Solid electrolyte material and battery using the same

Abstract

A solid electrolyte material contains Li, Ti, Zr and F.

Description

Technical Field

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

[0002] Patent Document 1 discloses an all-solid-state battery using a sulfide solid electrolyte. Patent Document 2 discloses LiBF4 as a fluoride solid electrolyte material.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-129312

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2008-277170 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] An object of the present disclosure is to provide a solid electrolyte material having high lithium ion conductivity (also referred to as lithium ion electrical conductivity or lithium ion electrical conductivity).

[0009] Means for solving problems

[0010] The solid electrolyte material disclosed herein contains Li, Ti, Zr, and F.

[0011] Effects of the Invention

[0012] The present disclosure provides a solid electrolyte material having high lithium ion conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A cross-sectional view of a battery 1000 according to a second embodiment is shown.

[0014] Figure 2 A cross-sectional view of a battery 2000 according to a second embodiment is shown.

[0015] Figure 3 A schematic diagram showing a press mold 300 for evaluating the ion conductivity of a solid electrolyte material.

[0016] Figure 4 This is a graph showing a Cole-Cole plot obtained by impedance measurement of the solid electrolyte material of Example 1.

[0017] Figure 5 Graphs showing initial discharge characteristics of the batteries of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0019] (First embodiment)

[0020] The solid electrolyte material of the first embodiment contains Li, Ti, Zr, and F. The solid electrolyte material of the first embodiment has high lithium ion conductivity. Here, the so-called high lithium ion conductivity is, for example, 1×10 -8 S / cm or more. That is, the solid electrolyte material of the first embodiment may have, for example, 1×10 -8 S / cm or higher ion conductivity.

[0021] The solid electrolyte material of 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 can be a primary battery or a secondary battery.

[0022] The solid electrolyte material of the first embodiment preferably contains no sulfur. A solid electrolyte material containing no sulfur does not generate hydrogen sulfide even when exposed to the atmosphere, thus providing excellent safety. The sulfide solid electrolyte disclosed in Patent Document 1 can generate hydrogen sulfide when exposed to the atmosphere.

[0023] The solid electrolyte material of the first embodiment can have high oxidation resistance because it contains F. This is because F has a high redox potential. On the other hand, because F has a high electronegativity, it binds strongly to Li. As a result, the lithium ion conductivity of the solid electrolyte material containing Li and F is generally reduced. For example, LiBF4 disclosed in Patent Document 2 has a carbon ion conductivity of 6.67×10 -9 S / cm. Furthermore, LiBF4 is the solid electrolyte material used in Comparative Example 1 described later. In contrast, the solid electrolyte material of the first embodiment can have a conductivity of, for example, 1×10 -8 High ion conductivity of S / cm or more.

[0024] In order to improve the ion conductivity of the solid electrolyte material, the solid electrolyte material of the first embodiment may contain anions other than F. Examples of such anions are Cl, Br, I, O, S, or Se.

[0025] The solid electrolyte material of the first embodiment may be substantially composed of Li, Ti, Zr, and F. Here, the phrase "the solid electrolyte material of the first embodiment is substantially composed of Li, Ti, Zr, and F" means that the molar ratio (i.e., molar fraction) of the total amount of Li, Ti, Zr, and F to the total amount of all elements constituting the solid electrolyte material of the first embodiment is 90% or more. As an example, the molar ratio may be 95% or more. The solid electrolyte material of the first embodiment may be composed only of Li, Ti, Zr, and F.

[0026] The solid electrolyte material of the first embodiment may also contain unavoidable elements. Examples of such elements are hydrogen, oxygen, or nitrogen. Such elements may be present in the raw material powder of the solid electrolyte material or in the atmosphere used to produce or store the solid electrolyte material.

[0027] In order to further improve the ion conductivity of the solid electrolyte material, in the solid electrolyte material of the first embodiment, the ratio of the amount of substance of Li to the total amount of substance of Ti and Zr may be 2.0 or more and 6.0 or less.

[0028] The solid electrolyte material of the first embodiment can also be represented by the following composition formula (1).

[0029] Li 6-4b (Ti 1-x Zr x ) b F6 formula (1)

[0030] In formula (1), the mathematical formulas: 0<x<1 and 0<b≤1.5 are satisfied. A solid electrolyte material having such a composition has high ion conductivity.

[0031] In order to improve the ion conductivity of the solid electrolyte material, the mathematical formula in formula (1) may also be satisfied: 0.1≤x≤0.8.

[0032] The upper limit and lower limit of the range of x in formula (1) can be defined by any combination of numerical values selected from 0.1, 0.2, 0.4, 0.5, 0.6, 0.67, and 0.8.

[0033] In order to improve the ion conductivity of the solid electrolyte material, the equation (1) may satisfy the mathematical formula: 0.6≤b≤1.0. In order to further improve the ion conductivity of the solid electrolyte material, the equation (1) may satisfy the mathematical formula: 0.8≤b≤0.92.

[0034] The upper limit and lower limit of the range of b in formula (1) can be defined by any combination selected from the group consisting of 0.6, 0.8, 0.85, 0.86, 0.92, and 1.0.

[0035] The solid electrolyte material of the first embodiment may be crystalline or amorphous.

[0036] The shape of the solid electrolyte material of the first embodiment is not limited. Examples of the shape include needle-shaped, spherical, or ellipsoidal. The solid electrolyte material of the first embodiment may also be particles. The solid electrolyte material of the first embodiment may also be formed in a form having a particle or plate shape.

[0037] When the solid electrolyte material of the first embodiment is in the form of particles (e.g., spheres), the solid electrolyte material may have a median particle size of 0.1 μm or more and 100 μm or less. The median particle size refers to the particle size at which the cumulative volume in the volume-based particle size distribution is 50%. The volume-based particle size distribution is measured, for example, using a laser diffraction analyzer or an image analyzer.

[0038] The solid electrolyte material of the first embodiment may also have a median particle size of 0.5 μm or more and 10 μm or less. This allows the solid electrolyte material to have higher conductivity. Furthermore, when the solid electrolyte material of the first embodiment is mixed with other materials such as an active material, the dispersion of the solid electrolyte material of the first embodiment and the other materials becomes better.

[0039] <Method for producing solid electrolyte material>

[0040] The solid electrolyte material of the first embodiment can be produced by, for example, the following method.

[0041] Raw material powders are prepared and mixed so as to obtain the target composition. The raw material powders may be, for example, halides.

[0042] As an example, when the target composition is Li 2.8 Ti 0.4 Zr 0.4 In F6, LiF, TiF4, and ZrF4 are mixed at a molar ratio of about 2.8:0.4:0.4. Alternatively, the raw material powders may be mixed at a molar ratio adjusted in advance to offset compositional variations that may occur during the synthesis process.

[0043] The raw material powders are mechanochemically reacted (i.e., by mechanochemical grinding) in a mixing device such as a planetary ball mill to obtain a reactant. The reactant may be calcined in a vacuum or in an inert atmosphere. Alternatively, the reactant may be obtained by calcining a mixture of the raw material powders in a vacuum or in an inert atmosphere. Calcination is preferably performed at a temperature of, for example, 100° C. to 300° C. for at least one hour. In order to suppress composition changes during calcination, the raw material powders are preferably calcined in a sealed container such as a quartz tube.

[0044] By these methods, the solid electrolyte material of the first embodiment is obtained.

[0045] (Second embodiment)

[0046] Hereinafter, the second embodiment will be described, and matters described in the first embodiment will be omitted.

[0047] The battery of the second embodiment comprises 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 of the positive electrode, the electrolyte layer, and the negative electrode contains the solid electrolyte material of the first embodiment. The battery of the second embodiment, because it contains the solid electrolyte material of the first embodiment, has excellent charge and discharge characteristics. This battery may also be an all-solid-state battery.

[0048] Figure 1 A cross-sectional view of a battery 1000 according to a second embodiment is shown.

[0049] The battery 1000 of the second embodiment includes a positive electrode 201 , an electrolyte layer 202 , and a negative electrode 203 . The electrolyte layer 202 is provided between the positive electrode 201 and the negative electrode 203 .

[0050] The positive electrode 201 includes positive electrode active material particles 204 and solid electrolyte particles 100 .

[0051] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material.

[0052] The negative electrode 203 includes negative electrode active material particles 205 and solid electrolyte particles 100 .

[0053] The solid electrolyte particles 100 are particles made of the solid electrolyte material of the first embodiment, or particles containing the solid electrolyte material of the first embodiment as a main component. The term "particles containing the solid electrolyte material of the first embodiment as a main component" refers to particles in which the solid electrolyte material of the first embodiment is the largest component by mass.

[0054] The positive electrode 201 contains a material that can intercalate and deintercalate metal ions (eg, lithium ions), such as a positive electrode active material (eg, positive electrode active material particles 204 ).

[0055] Examples of positive electrode active materials are lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal sulfur oxides or transition metal nitrogen oxides. Examples of lithium-containing transition metal oxides are Li(Ni, Co, Al)O2, Li(Ni, Co, Mn)O2 or LiCoO2. In the present disclosure, the notation "(Ni, Co, Al)" in the chemical formula represents at least one element selected from the group of elements in the brackets. That is, "(Ni, Co, Al)" is synonymous with "at least one selected from Ni, Co and Al". The same applies to other elements.

[0056] The positive electrode active material particles 204 may also have a median particle size of 0.1 μm or greater and 100 μm or less. When the positive electrode active material particles 204 have a median particle size of 0.1 μm or greater, the dispersion of the positive electrode active material particles 204 and the solid electrolyte particles 100 in the positive electrode 201 is improved. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material particles 204 have a median particle size of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles 204 is increased. This enables the battery 1000 to operate at high power.

[0057] The positive electrode active material particles 204 may have a larger median diameter than the solid electrolyte particles 100. This improves the dispersion state of the positive electrode active material particles 204 and the solid electrolyte particles 100 in the positive electrode 201.

[0058] To improve battery energy density and power, in the positive electrode 201 , the ratio of the volume of the positive electrode active material particles 204 to the total volume of the positive electrode active material particles 204 and the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0059] A coating layer may also be formed on at least a portion of the surface of the positive electrode active material particles 204. For example, the coating layer may be formed on the surface of the positive electrode active material particles 204 before being mixed with the conductive additive and the binder. Examples of the coating material included in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. When the solid electrolyte particles 100 contain a sulfide solid electrolyte, the coating material may also contain the solid electrolyte material of the first embodiment to suppress oxidative decomposition of the sulfide solid electrolyte. When the solid electrolyte particles 100 contain the solid electrolyte material of the first embodiment, the coating material may also contain an oxide solid electrolyte to suppress oxidative decomposition of the solid electrolyte material. Lithium niobate, which has excellent stability at high potentials, may also be used as the oxide solid electrolyte. By suppressing oxidative decomposition of the solid electrolyte material, the increase in battery overvoltage can be suppressed.

[0060] In order to increase the energy density and power of the battery, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0061] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may also be a solid electrolyte layer.

[0062] The electrolyte layer 202 may be composed solely of the solid electrolyte material of the first embodiment. Alternatively, it may be composed solely of a solid electrolyte material different from the solid electrolyte material of the first embodiment. Examples of solid electrolyte materials different from the solid electrolyte material of the first embodiment include Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or LiI. Here, X is at least one selected from F, Cl, Br, and I.

[0063] Hereinafter, the solid electrolyte material of the first embodiment is referred to as a first solid electrolyte material. A solid electrolyte material different from the solid electrolyte material of the first embodiment is referred to as a second solid electrolyte material.

[0064] Electrolyte layer 202 may contain not only the first solid electrolyte material but also the second solid electrolyte material. The first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed in electrolyte layer 202. The layers formed of the first solid electrolyte material and the layers formed of the second solid electrolyte material may be stacked along the stacking direction of battery 1000.

[0065] Figure 2 A cross-sectional view of a battery 2000 according to a second embodiment is shown.

[0066] like Figure 2As shown, battery 2000 may also include a positive electrode 201, a first electrolyte layer 212, a second electrolyte layer 222, and a negative electrode 203. That is, electrolyte layer 202 may include a first electrolyte layer 212 and a second electrolyte layer 222. First electrolyte layer 212 is provided between positive electrode 201 and negative electrode 203. Second electrolyte layer 222 is disposed between first electrolyte layer 212 and negative electrode 203.

[0067] In battery 2000, the first electrolyte layer 212 may also contain the solid electrolyte material of the first embodiment. Since the solid electrolyte material of the first embodiment has high oxidation resistance, the solid electrolyte material contained in the second electrolyte layer 222 can be used without being oxidized. As a result, the charge and discharge efficiency of the battery can be improved.

[0068] In battery 2000, the solid electrolyte material contained in the second electrolyte layer 222 may also have a lower reduction potential than the solid electrolyte material contained in the first electrolyte layer 212. This allows the solid electrolyte material contained in the first electrolyte layer 212 to be used without undergoing reduction. As a result, the battery's charge and discharge efficiency can be improved. For example, when the first electrolyte layer 212 contains the solid electrolyte material of the first embodiment, the second electrolyte layer 222 may also contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte material.

[0069] In order to increase the energy density and power of the battery, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0070] The negative electrode 203 contains a material that can intercalate and deintercalate metal ions (eg, lithium ions), such as a negative electrode active material (eg, negative electrode active material particles 205 ).

[0071] Examples of negative electrode active materials include metal materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. The metal material may be a single metal or an alloy. Examples of metal materials include lithium metal or lithium alloys. Examples of carbon materials include natural graphite, coke, graphitized carbon, carbon fibers, spherical carbon, artificial graphite, or amorphous carbon. From the perspective of capacity density, preferred examples of negative electrode active materials include silicon (i.e., Si), tin (i.e., Sn), silicon compounds, or tin compounds.

[0072] The negative electrode active material can also be selected in consideration of the reduction resistance of the solid electrolyte material contained in the negative electrode 203. For example, when the negative electrode 203 contains the solid electrolyte material of the first embodiment, the negative electrode active material can also be a material that can intercalate and deintercalate lithium ions at a voltage of 0.27V or more relative to lithium. Examples of such negative electrode active materials are titanium oxide, indium metal, or lithium alloys. An example of titanium oxide is Li4Ti5O 12 , LiTi2O4 or TiO2. By using the above-mentioned negative electrode active material, the solid electrolyte material of the first embodiment contained in the negative electrode 203 can be suppressed from undergoing reductive decomposition. As a result, the charge and discharge efficiency of the battery can be improved.

[0073] The negative electrode active material particles 205 may also have a median particle size of 0.1 μm or greater and 100 μm or less. When the negative electrode active material particles 205 have a median particle size of 0.1 μm or greater, the dispersion of the negative electrode active material particles 205 and the solid electrolyte particles 100 in the negative electrode 203 is improved. This improves the battery's charge and discharge characteristics. When the negative electrode active material particles 205 have a median particle size of 100 μm or less, the lithium diffusion rate within the negative electrode active material particles 205 is increased, enabling the battery to operate at high power.

[0074] The negative electrode active material particles 205 may have a larger median diameter than the solid electrolyte particles 100. This improves the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 in the negative electrode 203.

[0075] To improve the energy density and power 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.

[0076] In order to increase the energy density and power of the battery, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0077] At least one selected from the positive electrode 201 , the electrolyte layer 202 , and the negative electrode 203 may contain a second solid electrolyte material for the purpose of improving ion conductivity, chemical stability, and electrochemical stability.

[0078] The second solid electrolyte material may be a sulfide solid electrolyte.

[0079] 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 Li10 GeP2S 12 .

[0080] When the electrolyte layer 202 contains the solid electrolyte material of the first embodiment, the negative electrode 203 may also contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte material. By coating the negative electrode active material with the electrochemically stable sulfide solid electrolyte, contact between the solid electrolyte material of the first embodiment and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery can be reduced.

[0081] The second solid electrolyte material may also be an oxide solid electrolyte.

[0082] Examples of oxide solid electrolytes are:

[0083] (i) NASICON type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions,

[0084] (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3,

[0085] (iii)Li 14 ZnGe4O 16 , LISICON type solid electrolytes such as Li4SiO4, LiGeO4 or their elemental substitutions,

[0086] (iv)Li7La3Zr2O 12 or its element-substituted garnet-type solid electrolyte, or

[0087] (v) Li3PO4 or its N-substituted counterparts.

[0088] As described above, the second solid electrolyte material may be a halide solid electrolyte.

[0089] Examples of halide solid electrolytes include Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or LiI, wherein X is at least one selected from F, Cl, Br, and I.

[0090] Other examples of halide solid electrolyte materials are Li a Me b Y cA compound represented by X6. Wherein, a+mb+3c=6 and c>0 are satisfied. Me is at least one selected from metal elements and semi-metal elements other than Li and Y. m represents the valence of Me. The so-called "semi-metal elements" are B, Si, Ge, As, Sb and Te. The so-called "metal elements" are all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S and Se).

[0091] In order to improve the ionic conductivity of the halide solid electrolyte material, Me may be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. The halide solid electrolyte may also be Li3YCl6 or Li3YBr6.

[0092] The second solid electrolyte material may also be an organic polymer solid electrolyte.

[0093] Examples of organic polymer solid electrolytes include compounds of polymer compounds and lithium salts.

[0094] The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can further improve ion conductivity because it contains a large amount of lithium salt.

[0095] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or 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.

[0096] At least one selected from the positive electrode 201 , the electrolyte layer 202 , and the negative electrode 203 may contain a non-aqueous electrolyte solution, a gel electrolyte, or an ionic liquid for the purpose of facilitating the transfer of lithium ions and improving the power characteristics of the battery.

[0097] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0098] Examples of non-aqueous solvents include cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorinated solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of chain carbonate solvents include dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Chain ether solvents include 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a chain ester solvent is methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, ethyl fluoromethyl carbonate, or dimethylene fluorocarbonate. One non-aqueous solvent selected from these may be used alone. Alternatively, a combination of two or more non-aqueous solvents selected from these may be used.

[0099] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or 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 is, for example, in the range of 0.5 mol / L to 2 mol / L.

[0100] As the gel electrolyte, a polymer material impregnated with a non-aqueous electrolyte can be used. Examples of the polymer material are polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0101] Examples of cations contained in ionic liquids are:

[0102] (i) Aliphatic chain quaternary salts (quaternary salts) such as tetraalkylammonium or tetraalkylphosphonium,

[0103] (ii) aliphatic cyclic ammonium such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium or piperidinium, or

[0104] (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium.

[0105] An example of an anion contained in an ionic liquid is PF6 - 、BF4 - 、SbF6 - 、AsF6 - 、SO3CF3 - 、N(SO2CF3)2 - 、N(SO2C2F5)2- , N(SO2CF3)(SO2C4F9)- or C(SO2CF3)3 - .

[0106] The ionic liquid may also contain a lithium salt.

[0107] At least one selected from 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.

[0108] The example of binding agent is polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamide-imide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyether sulfone, hexafluoropolypropylene, styrene-butadiene rubber or carboxymethyl cellulose. Copolymer also can be used as binding agent. The example of such binding agent is a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid and hexadiene. Also can use the mixture of two or more materials selected from above-mentioned these as binding agent.

[0109] In order to reduce resistance, at least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive.

[0110] Examples of conductive additives are:

[0111] (i) Graphites such as natural graphite or artificial graphite,

[0112] (ii) Carbon blacks such as acetylene black and Ketjen black,

[0113] (iii) Conductive fibers such as carbon fibers or metal fibers,

[0114] (iv) fluorocarbons,

[0115] (v) Metal powders such as aluminum,

[0116] (vi) Conductive whiskers such as zinc oxide or potassium titanate,

[0117] (vii) conductive metal oxides such as titanium oxide, or

[0118] (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene.

[0119] For cost reduction, the conductive auxiliary agent (i) or (ii) mentioned above may be used.

[0120] Examples of the shape of the battery of the second embodiment include a coin shape, a cylindrical shape, a square shape, a sheet shape, a button shape, a flat shape, or a laminated shape.

[0121] The battery of the second embodiment can also be manufactured, for example, by preparing materials for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and producing a stacked body in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order by a known method.

[0122] Example

[0123] Hereinafter, the present disclosure will be described in more detail with reference to Examples and Comparative Examples.

[0124] <Example 1>

[0125] (Fabrication of Solid Electrolyte Materials)

[0126] In an argon atmosphere with a dew point below -60°C (hereinafter referred to as "dry argon atmosphere"), LiF, TiF4 and ZrF4 were prepared as raw material powders in a molar ratio of LiF:TiF4:ZrF4=2.8:0.4:0.4. These materials were crushed and mixed in a mortar. The obtained mixture was milled at 500 rpm for 12 hours using a planetary ball mill. In this manner, a powder of the solid electrolyte material of Example 1 was obtained. The solid electrolyte material of Example 1 has a 2.8 Ti 0.4 Zr 0.4 The composition represented by F6.

[0127] (Evaluation of ion conductivity)

[0128] Figure 3 A schematic diagram showing a press mold 300 for evaluating the ion conductivity of a solid electrolyte material.

[0129] The press forming die 300 includes a punch upper portion 301, a frame die 302, and a punch lower portion 303. The frame die 302 is formed of insulating polycarbonate. The punch upper portion 301 and the punch lower portion 303 are formed of electronically conductive stainless steel.

[0130] use Figure 3 The press molding die 300 shown was used to evaluate the ion conductivity of the solid electrolyte material of Example 1 by the following method.

[0131] In a dry atmosphere with a dew point of -30°C or less, the powder of the solid electrolyte material of Example 1 was filled into the press die 300. Inside the press die 300, a pressure of 400 MPa was applied to the solid electrolyte material of Example 1 using the upper punch 301 and the lower punch 303.

[0132] The upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research, Versa STAT4) equipped with a frequency response analyzer while applying pressure. The upper punch 301 was connected to the working electrode and the potential measurement terminal. The lower punch 303 was connected to the counter electrode and the reference electrode. The impedance of the solid electrolyte material was measured at room temperature using electrochemical impedance spectroscopy.

[0133] Figure 4 This is a graph showing a Cole-Cole plot obtained by impedance measurement of the solid electrolyte material of Example 1.

[0134] Figure 4 The real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is the smallest is regarded as the resistance value of the solid electrolyte material to ion conduction. Figure 4 The arrow R shown in SE Using this resistance value, the ion conductivity was calculated based on the following mathematical formula (2).

[0135] σ=(R SE ×S / t) -1 (2)

[0136] Wherein, σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper portion 301 of the punch ( Figure 3 The cross-sectional area of the hollow portion of the frame mold 302 is equal to that of the hollow portion of the frame mold 302). SE represents the resistance value of the solid electrolyte material during impedance measurement. t represents the thickness of the solid electrolyte material (i.e., Figure 3 , the thickness of the layer formed by the powder 101 of the solid electrolyte material).

[0137] The ionic conductivity of the solid electrolyte material of Example 1 measured at 25°C was 1.94×10 -6 S / cm.

[0138] (Battery Production)

[0139] In a dry argon atmosphere, the solid electrolyte material of Example 1 and the active material, LiCoO2, were prepared at a volume ratio of 30:70. These materials were mixed in an agate mortar to obtain a positive electrode mixture.

[0140] Next, LiCl and YCl₃ were prepared in a molar ratio of LiCl:YCl₃=3:1. These materials were crushed and mixed in a mortar. The resulting mixture was milled at 500 rpm using a planetary ball mill for 12 hours. By operating in this manner, a halide solid electrolyte (hereinafter referred to as "LYC") having a composition represented by Li₃YCl₃ was obtained.

[0141] LYC (60 mg), the solid electrolyte material from Example 1 (26 mg), and the aforementioned positive electrode mixture (9.1 mg) were stacked in this order in an insulating cylinder with an inner diameter of 9.5 mm. A pressure of 300 MPa was applied to the resulting stack to form the second electrolyte layer, the first electrolyte layer, and the positive electrode. In other words, the first electrolyte layer, formed from the solid electrolyte material from Example 1, was sandwiched between the second electrolyte layer and the positive electrode. The thicknesses of the second and first electrolyte layers were 450 μm and 150 μm, respectively.

[0142] Next, metal In (thickness: 200 μm) was stacked on the second electrolyte layer, and a pressure of 80 MPa was applied to the resulting stack to form a negative electrode.

[0143] Next, current collectors made of stainless steel were attached to the positive electrode and the negative electrode, and current collecting leads were attached to the current collectors.

[0144] Finally, an insulating ferrule was used to isolate the interior of the insulating tube from the external atmosphere, thereby sealing the interior of the tube.

[0145] (Charge and discharge test)

[0146] Figure 5 This is a graph showing the initial discharge characteristics of the battery of Example 1. The initial charge and discharge characteristics were measured by the following method.

[0147] The battery of Example 1 was placed in a constant temperature chamber at 85°C.

[0148] The battery of Example 1 was charged at 27 μA / cm 2 The battery was charged to a voltage of 3.6 V at a current density equivalent to a 0.02C rate.

[0149] Next, the battery of Example 1 was tested at 27 μA / cm 2 The battery was discharged at a current density of 1.9 V.

[0150] As a result of the charge and discharge test, the battery of Example 1 had an initial discharge capacity of 720 μAh.

[0151] <Examples 2 to 11>

[0152] (Fabrication of Solid Electrolyte Materials)

[0153] In Examples 2 to 11, LiF, TiF4, and ZrF4 were prepared as raw material powders in a molar ratio of LiF:TiF4:ZrF3=(6-4b):(1-x)b:xb.

[0154] Solid electrolyte materials of Examples 2 to 11 were obtained in the same manner as in Example 1 except for the above-mentioned matters.

[0155] Table 1 shows the values of x, b, and the Li / (Ti+Zr) molar ratio for the solid electrolyte materials of Examples 2 to 11.

[0156] (Evaluation of ion conductivity)

[0157] The ion conductivity of the solid electrolyte materials of Examples 2 to 11 was measured in the same manner as in Example 1. Table 1 shows the measurement results.

[0158] (Charge and discharge test)

[0159] Using the solid electrolyte materials of Examples 2 to 11, the same operation as in Example 1 was carried out to obtain batteries of Examples 2 to 11.

[0160] The batteries of Examples 2 to 11 were subjected to charge and discharge tests in the same manner as in Example 1. The batteries of Examples 2 to 11 were charged and discharged in the same manner as in Example 1, and the batteries performed well.

[0161] <Comparative Example 1>

[0162] As a solid electrolyte material, LiBF4 is used instead of Li 2.8 Ti 0.4 Zr 0.4 F6.

[0163] The ion conductivity of LiBF4 was measured in the same manner as in Example 1. The ion conductivity measured at 25°C was 6.67×10 -9 S / cm.

[0164] A battery of Comparative Example 1 was obtained in the same manner as in Example 1 using LiBF 4 as a solid electrolyte material.

[0165] The battery of Comparative Example 1 was subjected to a charge and discharge test in the same manner as in Example 1. The results showed that the battery of Comparative Example 1 had an initial discharge capacity of 0.01 μAh or less. In other words, the battery of Comparative Example 1 was neither charged nor discharged.

[0166] Table 1 shows the solid electrolyte materials in Examples 1 to 11 and Comparative Example 1 and the evaluation results.

[0167] Table 1

[0168]

[0169] <Inspection>

[0170] The solid electrolyte materials of Examples 1 to 11 have a 1×10- 8 S / cm or higher. On the other hand, the solid electrolyte material of the comparative example has a conductivity of less than 1×10- 8 S / cm low ion conductivity.

[0171] The solid electrolyte materials of Examples 1, 2, 3, 4, and 10 have the same value of x (i.e., x = 0.5). Comparison of Examples 1, 2, and 4 with Examples 3 and 10 reveals that, among solid electrolyte materials having the same value of x, when 0.8 ≤ b ≤ 0.92 is satisfied, the ionic conductivity of the solid electrolyte material is further improved.

[0172] The batteries of Examples 1 to 11 were all charged and discharged at 85° C. On the other hand, the battery of Comparative Example 1 was neither charged nor discharged.

[0173] Since the solid electrolyte materials of Examples 1 to 11 do not contain sulfur, hydrogen sulfide is not generated.

[0174] As described above, the solid electrolyte material of the present disclosure is suitable for providing a battery that has high lithium ion conductivity and can be charged and discharged well.

[0175] Industrial applicability

[0176] The solid electrolyte material disclosed herein can be used in, for example, all-solid-state lithium-ion secondary batteries.

[0177] Explanation of symbols

[0178] 100: Solid electrolyte particles

[0179] 101: Powder of solid electrolyte material

[0180] 201: Positive electrode

[0181] 202: Electrolyte layer

[0182] 212: 1st electrolyte layer

[0183] 222: Second electrolyte layer

[0184] 203: Negative electrode

[0185] 204: Positive electrode active material particles

[0186] 205: Negative electrode active material particles

[0187] 300: Pressurized forming die

[0188] 301: Upper part of the punch

[0189] 302: Frame mold

[0190] 303: lower part of punch

[0191] 1000: Battery

[0192] 2000: Batteries

Claims

1. A solid electrolyte material comprising Li, Ti, Zr and F, The solid electrolyte material is represented by the following composition formula (1): Li 6-4b (Ti 1-x Zr x ) b Type F6 (1) in, Satisfies 0<x<1 and 0.6<b≤0.

92.

2. The solid electrolyte material according to claim 1, wherein The ratio of the amount of substance of Li to the total amount of substances of Ti and Zr is 2.0 or more and 6.0 or less.

3. The solid electrolyte material according to claim 1, wherein Satisfies the mathematical formula: 0.1≤x≤0.

8.

4. The solid electrolyte material according to claim 1 or 3, wherein Satisfies the mathematical formula: 0.8≤b≤0.

92.

5. A battery comprising: positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, in, At least one selected from the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to any one of claims 1 to 4.

6. The battery according to claim 5, wherein The electrolyte layer includes a first electrolyte layer and a second electrolyte layer, The first electrolyte layer is disposed between the positive electrode and the negative electrode, The second electrolyte layer is disposed between the first electrolyte layer and the negative electrode. The first electrolyte layer contains the solid electrolyte material.

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