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

Abstract

The method for producing a halide solid electrolyte according to the present disclosure comprises: (A) halogenating an oxide mixture containing a composite oxide containing Li and Ti and an oxide raw material containing Li and M, thereby obtaining 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.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a halide solid electrolyte, a halide solid electrolyte, a cathode material, and a battery. Background Technology

[0002] Patent Document 1 discloses a halide-based solid electrolyte material. Furthermore, Patent Document 2 discloses a halide-based solid electrolyte material as a solid electrolyte material used to coat the surface of a positive electrode active material.

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2021 / 186809 Patent Document 2: International Publication No. 2021 / 187391 Summary of the Invention

[0004] The problem that the invention aims to solve The purpose of this disclosure is to provide a novel manufacturing method for the stable synthesis of halide solid electrolytes with a target composition.

[0005] Methods for solving problems The method for manufacturing a halide solid electrolyte disclosed herein includes: (A) performing a halogenation treatment on an oxide mixture containing a composite oxide containing Li and Ti and an oxide raw material containing Li and M, thereby obtaining a halide solid electrolyte containing Li, Ti, M and X.

[0006] Here, M is at least one element selected from metallic elements (excluding Li and Ti) and metalloid elements. X is at least one selected from F, Cl, Br and I.

[0007] Invention Effects This disclosure provides a novel manufacturing method capable of stably synthesizing halide solid electrolytes with a target composition. Attached Figure Description

[0008] Figure 1 This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the first embodiment.

[0009] Figure 2 This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the second embodiment.

[0010] Figure 3 This is a flowchart illustrating a modified example of the method for manufacturing a halide solid electrolyte according to the second embodiment.

[0011] Figure 4This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the third embodiment.

[0012] Figure 5 A cross-sectional view showing the battery 1000 according to the fourth embodiment.

[0013] Figure 6A This is a diagram showing the X-ray diffraction pattern of the halide solid electrolyte after heat treatment and before pulverization in the manufacturing method of Example 1.

[0014] Figure 6B This is a graph showing the X-ray diffraction patterns of the halide solid electrolyte obtained in Example 1 after pulverization and the halide solid electrolyte obtained in Comparative Example 1. Detailed Implementation

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0016] The embodiments described below are either general or specific examples. The numerical values, shapes, materials, and constituent elements shown in the following embodiments are examples and are not intended to limit this disclosure. In addition, the constituent elements in the following embodiments that are not described in the independent claims representing the highest concept are described as optional constituent elements.

[0017] [First Implementation Method] The method for manufacturing the halide solid electrolyte in the first embodiment will be described below.

[0018] The manufacturing method of the first embodiment includes: (A) performing a halogenation treatment on an oxide mixture containing a composite oxide containing Li and Ti and an oxide raw material containing Li and M, thereby obtaining a halide solid electrolyte containing Li, Ti, M and X. Here, M is at least one element selected from metallic elements (excluding Li and Ti) and metalloid elements, and X is at least one element selected from F, Cl, Br and I.

[0019] "Metalloids" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements contained in Groups 1 through 12 of the periodic table (except for hydrogen) and all elements contained in Groups 13 through 16 of the periodic table (except for B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). In other words, "metallic elements" are the group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0020] According to the manufacturing method of the first embodiment, a halide solid electrolyte having the target composition can be stably synthesized. The reasons will be explained in more detail below.

[0021] In conventional manufacturing methods, titanium halides (e.g., TiX4) are typically used as the Ti source to produce Ti-containing halide solid electrolytes. However, titanium halides are relatively unstable substances, such as being easily evaporable and deliquescent. Therefore, the produced halide solid electrolytes sometimes experience compositional changes (i.e., compositional deviations) and deterioration (e.g., the presence of moisture). Consequently, conventional manufacturing methods sometimes struggle to stably obtain the target halide solid electrolyte. In contrast, in the manufacturing method of the first embodiment, a composite oxide containing Li and Ti can be used as the Ti source. Therefore, in the manufacturing method of the first embodiment, the unstable titanium halides described above are not required as a raw material in the synthesis of Ti-containing halide solid electrolytes, and titanium halides are less likely to form during the synthesis process. Therefore, the manufacturing method of the first embodiment is less prone to the compositional changes and deterioration described above in the produced halide solid electrolytes, and can, for example, reproduce and stably synthesize Ti-containing halide solid electrolytes with excellent ionic conductivity and other properties. That is, according to the manufacturing method of the first embodiment, a halide solid electrolyte having the target composition can be stably synthesized.

[0022] In (A) above, the halogenation treatment of the oxide mixture can be carried out at a temperature of 150°C or higher. By carrying out the halogenation treatment at a temperature of 150°C or higher, the oxide mixture can be sufficiently halogenated. The temperature during the halogenation treatment can be, for example, 600°C or lower. It should be noted that the atmosphere for the halogenation treatment can be appropriately selected, for example, any atmosphere suitable for the halogen-containing substance used, such as the atmosphere, a nitrogen atmosphere, or a reducing atmosphere.

[0023] In (A) above, the halogenation treatment of the oxide mixture can be carried out, for example, by heat treatment of a halogen-containing substance that is thermally decomposable.

[0024] By performing halogenation treatment on an oxide mixture using a thermally decomposable halogen-containing substance, both halogenation of the oxide mixture and solid-phase reaction for synthesizing halide solid electrolytes can occur simultaneously. Therefore, homogeneous solid electrolytes with excellent properties can be obtained while reducing reaction residues such as oxides in a short time. Furthermore, since halogenation treatment is performed by thermally treating a thermally decomposable halogen-containing substance, the oxide mixture exhibits good reactivity (halogenation properties) and excellent productivity. Moreover, for example, the temperatures of the halogenation reaction and the solid-phase reaction of the oxide mixture, as well as the conduction of these reactions, can be controlled based on the selected thermal decomposition temperature of the halogen-containing substance. Therefore, the desired halide solid electrolyte can be obtained.

[0025] In the case of using a thermally decomposable halogen-containing substance in the halogenation treatment of the oxide mixture, the manufacturing method of the first embodiment may also include the above-mentioned (A): (A-1) Mix the above oxide mixture with the above halogen-containing substance; and (A-2) The oxide mixture obtained in (A-1) is subjected to halogenation treatment by heat treatment of the mixture containing the oxide mixture and the halogen-containing substance.

[0026] In the manufacturing method of the first embodiment, by performing steps (A-1) and (A-2) as described above, a homogeneous mixture of an oxide mixture and a halogen-containing substance can be subjected to heat treatment for halogenation. Furthermore, the contact area between the oxide mixture and the halogen-containing substance can be increased. As a result, the halogenation of the oxide mixture is homogenized and promoted, thus yielding a homogeneous halide solid electrolyte with excellent properties.

[0027] Figure 1 This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the first embodiment. An example of the manufacturing method according to the first embodiment is described, illustrating an example of implementing the manufacturing methods described in (A-1) and (A-2) above.

[0028] like Figure 1 As shown, in one example of the manufacturing method of the first embodiment, firstly, as a step equivalent to (A-1) above, an oxide mixture and a halogen-containing substance are mixed (S11). As described above, the oxide mixture comprises a composite oxide containing Li and Ti and an oxide raw material containing Li and M. The halogen-containing substance is thermally decomposable. Next, as a step equivalent to (A-2) above, the obtained mixture containing the oxide mixture and the halogen-containing substance is subjected to halogenation treatment by heat treatment (S12). Thus, a halide solid electrolyte containing Li, Ti, M, and X is obtained.

[0029] The following describes in detail the oxide mixture, the halogen-containing substance, and the processes equivalent to (A-1) and (A-2) above.

[0030] <Oxide Mixture> The oxide mixture includes composite oxides containing Li and Ti, as well as oxide raw materials containing Li and M.

[0031] The Li and Ti composite oxide only needs to contain at least Li, Ti, and O, and may further contain other cations. By using the Li and Ti composite oxide as the Ti source, compositional variations and deterioration of the halide solid electrolyte can be suppressed, and a desired halide solid electrolyte with high ionic conductivity and reliability can be manufactured. According to the manufacturing method of the first embodiment, it is not necessary to use titanium oxide (e.g., TiO2) as the Ti source. Titanium oxide is independent of the crystal system (rutile, anatase), and during halogenation, it easily generates titanium halides (e.g., TiX4) that are prone to evaporation and deliquescence. As a result, the Ti component disappears during synthesis, or moisture is contained due to the deliquescence of titanium halides, sometimes leading to deviations from the desired composition. Therefore, titanium halides sometimes become a cause of reduced ionic conductivity and reliability of the solid electrolyte. In the manufacturing method of the first embodiment, the Li and Ti composite oxide can be used as the Ti source, so it is not necessary to use titanium oxide. Therefore, the compositional variations and deterioration of the halide solid electrolyte caused by the use of titanium oxide as described above can be suppressed.

[0032] For the reasons stated above, the oxide mixture preferably does not substantially contain TiO2. In this specification, "the oxide mixture does not substantially contain TiO2" means that the TiO2 content in the overall oxide mixture is 0.3% by mass or less.

[0033] The aforementioned composite oxide may, for example, contain Li₂TiO₃. Li₂TiO₃ exhibits excellent stability in normal atmospheric conditions (including moisture), and consequently, excellent stability up to approximately 800°C. By using Li₂TiO₃ as the composite oxide, it is possible to fabricate halide solid electrolytes containing a crystalline phase represented by Li₂TiX₆.

[0034] Oxide feedstocks containing Li and M, such as oxides containing Li and M, can be used. By using oxides of Li and M as oxide feedstocks, halide solid electrolytes with the target composition can be synthesized more stably.

[0035] M can be at least one selected from Al, Y, Ga, Dy, Ho, Er, Tm, and Yb. M can be at least one selected from Al and Y. By including the above elements in M, halide solid electrolytes with high ionic conductivity can be obtained.

[0036] M can contain Al. By including Al in M, a halide solid electrolyte with high ionic conductivity can be obtained. M can be Al.

[0037] As oxide raw materials, metal oxides such as Li₂O and Al₂O₃ can be used. Oxide raw materials can include Li₂O and Al₂O₃.

[0038] The oxide mixture can be, for example, in particulate form. That is, the composite oxide constituting the oxide mixture and the oxide raw material can each be in particulate form. This facilitates the simultaneous occurrence of halogenation (i.e., substitution of halogen elements with oxygen elements) from the particle surface of the oxide mixture and solid-phase reactions within the oxide mixture. Therefore, reaction residues such as oxides can be reduced in a short time, and halides can be synthesized. Thus, a homogeneous halide solid electrolyte with excellent properties can be obtained. Furthermore, the particulate oxide mixture exhibits good reactivity, such as halogenation and solid-phase reactivity, thereby enabling excellent productivity.

[0039] Composite oxides such as Li₂TiO₃ can have an average particle size of 0.5 μm or more and 20 μm or less. However, the average particle size of composite oxides is not limited to the above range, and from the viewpoint of halogenation and solid-state reaction with oxide raw materials, any particle size and shape can be appropriately selected. For example, the smaller the particle size of the composite oxide, the lower the conversion temperature from the composite oxide to the halide.

[0040] It should be noted that the average particle size of the composite oxide is the median particle size of the composite oxide, which refers to the particle size (d50) equivalent to 50% of the volume cumulative particle size, determined by the particle size distribution measured on a volume basis using laser diffraction scattering. The same applies to the average particle size of the oxide raw materials and halogen-containing substances specifically specified in this specification.

[0041] Oxide raw materials such as Li₂O and Al₂O₃ can have an average particle size of 0.5 μm or more and 20 μm or less. Similar to composite oxides, oxide raw materials can also have arbitrary particle size and shape.

[0042] <Halogen-containing substances> Halogen-containing substances are thermally decomposable. For example, in the case where the target halide solid electrolyte contains F as the halogen element X, a fluorine-containing substance that serves as the fluorine source is used as the halogen-containing substance.

[0043] The thermal decomposition start temperature of the halogen-containing material used can be, for example, above 100°C and below 600°C. Because the halogen-containing material has a thermal decomposition start temperature within the above temperature range, it exhibits stability during storage and mixing operations, and prevents the resulting halide solid electrolyte from becoming too hard.

[0044] The halogen element X can include F or be F alone. This allows for the production of halide solid electrolytes with excellent stability (e.g., excellent electrochemical stability and heat resistance) and high ionic conductivity.

[0045] Halogen-containing materials can be in particulate form, for example. However, they are prone to thermal decomposition. Therefore, by using particulate halogen-containing materials, the oxide mixture can be halogenated efficiently, and halogen-containing materials are less likely to remain in the final halide solid electrolyte. Furthermore, by using particulate halogen-containing materials, the amount of halogen can be precisely controlled. Therefore, the synthesis of the desired halide solid electrolyte becomes easier. Additionally, only the amount of halogen-containing material required for the halogenation of the oxide mixture can be used, thus suppressing the emission of excess halogen gases. Therefore, the environmental impact is reduced, and consequently, the corrosion effect on furnace materials, etc., is also reduced.

[0046] Halogen-containing substances can have 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, or an average particle size of 0.5 μm or more and 100 μm or less. Similar to composite oxides and oxide raw materials, halogen-containing substances can also have arbitrary particle size and shape.

[0047] The average particle size of the halogen-containing material can be larger than that of the oxide mixture. This results in a state where the surface area of ​​the oxide mixture is larger than that of the halogen-containing material, meaning the exposed surface area of ​​the oxide mixture is greater. Therefore, halogenation is readily performed from the particle surface of the oxide mixture, thus yielding homogeneous halides. The average particle size of the halogen-containing material can be 5 μm or more and 100 μm or less, or 5 μm or more and 20 μm or less, or 50 μm or more and 100 μm or less. The average particle size of the halogen-containing material can be appropriately adjusted by considering the halogenation temperature or reactivity. For example, by increasing the average particle size of the halogen-containing material, the heat treatment temperature used for halogenation can be increased.

[0048] Halogen-containing materials can include ammonium salts. Ammonium salts begin to thermally decompose at relatively low temperatures (e.g., about 150°C). Therefore, ammonium salts are less likely to remain as unwanted inorganic components in the final halide solid electrolyte and can thermally decompose at low temperatures, halogenating the oxide mixture. Thus, by using ammonium salts as halogen-containing materials, unwanted inorganic components from the halogen-containing material can be suppressed from remaining in the final halide solid electrolyte. Furthermore, energy savings in synthesis are achieved, heating and cooling times are reduced, and productivity is increased. Additionally, since synthesis can be performed at low temperatures, furnace material durability is improved, and the operating costs and replacement frequency of synthesis components are significantly reduced. Ammonium salts can be used alone as halogen-containing materials.

[0049] Ammonium salts can include NH4F. NH4F is a highly decomposable fluorine source and can effectively act on the halogenation of oxide mixtures. Therefore, NH4F can fluorinate oxide mixtures without residue in the solid electrolyte while undergoing thermal decomposition at low temperatures (e.g., about 150°C) and at a fast decomposition rate. It should be noted that ammonium salts of other halogen elements, such as NH4Cl and NH4Br, are also thermally decomposable and can therefore be used as halogen sources in the same way.

[0050] Halogen-containing substances can include resins. By including resins as halogen-containing substances, the halogen-containing substances can undergo thermal decomposition at relatively high temperatures (e.g., above about 450°C and below 600°C) while halogenating the oxide mixture. Therefore, the method of including resins as halogen-containing substances is suitable for situations where it is desired to perform halogenation and solid-phase reactions at relatively high temperatures (e.g., above about 450°C and below 600°C).

[0051] Examples of resins used as halogen-containing substances are fluoropolymers. For example, polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used. Fluoropolymers such as PTFE can halogenate oxide mixtures while undergoing thermal decomposition at relatively high temperatures (e.g., above about 450°C and below 600°C). Therefore, methods involving fluoropolymers as halogen-containing substances are suitable for situations where halogenation and solid-phase reactions need to be performed at relatively high temperatures (e.g., above about 450°C and below 600°C).

[0052] The halogen-containing substance may include, for example, a substance that substantially eliminates the inorganic components other than halogen elements produced by thermal decomposition through heat treatment as described in (A) above. For the halogen-containing substance used in the halogenation process, it is required that while the halogen elements produced by thermal decomposition through heat treatment as described in (A) above are replaced by the oxygen elements in the oxide mixture, other components are not mixed into the final halide solid electrolyte as inorganic residues. By using a halogen-containing substance that substantially eliminates the inorganic components other than halogen elements produced by thermal decomposition through heat treatment in the final halide solid electrolyte, the mixing of inorganic residues into the halide solid electrolyte can be suppressed, resulting in the desired halide solid electrolyte. In this specification, "substantially eliminating the inorganic components other than halogen elements produced by thermal decomposition through heat treatment in the manufactured halide solid electrolyte" means that the content of the aforementioned inorganic components in the halide solid electrolyte is, for example, 0.5% by mass or less.

[0053] Halogen-containing substances can include a variety of halogen-containing compounds. For example, ammonium salts and fluoropolymers can both be used as halogen-containing substances. Therefore, a wider temperature range can be controlled for the halogen-containing substances to function as halogen sources, thus allowing for wider control of the conversion of oxide mixtures to halides and the solid-phase reaction temperature. Consequently, the desired halide solid electrolytes can be readily obtained.

[0054] The amount of halogenated substance used is not particularly limited, as long as it is sufficient to halogenate the total amount of the compound to be halogenated. For example, regarding the amount of halogenated substance, in the reaction of halogenating the compound to be halogenated, if the molar amount of halogenated substance used to halogenate the compound stoichiometrically (i.e., the stoichiometric equivalent molar amount, in other words, the molar amount required to completely replace the anion of the compound to be halogenated with a halogen anion such as F) is set to 100%, it can 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.

[0055] <About (A-1)> In (A-1), an oxide mixture and a halogen-containing substance are mixed. In mixing the oxide mixture and the halogen-containing substance, for example, a composite oxide containing Li and Ti, an oxide raw material containing Li and M, and a thermally decomposable halogen-containing substance are uniformly mixed. This allows for simultaneous mixing of the composite oxide, the oxide raw material, and the halogen-containing substance, or it allows for the first uniform mixing of the composite oxide and the oxide raw material to obtain an oxide mixture, followed by mixing of the oxide mixture with the halogen-containing substance.

[0056] In this way, as a preparatory step before halogenation, a process of uniformly mixing the composite oxide, oxide raw materials, and halogen-containing substances can be carried out, enabling a uniform conversion from the oxide mixture to the halide. This allows the synthesis of a homogeneous halide solid electrolyte.

[0057] For example, the composite oxide, oxide raw material, and halogen-containing powder are mixed in a desired ratio. For example, any method that allows for uniform dry mixing of the composite oxide, oxide raw material, and halogen-containing powder is acceptable. For example, uniform mixing can be achieved by repeated mixing with a scraper, or by using a dry mixing machine such as a mortar and pestle, a grinder, or a V-type mixer. Alternatively, a medium such as zirconia balls can be used for mixing. Any mixing method can be employed as long as the powders can be uniformly mixed. Uniformity can be evaluated, for example, using energy dispersive X-ray spectrophotometry (EDS) or electron probe microanalysis (EPMA). For example, uniformity can be confirmed by observing composition mapping images.

[0058] <About (A-2)> In (A-2), the oxide mixture obtained in (A-1) is subjected to halogenation treatment by heat treatment of the mixture containing the oxide mixture and the halogen-containing substance.

[0059] Heat treatment can also be performed using a conventional electric furnace. The heat treatment atmosphere can be selected as needed, and heat treatment can be carried out in the atmosphere, inert gas atmospheres (such as nitrogen or argon), or reducing gas atmospheres (such as hydrogen or carbon dioxide). Synthesized halides are usually obtained in powder form, but when heat treatment is performed above the melting point, they are sometimes obtained in the form of melts, sintered bodies, or blocks formed by solidifying powder.

[0060] In heat treatment, for example, the homogeneous mixture described above is placed in a heat-resistant container (boiler) made of alumina, and the mixture is calcined in a calcining furnace under any atmosphere. For example, while introducing inert gases such as nitrogen into the furnace and venting gases generated during halogenation (such as ammonium, hydrogen chloride, carbon dioxide, etc.), heat treatment is performed in an atmosphere furnace at a temperature of, for example, 150°C or higher and 600°C or lower for a time of, for example, 1 hour or higher and 40 hours or less, to synthesize a halide solid electrolyte. In this way, by introducing and venting gases into the calcining furnace, unwanted reaction gas components are not left in the furnace, i.e., in the halide solid electrolyte.

[0061] The preferred method for introducing inert gas into the furnace is to prevent it from directly contacting the cauldron containing the mixture. Alternatively, atmospheric air can be introduced instead of inert gas. A plate larger than the gas inlet is placed between the gas inlet and the cauldron. The plate's thickness is sufficient to prevent damage from gas flow or operation. More preferably, it provides partial shielding, for example, by raising an alumina plate. In this way, by shielding the gas inlet from the cauldron, the gas bypasses the shielding plate and comes into contact with the cauldron. By indirectly contacting the cauldron through this circuitous route, the problem of lower temperatures at the point of direct gas contact and a larger temperature distribution within the cauldron is reduced. Therefore, for the synthesis reaction of halide solid electrolytes involving halogenation reactions and solid-phase reactions of oxide mixtures, the uneven distribution of the proceeding state (i.e., deviations in the proceeding state) can be suppressed.

[0062] Preferably, the gas inlet is located on the bottom side of the furnace, and the exhaust port is located on the top side (e.g., the top side of the ceiling or the top side wall). This allows the reaction gases to be smoothly discharged from the furnace through convection (from bottom to top) within the furnace, thus reducing the amount of unwanted residual components mixed into the halide solid electrolyte.

[0063] Alternatively, the introduced gas can be heated before being introduced into the furnace. This suppresses uneven temperature distribution within the furnace. Consequently, the synthesis reaction of the halide solid electrolyte proceeds more uniformly, resulting in a more homogeneous halide solid electrolyte.

[0064] As described above, the heat treatment temperature is, for example, 150°C or higher and 600°C or lower, or 250°C or higher and 550°C or lower. As described above, the heat treatment time is, for example, 1 hour or higher and 40 hours or lower. The heat treatment temperature and heat treatment time can be arbitrarily determined taking into account the temperature required for the synthesis of the halide solid electrolyte, the synthesis time required, and the time for the release of reaction gases, etc.

[0065] The furnace used in heat treatment can be a known firing furnace (e.g., an electric furnace) or an atmosphere firing furnace. It should be noted that, in order to completely replace the atmospheric and moisture content deep within the firing pan with an inert gas, an inert gas can be circulated after vacuum replacement. This reduces the influence of reactive components and moisture contained in the atmosphere. Vacuum replacement can be repeated.

[0066] The temperature distribution within the firing pan during heat treatment can be within the temperature distribution range of a commonly used firing furnace, for example, within 30°C. Furthermore, the temperature distribution within the firing pan referred to here is the difference between the highest and lowest temperatures within the firing pan.

[0067] Furthermore, since the heat treatment is not intended to react easily evaporating materials such as titanium halides, a closed-loop heat treatment is not required. The oxide mixture and the halogen-containing mixture can be placed in a cauldron, and a lid (e.g., an alumina lid) can be placed to prevent debris and foreign matter from falling in, and then the heat treatment can be performed. Therefore, unlike conventional manufacturing methods using halides as raw materials where the throughput is limited by size (i.e., heat treatment for causing a solid-phase reaction of the halide raw materials) in closed-loop heat treatment fixtures, the heat treatment in the manufacturing method of the first embodiment has extremely high productivity and workability, and its industrial applicability is extremely high. According to the manufacturing method of the first embodiment, a halide solid electrolyte with excellent ionic conductivity and stability (e.g., electrochemical stability and heat resistance) can be obtained through such a highly productive manufacturing method. Additionally, if the oxide mixture contains trace amounts of titanium oxide as impurities, trace amounts of titanium halides (e.g., TiF4) may be generated. However, by performing heat treatment in an open atmosphere, these trace amounts of titanium halides will evaporate and disappear. Therefore, even under such circumstances, it is possible to obtain halide solid electrolytes that do not contain titanium halides and have excellent properties and reliability.

[0068] Furthermore, the material of the beaker does not have to be alumina. Besides alumina, heat-resistant containers made of various dense materials (e.g., relative density of 98% or higher), such as mullite and SiC, can also be used. From the perspective of the reaction between the oxide mixture contained in the beaker, halogenated substances, and halide solid electrolytes, a suitable material can be selected for the beaker. In addition to the materials mentioned above, dense materials with heat resistance and low heat capacity can also be used as the beaker material. The shape of the beaker can be various, such as cylindrical, prismatic, or gourd-shaped.

[0069] Furthermore, examples of using a firing pan in heat treatment are given here, but it is not limited to this. For example, a rotary kiln or other rotary furnace can be used, or the mixed powder can be heat-treated by spraying, such as in spray drying.

[0070] It should be noted that, as an example of the manufacturing method of the first embodiment, the methods described in (A-1) and (A-2) above have been explained in detail. However, the step of uniformly mixing the oxide mixture and the halogen-containing substance before halogenation treatment may not be necessary. For example, the halogen-containing substance may be added to the oxide mixture, and heat treatment may be performed without sufficient mixing. In addition, for effective halogenation treatment, heat treatment is preferred. For example, the oxide mixture may be halogenated by adding the halogen-containing substance and then leaving it at room temperature for an extended period of time.

[0071] In the manufacturing method of the first embodiment, additives can be added to the oxide mixture as needed before the halogenation treatment. For example, additives that promote the halogenation reaction of the oxide mixture or additives that promote the solid-phase reaction of the oxide mixture can be added. Examples of such additives include oxides containing at least one element selected from Nb, Ga, Zn, Mg, P, K, Na, Ca, Fe, Si, and Cu. For example, when trace amounts of Nb oxide and Ga oxide are added to the oxide mixture, the reaction temperature of the halogenation reaction and the solid-phase reaction can be lowered by, for example, about 10°C to 30°C. This promotes the halogenation reaction and the solid-phase reaction of the oxide mixture. Nb oxide and Ga oxide can be added together or only one of them can be added. The amount of additive added is not particularly limited, as long as it is appropriately selected according to the added compound and its purpose. For example, when Nb oxide and Ga oxide are added for the purpose of promoting the halogenation reaction and the solid-phase reaction, the total amount of Nb oxide and Ga oxide added relative to the oxide mixture can be, for example, 0.001 mol% or more and 0.3 mol% or less.

[0072] Additives such as Nb oxides and Ga oxides can be in particulate form. The effect of an additive can vary depending on its particle morphology and dispersion relative to the oxide mixture. Generally, for Nb oxides and Ga oxides, smaller particle sizes result in greater reaction-promoting effects. For example, the particle size of the additive can be smaller than the particles of the oxides constituting the oxide mixture. As an example, the additive can have a particle size of 0.1 μm or less and a BET of 100 μm. 2 Fine particles of g or higher. It should be noted that when Nb oxide and Ga oxide are used in large particles or added in excess, sometimes excess precipitated phases other than the solid electrolyte are generated, reducing ionic conductivity. Therefore, it is preferable to adjust the particle size and addition amount to an appropriate level. For example, Nb oxide and Ga oxide are preferably set to a particle size and addition amount at which Nb and Ga are not detected as a composite phase in the X-ray diffraction analysis of the final halide solid electrolyte. This allows for the synthesis of a halide solid electrolyte with high ionic conductivity while achieving a reaction-promoting effect.

[0073] The halide solid electrolyte obtained by the manufacturing method of the first embodiment is a solid electrolyte containing Li, Ti, M and X. When M contains Al and X contains F, the obtained halide solid electrolyte may, for example, contain a first crystalline phase represented by the following composition formula (1) and a second crystalline phase represented by the following composition formula (2).

[0074] Composition formula (1): Li2TiX6 Composition formula (2): Li3MX6 In the manufacture of halide solid electrolytes comprising a first crystalline phase and a second crystalline phase, for example, Li₂TiO₃, which is stable in an atmospheric environment, can be used as a composite oxide containing Li and Ti. Therefore, TiO₂ can be omitted as the Ti source. Consequently, the formation of titanium halide is suppressed during the conversion of the oxide mixture to a halide. Thus, it is possible to synthesize halide solid electrolytes with good characteristics such as stability in an atmospheric environment, good reproducibility, and suppressed compositional variations. In other words, the halide solid electrolyte obtained by the manufacturing method of the first embodiment can have the target composition, thus enabling the realization of halide solid electrolytes with excellent ionic conductivity. Furthermore, since the formation of titanium halide is suppressed, synthesis using a closed fixture (e.g., solid-phase synthesis using a planetary ball mill or a closed heat-resistant container) is not required. Therefore, synthesis with excellent productivity is possible.

[0075] When the halide solid electrolyte obtained by the manufacturing method of the first embodiment contains a first crystal phase and a second crystal phase, the halide solid electrolyte can be represented by the following composition formula (3).

[0076] Composition formula (3): xLi2TiX6-(1-x)Li3MX6 In the composition formula (3), x satisfies 0 < x < 1. That is, x represents the composition ratio of Li2TiX6 as the first crystal phase, and (1-x) represents the composition ratio of Li3MX6 as the second crystal phase. In order to improve ionic conductivity, x can satisfy 0.05 ≤ x ≤ 0.5, for example.

[0077] In the manufacturing method of the first embodiment, when at least one selected from Nb oxide and Ga oxide is used as an additive, the obtained halide solid electrolyte contains at least one selected from Nb and Ga. That is, in this case, the halide solid electrolyte obtained by the manufacturing method of the first embodiment contains Li, Ti, Al, and F, and also contains at least one selected from Nb and Ga. With this configuration, a homogeneous halide solid electrolyte with excellent ionic conductivity can be obtained. The halide solid electrolyte obtained by the manufacturing method of the first embodiment can be substantially composed of Li, Ti, Al, F, Nb, and Ga, or can be composed only of Li, Ti, Al, F, Nb, and Ga. "The halide solid electrolyte is substantially composed of Li, Ti, Al, F, Nb, and Ga" means that the ratio of the total amount of the substances of Li, Ti, Al, F, Nb, and Ga to the total amount of the substances of all the elements constituting the halide solid electrolyte is 90% or more. As an example, this ratio can be 95% or more.

[0078] The amount of oxygen as an impurity in the halide solid electrolyte obtained by the manufacturing method of the first embodiment can be 0.5 mass% or less. According to the manufacturing method of the first embodiment, a halide solid electrolyte with less oxygen incorporation can be obtained. The amount of oxygen as an impurity in the halide solid electrolyte can be 0.1 mass% or more, for example.

[0079] As described above, when Nb oxide and Ga oxide are added as additives for promoting the reaction of the oxide mixture, in X-ray diffraction measurement, Nb and Ga are sometimes not detected in the form of a composition phase. In this case, the presence of Nb and Ga in the halide solid electrolyte can also be confirmed by highly sensitive composition analysis (such as surface analysis) using an electron probe microanalyzer (EPMA). The total content ratio of Nb and Ga contained in the halide solid electrolyte can be 0.0003 atomic% or more and 0.15 atomic% or less, for example. The content ratios of Nb and Ga can be determined by EPMA or the like.

[0080] In the case where the halide solid electrolyte obtained by the manufacturing method of the first embodiment contains the aforementioned first crystalline phase and the aforementioned second crystalline phase, and further contains at least one of Nb and Ga selected from Nb oxide and Ga oxide used as additives, for example, Nb can be mainly introduced into the first crystalline phase, i.e., Li₂TiX₆, and Ga can be mainly introduced into the second crystalline phase, i.e., Li₃MX₆. That is, it is considered that Nb mainly plays a reaction-promoting role in the synthesis reaction of Li₂TiX₆, while Ga mainly plays a reaction-promoting role in Li₃MX₆. Therefore, when the halide solid electrolyte to be manufactured is a solid electrolyte containing the first crystalline phase and the second crystalline phase, it is preferable to simultaneously add Nb oxide and Ga oxide.

[0081] The halide solid electrolyte obtained by the manufacturing method of the first embodiment can achieve the same level of high ionic conductivity as solid electrolytes manufactured using halide raw materials.

[0082] The halide solid electrolyte obtained by the manufacturing method of the first embodiment preferably does not substantially contain TiF4. With this configuration, the changes in the properties and mechanical properties of the halide solid electrolyte over time due to the evaporation and deliquescence of TiF4 can be suppressed, thus enabling the realization of a halide solid electrolyte with excellent properties and reliability. Here, "the halide solid electrolyte does not substantially contain TiF4" means that the proportion of TiF4 in the solid electrolyte is, for example, 0.5% by mass or less, preferably 0.1% by mass or less. It should be noted that regarding the proportion of TiF4 in the halide solid electrolyte, for example, compositional analysis can be performed by elemental analysis based on energy dispersive X-ray spectrometry (EDS) or electron probe microanalysis (EPMA) on the cross-section of the pressed powder of the halide solid electrolyte or the particle surface of the solid electrolyte, and the proportion can be determined based on the area ratio of the detected TiF4 portion. It should be noted that when the oxide mixture used as the raw material for the halide solid electrolyte contains trace amounts of titanium oxide (TiO2), trace amounts of TiF4 may sometimes be generated during the halogenation process. However, even under these circumstances, TiF4 can be evaporated and eliminated by openly performing halogenation. Therefore, a halide solid electrolyte with excellent reliability and properties that substantially do not contain TiF4 can be obtained.

[0083] Regarding the halide solid electrolyte obtained by the manufacturing method of the first embodiment, for example, in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the above-mentioned halide solid electrolyte using Cu-Kα rays, it is preferable to satisfy at least one of (1), (2) and (3) below.

[0084] (1) There are no peaks originating from TiF4.

[0085] (2) There are no peaks originating from LiF.

[0086] (3) There are no peaks originating from AlF3.

[0087] Based on the above configuration, the halide solid electrolyte obtained by the manufacturing method of the first embodiment does not substantially contain compounds such as TiF4, LiF and / or AlF3, and therefore has excellent properties and reliability.

[0088] In this specification, a peak in an X-ray diffraction pattern is defined as a mountain-shaped portion with an S / N ratio (i.e., the ratio of signal S to background noise N) of 1.3 or higher and a half-width of 5° or less. Therefore, the absence of a peak refers to a mountain-shaped portion that has not been identified as a peak as described above.

[0089] For example, if the halide solid electrolyte obtained by the manufacturing method of the first embodiment satisfies the above-mentioned (1) configuration, that is, if there is no peak originating from TiF4 in the X-ray diffraction pattern, for example, there is no peak in the range of diffraction angle 2θ of 24° or more and 25° or less.

[0090] The halide solid electrolyte obtained by the manufacturing method of the first embodiment can be in particle form. Halide solid electrolytes have relatively soft properties. Therefore, based on this configuration, a relatively soft particle-shaped solid electrolyte can be achieved. Consequently, the pressed powder of such a halide solid electrolyte exhibits high ionic conductivity, excellent stability, and can be produced in any shape. Therefore, the pressed powder of a halide solid electrolyte with these characteristics can realize a solid electrolyte layer for a battery with excellent properties and high reliability. It should be noted that the size and shape of the halide solid electrolyte particles can be appropriately selected according to the application.

[0091] When comparing the manufacturing method of the first embodiment with the manufacturing methods described in Patent Document 1 and Patent Document 2, the following differences exist.

[0092] Patent Document 1 discloses a solid electrolyte comprising a halide system containing Li, Ti, M, and F. It should be noted that "M" in the solid electrolyte described in Patent Document 1 is at least one selected from Al and Y. As the starting material for manufacturing this solid electrolyte, oxides such as composite oxides are not used; fluorides are used exclusively, specifically TiF4. Fluorides are mostly unstable; as mentioned above, titanium fluoride (TiF4) in particular is prone to evaporation even at relatively low temperatures (e.g., 50°C to 100°C) and also tends to contain moisture. Therefore, to suppress compositional variations and deterioration of the fluoride raw materials, a closed ball milling process in an argon atmosphere with a low dew point (e.g., below -60°C) is described. In contrast, the method for manufacturing the halide solid electrolyte in the first embodiment differs in terms of synthesizing the halide solid electrolyte from oxide raw materials with high environmental stability and the reaction pathway. In particular, by using a composite oxide as the Ti source, a reaction pathway that suppresses the formation of titanium fluoride can be selected, thus eliminating the problem of compositional variations leading to evaporation and moisture absorption of the unstable Ti component. Therefore, the manufacturing method of the first embodiment is a method for manufacturing halide solid electrolytes with excellent properties that can be synthesized in mass production. Thus, it can be seen that, unlike the manufacturing method of the first embodiment, the solid electrolyte manufacturing method of Patent Document 1 has problems in terms of Ti evaporation, atmospheric synthesis, and production.

[0093] Patent Document 2 discloses a method for manufacturing a halide solid electrolyte comprising Li, Ti, M1, and F as a cathode material. It should be noted that "M1" in the solid electrolyte described in Patent Document 2 is at least one selected from Ca, Mg, Al, Y, and Zr. However, similar to the manufacturing method described in Patent Document 1, fluorides such as TiF4 are used as starting materials. Therefore, it is considered that the manufacturing method described in Patent Document 1 also suffers from issues such as compositional deviations in the synthesis process. In contrast, the manufacturing method of the first embodiment, as described above, is a method for manufacturing a halide solid electrolyte with excellent properties that can be synthesized in mass production.

[0094] As described above, the manufacturing method of the first embodiment uses an oxide that is stable to the environment (temperature and humidity) as a starting material, and it does not require the synthesis of unstable titanium fluoride or the like during the reaction process. Therefore, the manufacturing method of the first embodiment is superior to the manufacturing methods described in Patent Documents 1 and 2 in terms of obtaining a halide solid electrolyte with excellent properties by suppressing compositional variations and having excellent mass production capabilities.

[0095] [Second Implementation] The method for manufacturing the halide solid electrolyte in the second embodiment will be described below.

[0096] The manufacturing method of the second embodiment, after step (A) of the manufacturing method of the first embodiment, further includes: (B) pulverizing the halide solid electrolyte obtained in step (A).

[0097] According to the manufacturing method of the second embodiment, by performing the pulverization process described in (B) above, a halide solid electrolyte with excellent ionic conductivity and reliability can be obtained at a particle size suitable for its application. Furthermore, since at least a portion of the halide solid electrolyte can be amorphized, ionic conductivity and the softness of the halide solid electrolyte particles can be improved. By increasing the softness of the halide solid electrolyte particles, the density of the pressed halide solid electrolyte powder can be increased. Therefore, the halide solid electrolyte obtained by the manufacturing method of the second embodiment can form a dense pressed powder with high ionic conductivity.

[0098] Figure 2 This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the second embodiment. Specifically, an example of the manufacturing method described in the first embodiment will be described, namely, an example in which the manufacturing method described above (A-1) and above (A-2) are performed as described in (A), and the manufacturing method described above (B) is performed after (A-2).

[0099] like Figure 2 As shown, firstly, the oxide mixture and the halogen-containing substance are mixed (S21). Next, the oxide mixture is subjected to halogenation treatment by heat treatment (S22). This yields a halide solid electrolyte containing Li, Ti, M, and X. Then, as a step equivalent to (B) above, the halide solid electrolyte obtained in S22 is subjected to pulverization treatment (S23).

[0100] S21 and S22 are the same as S11 and S12 described in the first embodiment, so detailed descriptions are omitted here.

[0101] The halide solid electrolyte synthesized by (A) above has an average particle size of, for example, 3 μm or more and about 20 μm or less. In (B) above, such halide solid electrolyte synthesized by (A) above is subjected to a pulverization process so that, for example, the average particle size becomes 0.1 μm or more and about 2 μm or less.

[0102] The pulverization process only needs to be able to finely break down the halide into the desired particle size. It can be dry or wet, using water or a solvent (e.g., ethanol, butyl acetate, etc.). For example, zirconium oxide balls (e.g., balls with a diameter of 1 mm to 30 mm) and the halide solid electrolyte obtained in (A) above are placed in a ball mill container, and pulverization is carried out for, for example, about 3 to 40 hours. The ball mill container can be, for example, a container made of polyethylene, or a container lined with fluororesin or zirconium oxide.

[0103] The pulverization process described in (B) above may include, for example, mechanochemical treatment. This mechanochemical treatment is performed to introduce deformed crystals or amorphous material into the halide solid electrolyte. The deformed crystals or amorphous material are primarily introduced into the surface layer of the halide solid electrolyte particles. Specific methods can be the same as the pulverization process described above, such as using a ball mill. However, pulverization conditions can be intensified or the time extended. The apparatus and media used for mechanochemical treatment can be the same as those used for pulverization; generally, pulverization and mechanochemical treatment are performed simultaneously. As an example, in a dry process, a ball mill container lined with zirconia is used, and zirconia balls are placed in a volume ratio of 10% to 60%, and mechanochemical grinding is performed simultaneously with pulverization. The diameter of the zirconia balls is not particularly limited, and any size can be used. Typically, as mentioned above, commercially available balls with diameters of 1 mm to 30 mm are used; smaller or larger diameters are also possible. The diameter of the balls used can be arbitrarily selected depending on the target particle size or the degree of amorphization. In addition, to prevent halide solid electrolytes from adhering to the inner wall of zirconia spheres or zirconia containers, an appropriate amount of additives such as ethanol that do not adversely affect the properties of the halide solid electrolytes can be added. Preferably, the additives are those that can be removed by subsequent drying.

[0104] The introduction of amorphous properties into halide solid electrolytes can be confirmed by X-ray diffraction (XRD) patterns. XRD patterns can be determined using Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å) as the X-ray source via the θ-2θ method. Specifically, this can be confirmed by the expansion of peaks in the XRD pattern of the pulverized halide solid electrolyte compared to the unpulverized version. Peak expansion refers to the broadening of the peaks and the increase in the half-width at half-maximum (WWHM).

[0105] The presence of deformed crystals, i.e., regions of disordered crystallization, in halide solid electrolytes can be observed using transmission electron microscopy (TEM) in the form of images formed by regions with high regularity of the lattice pattern and regions with disordered lattice patterns.

[0106] In addition, changes in deformability caused by amorphization can be evaluated using methods such as microVickers hardness.

[0107] As described above, the manufacturing method of the second embodiment includes a pulverization process, therefore the halide solid electrolyte obtained by the manufacturing method of the second embodiment contains, for example, an amorphous phase. According to this configuration, the amorphous portion of the halide solid electrolyte becomes softer and exhibits superior deformability. Therefore, the pressed powder of the halide solid electrolyte can be formed into a solid electrolyte layer with higher ionic conductivity and higher stability in any shape. Thus, the pressed powder of the halide solid electrolyte containing the amorphous phase can realize a solid electrolyte layer for a battery with excellent characteristics and high reliability.

[0108] As a variation of the manufacturing method of the second embodiment, during the pulverization process described in (B) above, the halide solid electrolyte can be slurried simultaneously with the pulverization process to form a coating film.

[0109] Figure 3 This is a flowchart illustrating a variation of the manufacturing method of the halide solid electrolyte according to the second embodiment. Regarding the variation of the manufacturing method of the second embodiment, an example of the manufacturing method described in the first embodiment will also be described here, namely, an example in which the manufacturing method described above (A-2) is performed after the manufacturing method described above (A-2) in the manufacturing method described above (A-1) and above (A-2).

[0110] like Figure 3 As shown, firstly, the oxide mixture and the halogen-containing substance are mixed (S31). Next, the oxide mixture is subjected to halogenation treatment by heat treatment (S32). This yields a halide solid electrolyte containing Li, Ti, M, and X. Then, as a step equivalent to (B) above, the halide solid electrolyte obtained in S32 is subjected to pulverization treatment, and simultaneously to slurry treatment (S33).

[0111] S31 and S32 are the same as S11 and S12 described in the first embodiment, so detailed descriptions are omitted here.

[0112] In S33, the pulverization process is the same as the pulverization process in S23, which is described as an example of the manufacturing method of the second embodiment. In a variation of the manufacturing method of the second embodiment, a slurry-forming process is further performed. The slurry-forming process is performed, for example, by adding a halide solid electrolyte while pulverizing, with the organic binder and plasticizer dispersedly contained in an organic solvent such as tetrahydronaphthalene. Examples of organic binders include styrene-butadiene block copolymer (SBS). Examples of plasticizers include dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP).

[0113] The obtained halide solid electrolyte slurry can be used for printing or coating. The thickness of the coating film can be, for example, 10 μm or more and 100 μm or less, thus, for example, it is possible to directly coat such a halide solid electrolyte slurry containing amorphous portions after it has been pulverized. In this way, organic binders and plasticizers can be added during the pulverization process to prepare the halide solid electrolyte slurry, and the coating film can be formed using the slurry. As a result, a halide solid electrolyte coating film with excellent properties can be formed. Such a coating film can be used, for example, in the manufacture of coated batteries.

[0114] [Third Implementation Method] The method for manufacturing the halide solid electrolyte in the third embodiment will be described below.

[0115] The manufacturing method of the third embodiment involves generating halogen gas by heat-treating a halogen-containing substance as described in (A) of the first embodiment, and then contacting the halogen gas with an oxide mixture to perform halogenation treatment on the oxide mixture. In the manufacturing method of the third embodiment, the pulverization process described in (B) of the second embodiment can be performed after (A).

[0116] Figure 4 This is a flowchart illustrating an example of a method for manufacturing a halide solid electrolyte according to the third embodiment. For example... Figure 4 As shown, an oxide mixture is prepared by mixing a composite oxide containing Li and Ti with an oxide raw material containing Li and M (S41). Next, the oxide mixture and a halogen-containing substance are positioned at a predetermined location, and the halogen-containing substance is heat-treated to bring the generated halogen gas into contact with the oxide mixture (S42). This performs a halogenation treatment on the oxide mixture. Then, as a step equivalent to (B) above, the halide solid electrolyte obtained in S42 can be pulverized (S43).

[0117] According to the manufacturing method of the third embodiment, the oxide mixture can be halogenated using the generated halogen gas without directly contacting the oxide mixture with the halogen-containing substance. Therefore, even if a halogen-containing substance containing inorganic components other than halogen elements (such as CuF2, a substance that releases fluorine gas upon heating) is used, inorganic residues in the manufactured halide solid electrolyte can be disregarded. Thus, the range of usable halogen-containing substances can be expanded.

[0118] As a specific example, an oxide mixture is placed on, for example, a fine-mesh nickel mesh, and a halogen-containing substance such as ammonium fluoride is placed below the nickel mesh. This operation ensures that the oxide mixture and the halogen-containing substance are not in contact with each other. In this state, by heat-treating the halogen-containing substance, a halogen gas such as fluorine is generated, which passes through the nickel mesh and comes into contact with the oxide mixture. Thus, the oxide mixture is converted into a halide. The oxide mixture and the halogen-containing substance are as described in the first embodiment. It should be noted that the heat treatment can also be performed in the atmosphere, but to prevent oxidation of the nickel mesh, heat treatment in a nitrogen atmosphere or a reducing atmosphere is preferred.

[0119] [Fourth Implementation Method] The fourth embodiment will now be described. Items described in the first, second, and third embodiments will be omitted as appropriate.

[0120] The battery of 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.

[0121] The solid electrolyte comprises at least one halide selected from the positive electrode, electrolyte layer, and negative electrode, wherein the solid halide comprises Li, Ti, Al, and F, and further comprises at least one selected from Nb and Ga. This solid halide electrolyte can be manufactured, for example, by the manufacturing methods of the first, second, or third embodiment.

[0122] Hereinafter, the halide solid electrolyte comprising Li, Ti, Al and F and further comprising at least one selected from Nb and Ga in the battery of the fourth embodiment will be described as the halide solid electrolyte of the fourth embodiment.

[0123] The halide solid electrolyte of the fourth embodiment, as described in the first, second, or third embodiment as an example of a halide solid electrolyte that can be manufactured by the manufacturing methods of the first, second, or third embodiment, may be substantially composed of Li, Ti, Al, F, Nb, and Ga, or may be composed of only Li, Ti, Al, F, Nb, and Ga. The halide solid electrolyte of the fourth embodiment may be in particulate form. Furthermore, as described in the second embodiment, the halide solid electrolyte of the fourth embodiment may contain an amorphous phase.

[0124] The battery of the fourth embodiment has excellent charge and discharge characteristics because it contains the halide solid electrolyte of the fourth embodiment.

[0125] Figure 5 A cross-sectional view showing the battery 1000 according to the fourth embodiment.

[0126] The battery 1000 of the fourth embodiment includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0127] The positive electrode 201 may contain a positive electrode material containing the halide electrolyte of the fourth embodiment. The positive electrode 201 contains a positive electrode active material 204 and a solid electrolyte 100.

[0128] Electrolyte layer 202 contains electrolyte material.

[0129] The negative electrode 203 contains negative electrode active material 205 and solid electrolyte 100.

[0130] Solid electrolyte 100 may include, for example, the halide solid electrolyte of the fourth embodiment. Solid electrolyte 100 may be particles containing the halide solid electrolyte of the fourth embodiment as a main component. Particles containing the halide solid electrolyte of the fourth embodiment as a main component refer to particles whose most abundant component, in molar ratio, is the halide solid electrolyte of the fourth embodiment. Solid electrolyte 100 may be particles formed from the halide solid electrolyte of the fourth embodiment.

[0131] The positive electrode 201 contains a material capable of inserting and deintercalating metal ions (e.g., lithium ions). This material is, for example, positive electrode active material 204.

[0132] Examples of positive electrode active material 204 include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, transition metal sulfides, transition metal fluorides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni, Co, Mn)O2, Li(Ni, Co, Al)O2, or LiCoO2.

[0133] In this disclosure, “(A, B, C)” means “at least one selected from A, B and C”.

[0134] The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 can be particles. The positive electrode active material 204 can have a median particle size of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median particle size 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. As a result, the charge and discharge characteristics of the battery 1000 are improved. When the positive electrode active material 204 has a median particle size of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 is increased. As a result, the battery 1000 can operate at high output.

[0135] The positive electrode active material 204 can have a larger median particle size than the solid electrolyte 100. Therefore, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201.

[0136] 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 total volume of the positive electrode active material 204 and the solid electrolyte 100 can be 0.30 or more and 0.95 or less.

[0137] A coating layer can be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer can be formed on the surface of the positive electrode active material 204, for example, before being mixed with a conductive additive and a binder. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes. When the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material can contain a halide solid electrolyte according to the fourth embodiment to suppress the 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 can contain an oxide solid electrolyte to suppress the oxidative decomposition of the solid electrolyte. Lithium niobate, which has excellent stability at high potentials, can be used as the oxide solid electrolyte. By suppressing oxidative decomposition, the overvoltage rise of the battery 1000 can be suppressed.

[0138] As described above, when the positive electrode 201 contains a positive electrode material containing a halide solid electrolyte of the fourth embodiment, the positive electrode material may contain the halide solid electrolyte of the fourth embodiment as a solid electrolyte 100, or it may contain it as a coating material for the coated positive electrode active material 204.

[0139] To improve the energy density and output of the battery 1000, the positive electrode 201 can have a thickness of more than 10 μm and less than 500 μm.

[0140] Electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte. The solid electrolyte may include the halide solid electrolyte of the fourth embodiment. Electrolyte layer 202 may be a solid electrolyte layer.

[0141] Electrolyte layer 202 may contain 50% by mass or more of the halide solid electrolyte of the fourth embodiment. Electrolyte layer 202 may contain 70% by mass or more of the halide solid electrolyte of the fourth embodiment. Electrolyte layer 202 may contain 90% by mass or more of the halide solid electrolyte of the fourth embodiment. Electrolyte layer 202 may be composed solely of the halide solid electrolyte of the fourth embodiment.

[0142] Hereinafter, the halide solid electrolyte of the fourth embodiment will be referred to as the first solid electrolyte. Solid electrolytes different from the first solid electrolyte will be referred to as the second solid electrolyte.

[0143] The electrolyte layer 202 may contain not only a first solid electrolyte but also a second solid electrolyte. The first and second solid electrolytes can be uniformly dispersed within the electrolyte layer 202. The layers composed of the first solid electrolyte and the layers composed of the second solid electrolyte can be stacked along the stacking direction of the battery 1000.

[0144] The battery of the fourth embodiment may sequentially include a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203. 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. Therefore, the solid electrolyte contained in the second electrolyte layer can be used without reduction. As a result, the charge / discharge efficiency of the battery 1000 can be improved. For example, when the second electrolyte layer contains a first solid electrolyte, in order to suppress the reductive decomposition of this solid electrolyte, the first electrolyte layer may contain a sulfide solid electrolyte. This can improve the charge / discharge efficiency of the battery 1000. The second electrolyte layer may contain a first solid electrolyte. Since the first solid electrolyte has high oxidation resistance, a battery with excellent charge / discharge characteristics can be achieved.

[0145] The electrolyte layer 202 may also consist of only the second solid electrolyte.

[0146] The electrolyte layer 202 can have a thickness of 1 μm or more but less than 1000 μm. When the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 become less prone to short circuits. When the electrolyte layer 202 has a thickness of less than 1000 μm, the battery 1000 can operate at high output.

[0147] Examples of the second solid electrolyte are Li₂MgX₄, Li₂FeX₄, Li(Al,Ga,In)X₄, Li₃(Al,Ga,In)X₆, or LiI. Wherein, X is at least one selected from F, Cl, Br, and I.

[0148] To improve the energy density and output of the battery 1000, the electrolyte layer 202 can have a thickness of more than 1 μm and less than 1000 μm.

[0149] The negative electrode 203 contains a material capable of inserting and deintercalating metal ions (e.g., lithium ions). This material is, for example, the negative electrode active material 205.

[0150] Examples of negative electrode active materials 205 include metallic materials, carbon materials, oxides, nitrides, tin compounds, and silicon compounds. Metallic materials can be elemental metals or alloys. Examples of metallic materials include lithium metal or lithium alloys. Examples of carbon materials include natural graphite, coke, graphitized carbon, carbon fibers, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of negative electrode active materials are silicon (i.e., Si), tin (i.e., Sn), silicon compounds, or tin compounds.

[0151] The negative electrode active material 205 can be selected considering the reduction resistance of the solid electrolyte contained in the negative electrode 203. For example, if the negative electrode 203 contains a first solid electrolyte, the negative electrode active material 205 can be a material capable of inserting and deintercalating lithium ions at a voltage greater than 0.27V relative to lithium. Examples of such negative electrode active materials are titanium oxides, indium metal, or lithium alloys. An example of titanium oxide is Li4Ti5O. 12 LiTi₂O₄ or TiO₂. By using the above-mentioned negative electrode active material, the reduction and decomposition of the first solid electrolyte contained in the negative electrode 203 can be suppressed. As a result, the charge and discharge efficiency of the battery 1000 can be improved.

[0152] The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 can be particles. The negative electrode active material 205 can have a median particle size of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median particle size 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. As a result, the charge and discharge characteristics of the battery 1000 are improved. When the negative electrode active material 205 has a median particle size of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 is increased. As a result, the battery 1000 can operate at high output.

[0153] The negative electrode active material 205 can have a larger median particle size than the solid electrolyte 100. Therefore, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203.

[0154] 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 total volume of the negative electrode active material 205 and the solid electrolyte 100 can be greater than 0.30 and less than 0.95.

[0155] To improve the energy density and output of the battery 1000, the negative electrode 203 can have a thickness of more than 10 μm and less than 500 μm.

[0156] For the purpose of improving ionic conductivity, chemical stability and electrochemical stability, at least one of the cathode 201, electrolyte layer 202 and anode 203 may contain a second solid electrolyte.

[0157] The second solid electrolyte can be a sulfide solid electrolyte.

[0158] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, and Li₂S-P₂S₅. 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 .

[0159] When the electrolyte layer 202 contains a first solid electrolyte, the negative electrode 203 may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte. By covering the negative electrode active material with an electrochemically stable sulfide solid electrolyte, contact between the first solid electrolyte and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery 1000 can be reduced.

[0160] The second solid electrolyte can be an oxide solid electrolyte.

[0161] Examples of oxide solid electrolytes are: (i) Sodium superionic conductor (NASICON) type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutes; (ii)Perovskite-type solid electrolytes such as (LaLi)TiO3; (iii)Li 14 ZnGe4O 16 NASICON-type solid electrolytes such as Li4SiO4, LiGeO4, or their elemental substitutions; (iv)Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those containing elemental substitutions; or (v)Li3PO4 or its N-substituted derivatives.

[0162] As mentioned above, the second solid electrolyte can be a halide solid electrolyte.

[0163] Examples of halide solid electrolytes are Li₂MgX₄, Li₂FeX₄, Li(Al,Ga,In)X₄, Li₃(Al,Ga,In)X₆, or LiI. Wherein, X is at least one selected from F, Cl, Br, and I.

[0164] Another example of a halide solid electrolyte is Li a Me b Y c Z6 represents the compound. Here, a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one of the metallic elements and metalloids selected from those other than Li and Y. Z is at least one of F, Cl, Br, and I. m represents the valence of Me. "Metalloids" refers to B, Si, Ge, As, Sb, and Te. "Metallic elements" refers to all elements contained in Groups 1 to 12 of the periodic table (except hydrogen) and all elements contained in Groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0165] To improve the ionic conductivity of halide solid electrolytes, Me can be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0166] The halide solid electrolyte can be Li3YCl6 or Li3YBr6.

[0167] The second solid electrolyte can be an organic polymer solid electrolyte.

[0168] Examples of organic polymer solid electrolytes are compounds of polymers and lithium salts.

[0169] Polymers can possess an ethylene oxide structure. Polymers with an ethylene oxide structure can contain a large amount of lithium salt, thus further improving ionic conductivity.

[0170] Examples of lithium salts are LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3F3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these can be used alone. Alternatively, a mixture of two or more lithium salts selected from these can be used.

[0171] In order to facilitate the acceptance and donation of lithium ions and improve the output characteristics of the battery, at least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte or an ionic liquid.

[0172] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0173] Examples of non-aqueous solvents include cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, and fluorinated solvents. Examples of cyclic carbonate solvents include ethylene carbonate, propylene carbonate, or butyl carbonate. Examples of chain carbonate solvents include dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of chain ether solvents include 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, ethyl fluorocarbonate, or dimethyl fluorocarbonate. One of these non-aqueous solvents may be used alone. Alternatively, a combination of two or more of these non-aqueous solvents may be used.

[0174] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these can be used alone. Alternatively, a mixture of two or more lithium salts selected from these can be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0175] As a gel electrolyte, a polymeric material impregnated with a non-aqueous electrolyte can be used. Examples of polymeric materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers containing ethylene oxide bonds.

[0176] Examples of cations contained in ionic liquids are: (i) Aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) Aliphatic cyclic ammonium compounds such as pyrrolidinemonium, morpholinium, imidazolinemonium, tetrahydropyrimidinemonium, piperazinemonium, or piperidinemonium; or (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazoline.

[0177] An example of anion contained in ionic liquids is PF6. - BF4 - SbF6 - AsF6 - SO3CF3 - N(SO2CF3)2 - N(SO2C2F5)2 - N(SO2CF3)(SO2C4F9) - Or C(SO2CF3)3 - .

[0178] Ionic liquids can contain lithium salts.

[0179] To improve the adhesion between particles, at least one of the positive electrode 201, electrolyte layer 202 and negative electrode 203 may contain a binder.

[0180] Examples of adhesives include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, or carboxymethyl cellulose. Copolymers can also be used as adhesives. Examples of such adhesives are copolymers selected from two or more materials chosen from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ethers, vinylidene fluoride, trifluorochloroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures selected from two or more of these materials can be used as adhesives.

[0181] To improve electronic conductivity, at least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive.

[0182] Examples of conductive additives are: (i) Graphite, such as natural or artificial graphite; (ii) Carbon blacks such as acetylene black or Ketjen black; (iii) Conductive fibers such as carbon fiber or metal fiber; (iv) Fluorinated carbon; (v) Powdered metals such as aluminum; (vi) Conductive whiskers such as zinc oxide or potassium titanate; (vii) Conductive metal oxides such as titanium dioxide; or (viii) Conductive polymers such as polyaniline, polypyrrole or polythiophene.

[0183] To reduce costs, the conductive additives described in (i) or (ii) above can be used.

[0184] It should be noted that a separator impregnated with electrolyte can be used instead of the electrolyte layer, or the outer packaging containing the positive electrode, separator, and negative electrode can be filled with electrolyte. The electrolyte can be, for example, the non-aqueous electrolyte described above. Examples of the battery shape in the fourth embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type, or stacked type.

[0185] The battery of the fourth embodiment can be manufactured, for example, by preparing materials for forming a positive electrode, materials for forming an electrolyte layer, and materials for forming a negative electrode, and then using a known method to create a laminate in which a positive electrode, an electrolyte layer, and a negative electrode are sequentially arranged.

[0186] [Other Implementation Methods] (Postscript) The following technology has been disclosed through the above description of the embodiments.

[0187] (Technology 1) A method for manufacturing a halide solid electrolyte, comprising: (A) subjecting an oxide mixture containing a composite oxide containing Li and Ti and an oxide raw material containing Li and M to halogenation treatment, thereby obtaining a halide solid electrolyte containing Li, Ti, M and X.

[0188] Here, M is at least one element selected from metallic elements (excluding Li and Ti) and metalloid elements. X is at least one selected from F, Cl, Br and I.

[0189] Titanium halide (TiX4) is a relatively unstable substance, exhibiting characteristics such as easy evaporation and deliquescence. According to the manufacturing method of Technique 1, a composite oxide containing Li and Ti can be used as the Ti source. Therefore, according to the manufacturing method of Technique 1, in the synthesis of Ti-containing halide solid electrolytes, it is not necessary to use unstable titanium halide as a raw material as described above, and titanium halide is less likely to form during the synthesis process. In conventional manufacturing methods, titanium halide is typically used as the Ti source for synthesizing Ti-containing halide solid electrolytes. Therefore, due to the instability of titanium halide, compositional changes (i.e., compositional deviations) and deterioration (e.g., the presence of moisture) are prone to occur during the synthesis of Ti-containing halide solid electrolytes, easily altering the properties of the halide solid electrolyte. In contrast, the manufacturing method of Technique 1 can reproduce and stably synthesize Ti-containing halide solid electrolytes with excellent properties such as ionic conductivity, which are less prone to such compositional changes. That is, the manufacturing method of Technique 1 can stably synthesize halide solid electrolytes with the target composition.

[0190] (Technology 2) According to the method for manufacturing a halide solid electrolyte of technology 1, the halide solid electrolyte comprises a first crystalline phase represented by the following composition formula (1) and a second crystalline phase represented by the following composition formula (2).

[0191] Composition formula (1): Li2TiX6 Composition formula (2): Li3MX6 According to the manufacturing method of Technique 2, for example, Li₂TiO₃, which is stable in an atmospheric environment, can be used as a composite oxide containing Li and Ti. Therefore, TiO₂ can be omitted as the Ti source. Consequently, the formation of titanium halide is suppressed during the conversion of the oxide mixture to halide. Thus, it is possible to synthesize a halide solid electrolyte that is stable in an atmospheric environment and exhibits good reproducibility and properties. Furthermore, since the formation of titanium halide is suppressed, synthesis using a closed fixture (e.g., solid-phase synthesis using a planetary ball mill or a closed heat-resistant container) is not required. Therefore, synthesis with excellent productivity is possible.

[0192] (Technology 3) The method for manufacturing a halide solid electrolyte according to technique 1 or 2, wherein the oxide raw material comprises an oxide of Li and an oxide of M.

[0193] According to the manufacturing method of technology 3, it is possible to synthesize halide solid electrolytes with the target composition more stably.

[0194] (Technology 4) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 3, wherein M comprises Al.

[0195] According to the manufacturing method of Technique 4, a halide solid electrolyte with high ionic conductivity can be obtained.

[0196] (Technology 5) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 4, wherein X comprises F.

[0197] According to the manufacturing method of technique 5, a halide solid electrolyte with excellent stability (e.g., excellent electrochemical stability and heat resistance) and high ionic conductivity can be obtained.

[0198] (Technology 6) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 5, wherein the oxide mixture is in particulate form.

[0199] According to the manufacturing method of Technique 6, halogenation (i.e., substitution of halogen elements with oxygen elements) and solid-phase reactions within the oxide mixture readily occur simultaneously. Therefore, reaction residues such as oxides can be reduced in a short time, and halides can be synthesized. Consequently, a homogeneous solid electrolyte with excellent properties can be obtained. Furthermore, the particulate oxide mixture exhibits good reactivity (i.e., halogenation), thus enabling excellent productivity.

[0200] (Technology 7) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 6, wherein the oxide mixture substantially does not contain TiO2.

[0201] According to the manufacturing method of Technique 7, for example, during the conversion from an oxide mixture to a halide, it is not easy to generate titanium halides such as easily evaporating titanium tetrafluoride (TiF4). Therefore, compositional changes and deterioration are suppressed, and the desired halide solid electrolyte can be obtained.

[0202] (Technology 8) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 7, wherein, in (A), the halogenation treatment of the oxide mixture is carried out by heat treatment of a halogen-containing substance that is thermally decomposable.

[0203] According to the manufacturing method of Technology 8, halogenation and solid-phase reaction of the oxide mixture can occur simultaneously. Therefore, a homogeneous solid electrolyte with excellent properties can be obtained while reducing reaction residues such as oxides in a short time. Furthermore, by performing halogenation treatment on a thermally decomposable halogen-containing substance through heat treatment, the reactivity (halogenation property) of the oxide mixture is good, and the production rate is also excellent. Moreover, for example, the temperatures of the halogenation reaction and the solid-phase reaction of the oxide mixture, as well as the occurrence of these reactions, can be controlled according to the selected thermal decomposition temperature of the halogen-containing substance. Therefore, the desired halide solid electrolyte can be obtained.

[0204] (Technology 9) According to the method for manufacturing a halide solid electrolyte as described in Technique 8, the halogen-containing substance is in particulate form.

[0205] According to the manufacturing method of Technology 9, halogen-containing substances are prone to thermal decomposition. Therefore, according to the manufacturing method of Technology 10, the oxide mixture can be halogenated efficiently, and halogen-containing substances are less likely to remain in the final halide solid electrolyte. Furthermore, the amount of halogen can be precisely controlled. Therefore, the desired halide solid electrolyte can be synthesized. Additionally, only the amount of halogen-containing substance required for the halogenation of the oxide mixture can be used, thus suppressing the emission of excess halogen gases. Therefore, the environmental impact is reduced, and consequently, the corrosion effect on furnace materials, etc., is also reduced.

[0206] (Technology 10) The method for manufacturing a halide solid electrolyte according to technique 8 or 9, wherein step (A) comprises: (A-1) Mixing the oxide mixture with the halogen-containing substance; and (A-2) The oxide mixture is subjected to the halogenation treatment by heat treatment of the mixture containing the oxide mixture and the halogen-containing substance obtained in (A-1).

[0207] According to the manufacturing method of Technology 10, a homogeneous mixture of a mixed oxide mixture and a halogen-containing substance can be subjected to heat treatment for halogenation. Furthermore, the contact area between the oxide mixture and the halogen-containing substance can be increased. Therefore, according to the manufacturing method of Technology 10, the halogenation of the oxide mixture can be uniformly promoted. Thus, a homogeneous halide solid electrolyte with excellent properties can be obtained.

[0208] (Technology 11) According to the method for manufacturing a halide solid electrolyte of technique 8 or 9, in step (A), halogen gas is generated by heat treatment of the halogen-containing substance, and the halogen gas is brought into contact with the oxide mixture to perform the halogenation treatment on the oxide mixture.

[0209] According to the manufacturing method of Technology 11, the oxide mixture can be halogenated using the generated halogen gas without directly contacting the oxide mixture with the halogen-containing substance. Therefore, even if a halogen-containing substance containing inorganic components in addition to halogen elements is used, inorganic residues in the manufactured halide solid electrolyte can be disregarded. Thus, the range of usable halogen-containing substances can be expanded.

[0210] (Technology 12) The method for manufacturing a halide solid electrolyte according to any one of techniques 8 to 11, wherein the halogen-containing substance comprises an ammonium salt.

[0211] Ammonium salts begin thermal decomposition at relatively low temperatures (e.g., around 150°C). Therefore, ammonium salts are less likely to remain as unwanted inorganic components in the final halide solid electrolyte, and thermal decomposition at low temperatures allows for the halogenation of the oxide mixture. Thus, according to the manufacturing method of Technique 12, the presence of unwanted inorganic components from halogen-containing substances in the final halide solid electrolyte can be suppressed. Furthermore, energy efficiency in synthesis is achieved, heating and cooling times are reduced, and productivity is increased. Additionally, since synthesis can be performed at low temperatures, the durability of the furnace material is improved, and the operating costs and replacement frequency of the synthesis components are significantly reduced. It should be noted that in conventional methods for synthesizing halide solid electrolytes using halide feedstocks via solid-state reactions, heat treatment at around 500°C to 600°C is required, for example.

[0212] (Technology 13) The method for manufacturing a halide solid electrolyte according to Technique 12, wherein the ammonium salt comprises NH4F.

[0213] NH4F is a highly decomposable fluorine source that can effectively act on the halogenation of oxide mixtures. Therefore, according to the manufacturing method of Technique 13, NH4F can halogenate oxide mixtures without residue in a solid electrolyte while undergoing thermal decomposition at a low temperature (e.g., about 150°C) and a fast decomposition rate.

[0214] (Technology 14) The method for manufacturing a halide solid electrolyte according to techniques 8-13, wherein the halogen-containing substance comprises a resin.

[0215] According to the manufacturing method of Technique 14, the halogen-containing substance can undergo thermal decomposition at a relatively high temperature (e.g., above about 450°C and below 600°C) while simultaneously halogenating the oxide mixture. Therefore, the manufacturing method of Technique 14 is suitable for situations where it is desired to perform halogenation and solid-phase reactions at a relatively high temperature (e.g., above about 450°C and below 600°C).

[0216] (Technology 15) The method for manufacturing a halide solid electrolyte according to Technique 14, wherein the resin comprises a fluororesin.

[0217] Fluoropolymers such as PTFE can undergo thermal decomposition at relatively high temperatures (e.g., above about 450°C and below 600°C) while simultaneously halogenating the oxide mixture. Therefore, the manufacturing method of Technique 15 is suitable for situations where it is desirable to perform halogenation and solid-phase reactions at relatively high temperatures (e.g., above about 450°C and below 600°C).

[0218] (Technology 16) The method for manufacturing a halide solid electrolyte according to any one of techniques 8 to 11, wherein the halogen-containing substance comprises a substance that substantially does not contain inorganic components other than halogen elements produced by thermal decomposition via heat treatment in (A).

[0219] For halogen-containing substances, it is required that while the halogen element produced by thermal decomposition through heat treatment in step (A) above replaces the oxygen element in the oxide mixture, other components should not be mixed into the final halide solid electrolyte as inorganic residues. By using a substance that substantially eliminates the inorganic components other than halogen elements produced by thermal decomposition through heat treatment in the final halide solid electrolyte, it is possible to suppress the mixing of inorganic residues into the halide solid electrolyte and obtain the desired halide solid electrolyte. It should be noted that the halogen-containing substance that substantially eliminates the inorganic components other than halogen elements produced by thermal decomposition through heat treatment in the final halide solid electrolyte can be, for example, a substance whose inorganic components other than halogen elements produced by thermal decomposition through heat treatment are released as gas.

[0220] (Technology 17) The method for manufacturing a halide solid electrolyte according to any one of techniques 8 to 16, wherein the halogen-containing substance comprises a variety of halogen-containing compounds.

[0221] According to the manufacturing method of technique 17, for example, both ammonium salt and fluoropolymer can be used as halogen-containing substances. Therefore, a wider temperature range can be controlled for the halogen source to function as the halogen-containing substance. Consequently, the conversion temperature of the oxide mixture to halide and the solid-phase reaction temperature can be controlled over a wide range. Therefore, according to the manufacturing method of technique 17, the desired halide solid electrolyte can be readily obtained.

[0222] (Technology 18) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 17, wherein, in (A), the halogenation treatment of the oxide mixture is carried out at a temperature of 150°C or higher.

[0223] According to the manufacturing method of Technique 18, the oxide mixture can be fully halogenated. It should be noted that the halogenation atmosphere can be appropriately selected, for example, any atmosphere suitable for the halogen-containing substance used, such as the atmosphere, nitrogen atmosphere, or reducing atmosphere.

[0224] (Technology 19) The method for manufacturing a halide solid electrolyte according to any one of techniques 1 to 18, wherein, after step (A), the method further includes: (B) pulverizing the halide solid electrolyte obtained in step (A).

[0225] According to the manufacturing method of Technology 19, a halide solid electrolyte with excellent ionic conductivity and reliability can be obtained at a particle size suitable for its application. Furthermore, since at least a portion of the halide solid electrolyte can be amorphized, ionic conductivity and the softness of the halide solid electrolyte particles can be improved. By increasing the softness of the halide solid electrolyte particles, the density of the pressed halide solid electrolyte powder can be increased. Therefore, the halide solid electrolyte obtained according to the manufacturing method of Technology 19 can form a dense pressed powder with high ionic conductivity.

[0226] (Technology 20) A halide solid electrolyte comprising Li, Ti, Al, and F, and further comprising at least one selected from Nb and Ga.

[0227] This configuration yields a homogeneous halide solid electrolyte with excellent ionic conductivity.

[0228] (Technology 21) The halide solid electrolyte according to Technique 20 does not actually contain TiF4.

[0229] This configuration suppresses the time-dependent changes in the properties and mechanical properties of halide solid electrolytes caused by the evaporation and deliquescence of TiF4, thus enabling the production of halide solid electrolytes with excellent properties and reliability. It should be noted that when the oxide mixture used as a raw material for the halide solid electrolyte contains trace amounts of titanium oxide (TiO2), trace amounts of TiF4 may sometimes be generated during halogenation. However, even in this case, the TiF4 can be evaporated and eliminated by open-process halogenation. Therefore, a halide solid electrolyte with excellent properties and reliability that substantially does not contain TiF4 can be obtained.

[0230] (Technology 22) The halide solid electrolyte according to technique 20 or 21, wherein the halide solid electrolyte is in particulate form.

[0231] Halide solid electrolytes are relatively soft. Therefore, based on this configuration, a relatively soft, particle-shaped solid electrolyte can be achieved. Consequently, the pressed powder of the halide solid electrolyte of Technology 22 exhibits high ionic conductivity, excellent stability, and can be shaped in any manner. Furthermore, because it can be shaped in any way, the pressed powder of the halide solid electrolyte of Technology 22 has excellent deformability. Therefore, the pressed powder of the halide solid electrolyte of Technology 22 can achieve a solid electrolyte layer for batteries with excellent properties and high reliability. It should be noted that the particle size and shape can be appropriately selected according to the application.

[0232] (Technology 23) The halide solid electrolyte according to any one of Art 20 to 22, wherein the halide solid electrolyte comprises an amorphous phase.

[0233] According to this configuration, the amorphous portion of the halide solid electrolyte becomes more flexible and exhibits superior deformability. Therefore, the pressed powder of the halide solid electrolyte can be formed into a solid electrolyte layer with higher ionic conductivity and greater stability in any shape. Thus, the pressed powder of the halide solid electrolyte of Technology 23 enables the realization of a solid electrolyte layer for batteries with excellent properties and high reliability.

[0234] (Technology 24) According to any one of the art 20 to 23, the halide solid electrolyte, in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the halide solid electrolyte using Cu-Kα rays, satisfies at least one of the following (1), (2) and (3).

[0235] (1) There are no peaks originating from TiF4.

[0236] (2) There are no peaks originating from LiF.

[0237] (3) There are no peaks originating from AlF3.

[0238] This configuration allows for the production of halide solid electrolytes with excellent properties and reliability.

[0239] (Technology 25) A positive electrode material comprising the halide solid electrolyte described in any one of techniques 20 to 24.

[0240] Based on the cathode material of Technology 25, a battery with excellent charge and discharge characteristics can be achieved.

[0241] (Technology 26) A battery having a positive electrode comprising the positive electrode material described in Technique 25.

[0242] This configuration enables the provision of batteries with excellent charge and discharge characteristics.

[0243] (Technology 27) A battery comprising: a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the electrolyte layer are selected from at least one of the halide solid electrolytes described in any one of techniques 20 to 24.

[0244] This configuration enables the provision of batteries with excellent charge and discharge characteristics.

[0245] The manufacturing method of the halide solid electrolyte and the halide solid electrolyte involved in this disclosure have been described above based on the embodiments, but this disclosure is not limited to these embodiments. Various modifications to the embodiments that can be conceived by those skilled in the art, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included within the scope of this disclosure, as long as they do not depart from the spirit of this disclosure.

[0246] Furthermore, the above-described embodiments can be modified, substituted, added, omitted, etc., within the scope of the claims or their equivalents.

[0247] Example The present disclosure will now be described in more detail with reference to the embodiments.

[0248] Synthesis of Halogen Solid Electrolytes (Example 1) As starting materials, Li2TiO3 powder (average particle size: about 0.8 μm) as a composite oxide, Li2O powder (average particle size: 1.5 μm) and Al2O3 powder (average particle size: 0.4 μm) as oxide raw materials, NH4F powder (average particle size: about 35 μm) as a halogen-containing substance, and Nb2O5 powder (average particle size: about 0.8 μm) and Ga2O3 powder (average particle size: about 0.6 μm) as additives.

[0249] Next, when the synthesized halide solid electrolyte is represented by the compositional formula (3): xLi2TiX6-(1-x)Li3MX6, Li2TiO3 powder, Li2O powder, and Al2O3 powder are weighed to achieve x=0.25. In this embodiment, X is F and M is Al in the compositional formula (3). Regarding additives, Nb2O5 powder and Ga2O3 powder are weighed to achieve NbF5 of 0.4 mol% and GaF3 of 0.02 mol% relative to [0.25Li2TiF6-0.75Li3AlF6]. NH4F powder is added in the amount (ratio) required for the fluorination of the raw materials. Specifically, an amount of NH4F sufficient to fluorinate all the raw materials according to the reaction formula is used. The weighing of these starting materials is carried out in an atmospheric atmosphere.

[0250] Using an alumina mortar and pestle, the weighed starting materials are mixed with a mortar and pestle for approximately 10 minutes to achieve homogeneity (equivalent to step (A-1) above). This yields a mixture containing an oxide mixture, halogenated substances, and additives. It should be noted that the mixing of the starting materials is carried out in normal atmospheric conditions, as was done during weighing.

[0251] Next, the mixture containing the oxide mixture, halogenated substances, and additives is heat-treated (equivalent to step (A-2) above). For the cauldron, a crucible made of high-purity (SSA-H) alumina (diameter φ: 36 mm, height: 40 mm) is used, and approximately 3 g of the above mixture is added to the crucible. To facilitate the escape of reaction gases (mainly ammonia) during heat treatment, gaps are provided on the outer edge of the upper surface of the cauldron, with spacers (0.5 mm thick), and a plate-shaped alumina lid is placed to prevent foreign matter from falling. The cauldron with the lid thus placed is then placed in the central part of the firing furnace for heat treatment. In the firing furnace, the cauldron is placed on a small heat-capacity pad made of mullite with a porosity of approximately 20%. Using pads 10 mm long, 10 mm wide, and 10 mm high, three pads are placed under one cauldron, causing the cauldron to float above the furnace bottom. This operation ensures that the heater's (radiant) heat and inert gases also circulate to the bottom of the furnace. After sealing the furnace with the door closed, nitrogen, as an inert gas, flows in at a rate of 1.5 L / min from the inlet at the bottom of the furnace and exits from the exhaust port on the upper side of the roof, allowing the gas to flow continuously until the heat treatment is complete. The heat treatment temperature is 300°C.

[0252] In this embodiment, since an oxide is used in the starting material, i.e., titanium halide is not included in the raw material, it can be heat-treated using the same method as general oxide ceramics. For example, if titanium fluoride is heat-treated in an open manner as in this embodiment, it begins to evaporate around 50°C to 100°C, and most (approximately 70%) disappears at 200°C. Therefore, halides in typical solid-phase synthesis exhibit large compositional variations. Therefore, from the viewpoint of evaporation and environmental stability, pre-preparing the Ti component as a Ti-containing composite oxide is extremely effective in suppressing compositional variations.

[0253] The halide solid electrolyte obtained by the above heat treatment was subjected to a pulverization process (equivalent to step (B) above). In this embodiment, a dry pulverization process was performed. Specifically, zirconia balls (diameter: 15 mm) and the halide solid electrolyte obtained by the above heat treatment were placed in a ball mill (volume: 1 L) lined with zirconia and pulverized for 20 hours.

[0254] (Comparative Example 1) A halide solid electrolyte was synthesized using the same method as the solid electrolyte material described in the embodiment of Patent Document 1. Specifically, the halide solid electrolyte of Comparative Example 1 was prepared by mechanochemical synthesis using fluorides as starting materials. Specifically, LiF, TiF4, and AlF3 were prepared in a molar ratio of LiF:TiF4:AlF3 = 2.75:0.25:0.75. These materials were pulverized and mixed in a mortar. The resulting mixture was then milled using a planetary ball mill at 500 rpm for 12 hours. This operation synthesized the halide solid electrolyte of Comparative Example 1.

[0255] Evaluation of Halogenated Solid Electrolytes For the halide solid electrolyte of Example 1 synthesized as described above, its crystal phase, ionic conductivity, electronic conductivity, average particle size, and BET specific surface area were evaluated. It should be noted that the crystal phase, ionic conductivity, average particle size, and BET specific surface area were evaluated for both the halide solid electrolyte before and after heat treatment and pulverization treatment. Furthermore, the crystal phase of the halide solid electrolyte of Comparative Example 1 was also evaluated. Additionally, trace component analysis was performed on the halide solid electrolyte of Example 1.

[0256] (Crystal phase) The crystal phase was determined by powder X-ray diffraction, both before and after heat treatment and before pulverization. The determination was performed using an X-ray diffractometer (RIGAKU MiniFlex 600). Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å) were used as the X-ray source.

[0257] Figure 6A This is a diagram showing the X-ray diffraction pattern of the halide solid electrolyte after heat treatment and before pulverization in the manufacturing method of Example 1. Figure 6B This is a graph showing the X-ray diffraction patterns of the halide solid electrolyte obtained in Example 1 after pulverization and the halide solid electrolyte obtained in Comparative Example 1. (See graph for details.) Figure 6A As shown, in the halide solid electrolyte synthesized in Example 1, Li2TiF6, corresponding to the first crystalline phase, and Li3AlF6, corresponding to the second crystalline phase, were identified. Figure 6B As shown, regarding the halide solid electrolyte obtained in Example 1 after pulverization, although the crystallinity decreased due to the pulverization process compared to the halide solid electrolyte before pulverization, no excess precipitated phase was observed. In contrast, as... Figure 6B As shown, the halide solid electrolyte obtained in Comparative Example 1 was found to have a compositional change compared to the halide solid electrolyte of Example 1, and the presence of LiF and AlF3 was also confirmed.

[0258] (ionic conductivity) Regarding ionic conductivity, halide solid electrolyte powder was placed in a 10 mm diameter mold, and the ionic conductivity was calculated using a uniaxial hydraulic press based on the area, thickness, and room temperature impedance characteristics of the pressed powder sample obtained under a pressure of approximately 3 t / cm. Impedance measurements were performed at room temperature under pressure. Furthermore, impedance measurements were performed at a measurement frequency of 10 Hz to 10 MHz, a measurement voltage of 1 Vrms, and without DC bias. Deviations in the electrical lengths of the cable and measuring fixture were evaluated after compensation. For the halide solid electrolyte of Example 1, the ionic conductivity before pulverization was 1.1 μS / cm, and the ionic conductivity after pulverization was 6.1 μS / cm.

[0259] (Electron conductivity) Electronic conductivity was calculated from DC voltage and current characteristics. The electronic conductivity of the halide solid electrolyte in Example 1 was <1.0 × 10⁻⁶. -9 μS / cm is a value that can be used to determine whether a substance has no electronic conductivity.

[0260] (Average particle size) The average particle size is the median particle size D50 obtained from the volumetric particle size distribution measured by a laser diffraction scattering particle size distribution measuring device. Specifically, the halide solid electrolyte powder was dispersed in a 0.01% by weight sodium hexametaphosphate aqueous solution using a homogenizer, and then the particle size distribution of the halide solid electrolyte was measured using a laser diffraction scattering particle size distribution measuring device (Microtrac, trade name: MT3100II). The D50 value of the measured particle size distribution (i.e., the cumulative 50% particle size) was regarded as the average particle size. For the halide solid electrolyte of Example 1, the average particle size before pulverization was 0.83 μm, and the average particle size after pulverization was 0.61 μm.

[0261] (BET specific surface area) The BET specific surface area was determined using a nitrogen adsorption apparatus and the BET multi-point method. For the halide solid electrolyte of Example 1, the BET specific surface area before pulverization was 2.86 m². 2 / g, the specific surface area of ​​BET after pulverization is 3.90m². 2 / g.

[0262] (Analysis of trace components) The trace components in the halide solid electrolyte were analyzed by EPMA. Specifically, the analysis was performed as follows: The halide solid electrolyte sample (powder) was attached to conductive tape and fixed (the sample was fixed within a 5 mm × 5 mm area to become a solid), and the composition was investigated (quantitatively) by point analysis. Although not confirmed by X-ray diffraction, the presence of Nb and Ga in the halide solid electrolyte of Example 1 was confirmed. The content of Nb was 0.07 atomic%, and the content of Ga was 0.004 atomic%.

[0263] Evaluation results of the halide solid electrolyte obtained in Example 1 show that, according to the manufacturing method of this disclosure, oxides can be converted into homogeneous halides, resulting in a high ionic conductivity of 6.1 μS / cm. This ionic conductivity is at or above the level of conductivity achieved by synthesis from fluoride raw materials. According to the manufacturing method of this disclosure, a halide solid electrolyte with excellent properties can be obtained. It should be noted that the electronic conductivity is <1.0 × 10⁻⁶. -9 μS / cm, confirmed as an ionicly conductive solid electrolyte with no electronic conductivity (i.e., negligible level of electronic conductivity).

[0264] Depend on Figure 6A and Figure 6B The X-ray diffraction patterns shown confirm that, according to the method of Example 1, a halide solid electrolyte containing Li2TiF6, corresponding to the first crystalline phase, and Li3AlF6, corresponding to the second crystalline phase, can be obtained. Furthermore, these X-ray diffraction patterns confirm that the halide solid electrolyte obtained in Example 1 has the same level of crystal quality as the halide solid electrolyte of Comparative Example 1 synthesized using conventional methods, and that compositional variations are suppressed compared to the halide solid electrolyte of Comparative Example 1. Additionally, for the halide solid electrolyte of Example 1, the X-ray diffraction pattern after pulverization shows a broader peak change than the X-ray diffraction pattern before pulverization, confirming the occurrence of amorphization. However, no new precipitated phases resulting from the pulverization process were observed. The changes in ionic conductivity, average particle size, and BET specific surface area before and after pulverization are as described in the explanatory sections regarding each evaluation item. These results show that the pulverization process can be implemented or not, depending on the intended use of the halide solid electrolyte. Regardless of whether pulverization is performed, the composition and crystal phase of the halide solid electrolyte remain almost unchanged, thus maintaining its excellent properties.

[0265] Furthermore, the oxygen content as an impurity in the halide solid electrolyte of Example 1 was 0.12% by mass, confirming that the oxygen in the oxide was converted into fluorine. Regarding the oxygen content, an apparatus using a melt extraction method was used, and a detector was used to measure the gases (CO2, CO) generated when the sample (powder) of the halide solid electrolyte was melted. The evaluation was based on this measurement result. The oxygen content of the halide solid electrolyte of Example 1 was lower than that of the halide solid electrolyte obtained by the synthesis method using fluorides as starting materials. It should be noted that the oxygen content of the halide solid electrolyte obtained by the synthesis method using fluorides as starting materials is typically greater than 0.5% by mass and less than 1.0% by mass. This is believed to be because moisture or oxygen absorbed by the unstable fluoride raw materials during the synthesis process, such as during storage or handling, remains after synthesis. It should be noted that when the fluoride raw materials are mixed and the solid-phase reaction is carried out without using a closed fixture, as in the manufacturing method of this disclosure, the Ti component evaporates and disappears from the halide as titanium fluoride due to the open environment. Therefore, the composition changes, resulting only in substances with ionic conductivity less than 1 μS / cm. Furthermore, in this case, a high heat treatment temperature of 500°C to 600°C is required for synthesis.

[0266] As described above, according to the manufacturing method of this disclosure, Li, Ti, M, and X-containing halide solid electrolytes with minimal compositional variations and high ionic conductivity comparable to those of conventional manufacturing methods can be produced through conventional synthesis processes (i.e., without sealing or other methods, and in an atmospheric synthesis environment). Furthermore, halide raw materials are extremely expensive; in contrast, the manufacturing method of this disclosure uses inexpensive oxide raw materials, thus reducing the manufacturing cost of halide solid electrolytes.

[0267] Industrial applicability The method for manufacturing halide solid electrolytes disclosed herein can be used, for example, as a method for manufacturing solid electrolytes for secondary batteries such as all-solid-state batteries used in various electronic devices or automobiles.

Claims

1. A method for producing a halide solid electrolyte, comprising: (A) subjecting an oxide mixture including a composite oxide containing Li and Ti and an oxide raw material containing Li and M to halogenation treatment, thereby obtaining a halide solid electrolyte containing Li, Ti, M, and X, wherein the M is at least one element selected from metal elements and metalloid elements other than Li and Ti, the X is at least one selected from F, Cl, Br, and I.

2. The method for producing a halide solid electrolyte according to claim 1, wherein the halide solid electrolyte contains a first crystal phase represented by the following composition formula (1) and a second crystal phase represented by the following composition formula (2), Composition formula (1): Li2TiX6 Composition formula (2): Li3MX6.

3. The method for producing a halide solid electrolyte according to claim 1, wherein the oxide raw material contains an oxide of Li and an oxide of M.

4. The method for producing a halide solid electrolyte according to claim 1, wherein the M contains Al.

5. The method for producing a halide solid electrolyte according to claim 1, wherein the X contains F.

6. The method for producing a halide solid electrolyte according to claim 1, wherein the oxide mixture is in a particulate form.

7. The method for producing a halide solid electrolyte according to claim 1, wherein the oxide mixture substantially does not contain TiO2.

8. The method for producing a halide solid electrolyte according to claim 1, wherein in the (A), the halogenation treatment of the oxide mixture is performed by subjecting a halogen-containing substance having thermal decomposability to heat treatment.

9. The method for producing a halide solid electrolyte according to claim 8, wherein the halogen-containing substance is in a particulate form.

10. The method for producing a halide solid electrolyte according to claim 8, wherein the (A) includes: (A-1) mixing the oxide mixture and the halogen-containing substance; and (A-2) subjecting the oxide mixture to the halogenation treatment by subjecting the mixture containing the oxide mixture and the halogen-containing substance obtained in the (A-1) to heat treatment.

11. The method for producing a halide solid electrolyte according to claim 8, wherein in the (A), the halogenation treatment of the oxide mixture is performed by generating halogen gas by subjecting the halogen-containing substance to heat treatment, and bringing the halogen gas into contact with the oxide mixture.

12. The method for producing a halide solid electrolyte according to claim 8, wherein the halogen-containing substance contains an ammonium salt.

13. The method for producing a halide solid electrolyte according to claim 12, wherein the ammonium salt contains NH4F.

14. The method for producing a halide solid electrolyte according to claim 8, wherein the halogen-containing substance contains a resin.

15. The method for producing a halide solid electrolyte according to claim 14, wherein the resin contains a fluororesin.

16. The method for producing a halide solid electrolyte according to claim 8, wherein the halogen-containing substance contains a substance that substantially does not contain inorganic components other than halogen elements in the halide solid electrolyte, which are generated by thermal decomposition by heat treatment in the (A).

17. The method for producing a halide solid electrolyte according to claim 8, wherein the halogen-containing substance contains a plurality of halogen-containing compounds.

18. The method for producing a halide solid electrolyte according to claim 1, wherein, in the (A), the halogenation treatment of the oxide mixture is performed at a temperature of 150°C or higher.

19. The method for producing a halide solid electrolyte according to claim 1, wherein after the (A), further includes: (B) subjecting the halide solid electrolyte obtained in the (A) to a pulverization treatment.

20. A halide solid electrolyte containing Li, Ti, Al, and F, and further containing at least one selected from Nb and Ga.

21. The halide solid electrolyte according to claim 20, which substantially does not contain TiF4.

22. The halide solid electrolyte according to claim 20, wherein, the halide solid electrolyte is in a particulate form.

23. The halide solid electrolyte of claim 20, wherein, the halide solid electrolyte contains an amorphous phase. the halide solid electrolyte is in a particulate form.

24. The halide solid electrolyte according to claim 20, in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the halide solid electrolyte using Cu-Ka rays, at least one of (1), (2), and (3) selected from the following is satisfied, (1) a peak derived from TiF4 is not present; (2) a peak derived from LiF is not present; (3) a peak derived from AlF3 is not present.

25. A positive electrode material comprising the halide solid electrolyte according to claim 20.

26. A battery provided with a positive electrode comprising the positive electrode material according to claim 25.

27. A battery provided with: a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode, at least one selected from the positive electrode, the negative electrode, and the electrolyte layer containing the halide solid electrolyte according to claim 20. wherein ​

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