THIN FILM FOR SOLID BATTERY

Abstract

The object of the present invention is to provide a thin film for a solid-state battery which, due to its low residual solvent content, has a less detrimental effect on the performance of the solid-state battery and can be produced by a continuous roll-to-roll coating process. The present invention relates to a thin film for a solid-state battery 100, comprising solid electrolyte particles 110 and crystalline fluororesin 120 and 130, which binds the solid electrolyte particles 110 together, wherein at least a portion 130 of the crystalline fluororesin has a fibrous form and the content of volatile components, measured by a gas analyzer, is 10 ppm by mass or less.

Description

AREA

[0001] The present invention relates to a thin film for a solid-state battery. BACKGROUND

[0002] A solid-state battery is a secondary battery that incorporates a solid electrolyte as its electrolyte and attracts attention due to its higher performance in terms of charging power and the like, compared to a liquid electrolyte battery, which uses only a liquid electrolyte as its electrolyte. A film deposition process is generally known for the layer of active material of the positive electrode, a solid electrolyte, or a layer of active material of the negative electrode included in such a solid-state battery (each of the three layer types is referred to below as a thin film for a solid-state battery). This process involves forming a suspension or slurry by containing each component in a solvent, and then coating and drying the suspension (a suspension film deposition process or slurry deposition process, respectively).

[0003] However, the suspension film deposition process involves a drying process and therefore requires high energy consumption and equipment costs. On the other hand, a film deposition process that does not use a solvent (a dry film deposition process) has been proposed.

[0004] For example, PTL 1 discloses a positive electrode for a secondary battery comprising a positive electrode containing at least one active material of the positive electrode and a solid electrolyte, wherein the amount of oil absorbed within and between primary particles of active material of the positive electrode, expressed as the amount of linseed oil, is 35 to 50 ml per 100 g. The average particle size of a solid electrolyte particle is 1.5 to 2.5 µm, and the layer of active material of the positive electrode is formed by mixing the active material of the positive electrode with the solid electrolyte particles without solvents or pressing the mixture.PTL 1 states that the invention in PTL 1 can provide a positive electrode for a secondary battery with a high capacity retention rate, a method for producing the positive electrode for a secondary battery and a solid-state battery comprising the positive electrode. [CITING LIST][PATENT LITERATURE]

[0005] [PTL 1] Japanese unpublished patent application (Kokai) No. 2014-143133 SUMMARY [TECHNICAL PROBLEM]

[0006] The inventors have found that the presence of a large amount of solvent residue in a thin film for a solid-state battery can impair the performance of the battery. Conversely, the formation of a thin film for a solid-state battery using the dry coating process described in PTL 1 can reduce the amount of solvent residue in the thin film.

[0007] However, to perform film deposition for a battery in an efficient manufacturing process at low cost, a thin film for a solid-state battery must be produced using a continuous roll-to-roll coating process, similar to conventional methods. The problem is that the flexibility of a thin film for a solid-state battery is low when dry-deposited using a batch pressure forming process described in PTL 1, and the continuous roll-to-roll coating process is not practical.

[0008] The aim of the present invention is to provide a thin film for a solid-state battery which, due to its low residual solvent content, impairs the performance of a solid-state battery less and can be produced by the continuous roll-to-roll coating process. [SOLUTION TO THE PROBLEM]

[0009] The present invention achieves the aforementioned goal by the following means. <Aspekt 1 >

[0010] A thin film for a solid-state battery comprising one or more solid electrolyte particles and crystalline fluororesin that binds the solid electrolyte particles together, wherein at least part of the crystalline fluororesin has a fibrous form and the content of a volatile component(s), measured with a gas analyzer, is 10 ppm by mass or less. <Aspekt 2>

[0011] The thin film for a solid-state battery according to aspect 1, wherein the content of the volatile component is 1 ppm mass fraction or less. <Aspekt 3>

[0012] The thin film for a solid-state battery according to aspect 1 or 2, wherein the particle diameter of the solid electrolyte particles is 1.0 µm or less. <Aspekt 4>

[0013] The thin film for a solid-state battery according to one of aspects 1 to 3, wherein the content of crystalline fluorinated resin is 1.0 mass percent or less. <Aspekt 5>

[0014] The thin film for a solid-state battery according to one of aspects 1 to 4, where the content of crystalline fluorinated resin is 0.6 mass percent or more. <Aspekt 6>

[0015] The thin film for a solid-state battery according to one of aspects 1 to 5, where the solid electrolyte particle is a sulfide solid electrolyte particle. <Aspekt 7>

[0016] The thin film for a solid-state battery according to one of aspects 1 to 6, wherein the crystalline fluoropolymer is polytetrafluoroethylene, a perfluoroalkyl compound, a polyfluoroalkyl compound or a combination of the foregoing. <Aspekt 8>

[0017] The thin film for a solid-state battery according to one of aspects 1 to 7, wherein the thin film is a layer of active material of the positive electrode, which additionally contains an active material of the positive electrode. <Aspekt 9>

[0018] The thin film for a solid-state battery according to one of aspects 1 to 7, wherein the thin film is a solid electrolyte layer. <Aspekt 10>

[0019] The thin film for a solid-state battery according to one of aspects 1 to 7, wherein The thin film is a layer of active material of the negative electrode, which additionally contains an active material of the negative electrode. <Aspekt 11>

[0020] A solid-state battery comprising a layer of positive electrode active material, a solid electrolyte layer, and a layer of negative electrode active material in that order, wherein at least one layer selected from the layer of positive electrode active material, the solid electrolyte layer, and the layer of negative electrode active material is the thin film for a solid-state battery according to any one of aspects 1 to 7. [ADVANTAGES OF THE INVENTION]

[0021] The present invention can provide a thin film for a solid-state battery which, due to its low residual solvent content, impairs the performance of a solid-state battery less and can be produced by a continuous roll-to-roll coating process. BRIEF DESCRIPTION OF THE DRAWINGS Fig.Figure 1 is a schematic cross-sectional view illustrating a thin film for a solid-state battery according to the present invention; and Fig. Figure 2 is a schematic cross-sectional view to illustrate a solid-state battery according to the present invention. DESCRIPTION OF EXECUTION FORMS<<Dünne Folie für Festkörperbatterie> >

[0022] A thin film for a solid-state battery according to the present invention comprises solid electrolyte particles and a crystalline fluorine resin that binds the solid electrolyte particles together, wherein at least part of the crystalline fluorinated resin has a fibrous form and The content of volatile components, measured with a gas analyzer, is 10 ppm by mass or less.

[0023] The present invention can provide a thin film for a solid-state battery which, due to its low residual solvent content, impairs the performance of a solid-state battery less and can be produced by a continuous roll-to-roll coating process.

[0024] The performance of a solid-state battery can be impaired by the presence of a large amount of residual solvent, i.e., volatile components, in the thin film used for the solid-state battery. Without being limited to a specific theory, it is thought that this is because some of the particles contained in the thin film, such as solid electrolyte particles, are coated with a decomposition product of the volatile components.

[0025] On the other hand, the inventors have found that if the content of volatile components in a thin film for a solid-state battery is 10 ppm by mass or less, the reduction or deterioration of the performance of a solid-state battery can be suppressed and advantageous physical properties can be achieved as a solid-state battery.

[0026] Furthermore, the inclusion of crystalline fluoropolymer as a binder in a thin film for a solid-state battery enables high flexibility after film deposition. While not limited to theory, it is assumed that the improved flexibility is due to the application of shear forces to the aforementioned crystalline fluoropolymer, which can make it fibrous and promote bonding between solid electrolyte particles.

[0027] In particular, this includes, for example, as in Fig.Figure 1 shows a thin film for a solid-state battery 100 according to the present invention, comprising solid electrolyte particles 110, crystalline fluororesin particles 120, and crystalline fluororesin fibers 130, which are formed by the fiber formation of a portion of the crystalline fluororesin particles 120. The solid electrolyte particles 110 are then interconnected by the crystalline fluororesin particles 120 and also by the crystalline fluororesin fibers 130. Accordingly, the thin film for a solid-state battery 100 exhibits high flexibility.

[0028] The individual components of the present invention are described below.

[0029] A “thin film for a solid-state battery” here refers to a layer of active material of the positive electrode, a solid electrolyte layer, or a layer of active material of the negative electrode contained in a solid-state battery. The thin film for a solid-state battery according to the present invention can be applied to one type of layer or to two or more types.

[0030] The term "solid-state battery" here refers to a battery that uses at least solid electrolyte particles as the electrolyte, and therefore a solid-state battery can also use a combination of solid electrolyte particles and a liquid electrolyte as the electrolyte. Furthermore, the term "solid-state battery" here can refer to a solid-state battery in which only solid electrolyte particles are used as the electrolyte.

[0031] The thin film for a solid-state battery comprises solid electrolyte particles and crystalline fluoropolymer resin that binds the solid electrolyte particles together. The crystalline fluoropolymer resin acts as a binder, and a thin film for a solid-state battery can exhibit high flexibility because the solid electrolyte particles are bonded together by the crystalline fluoropolymer resin.

[0032] The content of crystalline fluororesin is not particularly limited, but can be 1.0% or less by mass, 0.9% or less by mass, or 0.8% or less by mass, based on the thin film used in a solid-state battery. Factors that affect the performance of a solid-state battery include the presence of additives that impede contact between solid electrolyte particles and reduce lithium-ion conductivity. Accordingly, incorporating a large amount of crystalline fluororesin into the thin film of a solid-state battery to improve its flexibility reduces ion conductivity.

[0033] The content of crystalline fluorinated resin is not particularly limited, but is preferably 0.6% by mass or more, or 0.7% by mass or more, based on the thin film for a solid-state battery, to ensure the flexibility of the thin film for a solid-state battery.

[0034] The solid electrolyte particle content is not particularly limited and can be appropriately determined according to the application, performance, and the like of the thin film for a solid-state battery. For example, the solid electrolyte particle content can be 1% or more by mass, 5% or more by mass, 10% or more by mass, 15% or more by mass, or 20% or more by mass, and can be 90% or less by mass, 80% or less by mass, 70% or less by mass, 60% or less by mass, or 50% or less by mass.

[0035] The solid electrolyte particles and the particles contained in the thin film for a solid-state battery, with the exception of the solid electrolyte particles, may be bonded together by the crystalline fluoropolymer resin. Examples of the aforementioned particles contained in the thin film for a solid-state battery, with the exception of the solid electrolyte particles, include particles of an active material for the positive electrode, an active material for the negative electrode, and a conductive additive.

[0036] The volatile content in the thin film for a solid-state battery according to the present invention, measured with a gas analyzer, is 10 ppm by mass or less. The amount of volatile components is preferably minimized to prevent a reduction or deterioration of battery performance. The aforementioned content can be 8 ppm by mass or less, 6 ppm by mass or less, 4 ppm by mass or less, 2 ppm by mass or less, or 1 ppm by mass or less. Furthermore, the aforementioned content can be 1 ppm by mass or more, 10 ppm by mass or more, or 100 ppm by mass or more. If multiple types of volatile components are present, the aforementioned content refers to the content of each individual volatile component.

[0037] The concentration of volatile components was measured using a gas analyzer. This analyzer performs qualitative and quantitative analysis of a target solvent using temperature-programmed desorption mass spectrometry (TPD-MS) with a mass spectrometer (GC / MS-QP2010, manufactured by Shimadzu Corporation) equipped with an integrated heating device. Helium is used as the carrier gas and is heated to 250 °C by the heating device at a rate of 10 degrees per minute.

[0038] A "volatile component" here refers to a solvent used in the manufacture of a thin film for a solid-state battery and is a component that remains in the thin film. Examples of solvents include alcohols such as methanol, ethanol, propanol, and butanol; aliphatic hydrocarbons such as hexane and heptane; ketones such as acetone, methyl ethyl ketone, and 2-pentanone; and esters such as ethyl acetate and butyl acetate.

[0039] The flexibility of the thin film for a solid-state battery is not particularly limited and can be appropriately determined according to the required power output of the solid-state battery, etc. For example, the flexibility of the thin film for a solid-state battery can be measured as the diameter of a cylinder at which cracks begin to form in the active material layer of the electrode when a laminate comprising the thin film is wound around the cylinder in a cylindrical mandrel test; and the diameter can be 45 mm or less, 40 mm or less, 35 mm or less, 30 mm or less, 25 mm or less, or 20 mm or less, and can be 5 mm or more, 10 mm or more, or 15 mm or more.

[0040] For example, the shape of the thin film for a solid-state battery is not particularly restricted; it can be a sheet shape with a nearly flat surface. Similarly, the thickness of the thin film for a solid-state battery is not particularly restricted; it can be 0.1 µm or more, 1 µm or more, or 10 µm or more, and can be 2 mm or less, 1 mm or less, or 500 µm or less.

[0041] The method for applying a thin film for a solid-state battery is not particularly limited, but preferably the layer is formed by a dry coating process which does not require volatile components in order to reduce the volatile content in the thin film for a solid-state battery. <festelektrolytpartikel>

[0042] The solid electrolyte particle diameter can be 1.0 µm or less. A smaller particle diameter can improve the flexibility of the thin film for a solid-state battery. While not strictly theoretical, it is thought that a smaller solid electrolyte particle diameter allows the solid electrolyte particles to efficiently apply shear forces to the crystalline fluoropolymer when the solid electrolyte particles and the crystalline fluoropolymer are kneaded together, resulting in an increased amount of fibrous crystalline fluoropolymer. The solid electrolyte particle diameter can be 0.9 µm or less, 0.8 µm or less, 0.7 µm or less, or 0.5 µm or less, and can be 0.1 µm or more, 0.2 µm or more, or 0.3 µm or more.

[0043] The particle diameter of the solid electrolyte particles is a particle diameter (a median diameter) at a cumulative value of 50% in the volume-based particle size distribution determined by a laser diffraction and scattering method.

[0044] The solid electrolyte particles are not limited, but can be sulfide solid electrolyte particles. Other examples of solid electrolyte particles include oxide solid electrolyte particles and polymer electrolyte particles.

[0045] Examples of sulfide solid electrolyte particles can include, but are not limited to, amorphous sulfide solid electrolyte particles, crystalline sulfide solid electrolyte particles, and argyrodite solid electrolyte particles. Specific examples of sulfide solid electrolyte particles include Li₂S-P₂S₅-based particles (e.g., Li₇P₃S₅). 11 , Li3PS4 and Li8P2S9), Li2S-SiS2, Lil-Li2S-SiS2, LiI-Li2S-P2S5, Lil-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (e.g. Li 13 GeP3S 16 and Li 10 GeP2S 12 ), Lil-Li2S-P2O5, Lil-Li3PO4-P2S5, Li 7-x PS 6-x Cl x and combinations thereof, but are not limited to these.

[0046] Examples of oxide solid electrolyte particles include Li7La3Zr2O 12 , Li 7-x La3Zr 1-x Note x O 12 , Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO4 -x N x (LiPON) and combinations thereof, but are not limited to these.

[0047] The sulfide solid electrolyte particles and the oxide solid electrolyte particles can be based on glass or crystalline glass (glass ceramics).

[0048] Examples of polymer electrolyte particles include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO) and copolymers thereof. <Kristallines Fluorharz>

[0049] At least a portion of the crystalline fluoropolymer exhibits a fibrous form. This fibrous structure improves the bonding properties between solid electrolyte particles and enables high flexibility.

[0050] Examples of crystalline fluoropolymers include, but are not limited to, polytetrafluoroethylene (PTFE), perfluoroalkyl compounds, and polyfluoroalkyl compounds. A single type of crystalline fluoropolymer can be used alone, or two or more types can be used in combination.

[0051] Examples of perfluoroalkyl compounds include perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS).

[0052] Examples of polyfluoroalkyl compounds include polyfluoroalkyl vinyl ethers (PFA) and polyfluoroalkyl acrylate (PFAA).

[0053] The crystalline fluororesin can comprise resin with a particle shape. The particle diameter of the crystalline fluororesin can be 0.5 µm or less, 0.4 µm or less, 0.3 µm or less, 0.2 µm or less, or 0.1 µm or less, and can be 0.01 µm or more, 0.03 µm or more, or 0.05 µm or more, but is not specifically limited to these values. The particle diameter of the crystalline fluororesin is a particle diameter (a median diameter) at a cumulative value of 50% in the volume-based particle size distribution determined by the laser diffraction and scattering method.

[0054] Examples of the process for producing the fibrous crystalline fluorinated resin are not particularly limited, but may include the fibrous formation of a portion of the particulate crystalline fluorinated resin by kneading the crystalline fluorinated resin with solid electrolyte under the application of a shear force. <Schicht aus aktivem Material der positiven Elektrode>

[0055] The thin film for solid-state batteries can be a layer of positive electrode active material that additionally contains a positive electrode active material. In this case, the positive electrode active material layer contains at least one positive electrode active material, solid electrolyte, and crystalline fluoropolymer resin, and may optionally contain a conductive additive. For the solid electrolyte particles, see the preceding description of solid electrolyte particles; for the crystalline fluoropolymer resin, see the preceding description of crystalline fluoropolymer resin. Furthermore, the positive electrode active material layer may also contain various additives.

[0056] The content of the positive electrode active material, solid electrolyte particles, and conductive additive in the positive electrode active material layer can be appropriately determined according to the desired battery performance. For example, if the total positive electrode active material layer (the total solids content) is assumed to be 100% by mass, the positive electrode active material content can be 40% or more by mass, 50% or more by mass, or 60% or more by mass, and can be 100% or less by mass, or 90% or less by mass. (Active material of the positive electrode)

[0057] The material for the active material of the positive electrode is not particularly restricted, as long as the material can trap and release lithium ions. Examples of active materials for the positive electrode include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), and lithium nickel manganese cobalt oxide (NCM: LiCo). 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel cobalt aluminum oxide [LiNi 0,8 (CoAl) 0,2 O2] and Li-Mn spinels substituted by heteroelements, whose composition is modified by Li 1+x Mn 2-x-y M y O4 (where M is one or more metallic elements selected from Al, Mg, Co, Fe, Ni and Zn) is represented as an example of the active material of the positive electrode, but is not limited to it.

[0058] The active material of the positive electrode is not particularly restricted, but it may include a cover layer. The cover layer is a layer containing a material with lithium-ion conductivity, exhibiting low reactivity with the active material of the positive electrode and the solid electrolyte particles, and capable of maintaining a shape that does not flow or condense even when the cover layer comes into contact with the active material or the solid electrolyte particles. Specific examples of the material used in the layer include LiNbO3 and Li4Ti5O. 12 and Li3PO4, but are not limited to them.

[0059] The shape of the positive electrode active material is not specifically restricted, as long as it is a shape commonly used for positive electrode active material in a battery. For example, the positive electrode active material can have a particle shape. The positive electrode active material can consist of primary particles or secondary particles formed by the aggregation of multiple primary particles. For example, the particle diameter of the positive electrode active material can be 1 nm or larger, 5 nm or larger, or 10 nm or larger, and can be 500 µm or less, 100 µm or less, 50 µm or less, or 30 µm or less.It should be noted that the particle diameter of the active material of the positive electrode is a particle diameter (a median diameter) at a cumulative value of 50% in the volume-based particle size distribution, which was determined by the laser diffraction and scattering method. (Conductive additive)

[0060] The conductive additive is not particularly restricted. Examples of the conductive additive may include, but are not limited to, steam-grown carbon fibers (VGCF), carbon black (AB), carbon black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF). The conductive additive may, for example, have a particulate or fibrous form, and its size is not particularly restricted. The conductive additive is not particularly restricted, but it may be one type alone or two or more types in combination. <festelektrolytschicht>

[0061] The thin film for a solid-state battery can be a solid electrolyte layer. In this case, the solid electrolyte layer contains at least solid electrolyte particles and crystalline fluoropolymer resin and may optionally contain a conductive additive. For the solid electrolyte particles, see the preceding description of solid electrolyte particles; for the conductive additive, see the preceding description of conductive additive. Furthermore, the solid electrolyte layer may also contain various other additives. <Schicht aus aktivem Material der negativen Elektrode>

[0062] The thin film for a solid-state battery can be a layer of negative electrode active material that additionally contains a negative electrode active material. In this case, the negative electrode active material layer contains at least a negative electrode active material, solid electrolyte, and crystalline fluoropolymer resin, and may optionally contain a conductive additive. For the solid electrolyte particles, see the preceding description of solid electrolyte particles; for the crystalline fluoropolymer resin, see the preceding description of crystalline fluoropolymer resin; and for the conductive additive, see the preceding description of conductive additive. Furthermore, the negative electrode active material layer may also contain various additives.

[0063] The content of the negative electrode active material, solid electrolyte particles, and conductive additive in the negative electrode active material layer can be appropriately determined according to the desired battery performance. For example, if the total negative electrode active material layer (the total solids content) is assumed to be 100% by mass, the negative electrode active material content can be 40% or more by mass, 50% or more by mass, or 60% or more by mass, and can be 100% or less by mass, or 90% or less by mass. (Active material of the negative electrode)

[0064] Various materials can be used as the active material of the negative electrode, provided they exhibit a potential at which lithium ions are trapped and released (a charge and discharge potential) that is lower than that of the active material of the positive electrode according to the present invention. The material for the active material of the negative electrode can be metallic lithium or a material capable of trapping and releasing metal ions, such as lithium ions, but is not specifically limited to this. Examples of materials capable of trapping and releasing metal ions, such as lithium ions, include alloy-based active materials of the negative electrode, carbon materials, and lithium titanate (Li₄Ti₅O₆). 12 ) include, but are not limited to.

[0065] Examples of alloy-based negative electrode active materials include, but are not limited to, silicon alloy-based and tin alloy-based negative electrode active materials. Examples of silicon alloy-based negative electrode active materials include silicon, silicon oxides, silicon carbides, silicon nitrides, and their solid solutions. Furthermore, silicon alloy-based negative electrode active materials can contain metallic elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Examples of tin alloy-based negative electrode active materials include tin, tin oxides, tin nitrides, and their solid solutions.Furthermore, the active materials of the negative electrode based on a tin alloy can contain metallic elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti and Si.

[0066] Examples of carbon materials include hard carbon, soft carbon and graphite, but are not specifically limited to these.

[0067] The shape of the active material of the negative electrode is not particularly restricted and simply needs to be a shape commonly used as active material for the negative electrode in a battery. For example, the active material of the negative electrode can be in a particle or sheet shape. <<Festkörperbatterie> >

[0068] A solid-state battery according to the present invention comprises a layer of active material of the positive electrode, a solid electrolyte layer and a layer of active material of the negative electrode in this order, wherein at least one layer selected from the aforementioned layer of active material of the positive electrode, the aforementioned solid electrolyte layer and the aforementioned layer of active material of the negative electrode is the thin film for a solid-state battery according to the present invention.

[0069] The present invention can provide a solid-state battery comprising a thin film for a solid-state battery which, due to its low residual solvent content, impairs the performance of a solid-state battery less and can be produced by a continuous roll-to-roll coating process.

[0070] The solid-state battery according to the present invention comprises at least one layer of active material of the positive electrode, a solid electrolyte layer and a layer of active material of the negative electrode in that order and may optionally include a current collector layer for the positive electrode, a current collector layer for the negative electrode and a liquid electrolyte.

[0071] In particular, for example, a solid-state battery 200 comprises a layer 210 of active material of the positive electrode, a solid electrolyte layer 220 and a layer 230 of active material of the negative electrode in that order, as shown in Fig. 1 shown.

[0072] At least one layer, selected from the active material layer of the positive electrode, the solid electrolyte layer, and the active material layer of the negative electrode, constitutes the thin film for a solid-state battery according to the present invention. Two or more of these layers can constitute the thin film for a solid-state battery according to the present invention. With regard to the active material layer of the positive electrode, reference can be made to the preceding description of the active material layer of the positive electrode; with regard to the solid electrolyte layer, reference can be made to the preceding description of the solid electrolyte layer; and with regard to the active material layer of the negative electrode, reference can be made to the preceding description of the active material layer of the negative electrode. <Stromabnehmerschicht für die positive Elektrode>

[0073] The material used for the current collector layer for the positive electrode is not particularly restricted, and a material commonly used as a positive electrode current collector in a solid-state battery may be used. Examples of materials used for the current collector layer for the positive electrode may include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. Furthermore, the current collector layer for the positive electrode may have a coating layer on its surface for the purpose of resistance adjustment and the like. The current collector layer for the positive electrode may also be obtained by plating a metal foil or substrate with the aforementioned metal or by depositing the metal onto the metal foil or substrate.

[0074] Examples of the shape of the current collector layer for the positive electrode are not particularly limited, but may include a foil shape, a plate shape, and a mesh shape. A foil shape is preferred. The thickness of the current collector layer for the positive electrode is not particularly limited, but may be 0.1 µm or more, 1 µm or more, 1 µm or less, or 100 µm or less. <Stromabnehmerschicht für die negative Elektrode>

[0075] The material used for the negative electrode current collector layer is not particularly limited, and a material generally used as a negative electrode current collector in a solid-state battery may be used appropriately. Examples of materials used for the negative electrode current collector layer may include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and a carbon plate. The negative electrode current collector layer may have a coating layer on its surface for the purpose of resistance adjustment and the like.

[0076] Examples of the shape of the current collector layer for the negative electrode are not particularly limited, but may include a foil shape, a plate shape, and a mesh shape. A foil shape is preferred. The thickness of the current collector layer for the negative electrode is not particularly limited, but may be 0.1 µm or more, 1 µm or more, 1 mm or less, or 100 µm or less. <Flüssiger Elektrolyt>

[0077] The liquid electrolyte is not particularly restricted, but preferably contains a carrier salt and a solvent.

[0078] Examples of the carrier salt (lithium salt) in a lithium-ion-conducting electrolyte solution are not particularly limited, but can include inorganic and organic lithium salts. Examples of inorganic lithium salts include, but are not limited to, LiPF6, LiBF4, LiClO4, and LiAsF6. Examples of organic lithium salts include, but are not limited to, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3.

[0079] Examples of solvents used in the electrolyte solution are not particularly limited, but may include cyclic and chain carbonates. Examples of cyclic carbonates include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of chain carbonates include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte solution is not particularly limited, but one type may be used alone, or two or more types may be used in combination. EXAMPLES

[0080] The present invention is specifically described by means of examples and comparative examples, but is not limited thereto. <<Herstellung einer dünnen Folie für eine Festkörperbatterie> ><Beispiele 1 bis 4>

[0081] As shown in Table 1, Li₂S-P₂S₅-based solid electrolyte particles were kneaded with PTFE, a crystalline fluorinated resin, as a binder under shear stress. The resulting mixture was pressed into a plate by a dry film deposition process and used as a thin film for a solid-state battery in Examples 1 to 4. <Vergleichsbeispiel 1>

[0082] As shown in Table 1, Li₂S-P₂S₅-based particles as solid electrolyte particles and PVDF as a binder were mixed in the presence of a solvent to obtain a slurry. This slurry was then coated using a doctor blade applicator and dried to form a thin film for a solid-state battery in Comparative Example 1. <Messung des Gehalts an flüchtigen Bestandteilen>

[0083] The amount of volatile components contained in the thin film for a solid-state battery in each of Examples 1 to 4 and the comparison example 1 was measured by qualitative and quantitative analysis of a target solvent using temperature-programmed desorption mass spectrometry (TPD-MS) with a mass spectrometer (GC / MS-QP2010, manufactured by Shimadzu Corporation) with an integrated heating device. It should be noted that helium was used as the carrier gas and heated to 250 °C by the heating device at a rate of 10 degrees per minute. The measurement results are presented in Table 1. < <bewertung>><Vorhandensein einer Zersetzung der Festelektrolytpartikel>

[0084] The presence of decomposition of the solid electrolyte particles was confirmed by ion conductivity measurement and elemental analysis. The evaluation criterion was as follows. A: Degradation of the solid electrolyte particles is not confirmed by ion conductivity measurement and elemental analysis. B: Degradation of the solid electrolyte particles is confirmed by ion conductivity measurement and elemental analysis. <Flexibilität der dünnen Folie für Festkörperbatterien>

[0085] The flexibility of the thin film for solid-state batteries in Examples 1 to 4 and Comparative Example 1 was evaluated by a cylindrical mandrel test, in which a laminate encompassing the thin film was wound around cylinders with diameters of 40 mm and 50 mm. The evaluation criterion was as follows. A: When wound onto the cylinder with a diameter of 40 mm, the thin film for a solid-state battery is not damaged and has sufficient flexibility. B: When wound onto the cylinder with a diameter of 50 mm, the thin film for a solid-state battery is not damaged and has sufficient flexibility. C: If the thin film for a solid-state battery is wrapped around the cylinder with a diameter of 50 mm, it will be damaged and will not have sufficient flexibility.

[0086] The evaluation results are shown in Table 1. [Table 1] Table 1 Example 1 Example 2 Example 3 Example 4 Comparative example 1 thin film for solid state battery Solid electrolyte particles Particle diameter (µm) 5 1 1 1 5 binder Art PTFE PTFE PTFE PTFE PVDF Content relative to the solid electrolyte layer (mass%) 3 3 0.5 1 3 Film deposition process Dry film deposition Dry film deposition Dry film deposition Dry film deposition Slurry coating Volatile component content (ppm mass fraction) < 1 < 1 < 1 < 1 800 Evaluation Presence of decomposition of the solid electrolyte A A A A B Flexibility of the thin film for solid-state batteries B A B A A

[0087] Examples 1 to 4 and the comparative example 1 in Table 1 show that with a low content of volatile components contained in the thin film for a solid-state battery, no degradation of the solid electrolyte is observed and the thin film for a solid-state battery does not impair the performance of the solid-state battery.

[0088] Examples 1 and 2 in Table 1 show that a smaller particle diameter of the solid electrolyte leads to an increased amount of fibrous crystalline fluorinated resin, resulting in greater flexibility of the solid electrolyte layer. Therefore, a smaller particle diameter of the solid electrolyte can be considered a more advantageous condition. LIST OF REFERENCE MARKS 100 thin foil sheets for solid-state batteries 110 solid electrolyte particles 120 crystalline fluorinated resin particles 130 Crystalline Fluororesin Fiber 200 solid-state batteries 210 Layer of active material of the positive electrode 220 solid electrolyte layer 230 Layer of active material of the negative electrode< / bewertung> < / festelektrolytschicht> < / festelektrolytpartikel>

Claims

Thin film for a solid-state battery comprising one or more solid electrolyte particles and crystalline fluororesin bonding the solid electrolyte particles together, wherein at least part of the crystalline fluororesin has a fibrous form and the content of a volatile component, as measured by a gas analyzer, is 10 ppm mass fraction or less. Thin film for a solid-state battery according to claim 1, wherein the content of the volatile component is 1 ppm by mass or less. Thin film for a solid-state battery according to claim 1 or 2, wherein the particle diameter of the solid electrolyte particle is 1.0 µm or less. Thin film for a solid-state battery according to one of claims 1 to 3, wherein the content of crystalline fluorinated resin is 1.0 percent by mass or less. Thin film for a solid-state battery according to one of claims 1 to 4, wherein the content of crystalline fluorinated resin is 0.6 percent by mass or more. Thin film for a solid-state battery according to one of claims 1 to 5, wherein the solid electrolyte particle is a sulfide solid electrolyte particle. Thin film for a solid-state battery according to any one of claims 1 to 6, wherein the crystalline fluoropolymer is polytetrafluoroethylene, a perfluoroalkyl compound, a polyfluoroalkyl compound or a combination of the foregoing. The thin film for a solid-state battery according to one of claims 1 to 7, wherein the thin film is a layer of active material of the positive electrode, which additionally contains an active material of the positive electrode. Thin film for a solid-state battery according to any one of claims 1 to 7, wherein the thin film is a solid electrolyte layer. Thin film for a solid-state battery according to one of claims 1 to 7, wherein the thin film is a layer of active material of the negative electrode, which further comprises an active material of the negative electrode. Solid-state battery comprising a layer of active material of the positive electrode, a solid electrolyte layer and a layer of active material of the negative electrode in that order, wherein at least one layer selected from the layer of active material of the positive electrode, the solid electrolyte layer and the layer of active material of the negative electrode is the thin film for a solid-state battery according to any one of claims 1 to 7.

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