Solid electrolyte material and battery using the same

Abstract

The solid electrolyte material of the present disclosure includes Li, M, O, X, and A, 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, A is at least one selected from the group consisting of P and B, the molar ratio of Li to M is from 1.0 to 3.0, the molar ratio of O to X is from 0.2 to 0.7, and the molar ratio of A to M is from 0.02 to 0.80.

Description

Technical Field

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

Background Art

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

[0003] Patent Document 2 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

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a novel solid electrolyte having high utility.

Means for Solving the Problems

[0006] The solid electrolyte material of the present disclosure contains Li, M, O, X, and A, 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, A is at least one selected from the group consisting of 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. [Effects of the Invention]

[0007] The present disclosure provides a new, highly useful solid electrolyte. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment. [Figure 2] FIG. 2 shows a cross-sectional view of an electrode material 1100 according to a second embodiment. [Figure 3] FIG. 3 shows a schematic diagram of a pressing 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. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0010] (First embodiment) The solid electrolyte material according to the first embodiment contains Li, M, O, X, and A. 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. A is at least one selected from the group consisting of 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.

[0011] The solid electrolyte material according to the first embodiment is a novel, highly useful solid electrolyte material suitable for, for example, lithium ion conduction. The solid electrolyte material according to the first embodiment can have, for example, practical lithium ion conductivity, e.g., high lithium ion conductivity. Here, high lithium ion conductivity is, for example, 0.42 mS / cm or more at around room temperature. That is, the solid electrolyte material according to the first embodiment can have, for example, ion conductivity of 0.42 mS / cm or more.

[0012] When the molar ratio of Li to M is 1.0 or more and 3.0 or less, the concentration of Li, which is a conduction carrier, is optimized. When the molar ratio of O to X is 0.2 or more and 0.7 or less, paths for lithium ion diffusion are easily formed. Therefore, the solid electrolyte material according to the first embodiment has high lithium ion conductivity.

[0013] When the molar ratio of A to M is 0.02 or more and 0.80 or less, the solid electrolyte material has high thermal stability. For example, even when the solid electrolyte material according to the first embodiment is heated to 150°C, the lithium ion conductivity is hardly reduced.

[0014] The molar ratio of Li to M is calculated by the formula: (amount of substance of Li) / (total amount of substance of Ti, Zr, and Hf). The molar ratio of O to X is calculated by the formula: (amount of substance of O) / (total amount of substance of F, Cl, Br, and I). The molar ratio of A to M is calculated by the formula: (total amount of substance of P and B) / (total amount of substance of Ti, Zr, and Hf). Hereinafter, the molar ratio of Li to M may be expressed as "Li / M". The molar ratio of O to X may be expressed as "O / X". The molar ratio of A to M may be expressed as "A / M".

[0015] 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.

[0016] The solid electrolyte material according to the first embodiment can maintain high lithium ion conductivity in the expected temperature range of the battery. Therefore, the battery using the solid electrolyte material according to the first embodiment can operate stably even in an environment with temperature changes. The temperature range of the battery is, for example, from -30°C to 80°C.

[0017] It is desirable that the solid electrolyte material according to the first embodiment be substantially free of sulfur. The term "substantially free of sulfur" in the solid electrolyte material according to the first embodiment means that the solid electrolyte material does not contain sulfur as a constituent element, except for sulfur inevitably mixed in as an impurity. In this case, the amount of sulfur mixed in the solid electrolyte material as an impurity is, for example, 1 mol % or less. From the viewpoint of safety, it is preferable that the solid electrolyte material according to the first embodiment be free of sulfur. A sulfur-free solid electrolyte material is excellent in safety because it does not generate hydrogen sulfide even when exposed to the atmosphere. Note that the sulfide solid electrolyte material disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

[0018] In order to increase the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist essentially of Li, M, O, X, and A. Here, "the solid electrolyte material according to the first embodiment consists essentially of Li, M, O, X, and A" means that the ratio (i.e., molar fraction) of the total amount of substance of Li, M, O, X, and A to the total amount of substance of all elements constituting the solid electrolyte material according to the first embodiment is 90% or more. As an example, the ratio may be 95% or more.

[0019] In order to increase the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist of only Li, M, O, X, and A.

[0020] In order to increase the ionic conductivity of the solid electrolyte material, M may contain Zr. M may be Zr.

[0021] In order to increase the ionic conductivity of the solid electrolyte material, X may contain Cl. X may be Cl.

[0022] In order to increase the ionic conductivity of the solid electrolyte material, A may contain P. A may also be P.

[0023] The upper and lower limits of the molar ratio of Li to M can be defined by any combination selected from the following values: 1.0, 1.3, 1.4, 1.5, and 3.0.

[0024] To increase the ionic conductivity of the solid electrolyte material, the molar ratio of Li to M may be 1.3 or more and less than 2.0, or 1.3 or more and 1.5 or less.

[0025] The upper and lower limits of the molar ratio of O to X may be defined by any combination selected from the following values: 0.2, 0.30, 0.31, 0.32, 0.35, 0.37, 0.39, 0.41, 0.52, 0.63, and 0.7.

[0026] In order to increase the ionic conductivity of the solid electrolyte material, the molar ratio of O to X may be 0.3 or more and 0.63 or less, 0.3 or more and 0.52 or less, or 0.3 or more and 0.41 or less.

[0027] The upper and lower limits of the molar ratio of A to M may be defined by any combination selected from the following values: 0.02, 0.04, 0.08, 0.12, 0.13, 0.16, 0.20, 0.40, 0.60, and 0.80.

[0028] To increase the ionic conductivity of the solid electrolyte material, the molar ratio of A to M may be 0.04 or more and 0.60 or less.

[0029] To increase the ionic conductivity of the solid electrolyte material, the molar ratio of A to M may be 0.04 or more and 0.20 or less.

[0030] The solid electrolyte material according to the first embodiment may be crystalline or amorphous.

[0031] 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.

[0032] 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 (where the mathematical formula: 0 < a < 1.5 is satisfied).

[0033] 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.

[0034] 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 be formed to have the shape of a pellet or a plate.

[0035] When the shape of 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 may have a median diameter of 0.5 μm or more and 10 μm or less. Thereby, the solid electrolyte material according to the first embodiment and other materials can be well dispersed. The median diameter of the particles means the particle diameter (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 measurement device or an image analysis device.

[0036] When the solid electrolyte material according to the first embodiment is in the form of particles (for example, spheres), the solid electrolyte material may have a smaller median diameter than the active material, thereby enabling the solid electrolyte material according to the first embodiment and the active material to be well dispersed.

[0037] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment can be produced by the following method.

[0038] A raw material powder is prepared to have a desired composition, such as an oxide, hydroxide, halide, or oxyhalide.

[0039] As an example, for 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), assume that the molar ratio Li / M when mixing the raw materials is 1.4, the molar ratio O / X when mixing the raw materials is 0.375, and the molar ratio A / M when mixing the raw materials is 0.04. In this case, Li2O2, ZrCl4, and PO5 are mixed in a molar ratio of Li2O2:ZrCl4:PO5=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. The raw material powders may be mixed in a pre-adjusted molar ratio to offset compositional changes that may occur during the synthesis process.

[0040] A reactant is obtained by firing the mixture of raw material powders. To prevent evaporation of the raw materials during firing, the mixture of raw material powders may be sealed in an airtight container made of quartz glass or borosilicate glass and fired under vacuum or an inert gas atmosphere. The inert gas atmosphere is, for example, an argon atmosphere or a nitrogen atmosphere.

[0041] Alternatively, the mixture of raw material powders may be mechanochemically reacted with each other in a mixing device such as a planetary ball mill to obtain a reactant. That is, the raw material powders may be mixed and reacted using a mechanochemical milling method. By these methods, the solid electrolyte material according to the first embodiment can be obtained.

[0042] When the raw material powder mixture is sintered or subjected to a mechanochemical reaction, some of the O may evaporate from the raw material powder. 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 powder.

[0043] The composition of the solid electrolyte material can be determined by, for example, inductively coupled plasma (ICP) atomic emission spectroscopy, ion chromatography, inert gas fusion-infrared absorption spectroscopy, or EPMA (Electron Probe Micro Analyzer). For example, the compositions of Li and M can be determined by ICP atomic emission spectroscopy, the composition of X can be determined by ion chromatography, O can be measured by inert gas fusion-infrared absorption spectroscopy, and the composition of A can be determined by EPMA.

[0044] (Second embodiment) The second embodiment will be described below. The matters described in the first embodiment may be omitted as appropriate.

[0045] The battery according to 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 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.

[0046] The battery according to the second embodiment has excellent charge / discharge characteristics because it contains the solid electrolyte material according to the first embodiment.

[0047] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0048] The battery 1000 includes 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.

[0049] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0050] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0051] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0052] The solid electrolyte particle 100 is a particle containing the solid electrolyte material according to the first embodiment. The solid electrolyte particle 100 may be a particle containing the solid electrolyte material according to the first embodiment as a main component. Particles containing the solid electrolyte material according to the first embodiment as a main component refer to particles in which the component contained in the largest amount in terms of molar ratio is the solid electrolyte material according to the first embodiment. The solid electrolyte particle 100 may be a particle made of the solid electrolyte material according to the first embodiment.

[0053] The positive electrode 201 contains a material capable of absorbing and releasing metal ions such as lithium ions, and includes, for example, a positive electrode active material (for example, positive electrode active material particles 204).

[0054] Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O2, Li(Ni,Co,Mn)O2, and LiCoO2.

[0055] In the present disclosure, "(A,B,C)" means "at least one selected from the group consisting of A, B, and C."

[0056] From the viewpoints of battery cost and safety, lithium phosphate may be used as the positive electrode active material.

[0057] 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 easily 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.

[0058] 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 a transition metal fluoride, it is difficult to form a resistance layer. As a result, the battery has high charge-discharge efficiency.

[0059] The transition metal oxyfluoride contains oxygen and fluorine. As an example, the transition metal oxyfluoride may be a compound represented by the composition formula Li p Me q O m F n . 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 .

[0060] 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 well-dispersed state in the positive electrode 201. This improves the charge / 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 improves. This allows the battery to operate at high power.

[0061] 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 well-dispersed state.

[0062] From the viewpoint of the energy density and output of the battery, 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 may be 0.30 or more and 0.95 or less.

[0063] FIG. 2 shows a cross-sectional view of an electrode material 1100 according to a second embodiment. The electrode material 1100 is included in, for example, a 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 can suppress an increase in the reaction overvoltage of the battery. Examples of coating materials included in the coating layer 216 include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte.

[0064] When the solid electrolyte particle 100 is a sulfide solid electrolyte, the coating material may be the solid electrolyte material according to the first embodiment. The solid electrolyte material according to the first embodiment is less susceptible to oxidation than the sulfide solid electrolyte. Therefore, an increase in the reaction overvoltage of the battery can be suppressed.

[0065] When the solid electrolyte particle 100 is the solid electrolyte material according to the first embodiment and X includes I, the coating material may be the 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 include I is less susceptible to oxidation than the solid electrolyte material according to the first embodiment that includes I. As a result, the battery has high charge / discharge efficiency.

[0066] When the solid electrolyte particle 100 is the solid electrolyte material according to the first embodiment and X includes I, the coating material may include an oxide solid electrolyte. The oxide solid electrolyte may be lithium niobate, which has excellent stability even at high potentials. This allows the battery to have high charge / discharge efficiency.

[0067] The cathode 201 may comprise a first cathode layer containing a first cathode active material and a second cathode layer containing a second cathode active material. The second cathode layer is disposed between the first cathode layer and the electrolyte layer 202. The first cathode layer and the second cathode layer contain a solid electrolyte material according to the first embodiment containing I, and a coating layer 216 is formed on the surface of the second cathode active material. This configuration prevents the solid electrolyte material according to the first embodiment contained in the electrolyte layer 202 from being oxidized by the second cathode active material. As a result, the battery has a high charge capacity. Examples of coating materials contained in the coating layer 216 include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes. However, if the coating material is a halide solid electrolyte, it does not contain I as a halogen element. The first cathode active material may be the same material as the second cathode active material or may be a different material from the second cathode active material.

[0068] From the viewpoint of 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.

[0069] The electrolyte layer 202 contains an electrolyte material. The 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 the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may be made of only the solid electrolyte material according to the first embodiment.

[0070] The electrolyte layer 202 may be made solely of a solid electrolyte material different from the solid electrolyte material according to the first embodiment. Examples of the solid electrolyte material different from the solid electrolyte material according to the first embodiment include Li2MgX'4, Li2FeX'4, Li(Al,Ga,In)X'4, Li3(Al,Ga,In)X'6, or LiI, where X' is at least one selected from the group consisting of F, Cl, Br, and I.

[0071] Hereinafter, the solid electrolyte material according to the first embodiment will be referred to as a first solid electrolyte material, and a solid electrolyte material different from the solid electrolyte material according to the first embodiment will be referred to as a second solid electrolyte material.

[0072] The electrolyte layer 202 may contain not only the first solid electrolyte material but also the second solid electrolyte material. The first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed in the electrolyte layer 202. A layer made of the first solid electrolyte material and a layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

[0073] The electrolyte layer 202 may have a thickness of 1 μm or more and 100 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to short-circuit. When the electrolyte layer 202 has a thickness of 100 μm or less, the battery can operate at high power.

[0074] Another electrolyte layer may be further provided between the electrolyte layer 202 and the negative electrode 203. That is, a second electrolyte layer may be further provided 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 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 being reduced. As a result, the charge / discharge efficiency of the battery can be improved.

[0075] The negative electrode 203 contains a material capable of absorbing and releasing metal ions (for example, lithium ions) and a negative electrode active material (for example, negative electrode active material particles 205).

[0076] Examples of the negative electrode active material include a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a simple metal or an alloy. An example of the metal material is lithium metal or a lithium alloy. Examples of the carbon material are natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, suitable examples of the negative electrode active material are silicon (Si), tin (Sn), a silicon compound, or a tin compound.

[0077] The negative electrode active material may 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 capable of absorbing and releasing lithium ions at 1.6 V or more relative to lithium may be used as the negative electrode active material. If the negative electrode active material is such a material, reduction of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the battery has high charge / discharge efficiency. Examples of such materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12 , LiTi2O4, or TiO2.

[0078] 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 well-dispersed state in the negative electrode 203. This improves the charge / 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 improves. This allows the battery to operate at high power.

[0079] 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 well-dispersed state.

[0080] From the viewpoint of 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 total volume of the negative electrode active material particles 205 and the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less.

[0081] The electrode material 1100 shown in FIG. 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., the electrode active material particles 206), a coating layer 216 may be formed on the surface of the electrode active material particles 206. This allows the battery to have high charge / discharge efficiency. Examples of coating materials contained in the coating layer 216 include a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a halide solid electrolyte.

[0082] When the solid electrolyte particles 100 are the first solid electrolyte material, the coating material may be a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte. An example of a sulfide solid electrolyte is Li2S-P2S5. 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 a lithium salt. An example of such a polymer solid electrolyte is lithium bis(trifluoromethanesulfonyl)imide.

[0083] From the viewpoint of 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.

[0084] 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 increasing ion conductivity. Examples of the second solid electrolyte material include a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, or an organic polymer solid electrolyte.

[0085] In this disclosure, a "sulfide solid electrolyte" refers to a solid electrolyte containing sulfur. An "oxide solid electrolyte" refers to a solid electrolyte containing oxygen. An oxide solid electrolyte may contain anions other than oxygen (excluding sulfur anions and halogen anions). A "halide solid electrolyte" refers to a solid electrolyte that contains a halogen element but does not contain sulfur. A halide solid electrolyte may contain not only a halogen element but also oxygen.

[0086] Examples of sulfide solid electrolytes are Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 is.

[0087] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutes; (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or elemental substitutions thereof; (iv) Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an elemental substitution product thereof, or (v) Li3PO4 or its N-substituted derivatives is.

[0088] An example of a halide solid electrolyte is Li a Me' b Y c The compound is represented by Z6, where the formula: a+mb+3c=6, and c>0 is satisfied. Me' is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. Z is at least one selected from the group consisting of F, Cl, Br, and I. The value of m represents the valence of Me'.

[0089] "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in groups 1 to 12 of the periodic table (except hydrogen) and all elements in groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0090] To enhance 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.

[0091] Examples of halide solid electrolytes are Li3YCl6 or Li3YBr6.

[0092] When the electrolyte layer 202 contains the first solid electrolyte material, the negative electrode 203 may contain a sulfide solid electrolyte. This allows the sulfide solid electrolyte, which is electrochemically stable with respect to the negative electrode active material, to prevent the first solid electrolyte material and the negative electrode active material from coming into contact with each other. As a result, the battery has low internal resistance.

[0093] Examples of organic polymer solid electrolytes include compounds of polymer compounds and lithium salts. The 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.

[0094] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF) , LiN(SOCF)(SOCF), or LiC(SOCF). One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used.

[0095] 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 in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0096] The nonaqueous electrolyte contains a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent. Examples of the nonaqueous solvent include a cyclic carbonate ester solvent, a chain carbonate ester solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent. Examples of the cyclic carbonate ester solvent are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the chain carbonate ester solvent are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of the chain ether solvent are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of the cyclic ester solvent is γ-butyrolactone. An example of the chain ester solvent is methyl acetate. Examples of fluorine-containing solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from these may be used.

[0097] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L to 2 mol / L.

[0098] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0099] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums, or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums is.

[0100] An example of an anion found in ionic liquids is PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - is.

[0101] The ionic liquid may contain a lithium salt.

[0102] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving adhesion between particles.

[0103] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. Copolymers 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 of the above materials may also be used.

[0104] At least one selected from the group consisting of the positive electrode 201 and the negative electrode 203 may contain a conductive additive for the purpose of increasing electronic conductivity.

[0105] Examples of the conductive additive include: (i) graphites such as natural or synthetic graphite; (ii) carbon blacks such as acetylene black or ketjen black; (iii) conductive fibers such as carbon or metal fibers; (iv) fluorocarbons, (v) metal powders such as aluminum; (vi) conductive whiskers such as zinc oxide or potassium titanate; (vii) a conductive metal oxide, such as titanium oxide, or (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene To reduce costs, the above-mentioned conductive additive (i) or (ii) may be used.

[0106] Examples of the shape of the battery according to the second embodiment include a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, and a laminate type.

[0107] 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 by using a known method to fabricate a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order. [Example]

[0108] Hereinafter, the present disclosure will be described in more detail using examples and comparative examples.

[0109] Example 1 [Preparation of solid electrolyte materials] In a dry atmosphere with a dew point of −30°C or less (hereinafter referred to as the “dry atmosphere”), raw material powders of Li2O2, ZrCl4, and P2O5 were prepared 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 milled at 600 rpm for 24 hours using a planetary ball mill. In this way, a solid electrolyte material according to Example 1, consisting of Li, Zr, O, Cl, and P, was obtained.

[0110] [Composition analysis of solid electrolyte materials] The Li and Zr contents of the obtained solid electrolyte material according to Example 1 were measured by high-frequency inductively coupled plasma atomic emission spectroscopy using a high-frequency inductively coupled plasma optical emission spectrometer (iCAP7400, manufactured by ThermoFisher Scientific). The Cl content was measured by ion chromatography using an ion chromatograph (ICS-2000, manufactured by Dionex). The O content was measured by inert gas fusion-infrared absorption spectroscopy using an oxygen analyzer (EMGA-930, manufactured by Horiba, Ltd.). From the measurement results, the molar ratios Li / M, O / X, and A / M were calculated. Here, the A content was measured using the charged amount.

[0111] In the solid electrolyte material according to Example 1, the molar ratio Li / M was 1.4, the molar ratio O / X was 0.31, and the molar ratio A / M was 0.04.

[0112] [Evaluation of ionic conductivity] FIG. 3 shows a schematic diagram of a pressing die 300 used to evaluate the ionic conductivity of the solid electrolyte material.

[0113] The pressure molding die 300 had an upper punch 301, a frame 302, and a lower punch 303. The frame 302 was made of insulating polycarbonate. The upper punch 301 and the lower punch 303 were both made of electronically conductive stainless steel.

[0114] Using the pressure molding die 300 shown in FIG. 3, the ionic conductivity of the solid electrolyte material of Example 1 was measured by the following method.

[0115] 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 FIG. 3) was filled into a 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 an upper punch 301. In this way, an evaluation cell according to Example 1 was obtained.

[0116] While pressure was still applied to the evaluation cell, the upper punch 301 and the lower punch 303 were connected to a potentiostat (VersaSTAT4, manufactured by Princeton Applied Research) equipped with a frequency response analyzer. The upper punch 301 was connected to a working electrode and a potential measurement terminal. The lower punch 303 was connected to a counter electrode and a reference electrode. The ionic conductivity of the solid electrolyte material of Example 1 was measured at room temperature by electrochemical impedance measurement. As a result, the ionic conductivity measured at 22°C was 1.82 mS / cm.

[0117] [Battery construction] In an argon atmosphere having a dew point of -60°C or less, the solid electrolyte material according to Example 1 and LiCoO2 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.

[0118] In an insulating cylinder having an inner diameter of 9.5 mm, the solid electrolyte material (80 mg) according to Example 1 and the positive electrode mixture (8.2 mg) were stacked to obtain a laminate. 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.

[0119] Next, a Li-In alloy (thickness: 200 μm) was laminated on the solid electrolyte layer, and a pressure of 80 MPa was applied to this laminate to form a negative electrode.

[0120] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0121] Finally, the inside of the insulating tube was isolated from the outside atmosphere using an insulating ferrule, and the inside of the tube was sealed.

[0122] In this way, the battery according to Example 1 was obtained.

[0123] [Charge / discharge test] 4 is a graph showing the initial discharge characteristics of the battery according to Example 1. The horizontal axis represents discharge capacity, and the vertical axis represents voltage. The results shown in FIG. 4 were measured by the following method.

[0124] The battery according to Example 1 was placed in a thermostatic chamber maintained at 25°C.

[0125] The battery according to Example 1 was charged at a current value corresponding to a 0.05 C rate (20-hour rate) relative to the theoretical capacity of the battery until the voltage reached 3.6 V. The battery according to Example 1 was then discharged at a current value corresponding to a 0.05 C rate until the voltage reached 1.9 V.

[0126] As a result of the charge-discharge test, the battery according to Example 1 had an initial discharge capacity of 0.99 mAh.

[0127] (Examples 2 to 9 and Comparative Example 1) [Preparation of solid electrolyte materials] In Example 2, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.04.

[0128] In Example 3, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.06.

[0129] In Example 4, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.08.

[0130] In Example 5, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.1.

[0131] In Example 6, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.2.

[0132] In Example 7, raw material powders of Li2O2, ZrCl4, and P2O5 were prepared in a molar ratio of Li2O2:ZrCl4:P2O5=0.75:1:0.3.

[0133] In Example 8, raw material powders of Li2O2, ZrCl4, and B2O3 were prepared in a molar ratio of Li2O2:ZrCl4:B2O3=0.65:1:0.066.

[0134] In Example 9, raw material powders of Li2O2, ZrCl4, and B2O3 were prepared in a molar ratio of Li2O2:ZrCl4:B2O3=0.65:1:0.10.

[0135] In Comparative Example 1, LiCl and ZrCl4 were prepared as raw material powders in a molar ratio of LiCl:ZrCl4=2:1.

[0136] Except for the above, the solid electrolyte materials according to Examples 2 to 9 and Comparative Example 1 were obtained in the same manner as in Example 1.

[0137] [Composition analysis of solid electrolyte materials] In the same manner as in Example 1, the compositions of the solid electrolyte materials according to Examples 2 to 9 and Comparative Example 1 were analyzed.

[0138] The solid electrolyte material according to Example 2 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.35, and a molar ratio A / M of 0.08.

[0139] The solid electrolyte material according to Example 3 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.37, and a molar ratio A / M of 0.12.

[0140] The solid electrolyte material according to Example 4 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.39, and a molar ratio A / M of 0.16.

[0141] The solid electrolyte material according to Example 5 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.41, and a molar ratio A / M of 0.20.

[0142] The solid electrolyte material according to Example 6 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.52, and a molar ratio A / M of 0.40.

[0143] The solid electrolyte material according to Example 7 had a molar ratio Li / M of 1.5, a molar ratio O / X of 0.63, and a molar ratio A / M of 0.60.

[0144] The solid electrolyte material according to Example 8 had a molar ratio Li / M of 1.3, a molar ratio O / X of 0.30, and a molar ratio A / M of 0.13.

[0145] The solid electrolyte material according to Example 9 had a molar ratio Li / M of 1.3, a molar ratio O / X of 0.32, and a molar ratio A / M of 0.20.

[0146] The molar ratio Li / M of the solid electrolyte material according to Comparative Example 1 was 2.0. The molar ratio O / X was 0.

[0147] [Evaluation of ionic conductivity] The ionic conductivities of the solid electrolyte materials according to Examples 2 to 9 and Comparative Example 1 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0148] [Table 1]

[0149] (Consideration) As is clear from Table 1, the solid electrolyte materials according to Examples 1 to 9 have high ionic conductivity of 0.42 mS / cm or more at around room temperature.

[0150] As is clear from a comparison of Examples 1 to 5 with Examples 6 and 7, when the molar ratio A / M is 0.04 or more and 0.20 or less, the solid electrolyte material has higher ionic conductivity.

[0151] A comparison between Example 5 and Example 9, which have the same A / M value, shows that when A contains P, the ionic conductivity of the solid electrolyte material tends to improve.

[0152] Even when F, Br, or I is used as X, it is possible to achieve ionic conductivity comparable to that of the solid electrolyte materials of Examples 1 to 9. Furthermore, even in this case, the above-mentioned tendency holds true. The chemical and electrical properties of these elements are very similar to those of Cl, and it is possible to substitute some or all of Cl with these elements.

[0153] Even when Ti or Hf is used as M, it is possible to achieve ionic conductivity comparable to that of the solid electrolyte materials of Examples 1 to 9. Furthermore, even in this case, the above-mentioned tendency holds true. The chemical and electrical properties of these elements are similar to those of Zr, and Zr can be partially or completely substituted with these elements.

[0154] Batteries according to all examples were charged and discharged at room temperature.

[0155] The solid electrolyte materials according to Examples 1 to 9 do not contain sulfur and therefore do not generate hydrogen sulfide.

[0156] As described above, the solid electrolyte material according to the present disclosure 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. [Industrial Applicability]

[0157] The solid electrolyte material of the present disclosure is used, for example, in an all-solid-state lithium-ion secondary battery.

Claims

1. A compound essentially consisting of Li, M, O, X, and A, 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; A is at least one selected from the group consisting of 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 equal to or greater than 0.2 and equal to or less than 0.63; the molar ratio of A to M is 0.02 or more and 0.60 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. A includes P, The solid electrolyte material according to claim 1 .

5. the molar ratio of A to M is 0.04 or more and 0.20 or less; The solid electrolyte material according to claim 1 .

6. positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to any one of claims 1 to 5. battery.

Images