Method for producing crystalline sulfide solid electrolyte, crystalline sulfide solid electrolyte, and electrode composite and lithium ion battery each including the same

Abstract

To provide a crystalline sulfide solid electrolyte that suppresses granulation and increase in specific surface area as well as significant decrease in ion conductivity, while having superior oxidation resistance, and an electrode composite and a lithium ion battery each including the crystalline sulfide solid electrolyte.SOLUTION: The present invention provides a crystalline sulfide solid electrolyte and a method for producing the crystalline sulfide solid electrolyte. This method includes: mixing raw material inclusion, which includes lithium, sulfur, phosphorus, and halogen atoms, to obtain a reaction product; heating the reaction product to obtain a crystalline product; and pulverizing the crystalline product to make at least a part of the surface of the crystalline product amorphous. In the pulverization, the cumulative power is 1(Wh / kg) or more and 500(Wh / kg) or less. There are also provided an electrode composite and a lithium ion battery, each including the crystalline sulfide solid electrolyte.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a crystalline sulfide solid electrolyte, a crystalline sulfide solid electrolyte, an electrode mixture containing the same, and a lithium ion battery. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries for use as their power sources has become increasingly important. Traditionally, batteries used for such applications have used electrolytes containing flammable organic solvents. However, because the electrolytes are liquid and flammable, safety concerns regarding leakage, fire, and other issues have arisen when used in batteries. In particular, for automotive applications, high capacity and high output are required, and safety concerns regarding batteries using conventional electrolytes are becoming increasingly serious. Therefore, all-solid-state batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed because such batteries eliminate the use of flammable organic solvents, simplify safety devices, and offer superior manufacturing costs and productivity.

[0003] Various types of solid electrolytes have been developed for use in the solid electrolyte layer of all-solid-state batteries, with particular emphasis being placed on the development of solid electrolytes with high ionic conductivity. Examples of such solid electrolytes include solid electrolytes containing lithium as a conductive species, such as the Li2S-P2S5-based solid electrolyte disclosed in Patent Document 1, and solid electrolytes containing halogen atoms, such as the Li2S-P2S5-LiI-based sulfide solid electrolyte disclosed in Patent Document 2 and the Li2S-P2S5-LiI-LiBr-based sulfide solid electrolyte disclosed in Patent Documents 3 and 4.

[0004] Solid electrolytes can be used in the positive electrode, negative electrode, and solid electrolyte layer of all-solid-state batteries. In the electrodes (positive electrode, negative electrode), the solid electrolyte is used in combination with an electrode active material (positive electrode active material, negative electrode active material). Because both the solid electrolyte and the electrode active material are solid electrolytes, a small particle size of the solid electrolyte is desirable, as this facilitates the formation of a contact interface between the electrode active material and the solid electrolyte, improving ionic and electronic conduction paths and resulting in excellent battery performance. Therefore, attention has also been focused on techniques for reducing the particle size of the solid electrolyte (hereinafter also referred to as "atomization"). Patent Document 5, for example, discloses a technique for atomizing the solid electrolyte using a pulverizer. Patent Document 6, for example, discloses a manufacturing method including a step of adding an ether compound to a coarse sulfide solid electrolyte material and atomizing the material by a pulverization process. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-228570 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-201110 [Patent Document 3] International Publication No. 2014 / 208180 Brochure [Patent Document 4] International Publication No. 2014 / 208239 Brochure [Patent Document 5] Japanese Patent Application Publication No. 2016-203087 [Patent Document 6] Japanese Patent Application Laid-Open No. 2013-020894 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and aims to provide a crystalline sulfide solid electrolyte having excellent oxidation resistance while suppressing granulation, an increase in specific surface area, and a significant decrease in conductivity, as well as an electrode mixture and a lithium ion battery using the same. [Means for solving the problem]

[0007] The method for producing a crystalline sulfide solid electrolyte according to the present invention comprises: mixing raw materials containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms to obtain a reactant; heating the reaction to obtain a crystalline product; and pulverizing the crystalline product to amorphize at least a portion of the surface of the crystalline product; Including, The integrated power in the pulverization treatment is 1 (Wh / kg) or more and 500 (Wh / kg) or less; A method for producing a crystalline sulfide solid electrolyte, is.

[0008] The crystalline sulfide solid electrolyte according to the present invention is A crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, The crystalline sulfide solid electrolyte has an amorphous portion on at least a part of its surface. crystalline sulfide solid electrolyte, is.

[0009] The electrode mixture according to the present invention is an electrode mixture comprising the crystalline sulfide solid electrolyte and an electrode active material; is.

[0010] The lithium ion battery according to the present invention is A lithium ion battery comprising at least one of the crystalline sulfide solid electrolyte and the electrode mixture; is. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a crystalline sulfide solid electrolyte having excellent oxidation resistance while suppressing granulation, an increase in specific surface area, and a significant decrease in ionic conductivity, as well as an electrode mixture and a lithium ion battery using the same. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an X-ray diffraction spectrum of the powder obtained in Example 1. [Figure 2] 1 shows CV curves of the powders obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0014] (Findings gained by the inventors to arrive at the present invention) As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention.

[0015] As a solid electrolyte used in an all-solid-state battery, from the viewpoint of obtaining higher battery performance, a solid electrolyte containing lithium as a conductive species is preferable as described above. That is, an all-solid-state lithium secondary battery is preferable as an all-solid-state battery. The electrodes (positive electrode, negative electrode) of an all-solid-state battery are used in combination with a solid electrolyte and an electrode active material (positive electrode active material, negative electrode active material). More specifically, an electrode mixture containing at least a solid electrolyte, an electrode active material, and a conductive agent is used. Furthermore, good ionic conduction and conductive paths are essential to obtain excellent battery characteristics.

[0016] For example, for a positive electrode, the conductive path is preferably such that electrons flow from the positive electrode current collector through the conductive agent in the electrode composite, electrons are exchanged between the conductive agent and the positive electrode active material, and lithium ions are exchanged between the positive electrode active material and the solid electrolyte. A potential difference may occur between the conductive agent and the solid electrolyte, and an electrochemical reaction may occur at the interface between the conductive agent and the solid electrolyte. When the negative electrode is used as a reference electrode, a positive potential is applied to the positive electrode composite, and the electrochemical reaction on the positive electrode side at this time is an oxidation reaction. This oxidation reaction leads to deterioration of the solid electrolyte, which is one of the factors that increase the internal resistance in all-solid-state batteries.

[0017] Therefore, the present inventors focused on the oxidation reaction that occurs at the interface between the conductive agent and the solid electrolyte, and thought that by using a solid electrolyte that is less susceptible to this oxidation reaction, an increase in internal resistance could be suppressed and excellent battery characteristics could be obtained. In other words, by using a solid electrolyte that has oxidation resistance, which is the property of being less susceptible to oxidation reactions, an increase in internal resistance could be suppressed and excellent battery characteristics could be obtained.

[0018] The present inventors confirmed the oxidation resistance of amorphous and crystalline solid electrolytes by cyclic voltammetry (CV) measurements and found that the amorphous solid electrolyte was less susceptible to oxidation. Based on this finding, they hypothesized that a crystalline solid electrolyte could be partially amorphous to obtain a solid electrolyte with high ionic conductivity and excellent oxidation resistance. One possible way to partially amorphousize a crystalline solid electrolyte is to perform a pulverization process. However, depending on the extent of the pulverization process, the entire particle may become amorphous, significantly reducing ionic conductivity. Furthermore, granulation may also result in a change in particle size distribution and an increase in specific surface area.

[0019] Furthermore, techniques for performing a pulverization process for the purpose of particle size reduction in solid electrolyte manufacturing methods are disclosed, for example, in Patent Documents 5 and 6. Patent Document 5 specifically discloses a method for manufacturing a sulfide solid electrolyte material having a flat shape and an average particle size of 1.9 μm or less, including a pulverization step of forming a flat sulfide solid electrolyte material by pulverization using a pulverization device with pulverization media. Patent Document 6 also specifically discloses a manufacturing method including a step of adding an ether compound to a coarse-grained sulfide solid electrolyte material and pulverizing the material to obtain fine particles. However, neither of these patent documents aims to obtain a crystalline sulfide solid electrolyte, nor does it disclose the pulverization of a crystalline sulfide solid electrolyte obtained once, or the amorphization of at least a portion of the surface, as in the manufacturing method of the present embodiment. As described above, in conventional methods for producing a sulfide solid electrolyte, a crystalline sulfide solid electrolyte is once obtained and then pulverized at a specific integrated power, thereby amorphizing at least a portion of the surface, thereby ensuring high ionic conductivity, obtaining excellent oxidation resistance, and further suppressing granulation and an increase in specific surface area.

[0020] Based on the above findings, it has been discovered that in a method for producing a crystalline sulfide solid electrolyte, by subjecting a crystalline sulfide solid electrolyte obtained by crystallization to a pulverization treatment using a specific integrated power, it is possible to suppress granulation, an increase in specific surface area, and a significant decrease in ionic conductivity, as well as to obtain a crystalline sulfide solid electrolyte having excellent oxidation resistance.

[0021] (Sulfide solid electrolyte) First, the terms used in this specification will be explained. In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere. The sulfide solid electrolyte in this embodiment is a solid electrolyte that contains at least lithium atoms and sulfur atoms, has ionic conductivity due to the lithium atoms, and also contains phosphorus atoms and halogen atoms.

[0022] The term "solid electrolyte" includes both amorphous solid electrolytes and crystalline solid electrolytes. In this specification, a crystalline solid electrolyte refers to a solid electrolyte in which a peak derived from the solid electrolyte is observed in an X-ray diffraction pattern in an X-ray diffraction measurement, regardless of whether or not a peak derived from the raw material of the solid electrolyte is present. That is, a crystalline solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a part of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as the crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous solid electrolyte in part. Therefore, a crystalline solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature equal to or higher than the crystallization temperature. In addition, in this specification, an amorphous solid electrolyte refers to an amorphous solid electrolyte that has a halo pattern in which peaks other than those derived from the material are substantially not observed in an X-ray diffraction pattern obtained by X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0023] (Various aspects of this embodiment) A method for producing a crystalline sulfide solid electrolyte according to a first aspect of the present embodiment includes: mixing raw materials containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms to obtain a reactant; heating the reaction to obtain a crystalline product; and The crystalline product is subjected to a pulverization treatment to amorphize at least a portion of the surface of the crystalline product. Including, The integrated power in the pulverization treatment is 1 (Wh / kg) or more and 500 (Wh / kg) or less; A method for producing a crystalline sulfide solid electrolyte, is.

[0024] In the method for producing a crystalline sulfide solid electrolyte according to the present embodiment, the reactant obtained by obtaining the reactant is a product of the reaction of the solid electrolyte raw materials contained in the raw material inclusions, contains at least sulfur atoms and lithium atoms, and has ionic conductivity attributable to the lithium atoms. Furthermore, in an X-ray diffraction pattern obtained by X-ray diffraction measurement, the reactant has a halo pattern in which peaks other than those attributable to the material are substantially not observed, and therefore, in terms of its properties, it can be called an amorphous sulfide solid electrolyte.

[0025] The crystalline product obtained by heating the reaction product obtained by the above mixing can be said to be obtained by heating an amorphous sulfide solid electrolyte in terms of its properties, and therefore has a crystalline structure derived from the solid electrolyte. Therefore, the crystalline product can be called a crystalline sulfide solid electrolyte in terms of its properties.

[0026] In the manufacturing method of this embodiment, the crystalline product thus obtained is pulverized using a specific integrated power, thereby amorphizing at least a portion of the surface thereof. The sulfide solid electrolyte obtained by the manufacturing method of this embodiment can be said to be a crystalline sulfide solid electrolyte because peaks derived from the solid electrolyte are observed in the X-ray diffraction pattern in X-ray diffraction measurement. However, the peak intensity is weaker than that of the crystalline product. Furthermore, according to CV measurements (oxidation current measurements) in the examples, the oxidation current increases when the reactant is converted into a crystalline product. However, when the crystalline product is pulverized using a specific integrated power, the oxidation current decreases to the same level as that of the reactant. From these results, it can be said that the sulfide solid electrolyte obtained by the manufacturing method of this embodiment retains the structure of the crystalline sulfide solid electrolyte, but a portion of it is amorphized to form an amorphous sulfide solid electrolyte. Furthermore, considering that pulverizing the crystalline product causes the surfaces of the crystalline products to come into contact with each other, it can be said that at least a portion of the surface of the crystalline product is amorphized. Therefore, it can be said that pulverizing the crystalline product using a specific integrated power can amorphize at least a portion of its surface.

[0027] In the manufacturing method of this embodiment, it is important to first obtain the crystalline sulfide solid electrolyte and then pulverize it. This configuration allows at least a portion of the surface of the crystalline sulfide solid electrolyte to be amorphized while maintaining its structure. Therefore, it is possible to impart the characteristics of the amorphous sulfide solid electrolyte, i.e., excellent oxidation resistance, to the crystalline sulfide solid electrolyte while maintaining its high ionic conductivity.

[0028] It is also important that the amorphization is limited to at least a portion of the surface, particularly the surface. If the entire surface is amorphized, the resulting electrolyte will no longer be a crystalline sulfide solid electrolyte, making it impossible to obtain high ionic conductivity. Restricting the amorphization to at least a portion of the surface can be achieved by setting the integrated power in the pulverization treatment of the crystalline product within a specific range. In the manufacturing method of this embodiment, by performing the pulverization treatment while setting the integrated power within a specific range, an effect is also obtained in that an increase in the specific surface area associated with a change in particle size distribution due to granulation can be suppressed. Thus, in the production method of this embodiment, a crystalline sulfide solid electrolyte is obtained, and then the crystalline sulfide solid electrolyte is pulverized at a specific integrated power, thereby amorphizing at least a portion of the surface, thereby ensuring high ionic conductivity, obtaining excellent oxidation resistance, and further making it possible to suppress granulation and an increase in specific surface area.

[0029] A method for producing a crystalline sulfide solid electrolyte according to a second aspect of the present embodiment is the same as the first aspect, except that: In obtaining the reactant, the mixing is carried out using a grinder. That is it.

[0030] In the manufacturing method of this embodiment, the method for obtaining the above-mentioned reactant is not particularly limited as long as the solid electrolyte raw materials contained in the raw material inclusions can be mixed to obtain a reactant (i.e., an amorphous sulfide solid electrolyte), and various methods can be used. The method of performing mixing using a pulverizer according to the second embodiment is a method known as a mechanical milling method.

[0031] A method for producing a crystalline sulfide solid electrolyte according to a third aspect of the present embodiment is the same as the first aspect, except that: Obtaining the reactant comprises: mixing the raw material contents in the presence of a complexing agent to obtain a complex; and heating the complex to obtain a complex decomposition product; Including, That is it.

[0032] As described above, various methods can be used to obtain the above-mentioned reactant. The method according to the third embodiment is a liquid phase method (particularly, a heterogeneous method), in which a complex containing a solid electrolyte raw material is formed using a complexing agent, and the complexing agent contained in the complex is removed by heating, thereby obtaining a reactant (i.e., an amorphous sulfide solid electrolyte).

[0033] Although the details of the complexing agent will be described later, the use of the complexing agent allows the formation of a complex between the solid electrolyte raw material and the complexing agent. When contained in a sulfide solid electrolyte, halogen atoms have the property of exhibiting high ionic conductivity, but they also have the property of being difficult to incorporate into the sulfide solid electrolyte. Since the solid electrolyte raw material containing halogen atoms is also incorporated into the complex using the complexing agent, it becomes easier to maintain a uniform dispersion state of the solid electrolyte raw material, particularly the dispersion state of the halogen atoms, and as a result, it becomes easier to obtain a sulfide solid electrolyte with high ionic conductivity.

[0034] A method for producing a crystalline sulfide solid electrolyte according to a fourth aspect of the present embodiment is the same as the first to third aspects, except that: The crystalline sulfide solid electrolyte is a sulfide solid electrolyte having a thiolithium region II crystal structure, That is it.

[0035] In the manufacturing method of this embodiment, it is possible to manufacture a desired sulfide solid electrolyte by changing the type and compounding ratio of the solid electrolyte raw materials contained in the raw material inclusions. A crystalline sulfide solid electrolyte having a thiolicon region II crystal structure is known as a sulfide solid electrolyte with extremely high ionic conductivity, and is preferable as the crystalline sulfide solid electrolyte to be obtained by the manufacturing method of this embodiment.

[0036] The crystalline sulfide solid electrolyte according to the fifth aspect of the present embodiment is A crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, The crystalline sulfide solid electrolyte has an amorphous portion on at least a part of its surface. crystalline sulfide solid electrolyte, That is it.

[0037] The crystalline sulfide solid electrolyte of this embodiment can be easily produced by the production method of this embodiment described above. After the crystalline sulfide solid electrolyte is obtained, it is pulverized at a specific integrated power to have an amorphous portion on at least a portion of the surface. Furthermore, the crystalline sulfide solid electrolyte of this embodiment has the properties of having excellent oxidation resistance while maintaining high ionic conductivity, and further suppressing granulation and an increase in specific surface area.

[0038] A crystalline sulfide solid electrolyte according to a sixth aspect of the present embodiment is the fifth aspect, The rate of decrease in oxidation current measured by cyclic voltammetry (CV measurement), calculated using the following formula, is 10% or more. That is it. Reduction rate of oxidation current (%) = (oxidation current 2 - oxidation current 1) / oxidation current 2 x 100 Oxidation current 1: Oxidation current (mA) of a crystalline sulfide solid electrolyte having at least a partially amorphous portion on its surface Oxidation current 2: Oxidation current (mA) of a crystalline sulfide solid electrolyte having at least a partially amorphous portion on its surface

[0039] The crystalline sulfide solid electrolyte of this embodiment is basically a crystalline sulfide solid electrolyte, but has an amorphous portion on at least a part of its surface. Therefore, while maintaining high ionic conductivity, which is a characteristic of crystalline sulfide solid electrolytes, it also has the added characteristic of excellent oxidation resistance, which is a characteristic of amorphous sulfide solid electrolytes, that is, the oxidation current decrease rate calculated by the above formula using the oxidation current measured by CV measurement is as high as 10% or more.

[0040] The crystalline sulfide solid electrolyte according to a seventh aspect of the present embodiment is the same as the fifth and sixth aspects, A sulfide solid electrolyte having a thiolithium region II crystal structure. That is it.

[0041] A sulfide solid electrolyte having a thiolicon region II crystal structure is known as a sulfide solid electrolyte having extremely high ionic conductivity, and is preferable as the crystalline sulfide solid electrolyte to be obtained by the manufacturing method of this embodiment.

[0042] The electrode mixture according to the eighth aspect of this embodiment is The crystalline sulfide solid electrolyte according to any one of the fifth to seventh embodiments and an electrode active material are included. That is it. Furthermore, the lithium ion battery according to the ninth aspect of the present embodiment is The crystalline sulfide solid electrolyte according to any one of the fifth to seventh forms and the electrode active material according to the eighth form are included. That is it.

[0043] As described above, the crystalline sulfide solid electrolyte of this embodiment has excellent oxidation resistance while suppressing granulation, an increase in specific surface area, and a significant decrease in ionic conductivity. Therefore, an electrode composite containing the crystalline sulfide solid electrolyte of this embodiment and a lithium ion battery using the same have excellent battery performance.

[0044] [Method for producing sulfide solid electrolyte] The method for producing the sulfide solid electrolyte of this embodiment includes the steps of: mixing raw materials containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms to obtain a reactant; heating the reaction to obtain a crystalline product; and pulverizing the crystalline product to amorphize at least a portion of the surface of the crystalline product; Including, The integrated power in the pulverization treatment is 1 (Wh / kg) or more and 500 (Wh / kg) or less; A method for producing a crystalline sulfide solid electrolyte, is.

[0045] [Obtaining the reactant] The manufacturing method of this embodiment includes mixing raw materials containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a reactant. In the manufacturing method of this embodiment, the method for obtaining the reactant is not particularly limited as long as the solid electrolyte raw materials contained in the raw material contents are mixed and the reactant is obtained, and various methods can be used. As the method for obtaining the reactant, the following two methods are preferably mentioned. (i) Mixing using a grinder (ii) A method in which the raw material components are mixed in the presence of a complexing agent to obtain a complex, and the complex is heated to obtain a decomplexed product.

[0046] (Method (i) for obtaining reactants) First, the method (i) for obtaining the reactant, the so-called mechanical milling method, will be explained starting from the raw material contents.

[0047] (Raw material content) The raw material content used in this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and more specifically, it is a content containing a compound containing one or more selected from the group consisting of these atoms (hereinafter also referred to as "solid electrolyte raw material"). The raw material content used in this embodiment preferably contains two or more solid electrolyte raw materials.

[0048] Examples of solid electrolyte raw materials contained in the raw material content include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; phosphorus sulfides such as diphosphorus trisulfide (P2S3) and diphosphorus pentasulfide (P2S5); phosphorus halides such as various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), various phosphorus bromides (PBr3, PBr5), and various phosphorus iodides (PI3, P2I4); thiophosphoryl fluoride (PSF3), chloride Representative examples include raw materials consisting of at least two atoms selected from the above four types of atoms, such as thiophosphoryl halides, such as thiophosphoryl (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl dichloride fluoride (PSCl2F), and thiophosphoryl dibromide fluoride (PSBr2F); and elemental halogens, such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), with bromine (Br2) and iodine (I2) being preferred.

[0049] Examples of usable solid electrolyte raw materials other than those mentioned above include solid electrolyte raw materials containing at least one atom selected from the above four types of atoms and also containing atoms other than the four types of atoms, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS), aluminum sulfide, and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium, such as sodium iodide, sodium fluoride, sodium chloride, and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides, and bismuth halides; and phosphorus oxyhalides such as phosphorus oxychloride (POCl) and phosphorus oxybromide (POBr).

[0050] Among the above, preferred are lithium sulfide, phosphorus sulfides such as diphosphorus trisulfide (PS) and diphosphorus pentasulfide (PS), halogen elements such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. Furthermore, when oxygen atoms are introduced into the solid electrolyte, lithium oxide, lithium hydroxide, and phosphate compounds such as lithium phosphate are preferred. Preferred combinations of solid electrolyte raw materials include, for example, a combination of lithium sulfide, diphosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, diphosphorus pentasulfide, and a halogen element. Preferred lithium halides are lithium bromide and lithium iodide, and preferred halogen elements are bromine and iodine.

[0051] In this embodiment, Li3PS4 containing the PS4 structure can be used as part of the raw material. Specifically, Li3PS4 is prepared in advance by manufacturing or the like, and then used as the raw material. The content of Li3PS4 relative to the total of the raw materials is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%.

[0052] When Li3PS4 and a simple halogen are used, the content of the simple halogen relative to Li3PS4 is preferably 1 to 50 mol %, more preferably 10 to 40 mol %, even more preferably 20 to 30 mol %, and even more preferably 22 to 28 mol %.

[0053] The lithium sulfide used in this embodiment is preferably in the form of particles. The average particle size of lithium sulfide particles (D 50 ) is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.5 μm or more and 100 μm or less, and even more preferably 1 μm or more and 20 μm or less. 50) is the particle size at which, when a particle size distribution cumulative curve is drawn, the cumulative total, starting from the smallest particle size, reaches 50% (by volume) of the total, and the volume distribution refers to the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles, i.e., within the same range as that of the lithium sulfide particles.

[0054] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as the solid electrolyte raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 78 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other solid electrolyte raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these raw materials is preferably 50 to 100 mol%, more preferably 55 to 90 mol%, and even more preferably 60 to 85 mol%. Furthermore, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the proportion of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 80 mol%, still more preferably 30 to 70 mol%, and particularly preferably 40 to 60 mol%.

[0055] When a halogen element is used as a solid electrolyte raw material, and lithium sulfide or diphosphorus pentasulfide is used, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because higher ionic conductivity can be obtained at these ratios. From the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0056] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount thereof preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5). 2≦2α+β≦100…(2) 4≦2α+β≦80 …(3) 6≦2α+β≦50 …(4) 6≦2α+β≦30 …(5)

[0057] When two types of halogens are used as simple substances, the molar number of one halogen atom in the substance is A1, and the molar number of the other halogen atom in the substance is A2. The ratio A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0058] Furthermore, when the two types of halogen atoms are bromine and iodine, where the number of moles of bromine is B1 and the number of moles of iodine is B2, the ratio B1:B2 is preferably 1 to 99:99 to 1, more preferably 15:85 to 90:10, even more preferably 20:80 to 80:20, still more preferably 30:70 to 75:25, and particularly preferably 35:65 to 75:25.

[0059] (Crusher) In the method (i) for obtaining the reaction product, the solid electrolyte raw materials contained in the raw material content are mixed using a pulverizer. A pulverizer is literally a device used for pulverizing, but it can also stir and mix materials at the same time. Therefore, mixing of solid electrolytes can be performed using a pulverizer.

[0060] The pulverizer that can be used in the production method of this embodiment is not particularly limited as long as it can mix the solid electrolyte raw materials, and for example, a media-type pulverizer that uses a pulverizing medium can be used.

[0061] Media-type mills are broadly classified into vessel-driven mills and media-agitation mills. Examples of vessel-driven mills include agitation tanks, grinding tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation mills include impact mills such as cutter mills, hammer mills, and pin mills; tower mills and other tower-type mills; agitation tank mills such as attritors, aquamizers, and sand grinders; flow-through tank mills such as Viscomills and pearl mills; flow-through pipe mills; annular mills such as Coball mills; continuous dynamic mills; and single- or multi-shaft kneaders. Considering the ease of adjusting the particle size of the resulting reaction product, the ball mill and bead mill exemplified as the container-driven grinder are preferred, and among them, planetary mills are preferred.

[0062] These pulverizers can be appropriately selected depending on the desired scale, etc. For relatively small scales, container-driven pulverizers such as ball mills and bead mills can be used, while for large scales or mass production, other types of pulverizers may be used.

[0063] Furthermore, when a liquid such as a solvent is used during mixing, that is, when the materials to be mixed are in a liquid state or a slurry state, a wet mill that can handle wet milling is preferred. Representative examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills, with wet bead mills using beads as milling media being preferred because they allow for flexible adjustment of milling conditions and are suitable for smaller particle sizes. Alternatively, dry mills such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills) can also be used.

[0064] When the material to be mixed is in a liquid or slurry state, a flow-through mill can be used, which can be operated to circulate the material as needed. Specifically, a mill that circulates the material between a mill (milling mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel) can be used. It is also possible to use a mill (one-pass type) that is not a flow-through mill and is capable of the above-mentioned circulation operation.

[0065] The size of the beads or balls used in the ball mill or bead mill may be appropriately selected depending on the desired particle size, processing amount, etc. For example, the diameter of the beads is usually 0.03 mm or more, preferably 0.1 mm or more, more preferably 0.3 mm or more, with the upper limit being usually 5.0 mm or less, preferably 3.0 mm or less, more preferably 2.0 mm or less. The diameter of the balls is usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 3.0 mm or more, with the upper limit being usually 20.0 mm or less, preferably 15.0 mm or less, more preferably 10.0 mm or less. Examples of materials include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0066] When a ball mill or a bead mill is used, the rotation speed varies depending on the scale of the treatment and cannot be generalized, but is usually 10 rpm or more, preferably 20 rpm or more, and more preferably 50 rpm or more, and the upper limit is usually 1,000 rpm or less, preferably 900 rpm or less, more preferably 800 rpm or less, and even more preferably 700 rpm or less. In this case, the grinding time cannot be generalized because it varies depending on the scale of the treatment, but it is usually 0.5 hours or more, preferably 1 hour or more, and more preferably 2 hours or more, and the upper limit is usually 100 hours or less, preferably 72 hours or less, more preferably 48 hours or less, even more preferably 24 hours or less, and even more preferably 10 hours or less.

[0067] (solvent) In the method (i) for obtaining the reactant, a solvent may be used as described above. As the solvent, a wide range of solvents that have been used in conventional methods for producing solid electrolytes can be used.

[0068] Examples of such solvents include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; and solvents containing carbon atoms such as alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, nitrile solvents, ether solvents having 4 or more carbon atoms on one side, and solvents containing carbon atoms and heteroatoms. More specifically, examples include the solvents listed as solvents that can be used in the method (ii) for obtaining the reaction product described below.

[0069] (Method (ii) for obtaining reactants) The method (ii) for obtaining the reaction product is a method in which the raw material components are mixed in the presence of a complexing agent to obtain a complex, and the complex is heated to obtain a decomplexed product. As the raw material ingredients used in the method (ii), those explained as the raw material ingredients that can be used in the above method (i) are used.

[0070] (complexing agent) As described above, the complexing agent is a compound that easily forms a complex with the solid electrolyte raw material contained in the raw material inclusions, and is, for example, a compound that can form a complex with lithium sulfide and diphosphorus pentasulfide, which are preferably used as solid electrolyte raw materials, Li3PS4 obtained when these are used, and solid electrolyte raw materials containing halogen atoms (hereinafter, these are also collectively referred to as "solid electrolyte raw materials, etc.").

[0071] The complexing agent can be any compound having the above properties without any particular limitation, and is preferably a compound containing an atom having a high affinity with lithium atoms, such as a heteroatom such as a nitrogen atom, an oxygen atom, or a chlorine atom, and more preferably a compound having a group containing such a heteroatom, because such a heteroatom or group containing such a heteroatom can coordinate (bond) with lithium.

[0072] It is believed that the heteroatoms present in the complexing agent molecules have a high affinity for lithium atoms and have the property of easily bonding with the solid electrolyte raw materials, etc. to form a complex (hereinafter also simply referred to as a "complex"). Therefore, by mixing the solid electrolyte raw materials with the complexing agent, a complex is formed, which makes it easier to maintain the uniform dispersion state of the solid electrolyte raw materials, particularly the dispersion state of the halogen atoms, and as a result, it is believed that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0073] Whether the complexing agent is capable of forming a complex with the solid electrolyte raw material or the like can be directly confirmed by, for example, an infrared absorption spectrum measured by FT-IR analysis (diffuse reflectance method). When a powder obtained by stirring tetramethylethylenediamine (hereinafter also referred to simply as "TMEDA"), which is one of the preferred complexing agents, with lithium iodide (LiI) and the complexing agent itself were analyzed by FT-IR analysis (diffuse reflectance method), the spectrum of TMEDA itself and the spectrum of the complexing agent itself, particularly in the range of 1000 to 1250 cm -1 The peaks due to the CN stretching vibration are different in this case. Also, considering that it is known that LiI-TMEDA complexes are formed by stirring and mixing TMEDA and lithium iodide (e.g., Aust. J. Chem., 1988, 41, 1925-34, especially Fig. 2), it is reasonable to assume that a LiI-TMEDA complex is formed.

[0074] Furthermore, for example, when a powder obtained by stirring a complexing agent (TMEDA) and Li3PS4 is analyzed by FT-IR analysis (diffuse reflectance method) in the same manner as above, the spectrum of TMEDA itself is different from that of the powder obtained by stirring a complexing agent (TMEDA) and Li3PS4 in the same manner as above. -1 Although the peaks due to the CN stretching vibrations in the spectrum are different from those of the LiI-TMEDA complex, the spectrum is similar to that of the LiI-TMEDA complex. This suggests that a Li3PS4-TMEDA complex is formed.

[0075] The complexing agent preferably has at least two heteroatoms capable of coordinating (bonding) in the molecule, and more preferably has a group containing at least two heteroatoms in the molecule. By having a group containing at least two heteroatoms in the molecule, the solid electrolyte raw material and the like can be bonded via at least two heteroatoms in the molecule. Furthermore, among heteroatoms, a nitrogen atom is preferred, and as a group containing a nitrogen atom, an amino group is preferred. In other words, an amine compound is preferred as the complexing agent.

[0076] The amine compound is not particularly limited as long as it has an amino group in the molecule and can promote the formation of a complex, but a compound having at least two amino groups in the molecule is preferred. By having such a structure, the solid electrolyte raw materials and the like can be bonded via at least two nitrogen atoms in the molecule to form a complex.

[0077] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination.

[0078] More specifically, typical and preferred examples of the aliphatic amine include aliphatic primary diamines such as ethylenediamine, diaminopropane, and diaminobutane; aliphatic secondary diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; and aliphatic tertiary diamines such as N,N,N',N'-tetramethyldiaminomethane, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldiaminopropane, N,N,N',N'-tetraethyldiaminopropane, N,N,N',N'-tetramethyldiaminobutane, N,N,N',N'-tetramethyldiaminopentane, and N,N,N',N'-tetramethyldiaminohexane. In the examples given in this specification, for example, in the case of diaminobutane, unless otherwise specified, all isomers of butane, such as linear and branched isomers, are included, in addition to isomers relating to the position of the amino group, such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane.

[0079] The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0080] Typical preferred examples of the alicyclic amine include alicyclic primary diamines such as cyclopropanediamine and cyclohexanediamine; alicyclic secondary diamines such as bisaminomethylcyclohexane; and alicyclic tertiary diamines such as N,N,N',N'-tetramethyl-cyclohexanediamine and bis(ethylmethylamino)cyclohexane. Typical preferred examples of the heterocyclic amine include heterocyclic primary diamines such as isophoronediamine; heterocyclic secondary diamines such as piperazine and dipiperidylpropane; and heterocyclic tertiary diamines such as N,N-dimethylpiperazine and bismethylpiperidylpropane. The number of carbon atoms in the alicyclic amine and heterocyclic amine is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0081] Representative preferred examples of the aromatic amine include aromatic primary diamines such as phenyldiamine, tolylenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-bismethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; and aromatic tertiary diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine. The aromatic amine preferably has 6 or more carbon atoms, more preferably 7 or more carbon atoms, and even more preferably 8 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0082] The amine compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom. Although diamines have been given as specific examples, it goes without saying that the amine compounds that can be used in this embodiment are not limited to diamines, and examples thereof include aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the above-mentioned aliphatic diamines, piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine, pyridine compounds such as pyridine and picoline, morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine, imidazole compounds such as imidazole and methylimidazole, and the above-mentioned alicyclic diamines. In addition to monoamines such as alicyclic monoamines such as the corresponding monoamines, heterocyclic monoamines corresponding to the above heterocyclic diamines, and aromatic monoamines corresponding to the above aromatic diamines, polyamines having three or more amino groups, such as diethylenetriamine, N,N',N''-trimethyldiethylenetriamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, triethylenetetramine, N,N'-bis[(dimethylamino)ethyl]-N,N'-dimethylethylenediamine, hexamethylenetetramine, and tetraethylenepentamine, can also be used.

[0083] Among the above, from the viewpoint of obtaining higher ionic conductivity, a tertiary amine having a tertiary amino group as the amino group is preferred, a tertiary diamine having two tertiary amino groups is more preferred, a tertiary diamine having two tertiary amino groups at both ends is even more preferred, and an aliphatic tertiary diamine having tertiary amino groups at both ends is even more preferred. Among the above amine compounds, the aliphatic tertiary diamine having tertiary amino groups at both ends is preferably tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, or tetraethyldiaminopropane, and in consideration of ease of availability, etc., tetramethylethylenediamine or tetramethyldiaminopropane is preferred.

[0084] Furthermore, compounds having a nitrogen atom as a heteroatom and a group other than an amino group, such as a nitro group or an amide group, can also provide the same effect.

[0085] In the production method of this embodiment, the complexing agent is preferably a compound containing an oxygen atom as a heteroatom in addition to the above-mentioned compound containing a nitrogen atom. The compound containing an oxygen atom is preferably a compound having one or more functional groups selected from an ether group and an ester group as the group containing an oxygen atom, and among these, a compound having an ether group is particularly preferred. That is, an ether compound is particularly preferred as a complexing agent containing an oxygen atom.

[0086] Examples of the ether compound include aliphatic ethers, alicyclic ethers, heterocyclic ethers, and aromatic ethers, and these compounds may be used alone or in combination.

[0087] More specifically, examples of aliphatic ethers include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and tert-butyl methyl ether; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, and diethoxyethane; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme) and triethylene oxide glycol dimethyl ether (triglyme); and ethers containing hydroxyl groups such as diethylene glycol and triethylene glycol. The aliphatic ether preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and even more preferably 4 or more carbon atoms, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less carbon atoms. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ether is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0088] Examples of alicyclic ethers include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, and dioxolane. Examples of heterocyclic ethers include furan, benzofuran, benzopyran, dioxene, dioxin, morpholine, methoxyindole, and hydroxymethyldimethoxypyridine. The number of carbon atoms in the alicyclic ether and heterocyclic ether is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0089] Examples of aromatic ethers include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether, and naphthyl ether. The aromatic ether preferably has 7 or more carbon atoms, more preferably 8 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0090] The ether compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0091] Among the above ether compounds, aliphatic ethers are preferred, and dimethoxyethane and tetrahydrofuran are more preferred, from the viewpoint of obtaining higher ionic conductivity.

[0092] Examples of the ester compound include ester compounds such as aliphatic esters, alicyclic esters, heterocyclic esters, and aromatic esters, and these compounds may be used alone or in combination.

[0093] More specifically, examples of aliphatic esters include formate esters such as methyl formate, ethyl formate, and triethyl formate; acetate esters such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate; propionate esters such as methyl propionate, ethyl propionate, propyl propionate, and butyl propionate; oxalate esters such as dimethyl oxalate and diethyl oxalate; malonate esters such as dimethyl malonate and diethyl malonate; and succinate esters such as dimethyl succinate and diethyl succinate.

[0094] The number of carbon atoms in the aliphatic ester is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ester is preferably 1 or more, more preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0095] Examples of alicyclic esters include methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, dimethyl cyclohexanedicarboxylate, dibutyl cyclohexanedicarboxylate, and dibutyl cyclohexenedicarboxylate. Examples of heterocyclic esters include methyl pyridinecarboxylate, ethyl pyridinecarboxylate, propyl pyridinecarboxylate, methyl pyrimidinecarboxylate, ethyl pyrimidinecarboxylate, and lactones such as acetolactone, propiolactone, butyrolactone, and valerolactone.

[0096] The number of carbon atoms in the alicyclic ester and heterocyclic ester is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0097] Examples of aromatic esters include benzoic acid esters such as methyl benzoate, ethyl benzoate, propyl benzoate, and butyl benzoate; phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, and dicyclohexyl phthalate; and trimellitic acid esters such as trimethyl trimellitate, triethyl trimellitate, tripropyl trimellitate, tributyl trimellitate, and trioctyl trimellitate.

[0098] The aromatic ester preferably has 8 or more carbon atoms, more preferably 9 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0099] The ester compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0100] Among the above ester compounds, from the viewpoint of obtaining higher ionic conductivity, aliphatic esters are preferred, acetate esters are more preferred, and ethyl acetate is particularly preferred.

[0101] From the viewpoint of efficiently forming a complex, the molar ratio of the amount of complexing agent added to the total molar amount of lithium atoms contained in the raw material content (moles-additive / moles-total amount of lithium atoms) is preferably 0.1 or more and 10.0 or less, more preferably 0.5 or more and 8.0 or less, and even more preferably 0.8 or more and 5.0 or less.

[0102] (mixture) In the method (ii) for obtaining a reaction product, the above-mentioned solid electrolyte raw material is mixed with a complexing agent, and by mixing these, a complex composed of the solid electrolyte raw material and the complexing agent is obtained.

[0103] In this embodiment, the solid electrolyte raw material and the complexing agent may be mixed in either a solid or liquid form. However, since the solid electrolyte raw material contains a solid and the complexing agent is liquid, they are usually mixed in a form in which the solid solid electrolyte raw material is present in the liquid complexing agent. Furthermore, when mixing the raw material and the complexing agent, a solvent may be further mixed as needed. Hereinafter, in the description of mixing the raw material and the complexing agent, unless otherwise specified, the complexing agent is also considered to include a solvent added as needed.

[0104] There is no particular limitation on the method for mixing the solid electrolyte raw material and the complexing agent, and the solid electrolyte raw material and the complexing agent may be mixed by being charged into an apparatus capable of mixing them. For example, it is preferable to supply the complexing agent into a tank, operate the stirring blades, and then gradually add the solid electrolyte raw material, since this results in a good mixed state of the solid electrolyte raw material and improves the dispersibility of the raw material. However, when a halogen element is used as the solid electrolyte raw material, the solid electrolyte raw material may not be solid, specifically, fluorine and chlorine are gaseous, and bromine is liquid, at room temperature and normal pressure. In such a case, for example, when the solid electrolyte raw material is liquid, it may be supplied into the tank together with a complexing agent separately from other solid solid electrolyte raw materials, or when the solid electrolyte raw material is gas, it may be supplied by blowing into a mixture of the solid solid electrolyte raw material and the complexing agent.

[0105] In method (ii) for obtaining a reactant, it is sufficient to mix the solid electrolyte raw material and the complexing agent; pulverization is not required. Therefore, unlike method (i) above, it is not necessary to use equipment commonly referred to as a pulverizer, such as a media-type pulverizer such as a ball mill or a bead mill, which is used for pulverizing solid electrolyte raw materials. In the manufacturing method of this embodiment, simply mixing the solid electrolyte raw material and the complexing agent allows the solid electrolyte raw material and the complexing agent contained in the raw material content to mix and form a complex. Note that the mixture of raw material and complexing agent may be pulverized in a pulverizer to shorten the mixing time for obtaining the complex or to achieve finer powder, but as mentioned above, it is preferable not to use a pulverizer.

[0106] An example of an apparatus for mixing the solid electrolyte raw material and the complexing agent is a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers. High-speed agitation mixers are preferred from the viewpoint of improving the uniformity of the solid electrolyte raw material in the mixture of the solid electrolyte raw material and the complexing agent and achieving higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers. Either type of mixer may be used.

[0107] The shapes of the impellers used in mechanically stirred mixers include anchor, blade, arm, ribbon, multi-blade, double-arm, shovel, two-shaft blade, flat blade, and C-shaped blade. From the viewpoint of improving the uniformity of the solid electrolyte raw material and obtaining higher ionic conductivity, the shovel, flat blade, and C-shaped blade types are preferred. Furthermore, it is preferable to install a circulation line in a mechanically stirred mixer that discharges the material to be stirred outside the mixer and then returns it to the mixer. This allows for more uniform mixing without sedimentation or retention of heavy raw materials such as lithium halide.

[0108] The location of the circulation line is not particularly limited, but it is preferably installed at a location where it discharges from the bottom of the mixer and returns to the top of the mixer. This makes it easier to uniformly mix the solid electrolyte raw material, which tends to settle, by using convection caused by circulation. Furthermore, it is preferable that the return port is located below the liquid surface of the material to be mixed. This can prevent the material to be mixed from splashing and adhering to the wall surfaces inside the mixer.

[0109] The temperature conditions when mixing the solid electrolyte raw material and the complexing agent are not particularly limited and are, for example, −30 to 100° C., preferably −10 to 50° C., and more preferably about room temperature (23° C.) (for example, about room temperature ±5° C.) The mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining higher ionic conductivity, is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0110] By mixing the solid electrolyte raw materials with the complexing agent, a complex is formed between the solid electrolyte raw materials and the complexing agent. More specifically, the complex is considered to be formed by the interaction of the complexing agent with lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms contained in the solid electrolyte raw materials, which are directly bonded to each other with or without the intervention of the complexing agent. In other words, in method (ii) for obtaining a reactant, the complex obtained by mixing the solid electrolyte raw materials with the complexing agent can be said to be composed of the complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The complex obtained in the method (ii) for obtaining the reactant is not completely soluble in the liquid complexing agent but is usually a solid, so that a suspension of the complex is obtained in the complex and a solvent added as needed. Therefore, the method (ii) for obtaining the reactant corresponds to a heterogeneous system in the so-called liquid phase method.

[0111] (solvent) In the method (ii) for obtaining the reaction product, a solvent may be further added when the solid electrolyte raw material and the complexing agent are mixed. When a solid complex is formed in a liquid complexing agent, if the complex is easily soluble in the complexing agent, separation of the components may occur. Therefore, by using a solvent in which the complex is insoluble, the elution of the components in the complex can be suppressed. Furthermore, by mixing the solid electrolyte raw material and the complexing agent using a solvent, complex formation is promoted, allowing each main component to be more evenly present, and a complex is obtained in which the dispersion state of the solid electrolyte raw material, particularly the dispersion state of the halogen atoms, is uniformly maintained. As a result, the effect of obtaining high ionic conductivity is more easily achieved.

[0112] Method (ii) for obtaining the reactant is a so-called heterogeneous method, in which the complex is preferably precipitated rather than completely dissolved in the liquid complexing agent. The solubility of the complex can be adjusted by adding a solvent. Halogen atoms, in particular, tend to dissolve from the complex, so adding a solvent can suppress the dissolution of halogen atoms and obtain the desired complex. As a result, a sulfide solid electrolyte with high ionic conductivity can be easily obtained via a complex in which the solid electrolyte raw material, particularly the solid electrolyte raw material containing halogen atoms, is uniformly dispersed.

[0113] A preferred example of a solvent having such properties is a solvent having a solubility parameter of 10 or less. In this specification, the solubility parameter is a value δ ((cal / cm)) calculated by the following formula (1), which is described in various documents, such as "Chemical Handbook" (published in 2004, 5th revised edition, Maruzen Co., Ltd.). 3 ) 1 / 2 ) and is also called the Hildebrand parameter or SP value.

[0114]

number

[0115] By using a solvent with a solubility parameter of 10 or less, the solid electrolyte raw materials, particularly halogen atoms, halogen-containing raw materials such as lithium halide, and halogen-containing components constituting the complex (e.g., an aggregate formed by bonding lithium halide and the complexing agent), can be made relatively less soluble compared to the complexing agent. This makes it easier to fix halogen atoms in the complex, resulting in well-dispersed halogen atoms in the resulting sulfide solid electrolyte, making it easier to obtain a sulfide solid electrolyte with high ionic conductivity. In other words, the solvent used in method (ii) for obtaining the reactant preferably has the property of not dissolving the complex. From the same perspective, the solubility parameter of the solvent is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less.

[0116] More specifically, the solvent used in this embodiment can be a wide variety of solvents that have conventionally been used in the production of solid electrolytes. Examples of the solvent include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; solvents containing carbon atoms such as alcohol-based solvents, ester-based solvents, aldehyde-based solvents, ketone-based solvents, ether-based solvents having 4 or more carbon atoms on one side, and solvents containing carbon atoms and heteroatoms; and among these, a solvent may be appropriately selected from those preferably having a solubility parameter within the above-mentioned range.

[0117] More specifically, aliphatic hydrocarbon solvents such as hexane (7.3), pentane (7.0), 2-ethylhexane, heptane (7.4), octane (7.5), decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane (8.2) and methylcyclohexane; benzene, toluene (8.8), xylene (8.8), mesitylene, ethylbenzene (8.8), tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene (9.5), chlorotoluene (8.8), and bromobenzene. Examples of the solvents include aromatic hydrocarbon solvents such as ethanol (12.7) and butanol (11.4); aldehyde solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone solvents such as acetone (9.9) and methyl ethyl ketone; ether solvents such as dibutyl ether, cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and heteroatoms such as acetonitrile (11.9), dimethyl sulfoxide, and carbon disulfide. Note that the numbers in parentheses in the above examples are SP values. The above examples are merely examples, and for example, solvents having isomers may include all isomers. In addition, solvents substituted with halogen atoms, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents may also include solvents substituted with aliphatic groups such as alkyl groups.

[0118] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred, and from the viewpoint of obtaining more stable and high ionic conductivity, heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred, and diisopropyl ether and dibutyl ether are still more preferred, with cyclohexane being particularly preferred. The solvent used in the method (ii) for obtaining the reaction product is preferably the organic solvent exemplified above, and is an organic solvent different from the complexing agent. In the method (ii) for obtaining the reaction product, these solvents may be used alone or in combination.

[0119] (Heat to obtain decomposition products) The method (ii) for obtaining a reaction product includes heating the complex obtained by the above-mentioned mixing to obtain a decomposition product. The decomposition product is obtained by removing the complexing agent from the complex obtained by the above-mentioned mixing by heating, and as described above, can be called an amorphous sulfide solid electrolyte. The complex is formed by the solid electrolyte raw materials and the complexing agent, and by forming the complex, the solid electrolyte raw materials exist in close contact at the molecular level. Therefore, when the complexing agent is removed by heating, it is thought that the close-contact solid electrolyte raw materials bond with each other to form a sulfide solid electrolyte.

[0120] The heating temperature of the complex in the method (ii) for obtaining a reactant is not particularly limited as long as it is a temperature at which the complex can become a reactant, i.e., a temperature at which an amorphous sulfide solid electrolyte can be obtained. For example, the heating temperature can be determined based on the structure of the crystalline sulfide solid electrolyte obtained by heating the reactant (amorphous sulfide solid electrolyte).

[0121] More specifically, the reactant (amorphous sulfide solid electrolyte) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10°C / min, and the temperature is preferably set to 5°C or lower, more preferably 10°C or lower, and even more preferably 20°C or lower, starting from the temperature at the top of the exothermic peak observed at the lowest temperature. There is no particular lower limit, but the lower limit may be set to about -40°C or higher, which is the temperature at the top of the exothermic peak observed at the lowest temperature. By setting the temperature range in this way, the reactant (amorphous sulfide solid electrolyte) can be obtained more efficiently and reliably. The heating temperature for obtaining the reaction product (amorphous sulfide solid electrolyte) cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. There is no particular lower limit, but it is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher.

[0122] The heating time in method (ii) for obtaining a reaction product is not particularly limited as long as it is a time that allows the desired reaction product (amorphous sulfide solid electrolyte) to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0123] Furthermore, the heating in the method (ii) for obtaining the reaction product is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum), because this can prevent deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte. The heating method is not particularly limited, and examples thereof include a method using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a baking furnace, etc. Furthermore, industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. may also be used, and the method may be selected depending on the amount of processing to be heated.

[0124] (Dry) In method (ii) for obtaining a reactant, a complex is obtained by mixing the solid electrolyte raw material with a complexing agent. However, the complexing agent remains and does not contribute to the formation of the complex. If a solvent is used, the solvent also remains. That is, in method (ii), the mixture obtained by mixing the solid electrolyte raw material with the complexing agent is a mixture containing the complex, the remaining complexing agent, and the solvent used as needed (hereinafter, sometimes referred to as a "complex-containing mixture"). Therefore, the complex-containing mixture obtained by the above mixing may be dried before heating to remove the remaining complexing agent and solvent. This results in a powder of the complex. By drying the material in advance, it becomes possible to efficiently perform heating. Note that drying and subsequent heating may be performed in the same step.

[0125] The complex-containing material can be dried at a temperature that depends on the type of remaining complexing agent (complexing agent not incorporated into the complex) and the type of solvent used if necessary, i.e., at a temperature equal to or higher than the boiling points of the complexing agent and solvent. Specific drying conditions cannot be generalized because they vary depending on the types of complexing agent and solvent. However, drying can be performed by drying under reduced pressure (vacuum drying) using a vacuum pump or the like at a temperature of typically 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably at about room temperature (23°C) (for example, about room temperature ±5°C) to volatilize the complexing agent and solvent.

[0126] The drying may be carried out by filtering the complex-containing material using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifuge, etc. Alternatively, for example, after solid-liquid separation, drying may be carried out under the above-mentioned temperature conditions.

[0127] Specifically, solid-liquid separation can be easily performed by decantation, in which a complex-containing substance is transferred to a container, and after the complex has precipitated, the complexing agent and solvent that form the supernatant are removed, or by filtration using, for example, a glass filter with a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0128] Although drying has been described as a treatment in the method (ii) for obtaining a reaction product, for example, when a solvent is used in mixing in a grinder in the method (i) for obtaining a reaction product, drying may be performed to remove the solvent.

[0129] (Reactants) The reaction product obtained by obtaining the above reaction product is an amorphous sulfide solid electrolyte. The amorphous solid electrolyte reactant contains lithium, sulfur, phosphorus, and halogen atoms. Representative examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiS-PS-LiI, LiS-PS-LiCl, LiS-PS-LiBr, and LiS-PS-LiI-LiBr; and solid electrolytes further containing other atoms such as oxygen and silicon, such as LiS-PS-LiO-LiI and LiS-SiS-PS-LiI. From the viewpoint of obtaining higher ionic conductivity, preferred examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiS-PS-LiI, LiS-PS-LiCl, LiS-PS-LiBr, and LiS-PS-LiI-LiBr. The types of atoms constituting the amorphous solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0130] When the reactant, which is an amorphous solid electrolyte, contains at least Li2S-P2S5, the molar ratio of Li2S to P2S5 is preferably 65-85:15-35, more preferably 70-80:20-30, and even more preferably 72-78:22-28, from the viewpoint of obtaining higher ionic conductivity.

[0131] When the reactant that is the amorphous solid electrolyte is, for example, Li2S-P2S5-LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0132] In the reactant which is an amorphous solid electrolyte, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.6, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.05-0.5, and even more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.08-0.4. Furthermore, when bromine and iodine are used in combination as halogen atoms, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine, and iodine is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.02-0.25:0.02-0.25, more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.03-0.2:0.03-0.2, and even more preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a crystalline solid electrolyte having a thiolithium region II crystal structure described later and having higher ionic conductivity. Furthermore, the compounding ratio (molar ratio) in the crystalline product (crystalline solid electrolyte) described later is within the above compounding ratio (molar ratio) range of the reactant, which is the amorphous solid electrolyte, and when the reactant is heated to obtain the crystalline product, the compounding ratio (molar ratio) of the reactant and the crystalline product is the same.

[0133] [Heating to obtain a crystalline product] The production method of this embodiment includes obtaining the above-mentioned reaction product, and then heating the obtained reaction product to obtain a crystalline product. By heating the reaction product, crystallization of the reaction product progresses and the crystalline product is obtained.

[0134] The heating temperature is not particularly limited as long as it promotes crystallization of the reactant and produces a crystalline product. For example, the heating temperature may be determined depending on the structure of the crystalline product obtained by heating the reactant. Specifically, the reactant is subjected to differential thermal analysis (DTA) at a heating rate of 10 °C / min using a differential thermal analyzer (DTA). The temperature is preferably set to 5 °C or higher, more preferably 10 °C or higher, and even more preferably 20 °C or higher, starting from the peak top temperature of the exothermic peak observed at the lowest temperature. The upper limit is not particularly limited, but it should be about 40 °C or lower. By setting the temperature range in this way, not only can the crystallization of the reactant proceed more efficiently and reliably to produce a crystalline product, but the content of the complexing agent remaining in the crystalline product and the solvent used if necessary can be reduced. Furthermore, by reducing the content of the reactant, the purity of the crystalline product can be improved. As a result, the purity of the crystalline sulfide solid electrolyte obtained by the production method of this embodiment can be improved.

[0135] The heating temperature cannot be generally defined because it varies depending on the structure of the crystalline product to be obtained, but is generally preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. There is no particular upper limit, but the temperature is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0136] The heating time is not particularly limited as long as the desired crystalline product is obtained, but is preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0137] In obtaining a crystalline product by heating, the heating can be carried out at normal pressure, but can also be carried out under reduced pressure or even under vacuum in order to reduce the heating temperature. When heating is performed under a reduced pressure, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less, and the lower limit may be a vacuum (0 kPa). In consideration of ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more. When the pressure is within the above range, the heating conditions can be made mild, and the apparatus can be prevented from becoming large.

[0138] Furthermore, the heating is preferably carried out in an inert gas atmosphere (for example, a nitrogen atmosphere or an argon atmosphere), since this can prevent deterioration (for example, oxidation) of the crystalline product. The heating method is not particularly limited, and examples thereof include a method using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a baking furnace, etc. Furthermore, industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. may also be used, and the method may be selected depending on the amount of processing to be heated.

[0139] When the method (ii) for obtaining the reaction product is adopted, the complex is heated to obtain a decomposition product, but the decomposition product (i.e., the reaction product) may be converted into a crystalline product by further heating following the heating for obtaining the decomposition product. In this case, too, the crystalline product is produced from the complex via the decomposition product (reaction product), and therefore can be said to be obtained by obtaining the reaction product and then heating to obtain the crystalline product.

[0140] (crystalline product) The crystalline product obtained by heating the reaction product can be said to be a crystalline sulfide solid electrolyte having a crystalline structure. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is obtained by pulverizing the crystalline product using a specific integrated power, and has the crystalline structure of the crystalline product. Therefore, the crystalline structure described below as having the crystalline product is also the crystalline structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment.

[0141] The crystalline product may have a crystal structure such as Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0142] The crystalline structure of the crystalline product is Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li 4-x Ge 1-x P x Examples include a crystal structure similar to the S4-type thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725).

[0143] The crystal structure of the crystalline product is preferably a thiolicon region II crystal structure, since this structure provides higher ionic conductivity. 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure, Li 4-x Ge 1-x Px This indicates that the crystal structure is either S4-type thio-LISICON Region II type or similar.

[0144] The crystalline product may contain the thiolicon region II crystal structure or may contain it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystalline product does not contain crystalline Li3PS4 (β-Li3PS4).

[0145] In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and the diffraction peaks of the Li7P3S 11 Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°. 4-x Ge 1-x P x The diffraction peaks of the S4 thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x Diffraction peaks of a crystal structure similar to the S4 thio-LISICON Region II type appear, for example, at 2θ = 20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0146] As the crystal structure of the crystalline product, an alluaudite-type crystal structure having the above-described structural framework of Li7PS6 and in which part of P is substituted with Si is also preferably mentioned. Examples of the composition formula of the alluaudite-type crystal structure include the composition formula Li 7-x P 1-y Si y S6 and Li 7+x P 1-y Si y S6 (where x is -0.6 to 0.6 and y is 0.1 to 0.6). The alluaudite-type crystal structure represented by this composition formula is cubic or orthorhombic, preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0147] Examples of the composition formula of the alluaudite-type crystal structure include the composition formula Li<00,00033>PS 6-x-y Cl x (0.8 ≤ x ≤ 1.7, 0 < y ≤ -0.25x + 0.5) is also included. The alluaudite-type crystal structure represented by this composition formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. In addition, examples of the composition formula of the alluaudite-type crystal structure include the composition formula Li 7-x PS 6-x Ha x (where Ha is Cl or Br, and x is preferably 0.2 to 1.8) is also included. The alluaudite-type crystal structure represented by this composition formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Note that these peak positions may shift within a range of ±0.5°.

[0148] <00006,67>[Amorphizing at least a portion of the surface of the crystalline product] The manufacturing method of this embodiment includes pulverizing the crystalline product obtained by the heating to amorphize at least a portion of the surface of the crystalline product. The pulverization process requires an integrated power of 1 (Wh / kg) or more and 500 (Wh / kg) or less. As described above, pulverizing the crystalline product at a specific integrated power can amorphize at least a portion of its surface.

[0149] (cumulative power) In the manufacturing method of this embodiment, it is important that the integrated power of the pulverization treatment is 1 (Wh / kg) or more and 500 (Wh / kg) or less. If the integrated power is less than 1 (Wh / kg), amorphization is insufficient, and the properties of the amorphous sulfide solid electrolyte, i.e., excellent oxidation resistance, cannot be obtained. On the other hand, if the integrated power is greater than 500 (Wh / kg), amorphization is not limited to at least a portion of the surface, and the crystalline product is entirely amorphized, making it impossible to obtain high ionic conductivity.

[0150] The integrated power in the manufacturing method of this embodiment can be calculated as follows. (How to calculate cumulative power) The cumulative energy E (unit: Wh / kg) can be calculated using the following formula, where P0 (unit: W) is the average air power of each machine when not including the crystalline product (the material to be crushed), P (unit: W) is the average instantaneous power required to process the crystalline product in each machine, t (unit: h) is the total processing time, and M (unit: kg) is the total weight of the crystalline product to be processed. E=(P-P0)×t / M

[0151] From the viewpoint of improving oxidation resistance and obtaining high ionic conductivity, the integrated power of the pulverization treatment is preferably 5 (Wh / kg) or more, more preferably 10 (Wh / kg) or more, and even more preferably 25 (Wh / kg) or more, with the upper limit being preferably 450 (Wh / kg) or less, more preferably 400 (Wh / kg) or less, and even more preferably 350 (Wh / kg) or less. Furthermore, if the integrated power is within the above range, it is also possible to suppress granulation, an increase in the specific surface area, and a significant decrease in ionic conductivity.

[0152] (Crushing process) The crystalline product may be crushed using any equipment capable of crushing, and is preferably crushed using a crusher. As the pulverizer, the pulverizers described as devices capable of mixing the solid electrolyte raw materials in the method (i) for obtaining the reaction product are preferably used. Among the pulverizers, ball mills and bead mills exemplified as container-driven pulverizers are preferred, and planetary mills are particularly preferred, since they facilitate adjustment of the integrated power and facilitate amorphization.

[0153] When a ball mill or a bead mill is used, the size and material of the beads and balls are the same as those explained for the grinding machine that can be used when mixing the solid electrolyte raw materials. Furthermore, when a ball mill or a bead mill is used, the operating conditions, i.e., the rotation speed and grinding time, are not particularly limited as long as they are within the range of the integrated power, and may be appropriately selected from the rotation speed and grinding time described for the grinder that can be used when mixing the solid electrolyte raw materials.

[0154] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the production method of this embodiment has an amorphous portion on at least a part of its surface. In the manufacturing method of this embodiment, a crystalline sulfide solid electrolyte having a desired crystal structure can be obtained by adjusting the type and amount of solid electrolyte raw material contained in the raw material inclusions. The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is the same as the crystal structure of the crystalline product as described above, and preferred examples include the crystal structures described as possible crystal structures of the crystalline product. Among these, the thiolicon region II crystal structure is preferred because of its high ionic conductivity.

[0155] The shape of the crystalline solid electrolyte obtained by the production method of this embodiment is not particularly limited, but may be, for example, particulate. The average particle size (D 50 ) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 5 μm or less, further 3.0 μm or less, 1.5 μm or less, or 1.0 μm or less. According to the production method of this embodiment, it is possible to suppress granulation and an increase in the specific surface area, and therefore the average particle size of the crystalline sulfide solid electrolyte is small enough to be used in subsequent applications (e.g., electrode composites, lithium ion batteries).

[0156] The ionic conductivity of the crystalline solid electrolyte obtained by the manufacturing method of this embodiment is 1.5 × 10 -3 S / cm or more, and even 1.7 × 10 -3 S / cm or more, 1.9×10 -3 S / cm or more. According to the manufacturing method of this embodiment, a significant decrease in ionic conductivity can be suppressed, and therefore, it can be said that the ionic conductivity of the crystalline sulfide solid electrolyte is high. Here, in this specification, the ionic conductivity is measured by the method described in the Examples.

[0157] The oxidation current of the crystalline solid electrolyte obtained by the production method of this embodiment is approximately the same as that of the amorphous sulfide solid electrolyte, that is, is smaller than the oxidation current of the crystalline sulfide solid electrolyte, and therefore excellent oxidation resistance can be obtained. The oxidation current reduction rate of the crystalline solid electrolyte obtained by the production method of this embodiment is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and even more preferably 25% or more. Here, the oxidation current reduction rate is calculated by the following formula. In other words, the oxidation current reduction rate can also be said to be the rate of reduction from the oxidation current before amorphizing at least a portion of the surface of the crystalline product to the oxidation current after amorphization.

[0158] Reduction rate of oxidation current (%) = (oxidation current 2 - oxidation current 1) / oxidation current 2 x 100 Oxidation current 1: Oxidation current of a crystalline sulfide solid electrolyte having an amorphized portion on at least a portion of its surface (oxidation current of a crystalline sulfide solid electrolyte obtained by amorphizing at least a portion of the surface of a crystalline product) (mA) Oxidation current 2: Oxidation current of the former crystalline sulfide solid electrolyte having at least a part of the surface amorphous (oxidation current of the crystalline product) (mA)

[0159] Furthermore, the oxidation current of the crystalline solid electrolyte obtained by the production method of this embodiment cannot be generally stated as an absolute value because it may vary depending on the measurement conditions, etc., but when measured by the oxidation current measurement method in the examples described below, it is preferably 0.45 mA or less, more preferably 0.40 mA or less, and even more preferably 0.38 mA or less.

[0160] [Crystalline sulfide solid electrolyte] The crystalline sulfide solid electrolyte of this embodiment is A crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, The crystalline sulfide solid electrolyte has an amorphous portion on at least a part of its surface. crystalline sulfide solid electrolyte, That is it.

[0161] The sulfide solid electrolyte of this embodiment can be produced by the above-described production method of this embodiment, and from the viewpoint of more efficient production, it is preferable to produce it by the above-described production method of this embodiment. That is, the crystalline sulfide solid electrolyte of this embodiment is a crystalline sulfide solid electrolyte having excellent oxidation resistance, high ionic conductivity, and suppressed granulation and increase in specific surface area.

[0162] The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. These atoms are derived from the solid electrolyte raw material contained in the raw material inclusions used in the production method of this embodiment.

[0163] The crystalline sulfide solid electrolyte of this embodiment has an amorphous portion on at least a part of its surface. The presence of the amorphous portion and the form of the amorphous portion are the same as those described above for the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment. In addition, other properties, such as the crystal structure that the electrolyte may have, ionic conductivity, average particle size, oxidation current measured by cyclic voltammetry measurement (CV measurement) and its rate of decrease, are the same as those described for the crystalline sulfide solid electrolyte obtained by the manufacturing method of the present embodiment.

[0164] (Application) The crystalline sulfide solid electrolyte of the present embodiment has excellent oxidation resistance while suppressing granulation, an increase in specific surface area, and a significant decrease in ionic conductivity, and is therefore suitable for use in electrode mixtures, lithium ion batteries, and the like. When used in a lithium ion battery, the composite may be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer of the lithium ion battery, and each layer can be produced by a known method.

[0165] The lithium ion battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and a known current collector can be used. For example, a layer of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used.

[0166] [Electrode composite material] The electrode mixture of this embodiment uses the crystalline sulfide solid electrolyte of this embodiment described above, and is an electrode mixture containing the crystalline sulfide solid electrolyte of this embodiment described above and an electrode active material.

[0167] (electrode active material) As the electrode active material, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode mixture is used for the positive electrode or the negative electrode.

[0168] The positive electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions due to atoms that are used to exhibit ionic conductivity, preferably lithium atoms, in relation to the negative electrode active material. Examples of such positive electrode active materials that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0169] Preferred examples of oxide-based positive electrode active materials include lithium-containing transition metal composite oxides such as LMO (lithium manganese oxide), LCO (lithium cobalt oxide), NMC (lithium nickel manganese cobalt oxide), NCA (lithium nickel cobalt aluminate), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO4, Me=Fe, Co, Ni, Mn). Examples of sulfide-based positive electrode active materials include titanium sulfide (TiS2), molybdenum sulfide (MoS2), iron sulfide (FeS, FeS2), copper sulfide (CuS), and nickel sulfide (Ni3S2). In addition to the above positive electrode active materials, niobium selenide (NbSe3) and the like can also be used. The positive electrode active material can be used alone or in combination of two or more kinds.

[0170] The negative electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions originating from lithium atoms, such as an atom that is used as an atom to exhibit ionic conductivity, preferably a metal that can form an alloy with lithium atoms, an oxide thereof, an alloy of the metal with lithium atoms, etc. As such a negative electrode active material capable of inserting and extracting lithium ions, any material known in the field of batteries as a negative electrode active material can be used without any limitation. Examples of such negative electrode active materials include metallic lithium, metallic indium, metallic aluminum, metallic silicon, metallic tin, and other metallic lithium or metals capable of forming alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0171] The electrode active material may have a coating layer on its surface. The material for forming the coating layer is an ion conductor such as an atom that exhibits ionic conductivity in the crystalline sulfide solid electrolyte, preferably a nitride or oxide of lithium atoms, or a composite thereof. Specifically, lithium nitride (Li3N), Li4GeO4, and the like, which have a main structure, for example, Li 4-2x Zn x Conductors with a lithiated crystal structure such as GeO4, and those with a Li3PO4-type framework structure such as Li 4-x Ge 1-x P x Conductors with thiolicon-type crystal structures such as S4, La 2 / 3-x Li 3x Examples include conductors having a perovskite crystal structure such as TiO3, and conductors having a NASICON crystal structure such as LiTi2(PO4)3. Also, Li y Ti 3-y O4(0 <y<3)、Li4Ti5O 12Examples include lithium titanates such as (LTO), lithium metal oxides of metals belonging to Group 5 of the periodic table such as LiNbO3 and LiTaO3, and oxide-based conductors such as Li2O-B2O3-P2O5, Li2O-B2O3-ZnO, and Li2O-Al2O3-SiO2-P2O5-TiO2.

[0172] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various atoms constituting the material that forms the coating layer to the surface of the electrode active material, and then firing the electrode active material after application at a temperature preferably between 200°C and 400°C. Here, the solution containing various atoms may be a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, tantalum isopropoxide, etc. In this case, the solvent may be an alcoholic solvent such as ethanol or butanol, an aliphatic hydrocarbon solvent such as hexane, heptane or octane, or an aromatic hydrocarbon solvent such as benzene, toluene or xylene. The above-mentioned attachment may be carried out by immersion, spray coating or the like.

[0173] From the viewpoint of improving production efficiency and battery performance, the firing temperature is preferably 200°C or higher and 400°C or lower, more preferably 250°C or higher and 390°C or lower, and the firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0174] The coverage of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100% of the surface area of ​​the electrode active material, i.e., the entire surface is covered. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less. The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage rate can be calculated from the thickness of the coating layer, elemental analysis values, and BET specific surface area.

[0175] (Other ingredients) The electrode mixture of this embodiment may contain, in addition to the above-mentioned crystalline sulfide solid electrolyte and electrode active material, other components such as a conductive material, a binder, etc. That is, the electrode mixture of this embodiment may use, in addition to the above-mentioned sulfide solid electrolyte and electrode active material, other components such as a conductive material, a binder, etc. The other components such as a conductive material, a binder, etc. may be added to and mixed with the sulfide solid electrolyte and the electrode active material when the sulfide solid electrolyte and the electrode active material are mixed together. Examples of the conductive material, from the viewpoint of improving battery performance by improving electronic conductivity, include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0176] By using a binder, the strength of the positive electrode and the negative electrode when they are fabricated is improved. The binder is not particularly limited as long as it can impart functions such as binding property and flexibility, and examples thereof include fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, thermoplastic elastomers such as butylene rubber and styrene-butadiene rubber, and various resins such as acrylic resin, acrylic polyol resin, polyvinyl acetal resin, polyvinyl butyral resin, and silicone resin.

[0177] In order to improve battery performance and take production efficiency into consideration, the compounding ratio (mass ratio) of the electrode active material to the sulfide solid electrolyte in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40.

[0178] When a conductive material is contained, the content of the conductive material in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more, and the upper limit is preferably 10 mass% or less, preferably 8 mass% or less, and even more preferably 5 mass% or less. Furthermore, when a binder is contained, the content of the binder in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, with the upper limit being preferably 20 mass % or less, preferably 15 mass % or less, and even more preferably 10 mass % or less.

[0179] [Lithium-ion battery] The lithium ion battery of this embodiment is a lithium ion battery including at least one selected from the crystalline sulfide solid electrolyte of this embodiment and the electrode mixture.

[0180] The lithium ion battery of this embodiment is not particularly limited in its configuration as long as it contains the sulfide solid electrolyte of this embodiment and an electrode composite containing the sulfide solid electrolyte, and has the configuration of a commonly used lithium ion battery.

[0181] The lithium ion battery of this embodiment preferably includes, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. The positive electrode layer and the negative electrode layer preferably use an electrode mixture using the crystalline sulfide solid electrolyte of this embodiment, and the electrolyte layer preferably uses the crystalline sulfide solid electrolyte of this embodiment.

[0182] The current collector may be a known material, for example, a layer of Au or the like coated with a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu. [Example]

[0183] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0184] (Powder XRD diffraction measurement) Powder X-ray diffraction (XRD) measurements were carried out as follows. The sulfide solid electrolyte powders obtained in the examples and comparative examples were filled into a groove 20 mm in diameter and 0.2 mm deep, and leveled with glass to prepare a sample. This sample was sealed in Kapton film for XRD and measured under the following conditions without exposing it to air. Measurement equipment: D2 PHASER, manufactured by Bruker Tube voltage: 30kV Tube current: 10mA X-ray wavelength: Cu-Kα ray (1.5418Å) Optical system: Concentration method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) Detector: Semiconductor detector Measurement range: 2θ=10-60deg Step width, scan speed: 0.05deg, 0.05deg / sec

[0185] (Measurement of ionic conductivity) In this example, the ionic conductivity was measured as follows. From the crystalline solid electrolytes obtained in the examples and comparative examples, a 10 mm diameter (cross-sectional area S: 0.785 cm 2 ) and a height (L) of 0.1 to 0.3 cm were molded into circular pellets to serve as samples. Electrode terminals were attached to the top and bottom of the samples, and measurements were made at 25°C using the AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV). A Cole-Cole plot was obtained. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following equation: R=ρ(L / S) σ=1 / ρ

[0186] (Measurement of average particle size) The particle size distribution was obtained by measuring using a laser diffraction / scattering particle size distribution analyzer (Partica LA-950 (model number), manufactured by Horiba, Ltd.). When the cumulative curve of the obtained particle size distribution was drawn, the particle size at which the particle size reached 50% (volume basis) of the total particle size was calculated sequentially from the smallest particle size. The average particle size (D50 ) was decided.

[0187] (CV measurement (oxidation current)) To evaluate the oxidation current, the following CV measurement cell was used. A total of 100 mg of the powder obtained in the example and granular Denka Black (particle size: 35 nm, manufactured by Denka Co., Ltd.) (powder: Denka Black (mass ratio) = 85:15) was mixed in a mortar for 10 minutes to obtain powder (1) for measurement. 100 mg of electrolyte for the separator layer was added to a 10 mm diameter battery cell, and the cell was pressurized in a stainless steel mold at 10 MPa / cm 2 After pressing three times while rotating by 120° at a pressure of 20 MPa / cm, 10 mg of powder (1) was added. 2 Then, the powder (1) was pressed three times with a pressure of 20 MPa / cm from the opposite side of the powder (1). 2 The press was performed three times, rotating the press by 120° each time.

[0188] The electrolyte for the separator was synthesized under the following conditions. A 1-L reactor equipped with a stirring blade was charged with 20.5 g of Li2S, 33.1 g of P2S5, 10.0 g of LiI, and 6.5 g of LiBr under a nitrogen atmosphere. After rotating the stirring blade, 630 g of toluene was added, and the slurry was stirred for 10 minutes. The reactor was connected to a recirculating bead mill ("Star Mill LMZ015 (trade name)" manufactured by Ashizawa Finetech Co., Ltd., bead material: zirconia, bead diameter: 0.5 mm, bead amount: 456 g), and milling was performed for 45 hours (pump flow rate: 650 mL / min, bead mill peripheral speed: 12 m / s, mill jacket temperature: 45 °C). The obtained slurry was dried under vacuum at room temperature (25°C) and then heated (80°C) to obtain a white powder of amorphous solid electrolyte. The obtained white powder was further heated under vacuum at 195°C for 2 hours to obtain a white powder of crystalline solid electrolyte. In the XRD spectrum of the crystalline solid electrolyte, crystallization peaks were detected at 2θ = 20.2° and 23.6°, confirming that it had a thiolicon region II crystal structure. In addition, the average particle size (D50 ) was 4.5 μm and the ionic conductivity was 5.0 mS / cm.

[0189] An InLi foil (having a layered structure, " / " indicates the space between each layer. In: 10mmφ×0.1mm / Li: 9mmφ×0.08mm / SUS: 10mmφ×0.1mm) was placed on the opposite side of the electrolyte measurement powder (1) for the separator layer, and a pressure of 6 MPa / cm was applied. 2 The cell was fixed with four screws with an insulator between them to prevent a short circuit between the powder (1) and the InLi foil, and the screws were fixed with a torque of 8 N m to obtain the measurement cell.

[0190] The obtained measurement cell was connected to a measuring instrument (VMP-300 (model number), manufactured by Biologic), and a CV curve was obtained under the following conditions. Measurement temperature: 25℃ Sweep speed: 0.1mV / s Potential measurement range: Open circuit voltage (+2.1V) → +5.0V → +2.1V Number of cycles: 2

[0191] Example 1 A 100 mL Schlenk flask equipped with a stirrer was charged with a solid electrolyte starting material containing 0.59 parts by mass of lithium sulfide, 0.95 parts by mass of diphosphorus pentasulfide, 0.19 parts by mass of lithium bromide, and 0.28 parts by mass of lithium iodide under a nitrogen atmosphere. After rotating the stirrer, the complexing agent tetramethylethylenediamine (TMEDA) was added in a ratio of 4.45 molar parts per 0.133 molar parts of lithium atoms contained in the starting material (i.e., 4.45 molar parts TMEDA / molar parts lithium atoms) (20 mL per 2.0 g of total solid electrolyte starting material). Stirring was continued for 12 hours to obtain a complex. This was dried under vacuum (room temperature: 23°C) to obtain a powdered complex. The complex powder was then heated under vacuum at 120°C for 2 hours to remove the complexing agent from the complex, yielding a decomposition product. The decomposition product of the complex corresponds to a reaction product obtained by mixing raw material components containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The resulting reaction product was heated at 200°C for 2 hours under vacuum to obtain a crystalline product (the heating temperature (200°C in this example) required to obtain a crystalline sulfide solid electrolyte is the "crystallization temperature"). Next, 80 g of the resulting crystalline product was placed in a vessel equipped with a stirring blade, and 740 mL of heptane and 110 mL of diisopropyl ether (DiPE) were added. The mixture was stirred for 10 minutes to obtain a slurry. The resulting slurry was then ground for 5 minutes using a circulation-operated bead mill ("Labostar Mini LMZ015" manufactured by Ashizawa Finetech Co., Ltd.) under the specified conditions: bead diameter: 0.3 mm, bead usage: 456 g (bead filling volume relative to the milling chamber: 80%), pump flow rate: 400 mL / min, peripheral speed: 6 m / s. The pulverized slurry was then dried under vacuum at room temperature (23°C) to obtain a crystalline sulfide solid electrolyte. The integrated power consumption during the pulverization process was 140 (Wh / kg).

[0192] The average particle size (D 50 The ionic conductivities of the crystalline product and the crystalline sulfide solid electrolyte were measured and found to be 4.3 (mS / cm) and 3.7 (mS / cm), respectively.

[0193] The resulting powders of the reaction product, crystalline product, and crystalline sulfide solid electrolyte were subjected to XRD measurement, and the results are shown in Figure 1. Furthermore, the resulting reaction product, crystalline product, and crystalline sulfide solid electrolyte powder were subjected to CV measurement (oxidation current measurement) according to the above-mentioned method, and the results are shown in FIG.

[0194] (Comparative Example 1) The crystalline sulfide solid electrolyte obtained in Example 1 was again heated in vacuum at 200°C for 2 hours. The obtained powder was subjected to CV measurement (oxidation current measurement) according to the above-mentioned method. The results are shown in Figure 2.

[0195] From the results in FIG. 1, it was confirmed that the reaction product obtained in the example exhibited a halo pattern and was an amorphous sulfide solid electrolyte. In addition, the crystalline product obtained in the examples and the sulfide solid electrolyte obtained by pulverizing the crystalline product both had crystallization peaks detected mainly at 2θ = 20.2 °, 23.6 °, and 29.5 °, confirming that they were crystalline sulfide solid electrolytes having a thiolicon region II crystal structure. However, the peak intensity of the sulfide solid electrolyte obtained by pulverizing the crystalline product was smaller than the peak intensity of the crystalline product, confirming that the crystalline structure was reduced and at least a portion of its surface was amorphized.

[0196] From the results in FIG. 2, it was confirmed that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment had an oxidation current of 0.36 mA, which was small compared to the 0.34 mA of the reactant (amorphous sulfide solid electrolyte), and that the crystalline sulfide solid electrolyte had excellent oxidation resistance despite being a crystalline sulfide solid electrolyte. On the other hand, the oxidation current of the crystalline product in Example 1 was 0.51 mA, which was extremely large compared to the sulfide solid electrolyte obtained by pulverizing the reactant and the crystalline product, and it was confirmed that the crystalline product did not have oxidation resistance. Furthermore, in Comparative Example 1, the crystalline sulfide solid electrolyte obtained in Example 1 was heated to crystallize the amorphous portion present on at least a portion of the surface, and the powder had an oxidation current of 0.46 mA, which was larger than the crystalline sulfide solid electrolyte obtained in Example 1 but slightly smaller than the oxidation current of the crystalline product in Example 1. This is thought to be due to the effect of some amorphous portions remaining. [Industrial Applicability]

[0197] According to the method for producing a crystalline sulfide solid electrolyte of the present embodiment, it is possible to provide a crystalline sulfide solid electrolyte having excellent oxidation resistance while suppressing granulation, an increase in specific surface area, and a significant decrease in ionic conductivity. The crystalline sulfide solid electrolyte of this embodiment obtained by the production method of this embodiment is an electrode mixture or a lithium ion battery, particularly a personal computer, a video camera, a mobile phone, and other information-related equipment and communication equipment. It is suitable for use in lithium ion batteries.

Claims

1. A reaction product is obtained by mixing raw material containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Heating the reactants to obtain a crystalline product, and The crystalline product is subjected to a grinding treatment to make at least a portion of the surface of the crystalline product amorphous. Includes, The cumulative power used in the aforementioned crushing process is 1 (Wh / kg) or more and 500 (Wh / kg) or less. A method for producing crystalline sulfide solid electrolytes.

2. The method for producing a crystalline sulfide solid electrolyte according to claim 1, wherein the mixing is performed using a pulverizer to obtain the reactant.

3. To obtain the aforementioned reaction product, A complex is obtained by mixing the raw material components in the presence of a complexing agent, and The complex is heated to obtain a complex decomposition product. A method for producing a crystalline sulfide solid electrolyte according to claim 1, comprising:

4. The method for producing a crystalline sulfide solid electrolyte according to claim 1 or 2, wherein the crystalline sulfide solid electrolyte is a sulfide solid electrolyte having a thiolysicon region type II crystal structure.

5. A crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, The crystalline sulfide solid electrolyte has an amorphous portion on at least a part of its surface. Crystalline sulfide solid electrolyte.

6. The crystalline sulfide solid electrolyte according to claim 5, wherein the rate of decrease of the oxidation current measured by cyclic voltammetry (CV measurement), calculated by the following formula, is 10% or more. The rate of decrease in oxidation current (%) = (oxidation current 2 - oxidation current 1) / oxidation current 2 × 100 Oxidation current 1: Oxidation current (mA) of a crystalline sulfide solid electrolyte having an amorphous portion on at least part of its surface. Oxidation current 2: Oxidation current (mA) of a crystalline sulfide solid electrolyte having an amorphous portion on at least part of its surface.

7. The crystalline sulfide solid electrolyte according to claim 5 or 6, wherein the crystalline sulfide solid electrolyte is a sulfide solid electrolyte having a thiolysicon region type II crystal structure.

8. An electrode mixture comprising a crystalline sulfide solid electrolyte and an electrode active material as described in claim 5.

9. A lithium-ion battery comprising at least one of the crystalline sulfide solid electrolyte described in claim 5 or 6 and the electrode composite material described in claim 8.

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