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

Abstract

The present invention provides a support for a secondary battery that can reduce 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. [Solution] A support for a secondary battery is constructed comprising at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, with an elastic modulus of 0.3 to 10 GPa.

Description

[Technical Field]

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

[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 primarily use organic electrolytes as the liquid electrolyte. Because organic electrolytes are liquids, there are concerns about leakage and flammability. Therefore, development is underway on rechargeable batteries that use a highly safe solid electrolyte instead of an organic electrolyte (hereinafter referred to as "all-solid-state batteries"). Because the electrolyte in all-solid-state batteries is solid, there is no leakage, and compared to liquid electrolytes, they are more flame-retardant and heat-resistant, making them a highly safe rechargeable battery that is attracting attention. Due to their high level of safety, small all-solid-state batteries are being mass-produced for use in wearable devices and other applications 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 an all-solid-state battery, 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, an all-solid-state battery requires the formation of carrier ion path lines 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 ensuring a stable supply of resources.

[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, all-solid-state batteries have been proposed that use a solid electrolyte sheet, which is an integrated solid electrolyte sheet containing a solid electrolyte in a membrane-like sheet (hereinafter referred to as a support). Various nonwoven fabric substrates have been proposed as supports for all-solid-state batteries. For example, a fiber aggregate containing polyolefin resin fibers, 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 / 50mm) 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 with an elastic recovery rate of 30-99% 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. As disclosed in Patent Document 2, 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 related to a support included in a solid electrolyte layer, wherein the longitudinal and lateral stiffness flexibility after heat treatment are each in the range of 5 to 250 mN, for a lithium ion secondary battery is disclosed (for example, see Patent Document 3). By using this support, it can withstand the non-uniform stress applied to the solid electrolyte layer, and the deformation of the support is suppressed. As a result, the lithium ion path line inside the pre-formed solid electrolyte layer is maintained, and Patent Document 3 discloses that an increase in internal resistance can be suppressed by the pressure integration of the positive electrode, the solid electrolyte layer, and the negative electrode.

[0010] As another related technology, a technology is disclosed that can exhibit flexible responsiveness to various forces in various directions applied to a separator for an aluminum electrolytic capacitor by optimizing the stretchability of the separator (for example, Patent Document 4). In this technology, a separator for an aluminum electrolytic capacitor with a tensile elastic modulus of 500 to 2000 MPa is disclosed. The tensile elastic modulus indicates the ease of deformation in the elastic deformation region. The lower the tensile elastic modulus, the easier it is to stretch and deform with a weak force. Also, the higher the tensile elastic modulus, the stronger the force required to reach deformation.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[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 applied 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, including a large amount of binder fibers that do not maintain their fiber shape increases the density. As a result, the penetration of the solid electrolyte slurry into the nonwoven fabric substrate becomes insufficient, and it was sometimes difficult to uniformly fill the inside of the support with the solid electrolyte.

[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. [Means for solving the problem]

[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 in 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 comprises a support having an elastic modulus of 0.3 to 10 GPa, which is made of at least one selected from paper and nonwoven fabric and includes at least one selected from polyester fiber, cellulose fiber, and polyamide fiber, and a solid electrolyte held in the support. [Effects of the Invention]

[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, as well as 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. [Modes for carrying out the invention]

[0020] The following describes examples of embodiments for carrying out the present invention, but the present invention is not limited to these examples. The explanation will be given 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)> The following describes specific embodiments of the support for secondary batteries. The secondary battery support of this embodiment (hereinafter also simply referred to as "support") is a support for holding the solid electrolyte of a secondary battery, and is made of at least one selected from paper and nonwoven fabric, and includes at least one selected from polyester fiber, cellulose fiber, and polyamide fiber, 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 undergo volume changes 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 material that makes up the solid electrolyte sheet. In this disclosure, the modulus of elasticity is used as an indicator of the flexibility of the support. The modulus of elasticity is the dimensional change in response 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, so that the solid electrolyte sheet can 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, and 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 improving 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 the elastic modulus within the above range results in a solid electrolyte layer with appropriate flexibility, allowing the solid electrolyte layer to readily follow volume changes caused by the positive and negative electrodes. As a result, the disruption of internal carrier ion pass lines is suppressed in a solid electrolyte sheet using this support. Furthermore, adhesion between the positive electrode and the solid electrolyte layer, and between the solid electrolyte layer and the negative electrode, is maintained in a solid electrolyte sheet using this support. Due to these effects, 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, the resistance of an all-solid-state battery can be lowered by using this support.

[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 a post-heating modulus in the range of 0.3 to 10 GPa, from the viewpoint of suppressing the severance of the carrier ion pass line inside the solid electrolyte layer. The post-heating modulus referred to here is the 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 thicker, which tends to increase the resistance of the all-solid-state battery.

[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, on the other hand, refers to a sheet-like material made without using a loom, by treating various fiber webs, such as natural, recycled, and synthetic fibers, mechanically, chemically, thermally, or a combination thereof, and joining the constituent fibers together with adhesives or the adhesive force of the fibers themselves. In other words, paper and nonwoven fabrics have a structure in which fibers are arranged randomly, and they have multiple voids and through-holes of various sizes within them. Therefore, 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 through the through-holes from the surface side 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 a 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, as well as 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 of the support and heat resistance.

[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 contain 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, as is the case with 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 are fibers that can form the framework of a sheet and also possess adhesive properties, and are fibers that serve as both main fibers and binder fibers.

[0040] Synthetic resin binder fibers include those that maintain their fiber shape while forming a support, and those that cannot maintain their fiber shape and instead form, for example, a film. Synthetic resin binder fibers that maintain their fibrous shape while forming a support are preferable 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. The synthetic resin binder fibers that maintain their fibrous shape are not particularly limited as long as they have high affinity to the 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 maintain their fibrous 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 the synthetic resin binder fibers that maintain their fibrous shape.

[0041] On the other hand, synthetic resin binder fibers that cannot maintain their fibrous shape while forming a support melt due to moist heat during the support manufacturing process, forming a film that fills the gaps between the fibers. As a result, their use is undesirable because it hinders the penetration and permeation of the solid electrolyte slurry into the support. Therefore, it is preferable that the support does not contain synthetic resin binder fibers that do not maintain their fibrous shape when the support is formed. However, synthetic resin binder fibers may be included if they can maintain their fibrous 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% or more by mass 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 explained. 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 having a configuration in which the solid electrolyte and the support are integrated.

[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 by selecting the materials that constitute the all-solid-state battery, it can be formed into, for example, a lithium-ion secondary battery, a sodium-ion secondary battery, etc. 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 secondary batteries, 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 and negative electrodes of an all-solid-state battery according to various carrier ions is acceptable.

[0047] The positive electrode is formed by 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 must be made of a material capable of intercepting and releasing lithium ions.

[0048] For example, aluminum can be used as the positive electrode current collector. Examples of positive electrode active materials include sulfide-based materials such as titanium sulfide (TiS2), molybdenum sulfide (MoS2), iron sulfide (FeS, FeS2), copper sulfide (CuS), and nickel sulfide (Ni3S2). Oxide-based materials include bismuth oxide (Bi2O3), bismuth leadate (Bi2Pb2O5), copper oxide (CuO), and vanadium oxide (V6O). 13 Examples include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2), Li(NiCoMn)O2, Li(NiCoAl)O2, and Li(NiCo)O2. It is also possible to use mixtures of these.

[0049] Furthermore, the negative electrode is formed by 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, metallic lithium, metallic indium, or a material capable of intercalating and releasing lithium ions can be used as the negative electrode active material.

[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 a all-solid-state battery, the solid electrolyte layer is configured as a solid electrolyte sheet in which the solid electrolyte is held on a support. The type of the solid electrolyte constituting the solid electrolyte sheet is not particularly limited, and for example, known materials that can be used as the solid electrolyte of the all-solid-state battery can be used. Further, the solid electrolyte is not particularly limited as long as it can conduct carrier ions between the positive electrode and the negative electrode. Examples thereof include oxide-based solid electrolytes and sulfide-based solid electrolytes. Further, other components such as a binder may be added as necessary.

[0053] For example, examples of the sulfide-based solid electrolyte capable of lithium ion conduction include sulfide-based amorphous solid electrolytes and sulfide-based crystalline solid electrolytes. Specific examples of the sulfide-based amorphous solid electrolyte include Li2S-SiS2, Li2S-GeS2, Li2S-P2S5, Li2S-B2S3, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li2SO4, Li2S-P2S5-LiI, Li2S-P2S5-P2O5-LiI, Li2S-B2S3-LiI, Li2S-P2S5-Li2O-LiI, Li2S-SiS2-B2S3-LiI, and the like. Note that the sulfide-based amorphous solid electrolyte may contain other elements. Further, specific examples of the sulfide-based crystalline solid electrolyte include Li 3.25 Ge 0.25 P 0.75 S4, and Li 10 GeP2S 12 , Li6PS5Cl, and the like, but the sulfide-based crystalline solid electrolyte is not limited to these element 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 the solid electrolyte sheet 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 coating the prepared slurry onto 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, but examples include slide die coating, comma die coating, comma reverse coating, gravure coating, and gravure reverse coating. Drying after coating a slurry containing a solid electrolyte can be performed, for example, using a drying apparatus that utilizes hot air, a heater, high frequency, etc.

[0057] The solid electrolyte sheet can be used as is, dry, but its mechanical strength and density can be further increased by applying pressure. Methods of applying pressure 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] [Manufacturing method for 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, positive electrode, and negative electrode and then pressing and crimping them together, or a method of applying pressure by passing the material between two rolls (roll-to-roll). Furthermore, in order to improve the adhesion between the solid electrolyte layer and the positive or 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. [Examples]

[0060] The following describes specific examples of the support according to the embodiments of the present invention. First, the supports for Examples 1-5 and Comparative Examples 1-10 were prepared using the following methods. Except for Comparative Example 2, the supports were prepared as paper or wet-laid nonwoven fabric using the 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 composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 60% by mass.

[0062] [Example 2] Using a raw material mixture consisting of 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, resulting in 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 combined 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 composition 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 combined 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, resulting in a thickness of 45 μm and a basis weight of 7.0 g / m². 2 , density 0.16g / cm 3A support was obtained. The composition 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, referencing the support manufacturing method 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 combined 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 combined 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, resulting in 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 blending 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 mixture consisting of 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, paper was made using a long screen, resulting in a thickness of 3 μm and a basis weight of 1.5 g / m². 2 , density 0.50g / cm 3 A support was obtained. The combined ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0073] [Comparative Example 8] Using a raw material mixture consisting of 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, paper was made using a short-mesh papermaking process, resulting in a thickness of 55 μm and a basis weight of 13.9 g / m². 2 , density 0.25g / cm 3 A support was obtained. The combined ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 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, paper was made using a short mesh method, resulting in a thickness of 5 μm and a basis weight of 0.8 g / m². 2 , density 0.16g / cm 3 A support was obtained. The combined ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 100% by mass.

[0075] [Comparative Example 10] Using a raw material mixture consisting of 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, paper was made using a circular mesh, resulting in a thickness of 40 μm and a basis weight of 15.5 g / m². 2 , density 0.39g / cm 3 A support was obtained. The composition ratio of polyester fibers, cellulose fibers, and polyamide fibers in the obtained support was 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) A mixture of LiNiCoAlO2 ternary powder was used as the positive electrode active material, Li2S-P2S5 amorphous powder as the sulfide-based solid electrolyte, and 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) A negative electrode coating solution was prepared by mixing graphite as the negative electrode active material, Li2S-P2S5 amorphous powder as the sulfide-based solid electrolyte, PVdF (polyvinylidene fluoride) as the binder, and NMP (N-methyl-2-pyrrolidone) as the solvent. The negative electrode structure was obtained by coating a copper foil current collector, which was the negative electrode current collector, with the negative electrode coating solution, drying it, and then rolling it.

[0078] (Solid electrolyte sheet) A solid electrolyte slurry was prepared by mixing Li2S-P2S5 amorphous powder as a sulfide-based solid electrolyte, SBR as a binder, and xylene as a solvent. A solid electrolyte slurry was applied to the support of each of the above examples and comparative examples, and dried to obtain a solid electrolyte sheet.

[0079] [Manufacturing of all-solid-state batteries] A single cell of an all-solid-state battery was obtained by laminating an 88mm x 58mm negative electrode structure, a 92mm x 62mm solid electrolyte sheet, and an 87mm x 57mm positive electrode structure, then dry laminating and bonding them together. The obtained single cells were placed in aluminum laminate film with terminals attached, degassed, heat-sealed, and packaged.

[0080] [Method for measuring the characteristics of support materials and all-solid-state batteries] The properties 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 measurement was performed using the apparatus described in "JIS P 8226-2 'Pulps - Determination of Fibre length by automated optical analysis - Part 2: Unpolarized light method'" (ISO 16065-2 'Pulps - Determination of Fibre length by automated optical analysis - Part 2: Unpolarized light method'), specifically the Fiber Tester PLUS (manufactured by Lorentzen & Wettre), and the length-loaded average fiber length was defined 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. Consequently, the fiber length of polyester fibers was measured using the following method. First, slides were prepared with fibers randomly dispersed. Then, the fiber length of the fibers on the slides 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 'Electrolytic cellulose paper - Part 2: Test methods' 5.1 Thickness," with the measuring force set to 1.5N 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] [Basic 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 / cm 3 ) = W / T W:Basic weight (g / m 2 ), T: thickness (μm)

[0086] [Porosity] The porosity of the support was calculated using the following formula. In cases where multiple materials were mixed to constitute the support, the average specific gravity of the constituent fibers was determined by performing a calculation proportional to the mixing ratio before calculating the porosity. Porosity (%)=(1-(D / S))×100 D: Support density (g / cm 3 ), S: Specific gravity of constituent fibers (g / cm³) 3 )

[0087] [Tensile strength] According to the method specified in "JIS P 8113 'Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method'" (ISO 1924-2 'Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method'), the maximum tensile load in the longitudinal direction (manufacturing direction) of the support was measured over a test width of 50 mm, and this was determined as the tensile strength of the support.

[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 elongation method'" (ISO 1924-2 'Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method'), and the modulus of elasticity was determined by the method described in "10.8 Tensile modulus of elasticity".

[0089] [Assessment of independence] The self-supporting properties of each solid electrolyte sheet that was fabricated were evaluated. When a 92mm x 62mm solid electrolyte sheet was lifted while holding the short edge, a "○" was given if no cracks or fissures were visible to the naked eye, and a "×" was given if cracks or fissures were visible to the naked eye when lifted.

[0090] [Internal resistance of solid electrolyte sheet] Solid-state batteries were 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 to 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 sheet] Solid-state 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] [Table 1]

[0094] [Table 2]

[0095] The evaluation results of all-solid-state batteries using the supports of each example and comparative example will be described in detail below. The solid electrolyte sheets using the supports of each embodiment were able to form self-supporting solid electrolyte sheets. Furthermore, the all-solid-state batteries using the supports of each embodiment 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. The support in Comparative Example 1 is composed of a polypropylene-polyethylene core sheath, and therefore melted when the solid electrolyte slurry was dried, failing to maintain its shape. As a result, it is believed that a self-supporting solid electrolyte sheet could not be obtained. Furthermore, 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 in Comparative Example 1 would have 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 solid-state batteries using the supports of Comparative Example 2 and Comparative Example 5 have higher resistance and lower discharge capacity compared to the solid-state batteries using the supports of each embodiment. Furthermore, the supports of Comparative Example 2 and Comparative Example 5 have lower elastic modulus compared to the supports of each embodiment. The supports in Comparative Examples 2 and 5 have a low elastic modulus of 0.2 GPa, resulting in excessive flexibility to stress. Therefore, it is believed that the stress applied due to the volume changes of the positive and negative electrodes caused the carrier ion pass lines formed within the solid electrolyte layer of the supports in Comparative Examples 2 and 5 to be severed.

[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 preferably consists 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 did not exhibit self-supporting properties. The supports of Comparative Example 3 and Comparative Example 9 had a basis weight of 0.8 g / m² compared to each of the examples. 2Because the tensile strength of the support was low, 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, by comparing each example with Comparative Example 3 and Comparative Example 9, the basis weight of the support is 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 support in Comparative Example 4 has a high elastic modulus of 11.3 GPa. Therefore, it is thought that the support lacked flexibility under stress, and the solid electrolyte sheet was unable to 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, leading to an increase in interfacial resistance. In other words, from a comparison between each example and Comparative Example 4, it can be seen that the elastic modulus of the support is preferably 10 GPa or less.

[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 fibrous shape, instead forming a film. This is thought to have inhibited the penetration of the solid electrolyte slurry into the support. In other words, a comparison of each example with 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 support of each example. The support of Comparative Example 8 is thicker than that of each example. In Comparative Example 8, the support was thick at 55 μm, which likely resulted in a thick solid electrolyte sheet with high resistance and low discharge capacity. In other words, from a 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 support of each example. In addition, the support of Comparative Example 10 has a higher basis weight compared to the support of each example. The support material of Comparative Example 10 has a basis weight of 15.5 g / m². 2 Because 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, by comparing each example with Comparative Example 10, the basis weight of the support was 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 the supports of Examples 2 and 5, at 0.3 GPa compared to 0.5 GPa for the supports of Examples 2 and 5. Furthermore, 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. In addition, the elastic modulus of the support of Example 4 is higher at 9.8 GPa compared to the support of Example 3, which has an elastic modulus of 8.8 GPa. In other words, a comparison between Examples 1 and 4 and Examples 2, 3, and 5 shows that an elastic modulus of 0.4 to 9 GPa is more preferable for the support.

[0107] The above-described embodiment is merely an example, and for example, the composition of the carrier ions, solid electrolyte, positive electrode, negative electrode, etc., can be appropriately modified by those skilled in the art. As explained above, by using a support with an elastic modulus of 0.3 to 10 GPa, which includes at least one fiber selected from polyester fibers, cellulose fibers, and polyamide fibers, and is made up of at least one selected from paper and nonwoven fabrics, the flexibility of the resulting solid electrolyte layer can be appropriately controlled, allowing the solid electrolyte layer to follow the volume changes caused by the positive and negative electrodes well. As a result, the disruption of the carrier ion pass lines inside the resulting solid electrolyte sheet can be suppressed, and the adhesion between the formed positive electrode-solid electrolyte layer and the solid electrolyte layer-negative electrode can be maintained. Consequently, 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 consisting only of fibers contained in the solid electrolyte layer of a secondary battery, It consists of at least one material selected from paper and nonwoven fabrics. It comprises at least one selected from polyester fibers, cellulose fibers, and polyamide fibers, The modulus of elasticity is in the range of 0.3 to 10 GPa. Support for secondary batteries.

2. Contains at least 60% by mass of at least one selected from polyester fibers, cellulose fibers, and polyamide fibers. Support for a secondary battery according to claim 1.

3. Thickness: 5–50 μm, Basis weight: 1.0–15.0 g / m² ２ It is within the range Support for a secondary battery according to claim 1 or 2.

4. A solid electrolyte sheet comprising a membrane-like support and a solid electrolyte held in the support, The aforementioned support is It consists of at least one selected from paper and nonwoven fabrics, and includes at least one selected from polyester fibers, cellulose fibers and polyamide fibers. The modulus of elasticity is in the range of 0.3 to 10 GPa. Solid electrolyte sheet.

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, The aforementioned solid electrolyte sheet is A support comprising 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, The solid electrolyte is held in the support, Secondary battery.

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