Solid electrolyte material and battery using the same

Abstract

A solid electrolyte material according to the present disclosure contains Li, M1, M2, and X. M1 is at least one element selected from the group consisting of the group 2 elements and the group 12 elements. M2 is at least three elements selected from the group consisting of rare earth elements and the group 13 elements. X is at least one element selected from the group consisting of F, Cl, Br, and I. A battery 1000 according to the present disclosure is provided with: a positive electrode 201; a negative electrode 203; and an electrolyte layer 202 disposed between the positive electrode 201 and the negative electrode 203. At least one selected from the group consisting of the positive electrode 201, the negative electrode 203, and the electrolyte layer 202, contains the solid electrolyte material according to the present disclosure.

Description

Technical Field

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

Background 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

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present disclosure is to provide a novel solid electrolyte material having lithium ion conductivity.

Means for Solving the Problems

[0007] The solid electrolyte material of the present disclosure comprises Li, M1, M2, and X, where M1 is at least one element selected from the group consisting of Group 2 elements and Group 12 elements, M2 is at least three elements selected from the group consisting of rare earth elements and Group 13 elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I. [Effects of the Invention]

[0008] The present disclosure provides a novel solid electrolyte material that has lithium ion conductivity. [Brief explanation of the drawings]

[0009] [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 AC impedance measurement of the solid electrolyte material of Example 1. [Figure 4] FIG. 4 is a graph showing the X-ray diffraction pattern of the solid electrolyte material of Example 1. [Figure 5] FIG. 5 is a graph showing the initial discharge characteristics of the battery of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] (First embodiment) The solid electrolyte material according to the first embodiment includes Li, M1, M2, and X. M1 is at least one element selected from the group consisting of Group 2 elements and Group 12 elements. M2 is at least three elements selected from the group consisting of rare earth elements and Group 13 elements. X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0012] The solid electrolyte material according to the first embodiment is a novel solid electrolyte material having lithium ion conductivity. The solid electrolyte material according to the first embodiment has a lithium ion conductivity of, for example, 1.0×10 -3 It may have an ionic conductivity of 5 S / cm or more.

[0013] 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.

[0014] The solid electrolyte material according to the first embodiment desirably does not contain 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.

[0015] In order to improve the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist essentially of Li, M1, M2, and X. Here, "the solid electrolyte material according to the first embodiment consists essentially of Li, M1, M2, and X" means that the molar ratio (i.e., molar fraction) of the total amount of substance of Li, M1, M2, and X to the total amount of substance of all elements constituting the solid electrolyte material according to the first embodiment is 90% or more. As an example, the molar ratio may be 95% or more. The solid electrolyte material according to the first embodiment may consist only of Li, M1, M2, and X.

[0016] 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.

[0017] 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 a diffraction angle 2θ range of 14.0° to 18.0°, and at least one peak in a diffraction angle 2θ range of 29.0° to 32.0°. The crystalline phase having these peaks is called the first crystalline phase. In a solid electrolyte material containing the first crystalline phase, paths for lithium ion diffusion within the crystal are easily formed. This improves the ionic conductivity of the solid electrolyte material. The solid electrolyte material according to the first embodiment may contain the first crystalline phase.

[0018] The first crystalline phase is classified as a trigonal crystal. In this disclosure, "trigonal crystal" refers to a crystalline phase having a crystalline structure similar to that of Li3ErCl6 disclosed in ICSD (Inorganic Crystal Structure Database) Collection Code 50151 and having an X-ray diffraction pattern specific to this structure. Here, "having a similar crystalline structure" means being classified into the same space group and having a similar atomic arrangement structure, but does not limit the lattice constant.

[0019] To improve the ionic conductivity of the solid electrolyte material, M1 may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. M2 may be Y, Gd, and Sm. X may be at least one selected from the group consisting of Cl and Br.

[0020] To further improve the ionic conductivity of the solid electrolyte material, M1 may be Ca.

[0021] The solid electrolyte material according to the first embodiment may be a material represented by the following composition formula (1). Li 3-2a M1 a Y 1-b-c Gd b Smc Br 6-d Cl d ···(1) Here, the following 5 two formulas: 0 < a ≤ 0.2, 0 < b, 0 < c, 0 < b + c < 1, and 0 ≤ d ≤ 6 are satisfied. According to the material represented by the compositional formula (1), the ionic conductivity of the solid electrolyte material can be further improved.

[0022] In order to further improve the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the formula: a ≤ 0.15 may be satisfied.

[0023] In order to further improve the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the formula: d ≤ 4.5 may be satisfied.

[0024] In order to further improve the ionic conductivity of the solid electrolyte material, in the compositional formula (1), the formula: c ≤ 0.325 may be satisfied.

[0025] 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), 0.075, 0.1, 0.15, and 0.2.

[0026] 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 greater than 0 (i.e., 0 < b), 0.1, 0.2, 0.3, 0.38, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.9, and less than 1 (i.e., b < 1).

[0027] The upper and lower limit values of the range of c in the compositional formula (1) may be defined by any combination selected from values greater than 0 (i.e., 0 < c), 0.02, 0.05, 0.1, 0.125, 0.15, 0.2, 0.225, 0.25, 0.3, 0.325, 0.35, and less than 1 (i.e., c < 1).

[0028] The upper and lower limit values of the range of d in the compositional formula (1) may be defined by any combination selected from the values 3, 3.5, 4, 4.5, and 5.

[0029] The weighted average value of the ionic radii of Y, Gd, and Sm based on the content rate of each element is defined as R α and the weighted average value of the ionic radii of Cl and Br based on the content rate of each element is defined as R β R α divided by R β is defined as R. At this time, R may be 0.490 or more and 0.505 or less. When R is within this range, the ionic conductivity of the solid electrolyte material is improved. Desirably, R may be 0.4965 or more and 0.505 or less. When R is within this range, the ionic conductivity of the solid electrolyte material is further improved. Here, the "ionic radius" in the present disclosure means the 6 - coordinate ionic radius described in Non - Patent Document 1 (R.D. Shannon, Acta Cryst., A32, 751 (1976)). The ionic radii of Y 3+ , Gd 3+ , Sm 3+ , Cl - , and Br - are 0.900 Å, 0.938 Å, 0.958 Å, 1.81 Å, and 1.96 Å, respectively.

[0030] For example, in the compositional formula (1), R is calculated by the following mathematical formula (1). R α and R β are calculated by the following mathematical formulas (2) and (3), respectively. R Y is the ionic radius of Y, R Gd is the ionic radius of Gd, R Sm is the ionic radius of Sm, RBr is the ionic radius of Br, R Cl is the ionic radius of Cl.

[0031] R=R α / R β ···(1) R α =R Y ×(1-bc)+R Gd ×b+R Sm ×c ···(2) R β =(R Br ×(6-d)+R Cl ×d) / 6 (3)

[0032] 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 materials are mixed, a peak and a halo are present in the X-ray diffraction pattern.

[0033] 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.

[0034] 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.

[0035] 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 can further improve the ionic conductivity of the solid electrolyte material according to the first embodiment. 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.

[0036] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment is produced, for example, by the following method.

[0037] Two or more halide raw material powders are mixed together to obtain a desired composition.

[0038] As an example, the composition of the desired solid electrolyte material is Li 2.85 Ca 0.075 Y 0.1 Gd 0.8 Sm 0.1 Assume that the starting material is Br3Cl3. In this case, raw material powders of LiBr, CaBr2, YCl3, GdCl3, and SmCl3 are mixed to achieve a molar ratio of approximately LiBr:CaBr2:YCl3:GdCl3:SmCl3 = 2.85:0.075:0.1:0.8:0.1. The raw material powders may be mixed at a molar ratio that is adjusted in advance to offset composition changes that may occur during the synthesis process.

[0039] 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.

[0040] Alternatively, the raw material powders may be mixed and reacted mechanochemically 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.

[0041] By these methods, the solid electrolyte material according to the first embodiment can be obtained.

[0042] (Second embodiment) The second embodiment will be described below, and the matters described in the first embodiment may be omitted.

[0043] In the second embodiment, a battery using the solid electrolyte material according to the first embodiment will be described.

[0044] 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.

[0045] 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.

[0046] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0047] 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.

[0048] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0049] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0050] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0051] 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" means particles in which the component contained most abundantly in terms of molar ratio is the solid electrolyte material according to the first embodiment.

[0052] The solid electrolyte particles 100 may have a median diameter of 0.1 μm or more and 100 μm or less. When the solid electrolyte particles 100 have a median diameter of 0.5 μm or more and 10 μm or less, the ionic conductivity of the solid electrolyte particles 100 can be further improved.

[0053] 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).

[0054] 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.

[0055] 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."

[0056] 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 1000. 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 1000 to operate at a high output.

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

[0058] In order to improve the energy density and output of the battery 1000, 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.

[0059] To improve the energy density and power output of the battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 1000 can operate at high power.

[0066] 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).

[0067] 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.

[0068] 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 1000. 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 1000 to operate at high power.

[0069] 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.

[0070] In order to improve the energy density and output of the battery 1000, 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.

[0071] To improve energy density and output, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0072] 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 improving ionic conductivity, chemical stability, and electrochemical stability.

[0073] As mentioned above, the second solid electrolyte material may be a halide solid electrolyte.

[0074] 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.

[0075] The second solid electrolyte material may be a sulfide solid electrolyte.

[0076] 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.

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

[0078] 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.

[0079] The second solid electrolyte material may be an organic polymer solid electrolyte.

[0080] 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 improving ionic conductivity.

[0081] 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.

[0082] 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 1000.

[0083] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0084] 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.

[0085] 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 / liter or more and 2 mol / liter or less.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The ionic liquid may contain a lithium salt.

[0090] 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.

[0091] 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.

[0092] At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity.

[0093] 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 polymers such as polyaniline, polypyrrole, or polythiophene; To reduce costs, the above-mentioned conductive additive (i) or (ii) may be used.

[0094] Examples of the shape of the battery 1000 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.

[0095] The battery 1000 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]

[0096] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0097] The solid electrolyte material in the examples is represented by the following composition formula (1). Li 3-2a M1 a Y 1-b-c Gd b Sm c Br 6-d Cl d ···(1)

[0098] 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, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3 = 2.85:0.075:0.1:0.8:0.1. 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 of Example 1 was obtained. The solid electrolyte material of Example 1 contained Li 2.85 Ca 0.075 Y0.1 Gd 0.8 Sm 0.1 The solid electrolyte material of Example 1 had a composition represented by Br3Cl3. The R value of this composition was 0.497. The composition of the solid electrolyte material of Example 1 is shown in Table 1. The values ​​corresponding to a, b, c, and d in composition formula (1), the element type of M1, and the R value are shown in Table 2.

[0099] (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.

[0100] 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.

[0101] The ionic conductivity of the solid electrolyte material of Example 1 was evaluated by the following method using the pressure molding die 300 shown in FIG.

[0102] In a dry argon atmosphere, powder 101 of the solid electrolyte material of 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 of Example 1 using upper punch 301 and lower punch 303.

[0103] 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.

[0104] FIG. 3 is a graph showing a Cole-Cole plot obtained by measuring the impedance of the solid electrolyte material of Example 1.

[0105] 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. SE Using the resistance value, the ionic conductivity was calculated based on the following formula (4).

[0106] σ=(R SE ×S / t) -1 ···(4)

[0107] 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).

[0108] The ionic conductivity of the solid electrolyte material of Example 1 measured at 25°C was 4.21 × 10 -3 The measurement results are shown in Table 2.

[0109] (X-ray diffraction measurement) FIG. 4 is a graph showing the X-ray diffraction pattern of the solid electrolyte material of Example 1.

[0110] 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.

[0111] In the X-ray diffraction pattern of the solid electrolyte material of Example 1, one or more peaks were present in the range of 29.0° to 32.0° and two peaks were present in the range of 14.0° to 18.0°. Therefore, the solid electrolyte material of Example 1 contained a crystalline phase belonging to a trigonal crystal system.

[0112] (Battery construction) In a dry argon atmosphere, the solid electrolyte material of Example 1 and LiCoO2 were prepared in a volume ratio of 30:70. These materials were mixed in a mortar to obtain a mixture.

[0113] In an insulating tube having an inner diameter of 9.5 mm, the solid electrolyte material of Example 1 (80 mg) and the above mixture (10 mg) were laminated in this order. A pressure of 720 MPa was applied to the resulting laminate, forming a solid electrolyte layer made of the solid electrolyte material of Example 1 and a first electrode made of the above mixture. The solid electrolyte layer had a thickness of 400 μm.

[0114] 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.

[0115] 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.

[0116] 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 of Example 1 was obtained.

[0117] (Charge / discharge test) 5 is a graph showing the initial charge / discharge characteristics of the battery of Example 1. The initial charge / discharge characteristics were measured by the following method.

[0118] The battery of Example 1 was placed in a thermostatic chamber at 25°C.

[0119] 75μA / cm 2 The battery of 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.

[0120] Next, 75 μA / cm 2 The battery of Example 1 was discharged at a current density of 1.88 V until a voltage of 1.88 V was reached.

[0121] As a result of the charge-discharge test, the battery of Example 1 had an initial discharge capacity of 0.96 mAh.

[0122] <Examples 2 to 29> (Preparation of solid electrolyte materials) In Example 2, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.35:0.4:0.25.

[0123] In Example 3, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.275:0.6:0.125.

[0124] In Example 4, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.375:0.3:0.325.

[0125] In Example 5, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.3:0.5:0.2.

[0126] In Example 6, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.15:0.7:0.15.

[0127] In Example 7, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.05:0.9:0.05.

[0128] In Example 8, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.1:0.7:0.2.

[0129] In Example 9, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.05:0.8:0.1.

[0130] In Example 10, raw material powders of LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.4:0.55:0.05.

[0131] In Example 11, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=2.35:0.5:0.075:0.5:0.2:0.3.

[0132] In Example 12, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=2.35:0.5:0.075:0.475:0.3:0.225.

[0133] In Example 13, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=2.35:0.5:0.075:0.45:0.4:0.15.

[0134] In Example 14, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=2.35:0.5:0.075:0.4:0.5:0.1.

[0135] In Example 15, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=1.85:1:0.075:0.65:0.1:0.25.

[0136] In Example 16, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=1.85:1:0.075:0.6:0.3:0.1.

[0137] In Example 17, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=1.85:1:0.075:0.05:0.8:0.1.

[0138] In Example 18, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=1.3:1.5:0.1:0.6:0.38:0.02.

[0139] In Example 19, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=0.8:2:0.1:0.6:0.38:0.02.

[0140] In Example 20, LiBr, MgBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:MgBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.1:0.8:0.1.

[0141] In Example 21, LiBr, ZnBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:ZnBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.1:0.8:0.1.

[0142] In Example 22, LiBr, SrBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:SrBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.1:0.8:0.1.

[0143] In Example 23, LiBr, BaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:BaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.1:0.8:0.1.

[0144] In Example 24, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.7:0.15:0.05:0.9:0.05.

[0145] In Example 25, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.6:0.2:0.05:0.9:0.05.

[0146] In Example 26, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3:SmCl3=2.35:0.5:0.075:0.55:0.1:0.35.

[0147] In Example 27, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.8:0.1:0.1.

[0148] In Example 28, LiBr, CaBr2, YCl3, GdCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:GdCl3:SmCl3=2.85:0.075:0.6:0.1:0.3.

[0149] In Example 29, raw material powders of LiBr, LiCl, CaBr2, YCl3, GdCl3, and SmCl3 were prepared in a molar ratio of LiBr:LiCl, CaBr2:YCl3:GdCl3:SmCl3=1.85:1:0.075:0.05:0.65:0.3.

[0150] Except for the above, the solid electrolyte materials of Examples 2 to 29 were obtained in the same manner as in Example 1. The compositions of the solid electrolyte materials of Examples 2 to 29 are shown in Table 1. In addition, the values ​​corresponding to a, b, c, and d in composition formula (1), the element type of M1, and the value of R are shown in Table 2.

[0151] (Evaluation of ionic conductivity) The ionic conductivities of the solid electrolyte materials of Examples 2 to 29 were measured in the same manner as in Example 1. The measurement results are shown in Table 2.

[0152] (X-ray diffraction measurement) The X-ray diffraction patterns of the solid electrolyte materials of Examples 2 to 29 were measured in the same manner as in Example 1. All of the solid electrolyte materials of Examples 2 to 29 contained a crystalline phase belonging to trigonal crystals.

[0153] (Charge / discharge test) The solid electrolyte materials of Examples 2 to 29 were used to obtain batteries of Examples 2 to 29 in the same manner as in Example 1. Using the batteries of Examples 2 to 29, charge / discharge tests were carried out in the same manner as in Example 1. As a result, the batteries of Examples 2 to 29 were successfully charged and discharged, similar to the battery of Example 1.

[0154] <Comparative Examples 1 and 2> (Preparation of solid electrolyte materials) In Comparative Example 1, LiBr, CaBr2, YCl3, and SmCl3 were prepared as raw material powders in a molar ratio of LiBr:CaBr2:YCl3:SmCl3=2.8:0.1:0.8:0.2.

[0155] In Comparative Example 2, raw material powders of LiBr, LiCl, CaBr2, YCl3, and GdCl3 were prepared in a molar ratio of LiBr:LiCl:CaBr2:YCl3:GdCl3=1.8:1:0.1:0.6:0.4.

[0156] Except for the above, the solid electrolyte materials of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1.

[0157] The compositions of the solid electrolyte materials of Comparative Examples 1 and 2 are shown in Table 1. The values ​​corresponding to a, b, c, and d in composition formula (1), the element type of M1, and the value of R are shown in Table 2.

[0158] (Evaluation of ionic conductivity) The ionic conductivities of the solid electrolyte materials of Comparative Examples 1 and 2 were measured in the same manner as in Example 1. The measurement results are shown in Table 2.

[0159] [Table 1]

[0160] [Table 2]

[0161] <Consideration> The solid electrolyte materials of Examples 1 to 29 had a melting point of 1.0 × 10 -3 The lithium ion conductivity was 200 S / cm or more.

[0162] The solid electrolyte materials of Examples 1 to 29 had a crystalline phase belonging to the trigonal crystal system. In the solid electrolyte material having a crystalline phase belonging to the trigonal crystal system, paths for the diffusion of lithium ions are easily formed within the crystal. Therefore, the ionic conductivity of the solid electrolyte material was improved.

[0163] Comparing Examples 1 to 10 and 19 with Comparative Examples 1 and 2 reveals the following. When the solid electrolyte material is represented by composition formula (1) and contains both Gd and Sm in addition to Y, the ionic conductivity is improved compared to when it contains only one of Gd and Sm in addition to Y. When the solid electrolyte material is represented by composition formula (1) and contains both Gd and Sm in addition to Y, a crystalline phase belonging to a trigonal crystal structure is likely to be formed. This is thought to be because paths for the diffusion of lithium ions within the crystal are more likely to be formed.

[0164] As is clear from comparing Examples 1, 22, and 23 with Examples 20 and 23, when M1 was Ca, Sr, or Ba, the ionic conductivity of the solid electrolyte material was further improved. This is thought to be because when the ionic radius of M1 is larger than that of Y, Gd, and Sm, the path for lithium ions to diffuse within the crystal is wider, making it easier to improve ionic conductivity. When the ionic radius of M1 is smaller than that of Y, Gd, and Sm, this is the case when M1 is Mg or Zn. When the ionic radius of M1 is larger than that of Y, Gd, and Sm, this is the case when M1 is Ca, Sr, or Ba. As is clear from comparing Example 1 with Examples 22 and 23, when M1 was Ca, the ionic conductivity of the solid electrolyte material was further improved. This is thought to be because when the ionic radius of M1 is close to the ionic radius of Y, Gd, and Sm, the path for lithium ions to diffuse is appropriately wide, making it easier to improve ionic conductivity.

[0165] As is clear from Examples 7, 24, and 25, when the value of a was greater than 0 and less than or equal to 0.2, the ionic conductivity of the solid electrolyte material was improved. This is thought to be because paths for lithium ions to diffuse within the crystal were easily formed. As is clear from comparing Examples 7 and 24 with Example 25, when the value of a was greater than 0 and less than or equal to 0.15, the ionic conductivity of the solid electrolyte material was further improved. This is thought to be because the amount of lithium ions within the crystal was optimized.

[0166] As is clear from a comparison of Examples 1 to 18 with Example 19, the ionic conductivity of the solid electrolyte material was improved when the value of d was 0 or more and 4.5 or less. This is thought to be because paths for lithium ions to diffuse within the crystals were more easily formed.

[0167] As is clear from a comparison of Examples 11 to 14 with Example 26, the ionic conductivity of the solid electrolyte material was improved when the value of c was greater than 0 and not greater than 0.325. This is thought to be because the size of the crystal lattice was optimized, making it easier to form paths for the diffusion of lithium ions.

[0168] As is clear from a comparison of Examples 1 to 18 with Examples 27 to 29, when R was 0.4900 or more and 0.5050 or less, the ionic conductivity of the solid electrolyte material was further improved. This is thought to be because diffusion paths of an appropriate width for lithium ion conduction were more easily formed within the crystal. As is clear from a comparison of Examples 1, 7 to 9, and 17 with Examples 2 to 6, 10 to 16, and 18, when R was 0.4965 or more and 0.5050 or less, the ionic conductivity of the solid electrolyte material was further improved. This is thought to be because the size of the crystal lattice was optimized, making it easier to form paths for lithium ion diffusion.

[0169] The batteries of Examples 1 to 29 were all charged and discharged at room temperature.

[0170] The solid electrolyte materials of Examples 1 to 29 did not contain sulfur and therefore did not generate hydrogen sulfide.

[0171] As described above, the solid electrolyte material according to the present disclosure is a novel solid electrolyte material having lithium ion conductivity. The solid electrolyte material according to the present disclosure is suitable for providing a battery that can be charged and discharged well. [Industrial Applicability]

[0172] The solid electrolyte material of the present disclosure is used, for example, in batteries (for example, all-solid-state lithium-ion secondary batteries).

Claims

1. Li, M1, M2, and X; M1 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn; M2 is Y, Gd, and Sm; X is at least one selected from the group consisting of Cl and Br; Solid electrolyte material.

2. Contains a crystalline phase that is attributed to trigonal crystals, The solid electrolyte material according to claim 1 .

3. M1 is Ca; The solid electrolyte material according to claim 1 or 2.

4. Represented by the following composition formula (1): Li 3-2a M1 a Y 1-b-c Gd b Sm c Br 6-d Cl d ・・・(1) Here, the following five formulas: 0<a≦0.2, 0<b, 0<c, 0<b+c<1, and 0≦d≦6 is satisfied, The solid electrolyte material according to claim 1 .

5. In the composition formula (1), the mathematical formula: a≦0.15 is satisfied. The solid electrolyte material according to claim 4.

6. In the composition formula (1), the mathematical formula: d≦4.5 is satisfied. The solid electrolyte material according to claim 4 or 5.

7. In the composition formula (1), the mathematical formula: c≦0.325 is satisfied. The solid electrolyte material according to claim 4 .

8. a value obtained by dividing the weighted average value of the ionic radii of Y, Gd, and Sm based on the content of each element by the weighted average value of the ionic radii of Cl and Br based on the content of each element is 0.4900 or more and 0.5050 or less; The solid electrolyte material according to claim 1 .

9. 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 8. battery.

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