Support for secondary battery, solid electrolyte sheet, and secondary battery

Abstract

Provided is a support for a secondary battery capable of reducing internal resistance of a solid electrolyte layer, as well as interfacial resistances between a positive electrode and a solid electrolyte sheet and between a negative electrode and the solid electrolyte sheet. The support for a secondary battery comprises at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, and has an elastic modulus of 0.3 to 10 GPa.

Description

Support for secondary batteries, solid electrolyte sheet, and secondary battery

[0001] The present invention relates to a support for a secondary battery, a solid electrolyte sheet, and a secondary battery.

[0002] Lithium-ion secondary batteries generally have a configuration in which a liquid electrolyte is held in a separator that isolates the positive and negative electrodes. Lithium-ion secondary batteries mainly use organic electrolytes as the liquid electrolyte. Because organic electrolytes are liquids, there are concerns about leakage and problems caused by flammability. Therefore, development is underway on secondary batteries that use a highly safe solid electrolyte instead of an organic electrolyte (hereinafter referred to as all-solid-state batteries). All-solid-state batteries are attracting attention as a secondary battery with superior safety because, since the electrolyte is solid, there is no leakage, and they are more flame-retardant and heat-resistant compared to liquid electrolytes. Due to their high safety, all-solid-state batteries are being mass-produced in small sizes for use in wearable devices that come into direct contact with the skin.

[0003] Solid-state batteries have high heat resistance due to their solid electrolyte, allowing them to be used in high-temperature environments and thus eliminating the need for cooling devices. Therefore, solid-state batteries offer advantages in improving energy density per unit volume of the battery pack. Consequently, further enlargement of solid-state batteries is expected, particularly for applications such as electric vehicles.

[0004] In all-solid-state batteries, a solid electrolyte layer, rather than a separator holding electrolyte, is interposed between the positive and negative electrodes. During charging, ions (hereinafter referred to as carrier ions) conduct between the positive electrode, solid electrolyte layer, and negative electrode. Conversely, during discharging, they travel from the negative electrode through the solid electrolyte layer to the positive electrode. Thus, all-solid-state batteries require the formation of carrier ion pathlines in the thickness direction of the solid electrolyte layer. In addition to lithium ions, various other ion species, such as less expensive sodium ions, are being considered as carrier ions, from the perspective of stable resource supply.

[0005] Furthermore, all-solid-state batteries require a solid electrolyte layer that prevents short circuits between the positive electrode active material and the negative electrode active material. While a thicker solid electrolyte layer is advantageous for preventing short circuits in all-solid-state batteries, it leads to a decrease in volumetric energy density and an increase in internal resistance, so a thinner layer is desirable.

[0006] Methods for forming solid electrolyte layers include mixing a solid electrolyte with a binder and rolling it under heat to form a sheet, or coating a solid electrolyte slurry onto an electrode and drying it. However, when forming large solid electrolyte layers, the rolling method under heat is likely to result in cracks and fissures. Similarly, the slurry coating method can result in cracks due to strain during drying, making it difficult to form a stable, thin, and uniform solid electrolyte layer.

[0007] To solve the above problems, an all-solid-state battery has been proposed that uses an integrated solid electrolyte sheet, in which a solid electrolyte is incorporated into a membrane-like sheet (hereinafter referred to as the support). Various nonwoven fabric substrates have been proposed as supports for all-solid-state batteries. For example, a fiber aggregate containing polyolefin resin fibers has been proposed, with a basis weight (unit: g / m²). ２ A technology relating to a support for a solid electrolyte membrane having a tensile strength (unit: N / 50 mm) of greater than 0.5 has been disclosed (see, for example, Patent Document 1). This technology makes it possible to realize a solid electrolyte membrane in which clumps of solid electrolyte particles are less likely to fall off, thus providing a solid electrolyte membrane with a small thickness and a solid battery with low internal resistance.

[0008] Furthermore, technologies relating to supports having an elastic recovery rate of 30 to 99% have been disclosed (see, for example, Patent Document 2). The elastic recovery rate of the support greatly affects the conformability of the electrolyte sheet to the electrode interface. For this reason, Patent Document 2 discloses that the higher the elastic recovery rate of the support, the better the sheet conforms to the electrode interface, and the lower the electrical resistance between the electrolyte sheet surface and the electrode.

[0009] Furthermore, a technology relating to a support for a lithium-ion secondary battery, which is included in a solid electrolyte layer and whose rigidity in the longitudinal and transverse directions after heat treatment is in the range of 5 to 250 mN, has been disclosed (see, for example, Patent Document 3). By using this support, the non-uniform stress applied to the solid electrolyte layer can be withstood, and deformation of the support is suppressed. As a result, the lithium ion pass line inside the pre-formed solid electrolyte layer is maintained, and the increase in internal resistance due to the pressurized integration of the positive electrode, solid electrolyte layer, and negative electrode can be suppressed, as disclosed in Patent Document 3.

[0010] Other related technologies include a technique that optimizes the elasticity of separators for aluminum electrolytic capacitors, enabling flexible response to various forces in various directions applied to the separator (for example, Patent Document 4). This technology discloses an aluminum electrolytic capacitor separator with a tensile modulus of 500 to 2000 MPa. The tensile modulus indicates how easily a material deforms in the elastic deformation region; the lower the tensile modulus, the easier it is to expand and contract with a weaker force. Conversely, the higher the tensile modulus, the stronger the force required to achieve deformation.

[0011] Japanese Patent Publication No. 2021-28869, International Publication No. 2022 / 220186, Japanese Patent Publication No. 2023-30824, Japanese Patent Publication No. 2022-35309

[0012] However, in the technologies described in Patent Documents 1 and 2, the resistance and interfacial resistance between the positive and negative electrodes and the solid electrolyte layer may be high due to the disruption of the carrier ion pass line.

[0013] Furthermore, in the technology described in Patent Document 3, although the support has resistance to non-uniform stress in the planar direction after the formation of the solid electrolyte layer, the stress response to the solid electrolyte layer due to expansion and contraction of the positive and negative electrodes may be poor. As a result, the pass line of the formed carrier ions may be cut, leading to increased resistance.

[0014] In addition, within the range of tensile modulus described in Patent Document 4, which is related technology, the conformability of the electrode to the solid electrolyte layer is considered to be excellent. However, Patent Document 4 incorporates binder fibers that form a film at fiber entanglement points and between fibers under moist heat conditions. As mentioned above, these film-forming binder fibers do not maintain their fiber shape and fill the voids inside the support. Furthermore, if a large amount of binder fibers that do not maintain their fiber shape are included, the density becomes high. As a result, the penetration of the solid electrolyte slurry into the nonwoven fabric substrate becomes insufficient, and uniform filling of the solid electrolyte into the support was sometimes difficult.

[0015] To solve the above-mentioned problems, the present invention provides a support for a secondary battery that can reduce the internal resistance of the solid electrolyte layer and the interfacial resistance between the positive electrode, the negative electrode and the solid electrolyte sheet, a solid electrolyte sheet using this support, and a secondary battery using this support.

[0016] The secondary battery support of the present invention is a support for holding a solid electrolyte of a secondary battery, comprising at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, and having an elastic modulus of 0.3 to 10 GPa.

[0017] Furthermore, the solid electrolyte sheet of the present invention comprises a membrane-like support and a solid electrolyte held by the support. The support consists of at least one selected from paper and nonwoven fabric, and includes at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, with an elastic modulus of 0.3 to 10 GPa.

[0018] Furthermore, the secondary battery of the present invention comprises a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the solid electrolyte sheet is made of at least one selected from paper and nonwoven fabric, and comprises a support having an elastic modulus of 0.3 to 10 GPa, which includes at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, and a solid electrolyte held in the support.

[0019] According to the present invention, it is possible to provide a support for a secondary battery that can reduce the internal resistance of the solid electrolyte layer and the interfacial resistance between the positive electrode, the negative electrode and the solid electrolyte sheet, a solid electrolyte sheet using this support, and a secondary battery using this support.

[0020] The following describes examples of embodiments for carrying out the present invention, but the present invention is not limited to these examples. The description will be in the following order: 1. Embodiment of a support for a secondary battery (first embodiment) 2. Embodiment of a secondary battery (second embodiment)

[0021] <1. Embodiment of a Support for Secondary Batteries (First Embodiment)> A specific embodiment of the support for secondary batteries will be described below. The support for secondary batteries in this embodiment (hereinafter also simply referred to as "support") is a support for holding the solid electrolyte of a secondary battery, and consists of at least one selected from paper and nonwoven fabric, and includes at least one selected from polyester fibers, cellulose fibers and polyamide fibers, with an elastic modulus of 0.3 to 10 GPa. In this disclosure, the numerical range indicated by "~" includes the numerical values ​​indicated as the upper and lower limits.

[0022] The inventors of this application have found that the elastic modulus of the support material is one factor that hinders further reduction of the internal resistance of the solid electrolyte layer, as well as the interfacial resistance between the positive and negative electrodes and the solid electrolyte sheet.

[0023] The positive and negative electrodes of an all-solid-state battery change volume due to factors such as charging and discharging, and the heat generated during these processes. When volume changes occur in the positive and negative electrodes, stress changes occur in the solid electrolyte layer in various directions. If the solid electrolyte layer lacks flexibility to withstand these stress changes, cracks will form at the interface between the positive and negative electrodes and the solid electrolyte sheet. This results in an increase in interfacial resistance between the positive and negative electrodes and the solid electrolyte sheet. In other words, the solid electrolyte layer needs to have the flexibility to follow the stress changes in the positive and negative electrodes.

[0024] The flexibility of a solid electrolyte sheet is influenced by the flexibility of the support structure, which is a component of the solid electrolyte sheet. In this disclosure, the modulus of elasticity is used as an indicator of the flexibility of the support structure. The modulus of elasticity is the dimensional change with respect to stress in the elastic region. The modulus of elasticity is expressed as the ratio of the stress applied to the displacement when a tensile test is performed in the elastic region.

[0025] Furthermore, this disclosure controls the flexibility of the solid electrolyte sheet in the elastic region, that is, the change in the region where it returns to its original shape after being compressed, thereby allowing the solid electrolyte sheet to follow the volume changes of the positive and negative electrodes. A low elastic modulus of the support indicates high flexibility of the solid electrolyte layer, while a high elastic modulus of the support indicates low flexibility of the solid electrolyte layer.

[0026] The support in this disclosure has an elastic modulus controlled to a range of 0.3 to 10 GPa. Furthermore, from the viewpoint of the flexibility of the support and further reducing the interfacial resistance between the positive and negative electrodes and the solid electrolyte layer, it is more preferable that the elastic modulus of the support before and after heating be in the range of 0.4 to 9 GPa. A support having an elastic modulus in the above range has an appropriate flexibility in the resulting solid electrolyte layer, so when volume changes occur due to the positive and negative electrodes, the solid electrolyte layer follows the volume change well. As a result, in a solid electrolyte sheet using the support, the cutting of the pass line of internal carrier ions is suppressed. In addition, in a solid electrolyte sheet using the support, adhesion between the positive electrode and the solid electrolyte layer, and between the solid electrolyte layer and the negative electrode is maintained. Due to these effects, the internal resistance of the solid electrolyte layer and the interfacial resistance between the positive and negative electrodes and the solid electrolyte layer can be reduced. In other words, by using this support, the resistance of the all-solid-state battery can be reduced.

[0027] If the elastic modulus of the support is below the above range, the support has high flexibility against stress, resulting in high conformability of the solid electrolyte sheet to volume changes of the positive and negative electrodes. As a result, the pass lines for carrier ions formed inside the solid electrolyte layer are cut, and the resistance of the solid electrolyte layer increases.

[0028] On the other hand, if the elastic modulus of the support exceeds the above range, the support's flexibility against stress is low, and the solid electrolyte sheet cannot follow the volume changes of the positive and negative electrodes. As a result, delamination occurs at the interface between the positive and negative electrodes and the solid electrolyte layer, and the interfacial resistance between the positive and negative electrodes and the solid electrolyte layer increases.

[0029] Furthermore, the support in this disclosure preferably has an elastic modulus in the range of 0.3 to 10 GPa after heating, from the viewpoint of suppressing the severance of the carrier ion pass line inside the solid electrolyte layer. The elastic modulus after heating referred to here is the elastic modulus measured after heating the support at 200°C for 1 hour. These heating conditions are sufficient for drying the solvent used in the solid electrolyte slurry.

[0030] If the elastic modulus after heat treatment is within the above range, the solid electrolyte layer retains flexibility to the volume changes of the positive and negative electrodes even after heat treatment, which can help suppress the disruption of the carrier ion pass lines within the solid electrolyte layer.

[0031] The support material is not limited in terms of thickness, basis weight, density, porosity, and tensile strength, as long as its elastic modulus is within the above range. As long as the elastic modulus is within the above range, it is not limited to the configuration of the support material, and it is possible to prevent the disruption of the carrier ion pass line within the solid electrolyte layer and to suppress the increase in interfacial resistance between the positive and negative electrodes and the solid electrolyte layer. In other words, as long as the elastic modulus is within the above range, it is not limited to the configuration of the support material, and it is possible to lower the resistance of the all-solid-state battery.

[0032] Furthermore, the thickness of the support is preferably 5 to 50 μm. If the thickness is less than 5 μm, the thickness of the solid electrolyte sheet tends to be thin, and the proportion of the solid electrolyte layer without support fibers in the thickness direction increases, which may cause cracks to occur. On the other hand, if the thickness exceeds 50 μm, the solid electrolyte sheet becomes thick, and the resistance of the all-solid-state battery tends to increase.

[0033] In addition, considering the balance between permeability and retention of the support material to the solid electrolyte slurry, and the strength of the handleable solid electrolyte sheet, the basis weight of the support material should be 1.0 to 15.0 g / m². ２ It is preferable that it be within the range of [specify range].

[0034] The support consists of at least one selected from paper and nonwoven fabric. Preferably, the support consists of at least one of paper and nonwoven fabric. This is for the following reasons: Paper refers to a material manufactured by bonding plant fibers and other fibers together. Nonwoven fabric refers to a sheet-like material made by treating various fiber webs, such as natural, recycled, and synthetic fibers, mechanically, chemically, thermally, or a combination thereof, without using a loom, and joining the constituent fibers together with adhesive or the adhesive force of the fibers themselves. In other words, paper and nonwoven fabric have a structure in which fibers are arranged randomly, and have multiple voids of various sizes and through holes of various sizes inside. For this reason, the coated solid electrolyte slurry can spread not only in the thickness direction but also in the surface direction. That is, the coated solid electrolyte may remain on the surface of the support, remain inside the support, or pass from the surface side through the through holes to reach the back side.

[0035] Therefore, in a solid electrolyte layer made using a support made of at least one of paper and nonwoven fabric, the solid electrolyte is filled not only on the surface of the support but also inside the support layer, thus forming a good carrier ion pass line. As a result, the solid electrolyte layer can reduce internal resistance and the interfacial resistance between the solid electrolyte layer and the positive and negative electrodes. Consequently, the solid electrolyte layer can reduce the resistance of the all-solid-state battery.

[0036] The materials that can be used as the support are not particularly limited, as long as they have high affinity with the solid electrolyte slurry, do not repel the solid electrolyte slurry, and do not adversely affect the solid electrolyte physically or chemically. Examples include organic fibers such as polyester fibers, cellulose fibers, polyamide fibers, polypropylene fibers, and acrylic fibers, and inorganic fibers such as glass fibers and alumina fibers. Furthermore, one or more fibers selected from these fibers can be used. By using these fibers, a support with excellent solid electrolyte filling properties can be obtained. Among these, polyester fibers, cellulose fibers, and polyamide fibers are more preferred from the viewpoint of the elastic modulus and heat resistance of the support.

[0037] The cellulose fibers referred to here include wood cellulose fibers, non-wood cellulose fibers, and regenerated cellulose. Polyamide fibers include aliphatic polyamides (nylon fibers), semi-aromatic polyamide fibers, and fully aromatic polyamide fibers (aramid fibers).

[0038] Furthermore, as a material used for the support, in addition to the main fibers that form the framework of the sheet, it is desirable that the support also contains adhesive fibers from the viewpoint of maintaining the shape of the support and its mechanical strength. Examples of adhesive fibers include fibers having fibrils on their surface (hereinafter referred to as fibrillated fibers) and synthetic resin binder fibers.

[0039] For example, fibrillated fibers that possess physical bonds through fiber entanglement include fibrillated cellulose fibers, fibrillated polyamide fibers, and fibrillated acrylic fibers. Furthermore, if hydroxyl groups are present, fibrillated fibers also possess chemical bonds through hydrogen bonding, similar to cellulose fibers. All types of fiber bonding are preferable because they contribute to maintaining the shape of the support and developing mechanical strength. Fibrillated cellulose fibers and fibrillated polyamide fibers, for example, are fibers that can form the framework of a sheet and possess adhesive properties, thus fulfilling the roles of both main fiber and binder fiber.

[0040] Synthetic resin binder fibers can be categorized into those that retain their fiber shape when a support is formed and those that do not retain their fiber shape and instead form a film, for example. Synthetic resin binder fibers that retain their fiber shape when a support is formed are preferred because they are heat-bonded only at the fiber contact points and do not easily hinder the penetration and permeation of solid electrolyte slurry into the support. Synthetic resin binder fibers that retain their fiber shape are not particularly limited as long as they have high affinity with solid electrolyte slurry, do not repel the solid electrolyte slurry, and do not adversely affect the solid electrolyte physically or chemically. Examples of synthetic resin binder fibers that retain their fiber shape include polyamide binder fibers, polyester binder fibers, polyester-polyester core-sheath type binder fibers, polyethylene binder fibers, and polypropylene-polyethylene core-sheath type binder fibers. Furthermore, one or more fibers selected from the above fibers can be used as synthetic resin binder fibers that retain their fiber shape.

[0041] On the other hand, synthetic resin binder fibers that cannot maintain their fiber shape when a support is formed melt due to moist heat during the support manufacturing process, forming a film that fills the gaps between the fibers. As a result, this inhibits the penetration and permeation of the solid electrolyte slurry into the support, making their use undesirable. For this reason, it is preferable that the support does not contain synthetic resin binder fibers that do not maintain their fiber shape when the support is formed. However, synthetic resin binder fibers may be included if they can maintain their fiber shape even after the support is formed. Here, "maintaining the fiber shape" means that when the fiber is observed from above, there is no change in the length of the fiber.

[0042] In a support material, a method for achieving an elastic modulus in the range of 0.3 to 10 GPa is to include, for example, 60% by mass or more of one or more fibers selected from polyester fibers, cellulose fibers, and polyamide fibers, with a basis weight of 1 to 15 g / m². ２ Methods such as [specific method] can be used. However, this does not apply if the modulus of elasticity can be kept within the above range.

[0043] There are no particular limitations on the method of manufacturing the support, and it can be manufactured by dry or wet methods, but the wet method is preferred. As for the wet method, a papermaking method in which fibers dispersed in water are deposited on a wire, dewatered, dried, and then formed into paper is preferred from the viewpoint of homogeneity of the support's form. There are no particular limitations on the papermaking method of the support as long as the elastic modulus is satisfied, and papermaking methods such as long-wire papermaking, short-wire papermaking, and cylinder-wire papermaking can be used. The support may also be made by combining multiple layers formed by these papermaking methods. Furthermore, additives such as dispersants, defoamers, and paper strength enhancers may be added during papermaking, and post-processing such as paper strength enhancement, hydrophilic processing, calendering, thermal calendering, and embossing may be performed after the paper layer is formed.

[0044] <2. Embodiment of a Secondary Battery (Second Embodiment)> Next, an embodiment of a secondary battery using the support described above will be described. The secondary battery is, for example, an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer. In this case, the solid electrolyte layer is arranged to be interposed between the positive electrode and the negative electrode. The solid electrolyte layer is configured as a solid electrolyte sheet in which a solid electrolyte is held by a support. The solid electrolyte sheet comprises a support for a secondary battery and a solid electrolyte, with the solid electrolyte held by the support and the solid electrolyte and support integrated into one structure.

[0045] The types of positive and negative electrodes used in all-solid-state batteries are not particularly limited. For example, an all-solid-state battery may be composed of known positive and negative electrodes, but is not limited to these. Furthermore, the type of all-solid-state battery is not particularly limited, and can be any type depending on the selection of materials used to make up the battery, such as a lithium-ion secondary battery or a sodium-ion secondary battery. The above-mentioned all-solid-state battery can be used, for example, as a storage battery for mobile communication devices, portable electronic devices, electric bicycles, electric motorcycles, electric vehicles, and small household power storage devices.

[0046] [Positive electrode, negative electrode] In a secondary battery, the positive electrode active material used in the positive electrode layer and the negative electrode active material used in the negative electrode layer are not particularly limited, and any material that functions as the positive electrode and negative electrode of an all-solid-state battery according to various carrier ions is acceptable.

[0047] The positive electrode is formed having a positive electrode active material-containing layer and a positive electrode current collector. For example, if the all-solid-state battery is a lithium-ion secondary battery, the positive electrode needs to be composed of a material capable of occluding and releasing lithium ions.

[0048] As the positive electrode current collector, for example, aluminum or the like is used. As the positive electrode active material, for example, in the sulfide system, titanium sulfide (TiS ２ ), molybdenum sulfide (MoS ２ ), iron sulfide (FeS, FeS ２ ), copper sulfide (CuS), and nickel sulfide (Ni ３ S ２ ) and the like can be mentioned. Also, in the oxide system, bismuth oxide (Bi ２ O ３ ), bismuth lead oxide (Bi ２ Pb ２ O ５ ), copper oxide (CuO), vanadium oxide (V ６ O １３ ), lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium manganate (LiMnO ２ ), Li(NiCoMn)O ２ , Li(NiCoAl)O ２ , and Li(NiCo)O ２ and the like can be mentioned. It is also possible to use a mixture thereof.

[0049] The negative electrode is formed having a negative electrode current collector and a negative electrode active material-containing layer. For example, if the all-solid-state battery is a lithium-ion secondary battery, as the negative electrode active material, metallic lithium, metallic indium, or a material capable of occluding and releasing lithium ions can be used.

[0050] For example, copper can be used as the negative electrode current collector. Examples of negative electrode active materials include carbon materials, specifically artificial graphite, graphite carbon fibers, resin-fired carbon, pyrolysis vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fibers, vapor-grown carbon fibers, natural graphite, and non-graphitizable carbon. Alternatively, mixtures thereof may also be used. Furthermore, examples include metallic lithium, metallic indium, metallic aluminum, and metallic silicon themselves, as well as alloys combining these metals with other elements or compounds.

[0051] The positive and negative electrodes of an all-solid-state battery are constructed by selecting two materials that can form electrodes, comparing the charge and discharge potentials of the two compounds, and using the one exhibiting a noble potential as the positive electrode and the one exhibiting a low potential as the negative electrode.

[0052] [Solid Electrolyte Layer] In an all-solid-state battery, the solid electrolyte layer is configured as a solid electrolyte sheet in which a solid electrolyte is held on a support. The type of solid electrolyte constituting the solid electrolyte sheet is not particularly limited, and for example, known materials that can be used as solid electrolytes in all-solid-state batteries can be used. Furthermore, the solid electrolyte is not particularly limited, and only needs to allow carrier ion conduction between the positive electrode and the negative electrode. Examples include oxide-based solid electrolytes and sulfide-based solid electrolytes. In addition, binders and other components may be added as needed.

[0053] For example, sulfide-based solid electrolytes capable of conducting lithium ions include sulfide-based amorphous solid electrolytes and sulfide-based crystalline solid electrolytes. A specific example of a sulfide-based amorphous solid electrolyte is Li ２ S-SiS ２ Li ２ S-GeS ２ Li ２ S-P ２ S ５ Li ２ S-B ２ S ３ Li ２ S-SiS ２ -Li ３ PO４ Li ２ S-S, iS ２ -Li ２ SO ４ Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S ５ -P ２ O ５ -, LiI, Li ２ S-B ２ S ３ -LiI, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ , and S-SiS ２ -B ２ S ３ - Examples include LiI. Note that sulfide-based amorphous solid electrolytes may contain other elements. Also, a specific example of a sulfide-based crystalline solid electrolyte is Li ３．２５ Ge ０．２５ P ０．７５ S ４ , and Li １０ GeP ２ S １２ Li ６ PS ５ Examples include chlorine, but sulfide-based crystalline solid electrolytes are not limited to these elemental compositions.

[0054] The solid electrolyte may be anything other than a sulfide-based solid electrolyte or an oxide-based solid electrolyte. Other examples include semi-solid polymer electrolytes such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, or polyacrylonitrile containing carrier ions. The solid electrolyte may also be a so-called gel-type electrolyte in which the electrolyte is held in a polymer solid electrolyte, such as a polymer containing at least one selected from polyethylene oxide polymers, polyorganosiloxane chains, and polyoxyalkylene chains.

[0055] [Method for Manufacturing Solid Electrolyte Sheets] The method for manufacturing solid electrolyte sheets is not particularly limited, and conventional methods in the art can be applied. For example, one method involves preparing a slurry by dispersing a solid electrolyte in a solvent, and then applying the prepared slurry to a support and drying it. The solvent used to prepare the solid electrolyte slurry is not particularly limited, as long as it does not adversely affect the performance of the solid electrolyte. For example, non-aqueous solvents can be used.

[0056] The coating method for applying a slurry containing a solid electrolyte to one or both sides of a support is not particularly limited and includes, for example, slide die coating, comma die coating, comma reverse coating, gravure coating, and gravure reverse coating. Drying after coating the slurry containing the solid electrolyte is performed, for example, by a drying apparatus using hot air, a heater, high frequency, etc.

[0057] The solid electrolyte sheet can be used as a dry sheet, but it may also be further compressed to increase its mechanical strength and density. Methods of compression include, for example, sheet pressing or roll pressing.

[0058] Alternatively, a layer consisting solely of the solid electrolyte may be formed on one or both sides of the support containing the solid electrolyte. However, in this configuration, a thick solid electrolyte layer is formed where there is no support, and if it is made too thick, cracks are likely to occur.

[0059] [Method for Manufacturing All-Solid-State Batteries] All-solid-state batteries can be manufactured by placing a solid electrolyte layer containing a solid electrolyte sheet between the positive electrode layer and the negative electrode layer described above, and bonding them together. The bonding method is not particularly limited, but examples include a method of laminating the solid electrolyte sheet, the positive electrode, and the negative electrode and pressing them together, or a method of applying pressure through two rolls (roll-to-roll). In addition, to improve the adhesion between the solid electrolyte layer and the positive electrode layer or the negative electrode layer, an ion-conductive active material or an adhesive material that does not inhibit ion conductivity may be placed at the bonding interface.

[0060] The following describes specific examples of the supports according to embodiments of the present invention. First, supports for Examples 1 to 5 and Comparative Examples 1 to 10 were prepared by the following method. Except for Comparative Example 2, the supports were prepared as paper or wet-laid nonwoven fabric using a papermaking method.

[0061] [Example 1] Using a raw material mixture consisting of 30% by mass of nylon-based fibers with an average fiber diameter of 5 μm and an average fiber length of 3 mm, 30% by mass of polyester binder fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, and 40% by mass of fibrillated acrylic fibers with a CSF value of 20 ml and an average fiber length of 0.8 mm, paper was made using a short-mesh papermaking process, resulting in a thickness of 5 μm and a basis weight of 1.0 g / m². ２ , density 0.20g / cm ３ A support was obtained. The blending ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 60% by mass.

[0062] [Example 2] Using a raw material made by mixing 25% by mass of polyester-based fibers with an average fiber diameter of 3 μm and an average fiber length of 3 mm, and 75% by mass of polyester-polyester core-sheath type binder fibers with an average fiber diameter of 5 μm and an average fiber length of 5 mm, paper was made using a circular mesh to produce a paper with a thickness of 12 μm and a basis weight of 3.2 g / m². ２ , density 0.27g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0063] [Example 3] Using a raw material mixture consisting of 50% by mass of fibrillated aramid fibers with a CSF value of 10 ml and an average fiber length of 0.5 mm, 30% by mass of semi-aromatic polyamide-based fibers with an average fiber diameter of 8 μm and an average fiber length of 5 mm, and 20% by mass of polypropylene-polyethylene core-sheath fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, paper was made using a long screen, resulting in a thickness of 20 μm and a basis weight of 9.8 g / m². ２ , density 0.50g / cm ３ A support was obtained. The blending ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 80% by mass.

[0064] [Example 4] Using fibrillated cellulose fibers with a CSF value of 200 ml and an average fiber length of 1.6 mm, paper was made using a short mesh method, resulting in a thickness of 50 μm and a basis weight of 14.8 g / m². ２ , density 0.30g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0065] [Example 5] Using a raw material mixture consisting of 40% by mass of polyester-based fibers with an average fiber diameter of 12 μm and an average fiber length of 5 mm, 20% by mass of polyester binder fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, and 40% by mass of polypropylene-polyethylene core-sheath fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, paper was made using a circular mesh to produce a paper with a thickness of 45 μm and a basis weight of 7.0 g / m². ２ , density 0.16g / cm ３ A support was obtained. The blending ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 60% by mass.

[0066] [Comparative Example 1] Using polypropylene-polyethylene core-sheath fibers with an average fiber diameter of 10 μm and an average fiber length of 5 mm, paper was made using a short mesh method, referring to the method for manufacturing a support described in Example 1 of Patent Document 1, resulting in a thickness of 30 μm and a basis weight of 5.0 g / m². ２ , density 0.17g / cm ３ A support was obtained. The blending ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 0% by mass.

[0067] [Comparative Example 2] A support was prepared using the same method as described in Example 13 of Patent Document 2, with a thickness of 18 μm and a basis weight of 5.0 g / m². ２ , density 0.28g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0068] [Comparative Example 3] Using a raw material mixture consisting of 35% by mass of nylon-based fibers with an average fiber diameter of 5 μm and an average fiber length of 3 mm, 35% by mass of polyester binder fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, and 30% by mass of fibrillated acrylic fibers with a CSF value of 20 ml and an average fiber length of 0.8 mm, paper was made using a short-mesh papermaking process, resulting in a thickness of 5 μm and a basis weight of 0.8 g / m². ２ , density 0.17g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 70% by mass.

[0069] [Comparative Example 4] Using fibrillated aramid fibers with a CSF value of 200 ml and an average fiber length of 1.3 mm, paper was made using a short mesh method, resulting in a thickness of 40 μm and a basis weight of 14.9 g / m². ２ , density 0.37g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0070] [Comparative Example 5] Using a raw material mixture consisting of 35% by mass of polyester-based fibers with an average fiber diameter of 12 μm and an average fiber length of 5 mm, 15% by mass of polyester binder fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, and 50% by mass of polypropylene-polyethylene core-sheath fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, paper was made using a circular mesh, resulting in a thickness of 45 μm and a basis weight of 6.5 g / m². ２ , density 0.14g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 50% by mass.

[0071] [Comparative Example 6] Using a raw material mixture consisting of 45% by mass of polyester-based fibers with an average fiber diameter of 4 μm and an average fiber length of 3 mm, 45% by mass of polyester binder fibers with an average fiber diameter of 5 μm and an average fiber length of 3 mm, and 10% by mass of polyvinyl alcohol fibers with an average fiber diameter of 15 μm and an average fiber length of 3 mm, paper was made using a circular mesh to produce a paper with a thickness of 20 μm and a basis weight of 9.0 g / m². ２ , density 0.45g / cm ３ A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 90% by mass.

[0072] [Comparative Example 7] Using a raw material obtained by mixing 50% by mass of fibrillated cellulose fibers with a CSF value of 10 ml and an average fiber length of 0.5 mm and 50% by mass of fibrillated aramid fibers with a CSF value of 50 ml and an average fiber length of 0.9 mm, papermaking was carried out on a Fourdrinier wire, and a support with a thickness of 3 μm and a basis weight of 1.5 g / m ２ and a density of 0.50 g / cm ３ was obtained. The blending ratio of polyester fibers, cellulose fibers and polyamide fibers in the obtained support is 100% by mass.

[0073] [Comparative Example 8] Using a raw material obtained by mixing 50% by mass of fibrillated aramid fibers with a CSF value of 15 ml and an average fiber length of 0.7 mm and 50% by mass of polyester binder fibers with an average fiber diameter of 5 μm and an average fiber length of 3 mm, papermaking was carried out on a cylinder mold wire, and a support with a thickness of 55 μm and a basis weight of 13.9 g / m ２ and a density of 0.25 g / cm ３ was obtained. The blending ratio of polyester fibers, cellulose fibers and polyamide fibers in the obtained support is 100% by mass.

[0074] [Comparative Example 9] Using fibrillated cellulose fibers with a CSF value of 20 ml and an average fiber length of 0.7 mm, papermaking was carried out on a cylinder mold wire, and a support with a thickness of 5 μm and a basis weight of 0.8 g / m ２ and a density of 0.16 g / cm ３ was obtained. The blending ratio of polyester fibers, cellulose fibers and polyamide fibers in the obtained support is 100% by mass.

[0075] [Comparative Example 10] Using a raw material obtained by mixing 40% by mass of fibrillated aramid fibers with a CSF value of 60 ml and an average fiber length of 0.9 mm, 40% by mass of polyester binder fibers with an average fiber diameter of 5 μm and an average fiber length of 3 mm, and 20% by mass of fibrillated acrylic fibers with a CSF value of 110 ml and an average fiber length of 1.1 ml, papermaking was carried out on a cylinder mold wire, and a support with a thickness of 40 μm and a basis weight of 15.5 g / m ２ and a density of 0.39 g / cm ３ was obtained. The blending ratio of polyester fibers, cellulose fibers and polyamide fibers in the obtained support is 80% by mass.

[0076] [Fabrication of All-Solid-State Batteries] Next, all-solid-state batteries were fabricated using the supports of the above examples and comparative examples. The specific fabrication method is as follows: (Positive Electrode Structure) LiNiCoAlO as the positive electrode active material ２ A ternary powder is used as a sulfide-based solid electrolyte, with Li ２ S-P ２ S ５ Amorphous powder was mixed with carbon fiber as a conductive additive. A dehydrated xylene solution containing dissolved SBR (styrene-butadiene rubber) was added to this mixed powder to prepare a positive electrode coating solution. The positive electrode coating solution was applied to an aluminum foil current collector, which served as the positive electrode current collector, dried, and then rolled to obtain a positive electrode structure.

[0077] (Negative electrode structure) Graphite is used as the negative electrode active material, and Li is used as the sulfide-based solid electrolyte. ２ S-P ２ S ５ A negative electrode coating solution was prepared by mixing amorphous powder with PVdF (polyvinylidene fluoride) as a binder and NMP (N-methyl-2-pyrrolidone) as a solvent. The negative electrode structure was obtained by coating a copper foil current collector, which is the negative electrode current collector, with the negative electrode coating solution, drying it, and then rolling it.

[0078] (Solid electrolyte sheet) Li as a sulfide-based solid electrolyte ２ S-P ２ S ５ Amorphous powder was mixed with SBR as a binder and xylene as a solvent to prepare a solid electrolyte slurry. The solid electrolyte slurry was coated onto the supports of each of the above examples and comparative examples, and dried to obtain solid electrolyte sheets.

[0079] [Manufacturing of All-Solid-State Batteries] A negative electrode structure measuring 88 mm x 58 mm, a solid electrolyte sheet measuring 92 mm x 62 mm, and a positive electrode structure measuring 87 mm x 57 mm were laminated, dry-laminated, and bonded together to obtain a single cell of an all-solid-state battery. The obtained single cell was placed in an aluminum laminate film with terminals attached, degassed, heat-sealed, and packaged.

[0080] [Measurement Method for the Characteristics of the Support and All-Solid-State Battery] The characteristics of the fabricated support and all-solid-state battery were measured under the following conditions and methods. [CSF Value] The CSF value was measured according to "JIS P8121-2 'Pulps - Determination of drainability - Part 2: Canadian Standard Freeness Method'" (ISO 5267-2 'Pulps - Determination of drainability - Part 2: "Canadian Standard" freeness method').

[0081] [Fiber Length] (Average fiber length) The fiber length was measured using the apparatus described in "JIS P 8226-2 'Pulp - Determination of fiber length by automated optical analysis - Part 2: Unpolarized light method'" (ISO 16065-2 'Pulps - Determination of fiber length by automated optical analysis - Part 2: Unpolarized light method'), in this case using a Fiber Tester PLUS (manufactured by Lorentzen & Wettre), and the length-loaded average fiber length was used as the fiber length.

[0082] (Fiber length of polyester fibers) Because polyester fibers are optically transparent, they cannot be accurately identified in images. Therefore, accurate measurement of fiber length was not possible using the above-mentioned automated optical analysis method. Accordingly, the fiber length of polyester fibers was measured by the following method. First, a slide was prepared with fibers randomly dispersed. Then, the fiber length of the fibers on the slide was measured directly using a scale.

[0083] [Thickness] The thickness of the support was measured using a micrometer described in "5.1.1 Measuring instrument and measurement method a. When using an outside micrometer," as specified in "JIS C 2300-2 'Cellulose paper for electrical use - Part 2: Test methods' 5.1 Thickness," with the measuring force set to 1.5 N and the diameter of the pressure surface changed to 14.3 mmφ, and by folding the paper into 10 sheets as described in "5.1.3 When measuring thickness by folding paper."

[0084] [Basis Weight] The basis weight of the support material in an oven-dry state was measured using the method specified in "JIS C 2300-2 'Cellulose paper for electrical use - Part 2: Test methods' 6 Basis weight".

[0085] [Density] The density of the support was calculated using the following formula: Density (g / cm³) ３ )=W / T W: Basis weight (g / m ２ ), T: thickness (μm)

[0086] [Porrosion] The porosity of the support was calculated using the following formula. If the support is composed of multiple materials, the average specific gravity of the constituent fibers was determined by calculating a ratio proportional to the material composition before calculating the porosity. Porrosion (%) = (1 - (D / S)) × 100 D: Support density (g / cm³) ３ ), S: Specific gravity of constituent fibers (g / cm³) ３ )

[0087] [Tensile Strength] The tensile strength of the support was determined by measuring the maximum tensile load in the longitudinal direction (manufacturing direction) of the support with a test width of 50 mm, according to the method specified in "JIS P 8113 'Paper and board - Determination of tensile properties - Part 2: Constant rate of tensile strength'" (ISO 1924-2 'Paper and board - Determination of tensile properties - Part 2: Constant rate of tensile strength').

[0088] [Module of Elasticity] The test was conducted with a test width of 50 mm according to the method specified in "JIS P 8113 'Paper and board - Determination of tensile properties - Part 2: Constant rate of elasticity method'" (ISO 1924-2 'Paper and board - Determination of tensile properties - Part 2: Constant rate of elasticity method'), and the modulus of elasticity was determined by the method described in "10.8 Tensile modulus of elasticity".

[0089] [Evaluation of Self-Standing Ability] The self-standing ability of each fabricated solid electrolyte sheet was evaluated. When a fabricated solid electrolyte sheet measuring 92 mm x 62 mm was lifted while holding the short edge, a score of ○ was given if no cracks or fissures were visible to the naked eye, and a score of × was given if cracks or fissures were visible to the naked eye when lifted.

[0090] [Internal Resistance of Solid Electrolyte Sheet] For the all-solid-state battery, the battery was charged to 4.0V at a current density of 0.1C in an environment of 25°C, and the impedance in the frequency range of 0.1Hz to 1MHz was measured using an LCR meter. The arc portion of the obtained Cole-Cole plot was fitted into a semicircle with the x-axis as the base, and the value at the point where the right end of the semicircle intersects with the x-axis was taken as the resistance value.

[0091] [Discharge Capacity of Solid Electrolyte Sheets] For all-solid-state batteries, the batteries were charged to 4.0V at a current density of 0.1C in an environment of 25°C, and then discharged to 2.5V at a current density of 0.1C. The discharge capacity at that time was measured.

[0092] Table 1 shows the names and blending ratios of the fibers used in each support structure described above in Examples 1 to 5 and Comparative Examples 1 to 10. Table 2 shows the characteristics of each support structure in each of the above-mentioned examples and conventional examples, as well as the evaluation results of the battery characteristics of the all-solid-state batteries.

[0093]

[0094]

[0095] The evaluation results of all-solid-state batteries using the supports of each example and comparative example are described in detail below. The solid electrolyte sheets using the supports of each example were able to form self-supporting solid electrolyte sheets. Furthermore, the all-solid-state batteries using the supports of each example had lower resistance and higher discharge capacity compared to the all-solid-state batteries using the supports of Comparative Examples 2, 4, 5, 6, 8, and 10.

[0096] The solid electrolyte sheet using the support of Comparative Example 1 lacked self-supporting properties. Furthermore, the support of Comparative Example 1 had a lower elastic modulus compared to the supports of each example. Because the support of Comparative Example 1 was composed of a polypropylene-polyethylene core sheath, it melted when the solid electrolyte slurry was dried, and was unable to maintain its shape. As a result, it is believed that a self-supporting solid electrolyte sheet could not be obtained. Moreover, even if the drying temperature was lowered to suppress melting, the elastic modulus was low at 0.2 GPa, resulting in excessive flexibility of the support against stress. Therefore, it is believed that the support of Comparative Example 1 had its carrier ion pass lines, formed inside the solid electrolyte layer, severed by the stress applied due to the volume changes of the positive and negative electrodes.

[0097] The all-solid-state batteries using the supports of Comparative Example 2 and Comparative Example 5 have higher resistance and lower discharge capacity compared to the all-solid-state batteries using the supports of each embodiment. Furthermore, the supports of Comparative Example 2 and Comparative Example 5 have lower elastic moduli compared to the supports of each embodiment. Because the elastic moduli of the supports of Comparative Example 2 and Comparative Example 5 are low at 0.2 GPa, the supports are too flexible to stress. For this reason, it is thought that the carrier ion pass lines formed inside the solid electrolyte layer were severed by the stress applied due to the volume changes of the positive and negative electrodes in the supports of Comparative Example 2 and Comparative Example 5.

[0098] The support in Comparative Example 1 is composed solely of polypropylene-polyethylene core-sheath fibers. Furthermore, the support in Comparative Example 5 contains a lower amount of polyester fibers (50% by mass) compared to the other examples. On the other hand, each example contains 60% by mass or more of polyester fibers, polyamide fibers, and cellulose fibers, resulting in an elastic modulus of 0.3 GPa or higher.

[0099] Unlike the supports of each example, which were obtained by the papermaking method, the support of Comparative Example 2 was obtained by the dry method. The elastic modulus of fibers increases with increasing stretch ratio. The fibers constituting the support of Comparative Example 2 were manufactured by the spunbond method and the meltblown method, and the stretch ratio applied to the fibers is smaller compared to the fibers used in the papermaking method. As a result, it is thought that the elastic modulus of the obtained support was lower compared to each example. In addition, in the case of the spunbond method and the meltblown method, the support is formed with long fibers exceeding 10 mm, resulting in poor support formation. Therefore, it is thought that unevenness in the filling of the solid electrolyte occurred, leading to a higher ionic resistance of the formed solid electrolyte layer.

[0100] In other words, from a comparison of each example with Comparative Example 1 and Comparative Example 5, it can be seen that the fibers used in the support preferably contain 60% by mass or more of polyester fibers, polyamide fibers, and cellulose fibers. Furthermore, from a comparison of each example with Comparative Example 2, it can be seen that the support is preferably composed of fibers 10 mm or less in length. In addition, from a comparison of each example with Comparative Example 2 and Comparative Example 5, it can be seen that the elastic modulus of the support preferably is 0.3 GPa or higher.

[0101] The solid electrolyte sheets using the supports of Comparative Examples 3, 7, and 9 lacked self-supporting properties. The supports of Comparative Examples 3 and 9 had a basis weight of 0.8 g / m² compared to the respective examples. ２ Because the basis weight was low, the tensile strength of the support was weak. Also, since the support of Comparative Example 7 was thinner at 3 μm compared to each example, a large portion of the solid electrolyte was made up of solid electrolyte in the thickness direction of the solid electrolyte sheet. As a result, it is thought that the effect of using the support could not be fully obtained, and a self-supporting solid electrolyte sheet could not be obtained. Furthermore, even if a self-supporting solid electrolyte sheet could be obtained with the supports of Comparative Examples 3, 7, and 9, and the characteristics of the all-solid-state battery could be evaluated, it is thought that the resistance was higher and the discharge capacity was lower compared to each example. In other words, from a comparison between each example and Comparative Examples 3 and 9, the basis weight of the support should be 1.0 g / m². ２ From the above comparison between each example and Comparative Example 7, it can be seen that a support thickness of 5 μm or more is preferable.

[0102] The all-solid-state battery using the support of Comparative Example 4 has higher resistance and lower discharge capacity compared to the all-solid-state batteries using the supports of each embodiment. Furthermore, the support of Comparative Example 4 has a higher elastic modulus compared to the supports of each embodiment. The elastic modulus of the support of Comparative Example 4 is high at 11.3 GPa. Therefore, it is thought that the support has poor flexibility against stress, and the solid electrolyte sheet could not follow the volume changes of the positive and negative electrodes. As a result, delamination occurred at the interface between the positive and negative electrodes and the solid electrolyte layer, and the interfacial resistance increased. In other words, from the comparison between each embodiment and Comparative Example 4, it can be seen that an elastic modulus of 10 GPa or less is preferable for the support.

[0103] The all-solid-state battery using the support of Comparative Example 6 has higher resistance and lower discharge capacity compared to the all-solid-state batteries using the support of each example. The support of Comparative Example 6 contains 10% by mass of polyvinyl alcohol fibers. The polyvinyl alcohol fibers contained in the support of Comparative Example 6 melted due to moist heat and were unable to maintain their fiber shape, becoming film-like. This is thought to have inhibited the penetration of the solid electrolyte slurry into the support. In other words, a comparison between each example and Comparative Example 6 shows that the inclusion of synthetic resin binder fibers that cannot maintain their fiber shape is undesirable.

[0104] The all-solid-state battery using the support of Comparative Example 8 has higher resistance and lower discharge capacity compared to the all-solid-state batteries using the supports of each example. The support of Comparative Example 8 is thicker than that of each example. Since the support of Comparative Example 8 is thick at 55 μm, it is thought that the resulting solid electrolyte sheet is thicker, resulting in higher resistance and lower discharge capacity. In other words, from the comparison between each example and Comparative Example 8, it can be seen that a thickness of 50 μm or less is preferable.

[0105] The all-solid-state battery using the support of Comparative Example 10 has higher resistance and lower discharge capacity compared to the all-solid-state batteries using the supports of each example. Furthermore, the support of Comparative Example 10 has a higher basis weight compared to the supports of each example. The basis weight of the support of Comparative Example 10 is 15.5 g / m². ２Because of this high density, the amount of fiber constituting the support is large. For this reason, it is possible that the solid electrolyte sheet using the support of Comparative Example 10 had impaired permeability of the solid electrolyte slurry, resulting in insufficient formation of carrier ion pass lines in the thickness direction. In other words, from a comparison between each example and Comparative Example 10, the basis weight of the support is 15.0 g / m². ２ The following are preferable.

[0106] The all-solid-state battery using the support of Example 1 has higher resistance and lower discharge capacity compared to the all-solid-state batteries using the supports of Examples 2 and 5. Furthermore, the elastic modulus of the support of Example 1 is lower than that of Examples 2 and 5, at 0.3 GPa, compared to 0.5 GPa for Examples 2 and 5. Also, the all-solid-state battery using the support of Example 4 has higher resistance and lower discharge capacity compared to the all-solid-state battery using the support of Example 3. Furthermore, the elastic modulus of the support of Example 4 is higher than that of Example 3, at 9.8 GPa, compared to 8.8 GPa for Example 3. In other words, from the comparison between Examples 1 and 4 and Examples 2, 3, and 5, it can be seen that an elastic modulus of 0.4 to 9 GPa for the support is more preferable.

[0107] The above-described embodiment is merely an example, and for example, the composition of the carrier ions, solid electrolyte, positive electrode, and negative electrode can be appropriately modified by those skilled in the art. As explained above, by using a support having an elastic modulus of 0.3 to 10 GPa, which includes at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, and is made up of at least one selected from paper and nonwoven fabric, the flexibility of the resulting solid electrolyte layer can be appropriately adjusted, and the solid electrolyte layer can follow the volume changes caused by the positive and negative electrodes well. As a result, the cutting of the carrier ion pass lines inside the resulting solid electrolyte sheet can be suppressed, and the adhesion between the formed positive electrode and solid electrolyte layer, and between the solid electrolyte layer and the negative electrode can be maintained. As a result, the internal resistance of the solid electrolyte layer, as well as the interfacial resistance between the positive and negative electrodes and the solid electrolyte layer, can be reduced. In other words, by using this support, an all-solid-state battery with low resistance can be obtained.

[0108] It should be noted that the present invention is not limited to the configuration described in the above-described embodiments, and various modifications and changes are possible without departing from the configuration of the present invention.

Claims

1. A support for a secondary battery, comprising only fibers contained in the solid electrolyte layer of a secondary battery, comprising at least one selected from paper and nonwoven fabric, and including at least one selected from polyester fibers, cellulose fibers and polyamide fibers, and having an elastic modulus in the range of 0.3 to 10 GPa.

2. The support for a secondary battery according to claim 1, comprising 60% by mass or more of at least one selected from polyester fibers, cellulose fibers, and polyamide fibers.

3. Thickness of 5 to 50 μm, basis weight of 1.0 to 15.0 g / m² ２ A support for a secondary battery according to claim 1 or 2, which is within the range of the following:

4. A solid electrolyte sheet comprising a membrane-like support and a solid electrolyte held in the support, wherein the support is made of at least one selected from paper and nonwoven fabric, and includes at least one selected from polyester fibers, cellulose fibers and polyamide fibers, and has an elastic modulus in the range of 0.3 to 10 GPa.

5. A secondary battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte sheet disposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte sheet comprises a support made of at least one selected from paper and nonwoven fabric, and containing at least one selected from polyester fibers, cellulose fibers and polyamide fibers, having an elastic modulus in the range of 0.3 to 10 GPa, and a solid electrolyte held in the support.

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