Solid electrolyte material and battery using the same

Abstract

A solid electrolyte material according to the present invention comprises Li, M1, M2, and X, wherein: M1 is at least two elements selected from the group consisting of Ca, Mg, and Zn; M2 is at least one element selected from the group consisting of Y, Gd, and Sm; and X is at least one element selected from the group consisting of F, Cl, Br, and I.

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.

[0003] Patent Document 2 discloses a solid electrolyte material represented by the composition formula Li 6-3z Y z X6 (0 < z < 2, X = Cl or Br).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a solid electrolyte material having high lithium ion conductivity.

Means for Solving the Problems

[0006] The solid electrolyte material of the present disclosure comprises Li, M1, M2, and X, where M1 is at least two selected from the group consisting of Ca, Mg, and Zn, M2 is at least one selected from the group consisting of Y, Gd, and Sm, and X is at least one selected from the group consisting of F, Cl, Br, and I.

Effects of the Invention

[0007] The present disclosure provides a solid electrolyte material with high lithium ion conductivity. [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 from the AC impedance measurement results 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 18. [Figure 5] FIG. 5 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 19 to 37. [Figure 6] FIG. 6 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.

[0010] (First embodiment) The solid electrolyte material according to the first embodiment is composed of Li, M1, M2, and X. M1 is at least two selected from the group consisting of Ca, Mg, and Zn. M2 is at least one selected from the group consisting of Y, Gd, and Sm. X is at least one selected from the group consisting of F, Cl, Br, and I.

[0011] The solid electrolyte material according to the first embodiment has high lithium ion conductivity. Here, high lithium ion conductivity is, for example, 1 mS / cm or more at around room temperature. That is, the solid electrolyte material according to the first embodiment can have ion conductivity of, for example, 1 mS / 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 desirably contains substantially no sulfur. The term "substantially no sulfur" used herein means that the solid electrolyte material does not contain sulfur as a constituent element, except for sulfur that is 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 desirably contains no sulfur. 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.

[0015] In order to increase the ionic conductivity of the solid electrolyte material, M1 may be Ca and Mg, or may be Ca and Zn.

[0016] M2 may contain Y to enhance the ionic conductivity of the solid electrolyte material.

[0017] To increase the ionic conductivity of the solid electrolyte material, X may be at least one selected from the group consisting of Cl and Br.

[0018] The solid electrolyte material according to the first embodiment may be a material represented by the following compositional formula (1). Li 3-2a-3b (Ca 1-x M1′ x ) a (Y 1-y M2′ y ) 1+b Br 6-z Cl z ···(1) Here, M1′ is at least one selected from the group consisting of Zn and Mg, M2′ is at least one selected from the group consisting of Gd and Sm, The following four mathematical formulas: 0 < a ≤ 0.3, 0 ≤ b ≤ 0.1, 0 < x ≤ 0.5, 0 ≤ y ≤ 0.9, and 0 ≤ z ≤ 6 are satisfied. The material represented by the compositional formula (1) has high ionic conductivity.

[0019] To increase the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the mathematical formula: 3 ≤ z ≤ 4.5 may be satisfied.

[0020] The upper and lower limit values of the range of a in the compositional formula (1) may be defined by any combination selected from the numerical values of greater than 0 (i.e., 0 < a), 0.05, 0.1, 0.15, 0.2, and 0.3.

[0021] The upper and lower limit values of the range of b in the compositional formula (1) may be defined by any combination selected from the numerical values of 0, 0.05, and 0.1.

[0022] The upper and lower limit values of the range of x in the compositional formula (1) may be defined by any combination selected from numerical values greater than 0 (i.e., 0 < x), 0.1, 0.2, 0.3, and 0.5.

[0023] 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 0, 0.1, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9.

[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 3, 3.5, 4, and 4.5.

[0025] The X-ray diffraction pattern of the solid electrolyte material in the first embodiment can be obtained by X-ray diffraction measurement using the θ-2θ method with Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å, i.e., wavelengths 0.15405 nm and 0.15444 nm). In the obtained X-ray diffraction pattern, a first peak may be present in the range of diffraction angle 2θ of 30.0° or more and 31.0° or less, and a second peak may be present in the range of diffraction angle 2θ of 39.0° or more and 40.3° or less. Further, a third peak may be present in the range of diffraction angle 2θ of 15.0° or more and 15.7° or less, a fourth peak may be present in the range of diffraction angle 2θ of 16.3° or more and 17.1° or less, and a fifth peak may be present in the range of diffraction angle 2θ of 46.6° or more and 48.1° or less. The crystal phase having these peaks is called the first crystal phase. The solid electrolyte material containing the first crystal phase has high ionic conductivity.

[0026] The first crystal phase is attributed to the trigonal crystal. The "trigonal crystal" in the present disclosure means a crystal phase having a crystal structure similar to Li3ErCl6 disclosed in ICSD (Inorganic Crystal Structure Database) Collection Code 50151 and having an X-ray diffraction pattern peculiar to this structure. In the present disclosure, "having a similar crystal structure" means being classified into the same space group and having a similar atomic arrangement structure, and does not limit the lattice constant.

[0027] 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 peak outside the range of the diffraction angle 2θ described above. The second crystalline phase may be interposed between the first crystalline phases.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment is produced, for example, by the following method.

[0032] Raw material powders are prepared and mixed to have a desired composition. The raw material powders may be, for example, halides.

[0033] As an example, if the desired composition is Li 2.6 Ca 0.18 Zn 0.02 Y 0.3 Gd 0.7 Br 2.5 Cl 3.5 In this case, LiCl raw material powder, LiBr raw material powder, CaBr2 raw material powder, ZnBr2 raw material powder, YBr3 raw material powder, and GdCl3 raw material powder (i.e., raw material powders of six types of halides) are mixed to a molar ratio of approximately LiCl:LiBr:CaBr2:ZnBr2:YBr3:GdCl3=1.4:1.2:0.18:0.02:0.3:0.7. The raw material powders may be mixed at a molar ratio adjusted in advance to offset composition changes that may occur in the synthesis process.

[0034] The mixture of raw material powders is fired in an inert gas atmosphere to react with each other and obtain a reactant. Examples of inert gases include helium, nitrogen, or argon. The firing may be performed in a vacuum. In the firing process, the mixture of raw material powders may be placed in a container (e.g., a crucible or a vacuum sealed tube) and fired in a heating furnace.

[0035] Alternatively, the raw material powders may be mechanochemically reacted with each other in a mixing device such as a planetary ball mill to obtain a reactant. That is, the raw material powders may be mixed and reacted using a mechanochemical milling method. The reactant thus obtained may be further calcined in an inert gas atmosphere or in vacuum.

[0036] By these methods, the solid electrolyte material according to the first embodiment can be obtained.

[0037] (Second embodiment) The second embodiment will be described below. The matters described in the first embodiment may be omitted as appropriate.

[0038] In the second embodiment, an electrochemical device will be described that uses the solid electrolyte material according to the first embodiment. As the electrochemical device according to the second embodiment, a battery will be described below.

[0039] 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.

[0040] 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.

[0041] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0042] 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.

[0043] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0044] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0045] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0046] The solid electrolyte particles 100 are 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 in the largest amount in terms of molar ratio is 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.

[0047] 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).

[0048] 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.

[0049] In this disclosure, the notation "(A, B, C)" in a chemical formula means "at least one selected from the group consisting of A, B, and C." The same applies to other elements.

[0050] The positive electrode active material particles 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median diameter of 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 100 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.

[0051] 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.

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

[0053] 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.

[0054] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may be a solid electrolyte layer.

[0055] The electrolyte layer 202 may contain the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may be made of only the solid electrolyte material according to the first embodiment. Alternatively, the electrolyte layer 202 may be made of only a solid electrolyte material different from the solid electrolyte material according to the first embodiment.

[0056] 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.

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

[0058] The electrolyte layer 202 may contain 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] As mentioned above, the second solid electrolyte material may be a halide solid electrolyte.

[0068] 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.

[0069] The second solid electrolyte material may be a sulfide solid electrolyte.

[0070] 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.

[0071] The second solid electrolyte material may be an oxide solid electrolyte.

[0072] 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 12or a garnet-type solid electrolyte such as an element substitution product thereof; or (v) Li3PO4 or its N-substituted derivatives is.

[0073] The second solid electrolyte material may be an organic polymer solid electrolyte.

[0074] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds. The polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt, thereby further increasing ionic conductivity.

[0075] 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.

[0076] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0077] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] The ionic liquid may contain a lithium salt.

[0084] 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.

[0085] 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.

[0086] At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive additive to enhance electronic conductivity.

[0087] 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 To reduce costs, the above-mentioned conductive additive (i) or (ii) may be used.

[0088] 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.

[0089] 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]

[0090] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0091] 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 LiCl, LiBr, CaBr2, ZnBr2, YBr3, and GdCl3 were prepared in a molar ratio of LiCl:LiBr:CaBr2:ZnBr2:YBr3:GdCl3 = 1.4:1.2:0.18:0.02:0.3:0.7. These raw material powders were ground and mixed in an agate mortar. The resulting mixture was placed in an alumina crucible and fired at 500°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 contained Li 2.6 Ca 0.18 Zn 0.02 Y 0.3 Gd 0.7 Br 2.5 Cl 3.5 The composition was represented by the formula:

[0092] (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.

[0093] 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.

[0094] The ionic conductivity of the solid electrolyte material according to Example 1 was evaluated using a pressure molding die 300 shown in FIG. 2 as follows.

[0095] In a dry argon atmosphere, powder 101 of the solid electrolyte material according to Example 1 was filled into a pressure molding die 300. Inside the pressure molding die 300, a pressure of 360 MPa was applied to powder 101 of the solid electrolyte material according to Example 1 using upper punch 301 and lower punch 303.

[0096] 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.

[0097] FIG. 3 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the solid electrolyte material according to Example 1.

[0098] In Fig. 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 ion conduction of the solid electrolyte material according to Example 1. The real value is indicated by the arrow R SE Using 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 (equal to the cross-sectional area of ​​the hollow portion of the frame mold 302 in FIG. 2), and R SE represents the resistance value of the solid electrolyte material in impedance measurement, and t represents the thickness of the solid electrolyte material (i.e., the thickness of the layer formed from the powder 101 of the solid electrolyte material in FIG. 2).

[0099] The ionic conductivity of the solid electrolyte material according to Example 1 measured at 25° C. was 2.49 mS / cm.

[0100] (X-ray diffraction measurement) FIG. 4 is a graph showing the X-ray diffraction pattern of the solid electrolyte material according to Example 1.

[0101] The X-ray diffraction pattern of the solid electrolyte material of Example 1 was measured by the θ-2θ method using an X-ray diffractometer (MiniFlex600, Rigaku Co., Ltd.) in a dry environment with a dew point of −50° C. or less. Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) was used as the X-ray source.

[0102] In the X-ray diffraction pattern of the solid electrolyte material according to Example 1, peaks were present at 30.25° (i.e., the first peak) and 39.37° (i.e., the second peak). Furthermore, peaks were also present at 15.24° (i.e., the third peak), 16.62° (i.e., the fourth peak), and 47.05° (i.e., the fifth peak). Therefore, the solid electrolyte material according to the first embodiment contained the first crystalline phase (i.e., trigonal).

[0103] (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.

[0104] In an insulating cylinder having an inner diameter of 9.5 mm, the solid electrolyte material (80 mg) according to Example 1 and the above mixture (10 mg) were stacked in this order. A pressure of 720 MPa was applied to the resulting stack to form a solid electrolyte layer and a first electrode. The solid electrolyte layer had a thickness of 400 μm.

[0105] 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 second electrode.

[0106] Next, current collectors made of stainless steel were attached to the first electrode and the second electrode, and current collecting leads were attached to the current collectors.

[0107] 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.

[0108] (Charge / discharge test) 6 is a graph showing the initial discharge characteristics of the battery according to Example 1. The initial discharge characteristics were measured as follows.

[0109] The battery according to Example 1 was placed in a thermostatic chamber at 25°C.

[0110] 76μA / 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.

[0111] Next, 76 μA / cm 2 The battery according to Example 1 was discharged at a current density of 0.1 V until a voltage of 1.88 V was reached.

[0112] As a result of the charge-discharge test, the battery according to Example 1 had an initial discharge capacity of 0.73 mAh.

[0113] <Examples 2 to 37> (Preparation of solid electrolyte materials) Except for the types and molar ratios of the raw material powders, the solid electrolyte materials of Examples 2 to 37 were obtained in the same manner as in Example 1. The types and molar ratios of the raw material powders are shown in Table 1.

[0114] The compositions of the solid electrolyte materials according to Examples 2 to 37 are shown in Table 2. The values ​​corresponding to a, b, x, y, and z in the composition formula (1), as well as the elemental species of M1 and M2, are shown in Table 2.

[0115] (Evaluation of ionic conductivity) The ionic conductivities of the solid electrolyte materials according to Examples 2 to 37 were measured in the same manner as in Example 1. The measurement results are shown in Table 2.

[0116] (X-ray diffraction measurement) The X-ray diffraction patterns of the solid electrolyte materials according to Examples 2 to 37 were measured in the same manner as in Example 1.

[0117] Fig. 4 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 1 to 18. Fig. 5 is a graph showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 19 to 37. The angles of the observed X-ray diffraction peaks are shown in Table 3. As shown in Figs. 4 and 5, the solid electrolyte materials according to Examples 1 to 37 all contained a first crystalline phase.

[0118] (Charge / discharge test) Batteries according to Examples 2 to 37 were obtained using the solid electrolyte materials according to Examples 2 to 37 in the same manner as in Example 1. Using the batteries according to Examples 2 to 37, charge / discharge tests were carried out in the same manner as in Example 1. As a result, the batteries according to Examples 2 to 37 were successfully charged and discharged, similar to the battery according to Example 1.

[0119] <Comparative Examples 1 and 2> (Preparation of solid electrolyte materials) Except for the types and molar ratios of the raw material powders, the solid electrolyte materials of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1. The types and molar ratios of the raw material powders are shown in Table 1.

[0120] The compositions of the solid electrolyte materials according to Comparative Examples 1 and 2 are shown in Table 2. The values ​​corresponding to a, b, x, y, and z in composition formula (1), as well as the elemental species of M1 and M2, are shown in Table 2.

[0121] (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 2.

[0122] [Table 1]

[0123] [Table 2]

[0124] [Table 3]

[0125] <Consideration> The solid electrolyte materials according to Examples 1 to 37 have high lithium ion conductivity of 1 mS / cm or more at around room temperature.

[0126] As is clear from a comparison of Examples 1 to 37 with Comparative Examples 1 and 2, when the solid electrolyte material is composed of Li, M1, M2, and X, where M1 is at least two selected from the group consisting of Ca, Mg, and Zn, M2 is at least one selected from the group consisting of Y, Gd, and Sm, and X is at least one selected from the group consisting of F, Cl, Br, and I, the solid electrolyte material has higher ionic conductivity than when it does not have the above configuration. This is thought to be because paths for lithium ion diffusion are more easily formed.

[0127] As is clear from Examples 1 to 16 and 31 to 37, when M1 is Ca or Zn, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for lithium ion diffusion are easily formed.

[0128] In the composition formula (1), when the value of a is greater than 0 and less than or equal to 0.3, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for the diffusion of lithium ions are easily formed.

[0129] In the composition formula (1), when the value of b is 0 or more and 0.1 or less, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for the diffusion of lithium ions are easily formed.

[0130] In the composition formula (1), when the value of x is greater than 0 and less than or equal to 0.5, the solid electrolyte material has high ionic conductivity. This is thought to be because paths for the diffusion of lithium ions are easily formed.

[0131] In the composition formula (1), when the value of y is 0 or more and 0.9 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.

[0132] As is clear from Examples 17 to 30, when M1 is Ca and Mg, the solid electrolyte material has high ionic conductivity.

[0133] Furthermore, in composition formula (1), if the value of z is 3 or more and 4.5 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.

[0134] 4 and 5, when the first, second, third, fourth, and fifth peaks are present in the X-ray diffraction patterns of the solid electrolyte materials according to Examples 1 to 37, the solid electrolyte materials have high ionic conductivity. This is thought to be because paths for lithium ion diffusion are more easily formed.

[0135] In all Examples 1 to 37, the batteries were charged and discharged at room temperature.

[0136] The solid electrolyte materials according to Examples 1 to 37 do not contain sulfur and therefore do not generate hydrogen sulfide.

[0137] As described above, the solid electrolyte material according to the present disclosure is suitable for providing a battery that has high lithium ion conductivity and can be charged and discharged well. [Industrial Applicability]

[0138] The solid electrolyte material of the present disclosure is used, for example, in an all-solid-state lithium-ion secondary battery. [Explanation of symbols]

[0139] 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. Li, M1, M2, and X; M1 is at least two selected from the group consisting of Ca, Mg, and Zn; M2 is at least one selected from the group consisting of Y, Gd, and Sm; X is at least one selected from the group consisting of F, Cl, Br, and I; In the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation, The first peak exists in the range of the diffraction angle 2θ of 30.0° or more and 31.0° or less, and A second peak exists in the diffraction angle 2θ range of 39.0° or more and 40.3° or less. Solid electrolyte material.

2. A compound comprising Li, M1, M2, and X; M1 is at least two selected from the group consisting of Ca, Mg, and Zn; M2 is at least one selected from the group consisting of Y, Gd, and Sm; X is at least one selected from the group consisting of F, Cl, Br, and I; Represented by the following composition formula (1): Li 3-2a-3b (Ca 1-x M1' x ) a (Y 1-y M2' y ) 1+b Br 6-z Cl z ... (1) where: M1′ is at least one selected from the group consisting of Zn and Mg; M2' is at least one selected from the group consisting of Gd and Sm; The following four formulas: 0<a≦0.3, 0≦b≦0.1, 0<x≦0.5, 0≦y≦0.9, and 0≦z≦6 is satisfied, Solid electrolyte material.

3. In the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation, a third peak exists in the diffraction angle 2θ range of 15.0° or more and 15.7° or less; A fourth peak exists in the diffraction angle 2θ range of 16.3° or more and 17.1° or less, and A fifth peak exists in the diffraction angle 2θ range of 46.6° or more and 48.1° or less. The solid electrolyte material according to claim 1 .

4. M1 is Ca and Mg, or Ca and Zn; The solid electrolyte material according to claim 1 .

5. X is at least one selected from the group consisting of Cl and Br; The solid electrolyte material according to claim 1 .

6. 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 5. battery.

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