Solid electrolyte material and battery

Abstract

The invention relates to a solid electrolyte material and a battery. A solid electrolyte material in which the solid electrolyte material contains a Li salt having a fluorine-containing anion, an inorganic filler surface-modified with a fluorinated alkyl group, and a polymer. The solid electrolyte material also includes butanedinitrile. The inorganic filler contains at least one selected from the group consisting of SiO2, TiO2, ZrO2, and MgO, and the fluorinated alkyl group contains at least one of a 1H, 1H, 2H, 2H-tridecafluoro n-octyl group, and a 1H, 1H, 2H, 2H-heptadecafluoro decyl group.

Description

Technical Field

[0001] This invention relates to solid electrolyte materials and batteries. Background Technology

[0002] Various technologies have been proposed regarding the solid electrolyte material disclosed in Japanese Patent Application Publication No. 2011-081934. Summary of the Invention

[0003] Japanese Patent Application Publication No. 2011-081934 discloses a solid electrolyte containing an ionic liquid, a compound capable of encapsulating anions, an electrolyte salt, and inorganic filler (inorganic compound particles) to provide a solid electrolyte with high lithium-ion mobility, excellent safety, durability, and good cycle performance. Japanese Patent Application Publication No. 2011-081934 describes that the compound capable of encapsulating anions is coordinated with the anions in the electrolyte salt, thus exhibiting an improvement in lithium-ion mobility.

[0004] In Japanese Patent Application Publication No. 2011-081934, it was found that when these components are mixed to prepare a solid electrolyte, it is difficult to uniformly disperse the compound with the function of encapsulating anions in the inorganic filler. As a result, it is difficult to obtain an improvement in the lithium-ion transference number.

[0005] The present invention was made in view of the above-mentioned actual situation, and its main purpose is to provide a solid electrolyte material with excellent lithium-ion transference number.

[0006] That is, the present invention includes the following methods.

[0007] <1>

[0008] A solid electrolyte material comprising a Li salt having a fluorine-containing anion, an inorganic filler, and a polymer, wherein the inorganic filler is surface-modified with a fluorinated alkyl group.

[0009] <2>

[0010] According to the solid electrolyte material described in <1>, the solid electrolyte material further comprises succinic anionyl nitrile.

[0011] <3>

[0012] According to the solid electrolyte material described in <1> or <2>, the inorganic filler comprises at least one selected from the group consisting of SiO2, TiO2, ZrO2 and MgO, and the fluorinated alkyl group comprises at least one of 1H,1H,2H,2H-tridecylfluorooctyl and 1H,1H,2H,2H-heptadecylfluorodecyl.

[0013] <4>

[0014] The solid electrolyte material according to any one of <1> to <3>, wherein the above-mentioned Li salt comprises at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium fluorosulfonyl(trifluoromethanesulfonyl)imide (LiFTFSI), LiPF6, LiBF4 and LiCF3SO3 (LiTfO).

[0015] <5>

[0016] A battery having a positive electrode layer, a negative electrode layer and an electrolyte layer, wherein the electrolyte layer comprises a solid electrolyte, and the solid electrolyte is any one of <1> to <4>.

[0017] According to the present invention, a solid electrolyte material with excellent lithium-ion transference number can be obtained. Attached Figure Description

[0018] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein the same symbols denote the same elements.

[0019] Figure 1 This is a schematic cross-sectional view illustrating the battery of the present invention. Detailed Implementation

[0020] The following describes embodiments based on the present invention. It should be noted that matters necessary for the implementation of the present invention, other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of solid electrolyte materials that do not impart features to the present invention), can be understood as design considerations for those skilled in the art based on prior art. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in the field.

[0021] In this invention, unless otherwise specified, the average particle size is the particle size at which the cumulative value of the particle size distribution of the volume reference, measured by laser diffraction / scattering particle size distribution determination, is 50%, i.e., the median particle size (D50).

[0022] A. Solid electrolyte materials

[0023] In this invention, a solid electrolyte material is provided, wherein the solid electrolyte material comprises a Li salt having a fluoride anion, an inorganic filler, and a polymer, wherein the inorganic filler is surface-modified with fluorinated alkyl groups.

[0024] In solid electrolyte materials containing Li salts with fluorine-containing anions (hereinafter sometimes referred to as F-containing anions), inorganic fillers, and polymers, both lithium ions (cations) and F-containing anions migrate, thus reducing the lithium ion transference number.

[0025] Therefore, in the solid electrolyte material of the present invention, the lithium-ion transference number was successfully improved by surface modification of the inorganic filler with fluorinated alkyl groups. This is believed to be because the surface modification with fluorinated alkyl groups generates an FF interaction between the inorganic filler and the F-containing anion, resulting in a decrease in the relative mobility of the F-containing anion relative to lithium ions. Furthermore, it is believed that the pre-introduction of fluorinated alkyl groups onto the surface of the inorganic filler through surface modification also improves the dispersibility of the inorganic filler and the fluorinated alkyl groups in the solid electrolyte material.

[0026] As a Li salt containing an F anion, there is no particular limitation, and it may include at least one of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium fluorosulfonyl(trifluoromethanesulfonyl)imide (LiFTFSI), LiPF6, LiBF4 and LiCF3SO3 (LiTfO).

[0027] In solid electrolyte materials, the proportion of Li salt containing F anions is not particularly limited. For example, relative to the total amount of solid electrolyte materials, it can be 40% or more by mass, 60% or more by mass, and 96% or less by mass, or 85% or less by mass.

[0028] As an inorganic filler, examples include SiO2, Al2O3, TiO2, ZrO2 and MgO, and may include at least one selected from the group consisting of SiO2, TiO2, ZrO2 and MgO.

[0029] The average particle size of inorganic fillers is not particularly limited; for example, it can be 0.1 μm to 0.2 μm.

[0030] Inorganic fillers are surface-modified with fluorinated alkyl groups. By introducing fluorinated alkyl groups onto the surface of the inorganic filler, FF interactions can be achieved between the inorganic filler and F-containing anions, and the dispersion state of the inorganic filler and fluorinated alkyl groups in solid electrolyte materials can be improved.

[0031] In this invention, the fluorinated alkyl group can be any structure in which some or all of the hydrogen atoms in the alkyl carbon chain are replaced by fluorine atoms, or it can be a structure containing groups, elements, etc., other than the fluorinated alkyl group. The number of carbon atoms in the alkyl carbon chain of the fluorinated alkyl group is not particularly limited; for example, it can be 1 to 12, or 3 to 10. Furthermore, the fluorinated alkyl group can have a branched structure.

[0032] As specific fluorinated alkyl groups, structures comprising at least one of 1H,1H,2H,2H-tridecylfluorooctyl and 1H,1H,2H,2H-heptadecylfluorodecyl can be listed, for example.

[0033] There are no particular limitations on the methods for surface modification of inorganic fillers using fluorinated alkyl groups; for example, surface treatment of inorganic fillers using silane coupling agents can be cited. Surface treatment methods using silane coupling agents can employ well-known techniques.

[0034] The trimethoxy(1H,1H,2H,2H-tridecylfluorooctyl)silane shown in structural formula (1) below can be used as a silane coupling agent to introduce a modifying group containing 1H,1H,2H,2H-tridecylfluorooctyl into the surface of inorganic fillers. Similarly, the trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane shown in structural formula (2) below can introduce a modifying group containing 1H,1H,2H,2H-heptadecylfluorodecyl into the surface of inorganic fillers.

[0035]

[0036] In solid electrolyte materials, the content of inorganic fillers that have been surface-modified with fluorinated alkyl groups can be, for example, more than 1% by mass and less than 10% by mass relative to the total amount of solid electrolyte materials.

[0037] Examples of polymers include polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethacrylonitrile, polyvinyl butyral, polyvinyl formal, polyvinylpyrrolidone, styrene-butadiene rubber, nitrile rubber, and combinations thereof.

[0038] The number-average molecular weight Mn of the polymer is not particularly limited and can be 3,000 to 200,000 or 5,000 to 100,000.

[0039] The polymer content in solid electrolyte materials can be between 3% and 30% by mass, or less than 10% by mass, relative to the total amount of the solid electrolyte material. Below 3% by mass, the required strength of the solid electrolyte material may not be achieved. Furthermore, above 30% by mass, the ion transport number may sometimes decrease.

[0040] By applying polymers to solid electrolyte materials, the lithium-ion transference number can be increased, thus endowing the solid electrolyte materials with the function of a membrane.

[0041] The solid electrolyte material of the present invention may contain components other than those described above. Examples of other components include succinate (hereinafter, sometimes referred to as SN). Succinate is a plastic crystal existing in the form of NCCH2CH2CN, and as a solid solvent, it can improve the ionic conductivity of the solid electrolyte material.

[0042] For example, from the perspective of improving the ionic conductivity of solid electrolyte materials, the content of succinate in solid electrolyte materials is 1 to 10 moles, or even 2 to 4 moles, relative to 1 mole of Li salt containing F anions.

[0043] B. Battery

[0044] The battery of the present invention has a positive electrode layer, a negative electrode layer and an electrolyte layer, and typically has a positive electrode containing the positive electrode layer and a negative electrode containing the negative electrode layer.

[0045] Figure 1 This is a schematic cross-sectional view illustrating the battery of the present invention. Figure 1 The battery 10 shown has a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive current collector 4 for collecting current in the positive electrode layer 1, and a negative current collector 5 for collecting current in the negative electrode layer 2. In this invention, the electrolyte layer 3 contains the solid electrolyte material described in "A. Solid Electrolyte Material" above.

[0046] By using the solid electrolyte material of the present invention, a battery with excellent lithium-ion conductivity can be obtained.

[0047] The battery of the present invention can be a solid-state battery in which the electrolyte layer contains a solid electrolyte. The solid-state battery can be a semi-solid-state battery or an all-solid-state battery. In the present invention, a semi-solid-state battery is a battery in which the electrolyte layer contains both a solid electrolyte and liquid components (e.g., solvent and electrolyte solution). In the present invention, an all-solid-state battery is a battery in which the electrolyte layer contains only a solid electrolyte as the electrolyte.

[0048] [positive electrode]

[0049] The positive electrode has a positive electrode layer and, if necessary, a positive electrode current collector.

[0050] The positive electrode layer is a layer containing at least a positive electrode active material. In addition, the positive electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder, as needed.

[0051] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other layered active substances in rock salt, LiMn2O4, Li4Ti5O 12 and Li(Ni 0.5 Mn 1.5 Spinel-type active substances such as O4, and olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4 and LiCoPO4.

[0052] A coating containing a Li-ion-conducting compound can be formed on the surface of the positive electrode active material. This is because it can suppress the reaction between the positive electrode active material and the solid electrolyte (especially a sulfide solid electrolyte). Examples of Li-ion-conducting compounds include B₂O₃, Li₂B₄O₇, LiBPO₄, Li₃PO₄, LiPO₃, and LiNbO₃. The coating thickness is, for example, 1 nm or more and 30 nm or less. The coating percentage of the Li-ion-conducting compound covering the positive electrode active material is, for example, 70% or more, 90% or more, or 100%. There are no particular limitations on the coating method of the Li-ion-conducting compound; conventionally known methods can be appropriately used.

[0053] The positive electrode active material is usually in the form of particles. The particles of the positive electrode active material can be primary particles or secondary particles formed by the aggregation of primary particles.

[0054] The average particle size (D50) of the positive electrode active material is not particularly limited, for example, it can be 0.01 μm or more and 50 μm or less, or it can be 0.5 μm or more and 30 μm or less.

[0055] The proportion of positive electrode active material in the positive electrode layer can be, for example, 20% by mass or more, 30% by mass or more, or 40% by mass or more. If the proportion of positive electrode active material is too low, sufficient energy density may not be obtained. On the other hand, the proportion of positive electrode active material in the positive electrode layer can be, for example, 80% by mass or less, 70% by mass or less, or 60% by mass or less. If the proportion of positive electrode active material is too high, the ionic conductivity and electronic conductivity of the positive electrode layer may decrease.

[0056] The positive electrode layer may contain a solid electrolyte. Adding a solid electrolyte improves the ionic conductivity of the positive electrode layer. The solid electrolyte can be an inorganic solid electrolyte such as a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, or a complex hydride solid electrolyte, or an organic solid electrolyte such as a gel electrolyte. The solid electrolyte can be any of the solid electrolyte materials described in "A. Solid Electrolyte Materials" above.

[0057] Sulfide solid electrolytes are electrolytes containing sulfur (S). They typically contain at least lithium (Li) and sulfur (S). Sulfide solid electrolytes may further contain metal (Me) (Me is at least one of P, As, Sb, Si, Ge, Sn, Bi, Al, Zn, Ga, and In). Additionally, sulfide solid electrolytes may contain halogens such as sulfur (F), chlorine (Cl), br, and iron (I).

[0058] Sulfide solid electrolytes can be glass-based (amorphous), glass-ceramic, or crystalline. They can also possess crystalline phases. Examples of such crystalline phases include the Thio-Lisicon type, the sulfide-germanium sulfide type, and the LGPS type.

[0059] The composition of sulfide solid electrolytes is not particularly limited; examples include xLi₂S·(1-x)P₂S₅ (0.5≤x<1) and yLiI·zLiBr·(100-yz)(xLi₂S·(1-x)P₂S₅) (0.5≤x<1, 0≤y≤30, 0≤z≤30). In these compositions, x can satisfy 0.7≤x≤0.8. Other examples of sulfide solid electrolyte compositions include Li 7-x PS 6-x X x X is at least one of F, Cl, Br, and I, and x satisfies 0 ≤ x < 2. Additionally, other examples of sulfide solid electrolyte compositions include Li. 4-x Me 1-x P x S4 (0 < x < 1). Me is defined the same as above. Examples of sulfide solid electrolytes include LiI-LiBr-Li2S-P2S5, LiI-Li2S-P2S5, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5.

[0060] Examples of oxide solid electrolytes include substances with a garnet-type crystal structure containing Li, La, A (where A is at least one of Zr, Nb, Ta, and Al), and O. Examples of oxide solid electrolytes include Li₂O-B₂O₃-P₂O₅, Li₂O-SiO₂, Li₂O-B₂O₃, and Li₂O-B₂O₃. 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4 and Li 3+x PO 4-x N x (1≤x≤3) etc.

[0061] As a halide solid electrolyte, it can be, for example, a solid electrolyte containing Li, M and X (M represents at least one of Ti, Al and Y, and X represents F, Cl or Br).

[0062] From an operational point of view, solid electrolytes can be in the form of particles.

[0063] In addition, the average particle size (D50) of the solid electrolyte is not particularly limited and can be from 1 nm to 100 μm.

[0064] The proportion of solid electrolyte in the positive electrode layer can be, for example, 10% by mass or more, 20% by mass or more, or 30% by mass or more. If the proportion of solid electrolyte is too low, the ion conduction pathways in the positive electrode layer may be insufficient. On the other hand, the proportion of solid electrolyte in the positive electrode layer can be, for example, 60% by mass or less, or 50% by mass or less. If the proportion of solid electrolyte is too high, the proportion of positive electrode active material will be relatively low, and the energy density may be lower.

[0065] The positive electrode layer can contain conductive materials. Adding conductive materials improves the electronic conductivity of the positive electrode layer. Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), fibrous carbon materials such as vapor-phase carbon fiber (VGCF), carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0066] The proportion of conductive material in the positive electrode layer can be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more. If the proportion of conductive material is too low, the electron conduction pathways in the positive electrode layer may be insufficient. On the other hand, the proportion of conductive material in the positive electrode layer can be, for example, 5% by mass or less, or 3% by mass or less. If the proportion of conductive material is too high, the proportion of positive electrode active material becomes relatively low, and the energy density may become lower.

[0067] The positive electrode layer may contain an adhesive. Examples of adhesives include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-isoprene-styrene block copolymer (SIS), and ethylene-propylene-diene copolymer (EPDM).

[0068] The proportion of binder in the positive electrode layer can be, for example, 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more. If the proportion of binder is too low, it may not be able to sufficiently reduce the increase in resistance caused by charging and discharging. On the other hand, the proportion of binder in the positive electrode layer can be, for example, 5% by mass or less, or 3% by mass or less. If the proportion of binder is too high, the proportion of positive electrode active material will be relatively low, and the energy density may be lower.

[0069] The thickness of the positive electrode layer can be, for example, 0.1 μm or more and 1000 μm or less, 1 μm or more and 500 μm or less, or 30 μm or more and 100 μm or less.

[0070] The manufacturing method of the positive electrode layer is not particularly limited. For example, the following method can be used: mixing the above-mentioned positive electrode active material, the above-mentioned solid electrolyte, and a solvent to obtain a positive electrode slurry; coating the above-mentioned positive electrode slurry onto a positive electrode current collector; and drying it to form a positive electrode layer. During the formation of the positive electrode layer, a pressing process can be performed to press the positive electrode layer in the thickness direction. Examples of pressing processes include roll forming and flat plate forming.

[0071] As a solvent, examples include tetrahydronaphthalene, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, dodecane, isodecane, and toluene, and may contain two or more of these components.

[0072] Materials used as positive current collectors include, for example, SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive current collector can be foil-like or plate-like. The top view shape of the positive current collector is not particularly limited; for example, circular, elliptical, rectangular, and arbitrary polygonal shapes are possible. The positive current collector can be composed of a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0073] [negative electrode]

[0074] The negative electrode has a negative electrode layer and, if necessary, a negative electrode current collector.

[0075] The negative electrode layer is a layer containing at least a negative electrode active material. Additionally, the negative electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder, depending on requirements.

[0076] The negative electrode layer contains at least one of elemental Li and Li alloy as the negative electrode active material. Examples of metallic elements other than lithium contained in the Li alloy include Mg, Ag, In, Sn, Si, Ga, Au, and Pt.

[0077] Regarding the solid electrolyte, conductive material, and binder used in the negative electrode layer, the same substances as those described in the positive electrode layer can be listed.

[0078] Materials used as negative current collectors include, for example, SUS, aluminum, copper, nickel, iron, titanium, and carbon. Furthermore, the thickness of the negative current collector varies depending on its shape, ranging from, for example, 1 μm to 50 μm. The shape of the negative current collector can be foil-like or plate-like. The top-view shape of the negative current collector is not particularly limited; examples include circular, elliptical, rectangular, and arbitrary polygonal shapes. The negative current collector can be composed of a buffer layer, an elastic layer, or a PTC thermistor layer disposed on its surface.

[0079] [Electrolyte layer]

[0080] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least a solid electrolyte. The solid electrolyte is the solid electrolyte material described in "A. Solid Electrolyte Material" above.

[0081] The proportion of solid electrolyte in the electrolyte layer is not particularly limited. For example, it can be 50% or more by mass, or it can be in the range of 60% or more and 100% by mass, or it can be in the range of 70% or more and 100% by mass, or it can be 100% by mass.

[0082] Solid electrolytes can be used alone or in combination with two or more types. Furthermore, when using two or more solid electrolytes, they can be mixed, or they can be layered into two or more separate layers to create a multilayer structure.

[0083] The electrolyte layer may further contain a solid electrolyte other than "A. solid electrolyte material" as a solid electrolyte. Examples of solid electrolytes other than "A. solid electrolyte material" include solid electrolytes that can be contained in the above-mentioned positive electrode layer.

[0084] The electrolyte layer may contain an electrolyte solution. The presence of an electrolyte solution improves ionic conductivity. To prevent a decrease in mechanical strength at high temperatures, the proportion of electrolyte solution in the electrolyte layer relative to the total electrolyte content can be, for example, less than 10% by mass, less than 5% by mass, less than 1% by mass, or less than 0.5% by mass.

[0085] As electrolytes, aqueous electrolytes and non-aqueous electrolytes can be used. One type can be used alone, or two or more can be used in combination. Conventionally known electrolytes can be used as both aqueous and non-aqueous electrolytes.

[0086] In the electrolyte layer, a membrane that is impregnated with electrolyte and prevents the positive electrode layer from contacting the negative electrode layer can be used.

[0087] The material used for the membrane is not particularly limited as long as it is a porous membrane. Examples include resins such as polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol, cellulose, and polyamide, among which polyethylene and polypropylene are possible. Furthermore, the membrane can be a single-layer or multi-layer structure. Examples of multi-layer membranes include two-layer PE / PP membranes, or three-layer PP / PE / PP or PE / PP / PE membranes.

[0088] The diaphragm can be made of resin nonwoven fabric, glass fiber nonwoven fabric, or other nonwoven fabrics.

[0089] The thickness of the electrolyte layer can be, for example, 0.1 μm or more and 1000 μm or less, or 0.1 μm or more and 500 μm or less.

[0090] [other]

[0091] The battery of the present invention may further include a constraint clamp that applies constraint pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer along the thickness direction. When the electrolyte layer is a solid electrolyte layer, good ion conduction paths and electron conduction paths can be formed. The constraint pressure is, for example, 0.1 MPa or more, and can be 1 MPa or more, or 5 MPa or more. On the other hand, the constraint pressure is, for example, 100 MPa or less, and can be 50 MPa or less, or 20 MPa or less.

[0092] The type of battery used in this invention is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery of this invention can be a primary battery or a secondary battery, with a particular emphasis on secondary batteries. This is because the ability to be repeatedly charged and discharged makes it useful, for example, as a vehicle battery.

[0093] There are no particular limitations on the shape of the battery; for example, it can be coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat, or stacked.

[0094] Batteries can be used in various applications, including as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, they can be used as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, batteries can be used as power sources for mobile bodies other than vehicles (such as trains, ships, and airplanes), and also as power sources for electrical products such as information processing devices.

[0095] [Example 1]

[0096] <Preparation of surface-modified SiO2(1)>

[0097] In an Ar glove box, 2 g of SiO2 (Sigma-Aldrich, average particle size 0.1 μm to 0.2 μm), 20 g of ultra-dehydrated ethanol (Fujifilm and Kohden Chemical Co., Ltd.), and 0.15 g of trimethoxy(1H,1H,2H,2H-tridecylfluoron-octyl)silane (structural formula (1) above, manufactured by Tokyo Chemical Industry Co., Ltd.) were weighed and stirred at 50 °C for 16 hours in a sealed reaction vessel to carry out a silane coupling reaction. The solution after stirring was filtered and repeatedly washed and filtered five times with 30 mL of ethanol. The obtained solid was vacuum dried at 100 °C for 12 hours. Thus, surface-modified SiO2 (1) with the SiO2 surface modified by a modifying group containing fluorinated alkyl groups was obtained.

[0098] <Preparation of Solid Electrolyte Materials>

[0099] In an Ar atmosphere glove box, succinate (manufactured by Sigma-Aldrich) and LITFSI (manufactured by Sigma-Aldrich) were weighed at a molar ratio of SN:LITFSI = 4:1, and stirred at 70°C for 24 hours. Polyethylene oxide (manufactured by Sigma-Aldrich, number average molecular weight Mn = 6000) was added to the resulting solution to make it 10% by mass relative to the total amount of the obtained solid electrolyte material, and surface-modified SiO2 (1) was added to make it 5% by mass relative to the total amount of the obtained solid electrolyte material. The mixture was then stirred at 70°C for 24 hours to obtain the solid electrolyte material.

[0100] [Example 2]

[0101] <Preparation of surface-modified SiO2(2)>

[0102] In Example 1, 0.18 g of trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane (the above structural formula (2), manufactured by Tokyo Chemical Industry) was used instead of 0.15 g of trimethoxy(1H,1H,2H,2H-tetrafluoron-octyl)silane, and the same procedure was followed to obtain surface-modified SiO2 (2) with the SiO2 surface modified by a modifying group containing fluorinated alkyl groups.

[0103] <Preparation of Solid Electrolyte Materials>

[0104] In Example 1, surface-modified SiO2 (2) was used instead of surface-modified SiO2 (1), and otherwise the same operation was performed to obtain a solid electrolyte material.

[0105] [Comparative Example 1]

[0106] <Preparation of Solid Electrolyte Materials>

[0107] In Example 1, without using surface-modified SiO2 (1), the same procedure was followed to obtain a solid electrolyte material.

[0108] [Comparative Example 2]

[0109] <Preparation of Solid Electrolyte Materials>

[0110] In Example 1, unmodified SiO2 (Sigma-Aldrich, average particle size 0.1 μm to 0.2 μm) was used instead of surface-modified SiO2 (1), and the same procedure was followed to obtain a solid electrolyte material.

[0111] [Comparative Example 3]

[0112] <Preparation of surface-modified SiO2(3)>

[0113] In Example 1, 0.06 g of hexyltrimethoxysilane (structural formula (3) below, manufactured by Tokyo Chemical) was used instead of 0.15 g of trimethoxy(1H,1H,2H,2H-tridecylfluoron-octyl)silane. Otherwise, the same procedure was followed to obtain surface-modified SiO2 (3) with modification groups containing unfluorinated alkyl groups on the SiO2 surface.

[0114]

[0115] <Preparation of Solid Electrolyte Materials>

[0116] In Example 1, surface-modified SiO2 (3) was used instead of surface-modified SiO2 (1), and otherwise the same operation was performed to obtain a solid electrolyte material.

[0117] [Determination of lithium-ion transference number]

[0118] For the solid electrolyte materials of Examples 1-2 and Comparative Examples 1-3 obtained above, the lithium-ion transference number was measured as follows.

[0119] First, a solid electrolyte material is heated to 60°C and impregnated in a polypropylene separator. Next, a button cell is fabricated using the separator impregnated with the solid electrolyte material, with a Li metal / impregnated separator / Li metal configuration. The fabricated button cell is then placed in a 50°C constant-temperature bath for 12 hours.

[0120] After settling, the AC impedance was measured at 50°C using a potentiostat / galvanostat (VMP3, Biologic) within a frequency range of 1 Hz to 1 MHz. The measured resistance was then taken as the pre-polarization impedance R0 (Ω).

[0121] Next, a DC polarization measurement was performed at 10mV for 3600 seconds. The initial current value at this time was taken as the pre-polarization current value I0 (A), and the current value in the steady state (after 3600 seconds) was taken as the post-polarization current value I. S (A)

[0122] Then, AC impedance measurements were performed in the frequency range of 1Hz-1MHz. The measured resistance was then used as the polarized impedance R. S (Ω).

[0123] The lithium-ion transport number t is obtained using the obtained value through the following formula. Li+ In the following formula, V is the applied voltage (V). The results are shown in Table 1.

[0124]

[0125]

[0126] As shown in Table 1, the solid electrolyte materials of Examples 1-2, which used inorganic fillers (SiO2) with fluorinated alkyl groups, all showed higher lithium-ion transference numbers compared to any one of Comparative Example 1 (without inorganic fillers (SiO2), Comparative Example 2 (with unmodified inorganic fillers (SiO2), and Comparative Example 3 (with inorganic fillers (SiO2) with unfluorinated alkyl groups).

Claims

1. A solid electrolyte material, wherein, The solid electrolyte material comprises a Li salt containing fluoride anions, inorganic fillers, and a polymer. The inorganic filler was surface-modified using fluorinated alkyl groups.

2. The solid electrolyte material according to claim 1, wherein, The solid electrolyte material also contains succinic anionyl nitrile.

3. The solid electrolyte material according to claim 1, wherein, The inorganic filler comprises at least one selected from the group consisting of SiO2, TiO2, ZrO2, and MgO. The fluorinated alkyl group comprises at least one of 1H,1H,2H,2H-tridecylfluorooctyl and 1H,1H,2H,2H-heptadecylfluorodecyl.

4. The solid electrolyte material according to claim 1, wherein, The Li salt comprises at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium fluorosulfonyl(trifluoromethanesulfonyl)imide (LiFTFSI), LiPF6, LiBF4, and LiCF3SO3 (LiTfO).

5. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, wherein, The electrolyte layer contains a solid electrolyte. The solid electrolyte is the solid electrolyte material according to any one of claims 1 to 4.

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