Halide solid electrolyte production method, halide solid electrolyte, positive electrode material, and battery

Abstract

A solid electrolyte production method according to the present disclosure is a method for producing a halide solid electrolyte containing Li, Ti, M, and X. M is at least one element selected from the group consisting of metal elements (excluding Li and Ti) and metalloid elements, and X is at least one selected from the group consisting of F, Cl, Br, and I. The production method comprises: (A) subjecting at least one Li source selected from the group consisting of simple oxides and simple carbonates of Li, at least one Ti source selected from the group consisting of simple oxides and simple carbonates of Ti, and at least one M source selected from the group consisting of simple oxides and simple carbonates of M to a halogenation treatment to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M; and (B) synthesizing the halide solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M.

Description

Method for producing halide solid electrolyte, halide solid electrolyte, positive electrode material, and battery

[0001] The present disclosure relates to a method for producing a halide solid electrolyte, a halide solid electrolyte, a positive electrode material, and a battery.

[0002] Patent Document 1 discloses a halide-based solid electrolyte material. Patent Document 2 discloses a halide-based solid electrolyte material as a solid electrolyte material that coats the surface of a positive electrode active material.

[0003] International Publication No. 2021 / 186809 International Publication No. 2021 / 187391

[0004] An object of the present disclosure is to provide a novel production method capable of synthesizing, at low cost, a halide solid electrolyte having excellent ionic conductivity comparable to that of halide solid electrolytes produced by conventional production methods.

[0005] The method for producing a halide solid electrolyte according to the present disclosure is a method for producing a halide solid electrolyte containing Li, Ti, M, and X, wherein M is at least one element selected from the group consisting of metal elements (excluding Li and Ti) and metalloid elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I. The method includes: (A) subjecting at least one Li source selected from the group consisting of simple oxides and simple carbonates of Li, at least one Ti source selected from the group consisting of simple oxides and simple carbonates of Ti, and at least one M source selected from the group consisting of simple oxides and simple carbonates of M to a halogenation treatment to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M, respectively; and (B) synthesizing the halide solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M.

[0006] The present disclosure provides a novel production method that can synthesize, at low cost, a halide solid electrolyte having excellent ionic conductivity comparable to that of halide solid electrolytes produced by conventional production methods.

[0007] FIG. 1 is a flowchart showing an example of a method for producing a halide solid electrolyte according to a first embodiment. FIG. 2 is a flowchart showing an example of a method for producing a halide solid electrolyte according to a second embodiment. FIG. 3 is a flowchart showing a modified example of the method for producing a halide solid electrolyte according to the second embodiment. FIG. 4 is a flowchart showing an example of a method for producing a halide solid electrolyte according to a third embodiment. FIG. 5 is a cross-sectional view of a battery 1000 according to a fourth embodiment. FIG. 6A is a graph showing an X-ray diffraction pattern of a halide solid electrolyte after heat treatment and before pulverization treatment in the production method of Example 1. FIG. 6B is a graph showing X-ray diffraction patterns of the halide solid electrolyte after pulverization treatment obtained in Example 1 and the halide solid electrolyte obtained in Comparative Example 1.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0009] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, any component that is not described in an independent claim that represents a top concept will be described as an optional component.

[0010] First Embodiment A method for producing a halide solid electrolyte according to a first embodiment will be described below.

[0011] The manufacturing method according to the first embodiment is a method for manufacturing a halide solid electrolyte containing Li, Ti, M, and X. Here, M is at least one element selected from the group consisting of metal elements (excluding Li and Ti) and metalloid elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0012] The production method according to the first embodiment includes: (A) subjecting at least one Li source selected from the group consisting of simple oxides and simple carbonates of Li, at least one Ti source selected from the group consisting of simple oxides and simple carbonates of Ti, and at least one M source selected from the group consisting of simple oxides and simple carbonates of M to a halogenation treatment to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M, respectively; and (B) synthesizing the halogenated solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M.

[0013] "Semi-metallic elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements included in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). In other words, "metallic elements" are a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0014] The term "simple oxide" refers to an oxide whose cation is composed of only one type of cation. That is, a simple oxide of Li is an oxide whose cation is only Li ions, a simple oxide of Ti is an oxide whose cation is only Ti ions, and a simple oxide of M is an oxide whose cation is only M ions. When the halide solid electrolyte according to the first embodiment contains multiple elements as M, simple oxides of each of those elements are used. For example, when M is M A and M B In the case of two elements, M A Simple oxides of M B Simple oxides of

[0015] The term "simple carbonate" refers to a carbonate whose cation is composed of only one type of cation. That is, a simple carbonate of Li is a carbonate whose cation is only Li ions, a simple carbonate of Ti is a carbonate whose cation is only Ti ions, and a simple carbonate of M is a carbonate whose cation is only M ions. When the halide solid electrolyte according to the first embodiment contains multiple elements as M, simple carbonates of each of those elements are used. For example, when M is M A and M B In the case of two elements, M A Simple carbonates and M B Simple carbonates are used.

[0016] "Simple halide" means a halide whose cation is composed of only one type of cation. That is, a simple halide of Li is a halide whose cation is only Li ions, a simple halide of Ti is a halide whose cation is only Ti ions, and a simple halide of M is a halide whose cation is only M ions. When the halide solid electrolyte according to the first embodiment contains multiple elements as M, simple halides of each of those elements can be obtained by the halogenation treatment. For example, when M is M A and M B In the case of two elements, M A Simple halides of M B Simple halides of the formula are used.

[0017] In the production method according to the first embodiment, relatively inexpensive materials with excellent atmospheric stability, such as simple oxides and simple carbonates, are used as the Li source, Ti source, and M source. Therefore, according to the production method according to the first embodiment, a halide solid electrolyte having excellent ionic conductivity comparable to that of halide solid electrolytes produced by conventional production methods can be synthesized stably at low cost.

[0018] Furthermore, the simple oxides and simple carbonates used as the Li source, Ti source, and M source are generally harder materials than halides. Therefore, in the production method according to the first embodiment, unlike when halides are used as raw materials, the raw materials are easily pulverized and microparticulated. Therefore, if the raw materials are microparticulated at the raw material stage and then subjected to halogenation treatment and solid electrolyte synthesis, a fine halide solid electrolyte can be easily produced. In this way, the production method according to the first embodiment uses raw materials that are easy to handle for microparticulation, such as pulverization, and is therefore also suitable for producing a fine halide solid electrolyte.

[0019] The Li simple halide, Ti simple halide, and M simple halide obtained in (A) above may contain oxygen ions as anions in addition to halogen elements. For example, the Ti simple halide may contain a fluoride oxide, such as TiF2O, containing oxygen ions and fluorine ions as anions. This allows synthesis without using unstable halides such as TiF4, which easily evaporates even when handled at room temperature, thereby suppressing compositional deviations in the solid electrolyte. Therefore, solid electrolytes with desired compositions and properties can be produced with high reproducibility and precision (i.e., high purity). NH4F, an example of an F source that replaces the oxygen in TiF2O with F, may be added in a subsequent solid-state reaction step to completely fluorinate the TiF2O, replacing the remaining oxygen with fluorine. The NH4F used to completely fluorinate TiF2O in this process can be obtained by, for example, adding a predetermined halogen-containing material and uniformly mixing it with each halide in a mixing step before firing. As TiF2O is fluorinated (in a highly stable form such as a halogenated oxide), a solid-phase reaction occurs with LiF and AlF3, synthesizing the solid electrolyte according to the embodiment. This suppresses the problem of composition fluctuations caused by evaporation and deliquescence of TiF4, and suppresses the formation of unnecessary precipitated phases, allowing the synthesis of a halide solid electrolyte with high compositional precision.

[0020] The above (A) may include: (A-0) pulverizing at least one selected from the group consisting of a Li source, a Ti source, and an M source; and (A-1) after the above (A-0), subjecting each of the Li source, the Ti source, and the M source to a halogenation treatment to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M.

[0021] The above (A) includes the above (A-0) and (A-1), that is, the starting materials, that is, the Li source, the Ti source, and the M source, are pulverized to fine powder and then each is subjected to a halogenation treatment, and the resulting halides are used to synthesize in the above (B). This makes it possible to produce a fine halide solid electrolyte more easily and at lower cost than conventional production methods that use relatively soft halides as raw materials.

[0022] In the above (A), the halogenation treatment of the Li source, Ti source, and M source may be performed at a temperature of 150°C or higher. This allows the Li source, Ti source, and M source to be converted to halides before they harden due to sintering or grow larger due to grain growth, thanks to the halogenation treatment at a relatively low temperature. Therefore, such a heat treatment temperature is suitable for producing a fine halide solid electrolyte. Furthermore, the resulting solid electrolyte is easy to pulverize, thereby suppressing contamination during pulverization. The halogenation treatment temperature is preferably, for example, 150°C or higher and 450°C or lower. Therefore, a useful halide solid electrolyte can be obtained that can be finely pulverized and exhibits suppressed deterioration in properties. The heat treatment for the halogenation treatment can be performed in any atmosphere suitable for conversion to various halides, such as air, nitrogen, or a reducing atmosphere.

[0023] In the above (A), the halogenation treatment of the Li source, the Ti source, and the M source may be carried out, for example, by heat treating a thermally decomposable halogen-containing material.

[0024] By performing halogenation treatment by heat treatment of a thermally decomposable halogen-containing material, simple oxides or simple carbonates used as Li, Ti, and M sources can be converted to halides with high productivity by controlling the heat treatment conditions. Controlling the heat treatment conditions includes, for example, temperature control or selection of the heat treatment atmosphere. The heat treatment atmosphere can be, for example, air, nitrogen, or a reducing gas. The temperature or progress of halogenation can also be controlled by using multiple halogen-containing materials with different thermal decomposition properties (e.g., thermal decomposition temperature and time required for thermal decomposition) or by adjusting the particle size of the halogen-containing materials. Therefore, various oxides and carbonates can be stably and uniformly halogenated.

[0025] When a thermally decomposable halogen-containing substance is used in the halogenation treatment of the Li source, the Ti source, and the M source, in the production method according to the first embodiment, (A) may include: (A-1-1) mixing the Li source with a first halogen-containing substance, mixing the Ti source with a second halogen-containing substance, and mixing the M source with a third halogen-containing substance; and (A-1-2) heat-treating the first mixture containing the Li source and the first halogen-containing substance, the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance, each obtained in (A-1-1), thereby halogenating the Li source, the Ti source, and the M source.

[0026] In the production method according to the first embodiment, by carrying out the above (A-1-1) and (A-1-2), a heat treatment for halogenation can be carried out on a homogeneous mixture of the starting materials and the halogen-containing material. Furthermore, the contact area between the starting materials and the halogen-containing material can be increased. Therefore, in this case, the halogenation of the starting materials can be promoted uniformly and evenly throughout the Li source, Ti source, and M source, respectively. Therefore, a homogeneous halide solid electrolyte with excellent properties can be obtained.

[0027] 1 is a flowchart showing an example of a method for producing a halide solid electrolyte according to the first embodiment. Here, as an example of the production method according to the first embodiment, an example of a production method in which the above (A-0) and (A-1) are performed will be described. Furthermore, in the example described here, the above (A-1) is performed in which the above (A-1-1) and (A-1-2) are performed.

[0028] As shown in FIG. 1 , in one example of the production method according to the first embodiment, first, in a step corresponding to the above-mentioned (A-0), at least one selected from the group consisting of a Li source, a Ti source, and an M source is pulverized. In this example, for example, all of the Li source, the Ti source, and the M source are pulverized (S11). Next, in a step corresponding to the above-mentioned (A-1-1), the Li source and a first halogen-containing substance are mixed, the Ti source and a second halogen-containing substance are mixed, and the M source and a third halogen-containing substance are mixed (S12). Next, in a step corresponding to the above-mentioned (A-1-2), the obtained first mixture containing the Li source and the first halogen-containing substance, the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance are each heat-treated, thereby subjecting the Li source, the Ti source, and the M source to a halogenation treatment (S13). Next, in a step corresponding to the above (B), a halide solid electrolyte is synthesized using the obtained simple halide of Li, simple halide of Ti, and simple halide of M (S14). This results in a halide solid electrolyte containing Li, Ti, M, and X.

[0029] Hereinafter, the starting materials (i.e., the Li source, the Ti source, and the M source), the halogen-containing substance, and each of the steps corresponding to (A-0), (A-1-1), (A-1-2), and (B) will be specifically described.

[0030] <Starting Materials (Li Source, Ti Source, and M Source)> As described above, each of the Li source, Ti source, and M source, which are starting materials, is at least one selected from the group consisting of simple oxides and simple carbonates.

[0031] As the Li source, for example, Li2O and Li2CO3 can be used.

[0032] As the Ti source, for example, TiO2 can be used.

[0033] As the M source, a simple oxide of M or a simple carbonate of M can be used. M may contain Al. When M contains Al, a halide solid electrolyte with high ionic conductivity can be obtained. M may also be Al. For example, when M contains Al, Al2O3 can be used as the Al source.

[0034] The Li source, Ti source, and M source may be, for example, particulate. This allows the halogenation of the Li source, Ti source, and M source (i.e., substitution of the halogen element with the oxygen element) to proceed from the particle surface, shortening the reaction distance and increasing the reaction area. This facilitates the halogenation of the raw materials and the solid-state reaction (i.e., the synthesis reaction in step (B) above). This allows the Li source, Ti source, and M source to be halogenated homogeneously and in a short time. Furthermore, intermediate products and reaction residues such as carbonates that are generated when the reaction is insufficient can be reduced, thereby enabling the production of a homogeneous halide solid electrolyte with excellent properties. Furthermore, in this case, the high reactivity of halogenation, etc., allows the solid electrolyte to be synthesized in a short time and at a low temperature, resulting in excellent productivity.

[0035] Although smaller particle sizes of the Li source, Ti source, and M source are more suitable for halogenation, they may be more likely to aggregate or to fuse together during halogenation. Therefore, appropriate particle sizes and particle shapes may be selected in consideration of handling. The average particle diameters of the Li source, Ti source, and M source particles may be, for example, 1 μm or less.

[0036] The average particle diameters of the Li source, Ti source, and M source are median diameters of the Li source, Ti source, and M source, and refer to particle diameters (d50) corresponding to 50% cumulative volume, determined from particle size distributions measured on a volume basis by a laser diffraction scattering method. The same applies to the average particle diameters of halogen-containing substances specified in this specification.

[0037] <Halogen-containing substance> The halogen-containing substance is thermally decomposable. For example, when the halide solid electrolyte to be produced contains F as the halogen element X, a fluorine-containing substance that serves as a fluorine source is used as the halogen-containing substance.

[0038] The thermal decomposition onset temperature of the halogen-containing substance used may be, for example, 100° C. or higher and 600° C. or lower. When the halogen-containing substance has a thermal decomposition onset temperature within the above temperature range, the halogen-containing substance has stability during storage and handling, such as mixing, and the obtained halide solid electrolyte can be prevented from becoming too hard.

[0039] The halogen element X may contain F or may be F. This makes it possible to obtain a halide solid electrolyte having excellent stability (particularly excellent electrochemical stability and heat resistance) and high ionic conductivity.

[0040] The halogen-containing material may be, for example, particulate. This improves the thermal decomposition property of the halogen-containing material and increases the contact area between the starting materials, the Li source, Ti source, and M source, and the halogen-containing material. This allows for efficient halogenation of the Li source, Ti source, and M source. Furthermore, the halogenation reaction can be controlled by the particle shape of the halogen-containing material. For example, by reducing the particle size of the halogen-containing material, the temperature and rate of halogenation of the Li source, Ti source, and M source can be increased. Furthermore, by mixing the Li source, Ti source, and M source with a particulate halogen-containing material, homogeneous halogenation of the Li source, Ti source, and M source is possible. Furthermore, precise control of the halogen content is possible. This allows for the synthesis of a desired halide solid electrolyte. Furthermore, since only the amount of halogen-containing material required for halogenation of the Li source, Ti source, and M source can be used, excess halogen gas emissions can be suppressed. This reduces the environmental impact and also reduces the impact on corrosion of furnace materials, etc.

[0041] The halogen-containing substance may have, for example, an average particle size of 0.5 μm or more and 500 μm or less, an average particle size of 0.5 μm or more and 150 μm or less, an average particle size of 0.5 μm or more and 200 μm or less, or an average particle size of 0.5 μm or more and 100 μm or less. As with the Li source, Ti source, and M source, the halogen-containing substance may also have any particle size and shape.

[0042] The average particle size of the halogen-containing material may be larger than the average particle size of the starting materials, the Li source, the Ti source, and the M source. This results in a state in which the surface areas of the Li source, the Ti source, and the M source are larger than the halogen-containing material, i.e., the exposed surface areas (i.e., the exposed areas) of the Li source, the Ti source, and the M source are larger. Therefore, halogenation easily proceeds from the particle surfaces of the Li source, the Ti source, and the M source, thereby enabling the production of homogeneous halides of Li, Ti, and M. The average particle size of the halogen-containing material may be 5 μm or more and 100 μm or less, 5 μm or more and 20 μm or less, 50 μm or more and 200 μm or less, 50 μm or more and 100 μm or less, or 50 μm or more and 20 μm or less. The average particle size of the halogen-containing material can be appropriately adjusted taking into account the halogenation temperature or reactivity. For example, increasing the average particle size of the halogen-containing material increases the heat treatment temperature for the halogenation treatment.

[0043] The halogen-containing material may include an ammonium salt. Ammonium salts begin to thermally decompose at relatively low temperatures (e.g., about 150°C). Therefore, ammonium salts are unlikely to remain as unnecessary inorganic components in the final halide solid electrolyte, allowing the Li source, Ti source, and M source to be halogenated at low temperatures. Halogenation at low temperatures refers to the conversion of the Li source, Ti source, and M source into halides, for example, at a temperature range of about 150°C or higher and 600°C or lower. Therefore, by using ammonium salts as the halogen-containing material, a halide solid electrolyte can be synthesized without excessive sintering. Therefore, a halide solid electrolyte with excellent pulverizability can be synthesized. Because a halide solid electrolyte with excellent pulverizability can be synthesized, using ammonium salts as the halogen-containing material is also suitable for producing fine halide solid electrolytes. Furthermore, energy savings during synthesis are achieved, and the temperature rise and fall times are reduced, thereby improving productivity. Furthermore, the low-temperature synthesis improves the durability of furnace materials, significantly reducing the running costs and replacement frequency of synthesis components. As the halogen-containing substance, only ammonium salts may be used.

[0044] The ammonium salt may contain NH4F. NH4F is a highly decomposable fluorine source and can effectively fluorinate the Li source, Ti source, and M source. Therefore, NH4F can convert the Li source, Ti source, and M source into fluorides without leaving any inorganic substances by thermal decomposition at a low temperature (e.g., about 150°C) and at a fast decomposition rate. Note that ammonium salts of other halogen elements, such as NH4Cl and NH4Br, are also thermally decomposable and can be similarly used as halogen sources.

[0045] The halogen-containing material may include a resin. By including a resin as the halogen-containing material, the halogen-containing material can halogenate the Li source, the Ti source, and the M source without leaving any inorganic substances while being thermally decomposed at a relatively high temperature (e.g., about 450°C or higher and 600°C or lower). Therefore, the method of including a resin as the halogen-containing material is suitable for the case where the halogenation of the Li source, the Ti source, and the M source is to be carried out at a relatively high temperature (e.g., about 450°C or higher and 600°C or lower).

[0046] An example of a resin used as the halogen-containing material is a fluororesin. For example, polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used. Fluororesins such as PTFE can halogenate the Li source, Ti source, and M source while being pyrolyzed at a relatively high temperature (e.g., about 450°C or higher and 600°C or lower). Therefore, a method using a fluororesin as the halogen-containing material is suitable for carrying out halogenation at a relatively high temperature (e.g., about 450°C or higher and 600°C or lower).

[0047] The halogen-containing substance may contain, for example, a substance that does not substantially include inorganic components, except for halogen elements, generated by thermal decomposition by the heat treatment in (A) in the halide solid electrolyte to be produced. The halogen-containing substance is required to replace the halogen elements generated by thermal decomposition by the heat treatment in (A) with oxygen elements from the Li source, Ti source, and M source, while preventing other components from being mixed as inorganic residues into the finally obtained halide solid electrolyte. By using a substance that does not substantially include inorganic components, except for halogen elements, generated by thermal decomposition by the heat treatment in the finally obtained halide solid electrolyte, the mixing of inorganic residues into the halide solid electrolyte can be suppressed, and a desired halide solid electrolyte can be obtained. Examples of halogen-containing substances that do not substantially include inorganic components, except for halogen elements, generated by thermal decomposition by the heat treatment in the finally obtained halide solid electrolyte include substances in which inorganic components, except for halogen elements, generated by thermal decomposition by the heat treatment are gasified and discharged. In this specification, the phrase "the halide solid electrolyte to be produced is substantially free of inorganic components, except for halogen elements, that are generated by thermal decomposition through heat treatment" means that the content of the inorganic components in the halide solid electrolyte is, for example, 0.5 mass % or less.

[0048] The halogen-containing material may contain multiple types of halogen-containing compounds. For example, both ammonium salt and fluororesin can be used as the halogen-containing material. Alternatively, a mixture of multiple types of halogen-containing compounds having different particle sizes may be used. This allows the temperature and reactivity of the halogenation of the Li source, Ti source, and M source to be adjusted. Therefore, for example, the temperature range over which the halogen-containing material acts as a halogen source can be widely controlled, and the conversion temperature of the Li source, Ti source, and M source to halides can be controlled over a wide range. This makes it easy to obtain a desired halide solid electrolyte.

[0049] The amount of the halogen-containing substance used is not particularly limited, as long as it is sufficient to halogenate the entire amount of the compound to be halogenated.For example, in the reaction of halogenating the compound to be halogenated, the molar amount of the halogen-containing substance for stoichiometrically halogenating the entire compound (i.e., stoichiometrically equivalent molar amount, in other words, the molar amount required for completely replacing the anion of the compound to be halogenated with a halogen anion such as F) is taken as 100%, and the amount of the halogen-containing substance may be, for example, 103% or more and 150% or less, 103% or more and 130% or less, or 103% or more and 110% or less.

[0050] <Regarding (A-0)> In (A-0), at least one selected from the group consisting of a Li source, a Ti source, and an M source is pulverized. All of the Li source, the Ti source, and the M source may be pulverized.

[0051] By pulverizing the Li source, Ti source, and M source, which are simple oxides and / or simple carbonates, into fine particles, the halide powder obtained by halogenating the Li source, Ti source, and M source also becomes fine particles of the same order, and further, the halide solid electrolyte to be produced can also be obtained in the form of fine particles. Therefore, when producing a finely particulate halide solid electrolyte, the Li source, Ti source, and M source may be pulverized into fine particles. Note that the Li source, Ti source, and M source may be pulverized, for example, so that the average particle size becomes 1 μm or less.

[0052] Li, Ti, and M sources, which are simple oxides and / or simple carbonates, generally have superior atmospheric stability compared to halide raw materials (e.g., LiF, TiF, and AlF), and can be handled in a normal atmospheric environment. This allows for reduced process variations in the raw materials during production. Here, "raw material process variations" refers to variations in the state of the raw materials caused by fluctuations in the external environment, such as temperature and humidity, during each process of production (e.g., seasonal variations). Because process variations are reduced for the Li, Ti, and M sources, which are simple oxides and / or simple carbonates, grinding using a ball mill or a media-agitating mill can be performed stably and easily, unlike soft halide raw materials. Therefore, by pre-grinding the Li, Ti, and M sources into fine particles, the halide solid electrolyte to be produced can be finely divided, enabling the production of thin layers using the solid electrolyte. Furthermore, since the material, the simple halide of Ti, and the simple halide of M are fine particles, reaction irregularities are reduced in the solid-phase reaction in the synthesis step (B) above, and a more homogeneous solid electrolyte is synthesized than in the conventional case where halide raw materials are used as starting materials.

[0053] <Regarding (A-1)> (A-1-1) In (A-1), after the above (A-0), a halogenation treatment is performed on each of the Li source, Ti source, and M source to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M. At this time, for example, the Li source and a first halogen-containing material are mixed, the Ti source and a second halogen-containing material are mixed, and the M source and a third halogen-containing material are mixed. The first halogen-containing material, the second halogen-containing material, and the third halogen-containing material are used for the same purpose as the above-mentioned "halogen-containing material." Therefore, the first halogen-containing material, the second halogen-containing material, and the third halogen-containing material can be the same material as the "halogen-containing material." The first halogen-containing material, the second halogen-containing material, and the third halogen-containing material may be the same material as each other, or different materials from each other.

[0054] In this way, by uniformly mixing the Li source and the first halogen-containing compound, the Ti source and the second halogen-containing compound, and the M source and the third halogen-containing compound as a preliminary step prior to the halogenation treatment, the Li source, the Ti source, and the M source can be uniformly converted into halides. This allows homogeneous simple halides of Li, Ti, and M to be obtained, and as a result, the final halide solid electrolyte can be synthesized uniformly.

[0055] For example, powders of the Li source and the first halogen-containing substance are mixed in a desired ratio. For example, dry mixing may be used as long as the powders of the Li source and the first halogen-containing substance are uniform. For example, the powders may be mixed uniformly by repeatedly mixing with a spatula, or by using a dry mixing device such as a mortar and pestle, a mortar and pestle, or a V-blender. Mixing may also be performed using a medium such as zirconia balls. Any mixing method may be used as long as it can uniformly mix these powders. The uniformity can be evaluated using, for example, energy dispersive X-ray spectroscopy (EDS) or an electron probe microanalyzer (EPMA). For example, the uniformity can be confirmed by observing a composition mapping image. Powders of the Ti source and the second halogen-containing substance, and powders of the M source and the third halogen-containing substance can also be mixed in a similar manner.

[0056] (A-1-2) In (A-1-2), the first mixture containing the Li source and the first halogen-containing substance, the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance obtained in (A-1-1) above are each heat-treated, thereby subjecting the Li source, the Ti source, and the M source to a halogenation treatment.

[0057] A general electric furnace may be used for the heat treatment. The atmosphere for the heat treatment may be selected as necessary, and the heat treatment may be performed in air, an inert gas atmosphere (e.g., nitrogen gas or argon gas), or a reducing gas (e.g., hydrogen or carbon dioxide). The synthesized halide is usually obtained as a powder.

[0058] <Regarding (B)> In the above (B), a halogenated solid electrolyte is synthesized using the simple halide of Li, the simple halide of Ti, and the simple halide of M obtained in the above (A).

[0059] The above (B) may include, for example, (B-1) mixing the simple halide of Li, the simple halide of Ti, and the simple halide of M obtained in the above (A), and (B-2) synthesizing a halide solid electrolyte by causing a solid-state reaction between the simple halide of Li, the simple halide of Ti, and the simple halide of M.

[0060] (B-1) Mixing a simple halide of Li (e.g., LiF), a simple halide of Ti (e.g., TiF2O), and a simple halide of M (e.g., AlF3) is a process of mixing them uniformly so as to achieve the composition ratio of the halide solid electrolyte to be manufactured. In this way, by uniformly mixing the simple halide of Li, the simple halide of Ti, and the simple halide of M obtained in (A) above, a uniform mixed powder can be obtained. By subjecting this uniformly mixed mixed powder to a solid-state reaction in (B-2) described below, a homogeneous halide solid electrolyte can be synthesized.

[0061] The powders of the Li simple halide, Ti simple halide, and M simple halide may have any shape, and may, for example, have an average particle size of 0.1 μm or more and 10 μm or less. The average particle sizes of the Li simple halide, Ti simple halide, and M simple halide are not limited to this range, and powders of any average particle size and any shape may be used from the viewpoint of handling in the mixing step and control of the solid-state reaction. The smaller the average particle size, the lower the temperature of the solid-state reaction.

[0062] The powders of Li simple halide, Ti simple halide, and M simple halide may be mixed by a general dry mixing or a general wet mixing method, as long as they are mixed uniformly. For example, the mixture of Li simple halide, Ti simple halide, and M simple halide powders may be mixed repeatedly with a spatula to homogenize them, or may be mixed using a mortar and pestle, or may be mixed using a dry mixer such as a mortar or V-blender. Mixing may also be performed using a medium such as zirconia balls. Any method may be used as long as the powders of Li simple halide, Ti simple halide, and M simple halide can be mixed uniformly. The homogeneity can be evaluated using, for example, EDS or EPMA. For example, the homogeneity can be confirmed by observing a composition mapping image.

[0063] (B-2) A halide solid electrolyte is synthesized by a solid-state reaction of a simple halide of Li, a simple halide of Ti, and a simple halide of M. For example, by heat-treating a mixture containing a simple halide of Li, a simple halide of Ti, and a simple halide of M, the simple halide of Li, a simple halide of Ti, and a simple halide of M can be caused to undergo a solid-state reaction.

[0064] A general electric furnace may be used for the heat treatment for the solid-state reaction. The heat treatment atmosphere may be selected as needed, and the heat treatment may be performed in air, an inert gas atmosphere (e.g., nitrogen gas or argon gas), or a reducing gas (e.g., hydrogen or carbon dioxide). The synthesized halide solid electrolyte is usually obtained as a powder, but when heat treated at or above the melting point, it may be obtained as a molten body, a sintered body, or a block-shaped mass in which the powder has solidified.

[0065] In the heat treatment, the homogeneously mixed mixture is placed in a heat-resistant alumina container (sheath), and the mixture is fired in a furnace under any atmosphere. For example, an inert gas such as nitrogen gas is flowed into the furnace, and gases generated during halogenation (e.g., ammonium, hydrogen chloride, carbon dioxide, etc.) are discharged. The heat treatment is carried out in the furnace at a temperature of, for example, 150°C to 600°C for, for example, 1 hour to 40 hours, to cause a solid-state reaction between the simple halides of Li, Ti, and M. By introducing and discharging gas into the furnace in this way, unnecessary reaction gas components are prevented from remaining in the furnace, i.e., in the halide solid electrolyte.

[0066] When introducing the inert gas into the furnace, it is recommended to avoid direct contact of the inert gas with the sheath containing the mixture. Instead of inert gas, air may be introduced into the furnace. A plate larger than the gas inlet is installed between the gas inlet and the sheath. The plate's thickness is sufficient as long as it is not damaged by the gas flow or handling. For example, partial shielding, such as by placing a plate such as an alumina plate against the sheath, is preferable. By shielding the space between the gas inlet and the sheath in this way, the gas flows around the shielding plate before contacting the sheath. By bypassing the gas and indirectly contacting the sheath in this way, the temperature is lower in the area directly exposed to the gas, thereby reducing the problem of large temperature distribution within the sheath. This suppresses uneven distribution of the progress (i.e., variation in progress) in the solid-state reactions of the Li simple halide, Ti simple halide, and M simple halide.

[0067] It is advisable to install the gas inlet on the bottom side of the furnace and the exhaust port on the top side (for example, on the ceiling or above the side wall). This allows the reaction gas to be smoothly discharged outside the furnace along with the convection current (bottom to top) inside the furnace, reducing the contamination of unnecessary residual components with the halide solid electrolyte.

[0068] The gas to be introduced may be heated before being introduced into the furnace. This prevents the temperature distribution in the sheath from becoming uneven. This allows the reaction for the halogenation treatment to proceed uniformly, resulting in a more homogeneous halide solid electrolyte.

[0069] The heat treatment temperature for the solid-phase reaction is, for example, 150°C or higher, and as described above, for example, 150°C or higher and 600°C or lower, or may be 150°C or higher and 550°C or lower, or 250°C or higher and 550°C or lower. Although it depends on the input amounts of the Li simple halide, Ti simple halide, and M simple halide, a temperature of 250°C or higher and 450°C or lower, and 2 hours or higher and 20 hours or lower are particularly suitable. The temperature, time, and reaction gas discharge time required for synthesis of the halide solid electrolyte may be determined arbitrarily in consideration of the properties and powder properties of the Li simple halide, Ti simple halide, and M simple halide.

[0070] The furnace used for the heat treatment can be a known firing furnace (e.g., an electric furnace) or an atmospheric firing furnace. Note that in order to remove the air and moisture between the particles deep inside the sheath and completely replace it with an inert gas, the inert gas may be flowed after vacuum replacement. This reduces the effects of reactive components and moisture contained in the air. The vacuum replacement may be repeated.

[0071] The temperature distribution within the sheath during the heat treatment may be within the temperature distribution range of a commonly used firing furnace, for example, 30° C. The temperature distribution within the sheath referred to here is the difference between the maximum and minimum temperatures within the sheath.

[0072] Since Ti simple halides contain oxygen and halogens, such as TiF2O, heat treatment is not necessary if the Ti simple halides do not contain easily volatile materials such as titanium halides (e.g., TiF4), or if present in negligible amounts. A mixture containing Li simple halides, Ti simple halides, and M simple halides may be placed in a sheath and, if necessary, heat-treated with a lid (e.g., an alumina lid) to prevent dust and foreign matter from falling. Therefore, unlike heat treatments in conventional manufacturing methods using halide raw materials (i.e., heat treatments for solid-state reactions of halide raw materials) that are limited in throughput by the size of sealed heat treatment jigs, the heat treatment in the manufacturing method according to the first embodiment offers excellent productivity and operability, making it highly valuable for industrial applications. The manufacturing method according to the first embodiment, with its excellent productivity, can produce a halide solid electrolyte with excellent ionic conductivity and stability (e.g., electrochemical stability and heat resistance). In addition, when a trace amount of titanium halide (e.g., TiF) is contained, the trace amount of titanium halide evaporates and disappears when the heat treatment is performed in an open atmosphere. Therefore, even in such a case, a halide solid electrolyte having excellent characteristics and reliability can be obtained.

[0073] The sheath material does not have to be alumina. Heat-resistant containers made of various dense materials (e.g., relative density of 98% or more), such as mullite or SiC, can be used for the sheath, in addition to alumina. A suitable material for the sheath may be selected in consideration of the reaction between the oxide mixture, halogen-containing material, and halide solid electrolyte contained in the sheath and the sheath. In addition to the above-mentioned sheath materials, materials that are dense, heat-resistant, and have a small heat capacity can also be used for the sheath. Various shapes, such as cylindrical, prismatic, and gourd-shaped, can be used for the sheath.

[0074] Although the heat treatment using a sagger has been described here as an example, the present invention is not limited to this. For example, a rotary furnace such as a rotary kiln may be used, or the heat treatment may be performed by spraying the mixed powder as in spray drying.

[0075] As an example of the production method according to the first embodiment, the method of carrying out the above (A-0), (A-1-1), and (A-1-2) has been described in detail. However, the step of pulverizing at least one selected from the group consisting of the Li source, the Ti source, and the M source may not necessarily be carried out. Furthermore, uniformly mixing the Li source and the first halogen-containing substance to obtain a first mixture, uniformly mixing the Ti source and the second halogen-containing substance to obtain a second mixture, and uniformly mixing the M source and the third halogen-containing substance to obtain a third mixture may not necessarily be carried out. For example, a halogen-containing substance may be added to a starting material such as a Li source, and heat treatment may be performed without sufficient mixing. Furthermore, while heat treatment is desirable for efficient halogenation, halogenation of the starting material such as a Li source may also be carried out by, for example, adding a halogen-containing substance to the starting material such as a Li source and then leaving it at room temperature for a long period of time.

[0076] In the production method according to the first embodiment, for example, an additive for promoting the halogenation reaction of the Li source, Ti source, and M source may be added to the starting materials, i.e., the Li source, Ti source, and M source. Also, an additive for promoting the solid-state reaction of the Li simple halide, Ti simple halide, and M simple halide may be added to a mixture containing the Li simple halide, Ti simple halide, and M simple halide. Examples of such additives include oxides containing at least one element selected from the group consisting of P, S, Nb, Ga, Zn, Mg, K, Na, Ca, Fe, Si, and Cu.

[0077] For example, when trace amounts of P and S are added during the solid-state reaction of a simple halide of Li, a simple halide of Ti, and a simple halide of M, the temperature of the solid-state reaction can be lowered by, for example, about 10 to 30°C. This can accelerate the solid-state reaction of the simple halide of Li, a simple halide of Ti, and a simple halide of M. P oxide (e.g., PO) may be added as the P component. The P component and the S component may be added together, or only one of them may be added. The amount of the additive added is not particularly limited and can be selected appropriately depending on the compound to be added and its purpose. For example, when the P component and the S component are added for the purpose of accelerating the solid-state reaction, the total amount of the P component and the S component may be, for example, 0.001 mol% or more and 0.3 mol% or less of the total amount of the simple halide of Li, a simple halide of Ti, and a simple halide of M.

[0078] The additives added as the P component and the S component may be, for example, particulate. The effect of the additive may vary depending on the particle form and dispersion state of the additive, but generally, the smaller the particle size of the additive, the greater the reaction-accelerating effect and other effects it can achieve. For example, the particle size of the additive may be smaller than the particles of the additive (e.g., Li source, Ti source, M source, simple halide of Li, simple halide of Ti, simple halide of M, etc.). As an example, the additive may have a particle size of 0.1 μm or less and a BET of 100 μm or less. 2 / g or more. Note that if coarse particles of the P and S component additives are used or if they are added in excess, an extra precipitated phase other than the solid electrolyte may be generated, which may reduce ionic conductivity. Therefore, it is desirable to adjust the particle size and the amount of additive to an appropriate level. For example, it is desirable that the P and S component additives have a particle size and amount such that P and S are not detected as a composition phase in X-ray diffraction measurement of the finally obtained halide solid electrolyte. This allows the synthesis of a halide solid electrolyte with high ionic conductivity while achieving a reaction-accelerating effect.

[0079] The halide solid electrolyte obtained by the manufacturing method according to the first embodiment is a halide solid electrolyte containing Li, Ti, M, and X. The obtained halide solid electrolyte may contain, for example, a first crystalline phase represented by the following composition formula (1) and a second crystalline phase represented by the following composition formula (2). Composition formula (1): Li2TiX6 Composition formula (2): Li3MX6

[0080] A halide solid electrolyte containing the first and second crystalline phases can have excellent ionic conductivity. Furthermore, by changing the ratio of the components of the composition formula (1) and the composition formula (2), a halide solid electrolyte can be produced with controlled properties such as density, strength, and electrical properties.

[0081] Furthermore, the halide solid electrolyte obtained by the manufacturing method according to the first embodiment may be particulate, and each particle of the halide solid electrolyte may contain a first crystalline phase represented by the composition formula (1) and a second crystalline phase represented by the composition formula (2). According to this configuration, a single particle contains a first crystalline phase of Li2TiX6 and a second crystalline phase of Li3MX6. Therefore, a halide solid electrolyte in which the first and second crystalline phases are homogenized is realized. This allows the first and second crystalline phases to be uniformly dispersed when forming a compact using the halide solid electrolyte or dispersing the halide solid electrolyte for slurry production, thereby producing a solid electrolyte layer with high ionic conductivity and excellent stability. The particle size and shape can be selected depending on the application. Such composite particles containing two crystalline phases are formed, for example, by bonding during a solid-state reaction. Therefore, the composite particles can be miniaturized by methods such as microparticulating the oxide raw material.

[0082] When the halide solid electrolyte obtained by the manufacturing method according to the first embodiment includes a first crystal phase and a second crystal phase, the halide solid electrolyte can be represented by the following composition formula (3): Composition formula (3): xLi2TiX6-(1-x)Li3MX6. In composition formula (3), x satisfies 0<x<1. That is, x represents the composition ratio of Li2TiX6, which is the first crystal phase, and (1-x) represents the composition ratio of Li3MX6, which is the second crystal phase. To improve ionic conductivity, x may, for example, satisfy 0.05≦x≦0.5.

[0083] In the manufacturing method according to the first embodiment, when at least one selected from the group consisting of a P component additive and an S component additive is used as the additive, the resulting halide solid electrolyte contains at least one selected from the group consisting of P and S. That is, in this case, when M is Al and X is F, the halide solid electrolyte obtained by the manufacturing method according to the first embodiment contains Li, Ti, Al, and F, and further contains at least one selected from the group consisting of P and S. This configuration allows for the production of a homogeneous halide solid electrolyte with excellent ionic conductivity. The halide solid electrolyte obtained by the manufacturing method according to the first embodiment may consist essentially of Li, Ti, Al, F, P, and S, or may consist only of Li, Ti, Al, F, P, and S. The phrase "the halide solid electrolyte consists essentially of Li, Ti, Al, F, P, and S" means that the ratio of the total amount of substance of Li, Ti, Al, F, P, and S to the total amount of substance of all elements constituting the halide solid electrolyte is 90% or more. As an example, this ratio may be 95% or more. Note that the above-mentioned halide solid electrolyte containing Li, Ti, Al, and F and further containing at least one element selected from the group consisting of P and S may contain, for example, a first crystalline phase represented by the following composition formula (4) and a second crystalline phase represented by the following composition formula (5). Composition formula (4): Li2TiX6 Composition formula (5): Li3AlX6

[0084] The amount of oxygen as an impurity in the halide solid electrolyte obtained by the manufacturing method according to the first embodiment may be 0.5 mass% or less. The manufacturing method according to the first embodiment makes it possible to obtain a halide solid electrolyte with little oxygen contamination. The amount of oxygen as an impurity in the halide solid electrolyte may be, for example, 0.1 mass% or more.

[0085] As described above, when P and S components are added, P and S may not be detected as a composition phase in X-ray diffraction measurement. Even in this case, the presence of P and S in the halide solid electrolyte can be confirmed by highly sensitive composition analysis (area analysis, etc.) such as an electron probe microanalyzer (EPMA). The total content of P and S contained in the halide solid electrolyte may be, for example, 0.0003 at. % or more and 0.15 at. % or less. The content of P and S can be determined by EPMA or the like.

[0086] When the halide solid electrolyte obtained by the production method according to the first embodiment includes the first crystalline phase and the second crystalline phase, and further includes at least one element selected from the group consisting of P and S derived from the additive, for example, P and S may be incorporated into both the first crystalline phase (i.e., LiTiX) and the second crystalline phase (i.e., LiMX).

[0087] The halide solid electrolyte obtained by the manufacturing method according to the first embodiment preferably contains substantially no TiF. This configuration suppresses changes over time in the characteristics and mechanical properties of the halide solid electrolyte due to TiF evaporation and deliquescence, thereby achieving a halide solid electrolyte with excellent characteristics and reliability. Here, "the halide solid electrolyte contains substantially no TiF" means that the TiF content in the solid electrolyte is, for example, 0.5 mass% or less, preferably 0.1 mass% or less. The TiF content in the halide solid electrolyte can be determined, for example, by elemental analysis using energy dispersive X-ray spectroscopy (EDS) or electron probe microanalysis (EPMA) on the cross section of a compacted halide solid electrolyte powder or the particle surface of the solid electrolyte, and the TiF content can be determined from the area ratio of the detected TiF portion. If the oxide mixture used as the raw material for the halide solid electrolyte contains trace amounts of titanium oxide (TiO), trace amounts of TiF may be generated during the halogenation process. However, even in this case, the halogenation treatment is performed in the open state, so that TiF can be evaporated and eliminated, thereby making it possible to obtain a halide solid electrolyte that is substantially free of TiF and has excellent properties and reliability.

[0088] The halide solid electrolyte obtained by the manufacturing method according to the first embodiment preferably satisfies at least one of the following (1), (2), and (3) in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the halide solid electrolyte using, for example, Cu-Kα radiation: (1) No peak derived from TiF4 is present; (2) No peak derived from LiF is present; and (3) No peak derived from AlF3 is present.

[0089] With the above-described configuration, the halide solid electrolyte obtained by the manufacturing method according to the first embodiment does not substantially contain compounds of, for example, TiF4, LiF, and / or AlF3, and therefore has excellent characteristics and reliability.

[0090] In this specification, a peak in an X-ray diffraction pattern is defined as a mountain-shaped portion having an S / N ratio (i.e., the ratio of signal S to background noise N) of 1.3 or more and a half-width of 5° or less. Therefore, the absence of a peak means that no mountain-shaped portion recognized as a peak as described above is confirmed.

[0091] For example, when the halide solid electrolyte obtained by the production method according to the first embodiment satisfies the above-mentioned configuration (1), i.e., when no peak derived from TiF is present in the X-ray diffraction pattern, no peak is present within a diffraction angle 2θ range of, for example, 24° or more and 25° or less.

[0092] The halogenated solid electrolyte obtained by the manufacturing method according to the first embodiment can achieve high ionic conductivity comparable to that of a solid electrolyte manufactured using a halide as a starting material.

[0093] The halide solid electrolyte obtained by the manufacturing method according to the first embodiment may be particulate. The halide solid electrolyte has relatively soft properties. Therefore, this configuration allows for a relatively soft particulate solid electrolyte to be realized. Therefore, a compact of such a halide solid electrolyte has high ionic conductivity, excellent stability, and can have any shape. Therefore, a compact of a halide solid electrolyte having such properties can realize a solid electrolyte layer of a battery having excellent properties and high reliability. The size and shape of the halide solid electrolyte particles can be selected appropriately depending on the application.

[0094] When the manufacturing method according to the first embodiment is compared with the manufacturing methods described in Patent Documents 1 and 2, there are the following differences.

[0095] Patent Document 1 discloses a halide-based solid electrolyte containing Li, Ti, M, and F. The "M" in the solid electrolyte described in Patent Document 1 is at least one selected from the group consisting of Al and Y. All starting materials used in producing this solid electrolyte are fluorides. A planetary ball mill and zirconia balls are used to apply a strong crushing force (impact force) to the starting materials, resulting in a mechanochemical reaction to synthesize the halide solid electrolyte. In contrast, the method for producing a halide solid electrolyte according to the first embodiment converts simple oxides and / or simple carbonates into simple halides, which are then subjected to a solid-state reaction (e.g., LiF, AlF, TiF, etc.). This method suppresses instabilities such as raw material evaporation, and by achieving homogeneous synthesis at the microstructure level, reaction irregularities are reduced and precipitates are suppressed. Thus, the production method according to the first embodiment is a novel method for synthesizing a halide solid electrolyte with excellent properties and reliability. Therefore, the production method according to the first embodiment differs from the production method described in Patent Document 1 in many respects in terms of the starting materials and reaction mechanism.

[0096] Patent Document 2 discloses a method for producing a halide solid electrolyte containing Li, Ti, M1, and F as part of the positive electrode material. Note that "M1" in the solid electrolyte described in Patent Document 2 is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. However, like the production method described in Patent Document 1, a fluoride is used as the starting material. Therefore, the production method according to the first embodiment differs in many respects from the production method described in Patent Document 2, as well as from the production method described in Patent Document 1, in terms of the starting materials and reaction mechanism.

[0097] As described above, in the manufacturing method according to the first embodiment, stable simple oxides and / or simple carbonates are used as starting materials, which are halogenated to obtain simple halides, and the simple halides are used to synthesize a homogeneous electrolyte while suppressing the formation of unnecessary precipitated phases. Therefore, according to the manufacturing method according to the first embodiment, a halide solid electrolyte having excellent ionic conductivity can be synthesized at low cost. Patent Documents 1 and 2 do not disclose the manufacturing method and halide solid electrolyte of the first embodiment.

[0098] Second Embodiment A method for producing a halide solid electrolyte according to a second embodiment will now be described.

[0099] The production method according to the second embodiment further includes, after the step (B) in the production method according to the first embodiment, (C) subjecting the halide solid electrolyte obtained in the step (B) to a pulverization treatment.

[0100] According to the manufacturing method of the second embodiment, by carrying out the pulverization treatment (C) above, a halide solid electrolyte having excellent ionic conductivity and reliability can be obtained with a particle size suitable for the application. Furthermore, since at least a portion of the halide solid electrolyte can be made amorphous, the ionic conductivity can be improved and the softness of the halide solid electrolyte particles can be improved. By improving the softness of the halide solid electrolyte particles, the density of a compact of the halide solid electrolyte can be improved. Therefore, the halide solid electrolyte obtained by the manufacturing method of the second embodiment can form a dense compact with high ionic conductivity.

[0101] 2 is a flowchart showing an example of a method for producing a halide solid electrolyte according to the second embodiment. Here, as the (A) described in the first embodiment, (A-0), (A-1-1), and (A-1-2) are performed, followed by (B). The second embodiment describes an example of a production method in which (C) is then performed.

[0102] As shown in FIG. 2 , first, at least one selected from the group consisting of a Li source, a Ti source, and an M source is pulverized. In this example, for example, all of the Li source, the Ti source, and the M source are pulverized (S21). Next, the Li source and a first halogen-containing substance are mixed, the Ti source and a second halogen-containing substance are mixed, and the M source and a third halogen-containing substance are mixed (S22). Next, the resulting first mixture containing the Li source and the first halogen-containing substance, the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance are each heat-treated, thereby halogenating the Li source, the Ti source, and the M source (S23). Next, a halide solid electrolyte is synthesized using the resulting simple halide of Li, the simple halide of Ti, and the simple halide of M (S24). Next, as a step corresponding to the above (C), the halide solid electrolyte obtained in S24 is subjected to a pulverization treatment (S25).

[0103] S21 to S24 are the same as S11 to S14 described in the first embodiment, respectively, and therefore detailed description thereof will be omitted here.

[0104] The halide solid electrolyte synthesized by the above (B) has an average particle size of, for example, about 3 μm or more and 20 μm or less. In the above (C), the halide solid electrolyte synthesized by the above (B) is pulverized to an average particle size of, for example, about 0.1 μm or more and 3 μm or less.

[0105] The pulverization process may be a dry process or a wet process using water or a solvent (e.g., ethanol, butyl acetate, etc.) as long as it can pulverize the halide solid electrolyte to a desired particle size. For example, zirconia balls (e.g., balls with a diameter of 1 mm to 30 mm) and the halide solid electrolyte obtained in (B) above are placed in a ball mill container, and pulverization is performed for, for example, about 3 to 40 hours. The ball mill container may be, for example, a polyethylene container, a container lined with fluororesin or zirconia, or the like.

[0106] The grinding treatment in (B) above may include, for example, mechanochemical treatment. The mechanochemical treatment here is carried out to introduce distorted crystallinity or amorphousness into the crystals of the halide solid electrolyte. The distorted crystallinity or amorphousness is mainly introduced into the surface layer of the halide solid electrolyte particles. The specific means may be the same as those used in the grinding treatment described above, such as using a ball mill. However, the grinding conditions may be strengthened or the grinding time may be extended. The equipment and media used for the mechanochemical treatment may be the same as those used in the grinding treatment. Generally, grinding and mechanochemical treatment proceed simultaneously. As an example, in the case of a dry method, a ball mill container lined with zirconia is used, and zirconia balls are placed in a volume ratio of 10% to 60%. The diameter of the zirconia balls is not particularly limited, and any size may be used. As mentioned above, commercially available balls with a diameter of 1 mm to 30 mm are typically used, but balls with a smaller or larger diameter may also be used. The diameter of the balls used may be selected as desired depending on the desired particle size or degree of amorphization. Furthermore, to prevent the halide solid electrolyte from adhering to the zirconia balls or the inner wall of the zirconia container, an appropriate amount of an additive, such as ethanol, that does not adversely affect the properties of the halide solid electrolyte may be added. It is preferable that the additive be able to be removed by drying later.

[0107] The introduction of amorphousness into the halide solid electrolyte can be confirmed by the X-ray diffraction pattern obtained by X-ray diffraction measurement. The X-ray diffraction pattern can be measured by the θ-2θ method using Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) as the X-ray source. Specifically, this can be confirmed by the fact that the peaks in the X-ray diffraction pattern of the halide solid electrolyte after the pulverization treatment are broadened compared to the peaks in the X-ray diffraction pattern of the halide solid electrolyte before the pulverization treatment. The broadened peaks mean that the peaks are broadened and the half-width is widened.

[0108] The introduction of distorted crystals into the halide solid electrolyte, i.e., the presence of regions with disordered crystallinity, can be observed with a transmission electron microscope (TEM) as an image consisting of regions with high order in the lattice image and regions with disordered lattice images.

[0109] Furthermore, the change in deformability (i.e., softness) due to amorphization can be evaluated by an evaluation method such as micro-Vickers.

[0110] As described above, since the manufacturing method according to the second embodiment includes a pulverization process, the halide solid electrolyte obtained by the manufacturing method according to the second embodiment includes, for example, an amorphous portion. With this configuration, the amorphous portion of the halide solid electrolyte becomes even softer and more deformable. Therefore, a compact of the halide solid electrolyte can be configured into a solid electrolyte layer of any shape with higher ionic conductivity and higher stability. Therefore, a compact of the halide solid electrolyte including an amorphous portion can realize a solid electrolyte layer of a battery with excellent characteristics and high reliability.

[0111] The amorphous material may be contained in, for example, the surface layer of a halide solid electrolyte particle, and may have a higher ionic conductivity than the interior of the particle. This configuration allows the surface layer of the halide solid electrolyte particle to have high ionic conductivity (e.g., 1 μS / cm or more). This increases the adhesion and ionic conductivity between the halide solid electrolyte particles, resulting in a solid electrolyte layer of a battery with excellent performance and high reliability.

[0112] The amorphous material may be contained in, for example, the surface layer of a halide solid electrolyte particle, and may have lower electronic conductivity than the interior of the particle. This configuration allows the surface layer of the halide solid electrolyte particle to have low electronic conductivity (e.g., 0.1 μS / cm or less). This reduces loss due to electronic conduction and increases ionic conductivity, resulting in a solid electrolyte layer for a battery with excellent performance and high reliability.

[0113] As a modification of the manufacturing method according to the second embodiment, the halide solid electrolyte may be made into a slurry for forming a coating film simultaneously with the pulverization treatment in (C) above.

[0114] 3 is a flowchart showing a modified example of the method for producing a halide solid electrolyte according to the second embodiment. Regarding the modified example of the production method according to the second embodiment, the steps (A-0), (A-1-1), and (A-1-2) are carried out as the step (A), which is an example of the production method described in the first embodiment, and then the step (B) is carried out. The production method according to the second embodiment further describes an example of a production method in which the step (C) is carried out thereafter.

[0115] As shown in FIG. 3 , first, at least one selected from the group consisting of a Li source, a Ti source, and an M source is pulverized. In this example, for example, all of the Li source, the Ti source, and the M source are pulverized (S31). Next, the Li source and a first halogen-containing substance are mixed, the Ti source and a second halogen-containing substance are mixed, and the M source and a third halogen-containing substance are mixed (S32). Next, the resulting first mixture containing the Li source and the first halogen-containing substance, the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance are each heat-treated, thereby halogenating the Li source, the Ti source, and the M source (S33). Next, a halide solid electrolyte is synthesized using the resulting simple halide of Li, the simple halide of Ti, and the simple halide of M (S34). Next, as a step corresponding to the above (C), the halide solid electrolyte obtained in S34 is subjected to a pulverization treatment and a slurry treatment (S35).

[0116] S31 to S34 are the same as S11 to S14 described in the first embodiment, respectively, and therefore detailed description thereof will be omitted here.

[0117] The pulverization process in S35 is the same as the pulverization process in S25 described as an example of the manufacturing method of the second embodiment. In a modified example of the manufacturing method of the second embodiment, a slurrying process is further performed. The slurrying process is performed, for example, by adding an organic binder, a plasticizer, etc., dispersed in an organic solvent such as tetralin to the halide solid electrolyte simultaneously with the pulverization process. An example of the organic binder is styrene butadiene block copolymer (SBS). An example of the plasticizer is bisbutyl phthalate (DBP) and butyl benzyl phthalate (BBP).

[0118] The obtained halide solid electrolyte slurry can be used for printing or coating. The thickness of the coating film may be, for example, 10 μm or more and 100 μm or less, thereby allowing, for example, a halide solid electrolyte slurry that has been pulverized to include an amorphous portion to be directly coated. In this way, an organic binder, a plasticizer, etc. may be added in the pulverization process to prepare a halide solid electrolyte slurry, and the slurry may be used to form a coating film. This allows for the formation of a halide solid electrolyte coating film with excellent properties. Such a coating film can be used, for example, in the manufacture of a coated cell.

[0119] Third Embodiment A method for producing a halide solid electrolyte according to a third embodiment will now be described.

[0120] In the production method according to the third embodiment, in the above (A) described in the first embodiment, a halogen-containing material is heat-treated to generate halogen gas, and the halogen gas is brought into contact with the Li source, Ti source, and M source, thereby subjecting the Li source, Ti source, and M source to halogenation treatment. In the production method according to the third embodiment, the above (B) may be followed by the pulverization treatment of the above (C) described in the second embodiment.

[0121] FIG. 4 is a flowchart showing an example of a method for producing a halide solid electrolyte according to the third embodiment. As shown in FIG. 4 , first, at least one selected from the group consisting of a Li source, a Ti source, and an M source is pulverized. In this example, for example, all of the Li source, the Ti source, and the M source are pulverized (S41). Next, the Li source, the Ti source, and the M source and a halogen-containing material are placed in predetermined positions, and the halogen-containing material is heat-treated to bring the generated halogen gas into contact with the Li source, the Ti source, and the M source (S42). This results in a halogenation treatment of the Li source, the Ti source, and the M source. Next, a halide solid electrolyte is synthesized using the obtained simple halide of Li, the simple halide of Ti, and the simple halide of M (S43). Thereafter, as a step corresponding to the above (C), the halide solid electrolyte obtained in S43 may be subjected to a pulverization treatment (S44).

[0122] According to the manufacturing method of the third embodiment, the Li source, the Ti source, and the M source can be halogenated by the generated halogen gas without directly contacting them with a halogen-containing material. Therefore, even if a halogen-containing material containing an inorganic component in addition to a halogen element (e.g., a substance such as CuF that is emitted as fluorine gas when heated) is used, it is not necessary to consider inorganic residues in the halide solid electrolyte to be manufactured. This allows for a wider range of usable halogen-containing materials.

[0123] As a specific example, the oxide mixture is placed on a fine-mesh nickel mesh, and a halogen-containing material such as ammonium fluoride is placed below the nickel mesh. In this way, the Li source, Ti source, and M source are placed without contacting each other with the halogen-containing material. In this state, by heat-treating the halogen-containing material, a halogen gas such as fluorine gas is generated, and the gas passes through the nickel mesh and comes into contact with the Li source, Ti source, and M source. As a result, the Li source, Ti source, and M source are each converted into a halide. The Li source, Ti source, and M source, and the halogen-containing material, are as described in the first embodiment. Note that while the heat treatment can be performed in air, it is preferable to perform the heat treatment in a nitrogen or reducing atmosphere to prevent oxidation of the nickel mesh.

[0124] [Fourth Embodiment] A fourth embodiment will be described below. Matters described in the first, second, and third embodiments will be omitted as appropriate.

[0125] The battery according to the fourth 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.

[0126] At least one selected from the group consisting of the positive electrode, the electrolyte layer, and the negative electrode includes a halide solid electrolyte containing Li, Ti, Al, and F, and further containing at least one selected from the group consisting of P and S. The halide solid electrolyte can be produced by, for example, the production method according to the first, second, or third embodiment.

[0127] Hereinafter, the halide solid electrolyte contained in the battery according to the fourth embodiment, which contains Li, Ti, Al, and F and further contains at least one element selected from the group consisting of P and S, will be referred to as the halide solid electrolyte according to the fourth embodiment.

[0128] As described in the first, second, or third embodiments as an example of a halide solid electrolyte that can be produced by the production method of the first, second, or third embodiments, the halide solid electrolyte according to the fourth embodiment may consist essentially of Li, Ti, Al, F, P, and S, or may consist solely of Li, Ti, Al, F, P, and S. Furthermore, as described in the first embodiment, the halide solid electrolyte according to the fourth embodiment may include a first crystalline phase represented by the composition formula (4) above and a second crystalline phase represented by the composition formula (5) above. In this case, for example, P and S may be incorporated into both the first crystalline phase (i.e., LiTiX) and the second crystalline phase (i.e., LiAlX). Furthermore, the halide solid electrolyte according to the fourth embodiment may include an amorphous phase, as described in the second embodiment. The amorphous material may be contained in, for example, a surface layer of a particle of the halide solid electrolyte according to the fourth embodiment and have a higher ionic conductivity than the interior of the particle. Alternatively, the amorphous material may be contained in, for example, a surface layer of a particle of the halide solid electrolyte according to the fourth embodiment and have a lower electronic conductivity than the interior of the particle.

[0129] The battery according to the fourth embodiment has excellent charge / discharge characteristics because it contains the halide solid electrolyte according to the fourth embodiment.

[0130] FIG. 5 shows a cross-sectional view of a battery 1000 according to a fourth embodiment.

[0131] The battery 1000 according to the fourth embodiment includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is provided between the positive electrode 201 and the negative electrode 203.

[0132] The positive electrode 201 may include a positive electrode material including a halide according to the fourth embodiment. The positive electrode 201 includes a positive electrode active material 204 and a solid electrolyte 100.

[0133] The electrolyte layer 202 contains an electrolyte material.

[0134] The negative electrode 203 contains a negative electrode active material 205 and a solid electrolyte 100 .

[0135] The solid electrolyte 100 includes, for example, the halide solid electrolyte according to the fourth embodiment. The solid electrolyte 100 may be particles containing the halide solid electrolyte according to the fourth embodiment as a main component. Particles containing the halide solid electrolyte according to the fourth embodiment as a main component refer to particles in which the component contained in the largest amount by molar ratio is the halide solid electrolyte according to the fourth embodiment. The solid electrolyte 100 may be particles made of the halide solid electrolyte according to the fourth embodiment.

[0136] The positive electrode 201 contains a material capable of absorbing and releasing metal ions (e.g., lithium ions). The material is, for example, a positive electrode active material 204.

[0137] Examples of the positive electrode active material 204 include a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion, a fluorinated polyanion material, a transition metal sulfide, a transition metal oxyfluoride, a transition metal oxysulfide, or a transition metal oxynitride. Examples of the lithium-containing transition metal oxide include Li(Ni,Co,Mn)O, Li(Ni,Co,Al)O, or LiCoO.

[0138] In the present disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0139] The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 may be particles. The positive electrode active material 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median diameter of 0.1 μm or more, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201. This improves the charge / discharge characteristics of the battery 1000. When the positive electrode active material 204 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 improves. This allows the battery 1000 to operate at a high output.

[0140] The positive electrode active material 204 may have a larger median diameter than the solid electrolyte 100. This allows the positive electrode active material 204 and the solid electrolyte 100 to be dispersed well in the positive electrode 201.

[0141] In order to improve the energy density and output of the battery 1000, in the positive electrode 201, the ratio of the volume of the positive electrode active material 204 to the sum of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 may be 0.30 or more and 0.95 or less.

[0142] A coating layer may be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer may be formed on the surface of the positive electrode active material 204, for example, before mixing with the conductive additive and the binder. Examples of coating materials included in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. When the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material may contain a halide solid electrolyte according to the fourth embodiment to suppress oxidative decomposition of the sulfide solid electrolyte. When the solid electrolyte 100 contains a halide solid electrolyte according to the fourth embodiment, the coating material may contain an oxide solid electrolyte to suppress oxidative decomposition of the solid electrolyte. Lithium niobate, which has excellent stability at high potentials, may be used as the oxide solid electrolyte. By suppressing oxidative decomposition, an increase in overvoltage of the battery 1000 can be suppressed.

[0143] As described above, when the positive electrode 201 includes the positive electrode material containing the halide according to the fourth embodiment, the positive electrode material may include the halide solid electrolyte according to the fourth embodiment as the solid electrolyte 100, or may include the halide solid electrolyte according to the fourth embodiment as a coating material that coats the positive electrode active material 204.

[0144] To improve the energy density and output of the battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0145] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte. The solid electrolyte may include the halide solid electrolyte according to the fourth embodiment. The electrolyte layer 202 may be a solid electrolyte layer.

[0146] The electrolyte layer 202 may contain 50 mass % or more of the halide solid electrolyte according to the fourth embodiment. The electrolyte layer 202 may contain 70 mass % or more of the halide solid electrolyte according to the fourth embodiment. The electrolyte layer 202 may contain 90 mass % or more of the halide solid electrolyte according to the fourth embodiment. The electrolyte layer 202 may be made of only the halide solid electrolyte according to the fourth embodiment.

[0147] Hereinafter, the halide solid electrolyte according to the fourth embodiment will be referred to as a first solid electrolyte, and a solid electrolyte different from the first solid electrolyte will be referred to as a second solid electrolyte.

[0148] The electrolyte layer 202 may contain not only the first solid electrolyte but also the second solid electrolyte. The first solid electrolyte and the second solid electrolyte may be uniformly dispersed in the electrolyte layer 202. A layer made of the first solid electrolyte and a layer made of the second solid electrolyte may be stacked along the stacking direction of the battery 1000.

[0149] The battery according to the fourth embodiment may include a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203, in this order. The solid electrolyte contained in the first electrolyte layer may have a lower reduction potential than the solid electrolyte contained in the second electrolyte layer. This allows the solid electrolyte contained in the second electrolyte layer to be used without being reduced. As a result, the charge / discharge efficiency of the battery 1000 can be improved. For example, when the second electrolyte layer contains the first solid electrolyte, the first electrolyte layer may contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte. This allows the charge / discharge efficiency of the battery 1000 to be improved. The second electrolyte layer may contain the first solid electrolyte. The first solid electrolyte has high oxidation resistance, thereby achieving a battery with excellent charge / discharge characteristics.

[0150] The electrolyte layer 202 may consist of only the second solid electrolyte.

[0151] The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the cathode 201 and the anode 203 are less likely to short-circuit. When the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high power.

[0152] Examples of the second solid electrolyte are LiMgX, LiFeX, Li(Al,Ga,In)X, Li(Al,Ga,In)X, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0153] To improve the energy density and power output of the battery 1000, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0154] The negative electrode 203 contains a material capable of absorbing and releasing metal ions (e.g., lithium ions). The material is, for example, a negative electrode active material 205.

[0155] Examples of the negative electrode active material 205 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.

[0156] The anode active material 205 may be selected taking into consideration the reduction resistance of the solid electrolyte contained in the anode 203. For example, when the anode 203 contains a first solid electrolyte, the anode active material 205 may be a material capable of absorbing and releasing lithium ions at 0.27 V or more relative to lithium. Examples of such anode active materials include titanium oxide, indium metal, or a lithium alloy. An example of titanium oxide is Li4Ti5O 1 2 , LiTiO, or TiO. By using the above-mentioned negative electrode active material, it is possible to suppress the reductive decomposition of the first solid electrolyte contained in the negative electrode 203. As a result, it is possible to improve the charge / discharge efficiency of the battery 1000.

[0157] The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 may be particles. The negative electrode active material 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median diameter of 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. This improves the charge / discharge characteristics of the battery 1000. When the negative electrode active material 205 has a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 improves. This allows the battery 1000 to operate at high power.

[0158] The negative electrode active material 205 may have a larger median diameter than the solid electrolyte 100. This allows the negative electrode active material 205 and the solid electrolyte 100 to be dispersed well in the negative electrode 203.

[0159] In order to improve the energy density and output of the battery 1000, in the negative electrode 203, the ratio of the volume of the negative electrode active material 205 to the sum of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 may be 0.30 or more and 0.95 or less.

[0160] To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0161] 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 for the purpose of increasing ionic conductivity, chemical stability, and electrochemical stability.

[0162] The second solid electrolyte may be a sulfide solid electrolyte.

[0163] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge0.25 P 0.75 S4, or Li 10 GeP2S 12 is.

[0164] When the electrolyte layer 202 contains the first solid electrolyte, the negative electrode 203 may contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte. The electrochemically stable sulfide solid electrolyte covers the negative electrode active material, thereby preventing the first solid electrolyte from contacting the negative electrode active material. As a result, the internal resistance of the battery 1000 can be reduced.

[0165] The second solid electrolyte may be an oxide solid electrolyte.

[0166] 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; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as LiSiO, LiGeO or elemental substitutions thereof; (iv) LiLaZrO 12 or an element-substituted product thereof; or (v) Li3PO4 or an N-substituted product thereof.

[0167] As mentioned above, the second solid electrolyte may be a halide solid electrolyte.

[0168] Examples of halide solid electrolytes are LiMgX, LiFeX, Li(Al,Ga,In)X, Li(Al,Ga,In)X, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0169] Other examples of halide solid electrolytes include Li a Me b Y cZ6, where a + mb + 3c = 6 and c > 0 are 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. m represents the valence of Me. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements included in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0170] In order to improve 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.

[0171] The halide solid electrolyte may be Li3YCl6 or Li3YBr6.

[0172] The second solid electrolyte may be an organic polymer solid electrolyte.

[0173] An example of the organic polymer solid electrolyte is a compound of a polymer compound and a lithium salt.

[0174] The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, and therefore can further increase ionic conductivity.

[0175] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOF, 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.

[0176] 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 to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0177] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0178] Examples of non-aqueous solvents are cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorine-containing solvents. Examples of cyclic carbonate ester solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of chain carbonate ester solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of chain ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a chain ester solvent is methyl acetate. Examples of fluorine-containing solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or two or more non-aqueous solvents selected from these may be used in combination.

[0179] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), or LiC(SOCF). A single 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 or more and 2 mol / L or less.

[0180] 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.

[0181] Examples of cations contained in the ionic liquid are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammonium such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums; or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums.

[0182] An example of an anion contained in an ionic liquid is PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - is.

[0183] The ionic liquid may contain a lithium salt.

[0184] 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 to improve adhesion between particles.

[0185] 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 can also be used as binders. Examples of such binders include copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures of two or more materials selected from these may also be used as binders.

[0186] At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity.

[0187] Examples of the conductive additive include (i) graphites such as natural graphite or artificial graphite, (ii) carbon blacks such as acetylene black or ketjen black, (iii) conductive fibers such as carbon fiber or metal fiber, (iv) carbon fluoride, (v) metal powders such as aluminum, (vi) conductive whiskers such as zinc oxide or potassium titanate, (vii) conductive metal oxides such as titanium oxide, or (viii) conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene. For cost reduction, the conductive additives (i) or (ii) may be used.

[0188] In addition, a separator impregnated with an electrolyte solution may be used instead of the electrolyte layer, or the exterior housing containing the positive electrode, separator portion, and negative electrode may be filled with the electrolyte solution. The electrolyte solution may be, for example, the nonaqueous electrolyte solution described above. Examples of the shape of the battery according to the fourth embodiment include a coin type, a cylindrical type, a prismatic type, a sheet type, a button type, a flat type, and a laminate type.

[0189] The battery according to the fourth 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.

[0190] [Other Embodiments] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0191] (Technology 1) A method for producing a solid electrolyte containing Li, Ti, M, and X, wherein M is at least one element selected from the group consisting of metal elements (excluding Li and Ti) and metalloid elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I, the method comprising: (A) subjecting at least one Li source selected from the group consisting of simple oxides and simple carbonates of Li, at least one Ti source selected from the group consisting of simple oxides and simple carbonates of Ti, and at least one M source selected from the group consisting of simple oxides and simple carbonates of M to a halogenation treatment to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M, respectively; and (B) synthesizing the halide solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M.

[0192] In the manufacturing method of Technology 1, relatively inexpensive and atmospherically stable materials such as simple oxides and simple carbonates are used as the Li source, Ti source, and M source. Therefore, according to the manufacturing method of Technology 1, a halide solid electrolyte having ionic conductivity comparable to that of a halide solid electrolyte manufactured by a conventional manufacturing method can be synthesized at low cost and in a stable manner. Furthermore, the simple oxides and simple carbonates used as the Li source, Ti source, and M source are generally harder materials than halides. Therefore, in the manufacturing method of Technology 1, unlike when a halide is used as a raw material, the raw material can be easily pulverized and microparticulated. Therefore, by microparticulating the raw material and then performing halogenation treatment and solid electrolyte synthesis, a fine halide solid electrolyte can be easily produced. Thus, the manufacturing method of Technology 1 uses raw materials that are easy to handle for microparticulation, such as pulverization, and is therefore also suitable for producing a fine halide solid electrolyte.

[0193] (Technology 2) The method for producing a halide solid electrolyte according to Technology 1, wherein (A) comprises: (A-0) pulverizing at least one selected from the group consisting of the Li source, the Ti source, and the M source; and (A-1) after (A-0), performing a halogenation treatment on each of the Li source, the Ti source, and the M source to obtain the simple halide of Li, the simple halide of Ti, and the simple halide of M.

[0194] According to the manufacturing method of Technique 2, fine halide solid electrolytes can be manufactured more easily and at lower cost than conventional manufacturing methods that use relatively soft halides as raw materials.

[0195] (Technology 3) The method for producing a halide solid electrolyte according to Technology 1 or 2, wherein the halide solid electrolyte includes a first crystalline phase represented by the following composition formula (1) and a second crystalline phase represented by the following composition formula (2). Composition formula (1): Li2TiX6 Composition formula (2): Li3MX6

[0196] According to the manufacturing method of Technology 3, a halide solid electrolyte having excellent ionic conductivity can be synthesized. By changing the ratio of composition formula (1) and composition formula (2), a halide solid electrolyte having controlled properties such as density, strength, and electrical properties can be manufactured.

[0197] (Technology 4) The method for producing a halide solid electrolyte according to any one of Technologies 1 to 3, wherein M contains Al.

[0198] According to the manufacturing method of Technique 4, a halide solid electrolyte having high ionic conductivity can be obtained.

[0199] (Technology 5) The method for producing a halide solid electrolyte according to any one of Techniques 1 to 4, wherein the X includes F.

[0200] According to the manufacturing method of Technique 5, it is possible to obtain a halide solid electrolyte having excellent stability (particularly excellent electrochemical stability and heat resistance) and high ionic conductivity.

[0201] (Technology 6) The method for producing a halide solid electrolyte according to any one of Techniques 1 to 5, wherein the Li source, the Ti source, and the M source are in a particulate form.

[0202] According to the manufacturing method of Technique 6, halogenation (i.e., substitution of halogen element with oxygen element) proceeds from the particle surface, shortening the reaction distance and increasing the reaction area. This facilitates the halogenation of the raw materials and the solid-state reaction (i.e., the synthesis reaction in step (B) above). This reduces intermediate products and reaction residues such as carbonates that are generated when the reaction is insufficient, thereby enabling the production of a homogeneous halide solid electrolyte with excellent properties. Furthermore, the high reactivity of halogenation, etc., allows the solid electrolyte to be synthesized in a short time and at a low temperature, resulting in excellent productivity.

[0203] (Technology 7) The method for producing a halide solid electrolyte according to any one of Techniques 1 to 6, wherein in (A), the halogenation treatment of the Li source, the Ti source, and the M source is carried out by heat-treating a thermally decomposable halogen-containing material.

[0204] According to the manufacturing method of Technique 7, halogenation treatment is performed by heat-treating a thermally decomposable halogen-containing material. Therefore, by controlling the heat treatment conditions, simple oxides or simple carbonates used as the Li source, Ti source, and M source can be converted to halides with high productivity. Controlling the heat treatment conditions includes, for example, temperature control or selection of the heat treatment atmosphere. The heat treatment atmosphere can be, for example, air, nitrogen, or a reducing gas. Furthermore, the temperature or progress of halogenation can be controlled by using multiple halogen-containing materials with different thermal decomposition properties (e.g., thermal decomposition temperature and time required for thermal decomposition) or by adjusting the particle size of the halogen-containing materials. Therefore, various oxides and carbonates can be stably and uniformly halogenated.

[0205] (Technology 8) The method for producing a halide solid electrolyte according to Technology 7, wherein the halogen-containing material is in a particulate form.

[0206] According to the manufacturing method of Technology 8, the thermal decomposition property of the halogen-containing material is improved, and the contact area between the starting materials (Li, Ti, and M sources) and the halogen-containing material is increased. This allows for efficient halogenation of the Li, Ti, and M sources. Furthermore, the halogenation reaction can be controlled by the particle shape of the halogen-containing material. For example, by reducing the particle size of the halogen-containing material, the temperature and rate of halogenation of the Li, Ti, and M sources can be increased. Furthermore, by mixing the Li, Ti, and M sources with a particulate halogen-containing material, homogeneous halogenation of the Li, Ti, and M sources is possible. Furthermore, precise control of the halogen content is possible. This allows for the synthesis of a desired halide solid electrolyte. Furthermore, since only the amount of halogen-containing material required for halogenation of the Li, Ti, and M sources can be used, excess halogen gas emissions can be suppressed. This reduces the environmental impact and also reduces the impact on corrosion of furnace materials.

[0207] (Technology 9) The method for producing a halide solid electrolyte according to Technology 7 or 8, wherein (A) comprises: (A-1-1) mixing the Li source and a first halogen-containing material, mixing the Ti source and a second halogen-containing material, and mixing the M source and a third halogen-containing material; and (A-1-2) heat-treating each of the first mixture containing the Li source and the first halogen-containing material, the second mixture containing the Ti source and the second halogen-containing material, and the third mixture containing the M source and the third halogen-containing material obtained in (A-1-1), thereby subjecting the Li source, the Ti source, and the M source to a halogenation treatment.

[0208] According to the manufacturing method of Technology 9, a homogeneous mixture of the starting materials and the halogen-containing material can be subjected to a heat treatment for halogenation. Furthermore, the contact area between the starting materials and the halogen-containing material can be increased. Therefore, according to the manufacturing method of Technology 9, the halogenation of the starting materials can be promoted uniformly and evenly throughout the Li source, Ti source, and M source. Therefore, a homogeneous halide solid electrolyte with excellent properties can be obtained.

[0209] (Technology 10) The method for producing a halide solid electrolyte according to Technology 7 or 8, wherein in (A), the halogen-containing material is heat-treated to generate a halogen gas, and the halogen gas is brought into contact with the Li source, the Ti source, and the M source, thereby subjecting the Li source, the Ti source, and the M source to the halogenation treatment.

[0210] According to the manufacturing method of Technique 10, the Li source, the Ti source, and the M source can be halogenated by the generated halogen gas without directly contacting them with a halogen-containing material. Therefore, even if a halogen-containing material containing an inorganic component in addition to a halogen element is used, it is not necessary to consider inorganic residues in the produced halide solid electrolyte. Therefore, the range of usable halogen-containing materials can be expanded.

[0211] (Technology 11) The method for producing a halide solid electrolyte according to any one of Techniques 8 to 11, wherein the halogen-containing substance includes an ammonium salt.

[0212] Ammonium salts begin to thermally decompose at relatively low temperatures (e.g., about 150°C). Therefore, ammonium salts are unlikely to remain as unnecessary inorganic components in the final halide solid electrolyte, and the Li source, Ti source, and M source can be halogenated at low temperatures. Halogenation at low temperatures refers to the conversion of the Li source, Ti source, and M source to halides, for example, at a temperature in the range of about 150°C or higher and 600°C or lower. When using halide raw materials, a temperature exceeding 600°C (e.g., above 600°C and below 900°C) is required to synthesize the halide solid electrolyte. Therefore, according to the manufacturing method of Technology 11, a halide solid electrolyte can be synthesized without excessive sintering. Therefore, a halide solid electrolyte with excellent pulverizability can be synthesized. Since the manufacturing method of Technology 11 can synthesize a halide solid electrolyte with excellent pulverizability, it is also suitable for producing fine halide solid electrolytes. Furthermore, the manufacturing method of Technology 11 achieves energy saving in synthesis and also reduces the time required for heating and cooling, thereby improving productivity. Furthermore, since synthesis is performed at low temperatures, the durability of furnace materials is improved, and the running costs and replacement frequency of synthesis components are significantly reduced.

[0213] (Technology 12) The method for producing a halide solid electrolyte according to Technology 11, wherein the ammonium salt contains NH4F.

[0214] NH4F is a highly decomposable fluorine source and can effectively act on the fluorination of Li, Ti, and M sources. Therefore, according to the production method of technique 12, NH4F can be thermally decomposed at a low temperature (e.g., about 150°C) and at a fast decomposition rate, and can convert the Li, Ti, and M sources into fluorides without leaving any inorganic substances.

[0215] (Technology 13) The method for producing a halide solid electrolyte according to any one of Techniques 7 to 12, wherein the halogen-containing material includes a resin.

[0216] According to the production method of technique 13, the halogen-containing material can be thermally decomposed at a relatively high temperature (e.g., about 450° C. or higher and 600° C. or lower) to halogenate the Li source, Ti source, and M source without leaving any inorganic matter. Therefore, the production method of technique 14 is suitable for the case where the halogenation of the Li source, Ti source, and M source is to be carried out at a relatively high temperature (e.g., about 450° C. or higher and 600° C. or lower).

[0217] (Technology 14) The method for producing a halide solid electrolyte according to Technology 13, wherein the resin includes a fluororesin.

[0218] Fluororesins such as PTFE can be pyrolyzed at a relatively high temperature (e.g., about 450° C. or higher and 600° C. or lower) to halogenate the Li source, Ti source, and M source. Therefore, the production method of technique 14 is suitable for the case where halogenation is to be performed at a relatively high temperature (e.g., about 450° C. or higher and 600° C. or lower).

[0219] (Technology 15) The method for producing a halide solid electrolyte according to any one of Techniques 7 to 14, wherein the halogen-containing material contains a substance that prevents the halide solid electrolyte from substantially containing inorganic components, except for halogen elements, that are generated by thermal decomposition by the heat treatment in (A).

[0220] The halogen-containing material is required to replace the halogen elements generated by thermal decomposition by the heat treatment in (A) with the oxygen elements of the Li source, Ti source, and M source, while preventing other components from being mixed as inorganic residues into the finally obtained halide solid electrolyte. By using a substance as the halogen-containing material that does not substantially contain inorganic components generated by thermal decomposition by the heat treatment, except for the halogen elements, in the finally obtained halide solid electrolyte, the mixing of inorganic residues into the halide solid electrolyte can be suppressed, and a desired halide solid electrolyte can be obtained. Examples of halogen-containing materials that do not substantially contain inorganic components, except for the halogen elements, generated by thermal decomposition by the heat treatment in the finally obtained halide solid electrolyte include substances in which inorganic components, except for the halogen elements, generated by thermal decomposition by the heat treatment are gasified and discharged.

[0221] (Technology 16) The method for producing a halide solid electrolyte according to any one of Techniques 7 to 15, wherein the halogen-containing material includes a plurality of halogen-containing compounds.

[0222] According to the manufacturing method of Technique 16, for example, both an ammonium salt and a fluororesin can be used as the halogen-containing material. This allows for a wide temperature range in which the halogen-containing material acts as a halogen source. Therefore, the conversion temperatures of the Li source, Ti source, and M source to halides can be controlled over a wide range. Therefore, according to the manufacturing method of Technique 16, it is easy to obtain a desired halide solid electrolyte.

[0223] (Technology 17) The method for producing a halide solid electrolyte according to any one of Techniques 1 to 16, wherein in (A), the halogenation treatment of the Li source, the Ti source, and the M source is carried out at a temperature of 150°C or higher.

[0224] According to the manufacturing method of Technique 17, the halogenation treatment at a relatively low temperature allows the Li source, Ti source, and M source to be converted into halides before sintering and hardening or before grain growth occurs. This method is therefore suitable for producing fine halide solid electrolytes. Furthermore, the resulting solid electrolyte is easy to pulverize, thereby suppressing contamination during pulverization. The halogenation treatment temperature is preferably, for example, 150°C or higher and 450°C or lower. This allows for the production of useful halide solid electrolytes that can be finely pulverized and exhibit reduced deterioration in properties. The heat treatment for the halogenation treatment can be performed in any atmosphere suitable for conversion to various halides, such as air, nitrogen, or a reducing atmosphere.

[0225] (Technology 18) A halide solid electrolyte comprising Li, Ti, Al, and F, and further comprising at least one element selected from the group consisting of P and S.

[0226] This configuration makes it possible to obtain a homogeneous halide solid electrolyte with excellent ionic conductivity.

[0227] (Technology 19) The halide solid electrolyte according to Technology 18, wherein the halide solid electrolyte is in a particulate form, and each particle of the halide solid electrolyte includes a first crystalline phase represented by the following composition formula (4) and a second crystalline phase represented by the following composition formula (5). Composition formula (4): Li2TiX6 Composition formula (5): Li3AlX6

[0228] According to this configuration, a first crystalline phase of Li2TiX6 and a second crystalline phase of Li3MX6 are integrally contained in one particle. Therefore, a halide solid electrolyte in which the first crystalline phase and the second crystalline phase are homogenized is realized. This allows the first crystalline phase and the second crystalline phase to be uniformly dispersed when forming a compact using the halide solid electrolyte or dispersing the halide solid electrolyte for slurry preparation, thereby producing a solid electrolyte layer with high ionic conductivity and excellent stability. The particle size and shape can be selected depending on the application. Such composite particles containing two crystalline phases are formed, for example, by bonding during a solid-state reaction. Therefore, the composite particles can also be made finer by methods such as microparticulating the oxide raw material.

[0229] (Technology 20) The halide solid electrolyte according to Technology 18 or 19, wherein the halide solid electrolyte includes an amorphous material.

[0230] This configuration makes the amorphous portion of the halide solid electrolyte softer and more deformable. Therefore, the halide solid electrolyte compact can be configured into a solid electrolyte layer of any shape with higher ionic conductivity and higher reliability. Therefore, the halide solid electrolyte compact of Technology 20 can realize a solid electrolyte layer for a battery with excellent characteristics and high reliability.

[0231] (Technology 21) The halide solid electrolyte according to Technology 20, wherein the amorphous material is contained in a surface layer of a particle of the halide solid electrolyte and has higher ionic conductivity than the interior of the particle.

[0232] This configuration provides the surface layer of the halide solid electrolyte particles with high ionic conductivity (e.g., 1 μS / cm or more), thereby enhancing the adhesion between the halide solid electrolyte particles and the ionic conductivity, resulting in a solid electrolyte layer of a battery with excellent performance and high reliability.

[0233] (Technology 22) The halide solid electrolyte according to Technology 20 or 21, wherein the amorphous material is contained in a surface layer of a particle of the halide solid electrolyte, and has lower electronic conductivity than the interior of the particle.

[0234] This configuration allows the surface layer of the halide solid electrolyte particles to have low electronic conductivity (e.g., 0.1 μS / cm or less), thereby reducing electronic conduction loss and increasing ionic conductivity, resulting in a solid electrolyte layer for batteries with excellent performance and high reliability.

[0235] (Technology 23) The halide solid electrolyte according to any one of Techniques 18 to 22, wherein an X-ray diffraction pattern obtained by X-ray diffraction measurement of the halide solid electrolyte using Cu-Kα radiation satisfies at least one of the following (1), (2), and (3): (1) no peak derived from TiF4 is present; (2) no peak derived from LiF is present; and (3) no peak derived from AlF3 is present.

[0236] This configuration makes it possible to obtain a halide solid electrolyte with excellent characteristics and reliability.

[0237] (Technology 24) A positive electrode material comprising the halide solid electrolyte according to any one of Technology 18 to Technology 23.

[0238] The cathode material according to Technology 24 makes it possible to realize a battery with excellent charge / discharge characteristics.

[0239] (Technology 25) A battery comprising a positive electrode containing the positive electrode material according to Technology 24.

[0240] This configuration makes it possible to provide a battery with excellent charge / discharge characteristics.

[0241] (Technology 26) A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, wherein at least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the halide solid electrolyte according to any one of Technologies 18 to 23.

[0242] This configuration makes it possible to provide a battery with excellent charge / discharge characteristics.

[0243] While the method for producing a halide solid electrolyte and the halide solid electrolyte according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications conceivable by those skilled in the art to the embodiments and other forms constructed by combining some of the components of the embodiments are also included within the scope of the present disclosure.

[0244] Furthermore, the above-described embodiments can be modified, replaced, added, omitted, and the like in various ways within the scope of the claims or their equivalents.

[0245] The present disclosure will now be described in more detail with reference to examples.

[0246] <Synthesis of Halide Solid Electrolyte> (Example 1) As starting materials, Li2CO3 (average particle size: about 5 μm), Al2O3 (average particle size: about 0.6 μm), TiO2 (average particle size: about 1 μm), a halogen-containing substance NH4F (average particle size: about 35 μm, fluorine source powder), and additives PO5 (average particle size: about 0.5 μm) and S (about 0.6 μm) were prepared.

[0247] 50 g of each of Li2CO3, Al2O3, and TiO2 was placed in a 600 mL polyethylene ball mill together with 600 g of 3 mm diameter zirconia balls and 200 mL of pure water and wet-milled for approximately 20 hours. The pulverized powder slurry was then collected in a stainless steel tray and air-dried at 200 °C for 20 hours to obtain pulverized powders of Li2CO3 (average particle size: approximately 0.6 μm), Al2O3 (average particle size: approximately 0.4 μm), and TiO2 (average particle size: approximately 0.5 μm). The average particle sizes of each were determined using a conventional laser diffraction particle size distribution analyzer.

[0248] Next, a mixture was prepared by uniformly mixing the respective pulverized powders of Li2CO3, Al2O3, and TiO2 with the halogen-containing compound NH4F under atmospheric conditions (approximately 24°C and 40% humidity). The respective pulverized powders of Li2CO3, Al2O3, and TiO2 were mixed with a predetermined amount of NH4F in an alumina mortar and pestle for approximately 10 minutes until uniform. This resulted in a mixture of the respective pulverized powders of Li2CO3, Al2O3, and TiO2 with NH4F. The NH4F powder was added in an amount necessary to fluorinate the raw materials. Specifically, an amount of NH4F sufficient to fluorinate all of the raw materials was used according to the reaction formula.

[0249] Approximately 3 g of each of the three resulting mixtures was placed into three high-purity (SSA-H) alumina crucibles (diameter φ: 36 mm, height: 40 mm). Next, a spacer (0.5 mm thick) was placed around the outer edge of the top surface of the crucible to allow clearance for the reactive gases (mainly ammonia and CO2) emitted during heat treatment to escape, and an alumina plate-shaped lid (1 mm thick) was placed on top to prevent foreign objects from falling. Next, the crucibles were placed on top of small mullite craters with a porosity of approximately 20% and a low heat capacity in the center of the firing furnace, and heat treatment was performed. The craters were 10 mm long, 10 mm wide, and 10 mm high, with three craters placed under each crucible, floating the sagger above the furnace bottom. The other two crucibles were installed in the same manner. In this way, heater (radiant) heat and inert gas were allowed to reach the bottom of the crucible. After closing and sealing the furnace door, nitrogen gas was introduced at 1 L / min through an inlet at the bottom of the furnace and discharged through an exhaust port above the ceiling. The gas flow continued until the heat treatment was completed. After the furnace was cooled, the crucible was removed from the furnace and the halogenated powder was recovered. XRD analysis confirmed that the powders had been converted to fluorides, LiF, AlF, and TiF0, respectively, with no oxides remaining. The heat treatment temperature was 300°C.

[0250] Next, when the synthesized halide solid electrolyte is expressed by the composition formula (3): xLi2TiX6-(1-x)Li3MX6, LiF, AlF3, and TiF2O powders were weighed out so that x = 0.25. In this example, in the composition formula (3), X is F and M is Al. Furthermore, as for the additives, PO5 powder and S powder were weighed out so that LiPF6 was 0.1 mol% and S was 0.03 mol% relative to [0.25Li2TiF6-0.75Li3AlF6]. These weighings were performed in an air atmosphere.

[0251] As in the halogenation treatment, approximately 3 g of the weighed mixed powder was placed in a high-purity alumina crucible (diameter: φ36 mm, height: 40 mm). A spacer (0.5 mm thick) was placed on the outer edge of the top surface of the sheath, and an alumina plate-shaped lid was placed on top to prevent foreign matter from falling. The powder was then placed on a mullite crucible with a low heat capacity and porosity of approximately 20% in the center of the firing furnace and heat-treated at 650 °C for 4 hours in a nitrogen atmosphere (nitrogen flow rate: 1 L / min). After furnace cooling, the powder was recovered. XRD confirmed two crystalline phases, Li3AlF6 and Li2TiF6, with no other precipitated phases detected. The powder obtained after firing had an average particle size of approximately 0.6 μm and a BET specific surface area of ​​approximately 3.6 m 2 / g of fine powder.

[0252] The halide solid electrolyte obtained by the heat treatment was subjected to a pulverization treatment. This pulverization treatment included a mechanochemical treatment. The halide solid electrolyte (average particle size: approximately 0.6 μm) obtained by the heat treatment was pulverized to an average particle size of approximately 0.4 μm. In this example, the pulverization treatment was carried out by a dry method. Zirconia balls (diameter: φ25 mm, 1.4 kg) and 3 g of the halide solid electrolyte were placed in a general ball mill (capacity: 1 L) lined with polyethylene or Teflon (registered trademark), and dry-pulverized for approximately 20 hours. The pulverized particles had an average particle size of approximately 0.4 μm (BET specific surface area = approximately 5.3 m). 2 / g).

[0253] Comparative Example 1 A halide solid electrolyte was synthesized using a method similar to that used for the solid electrolyte material of the example described in Patent Document 1. That is, fluoride was used as a starting material, and the halide solid electrolyte of Comparative Example 1 was produced by mechanochemical synthesis. Specifically, LiF, TiF, and AlF were prepared in a molar ratio of LiF:TiF:AlF = 2.75:0.25:0.75. These materials were ground and mixed in a mortar. The resulting mixture was milled for 12 hours at 500 rpm using a planetary ball mill. In this manner, the halide solid electrolyte of Comparative Example 1 was synthesized.

[0254] <Evaluation of Halide Solid Electrolyte> The halide solid electrolyte of Example 1 synthesized as described above was evaluated for its crystalline phase, ionic conductivity, electronic conductivity, average particle size, and BET specific surface area. The crystalline phase, ionic conductivity, average particle size, and BET specific surface area were evaluated for the halide solid electrolyte both after the heat treatment and before the pulverization treatment, and after the pulverization treatment. The crystalline phase of the halide solid electrolyte of Comparative Example 1 was also evaluated. The halide solid electrolyte of Example 1 was also analyzed for trace components.

[0255] (Crystalline Phase) The crystalline phase was confirmed by powder X-ray diffraction measurement both before and after the heat treatment and grinding treatment. An X-ray diffractometer (MiniFlex 600, manufactured by RIGAKU Corporation) was used for the measurement. Cu-Kα radiation (wavelengths 1.5405 Å and 1.5444 Å) was used as the X-ray source.

[0256] FIG. 6A is a graph showing the X-ray diffraction pattern of the halide solid electrolyte after heat treatment but before pulverization in the manufacturing method of Example 1. FIG. 6B is a graph showing the X-ray diffraction pattern of the halide solid electrolyte after pulverization obtained in Example 1 and the halide solid electrolyte obtained in Comparative Example 1. As shown in FIG. 6A, Li2TiF6 corresponding to the first crystalline phase and Li3AlF6 corresponding to the second crystalline phase were confirmed in the halide solid electrolyte synthesized in Example 1. As shown in FIG. 6B, the crystallinity of the halide solid electrolyte after pulverization obtained in Example 1 was reduced by the pulverization compared to the halide solid electrolyte before pulverization, but no extra precipitated phase was observed. In contrast, as shown in FIG. 6B, the halide solid electrolyte obtained in Comparative Example 1 exhibited a compositional variation compared to the halide solid electrolyte of Example 1, and the presence of LiF and AlF3 was also confirmed.

[0257] (Ionic Conductivity) The ionic conductivity was calculated from the area, thickness, and room temperature impedance characteristics of a compacted powder sample obtained by placing a halide solid electrolyte powder in a 10 mm diameter mold and applying a pressure of approximately 3 t / cm using a uniaxial hydraulic press. The impedance measurement was performed at room temperature while applying pressure. The impedance measurement was performed at a measurement frequency of 10 Hz to 10 MHz, a measurement voltage of 1 Vrms, and no DC bias. The deviation in the electrical length of the cable and the measurement jig was offset and evaluated. For the halide solid electrolyte of Example 1, the ionic conductivity before the pulverization treatment was 1.1 μS / cm, and the ionic conductivity after the pulverization treatment was 5.7 μS / cm.

[0258] (Electronic Conductivity) The electronic conductivity was calculated from DC voltage and current characteristics. The electronic conductivity of the halide solid electrolyte of Example 1 was <1.0 × 10 -8 This was a value that could be judged to have no electronic conductivity.

[0259] (Average Particle Diameter) The average particle diameter is the value of the median diameter D50 obtained from the volume particle size distribution measured by a laser diffraction scattering particle size distribution analyzer. Specifically, a halide solid electrolyte powder was dispersed in a 0.01 wt % aqueous solution of sodium hexametaphosphate using a homogenizer, and then the particle size distribution of the halide solid electrolyte was measured using a laser diffraction scattering particle size distribution analyzer (manufactured by Microtrac, product name: MT3100II). The value of D50 (i.e., cumulative 50% particle diameter) of the measured particle size distribution was regarded as the average particle size. For the halide solid electrolyte of Example 1, the average particle diameter before pulverization was 0.60 μm, and the average particle diameter after pulverization was 0.40 μm.

[0260] (BET Specific Surface Area) The BET specific surface area was determined by a BET multipoint method using a nitrogen gas adsorption apparatus. The halide solid electrolyte of Example 1 had a BET specific surface area of ​​3.6 m before pulverization. 2 / g, and the BET specific surface area after pulverization was 5.3 m 2 / g.

[0261] (Analysis of Trace Components) Trace components contained in the halide solid electrolyte were analyzed using EPMA. Specifically, the analysis was performed as follows. A sample (powder) of the halide solid electrolyte was attached to conductive tape and fixed (the sample was fixed to a 5 mm x 5 mm area to form a solid), and the composition (quantitative) was examined by point analysis or area analysis. Although not confirmed by X-ray diffraction measurement, it was confirmed that the halide solid electrolyte of Example 1 contained Nb and Ga. The P content was 0.08 at. %, and the S content was 0.03 at. %.

[0262] From the evaluation results of the halide solid electrolyte obtained in Example 1, it was found that the manufacturing method of the present disclosure was able to synthesize a homogeneous halide solid electrolyte, resulting in a high ionic conductivity of 5.7 μS / cm. This ionic conductivity was at a level equal to or higher than that obtained from synthesis using a fluoride raw material, and the manufacturing method of the present disclosure was able to obtain a halide solid electrolyte with excellent properties. The electronic conductivity was <1.0 × 10 -8 It was confirmed that the electrolyte had no electronic conductivity (i.e., negligible electronic conductivity) and was an ionically conductive solid electrolyte.

[0263] The X-ray diffraction patterns shown in FIGS. 6A and 6B confirmed that the method of Example 1 could produce a halide solid electrolyte containing Li2TiF6 corresponding to the first crystalline phase and Li3AlF6 corresponding to the second crystalline phase. These X-ray diffraction patterns also confirmed that the halide solid electrolyte obtained in Example 1 had similar crystalline quality to the halide solid electrolyte of Comparative Example 1 synthesized by a conventional method, and that compositional variation was suppressed compared to the halide solid electrolyte of Comparative Example 1. Furthermore, for the halide solid electrolyte of Example 1, the X-ray diffraction pattern after the milling process exhibited broader peaks than the X-ray diffraction pattern before the milling process, confirming the progression of amorphization. However, no new precipitated phases were observed due to the milling process. The changes in ionic conductivity, average particle size, and BET specific surface area before and after the milling process are as described in the sections describing each evaluation item. These results show that the pulverization treatment may or may not be performed depending on the application of the halide solid electrolyte, and that the composition and crystalline phase of the halide solid electrolyte are substantially unchanged regardless of whether the pulverization treatment is performed or not, thereby maintaining excellent properties.

[0264] As described above, according to the manufacturing method of the present disclosure, a halide solid electrolyte containing Li, Ti, M, and X can be manufactured by a normal synthesis process (i.e., without sealing or the like, and in a synthesis environment in the atmosphere) with little compositional variation and with ionic conductivity as high as that of conventional manufacturing methods. Furthermore, whereas halide raw materials are extremely expensive, the manufacturing method of the present disclosure uses inexpensive oxide raw materials, thereby reducing the manufacturing cost of the halide solid electrolyte.

[0265] The method for producing a halide solid electrolyte according to the present disclosure can be used, for example, as a method for producing a solid electrolyte for secondary batteries such as all-solid-state batteries used in various electronic devices or automobiles.

Claims

1. A method for producing a halogen solid electrolyte containing Li, Ti, M, and X, The aforementioned M is at least one element selected from the group consisting of metallic elements (excluding Li and Ti) and metalloid elements. The aforementioned X is at least one selected from the group consisting of F, Cl, Br, and I. The aforementioned manufacturing method is (A) A halogenation treatment is performed on each of the following: at least one Li source selected from the group consisting of simple oxides and simple carbonates of Li, at least one Ti source selected from the group consisting of simple oxides and simple carbonates of Ti, and at least one M source selected from the group consisting of simple oxides and simple carbonates of M, in order to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M. (B) Synthesizing the halogen solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M, A method for producing a halogenated solid electrolyte, including [the specified substance].

2. The above (A) is, (A-0) Grinding at least one selected from the group consisting of the Li source, the Ti source, and the M source, (A-1) After (A-0), halogenation treatment is performed on each of the Li source, Ti source, and M source to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M. A method for producing a halogenated solid electrolyte according to claim 1, comprising:

3. The aforementioned halide solid electrolyte comprises a first crystalline phase represented by the following compositional formula (1) and a second crystalline phase represented by the following compositional formula (2). A method for producing a halogenated solid electrolyte according to claim 1. Composition formula (1): Li 2 TiX 6 Composition (2): Li 3 MX 6

4. The above M includes Al, A method for producing a halogenated solid electrolyte according to claim 1.

5. The aforementioned X includes F, A method for producing a halogenated solid electrolyte according to claim 1.

6. The Li source, the Ti source, and the M source are particulate. A method for producing a halogenated solid electrolyte according to claim 1.

7. In (A) above, the halogenation treatment of the Li source, the Ti source, and the M source is carried out by heat treatment of a halogen-containing material that is thermally decomposable. A method for producing a halogenated solid electrolyte according to claim 1.

8. The halogen-containing substance is in particulate form. A method for producing a halogen solid electrolyte according to claim 7.

9. The above (A) is, (A-1-1) Mixing the Li source with the first halogen-containing substance, mixing the Ti source with the second halogen-containing substance, and mixing the M source with the third halogen-containing substance, (A-1-2) By heat-treating the first mixture containing the Li source and the first halogen-containing substance obtained in (A-1-1), the second mixture containing the Ti source and the second halogen-containing substance, and the third mixture containing the M source and the third halogen-containing substance, the Li source, the Ti source, and the M source are subjected to halogenation treatment. A method for producing a halogenated solid electrolyte according to claim 7, comprising:

10. In (A) above, a halogen gas is generated by heat-treating the halogen-containing material, and the halogen gas is brought into contact with the Li source, the Ti source, and the M source, thereby performing the halogenation treatment on the Li source, the Ti source, and the M source. A method for producing a halogen solid electrolyte according to claim 7.

11. The halogen-containing substance includes an ammonium salt. A method for producing a halogen solid electrolyte according to claim 7.

12. The ammonium salt is NH 4 Including F, A method for producing a halogenated solid electrolyte according to claim 11.

13. The halogen-containing material includes a resin. A method for producing a halogen solid electrolyte according to claim 7.

14. The aforementioned resin includes a fluororesin. A method for producing a halogenated solid electrolyte according to claim 13.

15. The halogen-containing substance includes a substance that substantially excludes inorganic components produced by thermal decomposition by the heat treatment in (A) from the halogen element, in the halogen solid electrolyte. A method for producing a halogen solid electrolyte according to claim 7.

16. The halogen-containing substance includes multiple types of halogen-containing compounds. A method for producing a halogen solid electrolyte according to claim 7.

17. In (A) above, the halogenation treatment of the Li source, the Ti source, and the M source is carried out at a temperature of 150°C or higher. A method for producing a halogenated solid electrolyte according to claim 1.

18. It includes Li, Ti, Al, and F, and Further comprising at least one selected from the group consisting of P and S, Halide solid electrolytes.

19. The halogenated solid electrolyte is in particulate form. Each particle of the halide solid electrolyte comprises a first crystalline phase represented by the following compositional formula (4) and a second crystalline phase represented by the following compositional formula (5), where X is F in compositional formulas (4) and (5). The halogenated solid electrolyte according to claim 18. Composition formula (4): Li 2 TiX 6 Composition formula (5): Li 3 AlX 6

20. The halogen solid electrolyte includes an amorphous phase. The halogenated solid electrolyte according to claim 19.

21. The amorphous phase is contained on the surface of the particles of the halide solid electrolyte and has higher ionic conductivity than the interior of the particles. The halogenated solid electrolyte according to claim 20.

22. The amorphous phase is contained on the surface of the particles of the halide solid electrolyte and has lower electronic conductivity than the interior of the particles. The halogenated solid electrolyte according to claim 20.

23. In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the halide solid electrolyte using Cu-Kα rays, at least one selected from the group consisting of (1), (2), and (3) below is satisfied. The halogenated solid electrolyte according to claim 18. (1) TiF 4 There is no peak in the origin. (2) No peaks originating from LiF are present. (3) AlF 3 There is no peak in the origin.

24. A positive electrode material comprising a halide solid electrolyte as described in claim 18.

25. A battery comprising a positive electrode containing the positive electrode material described in claim 24.

26. positive electrode, Negative electrode, and An electrolyte layer provided 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 halogenated solid electrolyte described in claim 18. battery.