applied to the area intended to become the electrolyte area 6 and dried. This forms the electrolyte area 6. Using this method, it is also possible to obtain a porous body 5 having an electrolyte area 6, an interconnecting area 10, and a non-interconnecting area 11.

[0028] The thickness of the porous body 5 is not particularly limited. For example, the thickness of the porous body 5 in the electrolyte region 6 is 5 to 100 μm, preferably 20 to 60 μm.

[0029] The solid electrolyte supported on the porous body 5 can be any solid that functions as an electrolyte. For example, sulfide solid electrolytes and oxide solid electrolytes can be used as the solid electrolyte. Preferably, the solid electrolyte is a sulfide solid electrolyte. Examples of sulfide solid electrolytes include LPS-based (e.g., argyrodite (Li6PS5Cl)) and LGPS-based (e.g., Li 10 GeP2S 12 The materials listed are:

[0030] (positive electrode) The positive electrode 9 can be formed from a material that releases lithium ions during charging and absorbs lithium ions during discharge. The positive electrode 9 can be formed from a material that includes, for example, 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. Examples of lithium metal composite oxides include layered rock salt type compounds such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2, LiMn2O4, and LiNi 0.5 Mn 1.5 Examples include spinel-type compounds such as O4, olivine-type compounds such as LiFePO4 and LiMnPO4, or Si-containing compounds such as Li2FeSiO4 and Li2MnSiO4. Also, Li4Ti5O 12 Other options can also be used.

[0031] The thickness of the positive electrode 9 is not particularly limited, but is, for example, 10 to 500 μm, preferably 50 to 200 μm.

[0032] (Negative electrode) The negative electrode 8 only needs to be configured to intercalate (or deposit) lithium during charging and release lithium ions during discharge. For example, the negative electrode 8 can be formed from a material comprising a resin binder and a negative electrode active material dispersed in the resin binder. Examples of negative electrode active materials that can be used include lithium metal, silicon materials, tin materials, compounds containing silicon or tin (oxides, nitrides, alloys with other metals), and carbon materials (graphite, etc.).

[0033] The secondary battery 1 according to this embodiment may be a so-called "fully deposited" secondary battery. A fully deposited secondary battery is a battery configured such that, in a completely discharged state, lithium is not contained on the negative electrode side as a negative electrode active material, and during charging, lithium ions move from the positive electrode side to the negative electrode side, and lithium metal is deposited on the negative electrode current collector foil 3. In such a battery, at least the lithium metal deposited on the negative electrode side during charging functions as a negative electrode 8, and is therefore included in the secondary battery 1 of the present invention.

[0034] Furthermore, in the fully deposited secondary battery 1, a negative electrode intermediate layer may be placed between the solid electrolyte layer and the negative electrode current collector foil. The negative electrode intermediate layer is a layer interposed between the deposited lithium metal and the solid electrolyte layer. The negative electrode intermediate layer contains a lithium-reactive material. Examples of lithium-reactive materials include materials capable of intercalating and releasing lithium ions during charging, and metals capable of alloying with lithium during charging.

[0035] While there are no particular limitations on the material capable of intercalating and deintercalating lithium ions, carbon materials are preferred. Specific examples of carbon materials include carbon black (specifically, acetylene black, Ketjenblack®, furnace black, channel black, thermal lamp black, etc.), carbon nanotubes (CNTs), graphite, and hard carbon. Among these, carbon black is preferred, and it is more preferable that it be at least one selected from the group consisting of acetylene black, Ketjenblack®, furnace black, channel black, and thermal lamp black.

[0036] Examples of metals that can be alloyed with lithium include In, Al, Si, Sn, Mg, Au, Ag, and Zn. Among these, In, Si, Sn, and Ag are preferred, with Ag being more preferred.

[0037] The lithium-reactive material may be used alone or in combination of two or more types. In the case of using two or more types in combination, it is preferable to use a material capable of intercalating and deintercalating lithium ions in combination with a metal that can alloy with lithium. This ensures sufficient strength and lithium-ion conductivity of the negative electrode intermediate layer. More specifically, it is preferable to use nanoparticles made of In, Si, Sn, and Ag in combination with carbon black, and more preferably to use nanoparticles made of Ag in combination with carbon black. When using a material capable of intercalating and deintercalating lithium ions in combination with a metal that can alloy with lithium, the mixing ratio (mass ratio) is not particularly limited, but the ratio of the material capable of intercalating and deintercalating lithium ions to the metal that can alloy with lithium is preferably 10:1 to 1:1, and more preferably 5:1 to 2:1.

[0038] The content of lithium-reactive material in the negative electrode intermediate layer (referring to the total content of two or more materials if they are used in combination; the same applies hereinafter) is not particularly limited, but is preferably in the range of 50 to 100% by mass, more preferably in the range of 70 to 100% by mass, even more preferably in the range of 85 to 99% by mass, and particularly preferably in the range of 90 to 100% by mass.

[0039] The negative electrode intermediate layer may consist solely of lithium-reactive material if a self-supporting film can be fabricated using only lithium-reactive material, but may also contain a binder as needed. The type of binder is not particularly limited, and any known binder in the art can be used as appropriate. Examples include polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethylcellulose.

[0040] The binder content in the negative electrode intermediate layer is not particularly limited, but is preferably in the range of 1 to 15% by mass, and more preferably in the range of 5 to 10% by mass. If the binder content is 1% by mass or more, a negative electrode intermediate layer with sufficient strength can be formed. If the binder content is 15% by mass or less, a negative electrode intermediate layer with sufficient lithium ion conductivity can be formed.

[0041] The thickness of the negative electrode intermediate layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 5 to 40 μm, and even more preferably 10 to 30 μm. When the thickness of the negative electrode intermediate layer is 1 μm or more, the functions of the negative electrode intermediate layer can be fully exhibited. When the thickness of the negative electrode intermediate layer is 50 μm or less, the decrease in energy density can be suppressed.

[0042] (Positive electrode current collector foil and negative electrode current collector foil) The positive electrode current collector foil 4 and the negative electrode current collector foil 3 are provided to electrically connect the secondary battery 1 to an external device. As shown in Figure 1, the positive electrode current collector foil 4 and the negative electrode current collector foil 3 each extend laterally from the power generation area. The positive electrode current collector foil 4 and the negative electrode current collector foil 3 are each formed from a conductive thin film. For example, aluminum foil can be used as the positive electrode current collector foil 4. For example, a stainless steel thin film and a copper thin film can be used as the negative electrode current collector foil 3.

[0043] (Manufacturing example) The manufacturing method of the secondary battery 1 according to this embodiment is not particularly limited. Below, a specific example of a manufacturing method for the secondary battery 1 according to this embodiment will be described.

[0044] [Fabrication of the positive electrode] A slurry is prepared by weighing and mixing predetermined amounts of positive electrode active material, sulfide solid electrolyte, conductive additive, binder, and xylene. The prepared slurry is applied to carbon-coated aluminum foil (positive electrode current collector foil 4). The slurry is applied to both sides in a predetermined area. After application, drying is performed. This results in a positive electrode current collector foil 4 with a positive electrode 9 having a thickness of 200 μm (100 μm on each side).

[0045] [Preparation of porous materials supported with solid electrolytes] A slurry is prepared by weighing and mixing predetermined amounts of sulfide solid electrolyte, binder, and xylene. The prepared slurry is directly coated onto a 40 μm porous sheet (with interconnecting pores) and dried. This causes the solid electrolyte to be supported on the porous sheet, forming an electrolyte region 6. Furthermore, a coating material is placed in a predetermined area to form a non-connecting region 11. This results in obtaining a porous body 5.

[0046] [Fabrication of the negative electrode] A slurry is prepared by weighing and mixing predetermined amounts of negative electrode active material, binder, and NMP (N-methylpyrrolidone). The prepared slurry is applied to a SUS foil (negative electrode current collector foil 3). The slurry is applied to both sides in a predetermined area. After application, drying is performed. This results in a negative electrode current collector foil 3 with a negative electrode 8 having a thickness of 100 μm (50 μm on each side).

[0047] [Fabrication of positive electrode / solid electrolyte / negative electrode laminates] The porous body 5 and the negative electrode current collector foil 3, on which the negative electrode 8 is formed, are placed above and below the positive electrode current collector foil 4, on which the positive electrode 9 created by the procedure described above is formed. Then, a laminate is obtained by rolling these together.

[0048] [Fabrication of cell stacks] Furthermore, multiple layers of the resulting laminates are stacked. Then, aluminum tabs are joined to the positive electrode current collector foil 4 and Ni-plated copper tabs are joined to the negative electrode current collector foil 3 using an ultrasonic welding machine. Finally, the laminates are placed in an aluminum laminate film and vacuum sealed. This yields a secondary battery 1 having a configuration in which multiple battery cells 2 are stacked.

[0049] In the example above, we described the case where the secondary battery 1 has multiple battery cells 2. However, the secondary battery 1 does not necessarily have to have multiple battery cells 2; it may be composed of a single battery cell 2.

[0050] The first embodiment has been described above. The configuration and effects of the secondary battery 1 according to this embodiment can be summarized as follows.

[0051] The secondary battery 1 according to this embodiment comprises a porous body 5 having an electrolyte region 6 on which a solid electrolyte is supported and an unsupported region 7 on which the solid electrolyte is not supported, and a positive electrode 9 and a negative electrode 8 arranged above and below the porous body 5 so as to sandwich the electrolyte region 6. The unsupported region 7 has a non-communicating region 11 on both sides of the porous body 5 in the stacking direction that are not in communication. The non-communicating region 11 is continuous with the outer periphery of the electrolyte region 6 and is provided in a position that surrounds the electrolyte region 6. With this configuration, since the region surrounding the electrolyte region 6 is the non-communicating region 11, the growth of lithium dendrites that wrap around the edges of the electrolyte region 6 is suppressed. Therefore, a short circuit between the positive electrode 9 and the negative electrode 8 can be prevented.

[0052] Second Embodiment Next, a second embodiment will be described. Note that the same configuration as in the first embodiment can be adopted, and this will not be explained.

[0053] Figure 3 is a schematic cross-sectional view showing the main part of the secondary battery 1 according to the second embodiment. In this embodiment, the width of the non-communication region 11 (A in Figure 3) is greater than or equal to the thickness of the positive electrode 9 (T in Figure 3).

[0054] The secondary battery 1 may be subjected to vibrations or other forces. As a result, the negative electrode current collector foil 3 and the porous body 5 may bend towards the positive electrode 9, and the negative electrode current collector foil 3 may move closer to the positive electrode 9. When the negative electrode current collector foil 3 moves closer to the positive electrode 9, a short circuit caused by lithium dendrites becomes more likely.

[0055] However, in this embodiment, since the width of the non-communicating region 11 is greater than or equal to the thickness of the positive electrode 9, even if the negative electrode current collector foil 3 and the porous body 5 are bent, the positive electrode 9 and the negative electrode current collector foil 3 are still separated by the non-communicating region 11. Therefore, even if the negative electrode current collector foil 3 and the porous body 5 are bent, a short circuit due to lithium dendrites is unlikely to occur.

[0056] Third Embodiment Next, a third embodiment will be described. The fact that the same configuration as the first embodiment can be adopted will not be explained.

[0057] Figure 4 is a schematic cross-sectional view showing a secondary battery 1 according to the third embodiment. As shown in Figure 4, in this embodiment, the entire area of ​​the non-supported region 7 in the porous body 5 is a non-communicating region 11. That is, there is no communicative region 10 in the non-supported region 7.

[0058] According to this embodiment, since the entire unsupported region 7 is a non-communicating region 11, the growth of lithium dendrites that wrap around the electrolyte region 6 is more reliably prevented.

[0059] Fourth Embodiment Next, we will describe the fourth embodiment. We will omit the explanation of how the same configuration as the previously described embodiments can be adopted.

[0060] Figure 5 is a schematic cross-sectional view showing a secondary battery 1 according to the fourth embodiment. As shown in Figure 5, the thickness of the porous body 5 is modified in this embodiment. Specifically, the thickness of the porous body 5 in the non-supported region 7 (T2 in the figure) is greater than the thickness of the porous body 5 in the electrolyte region 6 (T1 in the figure).

[0061] In this embodiment, the thickness of the structure (i.e., the porous body 5) separating the positive electrode side and the negative electrode side is increased in the region surrounding the electrolyte region 6. Therefore, the growth of lithium dendrites is more easily hindered. Consequently, short circuits can be prevented more reliably.

[0062] Fifth Embodiment Next, we will describe the fifth embodiment. Note that we will omit explanations regarding the fact that the same configuration as the previously described embodiments can be adopted.

[0063] Figure 6 is a schematic cross-sectional view showing a secondary battery 1 according to the fifth embodiment. As shown in Figure 6, a covering material 12 is provided on the upper and lower surfaces of the porous body 5 in the non-communicating region 11. That is, in the non-communicating region 11, the communicating holes of the porous body 5 are blocked by the covering material 12. The covering material 12 is not particularly limited, but for example, tape material (such as polyimide film), coating agent, and inorganic particle material can be used.

[0064] In this embodiment, in the region outside the electrolyte region 6, the thickness of the porous body 5 is substantially increased by the covering material 12. Therefore, similar to the fourth embodiment, the growth of lithium dendrites is easily hindered. As a result, short circuits can be prevented more reliably.

[0065] In the example shown in Figure 6, the coating material 12 is provided on both the upper and lower surfaces of the porous body 5. However, the coating material 12 may be provided on only one side of the porous body 5. In this case, since lithium dendrites grow from the negative electrode 8 side, it is preferable that the coating material 12 is provided on the negative electrode 8 side of the porous body 5.

[0066] Sixth Embodiment Next, a sixth embodiment will be described. This embodiment is a modification of the fifth embodiment. The fact that the same configuration as the fifth embodiment can be adopted will not be explained.

[0067] Figure 7 is a schematic cross-sectional view showing a secondary battery 1 according to the sixth embodiment. As shown in Figure 7, in this embodiment, the covering material 12 is arranged to cover the boundary between the electrolyte region 6 and the unsupported region 7.

[0068] At the edges of the electrolyte region 6, the binding force of the solid electrolyte in the porous body 5 often weakens. As a result, the solid electrolyte may detach from the porous body 5, creating a space that penetrates the porous body 5 vertically. This can cause lithium dendrites to grow vertically through the porous body 5, potentially leading to a short circuit between the positive electrode 9 and the negative electrode 8.

[0069] However, according to this embodiment, the boundary between the electrolyte region 6 and the non-supported region 7 is protected by the covering material 12. Therefore, the detachment of the solid electrolyte can be prevented, and short circuits can be prevented more reliably.

[0070] Seventh Embodiment Next, a seventh embodiment will be described. Note that the same configuration as in the previously described embodiments can be adopted, and this will not be explained. In this embodiment, at least one side surface of the positive electrode 9 and the negative electrode 8 is covered, at least partially, by the porous body 5.

[0071] Figure 8 is a schematic cross-sectional view showing an example of a secondary battery 1 according to this embodiment. In this example, one porous body 5 is used in common between two adjacent battery cells 2. Specifically, each porous body 5 is bent so as to wrap around the positive electrode current collector foil 4 and the positive electrode 9 (see folded portion 14 in the figure). The lower portion of each porous body 5 is sandwiched between the positive electrode 9 and the negative electrode 8 in the lower battery cell 2, and the upper portion is sandwiched between the positive electrode 9 and the negative electrode 8 in the upper battery cell 2. In addition, the outer periphery of the upper portion of each porous body 5 overlaps with the outer periphery of the lower portion. The overlapping outer peripheries are then closed together with adhesive 13 (e.g., tape material). In the portion where the positive electrode current collector foil 4 is present, the outer periphery of each porous body 5 is adhered to the positive electrode current collector foil 4. With this configuration, the side surface of the positive electrode 9 is entirely covered by each porous body 5.

[0072] With the configuration described above, the negative electrode current collector foil 3 and the positive electrode current collector foil 4 are separated by the porous body 5. Therefore, even if the negative electrode current collector foil 3 or the positive electrode current collector foil 4 bends, they will not come into contact with each other. Thus, short circuits caused by contact between the negative electrode current collector foil 3 and the positive electrode current collector foil 4 can be prevented. In addition, lithium dendrites can be prevented from growing around the edges of the porous body 5.

[0073] In the example shown in Figure 8, the porous body 5 is configured to cover the side surface of the positive electrode 9, but the porous body 5 may also be bent to cover the side surface of the negative electrode 8 instead of the positive electrode 9.

[0074] Next, another example of the secondary battery according to this embodiment will be described. Figure 9 is a schematic diagram showing another example of the secondary battery 1 according to this embodiment. In the example shown in Figure 9, the porous bodies 5 in adjacent battery cells 2 are bonded together by heat fusion at their outer periphery (see heat fusion portion 15 in Figure 9). Specifically, the outer periphery of the porous bodies 5 of the upper and lower battery cells 2 are joined together by heat fusion in the portion excluding the portion where the negative electrode current collector foil 3 and the positive electrode current collector foil 4 are provided.

[0075] In the configuration shown in Figure 9, similar to the configuration shown in Figure 8, at least one side of the positive electrode 9 and the negative electrode 8 is covered by the porous material 5, at least in part. This prevents short circuits caused by contact between the negative electrode current collector foil 3 and the positive electrode current collector foil 4. Furthermore, it provides more reliable protection against short circuits caused by lithium dendrites.

Claims

1. A porous body having an electrolyte region on which a solid electrolyte is supported and an unsupported region on which the solid electrolyte is not supported, A positive electrode and a negative electrode are arranged above and below the porous body so as to sandwich the electrolyte region. Equipped with, The non-supported region has non-communicating regions where both sides of the porous body in the stacking direction are not in communication. The non-communicating region is continuous with the outer periphery of the electrolyte region and is located in a position surrounding the electrolyte region. When viewed along the stacking direction, the outer shape of the electrolyte region is located outside the outer shapes of the positive electrode and the negative electrode. Secondary battery.

2. A secondary battery according to claim 1, The width of the non-communicating region is greater than or equal to the thickness of the positive electrode. Secondary battery.

3. A secondary battery according to claim 1 or 2, The entire area of ​​the non-supported region is the non-communicating region. Secondary battery.

4. A secondary battery according to claim 1 or 2, The thickness of the porous material in the non-supported region is greater than the thickness of the porous material in the electrolyte region. Secondary battery.

5. A secondary battery according to claim 1 or 2, The non-communicating region is formed by a covering material placed on the upper or lower surface of the non-supported region. Secondary battery.

6. A secondary battery according to claim 5, The covering material is arranged to cover the boundary between the electrolyte region and the non-supported region. Secondary battery.

7. A secondary battery according to claim 1 or 2, At least one side surface of the positive electrode and the negative electrode is covered at least in part by the porous material. Secondary battery.

8. A secondary battery according to claim 1 or 2, The porous material is a nonwoven fabric. Secondary battery.

9. A secondary battery according to claim 1 or 2, The porous material is a porous sheet having interconnected holes, The non-communicating region is formed by partially heating and melting the porous sheet to block the communication holes. Secondary battery.

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