Solid electrolyte composition, solid electrolyte material, and method for producing solid electrolyte composition

Abstract

A solid electrolyte composition according to the present disclosure comprises a solid electrolyte containing Li, M1, O and X1, a halide containing M2 and X2, and an organic solvent. M1 is at least one element selected from the group consisting of Nb and Ta. M2 is at least one element selected from the group consisting of Nb and Ta. X1 is at least one element selected from the group consisting of F, Cl, Br and I. X2 is at least one element selected from the group consisting of F, Cl, Br and I.

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolyte composition, a solid electrolyte material, and a method for producing a solid electrolyte composition. [Background technology]

[0002] Patent Document 1 discloses a solid electrolyte composition using a sulfide solid electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 168505 Summary of the Invention [Problem to be solved by the invention]

[0004] When using a solid electrolyte, for example, when pulverizing the solid electrolyte, the solid electrolyte may be mixed with an organic solvent. In this case, the ionic conductivity of the solid electrolyte may decrease. Therefore, it is desired to suppress the decrease in the ionic conductivity of the solid electrolyte. [Means for solving the problem]

[0005] The present disclosure provides: a solid electrolyte comprising Li, M1, O, and X1; a halide containing M2 and X2; an organic solvent; Including, where: M1 is at least one selected from the group consisting of Nb and Ta; M2 is at least one selected from the group consisting of Nb and Ta; X1 is at least one selected from the group consisting of F, Cl, Br, and I; X2 is at least one selected from the group consisting of F, Cl, Br, and I, to provide a solid electrolyte composition. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of a solid electrolyte. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a flowchart showing an example of a method for producing a solid electrolyte material. [Figure 2] FIG. 2 is a schematic diagram showing a method for evaluating the lithium ion conductivity of a solid electrolyte material. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Findings that formed the basis of this disclosure) In the field of secondary batteries, where high energy density and large capacity are required, organic electrolyte solutions, in which electrolyte salts are dissolved in organic solvents, have traditionally been used. However, secondary batteries using organic electrolyte solutions have been known to have concerns about leakage and the possibility of increased heat generation in the event of a short circuit.

[0009] Meanwhile, all-solid-state secondary batteries, which use inorganic solid electrolytes instead of organic electrolytes, are gaining attention. All-solid-state secondary batteries do not leak. Because inorganic solid electrolytes are non-flammable, they are expected to suppress heat generation in the event of a short circuit.

[0010] Known inorganic solid electrolytes for use in all-solid-state secondary batteries include sulfide-based solid electrolytes containing sulfur as the primary component and oxide-based solid electrolytes containing metal oxides as the primary component. However, sulfide-based solid electrolytes can generate toxic hydrogen sulfide when reacting with water. Oxide-based solid electrolytes have low ionic conductivity. Therefore, the development of new solid electrolytes with high ionic conductivity is desired.

[0011] As a new solid electrolyte, for example, an oxyhalide-based solid electrolyte containing lithium, tantalum, oxygen, and at least one halogen element is expected. The oxyhalide-based solid electrolyte means a solid electrolyte containing oxygen and a halogen element.

[0012] To commercialize all-solid-state secondary batteries, a technology is required to prepare a fluid composition containing a solid electrolyte, apply it to the surface of an electrode or current collector, and form a solid electrolyte layer. Furthermore, to thin the solid electrolyte layer, a technology is also required to microparticulate the solid electrolyte to the order of a few micrometers.

[0013] To make the solid electrolyte into fine particles, the solid electrolyte may be mixed with an organic solvent and pulverized.

[0014] Therefore, the present inventors investigated the feasibility of pulverizing an oxyhalide-based solid electrolyte by a wet process using an organic solvent, using lithium ion conductivity as an index. As a result, it was found that when an oxyhalide-based solid electrolyte is pulverized by a wet process using an organic solvent, the lithium ion conductivity of the oxyhalide-based solid electrolyte may be significantly reduced compared to before pulverization. A similar phenomenon may occur when pulverization is not performed, i.e., when the solid electrolyte composition is formed into a predetermined shape and the organic solvent is removed. From the above perspective, the configuration of the present disclosure was obtained.

[0015] (Summary of one aspect of the present disclosure) The solid electrolyte composition according to the first aspect of the present disclosure comprises: a solid electrolyte comprising Li, M1, O, and X1; a halide containing M2 and X2; an organic solvent; Including, where: M1 is at least one selected from the group consisting of Nb and Ta; M2 is at least one selected from the group consisting of Nb and Ta; X1 is at least one selected from the group consisting of F, Cl, Br, and I; X2 is at least one selected from the group consisting of F, Cl, Br, and I.

[0016] According to the above configuration, it is possible to provide a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte.

[0017] In the second embodiment of the present disclosure, for example, in the solid electrolyte composition according to the first embodiment, X1 may contain Cl. By containing Cl, a solid electrolyte having high ionic conductivity can be provided.

[0018] In the third aspect of the present disclosure, for example, in the solid electrolyte composition according to the first or second aspect, M1 may contain Ta. By containing Ta, a solid electrolyte having high ionic conductivity can be provided.

[0019] In a fourth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to third aspects, the solid electrolyte may contain LiTaOCl4, which is suitable for application of the technology of the present disclosure.

[0020] In a fifth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to fourth aspects, X2 may contain Cl. According to such a configuration, a decrease in the ionic conductivity of the solid electrolyte can be effectively suppressed.

[0021] In a sixth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to fifth aspects, M2 may contain Ta. With this configuration, a decrease in the ionic conductivity of the solid electrolyte can be effectively suppressed.

[0022] In a seventh aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to sixth aspects, the halide may contain TaCl. TaCl can effectively suppress a decrease in ionic conductivity of the solid electrolyte.

[0023] In an eighth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to seventh aspects, M1 may be the same as M2. In this case, M2, which is a constituent element of the halide, is unlikely to adversely affect the solid electrolyte material produced by removing the organic solvent from the solid electrolyte composition.

[0024] In a ninth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to eighth aspects, X1 may be the same as X2. In this case, X2, which is a constituent element of the halide, is unlikely to adversely affect the solid electrolyte material produced by removing the organic solvent from the solid electrolyte composition.

[0025] In a tenth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to ninth aspects, the organic solvent may contain at least one selected from the group consisting of compounds having a halogen group and hydrocarbons, which are suitable as a solvent for the solid electrolyte composition.

[0026] In an eleventh aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to tenth aspects, the organic solvent may include at least one selected from the group consisting of tetralin, ethylbenzene, mesitylene, pseudocumene, xylene, cumene, 1,2,4-trichlorobenzene, chlorobenzene, 2,4-dichlorobenzene, o-chlorotoluene, 1,3-dichlorobenzene, p-chlorotoluene, 1,2-dichlorobenzene, 1,4-dichlorobutane, 2,4-dichlorotoluene, 3,4-dichlorotoluene, and pentane. The solid electrolyte containing oxygen and halogen elements has good dispersibility in these organic solvents.

[0027] In a twelfth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to eleventh aspects, the ratio of the mass of the halide to the total mass of the solid electrolyte and the halide may be 1% or more and 50% or less. With this configuration, a decrease in the ionic conductivity of the solid electrolyte can be effectively suppressed.

[0028] In the thirteenth aspect of the present disclosure, for example, in the solid electrolyte composition according to the twelfth aspect, the ratio may be 10% or more and 50% or less. When the ratio is 50% or less, the solid electrolyte material can have higher ionic conductivity.

[0029] The solid electrolyte material according to a fourteenth aspect of the present disclosure is a solid electrolyte comprising Li, M1, O, and X1; a halide containing M2 and X2; Including, where: M1 is at least one selected from the group consisting of Nb and Ta; M2 is at least one selected from the group consisting of Nb and Ta; X1 is at least one selected from the group consisting of F, Cl, Br, and I; X2 is at least one selected from the group consisting of F, Cl, Br, and I.

[0030] The above solid electrolyte material can exhibit the inherent ionic conductivity of a solid electrolyte.

[0031] A method for producing a solid electrolyte composition according to a fifteenth aspect of the present disclosure includes: A method for producing the solid electrolyte composition according to any one of the first to thirteenth aspects, synthesizing a solid electrolyte using a raw material containing a halide; mixing the solid electrolyte, the halide, and an organic solvent to prepare a solid electrolyte composition; Includes:

[0032] According to the above configuration, it is possible to provide a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte.

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0034] (First embodiment) In a first embodiment, the solid electrolyte composition includes a solid electrolyte, a halide, and an organic solvent. The solid electrolyte includes Li, M1, O, and X1. M1 is at least one selected from the group consisting of Nb and Ta. X1 is at least one selected from the group consisting of F, Cl, Br, and I. The solid electrolyte is a so-called oxyhalide-based solid electrolyte. The halide includes M2 and X2. M2 is at least one selected from the group consisting of Nb and Ta. X2 is at least one selected from the group consisting of F, Cl, Br, and I.

[0035] According to the above configuration, a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of a solid electrolyte can be provided. For example, even when a solid electrolyte is pulverized by wet pulverization using the solid electrolyte composition and then the organic solvent is removed, a solid electrolyte material that can fully exhibit the inherent ionic conductivity of the solid electrolyte can be obtained. The solid electrolyte material may be a powder or a solid electrolyte sheet.

[0036] The solid electrolyte composition may be in the form of a paste or a dispersion. In the solid electrolyte composition, particles and / or chunks of the solid electrolyte are mixed with an organic solvent. The viscosity of the solid electrolyte composition can be adjusted appropriately. For example, when the solid electrolyte composition is applied by a method such as a spray method, the viscosity of the solid electrolyte composition is relatively low. When the solid electrolyte composition is applied by a method such as a doctor blade method, the viscosity of the solid electrolyte composition is relatively high. When the purpose is to pulverize the particles or chunks of the solid electrolyte, the viscosity of the solid electrolyte composition can be adjusted appropriately depending on the pulverization method.

[0037] (solid electrolyte) The solid electrolyte includes Li, M1, O, and X1. In the solid electrolyte, X1 may include Cl. X1 may also be Cl. By including Cl, a solid electrolyte having high ionic conductivity can be provided.

[0038] In the solid electrolyte, M1 may include Ta. M1 may be Ta. By including Ta, a solid electrolyte having high ionic conductivity can be provided.

[0039] The solid electrolyte may consist only of Li, M1, O, and X1. The solid electrolyte may contain LiTaOCl4 or may be LiTaOCl4. While LiTaOCl4 exhibits high ionic conductivity, it tends to decrease in ionic conductivity upon wet processing. Therefore, LiTaOCl4 is suitable for application of the technology of the present disclosure.

[0040] In this specification, the phrase "consisting only of" means that, except for inevitable impurities, no other components are intentionally added.

[0041] The solid electrolyte may not contain sulfur (S), in which case the generation of hydrogen sulfide is prevented.

[0042] The solid electrolyte may be one type of oxyhalide-based solid electrolyte having a single composition, or may be a mixture of two or more types of oxyhalide-based solid electrolytes having different compositions.

[0043] The shape of the solid electrolyte is not particularly limited. The solid electrolyte may be in the form of particles. Examples of the particle shape are needle-like, spherical, or oval-spherical. The solid electrolyte may be in the form of a block. The solid electrolyte may have the shape of a pellet or a plate.

[0044] The solid electrolyte is produced, for example, by mechanochemical milling. Specifically, multiple types of raw material powders are mixed. The mixing ratio of the multiple types of raw material powders is adjusted to obtain a solid electrolyte with the desired composition. The raw material powders are then reacted with each other using a mixing device such as a planetary ball mill to obtain a reactant. The reactant may be fired in a vacuum or in an inert atmosphere. This results in a solid electrolyte with the desired composition.

[0045] (halides) The halide includes M2 and X2. X2 may include Cl. This configuration can effectively prevent a decrease in the ionic conductivity of the solid electrolyte. X2 may be Cl.

[0046] M2 may contain Ta. With this configuration, a decrease in the ionic conductivity of the solid electrolyte can be effectively suppressed. M2 may be Ta.

[0047] The halide may consist only of M2 and X2. The halide may contain TaCl5 or may be TaCl5. TaCl5 can effectively prevent a decrease in the ionic conductivity of the solid electrolyte.

[0048] M1 in the composition of the solid electrolyte may be the same as M2 in the composition of the halide. That is, when M1 is Ta, M2 is also Ta. In this case, M2, which is a constituent element of the halide, is unlikely to adversely affect the solid electrolyte material produced by removing the organic solvent from the solid electrolyte composition.

[0049] X1 in the composition of the solid electrolyte may be the same as X2 in the composition of the halide. That is, when X1 is Cl, X2 is also Cl. In this case, X2, which is a constituent element of the halide, is unlikely to adversely affect the solid electrolyte material produced by removing the organic solvent from the solid electrolyte composition.

[0050] The halide may contain at least one cation other than M2, such as Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, or Sm.

[0051] The halide may contain an anion other than X2.

[0052] The halide may be one compound having a single composition, or a mixture of two or more compounds having different compositions.

[0053] The halide may be crystalline or amorphous.

[0054] The shape of the halide is not particularly limited. The shape of the halide may be particulate. Examples of particulate shapes are needle-like, spherical, or oval-spherical. The halide may have a pellet or plate shape. In the solid electrolyte composition, the halide may be dispersed in the organic solvent while maintaining the particulate shape.

[0055] The mass ratio of the halide to the sum of the mass of the solid electrolyte and the mass of the halide may be 1% or more and 50% or less. This configuration can effectively prevent a decrease in the ionic conductivity of the solid electrolyte. This ratio in the solid electrolyte composition can be determined by known chemical analysis methods. For example, if the halide is crystalline, the mass ratio can be calculated by X-ray diffraction analysis. If the halide is amorphous, the mass ratio can be calculated by composition analysis such as ICP atomic emission spectroscopy.

[0056] The ratio may be 10% or more and 50% or less. If the ratio is 50% or less, the solid electrolyte material may have higher ionic conductivity. The lower limit of the ratio may be 5%. The upper limit of the ratio may be 20%.

[0057] A suitable range of the ratio may be defined by a combination of a lower limit and an upper limit selected from 1%, 5%, 10%, 20%, and 50%.

[0058] While solid electrolytes contain lithium, halides do not necessarily contain lithium. While solid electrolytes have lithium ion conductivity, halides do not necessarily contain lithium. These are also differences between the two.

[0059] The halide may be the same compound as the raw material used to synthesize the oxyhalide-based solid electrolyte. For example, the oxyhalide-based solid electrolyte is synthesized using a raw material containing a halide by a method such as mechanochemical milling. The solid electrolyte composition can be prepared by mixing the halide used in the synthesis, the synthesized oxyhalide-based solid electrolyte, and an organic solvent. This configuration allows for the production of a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte. The halide contained in the raw material for the solid electrolyte is unlikely to affect the resulting solid electrolyte material.

[0060] (organic solvent) The organic solvent may contain at least one selected from the group consisting of compounds having a halogen group and hydrocarbons, which are suitable as a solvent for the solid electrolyte composition.

[0061] A hydrocarbon is a compound consisting only of carbon and hydrogen. The hydrocarbon may be an aliphatic hydrocarbon. The hydrocarbon may be a saturated hydrocarbon or an unsaturated hydrocarbon. The hydrocarbon may be a linear or branched chain. The number of carbon atoms contained in the hydrocarbon is not particularly limited and may be 7 or more. By using a hydrocarbon, a solid electrolyte composition with excellent dispersibility can be obtained.

[0062] The hydrocarbon may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be a monocyclic or a polycyclic hydrocarbon. When the hydrocarbon has a ring structure, the oxyhalide-based solid electrolyte can be easily dispersed in an organic solvent. From the viewpoint of improving the dispersibility of the oxyhalide-based solid electrolyte in the solid electrolyte composition, the hydrocarbon may contain an aromatic hydrocarbon. The hydrocarbon may be an aromatic hydrocarbon.

[0063] The compound having a halogen group may consist of only carbon and hydrogen other than the halogen group. In other words, the compound having a halogen group refers to a compound in which at least one hydrogen atom contained in a hydrocarbon is substituted with a halogen group. Examples of halogen groups include F, Cl, Br, and I. The compound having a halogen group may have high polarity. The number of halogen groups contained in the compound having a halogen group is not particularly limited. The number of halogen groups may be, for example, one. The organic solvent may be a liquid capable of dispersing an oxyhalide-based solid electrolyte. The organic solvent does not need to dissolve an oxyhalide-based solid electrolyte.

[0064] According to the above configuration, it is possible to provide a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte.

[0065] The number of carbon atoms contained in the compound having a halogen group is not particularly limited and may be 7 or more. In this case, the volatility of the compound having a halogen group is reduced, so that the solid electrolyte composition can be stably produced. The compound having a halogen group may have a large molecular weight. That is, the compound having a halogen group may have a high boiling point.

[0066] The compound having a halogen group may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be a monocyclic or a polycyclic. When the compound having a halogen group has a ring structure, the oxyhalide-based solid electrolyte can be easily dispersed in the compound having a halogen group. The compound having a halogen group may include an aromatic hydrocarbon. The compound having a halogen group may be an aromatic compound.

[0067] The compound having a halogen group may have only a halogen group as a functional group. In this case, the number of halogens contained in the compound having a halogen group is not particularly limited. At least one halogen selected from the group consisting of F, Cl, Br, and I may be used as the halogen, or multiple halogens may be used. By using such a compound, the oxyhalide-based solid electrolyte can be easily dispersed, thereby obtaining a solid electrolyte composition with excellent dispersibility. As a result, the solid electrolyte composition has excellent lithium ion conductivity and can form a denser solid electrolyte material. By using such a compound, the solid electrolyte composition can easily form, for example, a dense solid electrolyte sheet with few pinholes, irregularities, etc.

[0068] The compound having a halogen group may be a halogenated hydrocarbon. A halogenated hydrocarbon refers to a compound in which all hydrogen atoms contained in a hydrocarbon are substituted with halogen groups. By using a halogenated hydrocarbon, an oxyhalide-based solid electrolyte can be easily dispersed, thereby obtaining a solid electrolyte composition with excellent dispersibility. As a result, the solid electrolyte composition has excellent lithium ion conductivity and can form a denser solid electrolyte material. By using a halogenated hydrocarbon, the solid electrolyte composition can easily form, for example, a dense solid electrolyte sheet with fewer pinholes, irregularities, etc.

[0069] The organic solvent may include at least one selected from the group consisting of, for example, tetralin, ethylbenzene, mesitylene, pseudocumene, xylene, cumene, 1,2,4-trichlorobenzene, chlorobenzene, 2,4-dichlorobenzene, o-chlorotoluene, 1,3-dichlorobenzene, p-chlorotoluene, 1,2-dichlorobenzene, 1,4-dichlorobutane, 3,4-dichlorotoluene, and pentane. Solid electrolytes containing oxygen and halogen elements have good dispersibility in these organic solvents. That is, oxyhalide-based solid electrolytes can be easily dispersed in organic solvents.

[0070] According to the above configuration, it is possible to provide a solid electrolyte composition suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte.

[0071] The boiling point of the organic solvent is not particularly limited and may be 100°C or higher and 250°C or lower. The organic solvent may be liquid at room temperature (25°C). Such organic solvents are less likely to volatilize at room temperature, allowing for stable production of solid electrolyte compositions. The organic solvent can be easily removed by drying. The organic solvent may be a liquid capable of dispersing an oxyhalide-based solid electrolyte.

[0072] The halide may also be dispersed in an organic solvent.

[0073] (Second embodiment) The second embodiment will be described below. The matters described in the first embodiment may be omitted as appropriate.

[0074] The second embodiment relates to a solid electrolyte material obtained by removing the organic solvent from the solid electrolyte composition according to the first embodiment. The solid electrolyte material may be an amorphous material such as a powder, or may be a finite material such as a solid electrolyte sheet.

[0075] The solid electrolyte material according to the second embodiment includes a solid electrolyte and a halide. The solid electrolyte material can exhibit the inherent ionic conductivity of a solid electrolyte. The solid electrolyte and the halide are as described in the first embodiment.

[0076] The solid electrolyte material has high lithium ion conductivity, for example, of 2.0 mS / cm or more.

[0077] The solid electrolyte material can be used in a battery having excellent charge / discharge characteristics. The battery is, for example, an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0078] The solid electrolyte material can be produced by the method described below.

[0079] Fig. 1 is a flowchart showing an example of a method for producing a solid electrolyte material. The production method shown in Fig. 1 includes a preparation step S01, a microparticulation step S02, and a removal step S03. However, these steps are not essential. For example, a solid electrolyte sheet may be produced using the solid electrolyte composition obtained through the preparation step S01.

[0080] The blending step S01 is a step of mixing materials to obtain a solid electrolyte composition. In the blending step S01, a solid electrolyte, a halide, and an organic solvent are mixed. In this manner, a solid electrolyte composition is obtained. In the blending step S01, the mixing method is not particularly limited. The respective ratios of the solid electrolyte, the halide, and the organic solvent can be adjusted as appropriate.

[0081] After the blending step S01, a micronization step S02 can be carried out.

[0082] The microparticulation step S02 is a step of pulverizing the solid electrolyte to form fine particles. In the microparticulation step S02, for example, the solid electrolyte composition and milling media are placed in a container and milling is performed by rotating the container. Such a milling method is a method using a roll mill, a pot mill, or a planetary ball mill. Alternatively, milling may be performed by placing milling media in a milling chamber equipped with a rotor, rotating the rotor at high speed, and passing the solid electrolyte composition through the milling chamber. Such a milling method is, for example, a method using a bead mill. A sieve or the like may be used to remove the milling media from the milled mixture. The milling conditions can be appropriately set depending on the milling machine.

[0083] The shape of the grinding media is, for example, spherical or round. The size of the grinding media affects the particle size of the ground solid electrolyte. For example, it is desirable to use spherical grinding media with a diameter of 1.0 mm or less.

[0084] The removing step S03 is performed, for example, after the microparticulating step S02.

[0085] The removal step S03 is a step of removing the organic solvent from the solid electrolyte composition.

[0086] The organic solvent may be removed from the solid electrolyte composition, for example, by drying under reduced pressure.

[0087] The reduced pressure drying refers to removing the organic solvent from the solid electrolyte composition in a pressure atmosphere lower than atmospheric pressure. The reduced pressure atmosphere is, for example, an atmosphere with a gauge pressure of -0.01 MPa or less. The reduced pressure drying may be vacuum drying. The vacuum drying refers to removing the organic solvent at a pressure equal to or lower than the vapor pressure at a temperature 20°C lower than the boiling point of the organic solvent. During the reduced pressure drying, the solid electrolyte composition may be dried by heating at an atmospheric temperature of 50°C or higher and 250°C or lower.

[0088] In the removal step S03, the organic solvent may be removed from the solid electrolyte composition by heating the solid electrolyte composition in an inert gas atmosphere. Heating may be performed while flowing an inert gas. Examples of the inert gas include nitrogen and argon. The ambient temperature during heating is, for example, 50°C or higher and 250°C or lower.

[0089] The presence of organic solvents can be confirmed by, for example, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), gas chromatography (GC), or gas chromatography mass spectrometry (GC / MS).

[0090] Through the above steps, the solid electrolyte material according to the second embodiment is obtained. [Example]

[0091] Hereinafter, the present disclosure will be described in detail with reference to examples.

[0092] Example 1 (Preparation of Solid Electrolyte Composition) 3.96 g of LiTaOCl4, 0.04 g of TaCl5, and 16 g of p-chlorotoluene were placed in the grinding pot of a planetary ball mill and gently stirred with a spatula. In this way, a solid electrolyte composition according to Example 1 was obtained. Hereinafter, LiTaOCl4 will be referred to as "LTOC."

[0093] (Atomization process) 25 g of spherical zirconia grinding media with a diameter of 0.5 mm was placed in the grinding pot of the planetary ball mill. The solid electrolyte composition was ground using a planetary ball mill (Fritsch, PULVERISETTE 7) at 300 rpm for 60 minutes. The grinding media were then removed using a sieve with a mesh size of 212 μm. In this way, a ground solid electrolyte composition (i.e., a finely divided solid electrolyte composition) was obtained.

[0094] (Removal of organic solvents) The crushed solid electrolyte composition was placed in a sealed glass beaker, and the sealed beaker was heated to 200°C while flowing nitrogen at a flow rate of 10 L / min, and the organic solvent was removed from the solid electrolyte composition over a period of 2 hours. In this way, a solid electrolyte material was obtained.

[0095] (Lithium ion conductivity measurement) 2 is a schematic diagram showing a method for evaluating the lithium ion conductivity of a solid electrolyte material. A pressure molding die 200 had an upper punch 201, a frame 202, and a lower punch 203. The frame 202 was made of insulating polycarbonate. The upper punch 201 and the lower punch 203 were both made of electronically conductive stainless steel.

[0096] Using the pressure molding die 200 shown in FIG. 2, the ionic conductivity of the solid electrolyte material was measured by the following method.

[0097] In a dry atmosphere having a dew point of −50° C. or less, the solid electrolyte material 101 according to Example 1 was filled into a pressure molding die 200. A pressure of 300 MPa was applied to the solid electrolyte material 101 using an upper punch 201 and a lower punch 203.

[0098] While the pressure was still applied, the upper punch 201 and the lower punch 203 were connected to a potentiostat (Bio-Logic, EC-Lab) equipped with a frequency response analyzer. The upper punch 201 was connected to a working electrode and a potential measurement terminal. The lower punch 203 was connected to a counter electrode and a reference electrode. The lithium ion conductivity of the solid electrolyte material 101 was measured at 25°C by electrochemical impedance measurement. As a result, the ion conductivity was found to be 3.4 × 10 -3 It was S / cm.

[0099] (Average particle size) The solid electrolyte material was observed with a scanning electron microscope (Hitachi High-Technologies Corporation, Regulus 8230, observation magnification 10,000x), and the unidirectional diameter (Ferret diameter) of 30 randomly selected primary particles was measured. The simple average of the obtained measurements was calculated. The calculated value was defined as the average particle diameter.

[0100] The solid electrolyte material according to Example 1 had an average particle size of 2.0 μm.

[0101] <Example 2> The solid electrolyte material of Example 2 was obtained in the same manner as in Example 1, except that 3.6 g of LTOC, 0.4 g of TaCl5, and 16 g of p-chlorotoluene were used.

[0102] The ionic conductivity and average particle size of the solid electrolyte material of Example 2 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 4.0 × 10 -3 The average particle size was 2.6 μm.

[0103] Example 3 A solid electrolyte material of Example 3 was obtained in the same manner as in Example 1, except that 3.2 g of LTOC, 0.8 g of TaCl5, and 16 g of p-chlorotoluene were used.

[0104] The ionic conductivity and average particle size of the solid electrolyte material of Example 3 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 4.1 × 10 -3 The average particle size was 1.9 μm.

[0105] Example 4 A solid electrolyte material of Example 4 was obtained in the same manner as in Example 1, except that 2 g of LTOC, 2 g of TaCl5, and 16 g of p-chlorotoluene were used.

[0106] The ionic conductivity and average particle size of the solid electrolyte material of Example 4 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 4.1 × 10 -3The average particle size was 1.8 μm.

[0107] <Example 5> A solid electrolyte material of Example 5 was obtained in the same manner as in Example 1, except that 3.2 g of LTOC, 0.8 g of TaBr5, and 16 g of p-chlorotoluene were used.

[0108] The ionic conductivity and average particle size of the solid electrolyte material of Example 5 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 2.9 × 10 -3 The average particle size was 1.8 μm.

[0109] Example 6 A solid electrolyte material of Example 6 was obtained in the same manner as in Example 1, except that 3.2 g of LTOC, 0.8 g of NbCl5, and 16 g of p-chlorotoluene were used.

[0110] The ionic conductivity and average particle size of the solid electrolyte material of Example 6 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 2.2 × 10 -3 The average particle size was 2.0 μm.

[0111] <Reference example 1> A solid electrolyte material of Reference Example 1 was obtained in the same manner as in Example 1, except that 4 g of LTOC and 16 g of p-chlorotoluene were used. That is, the solid electrolyte composition of Reference Example 1 did not contain any halide containing M2 and X2.

[0112] The ionic conductivity and average particle size of the solid electrolyte material of Reference Example 1 were measured in the same manner as in Example 1. As a result, the ionic conductivity was 1.4 × 10 -3 The average particle size was 1.4 μm.

[0113] The ionic conductivity and average particle diameter of the solid electrolyte materials of the examples and reference examples are shown in Table 1. In Table 1 and the discussion, the ratio of the mass of the halide to the total mass of the solid electrolyte and the halide is simply denoted as "mass ratio".

[0114]

Table 1

[0115] (Discussion) The solid electrolyte materials of Examples 1 to 6 had higher ionic conductivity compared to Reference Example 1. That is, the solid electrolyte compositions of Examples 1 to 6 maintained high ionic conductivity even when micronized.

[0116] As is clear from comparing Examples 2 to 4 with Example 1, when the mass ratio was 10% or more and 50% or less, the solid electrolyte material had higher ionic conductivity.

[0117] As described above, the solid electrolyte composition of the present disclosure was suitable for suppressing a decrease in the ionic conductivity of the solid electrolyte due to the micronization and the removal process of the organic solvent.

[0118] In this example, LiTaOCl4 was used as the solid electrolyte. However, the technology of the present disclosure is also useful for oxyhalide-based solid electrolytes containing niobium. Both tantalum and niobium belong to Group 5 of the periodic table and exhibit similar chemical properties. Also, the oxyhalide-based solid electrolyte containing Nb exhibits an ionic conductivity close to that of LiTaOCl4. Therefore, it is presumed that oxyhalide-based solid electrolytes containing Nb such as LiNbOCl4, LiTa x Nb 1-x OCl4 (0 < x < 1) also exhibit the same effect as LTOC.

Industrial Applicability

[0119] The solid electrolyte composition according to the present disclosure is used, for example, in the manufacture of all-solid-state lithium-ion secondary batteries.

Claims

1. a solid electrolyte comprising Li, M1, O, and X1; a halide comprising M2 and X2; an organic solvent; Including, where: M1 is at least one selected from the group consisting of Nb and Ta; M2 is at least one selected from the group consisting of Nb and Ta; X1 is at least one selected from the group consisting of F, Cl, Br, and I; X2 is at least one selected from the group consisting of F, Cl, Br, and I.

2. X1 contains Cl; The solid electrolyte composition according to claim 1 .

3. M1 includes Ta; The solid electrolyte composition according to claim 1 or 2.

4. The solid electrolyte is LiTaOCl 4 Including, The solid electrolyte composition according to claim 1 .

5. X2 contains Cl; The solid electrolyte composition according to claim 1 .

6. M2 includes Ta; The solid electrolyte composition according to claim 1 .

7. The halide is TaCl 5 Including, The solid electrolyte composition according to claim 1 .

8. M1 is identical to M2, The solid electrolyte composition according to claim 1 .

9. X1 is identical to X2; The solid electrolyte composition according to claim 1 .

10. the organic solvent contains at least one selected from the group consisting of compounds having a halogen group and hydrocarbons; The solid electrolyte composition according to claim 1 .

11. the organic solvent includes at least one selected from the group consisting of tetralin, ethylbenzene, mesitylene, pseudocumene, xylene, cumene, 1,2,4-trichlorobenzene, chlorobenzene, 2,4-dichlorobenzene, o-chlorotoluene, 1,3-dichlorobenzene, p-chlorotoluene, 1,2-dichlorobenzene, 1,4-dichlorobutane, 2,4-dichlorotoluene, 3,4-dichlorotoluene, and pentane; The solid electrolyte composition according to claim 10.

12. a ratio of the mass of the halide to the total mass of the solid electrolyte and the halide is 1% or more and 50% or less; The solid electrolyte composition according to claim 1 .

13. The ratio is equal to or greater than 10% and equal to or less than 50%. The solid electrolyte composition according to claim 12.

14. a solid electrolyte comprising Li, M1, O, and X1; a halide comprising M2 and X2; Including, where: M1 is at least one selected from the group consisting of Nb and Ta; M2 is at least one selected from the group consisting of Nb and Ta; X1 is at least one selected from the group consisting of F, Cl, Br, and I; X2 is at least one selected from the group consisting of F, Cl, Br, and I.

15. A method for producing the solid electrolyte composition according to any one of claims 1 to 13, synthesizing a solid electrolyte using a raw material containing a halide; mixing the solid electrolyte, the halide, and an organic solvent to prepare a solid electrolyte composition; A method for producing a solid electrolyte composition, comprising:

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