Solid electrolyte material, method for producing solid electrolyte material, positive electrode material, and battery

Abstract

A solid electrolyte material is composed of Li, Al, and X. X is an anion including F, and the specific surface area of the solid electrolyte material is 16 m2 / g or more. A method for producing a solid electrolyte material includes a wet grinding step for grinding a mixture containing a raw material composition and a solvent, the raw material composition containing constituent components of the solid electrolyte material. A positive electrode material includes a positive electrode active material coated with a solid electrolyte material.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a solid electrolyte material, a method for manufacturing a solid electrolyte material, a positive electrode material, and a battery. BACKGROUND

[0002] Patent Document 1 discloses an all-solid battery using a sulfide solid electrolyte.

[0003] Patent Document 2 discloses coating the surface of lithium nickel oxide with lithium fluoride.

[0004] PRIOR ART DOCUMENTS

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

[0006] Patent Document 2: Japanese Patent Application Publication No. 2012-84547 SUMMARY

[0007] An object of the present disclosure is to provide a solid electrolyte material that is suitable for lithium ion conduction and that improves contact with other materials.

[0008] The present disclosure provides a solid electrolyte material composed of Li, Al, and X,

[0009] X is an anion containing F,

[0010] The specific surface area of the solid electrolyte material is 16 m 2 / g or more.

[0011] The present disclosure provides a solid electrolyte material that is suitable for lithium ion conduction and that improves contact with other materials. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 FIG. 1 is a cross-sectional view showing a battery 1000 according to Embodiment 1.

[0013] Figure 2 FIG. 3 is a schematic view showing a press molding mold 300 used for evaluating the ion conductivity of a solid electrolyte material.

[0014] Figure 3 FIG. 4 is a graph showing a Cole-Cole plot of a solid electrolyte material of Example 1 obtained by impedance measurement.

[0015] Figure 4 FIG. 5 is a graph showing the initial discharge characteristics of a battery of Example 1. DETAILED DESCRIPTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0017] (First Embodiment)

[0018] The solid electrolyte material of the first embodiment is composed of Li, Al, and X. X is an anion containing F. The specific surface area of the solid electrolyte material of the first embodiment is greater than 16 m 2 / g. Herein, the specific surface area of the solid electrolyte material in the present disclosure refers to the specific surface area calculated by the BET (Brunauer Emmett Teller) method.

[0019] "composed of Li, Al, and X" means that no element other than Li, Al, and X is actively used in the raw material of the solid electrolyte material. It is permissible for the solid electrolyte material to contain unavoidable impurities. Examples of the element contained as the unavoidable impurities are hydrogen, oxygen, or nitrogen. These elements exist in the raw material powder of the solid electrolyte material, or in the atmosphere used for manufacturing or storing the solid electrolyte material. There are also cases where the container used for synthesizing the solid electrolyte material mixes impurities into the solid electrolyte material.

[0020] The solid electrolyte material of the first embodiment is suitable for lithium ion conduction, and has good contactability with other materials. Therefore, the solid electrolyte material of the first embodiment can reduce the resistance at the interface with other materials. The other materials are, for example, active materials.

[0021] Generally, as the active material used in a lithium ion secondary battery, a polycrystal is used. The surface of the active material is not flat, but has a small groove or a pit, or the like. In the case where the surface of the active material is coated with the solid electrolyte, in order to reduce the resistance of the battery, it is desirable to improve the contactability of the active material with the solid electrolyte. For this purpose, it is necessary to deform the solid electrolyte by compression or the like so as to match the concave-convex shape of the active material. However, in the case where the surface of the solid electrolyte is flat and the particle diameter of the solid electrolyte is large, the pressure at the time of pressing is concentrated on the convex portion of the surface of the active material. As a result, good contactability of the active material with the solid electrolyte is not obtained in the inside of the concave portion. On the other hand, in the case where the particle diameter of the solid electrolyte is smaller than the concave portion of the surface of the active material, the pressure is applied in a state where the solid electrolyte enters the concave portion, and thus good contactability of the active material with the solid electrolyte can be obtained. In addition, in the case where the surface of the solid electrolyte has a concave-convex shape, the solid electrolyte easily enters the inside of the concave portion of the surface of the active material compared to the case where the surface is flat, and thus good contactability of the active material with the solid electrolyte is easily achieved. The small particle diameter and the surface having a concave-convex shape mean that the specific surface area is large. That is, the solid electrolyte having a large specific surface area easily achieves good contactability with the active material. As a result, it is possible to reduce the resistance of the battery, and for example, it is possible to improve the charge-discharge characteristics of the battery.

[0022] The solid electrolyte material of the first embodiment can be used, for example, to obtain a battery having excellent charge / discharge characteristics. Examples of the battery include a solid battery. The solid electrolyte material of the first embodiment is suitable as a material for a solid battery. The solid battery can be a primary battery or a secondary battery. The solid battery can also be an all-solid battery.

[0023] The solid electrolyte material of the first embodiment preferably does not contain sulfur. A solid electrolyte material not containing sulfur does not generate hydrogen sulfide even when exposed to the atmosphere, and thus has excellent safety. The sulfide solid electrolyte disclosed in Patent Document 1 generates hydrogen sulfide when exposed to the atmosphere.

[0024] The solid electrolyte material of the first embodiment can have high oxidation resistance because it contains F. This is because F has a high redox potential. On the other hand, because F has high electronegativity, the bonding between F and Li is strong. As a result, the lithium ion conductivity of a solid electrolyte material that generally contains Li and F is low. For example, the electrical conductivity of LiF disclosed in Patent Document 2 is so high that it cannot be measured by an alternating current impedance method. In contrast, the solid electrolyte material of the first embodiment contains Al in addition to Li and F, and thus, for example, can have an ion conductivity of 1.2 x 10 -10 S / cm or more. This value is a sufficient conductivity for lithium ions to move over a very short distance. For example, in the case where the surface of an active material is coated with the solid electrolyte material of the first embodiment, lithium ions can permeate the layer of the solid electrolyte material.

[0025] The specific surface area of the solid electrolyte material of the first embodiment can be less than 100 m 2 / g, can be less than 60 m 2 / g, and can be 44.6 m 2 / g or less. According to such a configuration, the above-described effects can be sufficiently obtained.

[0026] The specific surface area of the solid electrolyte material of the first embodiment can be 32.4 m 2 / g or more. According to such a configuration, the above-described effects can be sufficiently obtained.

[0027] To improve the ion conductivity of the solid electrolyte material, the solid electrolyte material of the first embodiment can contain at least one anion other than F. Examples of the anion include Cl, Br, I, O, or Se.

[0028] To improve the oxidation resistance of the solid electrolyte material, the ratio of the amount of substance of F to the total amount of substance of the anions constituting the solid electrolyte material of the first embodiment can be 0.50 or more and 1.0 or less.

[0029] In order to improve the oxidation resistance of the solid electrolyte material, the anion constituting the solid electrolyte material of the first embodiment can also be F alone. That is, the above-mentioned molar ratio can be 1.0.

[0030] The solid electrolyte material of the first embodiment can contain a phase represented by the composition formula (1).

[0031] Li 6-3a Al a F6 ・・・ (1)

[0032] (In the formula, 0 < a ≤ 1.5 is satisfied). The solid electrolyte material containing a phase having such a composition has high ionic conductivity.

[0033] In order to improve the ionic conductivity of the solid electrolyte material, in the formula (1), 0.7 ≤ a ≤ 1.3 can be satisfied, or 0.9 ≤ a ≤ 1.04 can be satisfied.

[0034] The upper limit value and the lower limit value of the range of a in the formula (1) can be defined by any combination of values selected from 0.7, 0.8, 0.9, 0.96, 1, 1.04, 1.1, 1.2, and 1.3.

[0035] The solid electrolyte material of the first embodiment can contain Li3AlF6, or can be Li3AlF6. Li3AlF6has excellent oxidation resistance.

[0036] The solid electrolyte material of the first embodiment can be crystalline, or can be amorphous.

[0037] The solid electrolyte material of the first embodiment can contain a phase represented by the formula (1).

[0038] The shape of the solid electrolyte material of the first embodiment is not limited. Examples of the shape are needle shape, spherical shape, or oval spherical shape. The solid electrolyte material of the first embodiment can also be a particle. The solid electrolyte material of the first embodiment can also have the shape of a pellet or a sheet.

[0039] <Manufacturing method of solid electrolyte material>

[0040] The solid electrolyte material of the first embodiment is manufactured, for example, by the following method.

[0041] The raw material powder of a plurality of halides weighed in such a manner as to have a target composition and an organic solvent are mixed while being micronized in a mixing device.

[0042] As an example, in the case where the target composition is Li3AlF6, LiF and AlF3are prepared in a molar ratio of about 3:1. The raw material powders are prepared in a molar ratio that is adjusted in advance to offset a change in composition that can occur during synthesis. The raw material powders and the organic solvent are introduced into a mixing device such as a planetary ball mill, and mixed while being micronized. That is, the treatment is performed using a wet ball mill. The raw material powders can also be mixed before being introduced into the mixing device.

[0043] After mixing, the balls are separated, and a slurry in which the particles are dispersed is obtained. The slurry is dried at a temperature corresponding to the boiling point of the organic solvent used, and a solid is obtained. The solid is pulverized using a mortar, and a reactant is obtained.

[0044] By performing wet micronization, it is possible to achieve the small particle size of the product resulting from micronization. That is, it is possible to increase the specific surface area of the solid electrolyte material.

[0045] By dissolving the solid obtained by drying the above slurry in an organic solvent and recrystallizing it, it is possible to expect further reduction in particle size. Alternatively, it is also possible to reduce the particle size by dissolving the raw material powders of the solid electrolyte material in an organic solvent and recrystallizing them, and then performing treatment using a wet ball mill.

[0046] The solid obtained by drying the above slurry can be fired in a vacuum or an inert atmosphere. The firing is performed at, for example, 100°C or higher and 300°C or lower for 1 hour or more. In order to suppress a change in composition during firing, the firing can also be performed in a closed container such as a quartz tube.

[0047] As described above, the solid electrolyte material of the first embodiment can be obtained by wet pulverization in which a mixture of a raw material composition containing constituent components of a solid electrolyte material and a solvent is pulverized. The raw material composition containing constituent components of a solid electrolyte material is raw material powders of a plurality of halides. The solvent is typically an organic solvent.

[0048] In order to increase the specific surface area of the solid electrolyte material, it is possible to reduce the particle size of the balls used in the wet ball mill. Alternatively, it is possible to increase the amount of the balls used in the wet ball mill. Alternatively, it is possible to extend the treatment time of the wet ball mill.

[0049] The solvent used in the wet ball mill can contain at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetrahydronaphthalene. By using these solvents, it is possible to produce the solid electrolyte material of the first embodiment. From the viewpoint of the dielectric constant of the solvent, it is possible to use N-methyl-2-pyrrolidone (NMP) as the solvent.

[0050] (Second Embodiment)

[0051] Next, the second embodiment will be described. Matters described in the first embodiment will be appropriately omitted.

[0052] The battery of the second embodiment has a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is provided between the positive electrode and the negative electrode.

[0053] At least one selected from the positive electrode, the electrolyte layer, and the negative electrode contains the solid electrolyte material of the first embodiment.

[0054] The battery of the second embodiment contains the solid electrolyte material of the first embodiment, and thus has excellent charge-discharge characteristics.

[0055] Figure 1 A cross-sectional view of the battery 1000 of the second embodiment is shown.

[0056] The battery 1000 of the second embodiment has 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.

[0057] The positive electrode 201 contains a positive electrode active material 204 and a solid electrolyte 100.

[0058] The electrolyte layer 202 contains an electrolyte material.

[0059] The negative electrode 203 contains a negative electrode active material 205 and the solid electrolyte 100.

[0060] The solid electrolyte 100 contains, for example, the solid electrolyte material of the first embodiment. The solid electrolyte 100 can be a particle containing the solid electrolyte material of the first embodiment as a main component. The particle containing the solid electrolyte material of the first embodiment as a main component means a particle in which the most abundant component is the solid electrolyte material of the first embodiment in terms of molar ratio. The solid electrolyte 100 can also be a particle composed of the solid electrolyte material of the first embodiment.

[0061] The positive electrode 201 contains a material capable of occluding and releasing metal ions (e.g., lithium ions). The material is, for example, the positive electrode active material 204.

[0062] Examples of the positive electrode active material 204 include lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, and transition metal oxynitrides. Here, the transition metal means, for example, a metal excluding d 10 elements (Zn, Cd, and Hg of Group 12), lanthanoid elements (except La (5d 16s 2 ) and actinide elements (except Ac (6d l 7S 2 ) and actinide elements (except Ac (6d Examples of the lithium-containing transition metal oxide include Li(Ni,Co,Mn)O2, Li(Ni,Co,Al)O2, or LiCoO2.

[0063] In the present disclosure, "(A, B, C)" means "at least one selected from A, B, and C".

[0064] The shape of the positive electrode active material 204 is not limited to a particular shape. The positive electrode active material 204 can be a particle. The positive electrode active material 204 can have a median particle diameter of 0.1 μm or more and 100 μm or less. In the case where the positive electrode active material 204 has a median particle diameter of 0.1 μm or more, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201. Thereby, the charge-discharge characteristics of the battery 1000 are improved. In the case where the positive electrode active material 204 has a median particle diameter of 100 μm or less, the lithium diffusion speed in the positive electrode active material 204 is improved. Thereby, the battery 1000 can operate at a high output.

[0065] The positive electrode active material 204 can have a larger median particle diameter than the solid electrolyte 100. Thereby, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201.

[0066] In order to improve the energy density and the output of the battery 1000, the ratio of the volume of the positive electrode active material 204 to the total of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 can be 0.30 or more and 0.95 or less in the positive electrode 201.

[0067] A coating layer can be formed on at least a part of the surface of the positive electrode active material 204. For example, the coating layer can be formed on the surface of the positive electrode active material 204 before being mixed with the conductive aid and the binder. Examples of the coating material contained in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. In the case where the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material can contain the solid electrolyte material of the first embodiment in order to suppress oxidative decomposition of the sulfide solid electrolyte. In the case where the solid electrolyte 100 contains the solid electrolyte material of the first embodiment, the coating material can contain an oxide solid electrolyte in order to suppress oxidative decomposition of the solid electrolyte material. As the oxide solid electrolyte, lithium niobate excellent in stability at a high potential can be used. By suppressing oxidative decomposition, the rise in the overvoltage of the battery 1000 can be suppressed.

[0068] The sulfide solid electrolyte is a solid electrolyte containing Li and S. In a case where the solid electrolyte 100 contains a sulfide solid electrolyte, as the sulfide solid electrolyte, a material described later, such as Li2S-P2S5, can be used. In a case where the positive electrode active material 204 is coated with the solid electrolyte material of the first embodiment, oxidation and decomposition of the solid electrolyte 100 containing Li and S can be suppressed.

[0069] In order to improve the energy density and output of the battery 1000, the positive electrode 201 can have a thickness of 10 µm or more and 500 µm or less.

[0070] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The solid electrolyte material can include the solid electrolyte material of the first embodiment. The electrolyte layer 202 can be a solid electrolyte layer.

[0071] The electrolyte layer 202 can contain 50% by mass or more of the solid electrolyte material of the first embodiment. The electrolyte layer 202 can contain 70% by mass or more of the solid electrolyte material of the first embodiment. The electrolyte layer 202 can contain 90% by mass or more of the solid electrolyte material of the first embodiment. The electrolyte layer 202 can also be composed only of the solid electrolyte material of the first embodiment.

[0072] Hereinafter, the solid electrolyte material of the first embodiment is referred to as a first solid electrolyte material. A solid electrolyte material different from the first solid electrolyte material is referred to as a second solid electrolyte material.

[0073] The electrolyte layer 202 can contain not only the first solid electrolyte material but also the second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material can be uniformly dispersed. A layer composed of the first solid electrolyte material and a layer composed of the second solid electrolyte material can be stacked along the stacking direction of the battery 1000.

[0074] The battery of the second embodiment can sequentially include the positive electrode 201, the second electrolyte layer, the first electrolyte layer, and the negative electrode 203. Here, the solid electrolyte material contained in the first electrolyte layer can have a lower reduction potential than the solid electrolyte material contained in the second electrolyte layer. Thus, the solid electrolyte material contained in the second electrolyte layer can be used without being reduced. As a result, the charge-discharge efficiency of the battery 1000 can be improved. For example, in the case where the second electrolyte layer contains the first solid electrolyte material, in order to suppress reduction decomposition of the solid electrolyte material, the first electrolyte layer can contain a sulfide solid electrolyte. Thus, the charge-discharge efficiency of the battery 1000 can be improved. The second electrolyte layer can contain the first solid electrolyte material. Since the first solid electrolyte material has high oxidation resistance, a battery having excellent charge-discharge characteristics can be realized.

[0075] The electrolyte layer 202 can be composed of only the second solid electrolyte material.

[0076] The electrolyte layer 202 can have a thickness of 1 μm or more and 1000 μm or less. In the case where the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 become difficult to short-circuit. In the case where the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high output.

[0077] Examples of the second solid electrolyte material are Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or LiI. Here, X is at least one selected from F, Cl, Br, and I.

[0078] In order to improve the energy density and the output of the battery 1000, the electrolyte layer 202 can have a thickness of 1 μm or more and 1000 μm or less.

[0079] The negative electrode 203 contains a material capable of occluding and releasing metal ions (e.g., lithium ions). The material is, for example, the negative electrode active material 205.

[0080] Examples of the negative electrode active material 205 are a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material can be a single metal, or can be an alloy. Examples of the metal material are lithium metal or a lithium alloy. Examples of the carbon material are natural graphite, coke, carbon in the process of graphitization, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of the capacity density, preferred examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0081] The negative electrode active material 205 can be selected in consideration of the reduction resistance of the solid electrolyte material contained in the negative electrode 203. For example, in the case where the negative electrode 203 contains the first solid electrolyte material, the negative electrode active material 205 can be a material capable of occluding and releasing lithium ions at 0.27 V or higher with respect to lithium. Examples of such a negative electrode active material are titanium oxide, indium metal, or a lithium alloy. Examples of the titanium oxide are Li4Ti5O12, LiTi2O4, or TiO2. By using the above-described negative electrode active material, reduction decomposition of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the charge and discharge efficiency of the battery 1000 can be improved. 12 3.25 0.25 The shape of the negative electrode active material 205 is not limited to a particular shape. The negative electrode active material 205 can be a particle. The negative electrode active material 205 can have a median particle diameter of 0.1 μm or more and 100 μm or less. In the case where the negative electrode active material 205 has a median particle diameter of 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. Thereby, the charge and discharge characteristics of the battery 1000 are improved. In the case where the negative electrode active material 205 has a median particle diameter of 100 μm or less, the lithium diffusion speed in the negative electrode active material 205 is improved. Thereby, the battery 1000 can operate at a high output. 0.75 10 The negative electrode active material 205 can have a larger median particle diameter than the solid electrolyte 100. Thereby, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. 12 14 In order to improve the energy density and the output of the battery 1000, the ratio of the volume of the negative electrode active material 205 with respect to the total of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 can be 0.30 or more and 0.95 or less in the negative electrode 203. 16 12 In order to improve the energy density and the output of the battery 1000, the negative electrode 203 can have a thickness of 10 μm or more and 500 μm or less. a b At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 can contain a second solid electrolyte material for the purpose of improving the ion conductivity, the chemical stability, and the electrochemical stability. c - The second solid electrolyte material can be a sulfide solid electrolyte. - - Examples of the sulfide solid electrolyte are Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li - - ​​P 0.75 S4or Li 10 GeP2S 12 .

[0089] In the case where the electrolyte layer 202 contains the first solid electrolyte material, in order to suppress reduction decomposition of the solid electrolyte material, the negative electrode 203 can contain a sulfide solid electrolyte. By covering the negative electrode active material with the electrochemically stable sulfide solid electrolyte, contact of the first solid electrolyte material with the negative electrode active material can be suppressed. As a result, internal resistance of the battery 1000 can be reduced.

[0090] The second solid electrolyte material can be an oxide solid electrolyte.

[0091] Examples of the oxide solid electrolyte include:

[0092] (i) a NASICON-type solid electrolyte such as LiTi2(PO4)3or an elemental substitute thereof,

[0093] (ii) a perovskite-type solid electrolyte such as (LaLi)TiO3,

[0094] (iii) Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4or an elemental substitute thereof, a LISICON-type solid electrolyte,

[0095] (iv) Li7La3Zr2O 12 or an elemental substitute thereof, a garnet-type solid electrolyte, or

[0096] (v) Li3PO4or an N-substitute thereof.

[0097] As described above, the second solid electrolyte material can be a halide solid electrolyte.

[0098] Examples of the halide solid electrolyte include Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6or LiI. Here, X is at least one selected from F, Cl, Br and I.

[0099] Other examples of the halide solid electrolyte include Li a Me b Y cThe compound represented by Z6. Among them, a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one selected from metal elements and semimetal elements other than Li and Y. Z is at least one selected from F, Cl, Br, and I. m represents the valence number of Me. The "semimetal element" is B, Si, Ge, As, Sb, and Te. The "metal element" refers to all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0100] In order to improve the ion conductivity of the halide solid electrolyte, Me can be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0101] The halide solid electrolyte can be Li3YCl6or Li3YBr6.

[0102] The second solid electrolyte material can be an organic polymer solid electrolyte.

[0103] Examples of the organic polymer solid electrolyte include a high molecular compound and a lithium salt.

[0104] The high molecular compound can have an oxirane structure. The high molecular compound having an oxirane structure can contain a large amount of lithium salt, and thus can further improve the ion conductivity.

[0105] Examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these can be used alone. Alternatively, a mixture of two or more lithium salts selected from these can be used.

[0106] At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 can contain a nonaqueous electrolyte solution, a gel electrolyte, or an ionic liquid in order to make the transfer of lithium ions easier and improve the output characteristics of the battery.

[0107] The nonaqueous electrolyte solution contains a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent.

[0108] Examples of the nonaqueous solvent are a cyclic carbonate solvent, a chain carbonate solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent. Examples of the cyclic carbonate solvent are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the chain carbonate solvent are dimethyl carbonate, methyl ethyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of the chain ether solvent are 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of the cyclic ester solvent are γ-butyrolactone. Examples of the chain ester solvent are methyl acetate. Examples of the fluorine solvent are fluoroethylene carbonate, fluoromethyl propionate, fluorobenzene, fluoro methyl ethyl carbonate, or fluoro dimethyl carbonate. One nonaqueous solvent selected from these can be used alone. Alternatively, a combination of two or more nonaqueous solvents selected from these can be used.

[0109] Examples of the lithium salt 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 can be used alone. Alternatively, a mixture of two or more lithium salts selected from these can be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0110] As the gel electrolyte, a polymer material impregnated with a nonaqueous electrolyte solution can be used. Examples of the polymer material are polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an oxirane bond.

[0111] Examples of the cation contained in the ionic liquid are:

[0112] (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium,

[0113] (ii) aliphatic cyclic amines such as pyrrolidinium, morpholinium, imidazolium, tetrahydropyrimidinium, piperazinium, or piperidinium, or

[0114] (iii) nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium.

[0115] Examples of the anion contained in the ionic liquid are PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9)- or C(SO2CF3)3 - .

[0116] The ionic liquid can contain a lithium salt.

[0117] At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 can contain a binder for improving adhesion between the particles.

[0118] Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamide-imide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, butadiene-styrene rubber, or carboxymethyl cellulose. A copolymer can also be used as the binder. Examples of such a binder include a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. A mixture of two or more materials selected from these can also be used as the binder.

[0119] At least one selected from the positive electrode 201 and the negative electrode 203 can contain a conductive aid for improving electronic conductivity.

[0120] Examples of the conductive aid include:

[0121] (i) graphite such as natural graphite or artificial graphite,

[0122] (ii) carbon black such as acetylene black or ketjen black,

[0123] (iii) electrically conductive fibers such as carbon fibers or metal fibers,

[0124] (iv) fluorinated carbon,

[0125] (v) metal powders such as aluminum,

[0126] (vi) electrically conductive whiskers such as zinc oxide or potassium titanate,

[0127] (vii) electrically conductive metal oxides such as titanium oxide, or

[0128] (viii) electrically conductive high molecular compounds such as polyaniline, polypyrrole, or polythiophene.

[0129] The conductive aid of (i) or (ii) described above can be used for reducing cost.

[0130] Examples of the shape of the battery of the second embodiment include a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a stacked type.

[0131] The battery of the second embodiment can be manufactured, for example, as follows: preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and producing a stack in which a positive electrode, an electrolyte layer, and a negative electrode are sequentially arranged, by a publicly known method.

[0132] (POSTSCRIPT)

[0133] According to the above description, the following technical solutions are disclosed.

[0134] (Technical Solution 1)

[0135] A solid electrolyte material composed of Li, Al, and X,

[0136] X is an anion containing F,

[0137] The specific surface area of the solid electrolyte material is 16 m 2 / g or more.

[0138] According to the present disclosure, it is possible to provide a solid electrolyte material that is suitable for lithium ion conduction and has improved contact with other materials.

[0139] (Technical Solution 2)

[0140] The solid electrolyte material according to Technical Solution 1,

[0141] The solid electrolyte material contains a phase represented by Composition Formula (1),

[0142] Li 6-3x Al x F6 ・・・ (1)

[0143] In the formula, 0 < x ≤ 1.5 is satisfied.

[0144] The solid electrolyte material containing the phase having such a composition has high ion conductivity.

[0145] (Technical Solution 3)

[0146] The solid electrolyte material according to Technical Solution 1 or 2, the ratio of the amount of substance of F to the total amount of substance of the anions constituting the solid electrolyte material is 0.50 or more and 1.0 or less. According to such a configuration, it is possible to improve the oxidation resistance of the solid electrolyte material.

[0147] (Technical Solution 4)

[0148] The solid electrolyte material according to any one of the aspects 1 to 3 contains Li3AlF6. According to such a configuration, the oxidation resistance of the solid electrolyte material can be improved.

[0149] (Aspect 5)

[0150] The solid electrolyte material according to any one of the aspects 1 to 4 has a specific surface area of less than 100 m 2 / g. According to such a configuration, the above-described effects can be sufficiently obtained.

[0151] (Aspect 6)

[0152] The solid electrolyte material according to any one of the aspects 1 to 5 has a specific surface area of less than 60 m 2 / g. According to such a configuration, the above-described effects can be sufficiently obtained.

[0153] (Aspect 7)

[0154] The solid electrolyte material according to any one of the aspects 1 to 6 has a specific surface area of 32.4 m 2 / g or more. According to such a configuration, the above-described effects can be sufficiently obtained.

[0155] (Aspect 8)

[0156] A method for manufacturing a solid electrolyte material is a method for manufacturing the solid electrolyte material according to any one of the aspects 1 to 7, and includes a wet-type pulverization process of pulverizing a mixture containing a raw material composition and a solvent, the raw material composition containing components constituting the solid electrolyte material. According to such a configuration, the solid electrolyte material of the present disclosure can be obtained.

[0157] (Aspect 9)

[0158] The method for manufacturing a solid electrolyte material according to the aspect 8, wherein the solvent contains at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetrahydronaphthalene. By using these solvents, the solid electrolyte material of the present disclosure can be manufactured.

[0159] (Aspect 10)

[0160] A positive electrode material contains the solid electrolyte material according to any one of the aspects 1 to 7, and a positive electrode active material coated with the solid electrolyte material. According to such a configuration, the contact of other materials such as a solid electrolyte with the positive electrode active material can be suppressed, and the decomposition of the other materials can be suppressed.

[0161] (Aspect 11)

[0162] A battery having a positive electrode and an electrolyte layer, the positive electrode comprising the positive electrode material described in Technical Solution 10. According to the present disclosure, a battery in which the overvoltage rise is suppressed can be obtained.

[0163] (Technical Solution 12)

[0164] The battery described in Technical Solution 11 is a solid-state battery. The solid electrolyte material of the present disclosure is suitable as a material for a solid-state battery.

[0165] (Technical Solution 13)

[0166] The battery described in Technical Solution 11 or 12, the electrolyte layer comprising a solid electrolyte containing Li and S. According to the present disclosure, oxidation decomposition of the solid electrolyte containing Li and S can be suppressed.

[0167] Examples

[0168] Hereinafter, the present disclosure will be described in detail with reference to Examples and Comparative Examples.

[0169] Example 1

[0170] (Production of solid electrolyte material)

[0171] LiF and AlF3 as raw material powders were prepared in a molar ratio of LiF:AlF3 = 3:1 under an argon atmosphere having a dew point of -60°C or lower (hereinafter referred to as "dry argon atmosphere"). These raw material powders were put into a container for a 45-cc planetary ball mill together with 1-mm-Φ balls (25 g). To the container, γ-butyrolactone (GBL) as an organic solvent was added dropwise so that the solid content ratio became 30%. Here, the solid content ratio was calculated from {(mass of the raw material put in) / (mass of the raw material put in + mass of the solvent put in)} x 100. Using a planetary ball mill, a grinding treatment was performed at 500 rpm for 12 hours. After the grinding treatment, the balls were separated to obtain a slurry. Using a jacketed heater, the obtained slurry was dried at 270°C for 1 hour under a nitrogen stream. By pulverizing the obtained solid substance with a mortar, a powder of the solid electrolyte material of Example 1 was obtained. The solid electrolyte material of Example 1 had a composition represented by Li3AlF6.

[0172] (Evaluation of ion conductivity)

[0173] Figure 2 A schematic view of a press molding mold 300 used for evaluating the ion conductivity of a solid electrolyte material is shown.

[0174] The press molding mold 300 has a punch upper portion 301, a frame mold 302, and a punch lower portion 303. The frame mold 302 is formed of an insulating polycarbonate. The punch upper portion 301 and the punch lower portion 303 are formed of an electrically conductive stainless steel.

[0175] Using Figure 2 The press molding mold 300 shown in the figure, by the following method, the ion conductivity of the solid electrolyte material of Example 1 was evaluated.

[0176] In a dry atmosphere having a dew point of -30°C or less, the powder of the solid electrolyte material of Example 1 was filled into the inside of the press molding mold 300. In the inside of the press molding mold 300, the solid electrolyte material of Example 1 was subjected to a pressure of 400 MPa using the punch upper portion 301 and the punch lower portion 303.

[0177] In the state where the pressure was applied, the punch upper portion 301 and the punch lower portion 303 were connected to a potentiostat (VSP300, manufactured by BioLogic) on which a frequency response analyzer was mounted. The punch upper portion 301 was connected to a working electrode and a potential measurement terminal. The punch lower portion 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.

[0178] Figure 3 is a graph showing the Cole-Cole plot of the solid electrolyte material of Example 1 obtained by impedance measurement.

[0179] In Figure 3 , the real value of the impedance of the measurement point at which the absolute value of the phase of the complex impedance was the smallest was regarded as the resistance value of the solid electrolyte material with respect to ion conduction. With respect to this real value, refer to the arrow R SE shown in Figure 3 . Using this resistance value, the ion conductivity was calculated by Formula (i).

[0180] σ = (R SE × S / t) -1 ・・・(i)

[0181] where σ represents the ion conductivity. S represents the contact area of the solid electrolyte material with the punch upper portion 301. That is, S is equal to the cross-sectional area of the hollow portion of the frame mold 302 in Figure 3 . R SE represents the resistance value of the solid electrolyte material in the impedance measurement. t represents the thickness of the solid electrolyte material. That is, in Figure 3 , t represents the thickness of the layer formed of the powder 101 of the solid electrolyte material.

[0182] The ion conductivity of the solid electrolyte material of Example 1 measured at 25°C was 1.4 x 10-10 S / cm.

[0183] (Measurement of specific surface area)

[0184] In the measurement of specific surface area, a specific surface area / pore distribution measuring device (BELSORP MINI X, manufactured by Microtrac Bell) was used. Hereinafter, the specific surface area obtained using this device is referred to as the BET specific surface area.

[0185] In an atmosphere having a dew point of -40°C or lower, the powder (about 1 g) of the solid electrolyte material of Example 1 was put into a dedicated test tube.

[0186] As a pretreatment, vacuum drying was performed at 80°C for 1 hour.

[0187] The mass of the sample put in was measured from the difference between the weight of the test tube containing the sample after the pretreatment and the weight of the test tube before the sample was put in.

[0188] The measurement of the BET specific surface area was performed using the pretreated test tube, and as a result, the specific surface area of the solid electrolyte material of Example 1 was 16.0 m 2 / g.

[0189] (Production of coated active material)

[0190] As the positive active material, a powder of Li(Ni, Co, Al)02 (hereinafter referred to as NCA) was prepared. A coating layer made of LAF was formed on the surface of the NCA. The coating layer was formed by compression shear treatment using a particle complexing device (NOB-MINI, manufactured by Seki Corporation). Specifically, the NCA and the LAF were weighed in a volume ratio of 98.9:1.1, and the treatment was performed under the conditions of a blade gap of 2 mm, a rotation speed of 8000 rpm, and a treatment time of 30 min. Thus, the coated active material of Example 1 was obtained.

[0191] (Production of sulfide solid electrolyte)

[0192] In an argon glove box having a dew point of -60°C or lower, Li2S and P2S5 as raw material powders were weighed in a molar ratio of Li2S:P2S5 = 75:25. They were pulverized and mixed in a mortar to obtain a mixture. Then, using a planetary ball mill (P-7 type, manufactured by Fritsch), the mixture was subjected to grinding treatment under the conditions of 10 hours and 510 rpm. Thus, a glassy solid electrolyte was obtained. The glassy solid electrolyte was subjected to heat treatment in an inert atmosphere at 270°C for 2 hours. Thus, a glass-ceramic solid electrolyte Li2S-P2S5 (hereinafter referred to as "LPS") was obtained.

[0193] (Production of battery)

[0194] The positive active material of Example 1 and LPS were weighed in a volume ratio of 7:3 of the coated active material to the sulfide solid electrolyte in a dry argon atmosphere. They were mixed in an agate mortar, thereby producing the positive electrode material mixture of Example 1.

[0195] In an insulating cylinder having an inner diameter of 9.5 mm, LPS (50 mg) and the above positive electrode mixture (10 mg) were stacked in this order. The resultant stack was subjected to a pressure of 300 MPa, thereby forming an electrolyte layer and a positive electrode. The thickness of the electrolyte layer was 400 μm.

[0196] Next, metal Li (thickness: 200 μm) was stacked on the first electrolyte layer. The resultant stack was subjected to a pressure of 80 MPa, thereby forming a negative electrode.

[0197] Next, a current collector formed of stainless steel was attached to the positive electrode and the negative electrode, and a current collecting lead was attached to the current collector.

[0198] Finally, the inside of the insulating cylinder was sealed from the outside gas atmosphere using an insulating grommet, thereby sealing the inside of the cylinder. In this way, the battery of Example 1 was obtained.

[0199] (Charge-discharge test)

[0200] Figure 4 is a graph showing the initial discharge characteristics of the battery of Example 1. The initial charge-discharge characteristics were measured by the following method.

[0201] The battery of Example 1 was placed in a thermostat set to 25°C.

[0202] The battery of Example 1 was charged at a current density of 125 μA / cm 2 until the voltage reached 4.3 V. This current density corresponds to 0.1 C rate.

[0203] Then, the battery of Example 1 was discharged at a current density of 125 μA / cm 2 until the voltage reached 3.1 V.

[0204] As a result of the charge-discharge test, the battery of Example 1 had an initial discharge capacity of 1340 μAh.

[0205] <Examples 2 to 4>

[0206] (Production of solid electrolyte material)

[0207] In Examples 2 to 4, as in Example 1, LiF and AlF3 were prepared as raw material powders in a molar ratio of LiF:AlF3=3:1.

[0208] The solvent, the ratio of solid components, the ball diameter, the ball amount, the treatment time, and the drying conditions in the grinding treatment are shown in Table 1.

[0209] The solid electrolyte materials of Examples 2 to 4 were obtained in the same manner as in Example 1 except for the conditions shown in Table 1.

[0210] (Evaluation of Ion Conductivity)

[0211] The ion conductivities of the solid electrolyte materials of Examples 2 to 4 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0212] (Measurement of Specific Surface Area)

[0213] The BET specific surface areas were measured in the same manner as in Example 1 using the solid electrolyte materials of Examples 2 to 4. The measurement results are shown in Table 1.

[0214] (Charge and Discharge Test)

[0215] The batteries of Examples 2 to 4 were obtained in the same manner as in Example 1 using the solid electrolyte materials of Examples 2 to 4.

[0216] The charge and discharge tests were performed in the same manner as in Example 1 using the batteries of Examples 2 to 4. As a result, the batteries of Examples 2 to 4 were charged and discharged as well as the battery of Example 1.

[0217] <Reference Example 1>

[0218] LiF and AlF3 as raw material powders were prepared in a molar ratio of LiF:AlF3 = 3:1 under a dry argon atmosphere. These raw material powders were pulverized and mixed in a mortar. The obtained mixed powder was put into a container for a 45 cc planetary ball mill together with balls of 5 mm Φ (25 g). A planetary ball mill was used to perform a grinding treatment at 500 rpm for 12 hours. In this way, the solid electrolyte material of Reference Example 1 was obtained.

[0219] As described above, the solid electrolyte material of Reference Example 1 was produced by a dry-type ball mill without using an organic solvent.

[0220] The ion conductivity and the specific surface area were measured in the same manner as in Example 1 using the solid electrolyte material of Reference Example 1.

[0221] The ion conductivity measured at 25°C was 8.3 x 10 -8 S / cm.

[0222] The specific surface area measured was 3.1 m 2 / g.

[0223] <Comparative Example 1>

[0224] The ion conductivity was measured in the same manner as in Example 1 using LiF as the solid electrolyte material. As a result, the ion conductivity could not be measured at 25°C.

[0225] Table 1

[0226]

[0227] <Investigation>

[0228] The solid electrolyte materials of Examples 1 to 4 had an ion conductivity of 1.2 x 10 -10 S / cm or more at room temperature, and had a specific surface area of 16 m 2 / g or more. On the other hand, the solid electrolyte material of Reference Example 1, which was produced by a dry ball mill, had a small specific surface area of 3.1 m 2 / g.

[0229] The batteries of Examples 1 to 4 were each charged and discharged at 25°C.

[0230] As described above, the solid electrolyte material of the present disclosure is suitable for providing a battery that has a high lithium ion conductivity and that can be charged and discharged well.

[0231] It is considered that the results shown in the present example can also be obtained in the case of using a positive electrode active material other than NCA, particularly in the case of using a lithium-containing transition metal oxide. The solid electrolyte material having a high specific surface area enters a recess on the surface of the active material, and the contactability of the solid electrolyte material with the active material is improved. This effect is obtained regardless of the composition of the positive electrode active material. This effect is particularly remarkable in the case where the particles of the positive electrode active material are secondary particles.

[0232] Industrial applicability

[0233] The solid electrolyte material of the present disclosure can be used, for example, in a lithium ion secondary battery.

[0234] Explanation of reference signs

[0235] 100 solid electrolyte

[0236] 101 powder of solid electrolyte material

[0237] 201 positive electrode

[0238] 202 electrolyte layer

[0239] 203 negative electrode

[0240] 204 positive electrode active material

[0241] 205 negative electrode active material

[0242] 300 press molding mold

[0243] 301 punch upper portion

[0244] 302 frame mold

[0245] 303 punch lower portion

[0246] 1000 battery

Claims

1. A solid electrolyte material composed of Li, Al, and X, X is an anion containing F, The specific surface area of the solid electrolyte material is 16 m 2 / g or more.

2. The solid electrolyte material according to claim 1, the solid electrolyte material contains a phase represented by composition formula (1), Li 6-3x Al x F6 ・・・(1) wherein 0 < x < 1.5 is satisfied.

3. The solid electrolyte material according to claim 1, the total ratio of the amount of substance of F with respect to the amount of substance of the anion constituting the solid electrolyte material is 0.50 or greater and 1.0 or less.

4. The solid electrolyte material according to claim 1, the solid electrolyte material contains Li3AlF6.

5. The solid electrolyte material according to claim 1, The specific surface area is less than 100 m 2 / g.

6. The solid electrolyte material according to claim 1, The specific surface area is less than 60 m 2 / g.

7. The solid electrolyte material according to claim 1, The specific surface area is 32.4 m 2 / g or more.

8. A method for producing a solid electrolyte material, which is a method for producing the solid electrolyte material according to claim 1, comprising a wet-type pulverization step of pulverizing a mixture containing a raw material composition and a solvent, the raw material composition containing components constituting the solid electrolyte material.

9. The method for producing a solid electrolyte material according to claim 8, the solvent contains at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetrahydronaphthalene.

10. A positive electrode material containing the solid electrolyte material according to any one of claims 1 to 7, and a positive electrode active material coated with the solid electrolyte material.

11. A battery provided with a positive electrode and an electrolyte layer, the positive electrode contains the positive electrode material according to claim 10.

12. The battery according to claim 11, the battery is a solid-state battery.

13. The battery according to claim 11, the electrolyte layer contains a solid electrolyte containing Li and S.

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