Solid electrolyte materials and batteries using the same

Abstract

A solid electrolyte material according to the present disclosure contains Li, M, O, X and S. Meanwhile, M represents at least one element that is selected from the group consisting of Ti, Zr and Hf. X represents at least one element that is selected from the group consisting of F, Cl, Br, and I. The molar ratio of the O to the X is more than 0 but not more than 0.3. A battery 1000 according to the present disclosure comprises a positive electrode 201, a negative electrode 203, and an electrolyte layer 202 that is arranged between the positive electrode 201 and the negative electrode 203. At least one member selected from the group consisting of the positive electrode 201, the negative electrode 203 and the electrolyte layer 202 contains the solid electrolyte material according to the present disclosure.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a solid electrolyte material represented by Li 6-4a M a X6. M is at least one selected from the group consisting of Zr, Hf, and Ti. X is a halogen element. The mathematical formula: 0 < a < 1.5 is satisfied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a novel solid electrolyte material with high utility.

Means for Solving the Problems

[0005] The solid electrolyte material of the present disclosure contains Li, M, O, X, and S, where M is at least one selected from the group consisting of Ti, Zr, and Hf, X is at least one selected from the group consisting of F, Cl, Br, and I, the molar ratio of O to X is more than 0 and 0.3 or less.

Effects of the Invention

[0006] The present disclosure provides a novel solid electrolyte material with high utility.

Brief Description of the Drawings

[0007] [Figure 1] FIG. 1 shows a cross-sectional view of a battery 1000 according to the second embodiment. [Figure 2] FIG. 2 shows a cross-sectional view of an electrode material 1100 according to the second embodiment. [Figure 3] FIG. 3 shows a schematic diagram of a compression molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material. [Figure 4] FIG. 4 is a graph showing the initial discharge characteristics of the battery according to Example 1.

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0009] (First Embodiment) The solid electrolyte material according to the first embodiment contains Li, M, O, X, and S. M is at least one selected from the group consisting of Ti, Zr, and Hf. X is at least one selected from the group consisting of F, Cl, Br, and I, and the molar ratio of O to X is greater than 0 and less than or equal to 0.3.

[0010] The solid electrolyte material according to the first embodiment is, for example, a new solid electrolyte material highly useful for lithium ion conduction. The solid electrolyte material according to the first embodiment can have, for example, a practical lithium ion conductivity, and can have, for example, a high lithium ion conductivity.

[0011] Here, the high lithium ion conductivity means, for example, 1.0 mS / cm or more in the vicinity of room temperature. That is, the solid electrolyte material according to the first embodiment can have an ionic conductivity of, for example, 1.0 mS / cm or more.

[0012] The solid electrolyte material according to the first embodiment can be used to obtain a battery having excellent charge-discharge characteristics. An example of such a battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0013] The solid electrolyte material according to the first embodiment can maintain high lithium-ion conductivity within the expected operating temperature range of the battery (for example, from -30°C to 80°C). Therefore, a battery using the solid electrolyte material according to the first embodiment can operate stably even in environments with temperature fluctuations.

[0014] To increase the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist substantially of Li, M, O, X, and S. Here, "the solid electrolyte material according to the first embodiment consists substantially of Li, M, O, X, and S" means that the molar ratio (i.e., mole fraction) of the total amount of substance of Li, M, O, X, and S to the total amount of substance of all elements constituting the solid electrolyte material according to the first embodiment is 90% or more. As an example, this molar ratio may be 95% or more.

[0015] To increase the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist only of Li, M, O, X, and S.

[0016] To increase the ionic conductivity of the solid electrolyte material, M may contain Zr.

[0017] To increase the ionic conductivity of the solid electrolyte material, X may contain Cl. X may also be Cl.

[0018] In the following, the molar ratio of Li to M may be written as "Li / M". The molar ratio of O to X may be written as "O / X". The molar ratio of S to M may be written as "S / M".

[0019] Li / M is calculated using the formula: (amount of Li) / (total amount of Ti, Zr, and Hf). O / X is calculated using the formula: (amount of O) / (total amount of F, Cl, Br, and I). S / M is calculated using the formula: (amount of S) / (total amount of Ti, Zr, and Hf).

[0020] The upper and lower limits of Li / M can be defined by any combination selected from the values ​​1.0, 1.2, 1.6, 2.0, 2.4, and 3.0.

[0021] The Li / M ratio may be between 1.0 and 3.0. This optimizes the concentration of Li, which is a conduction carrier. As a result, the solid electrolyte material according to the first embodiment has high ionic conductivity. To further increase the ionic conductivity of the solid electrolyte material, the Li / M ratio may be between 1.2 and 2.4. To further increase the ionic conductivity of the solid electrolyte material, the Li / M ratio may be between 1.6 and 2.4.

[0022] The upper and lower limits of O / X can be defined by any combination selected from the following values: greater than 0, 0.05, 0.08, 0.11, 0.13, 0.15, 0.16, 0.17, 0.24, and 0.3.

[0023] The upper and lower limits of S / M can be defined by any combination selected from the values ​​greater than 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7.

[0024] The O / X ratio may be 0.05 or higher and 0.3 or lower. This facilitates the formation of pathways for lithium ion diffusion. As a result, the solid electrolyte material according to the first embodiment has high lithium ion conductivity. The O / X ratio may be 0.05 or higher and 0.24 or lower.

[0025] S / M may be 0.1 or more and 0.7 or less. This makes it easier to form a path for lithium ions to diffuse. As a result, the solid electrolyte material according to the first embodiment has high lithium ion conductivity. In order to increase the ion conductivity of the solid electrolyte material, S / M may be 0.2 or more and 0.5 or less.

[0026] The solid electrolyte material according to the first embodiment may be crystalline or amorphous.

[0027] The solid electrolyte material according to the first embodiment may be amorphous. An amorphous solid electrolyte has advantages such as no crystal orientation anisotropy in ion conduction, little influence of grain boundaries, and less likelihood of deterioration of ion conductivity after processing such as further pulverization.

[0028] The solid electrolyte material according to the first embodiment may contain a crystal phase. The crystal phase is derived from, for example, LiX or Li 6-4a M a X6 (the mathematical formula: 0 < a < 1.5 is satisfied).

[0029] The solid electrolyte material according to the first embodiment may contain both an amorphous phase and a crystal phase, or may contain only one of them. The microstructure of the solid electrolyte material can be examined by X-ray diffraction measurement.

[0030] The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of the shape are needle-like, 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 a pellet or a plate.

[0031] If the solid electrolyte material according to the first embodiment is particulate (for example, spherical), the solid electrolyte material may have a median diameter of 0.1 μm or more and 100 μm or less, or a median diameter of 0.5 μm or more and 10 μm or less. This allows the solid electrolyte material according to the first embodiment and other materials to be dispersed well. The median diameter of the particles refers to the particle size (d50) corresponding to 50% of the volume cumulative in the volume-based particle size distribution. The volume-based particle size distribution can be measured by a laser diffraction measuring device or an image analysis device.

[0032] <Method for manufacturing solid electrolyte materials> The solid electrolyte material according to the first embodiment can be manufactured by the following method.

[0033] The raw material powder is prepared to have the desired composition. Examples of raw material powders include oxides, hydroxides, halides, or acid halides.

[0034] As an example, consider a solid electrolyte material composed of Li, Zr, O, Cl, and S (where M is Zr and X is Cl), where the molar ratio Li / M is 1.6, the molar ratio O / X is 0.175, and the molar ratio S / M is 0.2. In this case, Li2O, LiOH, ZrCl4, and Li2S are mixed in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.5:0.2:1:0.2. M and X are determined by the selection of raw material powders. The molar ratios of Li / M, O / X, and S / M are determined by selecting the mixing ratio of the raw material powders. The raw material powders may be mixed in pre-adjusted molar ratios to offset any compositional changes that may occur during the synthesis process.

[0035] The reaction product is obtained by calcining a mixture of raw material powders. To suppress the evaporation of the raw materials during calcination, the mixture of raw material powders may be sealed in an airtight container made of quartz glass or borosilicate glass and calcined under vacuum or an inert gas atmosphere. The inert gas atmosphere may be, for example, an argon atmosphere or a nitrogen atmosphere.

[0036] Alternatively, the mixture of raw material powders may be reacted mechanochemically with each other in a mixing device such as a planetary ball mill to obtain a reactant. In other words, the raw material powders may be mixed and reacted using a mechanochemical milling method. By these methods, the solid electrolyte material according to the first embodiment can be obtained.

[0037] When a mixture of raw material powders is calcined or reacted mechanochemically, some of the oxygen may evaporate from the raw material powders. As a result, the molar ratio O / X of the solid electrolyte material may be smaller than the O / X value calculated from the molar ratio of the raw material powders.

[0038] The composition of solid electrolyte materials can be determined, for example, by ICP emission spectroscopy, ion chromatography, inert gas fusion-infrared absorption spectroscopy, or EPMA (Electron Probe Micro Analyzer). For instance, the compositions of Li and M may be determined by ICP emission spectroscopy, the composition of X by ion chromatography, O by inert gas fusion-infrared absorption spectroscopy, and the composition of S by EPMA.

[0039] (Second Embodiment) The second embodiment is described below. Matters described in the first embodiment may be omitted as appropriate.

[0040] The battery according to the second embodiment comprises a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is positioned between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode, the electrolyte layer, and the negative electrode contains the solid electrolyte material according to the first embodiment.

[0041] 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.

[0042] Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment.

[0043] The battery 1000 comprises a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is located between the positive electrode 201 and the negative electrode 203.

[0044] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100.

[0045] The electrolyte layer 202 contains an electrolyte material.

[0046] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

[0047] The solid electrolyte particles 100 are particles containing the solid electrolyte material according to the first embodiment. The solid electrolyte particles 100 may also be particles that mainly contain the solid electrolyte material according to the first embodiment. Particles that mainly contain the solid electrolyte material according to the first embodiment 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 particles 100 may also be particles made of the solid electrolyte material according to the first embodiment.

[0048] The positive electrode 201 contains a material capable of intercalating and releasing metal ions such as lithium ions. The positive electrode 201 also contains, for example, a positive electrode active material (e.g., positive electrode active material particles 204).

[0049] Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O2, Li(Ni,Co,Mn)O2, or LiCoO2.

[0050] In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0051] From the standpoint of battery cost and safety, lithium phosphate may be used as the positive electrode active material.

[0052] When the positive electrode 201 contains the solid electrolyte material according to the first embodiment and X contains I (i.e., iodine), lithium iron phosphate may be used as the positive electrode active material. The solid electrolyte material according to the first embodiment containing I is liable to be oxidized. If lithium iron phosphate is used as the positive electrode active material, the oxidation reaction of the solid electrolyte material is suppressed. That is, the formation of an oxide layer having low lithium ion conductivity is suppressed. As a result, the battery has high charge-discharge efficiency.

[0053] The positive electrode 201 may contain not only the solid electrolyte material according to the first embodiment but also a transition metal oxyfluoride as the positive electrode active material. Even if the solid electrolyte material according to the first embodiment is fluorinated by the transition metal fluoride, it is difficult to form a resistance layer. As a result, the battery has high charge-discharge efficiency.

[0054] The transition metal oxyfluoride contains oxygen and fluorine. As an example, the transition metal oxyfluoride has a composition formula Li p Me q O m F n and may be a compound represented by. Here, Me is at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and the mathematical formulas: 0.5 ≦ p ≦ 1.5, 0.5 ≦ q ≦ 1.0, 1 ≦ m < 2, and 0 < n ≦ 1 are satisfied. An example of such a transition metal oxyfluoride is Li 1.05 (Ni 0.35 Co 0.35 Mn 0.3 ) 0.95 O 1.9 F 0.1 is.

[0055] The positive electrode active material particles 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median diameter of 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 100 can form a good dispersion state in the positive electrode 201. This improves the charge and discharge characteristics of the battery. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles 204 is improved. This allows the battery to operate at high power.

[0056] The positive electrode active material particles 204 may have a larger median diameter than the solid electrolyte particles 100. This allows the positive electrode active material particles 204 and the solid electrolyte particles 100 to form a good dispersion state.

[0057] To increase the energy density and output of the battery, the ratio of the volume of the positive electrode active material particles 204 to the sum of the volume of the positive electrode active material particles 204 and the volume of the solid electrolyte particles 100 in the positive electrode 201 may be 0.30 or more and 0.95 or less.

[0058] Figure 2 shows a cross-sectional view of the electrode material 1100 according to the second embodiment. The electrode material 1100 is included, for example, in the positive electrode 201. To prevent the solid electrolyte particles 100 from reacting with the positive electrode active material (i.e., electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This can suppress the rise in the reaction overpotential of the battery. Examples of coating materials included in the coating layer 216 are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes.

[0059] When the solid electrolyte particles 100 are a solid electrolyte material according to the first embodiment and X contains I, the coating material may also be a solid electrolyte material according to the first embodiment, and X may be at least one selected from the group consisting of Cl and Br. The solid electrolyte material according to the first embodiment that does not contain I is less susceptible to oxidation than the solid electrolyte material according to the first embodiment that contains I. As a result, the battery has high charge and discharge efficiency.

[0060] If the solid electrolyte particles 100 are a solid electrolyte material according to the first embodiment and X contains I, the coating material may also contain an oxide solid electrolyte. The oxide solid electrolyte may be lithium niobate, which has excellent stability even at high potentials. This results in a battery with high charge and discharge efficiency.

[0061] The positive electrode 201 may consist of a first positive electrode layer containing a first positive electrode active material and a second positive electrode layer containing a second positive electrode active material. Here, the second positive electrode layer is positioned between the first positive electrode layer and the electrolyte layer 202, and both the first and second positive electrode layers contain a solid electrolyte material according to the first embodiment, including I, and a coating layer 216 is formed on the surface of the second positive electrode active material. With this configuration, oxidation of the solid electrolyte material according to the first embodiment contained in the electrolyte layer 202 by the second positive electrode active material can be suppressed. As a result, the battery has a high charging capacity. Examples of coating materials contained in the coating layer 216 are sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes. However, if the coating material is a halide solid electrolyte, it does not contain I as a halogen element. The first positive electrode active material may be the same material as the second positive electrode active material, or it may be a different material from the second positive electrode active material.

[0062] To increase the energy density and output of the battery, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0063] The electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may be a solid electrolyte layer. The electrolyte layer 202 may contain a solid electrolyte material according to the first embodiment. The electrolyte layer 202 may consist only of a 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 solid electrolyte material according to the first embodiment 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. The first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed in the electrolyte layer 202. 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 electrolyte layer 202 may consist solely of the second solid electrolyte material.

[0067] The electrolyte layer 202 may have a thickness of 1 μm or more and 100 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 100 μm or less, the battery can operate at high power.

[0068] An additional electrolyte layer may be provided between the electrolyte layer 202 and the negative electrode 203. That is, a second electrolyte layer may be provided between the electrolyte layer 202 and the negative electrode 203. For example, if the electrolyte layer 202 contains a first solid electrolyte material, the second electrolyte layer may be composed of another solid electrolyte material that is electrochemically more stable than the first solid electrolyte material. Specifically, the reduction potential of the solid electrolyte material constituting the second electrolyte layer may be lower than the reduction potential of the first solid electrolyte material. This allows the first solid electrolyte material to be used without reduction. As a result, the charge and discharge efficiency of the battery can be improved.

[0069] The negative electrode 203 contains a material capable of intercalating and releasing metal ions such as lithium ions. The negative electrode 203 also contains, for example, a negative electrode active material (e.g., negative electrode active material particles 205).

[0070] Examples of negative electrode active materials include metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. Metallic materials may be elemental metals or alloys. Examples of metallic materials include lithium metal or lithium alloys. Examples of carbon materials include 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.

[0071] The negative electrode active material may be selected based on the reduction resistance of the solid electrolyte material contained in the negative electrode 203. If the negative electrode 203 contains a first solid electrolyte material, a material capable of intercalating and releasing lithium ions at 1.6V or higher relative to lithium may be used as the negative electrode active material. If the negative electrode active material is such a material, the reduction of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the battery has high charge and discharge efficiency. Examples of such materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12 It is either LiTi2O4 or TiO2.

[0072] The negative electrode active material particles 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median diameter of 0.1 μm or more, the negative electrode active material particles 205 and the solid electrolyte particles 100 can form a good dispersion state in the negative electrode 203. This improves the charge and discharge characteristics of the battery. When the negative electrode active material particles 205 have a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material particles 205 is improved. This allows the battery to operate at high power.

[0073] The negative electrode active material particles 205 may have a larger median diameter than the solid electrolyte particles 100. This allows the negative electrode active material particles 205 and the solid electrolyte particles 100 to form a good dispersion state.

[0074] To increase the energy density and output of the battery, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the sum of the volume of the negative electrode active material particles 205 and the volume of the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0075] The electrode material 1100 shown in Figure 2 may be contained in the negative electrode 203. To prevent the solid electrolyte particles 100 from reacting with the negative electrode active material (i.e., electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This gives the battery high charge and discharge efficiency. Examples of coating materials included in the coating layer 216 are sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes.

[0076] When the solid electrolyte particles 100 are the first solid electrolyte material, the coating material may be an oxide solid electrolyte or a polymer solid electrolyte. An example of an oxide solid electrolyte is trilithium phosphate. An example of a polymer solid electrolyte is a composite compound of polyethylene oxide and lithium salt. An example of such a polymer solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0077] To increase the energy density and output of the battery, 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 the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a second solid electrolyte material for the purpose of enhancing ionic conductivity. Examples of the second solid electrolyte material are sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, or organic polymer solid electrolytes.

[0079] In this disclosure, "sulfide solid electrolyte" means a solid electrolyte containing sulfur as the main component of its anions. "Oxide solid electrolyte" means a solid electrolyte containing oxygen as the main component of its anions. "Halide solid electrolyte" means a solid electrolyte containing a halogen element as the main component of its anions. The main component of anions means the anion with the largest amount of substance among all the anions that make up the 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] 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 derivative That is the case.

[0082] An example of a solid halide electrolyte is Li a Me' b Y c This is a compound represented by Z6. Here, the equation a + mb + 3c = 6 and c > 0 are satisfied. Me' is at least one element selected from the group consisting of metallic elements other than Li and Y and metalloid elements. Z is at least one element selected from the group consisting of F, Cl, Br, and I. The value of m represents the valence of Me'.

[0083] "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).

[0084] To increase 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.

[0085] Examples of solid halide electrolytes are Li3YCl6 or Li3YBr6.

[0086] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds. 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 have higher ionic conductivity.

[0087] 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.

[0088] 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 for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery.

[0089] Non-aqueous electrolytes include a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents are cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorine 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. Examples of 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 include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0090] 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 / liter to 2 mol / liter.

[0091] As the gel electrolyte, polymer materials impregnated with a non-aqueous electrolyte can be used. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds.

[0092] 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 pyridiniums or imidazoliums That is the case.

[0093] An example of anion found in ionic liquids is PF6. - BF4 - SbF6 - AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case.

[0094] The ionic liquid may contain a lithium salt.

[0095] 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 for the purpose of improving the adhesion between particles.

[0096] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, or carboxymethylcellulose. Copolymers may also be used as binders. Examples of such binders include copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures of two or more materials selected from the above materials may also be used.

[0097] At least one selected from the group consisting of a positive electrode 201 and a negative electrode 203 may contain a conductive additive for the purpose of enhancing electronic conductivity.

[0098] 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.

[0099] Examples of battery shapes according to the second embodiment include coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked types.

[0100] 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]

[0101] The present disclosure will be described in more detail below with reference to examples and comparative examples.

[0102] (Example 1) [Fabrication of Solid Electrolyte Materials] In a dry atmosphere with a dew point of -30°C or lower (hereinafter referred to as the "dry atmosphere"), Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.5:0.2:1:0.2. These raw material powders were mixed in a mortar to obtain a mixed powder. The obtained mixed powder was milled using a planetary ball mill at 600 rpm for 24 hours. In this way, the solid electrolyte material according to Example 1 was obtained.

[0103] [Compositional analysis of solid electrolyte materials] The Li and Zr content of the solid electrolyte material obtained in Example 1 was measured by inductively coupled plasma atomic emission spectroscopy using a high-frequency inductively coupled plasma atomic emission spectrometer (ThermoFisher Scientific, iCAP7400). The Cl content was measured by ion chromatography using an ion chromatograph (Dionex, ICS-2000). The O content was measured by inert gas fusion-infrared absorption using an oxygen analyzer (Horiba, EMGA-930). From the measurement results, the molar ratios Li / M, O / X, and S / M were calculated. Here, the amount of S used was adopted as the S content.

[0104] In the solid electrolyte material according to Example 1, the molar ratio Li / M was 1.6, the molar ratio O / X was 0.16, and the molar ratio S / M was 0.2.

[0105] [Evaluation of ionic conductivity] Figure 3 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material.

[0106] 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. Both the punch upper section 301 and the punch lower section 303 were formed from electronically conductive stainless steel.

[0107] Using the pressure molding die 300 shown in Figure 3, the ionic conductivity of the solid electrolyte material according to Example 1 was measured by the following method.

[0108] In a dry atmosphere, the powder of the solid electrolyte material according to Example 1 (i.e., the powder of the solid electrolyte material 101 in Figure 3) was filled into the inside of the pressure molding die 300. Inside the pressure molding die 300, a pressure of 300 MPa was applied to the solid electrolyte material according to Example 1 using the upper part of the punch 301. In this way, the evaluation cell according to Example 1 was obtained.

[0109] With pressure still applied to the evaluation cell, the upper part 301 and lower part 303 of the punch were connected to a potentiostat (VersaSTAT4, Princeton Applied Research) 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 ionic conductivity of the solid electrolyte material according to Example 1 was measured at room temperature using electrochemical impedance measurement. As a result, the ionic conductivity measured at 22°C was 2.0 mS / cm.

[0110] [Battery construction] In an argon atmosphere with a dew point of -60°C or lower, the solid electrolyte material and LiCoO2 according to Example 1 were prepared in a volume ratio of solid electrolyte material:LiCoO2 = 30:70. These materials were mixed in an agate mortar. In this way, a positive electrode mixture was obtained.

[0111] A laminate was obtained by laminating the solid electrolyte material (80 mg) and positive electrode mixture (8.2 mg) according to Example 1 in an insulating cylinder having an inner diameter of 9.5 mm. A pressure of 360 MPa was applied to this laminate to form a solid electrolyte layer and a positive electrode. The solid electrolyte layer had a thickness of 500 μm.

[0112] Next, a Li-In alloy (thickness: 200 μm) was laminated onto the solid electrolyte layer. A pressure of 80 MPa was applied to this laminate to form a negative electrode.

[0113] 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.

[0114] 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.

[0115] Thus, the battery according to Example 1 was obtained.

[0116] [Charge / Discharge Test] Figure 4 is a graph showing the initial discharge characteristics of the battery according to Example 1. The horizontal axis represents the discharge capacity, and the vertical axis represents the voltage. The results shown in Figure 4 were measured by the following method.

[0117] The battery according to Example 1 was placed in a constant temperature bath maintained at 25°C.

[0118] The battery according to Example 1 was charged at a current value that corresponds to a 0.05C rate (20-hour rate) relative to the battery's theoretical capacity until it reached a voltage of 3.6V. Next, the battery according to Example 1 was discharged at a current value that corresponds to a 0.05C rate until it reached a voltage of 1.9V.

[0119] The charge-discharge test results showed that the battery according to Example 1 had an initial discharge capacity of 0.68 mAh.

[0120] (Examples 2 to 9 and Comparative Example 1) [Fabrication of Solid Electrolyte Materials] In Example 2, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.4:0.2:1:0.3.

[0121] In Example 3, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.2:0.2:1:0.5.

[0122] In Example 4, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of LiOH:ZrCl4:Li2S = 0.2:1:0.7.

[0123] In Example 5, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.6:0.2:1:0.1.

[0124] In Example 6, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.9:0.2:1:0.2.

[0125] In Example 7, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.7:0.2:1:0.2.

[0126] In Example 8, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.3:0.2:1:0.2.

[0127] In Example 9, Li2O, LiOH, ZrCl4, and Li2S were prepared as raw material powders in a molar ratio of Li2O:LiOH:ZrCl4:Li2S = 0.5:0.2:1:0.4.

[0128] In Comparative Example 1, LiCl and ZrCl4 were prepared as raw material powders in a molar ratio of LiCl:ZrCl4 = 2:1.

[0129] Except for the matters described above, solid electrolyte materials according to Examples 2 to 9 and Comparative Example 1 were obtained in the same manner as in Example 1.

[0130] [Compositional analysis of solid electrolyte materials] The composition of the solid electrolyte materials from Examples 2 to 9 and Comparative Example 1 was analyzed in the same manner as in Example 1.

[0131] In Example 2, the molar ratio Li / M of the solid electrolyte material was 1.6. The molar ratio O / X was 0.13. The molar ratio S / M was 0.3.

[0132] The molar ratio Li / M of the solid electrolyte material in Example 3 was 1.6. The molar ratio O / X was 0.08. The molar ratio S / M was 0.5.

[0133] In Example 4, the molar ratio Li / M of the solid electrolyte material was 1.6. The molar ratio O / X was 0.05. The molar ratio S / M was 0.7.

[0134] In Example 5, the molar ratio Li / M of the solid electrolyte material was 1.6. The molar ratio O / X was 0.17. The molar ratio S / M was 0.1.

[0135] The molar ratio Li / M of the solid electrolyte material in Example 6 was 2.4. The molar ratio O / X was 0.24. The molar ratio S / M was 0.2.

[0136] The molar ratio Li / M of the solid electrolyte material in Example 7 was 2.0. The molar ratio O / X was 0.19. The molar ratio S / M was 0.2.

[0137] In Example 8, the molar ratio Li / M of the solid electrolyte material was 1.2. The molar ratio O / X was 0.11. The molar ratio S / M was 0.2.

[0138] In Example 9, the molar ratio Li / M of the solid electrolyte material was 2.0. The molar ratio O / X was 0.15. The molar ratio S / M was 0.4.

[0139] The molar ratio Li / M of the solid electrolyte material in Comparative Example 1 was 2.0. The molar ratios O / X and S / M were both 0.

[0140] [Evaluation of ionic conductivity] The ionic conductivity of the solid electrolyte materials from Examples 2 to 9 and Comparative Example 1 was measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0141] [Table 1]

[0142] (Consideration) As is clear from Table 1, the solid electrolyte materials according to Examples 1 to 9 have high ionic conductivity of 1.0 mS / cm or more at or near room temperature.

[0143] As is clear from comparing Examples 1 to 7 and 9 with Example 8, if the molar ratio Li / M is between 1.6 and 2.4, the solid electrolyte material has higher ionic conductivity. As is clear from comparing Examples 1 to 3 and Examples 4 and 5, which have the same Li / M value, if the molar ratio S / M is between 0.2 and 0.5, the solid electrolyte material has higher ionic conductivity.

[0144] Ti, Zr, and Hf are all transition metal elements belonging to Group 4. Therefore, it is presumed that the desired effect can be obtained even if some or all of Zr is replaced with at least one selected from the group consisting of Ti and Hf. Similarly, it is presumed that the desired effect can be obtained even if some or all of the halogen element Cl is replaced with at least one selected from the group consisting of F, Br, and I.

[0145] The battery according to Example 1 was charged and discharged at room temperature.

[0146] As described above, the solid electrolyte material according to this disclosure is a highly useful material that can improve, for example, lithium ion conductivity, and is suitable for providing a battery that can be charged and discharged well. [Industrial applicability]

[0147] The solid electrolyte material of this disclosure can be used, for example, in all-solid-state lithium-ion secondary batteries.

Claims

1. Including Li, M, O, X, and S, Here, M is at least one selected from the group consisting of Ti, Zr, and Hf. X is at least one selected from the group consisting of F, Cl, Br, and I. The molar ratio of O to X is 0.05 or greater and 0.24 or less. The molar ratio of Li to M is 1.2 or greater and 2.4 or less. The molar ratio of S to M is 0.1 or greater and 0.7 or less. Solid electrolyte material.

2. M includes Zr, The solid electrolyte material according to claim 1.

3. X contains Cl, The solid electrolyte material according to claim 1 or 2.

4. The molar ratio of Li to M is 1.6 or greater and 2.4 or less. The solid electrolyte material according to any one of claims 1 to 3.

5. The molar ratio of S to M is 0.2 or greater and 0.5 or less. A solid electrolyte material according to any one of claims 1 to 4.

6. positive electrode, Negative electrode, and An electrolyte layer disposed between the positive electrode and the negative electrode, Equipped with, At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material described in any one of claims 1 to 5. battery.

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