Solid electrolyte material and battery using the same

Abstract

This solid electrolyte material contains Li, M, O, and X. M is at least one selected from the group consisting of Nb and Ta. X is at least one selected from the group consisting of F, Cl, Br, and I. This solid electrolyte material has a first peak located within a range of a diffraction angle 2θ of from 13.49° to 13.59° and a second peak located within a range of a diffraction angle 2θ of from 14.82° to 14.92° in an x-ray diffraction pattern obtained by x-ray diffraction measurement using Cu-Kα rays. The intensity ratio of the first peak to the second peak is from 0.50 to 4.50.

Description

[Technical Field]

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

[0002] Patent Documents 1 and 2 disclose solid electrolyte materials containing Li, M, O, and X, where M is at least one element selected from the group consisting of Nb and Ta, and X is at least one element selected from the group consisting of Cl, Br, and I. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 137153 [Patent Document 2] International Publication No. 2020 / 137155 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a solid electrolyte material that has practical ionic conductivity and is capable of reducing the decrease in ionic conductivity due to heat. [Means for solving the problem]

[0005] The solid electrolyte material of the present disclosure is A solid electrolyte material comprising Li, M, O, and X, M is at least one selected from the group consisting of Nb and Ta; X is at least one selected from the group consisting of F, Cl, Br, and I; the solid electrolyte material has, in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation, a first peak located within a diffraction angle 2θ range of 13.49° or more and 13.59° or less, and a second peak located within a diffraction angle 2θ range of 14.82° or more and 14.92° or less; The intensity ratio of the first peak to the second peak is not less than 0.50 and not more than 4.50. [Effects of the Invention]

[0006] The present disclosure provides a solid electrolyte material that has practical ionic conductivity and can reduce the decrease in ionic conductivity due to heat. [Brief explanation of the drawings]

[0007] [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 X-ray diffraction patterns of the solid electrolyte materials according to Examples 1 to 3, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] (First embodiment) The solid electrolyte material according to the first embodiment contains Li, M, O, and X. M is at least one selected from the group consisting of Nb and Ta. X is at least one selected from the group consisting of F, Cl, Br, and I. In an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation, the solid electrolyte material according to the first embodiment has a first peak located within a diffraction angle 2θ range of 13.49° to 13.59°, and a second peak located within a diffraction angle 2θ range of 14.82° to 14.92°. The intensity ratio of the first peak to the second peak is 0.50 to 4.50. When multiple peaks exist within the diffraction angle 2θ range of 13.49° to 13.59°, the first peak is the peak with the greatest intensity among the multiple peaks. Furthermore, when multiple peaks exist within the range of diffraction angle 2θ of 14.82° or more and 14.92° or less, the second peak is the peak having the greatest intensity among the multiple peaks.

[0010] The solid electrolyte material according to the first embodiment, which contains Li, M, O, and X, contains a crystalline phase having the above-described X-ray diffraction pattern. Due to the inclusion of this crystalline phase, the solid electrolyte material according to the first embodiment has practical ionic conductivity and can reduce the decrease in ionic conductivity due to heat.

[0011] More specifically, in a solid electrolyte material containing Li, M, O, and X and containing a crystalline phase having the above X-ray diffraction pattern, paths for lithium ion diffusion are easily formed, and at the same time, evaporation of the constituent elements due to heat is suppressed. As a result, the solid electrolyte material according to the first embodiment can achieve practical ionic conductivity, and at the same time, can reduce the decrease in ionic conductivity due to heat. The solid electrolyte material according to the first embodiment can have, for example, high lithium ion conductivity and excellent heat resistance.

[0012] Here, an example of high lithium ion conductivity is, for example, 4.0 mS / cm or more at around room temperature. The solid electrolyte material according to the first embodiment can have an ion conductivity of, for example, 4.0 mS / cm or more.

[0013] Next, an example of heat to which the solid electrolyte material is exposed will be described. When manufacturing a large-scale battery, a high-temperature heat treatment process is required for the battery's positive electrode, electrolyte layer, and negative electrode for densification and bonding. The temperature in the heat treatment process is, for example, about 200°C. Even when heat treatment at about 200°C is performed, the decrease in ionic conductivity of the solid electrolyte material according to the first embodiment is reduced or does not occur. Thus, the solid electrolyte material according to the first embodiment has excellent heat resistance. Therefore, the solid electrolyte material according to the first embodiment can be used to obtain a battery with excellent charge / discharge characteristics.

[0014] The solid electrolyte material according to the first embodiment can maintain high lithium ion conductivity over the expected temperature range in which the battery will be used (for example, a range of −30° C. to 80° C.). Therefore, the battery using the solid electrolyte material according to the first embodiment can operate stably even in an environment with temperature changes.

[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 the battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0016] From the viewpoint of safety, it is desirable that the solid electrolyte material according to the first embodiment is substantially free of sulfur. The solid electrolyte material according to the first embodiment is substantially free of sulfur means that the solid electrolyte material does not contain sulfur as a constituent element, except for sulfur that is 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 desirable that the solid electrolyte material according to the first embodiment is free of sulfur. A sulfur-free solid electrolyte material does not generate hydrogen sulfide even when exposed to the atmosphere, and is therefore excellent in safety.

[0017] In order to enhance the ionic conductivity and heat resistance of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist essentially of Li, M, O, and X. Here, "the solid electrolyte material according to the first embodiment consists essentially of Li, M, O, and X" means that the ratio of the total amount of substance of Li, M, O, and X 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.

[0018] In order to enhance the ionic conductivity and heat resistance of the solid electrolyte material, the solid electrolyte material according to the first embodiment may consist of Li, M, O, and X only.

[0019] In order to enhance the ionic conductivity and heat resistance of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, X may contain Cl. X may be Cl.

[0020] In order to enhance the ionic conductivity and heat resistance of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, M may contain Ta. M may be Ta.

[0021] In order to enhance the ionic conductivity and heat resistance of the solid electrolyte material, the molar ratio of Li to M in the solid electrolyte material according to the first embodiment may be 1.2 or more and 1.4 or less.

[0022] The X-ray diffraction pattern of the solid electrolyte material according to the first embodiment can be obtained by X-ray diffraction measurement by the θ-2θ method using Cu-Kα radiation (wavelengths of 1.5405 Å and 1.5444 Å, ie, wavelengths of 0.15405 nm and 0.15444 nm).

[0023] The diffraction angle of a peak in an X-ray diffraction pattern is defined as the angle at which the signal-to-noise ratio (i.e., the ratio of signal S to background noise N) is 3 or more and the peak width is 10° or less, showing the maximum intensity. The half width is the maximum intensity of the X-ray diffraction peak. MAX When the intensity is I MAX The width is expressed as the difference between the two diffraction angles that are half the value of the square root of the diffraction angle.

[0024] As described above, in the X-ray diffraction pattern of the solid electrolyte material according to the first embodiment, the intensity ratio of the first peak to the second peak is 0.50 or more and 4.50 or less. The intensity ratio of the first peak to the second peak may be 0.70 or more and 1.72 or less, or may be 1.05 or more and 1.72 or less.

[0025] The upper and lower limits of the intensity ratio of the first peak to the second peak may be defined by any combination selected from the following numerical values: 0.50, 0.7, 1.0, 1.05, 1.5, 1.72, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.50.

[0026] The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of the shape include a needle shape, a sphere shape, and an oval sphere shape. The solid electrolyte material according to the first embodiment may be in the form of particles. The solid electrolyte material according to the first embodiment may be formed into a pellet or plate shape.

[0027] When the solid electrolyte material according to the first embodiment is particulate (e.g., 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. This allows the solid electrolyte material according to the first embodiment and other materials to be dispersed well. The median particle diameter refers to the particle size (d50) corresponding to 50% cumulative volume in the volume-based particle size distribution. The volume-based particle size distribution can be measured using a laser diffraction measurement device or an image analysis device.

[0028] 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.

[0029] <Method of manufacturing solid electrolyte material> The solid electrolyte material according to the first embodiment can be produced by the following method.

[0030] A raw material powder is prepared to have a desired composition, such as an oxide, hydroxide, halide, or oxyhalide.

[0031] As an example, in a solid electrolyte material composed of Li, Ta, O, and Cl (i.e., a solid electrolyte material where M is Ta and X is Cl), if the molar ratio Li / M when the raw materials are mixed is 1.3, Li2O2 and TaCl5 are mixed in a molar ratio of Li2O2:TaCl5 = 0.65:1.0. M and X are determined by selecting the raw material powders. The Li / M molar ratio is determined by selecting the mixing ratio of the raw material powders. The raw material powders may be mixed in a molar ratio that is adjusted in advance to offset composition changes that may occur in the synthesis process.

[0032] A reactant is obtained by firing a 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 a vacuum or inert gas atmosphere. The inert gas atmosphere may be, for example, an argon atmosphere or a nitrogen atmosphere. 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 materials 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.

[0033] The firing of the solid electrolyte material may cause a part of M or a part of X to evaporate. As a result, the value of the molar ratio Li / M of the obtained solid electrolyte material may be larger than the value calculated from the molar ratio of the prepared raw material powder.

[0034] By selecting the type of raw material powder, the mixing ratio of the raw material powder, and the reaction conditions, the position of the X-ray diffraction peak in the solid electrolyte material according to the first embodiment, that is, the structure of the crystalline phase, can be adjusted to the desired one.

[0035] The composition of the solid electrolyte material can be determined by, for example, inductively coupled plasma (ICP) atomic emission spectroscopy, ion chromatography, or inert gas fusion-infrared absorption spectroscopy. For example, the composition of Li and M can be determined by ICP atomic emission spectroscopy, the composition of X can be determined by ion chromatography, and O can be measured by inert gas fusion-infrared absorption spectroscopy.

[0036] (Second embodiment) The second embodiment will be described below, and the matters described in the first embodiment will be omitted as appropriate.

[0037] 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.

[0038] The battery according to the second embodiment contains the solid electrolyte material according to the first embodiment, and therefore, even when the battery is exposed to high temperatures, such as when the battery is subjected to a high-temperature heat treatment during its manufacture, the battery according to the second embodiment has excellent charge / discharge characteristics.

[0039] FIG. 1 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0040] 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.

[0041] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100 .

[0042] The electrolyte layer 202 contains an electrolyte material, such as a solid electrolyte material.

[0043] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100 .

[0044] 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.

[0045] 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).

[0046] 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.

[0047] In the present disclosure, "(A,B,C)" means "at least one selected from the group consisting of A, B, and C."

[0048] From the viewpoint of battery cost and safety, lithium phosphate may be used as the positive electrode active material.

[0049] 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. When lithium iron phosphate is used as the positive electrode active material, the oxidation reaction of the solid electrolyte material is suppressed. In other words, the formation of an oxide layer with low lithium ion conductivity is suppressed. As a result, the battery has high charge / discharge efficiency.

[0050] The positive electrode 201 may contain not only the solid electrolyte material according to the first embodiment but also a transition metal oxyfluoride as a positive electrode active material. Even if the solid electrolyte material according to the first embodiment is fluorinated with a transition metal fluoride, a resistance layer is unlikely to form. As a result, the battery has high charge / discharge efficiency.

[0051] Transition metal oxyfluorides contain oxygen and fluorine. For example, transition metal oxyfluorides have the formula Li p Me q O m F nIt may also be a compound represented by the following. Here, Me is at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and the mathematical formulas: 0.5 ≦ p ≦ 1.5, 0.5 ≦ q ≦ 1.0, 1 ≦ m < 2, and 0 < n ≦ 1 are satisfied. An example of such a transition metal oxyfluoride is Li 1.05 (Ni 0.35 Co 0.35 Mn 0.3 ) 0.95 O 1.9 F 0.1 is.

[0052] 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, in the positive electrode 201, the positive electrode active material particles 204 and the solid electrolyte particles 100 can form a good dispersion state. Thereby, the charge and discharge characteristics of the battery are improved. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the lithium diffusion rate in the positive electrode active material particles 204 is improved. Thereby, the battery can operate at high power.

[0053] The positive electrode active material particles 204 may have a median diameter larger than that of the solid electrolyte particles 100. Thereby, the positive electrode active material particles 204 and the solid electrolyte particles 100 can form a good dispersion state.

[0054] From the viewpoints 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.

[0055] 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.

[0056] 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, and X may be at least one selected from the group consisting of Cl and Br. Such a solid electrolyte material according to the first embodiment is less susceptible to oxidation than a sulfide solid electrolyte. As a result, an increase in the reaction overvoltage of the battery can be suppressed.

[0057] 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.

[0058] 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.

[0059] 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. Here, 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 206 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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. 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.

[0065] 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.

[0066] 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, an electrolyte layer made of another solid electrolyte material that is electrochemically more stable than the first solid electrolyte material may be further provided between the electrolyte layer 202 and the negative electrode 203 in order to more stably maintain the high ionic conductivity of the first solid electrolyte material.

[0067] 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).

[0068] 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 (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0069] 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 0.27 V or higher 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] Examples of oxide solid electrolytes include (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions, (ii) perovskite-type solid electrolytes such as (LaLi)TiO3, and (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or their elemental substitutions; (iv) Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an element-substituted product thereof, or (v) Li3PO4 or an N-substituted product thereof.

[0080] 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'.

[0081] "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).

[0082] 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.

[0083] Examples of halide solid electrolytes are Li3YCl6 or Li3YBr6.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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 solution, a gel electrolyte, or an ionic liquid in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The ionic liquid may contain a lithium salt.

[0094] At least one selected from 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] Examples of shapes of the battery according to the second embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type, and laminate type.

[0099] 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]

[0100] The present disclosure will now be described in more detail using examples. Example 1 [Preparation of solid electrolyte materials] In a dry atmosphere with a dew point of −30°C or less (hereinafter simply referred to as the “dry atmosphere”), raw material powders containing Li2O2 and TaCl5 were prepared in a molar ratio of Li2O2:TaCl5 = 0.65:1.0. These raw material powders were ground and mixed in a mortar to obtain a mixed powder. The mixed powder was placed in a quartz glass container filled with argon gas and fired at 320°C for 3 hours. The fired product was then ground in an agate mortar. In this way, a solid electrolyte material according to Example 1 was obtained. The molar ratio Li / M was 1.3. Note that this molar ratio was determined from the molar ratio of the raw material powders. The same applies to the molar ratio Li / M in Examples 2 and 3 and Comparative Examples 1 and 2 described below.

[0101] [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.

[0102] 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.

[0103] 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.

[0104] In a dry atmosphere, the powder of the solid electrolyte material according to Example 1 (i.e., the powder 101 of the solid electrolyte material in FIG. 3) was filled into the inside of the pressure molding die 300. Inside the pressure molding die 300, a pressure of 300 MPa was applied to the solid electrolyte material according to Example 1 using the upper punch 301.

[0105] While pressure was still applied to the evaluation cell, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research VersaSTAT4) 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 5.8 mS / cm.

[0106] [Heat resistance evaluation] To evaluate the heat resistance of the solid electrolyte material, the solid electrolyte material according to Example 1 was heat-treated in an argon gas atmosphere at 200°C for 3 hours. Then, the ionic conductivity of the solid electrolyte material according to Example 1 was measured at room temperature. The ionic conductivity was measured using the same method as described above in [Evaluation of ionic conductivity]. As a result, the ionic conductivity measured at 22°C was 6.6 mS / cm. Thus, the ionic conductivity of the solid electrolyte material was not reduced by the heat treatment. That is, the solid electrolyte material according to Example 1 had excellent heat resistance.

[0107] [X-ray diffraction] Fig. 4 is a graph showing the X-ray diffraction pattern of the solid electrolyte material according to Example 1. The results shown in Fig. 4 were measured by the following method.

[0108] The X-ray diffraction pattern of the solid electrolyte material of Example 1 was measured using an X-ray diffractometer (RIGAKU Corporation, MiniFlex600) in a dry atmosphere with a dew point of −45° C. or less. Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) was used as the X-ray source.

[0109] The solid electrolyte material according to Example 1 had a first peak and a second peak at 13.54° and 14.88°, respectively. The intensity ratio of the first peak to the second peak (hereinafter referred to as "intensity ratio I1 / I2") was 1.05.

[0110] (Examples 2 and 3, and Comparative Examples 1 and 2) [Preparation of solid electrolyte materials] In Example 2, Li2O2 and TaCl5 were prepared as raw material powders in a molar ratio of Li2O2:TaCl5=0.7:1.0, with a molar ratio Li / M of 1.4.

[0111] In Example 3, Li2O, LiOH, and TaCl5 were prepared as raw material powders in a molar ratio of Li2O:LiOH:TaCl5 = 0.4:0.4:1.0, with a molar ratio Li / M of 1.2.

[0112] Except for the above, the solid electrolyte materials of Examples 2 and 3 were obtained in the same manner as in Example 1.

[0113] In Comparative Example 1, Li2O2 and TaCl5 were prepared as raw material powders in a dry atmosphere, with a molar ratio of Li2O2:TaCl5 = 0.8:1.0. These raw material powders were ground and mixed in a mortar to obtain a mixed powder. The mixed powder was placed in a quartz glass container filled with argon gas and fired at 355°C for 3 hours. The fired product was ground in an agate mortar. In this way, the solid electrolyte material according to Example 1 was obtained. The molar ratio Li / M was 1.6.

[0114] In Comparative Example 2, Li2O and TaCl5 were prepared as raw material powders in a molar ratio of Li2O:TaCl5 = 0.6:1.0. The molar ratio Li / M was 1.2. Except for the above, the solid electrolyte material of Comparative Example 2 was obtained in the same manner as in Comparative Example 1.

[0115] [Evaluation of ionic conductivity] The ionic conductivities of the solid electrolyte materials according to Examples 2 and 3 and Comparative Examples 1 and 2 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0116] [Heat resistance evaluation] In the same manner as in Example 1, the ionic conductivities after the heat treatment were measured for the solid electrolyte materials of Examples 2 and 3 and Comparative Examples 1 and 2. The measurement results are shown in Table 1.

[0117] [X-ray diffraction] In the same manner as in Example 1, the X-ray diffraction patterns of the solid electrolyte materials according to Examples 2 and 3 and Comparative Examples 1 and 2 were measured. The measurement results are shown in FIG.

[0118] The solid electrolyte material according to Example 2 had a first peak and a second peak at 13.51° and 14.83°, respectively, and the intensity ratio I1 / I2 was 0.70.

[0119] The solid electrolyte material according to Example 3 had a first peak and a second peak at 13.54° and 14.85°, respectively, and the intensity ratio I1 / I2 was 1.72.

[0120] The solid electrolyte material according to Comparative Example 1 had a first peak and a second peak at 13.55° and 14.82°, respectively, and the intensity ratio I1 / I2 was 0.41.

[0121] The solid electrolyte material according to Comparative Example 2 had a first peak and a second peak at 13.58° and 14.92°, respectively, and the intensity ratio I1 / I2 was 4.75.

[0122] [Table 1]

[0123] (Consideration) As is clear from Table 1, the solid electrolyte materials of Examples 1 to 3 have high ionic conductivity of 4.0 mS / cm or more at around room temperature, and the ionic conductivity did not decrease even after heat treatment at 200°C for 3 hours.

[0124] As is clear from a comparison of Examples 1 to 3 with Comparative Example 1, by satisfying the value of the intensity ratio I1 / I2 of 0.5 or more, a solid electrolyte material can be realized in which the decrease in ionic conductivity is suppressed even after heat treatment at 200°C for 3 hours.

[0125] As is clear from a comparison of Examples 1 to 3 and Comparative Example 1 with Comparative Example 2, by satisfying the value of the intensity ratio I1 / I2 of 4.50 or less, a solid electrolyte material can be realized in which the decrease in ionic conductivity is suppressed even after heat treatment.

[0126] The solid electrolyte materials according to Examples 1 to 3 do not contain sulfur and therefore do not generate hydrogen sulfide.

[0127] As described above, the solid electrolyte material according to the present disclosure has practical ionic conductivity and can reduce the decrease in ionic conductivity due to heat. Therefore, the solid electrolyte material according to the present disclosure is suitable for providing a battery with excellent charge-discharge characteristics. [Industrial Applicability]

[0128] The battery of the present disclosure is used, for example, in an all-solid-state lithium-ion secondary battery.

Claims

1. A solid electrolyte material comprising Li, M, O, and X, M is at least one selected from the group consisting of Nb and Ta; X is at least one selected from the group consisting of F, Cl, Br, and I; the molar ratio of Li to M is 1.2 or more and 1.4 or less; the solid electrolyte material has, in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu—Kα radiation, a first peak located within a diffraction angle 2θ range of 13.49° or more and 13.59° or less, and a second peak located within a diffraction angle 2θ range of 14.82° or more and 14.92° or less; an intensity ratio of the first peak to the second peak is 0.50 or more and 4.50 or less; Solid electrolyte material.

2. X contains Cl; The solid electrolyte material according to claim 1 .

3. The solid electrolyte material according to claim 1 or 2, wherein M includes Ta.

4. The intensity ratio is 0.70 or more and 1.72 or less. The solid electrolyte material according to claim 1 .

5. positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode; 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 4. battery.

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