Solid electrolyte material and battery using the same

Abstract

The solid electrolyte material according to the present disclosure comprises Li, La, O, and I. The battery 1000 according to the present disclosure is provided with a positive electrode 201, a negative electrode 203, and an electrolyte layer 202. The electrolyte layer 202 is arranged between the positive electrode 201 and the negative electrode 203. At least one member selected from the group consisting of the positive electrode 201, the negative electrode 203, and the electrolyte layer 202 contains the solid electrolyte material according to the present disclosure.

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolyte material and a battery using the same. [Background technology]

[0002] Patent Document 1 discloses a lithium ion conductive solid electrolyte material composed of Li, La, O, and X, and an all-solid-state battery using the same, where X is at least one element selected from the group consisting of Cl, Br, and I. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 137043 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a solid electrolyte material suitable for improving lithium ion conductivity. [Means for solving the problem]

[0005] The solid electrolyte material of the present disclosure is composed of Li, La, O, and I. [Effects of the Invention]

[0006] The present disclosure provides a solid electrolyte material suitable for improving lithium ion conductivity. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment. [Figure 2] FIG. 2 shows a cross-sectional view of an electrode material 1100 according to a second embodiment. [Figure 3]FIG. 3 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of a solid electrolyte material. [Figure 4] FIG. 4 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the solid electrolyte material according to Example 1. [Figure 5] FIG. 5 is a graph showing the initial charge-discharge characteristics of the battery according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0009] (First embodiment) The solid electrolyte material according to the first embodiment is made of Li, La, O, and I.

[0010] The solid electrolyte material according to the first embodiment is a solid electrolyte material suitable for improving lithium ion conductivity. The solid electrolyte material according to the first embodiment can have, for example, a practical lithium ion conductivity, for example, a high lithium ion conductivity. Here, the high lithium ion conductivity is, for example, 5×10 at around room temperature (for example, 25° C.). -5 That is, the solid electrolyte material according to the first embodiment has a specific resistance of, for example, 5×10 -5 It may have an ionic conductivity of 5 S / cm or more.

[0011] The solid electrolyte material according to the first embodiment can be used to obtain a battery with excellent charge / discharge characteristics. An example of such a battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0012] The solid electrolyte material according to the first embodiment substantially does not contain sulfur. That the solid electrolyte material according to the first embodiment substantially does not contain sulfur means that the solid electrolyte material does not contain sulfur as a constituent element, except for sulfur inevitably mixed as an impurity. In this case, the sulfur mixed as an impurity in the solid electrolyte material is, for example, 1 mol% or less. The solid electrolyte material according to the first embodiment does not contain sulfur. The solid electrolyte material that does not contain sulfur is excellent in safety because hydrogen sulfide does not generate even when exposed to the atmosphere. The sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

[0013] The solid electrolyte material according to the first embodiment may contain unavoidably mixed elements. Examples of such elements are hydrogen or nitrogen. Such elements may exist in the raw material powder of the solid electrolyte material or in the atmosphere for manufacturing or storing the solid electrolyte material. In the solid electrolyte material according to the first embodiment, the unavoidably mixed elements as described above are, for example, 1 mol% or less.

[0014] In the solid electrolyte material according to the first embodiment, the molar ratio of O (that is, oxygen) to I (that is, iodine) may be less than 1. Such a solid electrolyte material has high lithium ion conductivity.

[0015] The solid electrolyte material according to the first embodiment may be a material represented by the following composition formula (1). Li a La b OI c ···(1) Here, 0 < a, 0 < b, (a + b) < 4.0, and 0 < c < 4.0 are satisfied.

[0016] The solid electrolyte material represented by the composition formula (1) has high ion conductivity.

[0017] In order to increase the ion conductivity of the solid electrolyte material, in the composition formula (1), 0.5 ≤ a ≤ 2.3 and 0.7 ≤ b ≤ 1.5 may be satisfied.

[0018] In order to increase the ionic conductivity of the solid electrolyte material, the formula (1) may satisfy the conditions 0.5≦a≦2.0 and 1.0≦b≦1.5.

[0019] In order to further increase the ionic conductivity of the solid electrolyte material, the formula (1) may satisfy the conditions 0.8≦a≦2.0 and 1.0≦b≦1.4.

[0020] The upper and lower limits of the range of a in composition formula (1) may be defined by any combination selected from the following numerical values: 0.50, 0.60, 0.80, 1.00, 1.20, 1.40, and 2.00.

[0021] The upper and lower limits of the range of b in composition formula (1) may be defined by any combination selected from the following numerical values: 1.00, 1.20, 1.27, 1.33, 1.40, 1.47, and 1.50.

[0022] In order to increase the ionic conductivity of the solid electrolyte material, the formula (1) may satisfy the condition 1.0≦c≦3.0.

[0023] In order to increase the ionic conductivity of the solid electrolyte material, the formula (1) may satisfy c=3.0. That is, the formula (1) may satisfy c=3.0. a La b OI 3.0 may be.

[0024] The solid electrolyte material according to the first embodiment may be crystalline or amorphous.

[0025] The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of the shape include a needle shape, a sphere shape, or an oval sphere shape. The solid electrolyte material according to the first embodiment may be in the form of particles. The solid electrolyte material according to the first embodiment may have the shape of a pellet or a plate.

[0026] When the solid electrolyte material according to the first embodiment has a particulate (e.g., spherical) shape, the solid electrolyte material may have a median diameter of 0.1 μm or more and 100 μm or less, or may have a median diameter of 0.5 μm or more and 10 μm or less, which allows the solid electrolyte material according to the first embodiment and other materials to be dispersed well.

[0027] The median particle size refers to the particle size (d50) corresponding to 50% of the cumulative volume in the volume-based particle size distribution. The volume-based particle size distribution can be measured using a laser diffraction measurement device or an image analysis device.

[0028] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment can be produced, for example, by the following method.

[0029] A raw material powder is prepared to have a desired composition.

[0030] As an example, the composition of the desired solid electrolyte material is Li 2.0 La 1.0 In the case of OI3, Li2O raw material powder and LaI3 raw material powder are mixed in a molar ratio of 1.0:1.0. The raw material powders may be mixed in a molar ratio adjusted in advance to offset composition changes that may occur during the synthesis process.

[0031] For example, raw material powders are reacted with each other mechanochemically (ie, using the method of mechanochemical milling) in a mixing device such as a planetary ball mill to obtain a reactant.

[0032] By this method, the solid electrolyte material according to the first embodiment is obtained.

[0033] The composition of the solid electrolyte material can be determined by, for example, ICP atomic emission spectroscopy, ion chromatography, inert gas fusion-infrared absorption spectroscopy, or EPMA (Electron Probe Micro Analyzer). For example, the composition of Li and La can be determined by ICP atomic emission spectroscopy, the composition of I can be determined by ion chromatography, and O can be measured by inert gas fusion-infrared absorption spectroscopy.

[0034] (Second embodiment) A second embodiment of the present disclosure will be described below. The matters described in the first embodiment may be omitted.

[0035] In the second embodiment, a battery using the solid electrolyte material according to the first embodiment will be described.

[0036] The battery according to the second embodiment includes a positive electrode, a negative electrode, and an electrolyte layer. The electrolyte layer is disposed between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode, the electrolyte layer, and the negative electrode contains the solid electrolyte material according to the first embodiment.

[0037] The battery according to the second embodiment has excellent charge / discharge characteristics because it contains the solid electrolyte material according to the first embodiment. The battery may be an all-solid-state battery.

[0038] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0039] The battery 1000 according to the second embodiment includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0040] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0041] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0042] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0043] The solid electrolyte particle 100 includes the solid electrolyte material according to the first embodiment. The solid electrolyte particle 100 may be a particle containing the solid electrolyte material according to the first embodiment as a main component. Particles containing the solid electrolyte material according to the first embodiment as a main component refer to particles in which the component contained in the largest amount in terms of molar ratio is the solid electrolyte material according to the first embodiment. The solid electrolyte particle 100 may be a particle made of the solid electrolyte material according to the first embodiment.

[0044] The solid electrolyte particles 100 may have a median diameter of 0.1 μm or more and 100 μm or less, or may have a median diameter of 0.5 μm or more and 10 μm or less, in which case the solid electrolyte particles 100 have higher ionic conductivity.

[0045] The positive electrode 201 contains a material capable of absorbing and releasing metal ions such as lithium ions, and includes, for example, a positive electrode active material (for example, positive electrode active material particles 204).

[0046] Examples of the positive electrode active material include a lithium-containing transition metal oxide, a transition metal fluoride, a polyanionic material, a fluorinated polyanionic material, a transition metal sulfide, a transition metal oxyfluoride, a transition metal oxysulfide, or a transition metal oxynitride. An example of a lithium-containing transition metal oxide is LiNi 1-d-f Co d Al f O2 (where 0 <d、0<f、かつ0<(d+f)<1)またはLiCoO2である。

[0047] From the viewpoint of cost and safety of the battery 1000, lithium phosphate may be used as the positive electrode active material.

[0048] The positive electrode 201 may contain a transition metal oxyfluoride as a positive electrode active material together with the solid electrolyte material according to the first embodiment. The solid electrolyte material according to the first embodiment is difficult to form a resistance layer even when fluorinated by the transition metal oxyfluoride. As a result, the battery 1000 has high charge and discharge efficiency.

[0049] The transition metal oxyfluoride contains oxygen and fluorine. As an example, the transition metal oxyfluoride is Li p Me’ q O m F n and may be a compound represented by. Here, Me’ is at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and the mathematical formulas: 0.5 ≦ p ≦ 1.5, 0.5 ≦ q ≦ 1.0, 1 ≦ m < 2, and 0 < n ≦ 1 are satisfied. An example of such a transition metal oxyfluoride is Li 1.05 (Ni 0.35 Co 0.35 Mn 0.3 ) 0.95 O 1.9 F 0.1 .

[0050] The positive electrode active material particles 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median diameter of 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 100 can be well dispersed in the positive electrode 201. Thereby, the charge and discharge characteristics of the battery are improved. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the lithium diffusion rate in the positive electrode active material particles 204 is improved. Thereby, the battery can operate at high power.

[0051] The positive electrode active material particles 204 may have a median diameter larger than that of the solid electrolyte particles 100. Thereby, the positive electrode active material particles 204 and the solid electrolyte particles 100 can be well dispersed.

[0052] In order to increase the energy density and output of the battery, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the sum of the volume of the positive electrode active material particles 204 and the volume of the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0053] FIG. 2 shows a cross-sectional view of an electrode material 1100 according to a second embodiment. The electrode material 1100 is included in, for example, a positive electrode 201. To prevent the solid electrolyte particles 100 from reacting with the positive electrode active material (i.e., the electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This can suppress an increase in the reaction overvoltage of the battery. Examples of coating materials included in the coating layer 216 include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. The coating material may be lithium niobate, which has excellent stability even at high potentials.

[0054] The cathode 201 may comprise a first cathode layer containing a first cathode active material and a second cathode layer containing a second cathode active material. Here, the second cathode layer is disposed between the first cathode layer and the electrolyte layer 202. The first cathode layer and the second cathode layer may contain the solid electrolyte material according to the first embodiment, and a coating layer may be formed on the surface of the second cathode active material. This configuration prevents the solid electrolyte material according to the first embodiment contained in the electrolyte layer 202 from being oxidized by the second cathode active material. As a result, the battery has a high charge capacity. Examples of coating materials contained in the coating layer 216 include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes. The first cathode active material may be the same material as the second cathode active material or may be a different material from the second cathode active material.

[0055] To increase the energy density and power output of the battery, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0056] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may be a solid electrolyte layer. The electrolyte layer 202 may contain the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may be made of only the solid electrolyte material according to the first embodiment.

[0057] Hereinafter, the solid electrolyte material according to the first embodiment will be referred to as a first solid electrolyte material, and a solid electrolyte material different from the solid electrolyte material according to the first embodiment will be referred to as a second solid electrolyte material.

[0058] The electrolyte layer 202 may contain the second solid electrolyte material, or may consist solely of the second solid electrolyte material.

[0059] The electrolyte layer 202 may contain not only the first solid electrolyte material but also the second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed.

[0060] The electrolyte layer 202 may have a thickness of 1 μm or more and 100 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to short-circuit. When the electrolyte layer 202 has a thickness of 100 μm or less, the battery can operate at high power.

[0061] Another electrolyte layer (i.e., a second electrolyte layer) may be further provided between the electrolyte layer 202 and the negative electrode 203. For example, when the electrolyte layer 202 includes a first solid electrolyte material, the second electrolyte layer may be composed of another solid electrolyte material that is electrochemically more stable than the first solid electrolyte material. Specifically, the reduction potential of the solid electrolyte material constituting the second electrolyte layer may be lower than the reduction potential of the first solid electrolyte material. This allows the first solid electrolyte material to be used without being reduced. As a result, the charge / discharge efficiency of the battery can be improved.

[0062] The negative electrode 203 contains a material capable of absorbing and releasing metal ions such as lithium ions, and includes, for example, a negative electrode active material (for example, negative electrode active material particles 205).

[0063] Examples of the negative electrode active material include a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a simple metal or an alloy. An example of the metal material is lithium metal or a lithium alloy. Examples of the carbon material are natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, suitable examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0064] The negative electrode active material may be selected based on the reduction resistance of the solid electrolyte material contained in the negative electrode 203. When the negative electrode 203 contains the solid electrolyte material according to the first embodiment, a material capable of absorbing and releasing lithium ions at 0 V or higher relative to lithium may be used as the negative electrode active material. If the negative electrode active material is such a material, the reduction of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the battery has high charge / discharge efficiency. Examples of such materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12 , LiTi2O4, or TiO2.

[0065] The negative electrode active material particles 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median diameter of 0.1 μm or more, the negative electrode active material particles 205 and the solid electrolyte particles 100 can be well dispersed in the negative electrode 203. This improves the charge / discharge characteristics of the battery. When the negative electrode active material particles 205 have a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material particles 205 improves. This allows the battery to operate at high power.

[0066] The negative electrode active material particles 205 may have a larger median diameter than the solid electrolyte particles 100. This allows the negative electrode active material particles 205 and the solid electrolyte particles 100 to be dispersed well.

[0067] In order to increase the energy density and output of the battery, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the total volume of the negative electrode active material particles 205 and the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0068] The electrode material 1100 shown in FIG. 2 may be included in the negative electrode 202. To prevent the solid electrolyte particles 100 from reacting with the negative electrode active material (i.e., the electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This allows the battery to have high charge / discharge efficiency. Examples of coating materials included in the coating layer 216 include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a halide solid electrolyte.

[0069] When the solid electrolyte particles 100 are made of a first solid electrolyte material, the coating material may be a sulfide solid electrolyte or a polymer solid electrolyte. An example of a sulfide solid electrolyte is Li2S-P2S5. An example of a polymer solid electrolyte is a composite compound of polyethylene oxide and a lithium salt. An example of such a polymer solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0070] To increase the energy density and power output of the battery, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0071] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a second solid electrolyte material for the purpose of enhancing ionic conductivity, chemical stability, and electrochemical stability. Examples of the second solid electrolyte material include a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, or an organic polymer solid electrolyte.

[0072] In this disclosure, a "sulfide solid electrolyte" refers to a solid electrolyte containing sulfur. An "oxide solid electrolyte" refers to a solid electrolyte containing oxygen. An oxide solid electrolyte may contain an anion other than oxygen (excluding sulfur and halogen elements). A "halide solid electrolyte" refers to a solid electrolyte containing a halogen element but not sulfur. A halide solid electrolyte may contain not only a halogen element but also oxygen.

[0073] Examples of sulfide solid electrolytes are Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 is.

[0074] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutes; (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or elemental substitutions thereof; (iv) Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an elemental substitution product thereof, or (v) Li3PO4 or its N-substituted derivatives.

[0075] An example of a halide solid electrolyte material is Li a Me b Y c Z6, where the formula: a+mb+3c=6, and c>0 is satisfied. Me is at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. Z is at least one element selected from the group consisting of F, Cl, Br, and I. The value of m represents the valence of Me.

[0076] "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in groups 1 to 12 of the periodic table (except hydrogen) and all elements in groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0077] To increase the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. As the halide solid electrolyte, for example, Li3YCl6 or Li3YBr6 is used.

[0078] When the electrolyte layer 202 contains the first solid electrolyte material, the negative electrode 203 may contain a sulfide solid electrolyte. This allows the sulfide solid electrolyte, which is electrochemically stable with respect to the negative electrode active material, to suppress contact between the first solid electrolyte material and the negative electrode active material. As a result, the internal resistance of the battery is reduced.

[0079] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds. The polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt, thereby further increasing ionic conductivity.

[0080] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF) , LiN(SOCF)(SOCF), or LiC(SOCF). One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used.

[0081] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0082] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0083] Examples of non-aqueous solvents include cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, and fluorine-containing solvents. Examples of cyclic carbonate ester solvents include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of chain carbonate ester solvents include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. Examples of chain ether solvents include 1,2-dimethoxyethane and 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate. Examples of fluorine-containing solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0084] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt may be, for example, 0.5 mol / liter or more and 2 mol / liter or less.

[0085] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0086] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums, or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums.

[0087] An example of an anion found in ionic liquids is PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - is.

[0088] The ionic liquid may contain a lithium salt.

[0089] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving adhesion between particles.

[0090] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. Copolymers may also be used as binders. Examples of such binders include copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. A mixture of two or more of the above materials may also be used as a binder.

[0091] At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive additive for the purpose of increasing electronic conductivity.

[0092] Examples of the conductive additive include: (i) graphites such as natural or synthetic graphite; (ii) carbon blacks such as acetylene black or ketjen black; (iii) conductive fibers such as carbon or metal fibers; (iv) fluorocarbons, (v) metal powders such as aluminum; (vi) conductive whiskers such as zinc oxide or potassium titanate; (vii) a conductive metal oxide such as titanium oxide, or (viii) a conductive polymer such as polyaniline, polypyrrole, or polythiophene; To reduce costs, the above-mentioned conductive additive (i) or (ii) may be used.

[0093] Examples of the shape of the battery according to the second embodiment include a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, and a laminate type.

[0094] The battery according to the second embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and by using a known method to fabricate a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order. [Example]

[0095] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0096] Example 1 [Preparation of solid electrolyte materials] In an argon atmosphere having a dew point of -60°C or less (hereinafter referred to as "dry argon atmosphere"), raw material powders of Li2O and LaI3 were prepared so as to have a molar ratio of Li2O:LaI3 = 1.0:1.0. The mixture of these raw material powders was milled using a planetary ball mill at 500 rpm for 30 hours. In this way, a powder of the solid electrolyte material according to Example 1 was obtained. The solid electrolyte material according to Example 1 contained Li 2.0 LaOI 3.0 The composition here is a charge composition calculated from the charge amounts. However, it was previously confirmed that the composition of the obtained solid electrolyte material was almost the same as the charge composition depending on the production method used in this example.

[0097] [Evaluation of ionic conductivity] FIG. 3 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of the solid electrolyte material.

[0098] The pressure molding die 300 had an upper punch 301, a frame 302, and a lower punch 303. The frame 302 was made of insulating polycarbonate. The upper punch 301 and the lower punch 303 were both made of electronically conductive stainless steel.

[0099] Using the pressure molding die 300 shown in FIG. 3, the ionic conductivity of the solid electrolyte material of Example 1 was measured by the following method.

[0100] In a dry atmosphere having a dew point of −30° C. or less, the powder of the solid electrolyte material according to Example 1 (i.e., the powder of the solid electrolyte material 101 in FIG. 3 ) was filled into the inside of a pressure molding die 300. Inside the pressure molding die 300, a pressure of 400 MPa was applied to the solid electrolyte material according to Example 1 using an upper punch 301.

[0101] While the pressure was still applied, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Bio-Logic Sciences Instruments, VMP-300) equipped with a frequency response analyzer. The upper punch 301 was connected to a working electrode and a potential measurement terminal. The lower punch 303 was connected to a counter electrode and a reference electrode. The ionic conductivity of the solid electrolyte material according to Example 1 was measured at room temperature by electrochemical impedance measurement.

[0102] FIG. 4 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the solid electrolyte material according to Example 1.

[0103] In Fig. 4, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is smallest was considered to be the resistance value for ionic conduction of the solid electrolyte material. This real value is indicated by the arrow R se See.

[0104] Using the resistance value, the ionic conductivity was calculated based on the following formula (2). σ=(Rse ×S / t) -1 ···(2)

[0105] Here, σ represents ionic conductivity, S represents the contact area of ​​the solid electrolyte material with the punch upper portion 301 (equal to the cross-sectional area of ​​the hollow portion of the frame mold 302 in FIG. 3), and R se represents the resistance value of the solid electrolyte material in the impedance measurement. t represents the thickness of the solid electrolyte material to which pressure is applied (equivalent to the thickness of the layer formed from the powder 101 of the solid electrolyte material in FIG. 3). The ionic conductivity of the solid electrolyte material according to Example 1 measured at room temperature was 1.03×10 -4 S / cm.

[0106] [Battery construction] In a dry argon atmosphere, the solid electrolyte material according to Example 1, Li4Ti5O 12 and carbon fiber (VGCF) were prepared in a mass ratio of 30:65:5. These materials were mixed in a mortar. In this way, a mixture was obtained. VGCF is a registered trademark of Showa Denko K.K.

[0107] In an insulating cylinder having an inner diameter of 9.5 mm, 80 mg of Li6PS5Cl (an argyrodite-type sulfide solid electrolyte), 20 mg of the solid electrolyte material according to Example 1, 15 mg of the above mixture, and 2 mg of VGCF were layered in this order. A pressure of 740 MPa was applied to this layered structure to form a solid electrolyte layer and an electrode.

[0108] Next, a metal In foil, a metal Li foil, and a metal In foil were laminated on the solid electrolyte layer in this order, and a pressure of 40 MPa was applied to this laminate to form a counter electrode.

[0109] Next, current collectors made of stainless steel were attached to the electrodes and counter electrodes, and current collecting leads were attached to the current collectors.

[0110] Finally, the inside of the insulating cylinder was isolated from the outside atmosphere using an insulating ferrule, and the inside of the cylinder was sealed. In this way, a battery serving as a charge / discharge test cell according to Example 1 was obtained.

[0111] [Charge / discharge test] 4 is a graph showing the initial charge / discharge characteristics of the battery according to Example 1. The initial charge / discharge characteristics were measured by the following method.

[0112] The battery according to Example 1 was placed in a thermostatic chamber at 25°C.

[0113] 17.1μA / cm 2 The battery according to Example 1 was charged until a voltage of 0.58 V was reached at a current density of 0.01 C, which corresponds to a 0.01 C rate.

[0114] Next, 17.1 μA / cm 2 The battery according to Example 1 was discharged until a voltage of 1.9 V was reached at a current density of 0.01 C, which corresponds to a 0.01 C rate.

[0115] As a result of the charge-discharge test, the battery according to Example 1 had an initial discharge capacity of 268.49 μAh.

[0116] (Examples 2 to 7, Comparative Examples 1 and 2) In Examples 2 to 7, raw material powders of Li2O, La2O3, and LaI3 were prepared in a molar ratio of (a / 2):((b-1) / 2):1.0. The values ​​of a and b are shown in Table 1.

[0117] In Comparative Example 1, LiI, La2O3, and LaBr3 were prepared as raw material powders so as to have a molar ratio of LiI:La2O3:LaBr3=3:1:1.

[0118] In Comparative Example 2, raw material powders of LiCl, La2O3, and LaBr3 were prepared so as to have a molar ratio of LiCl:La2O3:LaBr3=3:1:1.

[0119] Other than the above, the solid electrolyte materials according to Examples 2 to 7 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1.

[0120] The ionic conductivities of the solid electrolyte materials according to Examples 2 to 7, Comparative Example 1, and Comparative Example 2 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0121] [Table 1]

[0122] (Consideration) As is clear from Table 1, the solid electrolyte materials according to Examples 1 to 7 had a melting point of 5×10 -5 It had high lithium ion conductivity of over S / cm.

[0123] As is clear from a comparison of Examples 1 to 7 with Comparative Examples 1 and 2, when X was I only, the ionic conductivity of the solid electrolyte material was higher than when X contained Br or Cl.

[0124] The battery according to Example 1 was charged and discharged at room temperature.

[0125] The solid electrolyte materials according to Examples 1 to 7 do not contain sulfur and therefore do not generate hydrogen sulfide.

[0126] As described above, the solid electrolyte material according to the present disclosure can improve lithium ion conductivity while suppressing the generation of hydrogen sulfide. The solid electrolyte material according to the present disclosure is suitable for providing a battery that can be charged and discharged well. [Industrial Applicability]

[0127] The solid electrolyte material and the method for producing the same according to the present disclosure are used, for example, in batteries (for example, all-solid-state lithium-ion secondary batteries). [Explanation of symbols]

[0128] 100 solid electrolyte particles 101 Solid electrolyte material powder 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 204 Positive electrode active material particles 205 Negative electrode active material particles 300 pressure forming die 301 Punch top 302 Frame type 303 Punch bottom 1000 batteries 1100 Electrode materials

Claims

1. consisting only of Li, La, O, and I; Represented by the following composition formula (1): Li a Lab OI c ... (1) In the composition formula (1), 0.6≦a≦2.0, 1.0≦b≦1.47, and c=3 are satisfied, having a lithium ion conductivity of 8.94×10 −5 S / cm or more; Solid electrolyte material.

2. In the composition formula (1), 0.8≦a≦2.0 and 1.0≦b≦1.4 are satisfied. The solid electrolyte material according to claim 1 .

3. positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to claim 1 or 2. battery.

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