Secondary battery

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

secondary battery

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

[0002] Secondary batteries are known in which a positive electrode and a negative electrode are provided on either side of an electrolyte layer, and charging and discharging are performed by the movement of lithium ions between the positive electrode and the negative electrode. Among such secondary batteries, those having a structure in which a solid electrolyte is supported on a sheet-like porous body are known. By supporting the solid electrolyte on the porous body, a thin but self-supporting electrolyte layer can be obtained.

[0003] A related technology is disclosed, for example, in Patent Document 1 (JP 2021-533542A). Patent Document 1 discloses a method for producing a solid electrolyte membrane for an all-solid-state battery, including the steps of: sequentially stacking a first protective layer, a film-like first solid electrolyte material, a porous substrate, a film-like second solid electrolyte material, and a second protective layer to prepare a laminate structure; pressurizing the laminate structure to force the first solid electrolyte material and the second solid electrolyte material into the porous substrate and fill the pores of the porous substrate with the solid electrolyte material; and removing the first protective layer and the second protective layer, wherein the pressurization is performed using a roll press method. This solid electrolyte membrane is a composite of a porous polymer material such as a nonwoven fabric and a solid electrolyte material, and therefore can be produced in a thin film form of 70 μm or less while maintaining excellent strength, which is advantageous for improving the energy density of the battery.

[0004] In secondary batteries that use lithium ions for charging and discharging, lithium dendrites may grow from the negative electrode during charging. If the lithium dendrites grow around the edge of the electrolyte layer, a short circuit may occur between the positive and negative electrodes. This problem may also occur in secondary batteries that have a configuration in which a solid electrolyte is supported on a porous body.

[0005] Therefore, an object of the present invention is to provide a technique capable of preventing short circuits caused by lithium dendrites in a secondary battery having a structure in which a solid electrolyte is supported on a porous body.

[0006] FIG. 1 is a cross-sectional view schematically showing a secondary battery according to a first embodiment. FIG. 2 is a plan view showing a porous body. FIG. 3 is a cross-sectional view schematically showing a secondary battery according to a second embodiment. FIG. 4 is a cross-sectional view schematically showing a secondary battery according to a third embodiment. FIG. 5 is a cross-sectional view schematically showing a secondary battery according to a fourth embodiment. FIG. 6 is a cross-sectional view schematically showing a secondary battery according to a fifth embodiment. FIG. 7 is a cross-sectional view schematically showing a secondary battery according to a sixth embodiment. FIG. 8 is a cross-sectional view schematically showing an example of a secondary battery according to a seventh embodiment. FIG. 9 is a schematic view showing another example of a secondary battery according to the seventh embodiment.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] First Embodiment A secondary battery 1 according to this embodiment is a so-called all-solid-state battery that is charged and discharged by the movement of lithium ions.

[0009] (Overview) Fig. 1 is a cross-sectional view that schematically shows a secondary battery 1 according to this embodiment. As shown in Fig. 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 disposed 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 disposed in a sheet-like porous body 5, and is a region in 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 disposed above and below the porous body 5, sandwiching the electrolyte region 6 therebetween. The positive electrode 9 is disposed between the electrolyte region 6 and the positive electrode current collector foil 4, and the negative electrode 8 is disposed between the electrolyte region 6 and the negative electrode current collector foil 3.

[0011] When viewed along the stacking direction, the outer shapes of the positive electrode 9, the negative electrode 8, and the electrolyte region 6 are generally the same. However, these do not need to be perfectly aligned, and some misalignment is acceptable.

[0012] The secondary battery 1 generates power in a region where the positive electrode 9, the negative electrode 8, and the electrolyte region 6 overlap (hereinafter, this region may be referred to as a power generation region). Specifically, during charging, lithium ions are conducted from the positive electrode 9 side to the negative electrode 8 side through the electrolyte region 6, and the lithium ions are absorbed on the negative electrode 8 side. Alternatively, lithium is deposited on the negative electrode 8 side. On the other hand, during discharging, lithium ions move from the negative electrode 8 side to the positive electrode 9 side, and lithium is absorbed in the positive electrode 9.

[0013] In such a secondary battery 1, as described above, there is a possibility that lithium dendrites will grow from the edge of the negative electrode 8. If the lithium dendrites grow so as to wrap around the edge 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 configuration of the porous body 5 is devised.

[0014] 2 is a plan view showing the porous body 5. As shown in FIGS. 1 and 2, each porous body 5 has an electrolyte region 6 and a non-loading region 7.

[0015] As described above, the electrolyte region 6 is a region in which a solid electrolyte is supported, and is provided in the center of each porous body 5. In the electrolyte region 6, each porous body 5 has communicating holes to enable lithium ion conduction. The communicating holes are holes that penetrate each porous body 5. The solid electrolyte is supported in these communicating holes.

[0016] On the other hand, the non-supported region 7 is a region where no solid electrolyte is supported. The non-supported region 7 is provided on the outer periphery of each porous body 5 and surrounds the electrolyte region 6.

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

[0018] The communication region 10 is a region in which both sides of the porous body 5 communicate with each other in the stacking direction. Specifically, both sides of the porous body 5 communicate with each other via communication holes.

[0019] On the other hand, the non-communicating region 11 is a region in which both sides of the porous body 5 are not connected in the stacking direction. The non-communicating region 11 is provided at a position surrounding the electrolyte region 6 and is continuous with the outer periphery of the electrolyte region 6. The non-communicating region 11 may be, for example, a region in which the porous body 5 itself has no communicating holes. Alternatively, the non-communicating region 11 may be a region in which the porous body 5 itself has communicating holes, but the communicating holes are blocked.

[0020] According to the above-described configuration, the provision of the non-communicating region 11 can prevent the growth of lithium dendrites that would otherwise wrap around the edge of the electrolyte region 6. If the non-communicating region 11 were not provided, that is, if the top and bottom of the porous body 5 were connected in the region outside the electrolyte region 6, lithium dendrites would likely grow to penetrate the porous body 5. This could result in a problem of short-circuiting between the negative electrode 8 and the positive electrode 9 due to lithium dendrites. However, in this embodiment, the provision of the non-communicating region 11 outside the electrolyte region 6 can prevent the growth of lithium dendrites that would short-circuit the positive electrode 9 and the negative electrode 8.

[0021] Next, each part of the secondary battery 1 according to this embodiment will be described in detail.

[0022] (Porous Body) The material of the porous body 5 is not particularly limited as long as it can support a solid electrolyte. For example, the porous body 5 can be produced using the materials and methods described below.

[0023] First, a porous sheet having communicating holes is prepared. Examples of the porous sheet having communicating holes include nonwoven fabric, porous separators, and sheets with communicating holes formed by lithography. Examples of the nonwoven fabric include polyester nonwoven fabric, polyethylene nonwoven fabric, and cellulose fiber nonwoven fabric.

[0024] Next, a slurry containing a solid electrolyte is applied to the area where the electrolyte region 6 is to be formed, and then dried, thereby forming the electrolyte region 6.

[0025] In addition, the communicating holes are blocked around the electrolyte region 6 to form the non-communicating region 11. For example, if a material that melts when heated is used for the porous sheet, the communicating holes can be blocked by partially heating and melting the porous sheet. Alternatively, the communicating holes can be blocked by filling the porous sheet with a resin material or the like so that the communicating holes are filled. Alternatively, as will be described in the embodiments below, the communicating holes can be blocked by placing a coating material on the upper or lower surface of the porous sheet.

[0026] The above is an example of a method for producing the porous body 5 when using a porous sheet having continuous pores.

[0027] On the other hand, the porous body 5 can also be produced using a porous sheet that does not originally have communicating pores (for example, a porous sheet having closed pores). In this case, communicating pores are first formed only in some regions (regions that are to become the electrolyte region 6 and the communicating region 10) by lithography or the like. Next, a slurry containing a solid electrolyte is applied to the region that is to become the electrolyte region 6 and dried. In this way, the electrolyte region 6 is formed. Even using such a method, it is possible to obtain a porous body 5 that has the electrolyte region 6, the communicating region 10, and the non-communicating region 11.

[0028] There is no particular limitation on the thickness of the porous body 5. 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 may be any solid electrolyte as long as it is solid and functions as an electrolyte. For example, a sulfide solid electrolyte and an oxide solid electrolyte can be used as the solid electrolyte. Preferably, the solid electrolyte is a sulfide solid electrolyte. As the sulfide solid electrolyte, for example, an LPS-based (e.g., Argyrodite (Li ６ P.S. ５ Cl), and LGPS systems (e.g., Li １０ GeP ２ S １２ ) materials can be mentioned.

[0030] (Positive Electrode) The positive electrode 9 may be formed of a material that can release lithium ions during charging and absorb lithium ions during discharging. The positive electrode 9 may be formed of a material that includes, for example, a resin binder and a positive electrode active material dispersed in the resin binder. For example, a lithium metal composite oxide may be used as the positive electrode active material. For example, the lithium metal composite oxide may be LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , and Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ , and LiNi ０．５ Mn １．５ O ４ spinel-type compounds such as LiFePO ４ , and LiMnPO ４ Olivine type compounds such as Li ２ FeSiO ４ , and Li ２ MnSiO ４ In addition, Si-containing compounds such as Li ４ Ti ５ O １２ Also, the following can be used.

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

[0032] (Negative Electrode) The negative electrode 8 may be configured to absorb lithium (or precipitate lithium) during charging and release lithium ions during discharging. For example, the negative electrode 8 may be formed from a material containing a resin binder and a negative electrode active material dispersed in the resin binder. Examples of the negative electrode active material that can be used include 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 "total deposition type" secondary battery. A total deposition type secondary battery is a battery configured such that, in a fully discharged state, the negative electrode side does not contain lithium as a negative electrode active material, and lithium ions move from the positive electrode side to the negative electrode side during charging, causing lithium metal to deposit 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 the negative electrode 8, and therefore is included in the secondary battery 1 of the present invention.

[0034] In addition, in the all-precipitation type secondary battery 1, a negative electrode intermediate layer may be disposed 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 the lithium-reactive material include a material capable of absorbing and releasing lithium ions during charging and a metal capable of alloying with lithium during charging.

[0035] The material capable of absorbing and releasing lithium ions is not particularly limited, but a carbon material is preferred. Specific examples of the carbon material include carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.), carbon nanotubes (CNT), graphite, hard carbon, etc. Among these, carbon black is preferred, and at least one selected from the group consisting of acetylene black, Ketjen Black (registered trademark), furnace black, channel black, and thermal lamp black is more preferred.

[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, and Ag is more preferred.

[0037] The lithium-reactive material may be used alone or in combination of two or more. In a combination of two or more, a material capable of absorbing and releasing lithium ions and a metal capable of alloying with lithium are also preferred. This ensures sufficient strength and lithium ion conductivity of the negative electrode intermediate layer. More specifically, nanoparticles made of In, Si, Sn, and Ag are preferably used in combination with carbon black, and nanoparticles made of Ag are more preferably used in combination with carbon black. When a material capable of absorbing and releasing lithium ions and a metal capable of alloying with lithium are used in combination, the blending ratio (mass ratio) of the material capable of absorbing and releasing lithium ions to the metal capable of alloying with lithium is not particularly limited, but is preferably 10:1 to 1:1, more preferably 5:1 to 2:1.

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

[0039] The negative electrode intermediate layer may be composed solely of a lithium reactive material as long as a freestanding film can be produced using only the lithium reactive material, but may also contain a binder as necessary. The type of binder is not particularly limited, and binders known in the art can be appropriately used. Examples include polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose.

[0040] The binder content in the negative electrode intermediate layer is not particularly limited, but is preferably in the range of 1 to 15 mass%, more preferably in the range of 5 to 10 mass%. If the binder content is 1 mass% or more, a negative electrode intermediate layer with sufficient strength can be formed. If the binder content is 15 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 function of the negative electrode intermediate layer can be fully exhibited. When the thickness of the negative electrode intermediate layer is 50 μm or less, a 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 negative electrode current collector foil 3 are provided to electrically connect the secondary battery 1 to an external device. As shown in FIG. 1 , the positive electrode current collector foil 4 and negative electrode current collector foil 3 each extend so as to protrude laterally from the power generation region. The positive electrode current collector foil 4 and negative electrode current collector foil 3 are each formed of a conductive thin film. For example, an aluminum foil can be used as the positive electrode current collector foil 4. For example, a stainless steel thin film or a copper thin film can be used as the negative electrode current collector foil 3.

[0043] (Manufacturing Example) There are no particular limitations on the manufacturing method of the secondary battery 1 according to this embodiment. An example of a specific manufacturing method of the secondary battery 1 according to this embodiment will be described below.

[0044] [Fabrication of Positive Electrode] Predetermined amounts of positive electrode active material, sulfide solid electrolyte, conductive additive, binder, and xylene are weighed and mixed to prepare a slurry. The prepared slurry is applied to a carbon-coated aluminum foil (positive electrode current collector foil 4). The slurry is applied to both sides in a predetermined area. After application, the coating is dried. This results in a positive electrode current collector foil 4 on which a positive electrode 9 having a thickness of 200 μm (100 μm on each side) is formed.

[0045] [Preparation of Porous Body Supporting Solid Electrolyte] Predetermined amounts of sulfide solid electrolyte, binder, and xylene are weighed and mixed to prepare a slurry. The prepared slurry is directly applied to a 40 μm porous sheet (having interconnecting pores) and dried. In this way, the solid electrolyte is supported on the porous sheet, forming the electrolyte region 6. Furthermore, a coating material is placed in a predetermined region to form the non-interconnecting region 11. In this way, the porous body 5 is obtained.

[0046] [Fabrication of Negative Electrode] A predetermined amount of negative electrode active material, binder, and NMP (N-methylpyrrolidone) are weighed and mixed to prepare a slurry. 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, the foil is dried. This results in a negative electrode current collector foil 3 on which a 100 μm-thick negative electrode 8 (50 μm on each side) is formed.

[0047] [Fabrication of Positive Electrode / Solid Electrolyte / Negative Electrode Laminate] The porous body 5 and the negative electrode current collector foil 3 on which the negative electrode 8 is formed are placed on top and bottom of the positive electrode current collector foil 4 on which the positive electrode 9 formed by the above-mentioned procedure is formed. Then, a laminate in which these are stacked is obtained by roll pressing.

[0048] [Fabrication of Cell Stack] Furthermore, multiple stacks of the obtained stacks are stacked. After that, an aluminum tab is bonded to the positive electrode current collector foil 4, and a Ni-plated copper tab is bonded to the negative electrode current collector foil 3 using an ultrasonic welder. Finally, the stack is placed in an aluminum laminate film and vacuum-sealed. This results in a secondary battery 1 having a configuration in which multiple battery cells 2 are stacked.

[0049] In the above example, the secondary battery 1 has been described as having a plurality of battery cells 2. However, the secondary battery 1 does not necessarily have to have a plurality of battery cells 2, and the secondary battery 1 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 includes a porous body 5 having an electrolyte region 6 supporting a solid electrolyte and a non-supported region 7 not supporting a solid electrolyte, and a positive electrode 9 and a negative electrode 8 disposed above and below the porous body 5 so as to sandwich the electrolyte region 6. The non-supported region 7 has a non-communicating region 11, which is not connected to both sides of the porous body 5 in the stacking direction. The non-communicating region 11 is continuous with the outer periphery of the electrolyte region 6 and is positioned to surround the electrolyte region 6. With this configuration, the region surrounding the electrolyte region 6 is the non-communicating region 11, which suppresses the growth of lithium dendrites that would otherwise wrap around the edge of the electrolyte region 6. This prevents short-circuiting between the positive electrode 9 and the negative electrode 8.

[0052] Second Embodiment Next, a second embodiment will be described. Note that a description of the fact that the same configuration as the first embodiment can be adopted will be omitted.

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

[0054] The secondary battery 1 may be subjected to vibrations or the like. As a result, the negative electrode current collector foil 3 and the porous body 5 may bend toward the positive electrode 9, causing the negative electrode current collector foil 3 to approach the positive electrode 9. When the negative electrode current collector foil 3 approaches the positive electrode 9, a short circuit due to lithium dendrites is likely to occur.

[0055] However, in this embodiment, the width of the non-communicating region 11 is equal to or greater than the thickness of the positive electrode 9, and therefore 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 same configuration as in the first embodiment can be adopted, and a description thereof will be omitted.

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

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

[0059] Fourth Embodiment Next, a fourth embodiment will be described. In the fourth embodiment, the same configuration as in the above-described embodiments can be adopted, and therefore the description will be omitted.

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

[0061] According to this embodiment, the thickness of the structure separating the positive electrode side and the negative electrode side (i.e., the porous body 5) is increased in the region surrounding the electrolyte region 6. This makes it easier to prevent the growth of lithium dendrites, thereby more reliably preventing short circuits.

[0062] Fifth Embodiment Next, a fifth embodiment will be described. Note that, insofar as the same configuration as in the previously described embodiments can be adopted, a description thereof will be omitted.

[0063] Fig. 6 is a schematic cross-sectional view showing a secondary battery 1 according to a fifth embodiment. As shown in Fig. 6, covering materials 12 are provided on the upper and lower surfaces of the porous body 5 in the non-communicating regions 11. That is, in the non-communicating regions 11, the communicating holes of the porous body 5 are blocked by the covering materials 12. The covering materials 12 are not particularly limited, and examples thereof include tape materials (such as polyimide films), coating agents, and inorganic particle materials.

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

[0065] 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 surface 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 surface of the porous body 5 facing the negative electrode 8.

[0066] Sixth Embodiment Next, a sixth embodiment will be described. This embodiment is a modification of the fifth embodiment. A description of the fact that the same configuration as the fifth embodiment can be adopted will be omitted.

[0067] 7 is a schematic cross-sectional view showing a secondary battery 1 according to a sixth embodiment. As shown in FIG. 7 , in this embodiment, a coating material 12 is disposed so as to cover the boundary between the electrolyte region 6 and the non-loaded region 7.

[0068] At the end of the electrolyte region 6, the binding strength of the solid electrolyte in the porous body 5 is often weak. As a result, the solid electrolyte may fall off from the porous body 5, forming a space that penetrates the porous body 5 from top to bottom. This may cause lithium dendrites to grow so as to penetrate the porous body 5 from top to bottom, potentially causing 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-electrolyte region 7 is protected by the coating material 12. Therefore, the solid electrolyte can be prevented from falling off, and short circuits can be more reliably prevented.

[0070] Next, a seventh embodiment will be described. It should be noted that the same configuration as in the previously described embodiments can be employed, and therefore the description will be omitted. In this embodiment, at least one side surface of the positive electrode 9 and the negative electrode 8 is at least partially covered with a porous body 5.

[0071] FIG. 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 shared between two adjacent battery cells 2. Specifically, each porous body 5 is folded 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 of the lower battery cell 2, and the upper portion is sandwiched between the positive electrode 9 and the negative electrode 8 of the upper battery cell 2. Furthermore, the outer periphery of the upper portion of each porous body 5 overlaps the outer periphery of the lower portion. The overlapping outer peripheries are sealed with adhesive 13 (e.g., tape). In the area 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] According to the above-described configuration, 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 is bent, the two do not come into contact with each other. This makes it possible to prevent a short circuit due to contact between the negative electrode current collector foil 3 and the positive electrode current collector foil 4. It is also possible to prevent lithium dendrites from growing around the edges of the porous body 5.

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

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

[0075] 9 , similarly to the configuration shown in Fig. 8 , at least one side surface of the positive electrode 9 and the negative electrode 8 is at least partially covered with the porous body 5. This makes it possible to prevent a short circuit due to contact between the negative electrode current collector foil 3 and the positive electrode current collector foil 4. Furthermore, it is possible to more reliably prevent a short circuit due to lithium dendrites.

Claims

1. A porous body having an electrolyte region in which a solid electrolyte is supported and a non-supported region in which the solid electrolyte is not supported; A positive electrode and a negative electrode are disposed above and below the porous body so as to sandwich the electrolyte region; Equipped with the non-supporting region has a non-connected region where both sides of the porous body in the stacking direction are not connected to each other, the non-communicating region is continuous with an outer periphery of the electrolyte region and is provided at 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. 2. The secondary battery according to claim 1, The width of the non-communicating region is equal to or greater than the thickness of the positive electrode. Secondary battery.

3. 3. The secondary battery according to claim 1, The entire non-supporting region is the non-communicating region. Secondary battery.

4. 3. The secondary battery according to claim 1, the thickness of the porous body in the non-support region is greater than the thickness of the porous body in the electrolyte region; Secondary battery.

5. 3. The secondary battery according to claim 1, Furthermore, A coating material is disposed on the upper surface or the lower surface of the porous body in the non-communicating region. Secondary battery.

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

7. 3. The secondary battery according to claim 1, At least one side surface of the positive electrode and the negative electrode is at least partially covered with the porous body. Secondary battery.

8. 3. The secondary battery according to claim 1, The porous body is a nonwoven fabric. Secondary battery.