Solid electrolyte materials and batteries using the same

Abstract

A solid electrolyte material according to the present disclosure contains Li, Zr, Al and F. The specific surface area of the solid electrolyte material is greater than 3.2 m2 / g. This battery 1000 comprises a positive electrode 201, a negative electrode 203, and an electrolyte layer 202 disposed between the positive electrode 201 and the negative electrode 203, wherein 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.

Description

Technical Field

[0001] This 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 LiBF4 as a fluoride solid electrolyte material.

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of this disclosure is to provide a solid electrolyte material suitable for lithium ion conduction and having improved contact with other materials.

Means for Solving the Problems

[0006] The solid electrolyte material of this disclosure is a solid electrolyte material containing Li, Zr, Al, and F, where the specific surface area of the solid electrolyte material is greater than 3.2 m 2 / g.

Effects of the Invention

[0007] This disclosure provides a solid electrolyte material suitable for lithium ion conduction and having improved contact with other materials.

Brief Description of the Drawings

[0008] [Figure 1] Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment. [Figure 2] Figure 2 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material. [Figure 3] Figure 3 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1. [Figure 4] Figure 4 is a graph showing the initial discharge characteristics of batteries according to Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described below with reference to the drawings.

[0010] (First Embodiment) The solid electrolyte material according to the first embodiment comprises Li, Zr, Al, and F. The specific surface area of ​​the solid electrolyte material according to the first embodiment is 3.2 m². 2 Greater than / g. Here, the specific surface area of ​​the solid electrolyte material in this disclosure refers to the specific surface area determined by the BET method.

[0011] The solid electrolyte material according to the first embodiment is suitable for lithium ion conduction and has good contact with other materials. Therefore, the solid electrolyte material according to the first embodiment can reduce the resistance at the interface with other materials. Other materials include, for example, active materials.

[0012] Generally, polycrystalline materials are used as active materials in lithium-ion secondary batteries. The surface of the active material is not flat, but often has irregularities such as small grooves or depressions. Unlike electrolyte-based batteries, in all-solid-state batteries, it is desirable to improve the contact between the active material and the solid electrolyte in order to reduce the battery's resistance. To achieve this, the solid electrolyte needs to deform by compression or other means to match the irregular shape of the active material. However, if the surface of the solid electrolyte is flat and the particle size of the solid electrolyte is large, the pressure during pressing will concentrate on the protrusions on the surface of the active material, and good contact cannot be obtained inside the depressions. On the other hand, if the particle size of the solid electrolyte is smaller than the depressions on the surface of the active material, good contact can be obtained because the pressure is applied while the electrolyte is inside the depressions. Also, if the surface of the solid electrolyte has irregularities, the solid electrolyte can more easily enter the depressions on the surface of the active material compared to when the surface is flat, making it easier to achieve good contact between the solid electrolyte and the active material. Small particle size or irregularities on the surface mean a large specific surface area. In other words, solid electrolytes with a large specific surface area are more likely to achieve good contact with the active material. As a result, the battery's resistance can be reduced, which can improve, for example, the battery's charge and discharge characteristics.

[0013] The solid electrolyte material according to the first embodiment can be used, for example, 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 is preferably sulfur-free. Sulfur-free solid electrolyte materials do not generate hydrogen sulfide when exposed to the atmosphere, thus offering superior safety. The sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

[0015] Since the solid electrolyte material according to the first embodiment contains F, it can have high oxidation resistance. This is because F has a high redox potential. On the other hand, since F has a high electronegativity, its bond with Li is relatively strong. As a result, usually, the lithium ion conductivity of a solid electrolyte material containing Li and F is low. For example, LiBF4 disclosed in Patent Document 2 has a low ionic conductivity of 6.67×10 -9 S / cm. In contrast, the solid electrolyte material according to the first embodiment can have an ionic conductivity of 7×10 -9 S / cm or more by further containing Zr and Al in addition to Li and F. That is, the solid electrolyte material according to the first embodiment is suitable for lithium ion conduction.

[0016] The specific surface area of the solid electrolyte material according to the first embodiment may be smaller than 100 m 2 / g, may be smaller than 40 m 2 / g, or may be 35.19 m 2 / g or less.

[0017] The specific surface area of the solid electrolyte material according to the first embodiment may be 5.2 m 2 / g or more, or may be 5.29 m 2 / g or more.

[0018] In order to increase the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may further contain an anion other than F. Examples of the anion are Cl, Br, I, O, or Se.

[0019] In order to increase the oxidation resistance of the solid electrolyte material, the ratio of the amount of substance of F to the total amount of substance of anions constituting the solid electrolyte material according to the first embodiment may be 0.50 or more and 1.0 or less.

[0020] In order to improve the oxidation resistance of the solid electrolyte material, the anion constituting the solid electrolyte material according to the first embodiment may be only F. That is, the ratio of the amount of substance may be 1.0.

[0021] The solid electrolyte material according to the first embodiment may substantially consist of Li, Zr, Al, and F. Here, "the solid electrolyte material according to the first embodiment substantially consists of Li, Zr, Al, and F" means that the ratio of the total amount of the substances of Li, Zr, Al, and F to the total amount of the substances of all the elements constituting the solid electrolyte material according to the first embodiment (i.e., the molar fraction) is 90% or more. As an example, the ratio (i.e., the molar fraction) may be 95% or more. The solid electrolyte material according to the first embodiment may consist only of Li, Zr, Al, and F.

[0022] The solid electrolyte material according to the first embodiment may contain unavoidably mixed elements. Examples of such elements are hydrogen, oxygen, or nitrogen. Such elements may be present in the raw material powder of the solid electrolyte material or in the atmosphere for manufacturing or storing the solid electrolyte material.

[0023] In order to further increase the ionic conductivity of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, the ratio of the amount of substance of Li to the total amount of the substances of Zr and Al may be 1.12 or more and 5.07 or less.

[0024] The solid electrolyte material according to the first embodiment may be a material represented by the following compositional formula (1).

[0025] Li 6-(4-x)b (Zr 1-x Al x ) b F6···(1) In formula (1), 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. The solid electrolyte material having such a composition has high ionic conductivity.

[0026] In order to increase the ionic conductivity of the solid electrolyte material, in formula (1), 0.01 ≤ x ≤ 0.99 may be satisfied, or 0.2 ≤ x ≤ 0.95 may be satisfied.

[0027] The upper and lower limits of the range of x in equation (1) can be defined by any combination selected from the numbers 0.01, 0.2, 0.4, 0.5, 0.5, 0.7, 0.8, 0.95, and 0.99.

[0028] To improve the ionic conductivity of the solid electrolyte material, the conditions 0.7 ≤ b ≤ 1.3 may be satisfied in equation (1), and the conditions 0.9 ≤ b ≤ 1.04 may also be satisfied.

[0029] The upper and lower limits of the range of b in equation (1) can be defined by any combination selected from the numbers 0.7, 0.8, 0.9, 0.96, 1, 1.04, 1.1, 1.2, and 1.3.

[0030] The solid electrolyte material according to the first embodiment is Li 2.8 Zr 0.2 Al 0.8 F6 is also acceptable.

[0031] The solid electrolyte material according to the first embodiment may be crystalline or amorphous.

[0032] The solid electrolyte material according to the first embodiment may contain a crystalline phase represented by formula (1).

[0033] The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of such shapes include needle-shaped, spherical, or ellipsoidal. The solid electrolyte material according to the first embodiment may be particles. The solid electrolyte material according to the first embodiment may have the shape of pellets or plates.

[0034] <Method for manufacturing solid electrolyte materials> The solid electrolyte material according to the first embodiment is manufactured, for example, by the following method.

[0035] Multiple halogenated raw material powders, weighed to have the desired composition, are mixed with an organic solvent in a mixing apparatus while being pulverized.

[0036] For example, if the target composition is Li 2.8 Zr 0.2 Al 0.8 For F6, LiF, ZrF4, and AlF3 are prepared in a molar ratio of approximately 2.8:0.2:0.8. The raw material powders may be prepared in a pre-adjusted molar ratio to compensate for any compositional changes that may occur during the synthesis process. The raw material powders and organic solvents are introduced into a mixing device such as a planetary ball mill and mixed while being pulverized. In other words, the process is carried out using a wet ball mill. The raw material powders may be mixed before being introduced into the mixing device.

[0037] After mixing, separating the balls yields a slurry with dispersed particles. Drying the slurry at a temperature corresponding to the boiling point of the organic solvent used yields a solid. Grinding this solid in a mortar yields the reaction product.

[0038] By performing micronization using a wet process, it is possible to reduce the particle size of the resulting product. In other words, the specific surface area of ​​the solid electrolyte material can be improved.

[0039] The solid obtained by drying the above slurry can be expected to have its particle size further reduced by dissolving it in an organic solvent and recrystallizing it. Alternatively, the raw material powder of the solid electrolyte material may be dissolved in an organic solvent and recrystallized to reduce its particle size, and then processed using a wet ball mill.

[0040] The solid obtained by drying the slurry may be calcined in a vacuum or an inert atmosphere. Calcination is carried out, for example, at a temperature of 100°C or higher and 300°C or lower for at least one hour. To suppress compositional changes during calcination, calcination may be carried out in a sealed container such as a quartz tube.

[0041] As described above, a solid electrolyte material according to the first embodiment can be obtained by performing wet grinding on a mixture containing a raw material composition containing the constituent components of the solid electrolyte material and a solvent.

[0042] To increase the specific surface area of ​​the solid electrolyte material, the particle size of the balls used in the wet ball mill may be reduced. Alternatively, the number of balls used in the wet ball mill may be increased. Alternatively, the processing time in the wet ball mill may be extended.

[0043] The solvent used in the wet ball mill may include at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetralin. From the viewpoint of the dielectric constant of the solvent, N-methyl-2-pyrrolidone (NMP) may be used as the solvent.

[0044] (Second Embodiment) The second embodiment will now be described. Matters described in the first embodiment will be omitted as appropriate.

[0045] The battery according to the second embodiment comprises a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is located between the positive electrode and the negative electrode.

[0046] At least one selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode contains a solid electrolyte material according to the first embodiment.

[0047] The battery according to the second embodiment has excellent charge and discharge characteristics because it contains the solid electrolyte material according to the first embodiment.

[0048] Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment.

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

[0050] The positive electrode 201 contains a positive electrode active material 204 and a solid electrolyte 100.

[0051] The electrolyte layer 202 contains an electrolyte material.

[0052] The negative electrode 203 contains a negative electrode active material 205 and a solid electrolyte 100.

[0053] The solid electrolyte 100 includes, for example, the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles containing the solid electrolyte material according to the first embodiment as the main component. Particles containing the solid electrolyte material according to the first embodiment as the main component mean particles in which the most abundant component in terms of molar ratio is the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles made of the solid electrolyte material according to the first embodiment.

[0054] The positive electrode 201 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the positive electrode active material 204.

[0055] Examples of positive electrode active material 204 include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Mn)O2, Li(Ni,Co,Al)O2, or LiCoO2.

[0056] In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0057] The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 may be particles. The positive electrode active material 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median 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. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material 204 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 is improved. This allows the battery 1000 to operate at high power.

[0058] The positive electrode active material 204 may have a median diameter larger than that of the solid electrolyte 100. This allows the positive electrode active material 204 and the solid electrolyte 100 to be well dispersed in the positive electrode 201.

[0059] In order to improve the energy density and output of the battery 1000, the ratio of the volume of the positive electrode active material 204 to the sum of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 in the positive electrode 201 may be 0.30 or more and 0.95 or less.

[0060] A coating layer may be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer can be formed on the surface of the positive electrode active material 204, for example, before mixing with a conductive additive and a binder. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes. If the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material may contain the solid electrolyte material according to the first embodiment in order to suppress the oxidative decomposition of the sulfide solid electrolyte. If the solid electrolyte 100 contains the solid electrolyte material according to the first embodiment, the coating material may contain an oxide solid electrolyte in order to suppress the oxidative decomposition of the solid electrolyte material. As the oxide solid electrolyte, lithium niobate, which has excellent stability at high potentials, may be used. By suppressing oxidative decomposition, the overvoltage rise of the battery 1000 can be suppressed.

[0061] To improve the energy density and output of battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0062] The electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. This solid electrolyte material may include the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may also be a solid electrolyte layer.

[0063] The electrolyte layer 202 may contain 50% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 70% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 90% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may consist only of the solid electrolyte material according to the first embodiment.

[0064] Hereinafter, the solid electrolyte material according to the first embodiment will be referred to as the first solid electrolyte material. A solid electrolyte material different from the first solid electrolyte material will be referred to as the second solid electrolyte material.

[0065] The electrolyte layer 202 may contain not only a first solid electrolyte material but also a second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed. The layer made of the first solid electrolyte material and the layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

[0066] The battery according to the second embodiment may comprise a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203 in this order. Here, the solid electrolyte material contained in the first electrolyte layer may have a lower reduction potential than the solid electrolyte material contained in the second electrolyte layer. This allows the solid electrolyte material contained in the second electrolyte layer to be used without reduction. As a result, the charge and discharge efficiency of the battery 1000 can be improved. For example, if the second electrolyte layer contains the first solid electrolyte material, the first electrolyte layer may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. This improves the charge and discharge efficiency of the battery 1000. The second electrolyte layer may also contain the first solid electrolyte material. Since the first solid electrolyte material has high oxidation resistance, a battery with excellent charge and discharge characteristics can be realized.

[0067] The electrolyte layer 202 may consist solely of the second solid electrolyte material.

[0068] The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. If 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. If the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high output.

[0069] Examples of second solid electrolyte materials are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0070] To improve the energy density and output of the battery 1000, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0071] The negative electrode 203 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the negative electrode active material 205.

[0072] Examples of negative electrode active materials 205 are metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. Metallic materials may be elemental metals or alloys. Examples of metallic materials are lithium metal or lithium alloys. Examples of carbon materials are natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of negative electrode active materials are silicon (i.e., Si), tin (i.e., Sn), silicon compounds, or tin compounds.

[0073] The negative electrode active material 205 may be selected considering the reduction resistance of the solid electrolyte material contained in the negative electrode 203. For example, if the negative electrode 203 contains a first solid electrolyte material, the negative electrode active material 205 may be a material capable of intercalating and releasing lithium ions at a voltage of 0.27 V or higher relative to lithium. Examples of such negative electrode active materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12The negative electrode active material is either LiTi2O4 or TiO2. By using the above negative electrode active material, the reductive 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.

[0074] The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 may be particles. The negative electrode active material 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median 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. This improves the charge and discharge characteristics of the battery 1000. When the negative electrode active material 205 has a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 is improved. This allows the battery 1000 to operate at high power.

[0075] The negative electrode active material 205 may have a larger median diameter than the solid electrolyte 100. This allows the negative electrode active material 205 and the solid electrolyte 100 to be well dispersed in the negative electrode 203.

[0076] In order to improve the energy density and output of the battery 1000, the ratio of the volume of the negative electrode active material 205 to the sum of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 in the negative electrode 203 may be 0.30 or more and 0.95 or less.

[0077] To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0078] At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a second solid electrolyte material for the purpose of enhancing ionic conductivity, chemical stability, and electrochemical stability.

[0079] The second solid electrolyte material may be a sulfide solid electrolyte.

[0080] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 That is the case.

[0081] If the electrolyte layer 202 contains a first solid electrolyte material, the negative electrode 203 may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. By covering the negative electrode active material with an electrochemically stable sulfide solid electrolyte, contact between the first solid electrolyte material and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery 1000 can be reduced.

[0082] The second solid electrolyte material may be an oxide solid electrolyte.

[0083] Examples of oxide solid electrolytes are: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions, (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3, (iii) Li 14 ZnGe4O 16 , LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or their elementally substituted counterparts, (iv)Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an elemental substitution thereof, (v) Li3PO4 or its N-substituted derivatives, That is the case.

[0084] As described above, the second solid electrolyte material may be a halide solid electrolyte.

[0085] Examples of halide solid electrolytes are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0086] Other examples of halide solid electrolytes include Li a Me b Y c This is a compound represented by Z6. Here, a+mb+3c=6 and c>0 are satisfied. Me is at least one selected from the group consisting of metallic elements other than Li and Y and metalloid elements. Z is at least one selected from the group consisting of F, Cl, Br, and I. m represents the valence of Me. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements in groups 1 through 12 of the periodic table (except hydrogen), and all elements in groups 13 through 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0087] To improve the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0088] The halide solid electrolyte may be Li3YCl6 or Li3YBr6.

[0089] The second solid electrolyte material may be an organic polymer solid electrolyte.

[0090] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds.

[0091] Polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt, and therefore their ionic conductivity can be further increased.

[0092] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0093] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid to facilitate the transfer of lithium ions and improve the output characteristics of the battery.

[0094] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0095] Examples of non-aqueous solvents include cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorinated solvents. Examples of cyclic carbonate solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of linear carbonate solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Linear ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a linear ester solvent is methyl acetate. Examples of fluorinated solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a combination of two or more non-aqueous solvents selected from these may be used.

[0096] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0097] Polymer materials impregnated with a non-aqueous electrolyte can be used as the gel electrolyte. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds.

[0098] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium, (ii) Aliphatic cyclic ammonium compounds such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperadiniums, or piperidiniums, (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium That is the case.

[0099] An example of anion contained in an ionic liquid is PF6. - BF4 - SbF6 - AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case.

[0100] The ionic liquid may contain lithium salts.

[0101] At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a binder to improve the adhesion between particles.

[0102] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyethers, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, or carboxymethylcellulose. Copolymers can also be used as binders. Examples of such binders are 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. A mixture of two or more materials selected from these may also be used as a binder.

[0103] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity.

[0104] Examples of conductive additives are: (i) Graphites such as natural graphite or artificial graphite, (ii) Carbon blacks such as acetylene black or Ketjen black, (iii) Conductive fibers such as carbon fibers or metal fibers, (iv) Carbon fluoride, (v) Metal powders such as aluminum, (vi) Conductive whiskers such as zinc oxide or potassium titanate, (vii) Conductive metal oxides such as titanium oxide, or (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene, Therefore, to reduce costs, the conductive additives described in (i) or (ii) above may be used.

[0105] Examples of battery shapes according to the second embodiment include coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked types.

[0106] The battery according to the second embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and then fabricating a laminate in which the positive electrode, electrolyte layer, and negative electrode are arranged in that order by a known method. [Examples]

[0107] The present disclosure will be described in more detail below with reference to examples and comparative examples.

[0108] <Example 1> (Preparation of solid electrolyte materials) In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as a "dry argon atmosphere"), LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. These raw material powders, along with 1 mmΦ balls (25 g), were placed in a 45 cc pod for a planetary ball mill. γ-butyrolactone (GBL) was added dropwise to the pod as an organic solvent to achieve a solid content ratio of 50%. Here, the solid content ratio is calculated as {(mass of raw materials) / (mass of raw materials + mass of solvent)} × 100. Milling was performed using a planetary ball mill at 500 rpm for 12 hours. After milling, the balls were separated to obtain a slurry. The obtained slurry was dried at 200°C for 1 hour under a nitrogen flow using a mantle heater. The obtained solid material was ground in a mortar to obtain the powder of the solid electrolyte material according to Example 1. The solid electrolyte material according to Example 1 is Li 2.8 Zr 0.2 Al 0.8 It had a composition represented by F6.

[0109] (Evaluation of ionic conductivity) Figure 2 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material.

[0110] The pressure forming die 300 comprised a punch upper section 301, a frame 302, and a punch lower section 303. The frame 302 was formed from insulating polycarbonate. The punch upper section 301 and the punch lower section 303 were formed from electronically conductive stainless steel.

[0111] Using the pressure molding die 300 shown in Figure 2, the ionic conductivity of the solid electrolyte material according to Example 1 was evaluated by the following method.

[0112] In a dry atmosphere having a dew point of -30°C or lower, the powder of the solid electrolyte material according to Example 1 was filled into the inside of a pressure molding die 300. Inside the pressure molding die 300, a pressure of 400 MPa was applied to the solid electrolyte material according to Example 1 using the upper part of the punch 301 and the lower part of the punch 303.

[0113] With pressure still applied, the upper part 301 and lower part 303 of the punch were connected to a potentiostat (BioLogic, VSP300) equipped with a frequency response analyzer. The upper part 301 of the punch was connected to the working electrode and potential measurement terminals. The lower part 303 of the punch was connected to the counter electrode and reference electrode. The impedance of the solid electrolyte material was measured at room temperature using electrochemical impedance measurement.

[0114] Figure 3 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1.

[0115] 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 to ion conduction of the solid electrolyte material. This real value is indicated by the arrow R in Figure 3. SE Refer to [reference]. Using the resistance value, the ionic conductivity was calculated based on the following formula (2).

[0116] σ=(R SE ×S / t) -1 ...(2) Here, σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper part 301 of the punch. That is, S is equal to the cross-sectional area of ​​the hollow part of the frame 302 in Figure 2. SE t represents the resistance value of the solid electrolyte material in impedance measurement. t represents the thickness of the solid electrolyte material. That is, in Figure 2, t represents the thickness of the layer formed from the powder 101 of the solid electrolyte material.

[0117] The ionic conductivity of the solid electrolyte material according to Example 1, measured at 25°C, was 4.92 × 10⁻⁶.-7 The value was S / cm.

[0118] (Measurement of specific surface area) A specific surface area / pore distribution analyzer (BELSORP MINI X, manufactured by Microtrac-BEL) was used to measure the specific surface area. Hereafter, the specific surface area obtained using this analyzer will be referred to as the BET specific surface area.

[0119] In an atmospheric environment with a dew point of -40°C or lower, approximately 1 g of the solid electrolyte material powder from Example 1 was placed in a dedicated test tube.

[0120] As a pretreatment, the material was vacuum-dried at 80°C for 1 hour.

[0121] The mass added was measured by the difference between the weight of the test tube containing the sample after pretreatment and the weight of the test tube before the sample was added.

[0122] BET specific surface area measurements were performed using pre-treated test tubes, and the specific surface area of ​​the solid electrolyte material according to Example 1 was 13.03 m². 2 It was / g.

[0123] (Battery construction) In a dry argon atmosphere, the solid electrolyte material and the active material LiCoO2 according to Example 1 were prepared in a volume ratio of 30:70. These materials were mixed in an agate mortar. In this way, a cathode mixture was obtained.

[0124] In an insulating cylinder with an inner diameter of 9.5 mm, Li3PS4 (57.41 mg), the solid electrolyte material according to Example 1 (26 mg), and the above-mentioned positive electrode mixture (9.1 mg) were layered in this order. A pressure of 300 MPa was applied to the resulting laminate to form a first electrolyte layer, a second electrolyte layer, and a positive electrode. That is, the second electrolyte layer formed from the solid electrolyte material according to Example 1 was sandwiched between the first electrolyte layer and the positive electrode. The thicknesses of the first and second electrolyte layers were 450 μm and 150 μm, respectively.

[0125] Next, metallic Li (thickness: 200 μm) was laminated onto the first electrolyte layer. A pressure of 80 MPa was applied to the resulting laminate to form a negative electrode.

[0126] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collector leads were attached to the current collectors.

[0127] Finally, an insulating ferrule was used to isolate the inside of the insulating cylinder from the outside atmosphere, thereby sealing the inside of the cylinder. In this way, the battery according to Example 1 was obtained.

[0128] (Charge / Discharge Test) Figure 4 is a graph showing the initial discharge characteristics of the battery according to Example 1. The initial charge-discharge characteristics were measured by the following method.

[0129] The battery according to Example 1 was placed in a constant temperature bath at 85°C.

[0130] 13.5 μA / cm 2 The battery according to Example 1 was charged to a voltage of 4.2V at a current density of 0.01C.

[0131] Next, 13.5 μA / cm 2 The battery according to Example 1 was discharged until it reached a voltage of 2.5V at the given current density.

[0132] The charge-discharge test results showed that the battery according to Example 1 had an initial discharge capacity of 943 μAh.

[0133] <Examples 2 to 13> (Preparation of solid electrolyte materials) In Examples 2 to 13, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8.

[0134] The solvent, solid content ratio, ball diameter, ball quantity, processing time, and drying conditions for the milling process are shown in Table 1.

[0135] Solid electrolyte materials according to Examples 2 to 13 were obtained in the same manner as in Example 1, except for the conditions shown in Table 1.

[0136] (Evaluation of ionic conductivity) The ionic conductivity of the solid electrolyte materials in Examples 2 to 13 was measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0137] (Measurement of specific surface area) The BET specific surface area was measured using the solid electrolyte materials from Examples 2 to 13 in the same manner as in Example 1. The measurement results are shown in Table 1.

[0138] (Charge / Discharge Test) Using the solid electrolyte materials from Examples 2 to 13, batteries according to Examples 2 to 13 were obtained in the same manner as in Example 1.

[0139] A charge-discharge test was performed using the batteries from Examples 2 to 13 in the same manner as in Example 1. As a result, the batteries from Examples 2 to 13 charged and discharged well, similar to the battery from Example 1.

[0140] <Reference example 1> In a dry argon atmosphere, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. These raw material powders were ground and mixed in a mortar. The resulting mixture was placed in a 45cc pod for a planetary ball mill along with a 5mmΦ ball (25g). The mixture was milled using a planetary ball mill at 500rpm for 12 hours. In this way, the solid electrolyte material according to Reference Example 1 was obtained.

[0141] As described above, the solid electrolyte material according to Reference Example 1 was prepared using a dry ball mill without the use of organic solvents.

[0142] Using the solid electrolyte material according to Reference Example 1, ionic conductivity and specific surface area were measured in the same manner as in Example 1.

[0143] The ionic conductivity measured at 25°C was 4.78 × 10⁻⁶. -7 The value was S / cm.

[0144] The measured specific surface area was 3.14 m². 2 It was / g.

[0145] <Comparative Example 1> LiBF4 was used as the solid electrolyte material, and the ionic conductivity was measured in the same manner as in Example 1. As a result, the ionic conductivity measured at 25°C was 6.67 × 10⁻⁶. -9 The value was S / cm.

[0146] A battery according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the solid electrolyte material from Comparative Example 1 was used as the solid electrolyte for the positive electrode mixture and the electrolyte layer.

[0147] A charge-discharge test was performed using the battery from Comparative Example 1 in the same manner as in Example 1.

[0148] The initial discharge capacity of the battery in Comparative Example 1 was 0.01 μAh or less. In other words, the battery in Comparative Example 1 neither charged nor discharged.

[0149] [Table 1]

[0150] <Consideration> The solid electrolyte materials according to Examples 1 to 13 have a capacitance of 7 × 10 at room temperature. -9 It has an ionic conductivity of S / cm or higher, and is 3.2m 2 It has a specific surface area of ​​1 / g or more. On the other hand, the specific surface area of ​​the solid electrolyte material according to Reference Example 1, which was manufactured using a dry ball mill, is 3.14 m². 2 It was a small value of / g.

[0151] The batteries from Examples 1 to 13 were all charged and discharged at 85°C. On the other hand, the battery from Comparative Example 1 was neither charged nor discharged.

[0152] The solid electrolyte materials according to Examples 1 to 13 do not contain sulfur, and therefore do not generate hydrogen sulfide.

[0153] As described above, the solid electrolyte material according to this disclosure is suitable for providing a battery that has high lithium-ion conductivity and can be charged and discharged well. [Industrial applicability]

[0154] The solid electrolyte material of this disclosure can be used, for example, in all-solid-state lithium-ion secondary batteries. [Explanation of symbols]

[0155] 100 solid electrolyte 101 Powder of solid electrolyte material 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 204 Cathode active material 205 Anode active material 300 pressure molding dies 301 Punch Top 302 Frame type 303 Punch bottom 1000 batteries

Claims

1. A solid electrolyte material comprising Li, Zr, Al, and F, The specific surface area of ​​the solid electrolyte material is 3.2 m². 2 Greater than / g, The solid electrolyte material is represented by the following compositional formula (1): Li 6-(4-x)b (Zr 1-x Al x ) b F 6 ... (1) Here, the conditions 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. Solid electrolyte material.

2. The aforementioned specific surface area is 100 m². 2 Less than / g The solid electrolyte material according to claim 1.

3. The aforementioned specific surface area is 40 m². 2 Less than / g The solid electrolyte material according to claim 2.

4. The aforementioned specific surface area is 5.2 m². 2 It is 1 / g or more. The solid electrolyte material according to claim 1.

5. A method for producing a solid electrolyte material according to any one of claims 1 to 4, The process includes a wet grinding step of grinding a mixture containing a raw material composition comprising the components of the solid electrolyte material and a solvent. A method for manufacturing solid electrolyte materials.

6. The raw material composition contains LiF, The manufacturing method according to claim 5.

7. The solvent comprises at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetralin. The manufacturing method according to claim 5.

8. positive electrode, Negative electrode, and An electrolyte layer provided 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 described in any one of claims 1 to 4. battery.

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