Solid electrolyte material and battery using the same

Abstract

A solid electrolyte material according to the present disclosure comprises Li, Yb, and X. X is at least two elements selected from the group consisting of F, Cl, Br, and I. A battery 1000 according to the present disclosure comprises a positive electrode 201, a negative electrode 203, and an electrolyte layer 202 provided 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.

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 an all-solid-state battery using a sulfide solid electrolyte material.

[0003] Non-Patent Documents 1 and 2 disclose solid electrolyte materials represented by the composition formulae Li3YbCl6 and Li3YbBr6, respectively. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-129312 [Non-Patent Document 1] Z. anorg. allg. Chem., 623,1067-1073(1997) [Non-patent document 2] Z. anorg. allg. Chem., 623,1352-1356(1997) Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a new, highly useful solid electrolyte material. [Means for solving the problem]

[0006] The solid electrolyte material of the present disclosure comprises Li, Yb, and X, X is at least two selected from the group consisting of F, Cl, Br, and I. [Effects of the Invention]

[0007] The present disclosure provides a new, highly useful solid electrolyte material. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment. [Figure 2] FIG. 2 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of a solid electrolyte material. [Figure 3] FIG. 3 is a graph showing a Cole-Cole plot obtained by alternating current (AC) impedance measurement of the solid electrolyte material according to Example 1. [Figure 4] FIG. 4 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 1 to 22, Comparative Example 1, and Comparative Example 2. [Figure 5] FIG. 5 is a graph showing the initial discharge characteristics of the battery according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0010] (First embodiment) The solid electrolyte material according to the first embodiment is composed of Li, Yb, and X, where X is at least two selected from the group consisting of F, Cl, Br, and I.

[0011] The solid electrolyte material according to the first embodiment is a novel, highly useful solid electrolyte material. 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, 5.0 × 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, 5.0×10 -5 It may have an ionic conductivity of 5 S / cm or more.

[0012] 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.

[0013] The solid electrolyte material according to the first embodiment is substantially free of sulfur. The fact that the solid electrolyte material according to the first embodiment is substantially free of sulfur means that the solid electrolyte material does not contain sulfur as a constituent element, except for sulfur inevitably mixed in as an impurity. In this case, the amount of sulfur mixed in the solid electrolyte material as an impurity is, for example, 1 mol % or less. The solid electrolyte material according to the first embodiment is sulfur-free. A sulfur-free solid electrolyte material does not generate hydrogen sulfide even when exposed to the atmosphere, and is therefore highly safe. The sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

[0014] The solid electrolyte material according to the first embodiment may contain elements that are inevitably mixed in. 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 for producing or storing the solid electrolyte material. In the solid electrolyte material according to the first embodiment, the amount of such elements that are inevitably mixed in is, for example, 1 mol % or less.

[0015] In order to enhance the ionic conductivity of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, X may be at least two selected from the group consisting of Cl, Br, and I.

[0016] The solid electrolyte material according to the first embodiment may be a material represented by the following composition formula (1). Li 6-3a Yb a Cl 6-x-y-z Br x I y F z ···(1) Here are the five formulas: 0.5 ≤ a ≤ 1.5, 0 < x < 6, 0 ≤ y ≤ 3, 0 ≤ z ≤ 2, and 0 < x + y + z ≤ 6 are satisfied. The material represented by the composition formula (1) has high ionic conductivity.

[0017] In order to increase the ionic conductivity of the solid electrolyte material, in the above composition formula (1), the following five mathematical formulas may be satisfied. 0.8 ≤ a ≤ 1.2, 0 < x < 6, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1, and 0 < x + y + z ≤ 6

[0018] The upper and lower limit values of the range of a in the composition formula (1) may be defined by any combination selected from the numerical values of 0.8, 0.9, 1, 1.1, and 1.2.

[0019] In order to increase the ionic conductivity of the solid electrolyte material, in the composition formula (1), 0.8 ≤ a ≤ 1.2 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the composition formula (1), 0.8 ≤ a ≤ 1.1 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the composition formula (1), 0.8 ≤ a ≤ 1 may be satisfied.

[0020] The upper and lower limit values of the range of x in the composition formula (1) may be defined by any combination selected from the numerical values greater than 0 (i.e., 0 < x), 0.75, 1, 1.5, 1.7, 1.9, 2, 2.25, 2.5, 3, 4, 5, and less than 6 (i.e., x < 6).

[0021] In order to increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0 < x ≤ 4 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0 < x ≤ 3 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 1.5 ≤ x ≤ 3 may be satisfied.

[0022] The upper and lower limit values of the range of y in the compositional formula (1) may be defined by any combination selected from the numerical values of 0, 0.5, 1, 1.5, and 2.

[0023] In order to increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0 ≤ y ≤ 2 may be satisfied. In order to increase the ionic conductivity of the solid electrolyte material even more, in the compositional formula (1), the mathematical formula: 0 ≤ y ≤ 1.5 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0 ≤ y ≤ 1 may be satisfied. In order to further increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0.5 ≤ y ≤ 2 may be satisfied.

[0024] The upper and lower limit values of the range of z in the compositional formula (1) may be defined by any combination selected from the numerical values of 0, 0.1, 0.3, 0.5, and 1.

[0025] In order to increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 0 ≤ z ≤ 1 may be satisfied.

[0026] The X-ray diffraction pattern of the solid electrolyte material according to the first embodiment can be obtained by X-ray diffraction measurement using the θ-2θ method with Cu-Kα radiation (wavelengths of 1.5405 Å and 1.5444 Å, i.e., wavelengths of 0.15405 nm and 0.15444 nm). The obtained X-ray diffraction pattern may have at least two peaks in the diffraction angle 2θ range of 26.0° to 35.0°, and at least one peak in the diffraction angle 2θ range of 13.0° to 17.0°. A crystalline phase having such peaks is called a first crystalline phase. In a solid electrolyte material containing the first crystalline phase, paths for lithium ion diffusion within the crystal are easily formed. Therefore, when the solid electrolyte material according to the first embodiment contains the first crystalline phase, the solid electrolyte material according to the first embodiment has high ionic conductivity.

[0027] The crystal system of the first crystal phase belongs to the monoclinic system. In this disclosure, "monoclinic" refers to a crystal phase having a crystal structure similar to that of Li3InCl6 disclosed in ICSD (Inorganic Crystal Structure Database) Collection Code 89617 and having an X-ray diffraction pattern specific to this structure. In this disclosure, "having a similar crystal structure" means being classified into the same space group and having a similar atomic arrangement structure, but does not limit the lattice constant. Furthermore, the relative intensity ratio and diffraction angle of the diffraction peaks in the X-ray diffraction pattern of the solid electrolyte material according to the first embodiment may vary from the diffraction pattern of Li3InCl6.

[0028] The solid electrolyte material according to the first embodiment may further contain a second crystalline phase different from the first crystalline phase. That is, the solid electrolyte material according to the first embodiment may further contain a second crystalline phase having a clear peak outside the range of the diffraction angle 2θ described above. The second crystalline phase may be, for example, a crystalline phase belonging to the trigonal or orthorhombic system. Here, "trigonal" in this disclosure refers to a crystalline phase having a crystalline structure similar to that of Li3ErCl6 disclosed in ICSD Collection Code 50151. Furthermore, "orthorhombic" refers to a crystalline phase having a crystalline structure similar to that of Li3YbCl6 disclosed in ICSD Collection Code 50152.

[0029] The solid electrolyte material according to the first embodiment may be crystalline or amorphous. Furthermore, the solid electrolyte material according to the first embodiment may be a mixture of crystalline and amorphous. Here, crystalline refers to the presence of a peak in the X-ray diffraction pattern. Amorphous refers to the presence of a broad peak (i.e., a halo) in the X-ray diffraction pattern. When amorphous and crystalline are mixed, a peak and a halo are present in the X-ray diffraction pattern.

[0030] 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 be formed into the shape of a pellet or a plate.

[0031] 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. The median diameter refers to the particle size when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measurement device or an image analysis device.

[0032] The solid electrolyte material according to the first embodiment may have a median diameter of 0.5 μm or more and 10 μm or less. This allows the solid electrolyte material according to the first embodiment to have higher ionic conductivity. Furthermore, when the solid electrolyte material according to the first embodiment is mixed with other materials such as active materials, the solid electrolyte material according to the first embodiment and the other materials are well dispersed.

[0033] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment is produced, for example, by the following method.

[0034] Two or more kinds of halide raw material powders are mixed together to obtain a desired composition.

[0035] As an example, if the desired composition is Li3YbBr 0.75 Cl 5.25 In this case, the LiBr raw material powder, the LiCl raw material powder, and the YbCl raw material powder (i.e., the raw material powders of the three halides) are mixed in a molar ratio of approximately 0.75:2.25:1. The raw material powders may be mixed in a pre-adjusted molar ratio to offset composition changes that may occur during the synthesis process.

[0036] The mixture of raw material powders is fired in an inert gas atmosphere to react with each other and obtain a reactant. Examples of the inert gas include helium, nitrogen, and argon. The firing process may be performed in a vacuum. In the firing process, the powders of the mixed materials may be placed in a container (e.g., a crucible or a sealed tube) and fired in a heating furnace.

[0037] Alternatively, the raw material powders may be reacted mechanochemically (i.e., by using a mechanochemical milling method) in a mixing device such as a planetary ball mill to obtain a reactant, which may then be calcined in an inert gas atmosphere or in vacuum.

[0038] By these methods, the solid electrolyte material according to the first embodiment can be obtained.

[0039] (Second embodiment) A second embodiment of the present disclosure will be described below. The matters described in the first embodiment may be omitted.

[0040] In the second embodiment, a battery using the solid electrolyte material according to the first embodiment will be described.

[0041] 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.

[0042] 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.

[0043] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0044] 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 provided between the positive electrode 201 and the negative electrode 203.

[0045] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0046] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0047] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0048] The solid electrolyte particles 100 are particles containing the solid electrolyte material according to the first embodiment. The solid electrolyte particles 100 may be particles made of the solid electrolyte material according to the first embodiment, or particles containing the solid electrolyte material according to the first embodiment as a main component. Here, particles containing the solid electrolyte material according to the first embodiment as a main component refer to particles in which the component contained most abundantly in terms of molar ratio is the solid electrolyte material according to the first embodiment.

[0049] 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.

[0050] The positive electrode 201 contains a material capable of absorbing and releasing metal ions (for example, lithium ions). The material is, for example, a positive electrode active material (for example, positive electrode active material particles 204).

[0051] 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. Examples of the lithium-containing transition metal oxide include Li(Ni,Co,Al)O2 and LiCoO2.

[0052] In the present disclosure, the notation "(A, B, C)" in a chemical formula means "at least one selected from the group consisting of A, B, and C." For example, "(Ni, Co, Al)" is synonymous with "at least one selected from the group consisting of Ni, Co, and Al."

[0053] 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 are well dispersed in the positive electrode 201. This improves the charge / discharge characteristics of the battery. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles 204 improves. This allows the battery to operate at high power.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may be a solid electrolyte layer.

[0058] The electrolyte layer 202 may be made of only the solid electrolyte material according to the first embodiment, or may be made of only a solid electrolyte material different from the solid electrolyte material according to the first embodiment.

[0059] Examples of solid electrolyte materials different from the solid electrolyte material according to the first embodiment include Li2MgX'4, Li2FeX'4, Li(Al,Ga,In)X'4, Li3(Al,Ga,In)X'6, or LiI, where X' is at least one selected from the group consisting of F, Cl, Br, and I. Thus, the solid electrolyte material different from the solid electrolyte material according to the first embodiment may be a solid electrolyte containing a halogen element, i.e., a halide solid electrolyte.

[0060] 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.

[0061] The 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 the electrolyte layer 202. A layer made of the first solid electrolyte material and a layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

[0062] The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 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 1000 μm or less, the battery can operate at high power.

[0063] The negative electrode 203 contains a material capable of absorbing and releasing metal ions such as lithium ions. The material is, for example, a negative electrode active material (for example, negative electrode active material particles 205).

[0064] 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.

[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 are 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 improves the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 in the negative electrode 203.

[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 sum of the volume of the negative electrode active material particles 205 and the volume of the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0068] 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.

[0069] 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 increasing ionic conductivity, chemical stability, and electrochemical stability.

[0070] As mentioned above, the second solid electrolyte material may be a halide solid electrolyte.

[0071] Examples of halide solid electrolytes are Li2MgX'4, Li2FeX'4, Li(Al,Ga,In)X'4, Li3(Al,Ga,In)X'6, or LiI, where X' is at least one selected from the group consisting of F, Cl, Br, and I.

[0072] Other examples of halide solid electrolytes are Li p Me q Y r Z6, where p + m'q + 3r = 6 and r > 0. Me is at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. The value of m' represents the valence of Me. Z is at least one element selected from the group consisting of F, Cl, Br, and I. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in Groups 1 to 12 of the Periodic Table (excluding hydrogen) and all elements in Groups 13 to 16 of the Periodic Table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). To increase the ionic conductivity of the halide solid electrolyte, Me may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0073] The second solid electrolyte material may be a sulfide solid electrolyte.

[0074] 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.

[0075] The second solid electrolyte material may be an oxide solid electrolyte.

[0076] 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 is.

[0077] The second solid electrolyte material may be an organic polymer solid electrolyte.

[0078] An example of the organic polymer solid electrolyte is a compound of a polymer compound and a lithium salt.

[0079] The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, and therefore can further increase 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 solution, 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 are 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, 0.5 mol / L or more and 2 mol / L 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 is.

[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 can 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. Mixtures of two or more of the above materials may also be used as binders.

[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) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene. For cost reduction, the conductive additives (i) or (ii) above 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] The solid electrolyte material according to the embodiment can be represented by the above-mentioned composition formula (1).

[0097] 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 LiBr, LiCl, and YbCl3 were prepared in a molar ratio of LiBr:LiCl:YbCl3 = 0.75:2.25:1. These raw material powders were ground and mixed in an agate mortar. The resulting mixed powder was placed in an alumina crucible and fired at 550°C for 1 hour in a dry argon atmosphere. The resulting fired product was ground in the agate mortar. In this way, a powder of the solid electrolyte material according to Example 1 was obtained. The solid electrolyte material according to Example 1 was composed of Li3YbBr 0.75 Cl 5.25 The composition was represented by the formula:

[0098] (Evaluation of ionic conductivity) FIG. 2 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of the solid electrolyte material.

[0099] The pressure molding die 300 had an upper punch 301, a frame 302, and a lower punch 303. The upper punch 301 and the lower punch 303 were both made of electronically conductive stainless steel. The frame 302 was made of insulating polycarbonate.

[0100] Using the pressure molding die 300 shown in FIG. 2, the ionic conductivity of the solid electrolyte material of Example 1 was evaluated by the following method.

[0101] In a dry argon atmosphere, the powder of the solid electrolyte material according to Example 1 was filled into the inside of a pressure molding die 300. Inside the pressure molding die 300, a pressure of 360 MPa was applied to the powder 101 of the solid electrolyte material according to Example 1 using an upper punch 301 and a lower punch 303.

[0102] While pressure was still applied, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research, VersaSTAT4) 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 impedance of the solid electrolyte material was measured at room temperature by electrochemical impedance measurement.

[0103] FIG. 3 is a graph showing a Cole-Cole plot obtained by AC impedance measurement of the solid electrolyte material according to Example 1.

[0104] In Figure 3, 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. The real value is indicated by the arrow R in Figure 3. SEUsing the resistance value, the ionic conductivity was calculated based on the following formula (2). σ=(R SE ×S / t) -1 ···(2) Here, σ represents ionic conductivity. S represents the contact area of ​​the solid electrolyte material with the punch upper portion 301. In other words, S is equal to the cross-sectional area of ​​the hollow portion of the frame mold 302 in FIG. 2. R SE represents the resistance value of the solid electrolyte material in impedance measurement. t represents the thickness of the solid electrolyte material. That is, t is equal to the thickness of the layer formed from the powder 101 of the solid electrolyte material in FIG. 2.

[0105] The ionic conductivity of the solid electrolyte material according to Example 1 measured at 25°C was 1.11 × 10 -3 It was S / cm.

[0106] (X-ray diffraction measurement) Fig. 4 is a graph showing the X-ray diffraction pattern of the solid electrolyte material according to Example 1. The results shown in Fig. 4 were measured by the following method.

[0107] The X-ray diffraction pattern of the solid electrolyte material of Example 1 was measured using an X-ray diffractometer (MiniFlex600, manufactured by Rigaku Co., Ltd.) in a dry environment with a dew point of −50° C. or less. The X-ray diffraction pattern was measured by the θ-2θ method using Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) as the X-ray source.

[0108] In the X-ray diffraction pattern of the solid electrolyte material according to Example 1, two peaks were present in the range of 26.0° or more and 35.0° or less, and one peak was present in the range of 13.0° or more and 17.0° or less. Therefore, the solid electrolyte material according to Example 1 contained a first crystalline phase (i.e., monoclinic crystals). The distinct X-ray diffraction peak angles attributed to the observed first crystalline phase are shown in Table 2.

[0109] (Battery construction) In a dry argon atmosphere, the solid electrolyte material according to Example 1 and LiCoO2 were prepared in a volume ratio of 30:70. These materials were mixed in a mortar to obtain a mixture.

[0110] In an insulating cylinder having an inner diameter of 9.5 mm, the solid electrolyte material according to Example 1 (80 mg) and the above mixture (10 mg) were stacked in this order. A pressure of 720 MPa was applied to the resulting stack, forming a solid electrolyte layer made of the solid electrolyte material according to Example 1 and a positive electrode made of the above mixture. The solid electrolyte layer had a thickness of 400 μm.

[0111] Next, metal In (thickness 200 μm), metal Li (thickness 200 μm), and metal In (thickness 200 μm) were laminated in this order on the solid electrolyte layer, and a pressure of 80 MPa was applied to the resulting laminate to form a negative electrode.

[0112] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0113] 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, the battery according to Example 1 was obtained.

[0114] (Charge / discharge test) 5 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.

[0115] The battery according to Example 1 was placed in a thermostatic chamber at 25°C.

[0116] 54μA / cm 2 The battery according to Example 1 was charged at a current density of 0.05 C until a voltage of 3.68 V was reached. The current density corresponds to a 0.05 C rate.

[0117] Next, 54 μA / cm 2The battery according to Example 1 was discharged at a current density of 0.1 V until a voltage of 1.88 V was reached.

[0118] As a result of the charge-discharge test, the battery according to Example 1 had an initial discharge capacity of 1.05 mAh.

[0119] <Examples 2 to 22> (Preparation of solid electrolyte materials) In Example 2, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 1:2:1.

[0120] In Example 3, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 1.5:1.5:1.

[0121] In Example 4, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2:1:1.

[0122] In Example 5, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2.25:0.75:1.

[0123] In Example 6, LiBr and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:YbCl3=3:1.

[0124] In Example 7, LiBr, LiCl, and YbBr3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbBr3=1:2:1.

[0125] In Example 8, LiBr, LiCl, and YbBr3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbBr3=2:1:1.

[0126] In Example 9, LiCl, LiBr, LiI, and YbCl3 were prepared as raw material powders in a molar ratio of LiCl:LiBr:LiI:YbCl3=1:1.5:0.5:1.

[0127] In Example 10, LiCl, LiBr, LiI, and YbCl3 were prepared as raw material powders in a molar ratio of LiCl:LiBr:LiI:YbCl3 = 0.5:1.5:1:1.

[0128] In Example 11, LiBr, LiI, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:YbCl3 = 2:1:1.

[0129] In Example 12, raw material powders of LiBr, LiI, YbCl3, and YbBr3 were prepared in a molar ratio of LiBr:LiI:YbCl3:YbBr3=2:1:0.83:0.17.

[0130] In Example 13, LiBr, LiI, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:YbCl3 = 1.5:1.5:1.

[0131] In Example 14, raw material powders of LiBr, LiI, YbCl3, and YbBr3 were prepared in a molar ratio of LiBr:LiI:YbCl3:YbBr3=1:2:0.67:0.33.

[0132] In Example 15, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2:0.4:1.2.

[0133] In Example 16, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2:0.7:1.1.

[0134] In Example 17, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2:1.3:0.9.

[0135] In Example 18, LiBr, LiCl, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiCl:YbCl3 = 2:1.6:0.8.

[0136] In Example 19, LiBr, LiI, LiF, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:LiF:YbCl3 = 1.9:1:0.1:1.

[0137] In Example 20, LiBr, LiI, LiF, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:LiF:YbCl3 = 1.7:1:0.3:1.

[0138] In Example 21, LiBr, LiI, LiF, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:LiF:YbCl3 = 1.5:1:0.5:1.

[0139] In Example 20, LiBr, LiI, LiF, and YbCl3 were prepared as raw material powders in a molar ratio of LiBr:LiI:LiF:YbCl3 = 1:1:1:1.

[0140] In Examples 2 to 8 and 15 to 18, the mixture of raw powders was fired at 550° C. for 1 hour in a dry argon atmosphere.

[0141] In Examples 9 to 14 and 19 to 22, the mixture of raw powders was fired at 480° C. for 1 hour in a dry argon atmosphere.

[0142] Except for the above, the solid electrolyte materials according to Examples 2 to 22 were obtained in the same manner as in Example 1.

[0143] (Evaluation of ionic conductivity) The ionic conductivities of the solid electrolyte materials according to Examples 2 to 22 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0144] (X-ray diffraction measurement) The X-ray diffraction patterns of the solid electrolyte materials according to Examples 2 to 22 were measured in the same manner as in Example 1.

[0145] 4 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 2 to 22. All of the solid electrolyte materials according to Examples 2 to 22 contained a first crystalline phase. The angles of the clear X-ray diffraction peaks attributed to the observed first crystalline phase are shown in Table 2.

[0146] (Charge / discharge test) Batteries according to Examples 2 to 22 were obtained using the solid electrolyte materials according to Examples 2 to 22 in the same manner as in Example 1. Using the batteries according to Examples 2 to 22, charge / discharge tests were carried out in the same manner as in Example 1. As a result, the batteries according to Examples 2 to 22 were successfully charged and discharged, similar to the battery according to Example 1.

[0147] <Comparative Examples 1 and 2> (Preparation of solid electrolyte materials) In Comparative Example 1, LiCl and YbCl3 were prepared as raw material powders in a molar ratio of LiCl:YbCl3 = 3: 1. The raw material powder mixture was fired at 600°C for 1 hour in a dry argon atmosphere.

[0148] In Comparative Example 2, LiBr and YbBr3 were prepared as raw material powders in a molar ratio of LiBr:YbBr3 = 3: 1. The raw material powder mixture was fired at 550°C for 1 hour in a dry argon atmosphere.

[0149] Except for the above, the solid electrolyte materials according to Comparative Examples 1 and 2 were obtained in the same manner as in Example 1.

[0150] (Evaluation of ionic conductivity) The ionic conductivities of the solid electrolyte materials according to Comparative Examples 1 and 2 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0151] (X-ray diffraction measurement) The X-ray diffraction patterns of the solid electrolyte materials according to Comparative Examples 1 and 2 were measured in the same manner as in Example 1.

[0152] 4 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Comparative Examples 1 and 2. The solid electrolyte material according to Comparative Example 2 contained a first crystalline phase. The solid electrolyte material according to Comparative Example 1 contained an orthorhombic crystalline phase. The angles of the clear X-ray diffraction peaks derived from the observed first crystalline phase are shown in Table 2.

[0153] The compositions of the solid electrolyte materials of the examples and comparative examples are shown in Table 1. The values ​​corresponding to a, x, y, and z in composition formula (1) are also shown in Table 1.

[0154] [Table 1]

[0155] [Table 2]

[0156] <Consideration> The solid electrolyte materials according to Examples 1 to 22 exhibited a thermal conductivity of 5.0×10 -5 It has high lithium ion conductivity of over S / cm.

[0157] As is clear from a comparison of Examples 1 to 22 with Comparative Examples 1 and 2, when the solid electrolyte material is represented by composition formula (1) and X is at least two selected from the group consisting of F, Cl, Br, and I, the solid electrolyte has significantly higher ionic conductivity than when X is composed of a single element. This is thought to be because when X is at least two selected from the group consisting of F, Cl, Br, and I, paths for lithium ions to diffuse within the crystal lattice are more easily formed.

[0158] The solid electrolyte materials according to Examples 1 to 22 have a first crystalline phase. Materials having the first crystalline phase are likely to exhibit high lithium ion conductivity because paths for lithium ions to diffuse are easily formed within the crystal lattice.

[0159] As is clear from comparing Examples 1 to 8 with Comparative Examples 1 and 2, when the value of x is greater than 0 (or 0.75 or greater) and less than 6 (or 5 or less), the solid electrolyte material has high ionic conductivity. This is thought to be because paths for lithium ion diffusion are easily formed within the crystal lattice. In particular, when the value of x is equal to 0, the solid electrolyte material has an orthorhombic crystalline phase. However, when the value of x is 0.75 or greater, the solid electrolyte material has a monoclinic crystalline phase (i.e., the first crystalline phase), which makes it easy to exhibit high lithium ion conductivity. Furthermore, as is clear from comparing Examples 1 to 6 with Examples 7 and 8, when the value of x is greater than 0 and 3 or less, the solid electrolyte material has higher ionic conductivity. This is thought to be because the size of the YbX6 octahedra in the crystal lattice is optimized, making it easier to form lithium ion conduction paths. In addition, when the value of x is 1.5 or greater and 3 or less, the solid electrolyte material has even higher ionic conductivity. This is thought to be because the size of the YbX6 octahedra is further optimized, making it much easier to form lithium ion conduction paths.

[0160] As is clear from Examples 1 to 14, when the value of y is 0 or more and 2 or less, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for lithium ion diffusion are easily formed. In addition, as is clear from comparing Examples 9 to 12 with Examples 13 and 14, when the value of y is 0.5 or more and 1 or less, the solid electrolyte material has higher ionic conductivity. This is thought to be because a first crystalline phase having high lithium ion conductivity is easily formed.

[0161] As is clear from Examples 4 and 15 to 18, when the value of a is 0.8 or more and 1.2 or less, the solid electrolyte material has high ionic conductivity. This is thought to be because a first crystal phase with high lithium ion conductivity is easily formed. Furthermore, as is clear from comparing Examples 4 and 17 to 18 with Examples 15 and 16, when the value of a is 0.8 or more and 1 or less, the solid electrolyte material has even higher ionic conductivity. This is thought to be because the amount ratio of Li, which is the ion-conducting carrier, and Yb, which forms the crystal lattice framework (i.e., the ion-conducting path), is in an optimal relationship. In particular, when the value of a is 1, the solid electrolyte material has significantly higher ionic conductivity.

[0162] As is clear from Examples 11 and 19 to 22, when the value of z is 0 or more and 1 or less, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for lithium ions to diffuse are easily formed. However, the smaller the value of z, the higher the ionic conductivity of the solid electrolyte material tends to be. This is thought to be because the presence of F in the crystal lattice strongly bonds with Li, inhibiting ionic conduction.

[0163] All the batteries according to Examples 1 to 22 were charged and discharged at room temperature.

[0164] The solid electrolyte materials according to Examples 1 to 22 did not contain sulfur, and therefore did not generate hydrogen sulfide.

[0165] As described above, the solid electrolyte material according to the present disclosure is suitable for providing a battery that has high lithium ion conductivity near room temperature and can be charged and discharged well. [Industrial Applicability]

[0166] 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]

[0167] 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

Claims

1. consisting of Li, Yb, and X; X includes Cl, Br, and I; Represented by the following composition formula (1): Li 6-3a Yb a Cl 6-xyz Br x I y F z ... (1) Here, the following five formulas: 0.5≦a≦1.5, 0<x<6, 0<y≦3, 0≦z≦2, and 0<x+y+z<6 is satisfied, Solid electrolyte material.

2. The formula: 0.8≦a≦1.2 is satisfied; The solid electrolyte material according to claim 1 .

3. The formula: 0.8≦a≦1.1 is satisfied; The solid electrolyte material according to claim 2 .

4. The formula: 0.8≦a≦1 is satisfied; The solid electrolyte material according to claim 3 .

5. The formula: 0<x≦4 is satisfied; The solid electrolyte material according to claim 1 .

6. The formula: 0<x≦3 is satisfied; The solid electrolyte material according to claim 5 .

7. The mathematical formula: 0<y≦2 is satisfied. The solid electrolyte material according to claim 1 .

8. The formula: 0<y≦1.5 is satisfied; The solid electrolyte material according to claim 1 .

9. The mathematical formula: 0<y≦1 is satisfied. The solid electrolyte material according to claim 8.

10. The mathematical formula: 0≦z≦1 is satisfied. The solid electrolyte material according to claim 1 .

11. In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material using Cu-Kα radiation, At least two peaks are present in the diffraction angle 2θ range of 26.0° or more and 35.0° or less, and At least one peak exists in the diffraction angle 2θ range of 13.0° or more and 17.0° or less. The solid electrolyte material according to claim 1 .

12. Contains a crystalline phase attributed to monoclinic crystals, The solid electrolyte material according to claim 1 .

13. 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 any one of claims 1 to 12. battery.

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