Solid electrolyte material and battery using the same

Abstract

The solid electrolyte material of the present disclosure contains Li, M, O, X, and A, where M is at least one selected from Ti, Zr, and Hf, X is at least one selected from F, Cl, Br, and I, A is at least one selected from P and B, the molar ratio of Li to M is 1.0 or greater and 3.0 or less, the molar ratio of O to X is 0.2 or greater and 0.7 or less, and the molar ratio of A to M is 0.02 or greater and 0.80 or less.

Description

Technical Field

[0001] This disclosure relates to solid electrolyte materials and batteries using the solid electrolyte material. Background Technology

[0002] Patent document 1 discloses an all-solid-state battery using sulfide solid electrolyte material.

[0003] Patent document 2 discloses the use of Li 6-4a M a X6 represents a solid electrolyte material. M is selected from at least one of Zr, Hf, and Ti. X is a halogen element. It satisfies the mathematical formula: 0 < a < 1.5.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-129312

[0007] Patent Document 2: International Publication No. 2020 / 070955 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this disclosure is to provide a novel solid electrolyte with high usefulness.

[0010] Methods for solving problems

[0011] This disclosure relates to a solid electrolyte material, wherein...

[0012] Contains Li, M, O, X and A.

[0013] here,

[0014] M is selected from at least one of Ti, Zr, and Hf.

[0015] X is selected from at least one of F, Cl, Br and I.

[0016] A is selected from at least one of P and B.

[0017] The molar ratio of Li to M is greater than 1.0 and less than 3.0.

[0018] The molar ratio of O to X is greater than 0.2 and less than 0.7.

[0019] The molar ratio of A to M is greater than 0.02 and less than 0.80.

[0020] Invention Effects

[0021] This disclosure provides a novel solid electrolyte with high utility. Attached Figure Description

[0022] Figure 1 A cross-sectional view showing the battery 1000 of the second embodiment.

[0023] Figure 2 A cross-sectional view showing the electrode material 1100 of the second embodiment.

[0024] Figure 3 A schematic diagram of a pressure forming mold 300 used to evaluate the ionic conductivity of solid electrolyte materials.

[0025] Figure 4 This is a graph showing the initial discharge characteristics of the battery in Example 1. Detailed Implementation

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0027] (First Embodiment)

[0028] The solid electrolyte material of the first embodiment contains Li, M, O, X, and A. M is at least one selected from Ti, Zr, and Hf. X is at least one selected from F, Cl, Br, and I. A is at least one selected from P and B. The molar ratio of Li to M is 1.0 or more and 3.0 or less. The molar ratio of O to X is 0.2 or more and 0.7 or less. The molar ratio of A to M is 0.02 or more and 0.80 or less.

[0029] The solid electrolyte material of the first embodiment is, for example, a novel solid electrolyte material that is suitable for lithium-ion conduction and has high utility. The solid electrolyte material of the first embodiment can, for example, have a practical lithium-ion conductivity, for example, a high lithium-ion conductivity. Here, a high lithium-ion conductivity is, for example, 0.42 mS / cm or higher near room temperature. That is, the solid electrolyte material of the first embodiment can, for example, have an ion conductivity of 0.42 mS / cm or higher.

[0030] The concentration of Li, the conductive carrier, can be optimized as long as the molar ratio of Li to M is 1.0 or more and 3.0 or less. A pathway for lithium-ion diffusion is easily formed as long as the molar ratio of O to X is 0.2 or more and 0.7 or less. Therefore, the solid electrolyte material of the first embodiment has a high lithium-ion conductivity.

[0031] Solid electrolyte materials exhibit high thermal stability as long as the molar ratio of A to M is 0.02 or higher and 0.80 or lower. For example, even when the solid electrolyte material of the first embodiment is heated to 150°C, the lithium-ion conductivity hardly decreases.

[0032] The molar ratio of Li to M can be calculated using the formula: (mass of Li) / (total mass of Ti, Zr, and Hf). The molar ratio of O to X can be calculated using the formula: (mass of O) / (total mass of F, Cl, Br, and I). The molar ratio of A to M can be calculated using the formula: (total mass of P and B) / (total mass of Ti, Zr, and Hf). Hereinafter, the molar ratio of Li to M will sometimes be written as "Li / M". The molar ratio of O to X will sometimes be written as "O / X". The molar ratio of A to M will sometimes be written as "A / M".

[0033] The solid electrolyte material of the first embodiment can be used to obtain a battery with excellent charge-discharge characteristics. An example of this battery is an all-solid-state battery. An all-solid-state battery can be a primary battery or a secondary battery.

[0034] The solid electrolyte material of the first embodiment can maintain a high lithium-ion conductivity within the assumed battery operating temperature range. Therefore, the battery using the solid electrolyte material of the first embodiment can operate stably even in environments with temperature variations. The battery operating temperature range is, for example, -30°C to 80°C.

[0035] The solid electrolyte material of the first embodiment is preferably substantially sulfur-free. "Substantially sulfur-free" means that the solid electrolyte material contains no sulfur as a constituent element, except for sulfur that inevitably mixes in as an impurity. In this case, the sulfur mixed in as an impurity in the solid electrolyte material is, for example, 1 mol% or less. From a safety point of view, it is preferable that the solid electrolyte material of the first embodiment is sulfur-free. Sulfur-free solid electrolyte materials do not produce hydrogen sulfide even when exposed to the atmosphere, thus exhibiting excellent safety. The sulfide solid electrolyte material disclosed in Patent Document 1 can produce hydrogen sulfide when exposed to the atmosphere, which should be noted.

[0036] To improve the ionic conductivity of the solid electrolyte material, the solid electrolyte material of the first embodiment may also be substantially composed of Li, M, O, X, and A. Here, "the solid electrolyte material of the first embodiment is substantially composed of Li, M, O, X, and A" means that the ratio (i.e., mole fraction) of the total mass of Li, M, O, X, and A to the total mass of all elements constituting the solid electrolyte material of the first embodiment is 90% or more. As an example, this ratio may also be 95% or more.

[0037] In order to improve the ionic conductivity of the solid electrolyte material, the solid electrolyte material of the first embodiment may also be composed of only Li, M, O, X and A.

[0038] To improve the ionic conductivity of solid electrolyte materials, M can also contain Zr. M can also be Zr.

[0039] To improve the ionic conductivity of solid electrolyte materials, X can also contain Cl. X can also be Cl.

[0040] To improve the ionic conductivity of solid electrolyte materials, A can also contain P. A can also be P.

[0041] The upper and lower limits of the molar ratio of Li to M can be specified by any combination of values ​​selected from 1.0, 1.3, 1.4, 1.5 and 3.0.

[0042] To improve the ionic conductivity of solid electrolyte materials, the molar ratio of Li to M can be greater than 1.3 and less than 2.0, or greater than 1.3 and less than 1.5.

[0043] The upper and lower limits of the molar ratio of O to X can be specified by any combination of values ​​selected from 0.2, 0.30, 0.31, 0.32, 0.35, 0.37, 0.39, 0.41, 0.52, 0.63 and 0.7.

[0044] To improve the ionic conductivity of solid electrolyte materials, the molar ratio of O to X can be 0.3 or higher and 0.63 or lower, or 0.3 or higher and 0.52 or lower, or 0.3 or higher and 0.41 or lower.

[0045] The upper and lower limits of the molar ratio of A to M can be specified by any combination of values ​​selected from 0.02, 0.04, 0.08, 0.12, 0.13, 0.16, 0.20, 0.40, 0.60 and 0.80.

[0046] To improve the ionic conductivity of solid electrolyte materials, the molar ratio of A to M can be above 0.04 and below 0.60.

[0047] To improve the ionic conductivity of solid electrolyte materials, the molar ratio of A to M can be above 0.04 and below 0.20.

[0048] The solid electrolyte material in the first embodiment can be crystalline or amorphous.

[0049] The solid electrolyte material in the first embodiment can also be amorphous. Amorphous solid electrolytes have advantages such as crystal orientation anisotropy without ion conduction, minimal grain boundary influence, and less ion conductivity degradation after further micronization and other processing.

[0050] The solid electrolyte material of the first embodiment may also contain a crystalline phase. This crystalline phase is, for example, derived from LiX or Li. 6-4a M a X6 (satisfies the mathematical expression: 0 < a < 1.5).

[0051] The solid electrolyte material of the first embodiment may contain both an amorphous phase and a crystalline phase, or only one of them. The fine structure of the solid electrolyte material can be investigated by X-ray diffraction.

[0052] The shape of the solid electrolyte material in the first embodiment is not limited. Examples of this shape are needle-shaped, spherical, or ellipsoidal. The solid electrolyte material in the first embodiment can also be particles. The solid electrolyte material in the first embodiment can also be formed in the form of pellets or plates.

[0053] When the solid electrolyte material of the first embodiment is in the form of particles (e.g., spheres), it can have a median particle size of 0.1 μm or more and 100 μm or less, or a median particle size of 0.5 μm or more and 10 μm or less. Therefore, the solid electrolyte material of the first embodiment and other materials can be well dispersed. The median particle size means the particle size (d50) that corresponds to the 50% volumetric cumulative distribution in a volumetric particle size distribution. The volumetric particle size distribution can be determined using a laser diffraction apparatus or an image analysis apparatus.

[0054] When the solid electrolyte material of the first embodiment is in the shape of particles (e.g., spheres), it can also have a smaller median particle size than the active material. Therefore, the solid electrolyte material and the active material of the first embodiment can form a good dispersion.

[0055] <Manufacturing Methods of Solid Electrolyte Materials>

[0056] The solid electrolyte material of the first embodiment can be manufactured by the following method.

[0057] Prepare the raw material powder in a manner that yields the desired composition. Examples of raw material powders include oxides, hydroxides, halides, or acid halides.

[0058] As an example, suppose in a solid electrolyte material composed of Li, Zr, O, Cl, and P (i.e., a solid electrolyte material where M is Zr, X is Cl, and A is P), the molar ratio of Li / M when mixing the raw materials is 1.4, the molar ratio of O / X is 0.375, and the molar ratio of A / M is 0.04. In this case, Li₂O₂, ZrCl₄, and P₂O₅ are mixed in a molar ratio of Li₂O₂∶ZrCl₄∶P₂O₅ = 0.7∶1∶0.02. M, X, and A are determined by selecting the raw material powders. The molar ratios of Li / M, O / X, and A / M are determined by selecting the mixing ratio of the raw material powders. Alternatively, the raw material powders can be mixed in a pre-adjusted molar ratio to offset possible compositional changes during the synthesis process.

[0059] The reactants are obtained by calcining a mixture of raw material powders. To suppress the evaporation of raw materials caused by calcination, the mixture of raw material powders can also be calcined in a vacuum or inert gas atmosphere by sealing it in an airtight container made of quartz glass or borosilicate glass. Inert gas atmospheres, for example, are argon or nitrogen atmospheres.

[0060] Alternatively, reactants can be obtained by subjecting the mixture of raw material powders to a mechanochemical reaction within a mixing apparatus such as a planetary ball mill. In other words, a mechanochemical grinding method can also be used to mix and react the raw material powders. Through these methods, the solid electrolyte material of the first embodiment can be obtained.

[0061] When a mixture of raw material powders is calcined or reacted in a mechanochemical manner, some of the oxygen (O) sometimes evaporates from the raw material powders. As a result, the molar ratio O / X of the solid electrolyte material may be less than the O / X value calculated from the molar ratio of the raw material powders.

[0062] The composition of solid electrolyte materials can be determined, for example, by inductively coupled plasma atomic emission spectrometry (ICP-AES), ion chromatography, inert gas melting-infrared absorption spectrometry, or EPMA (Electron Probe Micro Analyzer). For instance, the compositions of Li and M can be determined by ICP-AES, the composition of X by ion chromatography, O by inert gas melting-infrared absorption spectrometry, and the composition of A by EPMA.

[0063] (Second Implementation)

[0064] The second embodiment will be described below. Items described in the first embodiment may be omitted as appropriate.

[0065] The battery of the second embodiment includes a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is disposed between the positive electrode and the negative electrode. At least one solid electrolyte material selected from the positive electrode, the electrolyte layer, and the negative electrode is used, which contains the solid electrolyte material of the first embodiment.

[0066] The battery of the second embodiment has excellent charge and discharge characteristics because it contains the solid electrolyte material of the first embodiment.

[0067] Figure 1 A cross-sectional view showing the battery 1000 of the second embodiment.

[0068] The battery 1000 has a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0069] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100.

[0070] Electrolyte layer 202 contains an electrolyte material. The electrolyte material may be, for example, a solid electrolyte material.

[0071] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

[0072] The solid electrolyte particles 100 are particles containing the solid electrolyte material of the first embodiment. The solid electrolyte particles 100 may also be particles containing the solid electrolyte material of the first embodiment as a main component. The term "particles containing the solid electrolyte material of the first embodiment as a main component" means particles containing, at most in a molar ratio, the solid electrolyte material of the first embodiment. The solid electrolyte particles 100 may also be particles composed of the solid electrolyte material of the first embodiment.

[0073] The positive electrode 201 contains a material that can insert and extract metal ions such as lithium ions. The positive electrode 201 contains, for example, a positive electrode active material (e.g., positive electrode active material particles 204).

[0074] 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 sulfide oxides, or transition metal nitride oxides. Examples of lithium-containing transition metal oxides include Li(Ni, Co, Al)O2, Li(Ni, Co, Mn)O2, or LiCoO2.

[0075] In this disclosure, “(A, B, C)” means “selected from at least one of A, B and C”.

[0076] From the perspective of battery cost and safety, lithium phosphate can also be used as the positive electrode active material.

[0077] When the positive electrode 201 contains the solid electrolyte material of the first embodiment and X contains I (i.e., iodine), lithium iron phosphate can also be used as the positive electrode active material. The solid electrolyte material of the first embodiment containing I is prone to oxidation. If lithium iron phosphate is used as the positive electrode active material, the oxidation reaction of the solid electrolyte material can be suppressed. That is, the formation of an oxide layer with low lithium-ion conductivity can be suppressed. As a result, the battery has a higher charge and discharge efficiency.

[0078] The positive electrode 201 not only contains the solid electrolyte material of the first embodiment, but may also contain transition metal fluorides as the positive electrode active material. Even when the solid electrolyte material of the first embodiment is fluorinated with transition metal fluorides, it is difficult to form a resistive layer. As a result, the battery has high charge and discharge efficiency.

[0079] Transition metal fluorides contain both oxygen and fluorine. As an example, transition metal fluorides can also be composed of the formula Li. p Me q O m F n The compound is represented by Me. Here, Me is selected from at least one 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 satisfies the mathematical formulas: 0.5 ≤ p ≤ 1.5, 0.5 ≤ q ≤ 1.0, 1 ≤ m < 2, and 0 < n ≤ 1. An example of such a transition metal fluoride oxide is Li. 1.05 (Ni 0.35 Co 0.35 Mn 0.3 ) 0.95 O 1.9 F 0.1 .

[0080] The positive electrode active material particles 204 can also have a median particle size of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median particle size 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. As a result, the charge and discharge characteristics of the battery are improved. When the positive electrode active material particles 204 have a median particle size of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles 204 can be increased. As a result, the battery can operate at high output power.

[0081] The positive electrode active material particles 204 can also have a larger median particle size than the solid electrolyte particles 100. As a result, the positive electrode active material particles 204 and the solid electrolyte particles 100 can form a good dispersion state.

[0082] From the perspective of battery energy density and output power, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the total volume of the positive electrode active material particles 204 and the solid electrolyte particles 100 can also be 0.30 or more and 0.95 or less.

[0083] Figure 2 This is a cross-sectional view showing the electrode material 1100 according to the second embodiment. The electrode material 1100 is, for example, contained in the positive electrode 201. To prevent the solid electrolyte particles 100 from reacting with the positive electrode active material (i.e., the electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This suppresses the rise of the battery's overpotential. Examples of coating materials contained in the coating layer 216 are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes.

[0084] When the solid electrolyte particles 100 are sulfide solid electrolytes, the coating material can also be the solid electrolyte material of the first embodiment. The solid electrolyte material of the first embodiment is less prone to oxidation compared to sulfide solid electrolytes. Therefore, it is possible to suppress the rise of the battery's reaction overpotential.

[0085] When the solid electrolyte particles 100 are the solid electrolyte material of the first embodiment and X contains I, the coating material can also be the solid electrolyte material of the first embodiment and X is at least one selected from Cl and Br. The solid electrolyte material of the first embodiment without I is less prone to oxidation than the solid electrolyte material of the first embodiment containing I. As a result, the battery has higher charge and discharge efficiency.

[0086] When the solid electrolyte particles 100 are the solid electrolyte material of the first embodiment and X contains I, the coating material may also contain an oxide solid electrolyte. This oxide solid electrolyte may also be lithium niobate, which exhibits excellent stability even at high potentials. Therefore, the battery has high charge / discharge efficiency.

[0087] The positive electrode 201 can also be composed 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 disposed 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 of the first embodiment containing I, and a coating layer 216 is formed on the surface of the second positive electrode active material. According to the above configuration, the oxidation of the solid electrolyte material of 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, when the coating material is a halide solid electrolyte, I is not contained as a halogen element. The first positive electrode active material can be the same material as the second positive electrode active material, or it can be a different material from the second positive electrode active material.

[0088] From the perspective of battery energy density and output power, the cathode 201 can also have a thickness of more than 10μm and less than 500μm.

[0089] Electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. Electrolyte layer 202 may also be a solid electrolyte layer. Electrolyte layer 202 may also contain the solid electrolyte material of the first embodiment. Electrolyte layer 202 may also be composed solely of the solid electrolyte material of the first embodiment.

[0090] The electrolyte layer 202 may also be composed of a solid electrolyte material different from that of the first embodiment. Examples of solid electrolyte materials different from those of the first embodiment are Li2MgX'4, Li2FeX'4, Li(Al, Ga, In)X'4, Li3(Al, Ga, In)X'6, or LiI. Here, X' is at least one selected from F, Cl, Br, and I.

[0091] Hereinafter, the solid electrolyte material of the first embodiment will be referred to as the first solid electrolyte material. Solid electrolyte materials that are different from the solid electrolyte material of the first embodiment will be referred to as the second solid electrolyte material.

[0092] The electrolyte layer 202 may contain not only a first solid electrolyte material but also a second solid electrolyte material. The first and second solid electrolyte materials may be uniformly dispersed within the electrolyte layer 202. The layers composed of the first and second solid electrolyte materials may also be stacked along the stacking direction of the battery 1000.

[0093] The electrolyte layer 202 can also have a thickness of more than 1 μm and less than 100 μm. When the electrolyte layer 202 has a thickness of more than 1 μm, short circuits are less likely to occur between the positive electrode 201 and the negative electrode 203. When the electrolyte layer 202 has a thickness of less than 100 μm, the battery can operate with high output power.

[0094] Alternatively, another electrolyte layer can be further disposed between the electrolyte layer 202 and the negative electrode 203. That is, a second electrolyte layer can also be further disposed between the electrolyte layer 202 and the negative electrode 203. For example, when the electrolyte layer 202 contains a first solid electrolyte material, the second electrolyte layer can also be composed of another solid electrolyte material that is electrochemically stable compared to the first solid electrolyte material. Specifically, the reduction potential of the solid electrolyte material constituting the second electrolyte layer can also be lower than the reduction potential of the first solid electrolyte material. Therefore, the first solid electrolyte material can be used without reducing it. As a result, the charge and discharge efficiency of the battery can be improved.

[0095] The negative electrode 203 contains a material capable of inserting and de-intercalating metal ions (e.g., lithium ions). The negative electrode 203 may contain, for example, a negative electrode active material (e.g., negative electrode active material particles 205).

[0096] Examples of negative electrode active materials include metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. Metallic materials can be elemental metals or alloys. Examples of metallic materials include lithium metal or lithium alloys. Examples of carbon materials include natural graphite, coke, graphitizable carbon, carbon fibers, spherical carbon, artificial graphite, or amorphous carbon. From a capacity density perspective, suitable examples of negative electrode active materials are silicon (Si), tin (Sn), silicon compounds, or tin compounds.

[0097] The negative electrode active material can also be selected based on the reduction resistance of the solid electrolyte material contained in the negative electrode 203. When the negative electrode 203 contains a first solid electrolyte material, a material that can insert and extract lithium ions at a voltage greater than 1.6V relative to lithium energy can also 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 a high charge and discharge efficiency. Examples of such materials include titanium oxide, indium metal, or lithium alloys. An example of titanium oxide is Li4Ti5O. 12 LiTi2O4 or TiO2.

[0098] The negative electrode active material particles 205 can also have a median particle size of 0.1 μm or larger and 100 μm or smaller. When the negative electrode active material particles 205 have a median particle size of 0.1 μm or larger, the negative electrode active material particles 205 and the solid electrolyte particles 100 can form a good dispersion state in the negative electrode 203. As a result, the charge and discharge characteristics of the battery are improved. When the negative electrode active material particles 205 have a median particle size of 100 μm or smaller, the lithium diffusion rate within the negative electrode active material particles 205 can be increased. As a result, the battery can operate at high output power.

[0099] The negative electrode active material particles 205 can also have a larger median particle size than the solid electrolyte particles 100. As a result, the negative electrode active material particles 205 and the solid electrolyte particles 100 can form a good dispersion state.

[0100] From the perspective of battery energy density and output power, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the total volume of the negative electrode active material particles 205 and the solid electrolyte particles 100 can also be 0.30 or more and 0.95 or less.

[0101] Figure 2 The electrode material 1100 shown can also 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 can also be formed on the surface of the electrode active material particles 206. This results in a battery with high charge / discharge efficiency. Examples of coating materials contained in the coating layer 216 include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes.

[0102] When the solid electrolyte particle 100 is the first solid electrolyte material, the coating material can also be a sulfide solid electrolyte, an oxide solid electrolyte, or a polymeric solid electrolyte. An example of a sulfide solid electrolyte is Li₂S-P₂S₅. An example of an oxide solid electrolyte is lithium triphosphate. An example of a polymeric solid electrolyte is a composite compound of polyethylene oxide and lithium salt. An example of such a polymeric solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0103] From the perspective of battery energy density and output power, the negative electrode 203 can also have a thickness of more than 10μm and less than 500μm.

[0104] The second solid electrolyte material is selected from at least one of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203, which can also improve ion conductivity. Examples of the second solid electrolyte material are sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, or organic polymer solid electrolytes.

[0105] In this disclosure, "sulfide solid electrolyte" means a solid electrolyte containing sulfur. "Oxide solid electrolyte" means a solid electrolyte containing oxygen. Oxide solid electrolytes may also contain anions other than oxygen (except for sulfide anions and halide anions). "Halide solid electrolyte" means a solid electrolyte containing halogens and not containing sulfur. Halide solid electrolytes may contain not only halogens but also oxygen.

[0106] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, and Li₂S-P₂S₅. 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 .

[0107] Examples of oxide solid electrolytes are:

[0108] (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutes;

[0109] (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3,

[0110] (iii)Li 14 ZnGe4O 16 LISICON-type solid electrolytes such as Li4SiO4, LiGeO4, or their elemental substitutes.

[0111] (iv)Li7La3Zr2O 12 Garnet-type solid electrolytes such as or elemental substitutes thereof, or (v)Li3PO4 or its N-substitutes thereof.

[0112] An example of a halide solid electrolyte is the use of Li a Me' b Y c Z6 represents the compound. Here, it satisfies the mathematical formula: a + mb + 3c = 6 and c > 0. Me' is at least one metallic element and half-metallic element selected from those other than Li and Y. Z is at least one selected from F, Cl, Br, and I. The value of m represents the valence of Me'.

[0113] "Half-metallic elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements contained in Groups 1 to 12 of the periodic table (except hydrogen) and all elements contained in Groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0114] To improve the ionic conductivity of halide solid electrolytes, Me' may also be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0115] Examples of halide solid electrolytes are Li3YCl6 or Li3YBr6.

[0116] When the electrolyte layer 202 contains a first solid electrolyte material, the negative electrode 203 can also contain a sulfide solid electrolyte. Thus, the sulfide solid electrolyte, which is electrochemically stable relative to the negative electrode active material, can suppress the contact between the first solid electrolyte material and the negative electrode active material. As a result, the battery has a lower internal resistance.

[0117] Examples of organic polymer solid electrolytes include polymeric compounds and lithium salt compounds. Polymeric compounds can also have an ethylene oxide structure. Polymers with an ethylene oxide structure exhibit higher ionic conductivity because they can contain more lithium salts.

[0118] Examples of lithium salts are LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. A single lithium salt selected from these can be used. Alternatively, a mixture of two or more lithium salts selected from these can be used.

[0119] The electrolyte, selected from at least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203, is also capable of readily accepting lithium ions and improving the output power characteristics of the battery, and contains a non-aqueous electrolyte, a gel electrolyte or an ionic liquid.

[0120] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in that non-aqueous solvent. Examples of non-aqueous solvents include cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorine solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, or butyl carbonate. Examples of chain carbonate solvents include dimethyl carbonate, methyl ethyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, or 1,3-dioxapentane. Examples of chain ether solvents include 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate. Examples of fluorine solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, methyl ethyl fluorocarbonate, or dimethyl fluorocarbonate. One of these non-aqueous solvents can be used alone. Alternatively, a mixture of two or more non-aqueous solvents can be used.

[0121] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. A single lithium salt selected from these can be used. Alternatively, a mixture of two or more lithium salts selected from these can be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0122] As a gel electrolyte, a polymeric material impregnated with a non-aqueous electrolyte can be used. Examples of polymeric materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers containing ethylene oxide bonds.

[0123] Examples of cations contained in ionic liquids are:

[0124] (i) Aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium;

[0125] (ii) Aliphatic cyclic ammonium compounds such as pyrrolidinemonium, morpholinium, imidazolinemonium, tetrahydropyrimidinemonium, piperazinemonium, or piperidinemonium, or

[0126] (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazoline.

[0127] An example of anion contained in ionic liquids is PF6. - BF4 - SbF6 - AsF6 - SO3CF3 - N(SO2CF3)2 -N(SO2C2F5)2 - N(SO2CF3)(SO2C4F9) - Or C(SO2CF3)3 - .

[0128] Ionic liquids can also contain lithium salts.

[0129] At least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 may also contain a binder for the purpose of improving the adhesion between particles.

[0130] Examples of adhesives include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, or carboxymethyl cellulose. Copolymers may also be used as adhesives. Examples of such adhesives are copolymers selected from two or more materials chosen from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ethers, vinylidene fluoride, trifluorochloroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures selected from the above materials may also be used as adhesives.

[0131] At least one of the positive electrode 201 and the negative electrode 203 can also be used to improve electronic conductivity, and contains a conductive additive.

[0132] Examples of conductive additives are:

[0133] (i) Graphite, such as natural or artificial graphite;

[0134] (ii) Carbon blacks such as acetylene black or Ketjen black;

[0135] (iii) Conductive fibers such as carbon fiber or metal fiber;

[0136] (iv) Fluorocarbon,

[0137] (v) Metal powders such as aluminum

[0138] (vi) Conductive whiskers such as zinc oxide or potassium titanate;

[0139] (vii) Conductive metal oxides such as titanium dioxide, or

[0140] (viii) Conductive polymers such as polyaniline, polypyrrole, or polythiophene. For cost reduction, conductive additives described in (i) or (ii) above may also be used.

[0141] Examples of the battery shape in the second embodiment include coin shape, cylindrical shape, square shape, sheet shape, button shape, flat shape, or stacked shape.

[0142] The battery of the second embodiment can also be manufactured by preparing a positive electrode forming material, an electrolyte layer forming material and a negative electrode forming material, and using a known method to make a laminate in which a positive electrode, an electrolyte layer and a negative electrode are sequentially arranged.

[0143] Example

[0144] The present disclosure will now be described in more detail through the use of examples and comparative examples.

[0145] (Example 1)

[0146] [Preparation of Solid Electrolyte Materials]

[0147] In a dry atmosphere with a dew point below -30°C (hereinafter referred to as "dry atmosphere"), Li₂O₂, ZrCl₄, and P₂O₅ were prepared as raw material powders in a molar ratio of Li₂O₂:ZrCl₄:P₂O₅ = 0.7:1:0.02. These raw material powders were mixed in a mortar to obtain a mixed powder. The obtained mixed powder was then milled at 600 rpm for 24 hours using a planetary ball mill. This yielded the solid electrolyte material of Example 1 containing Li, Zr, O, Cl, and P.

[0148] [Compositional Analysis of Solid Electrolyte Materials]

[0149] The Li and Zr contents of the solid electrolyte material obtained in Example 1 were determined using a high-frequency inductively coupled plasma atomic emission spectrometry (ICP-AES) apparatus (iCAP7400 manufactured by Thermo Fisher Scientific). The Cl content was determined using ion chromatography (ICS-2000 manufactured by Dionex). The O content was determined using an oxygen analyzer (EMGA-930 manufactured by Horiba Corporation) via inert gas melting-infrared absorption. From the results, the molar ratios Li / M, O / X, and A / M were calculated. Here, the A content is represented by the feed amount.

[0150] In the solid electrolyte material of Example 1, the molar ratio Li / M is 1.4. The molar ratio O / X is 0.31. The molar ratio A / M is 0.04.

[0151] [Evaluation of Ion Conductivity]

[0152] Figure 3A schematic diagram of a pressure forming mold 300 used to evaluate the ionic conductivity of solid electrolyte materials.

[0153] The pressure forming die 300 includes an upper punch 301, a frame die 302, and a lower punch 303. The frame die 302 is formed of insulating polycarbonate. The upper punch 301 and the lower punch 303 are both formed of electronically conductive stainless steel.

[0154] use Figure 3 The ionic conductivity of the solid electrolyte material of Example 1 was measured using the pressure molding die 300 shown in the following method.

[0155] In a dry atmosphere, the powder of the solid electrolyte material of Example 1 (i.e., Figure 3 Powder 101 of the solid electrolyte material is filled into the interior of the pressure forming mold 300. Inside the pressure forming mold 300, a pressure of 300 MPa is applied to the solid electrolyte material of Example 1 using the upper part of the punch 301. In this way, the evaluation battery of Example 1 is obtained.

[0156] While maintaining pressure on the evaluation battery, the upper part 301 and lower part 303 of the punch were connected to a potentiostat (VersaSTAT4 manufactured by Princeton Applied Research) equipped with a frequency response analyzer. The upper part 301 of the punch was connected to the working electrode and the potential measurement terminal. The lower part 303 of the punch was connected to the counter electrode and the reference electrode. The ionic conductivity of the solid electrolyte material of Example 1 was measured by electrochemical impedance spectroscopy at room temperature. The result showed that the ionic conductivity measured at 22°C was 1.82 mS / cm.

[0157] [Battery Manufacturing]

[0158] In an argon atmosphere with a dew point below -60°C, the solid electrolyte material and LiCoO2 of Example 1 were prepared at a volume ratio of solid electrolyte material to LiCoO2 of 30:70. These materials were mixed in an agate mortar. This yielded the positive electrode mixture.

[0159] In an insulating cylinder with an inner diameter of 9.5 mm, the solid electrolyte material (80 mg) and the positive electrode mixture (8.2 mg) of Example 1 were stacked to obtain a laminate. A pressure of 360 MPa was applied to the laminate to form a solid electrolyte layer and a positive electrode. The solid electrolyte layer has a thickness of 500 μm.

[0160] Next, a Li-In alloy (thickness: 200 μm) is laminated on the solid electrolyte layer. A pressure of 80 MPa is applied to the laminate to form the negative electrode.

[0161] Next, a current collector made of stainless steel is installed on the positive and negative terminals, and the current collector leads are installed on the current collector.

[0162] Finally, an insulating hoop is used to isolate the inside of the insulating cylinder from the outside atmosphere, thus sealing the inside of the cylinder.

[0163] This yields the battery of Example 1.

[0164] [Charge / Discharge Test]

[0165] Figure 4 This is a graph showing the initial discharge characteristics of the battery in Example 1. The horizontal axis represents the discharge capacity, and the vertical axis represents the voltage. Figure 4 The results shown were determined using the following method.

[0166] The battery of Example 1 was placed in a constant temperature bath maintained at 25°C.

[0167] The battery of Example 1 was charged to a voltage of 3.6V at a current value at a rate of 0.05C (20-hour rate) relative to its theoretical capacity. Then, the battery of Example 1 was discharged to a voltage of 1.9V at a current value at a rate of 0.05C.

[0168] Based on the results of the charge-discharge test, the battery of Example 1 has an initial discharge capacity of 0.99 mAh.

[0169] (Examples 2-9 and Comparative Example 1)

[0170] [Preparation of Solid Electrolyte Materials]

[0171] In Example 2, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2:ZrCl4:P2O5 = 0.75:1:0.04.

[0172] In Example 3, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2:ZrCl4:P2O5 = 0.75:1:0.06.

[0173] In Example 4, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2:ZrCl4:P2O5 = 0.75:1:0.08.

[0174] In Example 5, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2∶ZrCl4∶P2O5=0.75∶1∶0.1.

[0175] In Example 6, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2∶ZrCl4∶P2O5=0.75∶1∶0.2.

[0176] In Example 7, Li2O2, ZrCl4 and P2O5 were prepared as raw material powders in a molar ratio of Li2O2:ZrCl4:P2O5 = 0.75:1:0.3.

[0177] In Example 8, Li2O2, ZrCl4 and B2O3 were prepared as raw material powders in a molar ratio of Li2O2:ZrCl4:B2O3 = 0.65:1:0.066.

[0178] In Example 9, Li2O2, ZrCl4 and B2O3 were prepared as raw material powders in a molar ratio of Li2O2∶ZrCl4∶B2O3=0.65∶1∶0.10.

[0179] In Comparative Example 1, LiCl and ZrCl4 were prepared as raw material powders in a molar ratio of LiCl:ZrCl4 = 2:1.

[0180] Except as described above, the solid electrolyte materials of Examples 2 to 9 and Comparative Example 1 were obtained in the same manner as in Example 1.

[0181] [Compositional Analysis of Solid Electrolyte Materials]

[0182] Similar to Example 1, the composition of the solid electrolyte materials in Examples 2-9 and Comparative Example 1 was analyzed.

[0183] In Example 2, the molar ratio of the solid electrolyte material was Li / M 1.5. The molar ratio of O / X was 0.35. The molar ratio of A / M was 0.08.

[0184] The solid electrolyte material in Example 3 has a Li / M molar ratio of 1.5, an O / X molar ratio of 0.37, and an A / M molar ratio of 0.12.

[0185] The solid electrolyte material in Example 4 has a Li / M molar ratio of 1.5, an O / X molar ratio of 0.39, and an A / M molar ratio of 0.16.

[0186] The solid electrolyte material in Example 5 has a Li / M molar ratio of 1.5, an O / X molar ratio of 0.41, and an A / M molar ratio of 0.20.

[0187] The solid electrolyte material in Example 6 has a Li / M molar ratio of 1.5, an O / X molar ratio of 0.52, and an A / M molar ratio of 0.40.

[0188] The solid electrolyte material in Example 7 has a Li / M molar ratio of 1.5, a O / X molar ratio of 0.63, and an A / M molar ratio of 0.60.

[0189] The solid electrolyte material in Example 8 has a Li / M molar ratio of 1.3, a O / X molar ratio of 0.30, and an A / M molar ratio of 0.13.

[0190] The solid electrolyte material in Example 9 has a Li / M molar ratio of 1.3, a O / X molar ratio of 0.32, and an A / M molar ratio of 0.20.

[0191] The solid electrolyte material in Comparative Example 1 has a Li / M molar ratio of 2.0 and an O / X molar ratio of 0.

[0192] [Evaluation of Ion Conductivity]

[0193] Similar to Example 1, the ionic conductivity of the solid electrolyte materials of Examples 2-9 and Comparative Example 1 was measured. The results are shown in Table 1.

[0194] Table 1

[0195]

[0196] (Inspection)

[0197] Table 1 shows that the solid electrolyte materials of Examples 1 to 9 have a high ionic conductivity of over 0.42 mS / cm at around room temperature.

[0198] The comparison between Examples 1-5 and Examples 6 and 7 shows that as long as the molar ratio A / M is above 0.04 and below 0.20, the solid electrolyte material has higher ionic conductivity.

[0199] A comparison of Examples 5 and 9, which have the same A / M value, shows that the presence of P in A tends to increase the ionic conductivity of the solid electrolyte material.

[0200] Even when F, Br, or I are used as X, ionic conductivity comparable to that of the solid electrolyte materials in Examples 1-9 can be achieved. Furthermore, the aforementioned tendency persists even in this case. The chemical and electrical properties of these elements are very similar to those of Cl, and some or all of Cl can be replaced by these elements.

[0201] Even when Ti or Hf is used as M, ionic conductivity comparable to that of the solid electrolyte materials in Examples 1-9 can be achieved. Furthermore, the aforementioned tendency persists even in this case. The chemical and electrical properties of these elements are very similar to those of Zr, and some or all of Zr can be replaced by these elements.

[0202] The batteries in all embodiments were charged and discharged at room temperature.

[0203] The solid electrolyte materials in Examples 1-9 do not contain sulfur, and therefore no hydrogen sulfide is generated.

[0204] As described above, the solid electrolyte material disclosed herein is a highly useful material that can improve, for example, lithium-ion conductivity while suppressing the generation of hydrogen sulfide, and is suitable for providing a battery that can be charged and discharged well.

[0205] Industrial availability

[0206] The solid electrolyte material disclosed herein can be used, for example, in all-solid-state lithium-ion secondary batteries.

Claims

1. A solid electrolyte material, wherein, Contains Li, M, O, X and A. here, M is selected from at least one of Ti, Zr, and Hf. X is selected from at least one of F, Cl, Br and I. A is selected from at least one of P and B. The molar ratio of Li to M is greater than 1.0 and less than 3.

0. The molar ratio of O to X is greater than 0.2 and less than 0.

7. The molar ratio of A to M is greater than 0.02 and less than 0.

60. The solid electrolyte material has an ionic conductivity of over 0.42 mS / cm near room temperature.

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

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

4. The solid electrolyte material according to claim 1 or 2, wherein, A contains P.

5. The solid electrolyte material according to claim 3, wherein, A contains P.

6. The solid electrolyte material according to claim 1 or 2, wherein, The molar ratio of A to M is greater than 0.04 and less than 0.

20.

7. The solid electrolyte material according to claim 3, wherein, The molar ratio of A to M is greater than 0.04 and less than 0.

20.

8. The solid electrolyte material according to claim 4, wherein, The molar ratio of A to M is greater than 0.04 and less than 0.

20.

9. The solid electrolyte material according to claim 5, wherein, The molar ratio of A to M is greater than 0.04 and less than 0.

20.

10. A battery, wherein, have: positive electrode, Negative electrode, and An electrolyte layer disposed between the positive electrode and the negative electrode; The material is selected from at least one solid electrolyte material containing any one of claims 1 to 9, chosen from the positive electrode, the negative electrode, and the electrolyte layer.

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