Method for producing solid sulfide electrolyte

Abstract

To provide: a method for producing a solid sulfide electrolyte in which hydrogen sulfide gas is prevented from being generated even when the solid sulfide electrolyte comes into contact with moisture, while preventing a decrease in ionic conductivity; the solid sulfide electrolyte; an electrode composite including the solid sulfide electrolyte; and a lithium ion battery.SOLUTION: A method for producing a solid sulfide electrolyte includes mixing a raw material-containing product containing two or more raw materials, wherein: the raw material contains at least one selected from a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom; and the raw material-containing product contains the modified P2S5. A solid sulfide electrolyte produced by the method, an electrode composite, a lithium ion battery, and modified P2S5 for producing the solid sulfide electrolyte are also provided.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a sulfide solid electrolyte.

Background Art

[0002] As a solid electrolyte layer of a lithium-ion battery, use of a sulfide solid electrolyte using phosphorus pentasulfide (P2S5) or the like as a starting material has been studied. Although this sulfide solid electrolyte has high lithium ion conductivity (hereinafter, also simply referred to as ion conductivity), it easily reacts with water (hereinafter, also including moisture) and oxygen, and particularly generates hydrogen sulfide (H2S) gas when contacting water. Therefore, it is required to reduce the generation amount of H2S gas. Further, these lithium-ion batteries also have a problem that the adhesiveness between solid particles such as a solid electrolyte is low. In contrast, in Patent Document 1, an organic compound group is covalently supported on the surface of inorganic solid electrolyte particles or the like to improve the binding property.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 describes a solid electrolyte in which organic compound groups are uniformly supported on its surface by covalent bonds. However, the method described in Patent Document 1 generates by-products such as Li salts, which cannot be removed, thus inhibiting ion conduction and potentially degrading battery performance. Furthermore, in order to support the organic compound groups, the solid electrolyte undergoes surface treatment or moisture exposure beforehand, making it difficult to maintain ionic conductivity. Thus, there are both advantages and disadvantages to the technology of supporting groups derived from organic compounds on the surface of solid electrolyte particles, and it has been difficult to achieve a good balance of all the desired performance characteristics.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a sulfide solid electrolyte that suppresses the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with water, while suppressing a decrease in ionic conductivity, and to provide the sulfide solid electrolyte itself, and further to provide an electrode mixture containing the sulfide solid electrolyte, a lithium-ion battery, and a modified P2S5 for producing a sulfide solid electrolyte comprising an organic group. [Means for solving the problem]

[0006] The present invention relates to a method for producing a sulfide solid electrolyte, comprising mixing a raw material-containing material comprising two or more raw materials, wherein the raw materials comprise at least one selected from lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and the raw material-containing material comprises modified P2S5. The sulfide solid electrolyte according to the present invention contains lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups, and the ratio of the content (moles) of sulfur atoms, phosphorus atoms, and halogen atoms per (mol) of lithium atoms is lithium atoms:sulfur atoms:phosphorus atoms:halogen atoms = 1:1.1000~1.2000:0.2000~0.3500:0.1400~0.1550.

[0007] The electrode mixture according to the present invention is an electrode mixture containing the sulfide solid electrolyte and an electrode active material. The lithium-ion battery according to the present invention is a lithium-ion battery comprising at least one of the sulfide solid electrolyte and the electrode composite material. Furthermore, the modified P2S5 according to the present invention is a modified P2S5 for the production of the sulfide solid electrolyte having the aforementioned organic group. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a sulfide solid electrolyte and the sulfide solid electrolyte itself, which suppresses the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with water, while suppressing a decrease in ionic conductivity (hereinafter also referred to as water resistance), an electrode composite material and a lithium-ion battery containing the sulfide solid electrolyte, and a modified P2S5 for producing a sulfide solid electrolyte comprising an organic group. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart illustrating an example of a preferred embodiment of the manufacturing method of this embodiment. [Figure 2] This is a schematic diagram of the test apparatus used in water resistance evaluation. [Figure 3] These are the X-ray diffraction spectra (XRD patterns) of the raw material containing modified P2S5 used in Example 1, the electrolyte precursor (1) produced in Example 1, the amorphous sulfide solid electrolyte (1), and the crystalline sulfide solid electrolyte (1). [Figure 4] This graph shows the relationship between the amount of additive used and the amount of H2S generated. [Modes for carrying out the invention]

[0010] The embodiments of the present invention (hereinafter sometimes referred to as "these embodiments") will be described below. In this specification, the upper and lower limit values ​​related to the numerical ranges indicated by "greater than or equal to," "less than or equal to," and "~" can be any combination of values, and the values ​​in the examples can also be used as the upper and lower limit values.

[0011] (Knowledge gained by the inventors in arriving at the present invention) As a result of diligent research to solve the aforementioned problems, the inventors of this invention have discovered the following and completed the present invention. Patent Document 1, mentioned above, describes inorganic solid electrolyte particles on which organic compound groups are supported on the surface by covalent bonds. However, Patent Document 1 focuses on the binding properties between solid particles and does not confirm the ionic conductivity of inorganic solid electrolyte particles on which organic compound groups are supported on the surface. Furthermore, the inorganic solid electrolyte particles contain lithium atoms, phosphorus atoms, and sulfur atoms, but do not contain halogen atoms.

[0012] Furthermore, the surface modification of inorganic solid electrolyte particles involves exposing the surface of the inorganic solid electrolyte particles to moisture in the air and then reacting it with acid chlorides, etc., to create a structure with ester groups as bonding groups. In the method described in Reference 1, an organic compound group is supported on the inorganic solid electrolyte particles, so the resulting inorganic solid electrolyte particles will contain impurities associated with this treatment, such as lithium salts of carboxylic acids and lithium halides. Also, since the surface of the inorganic solid electrolyte particles is treated, the ionic conductivity is thought to decrease, and furthermore, it is thought that no organic groups exist inside the inorganic solid electrolyte particles. For this reason, if the surface-modified inorganic solid electrolyte particles are crushed by some force, an unmodified surface will be generated.

[0013] The inventors focused on modifying P2S5. They found that when modified P2S5 is used in the production of sulfide solid electrolytes, the resulting sulfide solid electrolyte has a uniform surface, and the modification effect extends not only to the surface but also to the interior. Furthermore, by employing the present invention, degradation due to surface treatment and the generation of by-products can be suppressed, and organic compound groups can be supported while maintaining ionic conductivity.

[0014] (Regarding various forms of this embodiment) The following describes the method for producing a sulfide solid electrolyte according to the first to eleventh forms of this embodiment, the sulfide solid electrolyte according to the twelfth form, the electrode composite material according to the thirteenth form, the lithium-ion battery according to the fourteenth form, and This paper describes modified P2S5 for the production of sulfide solid electrolytes in the fifteenth form.

[0015] The method for producing a sulfide solid electrolyte according to the first embodiment of this present invention is: A method for producing a sulfide solid electrolyte, comprising mixing a raw material-containing material comprising two or more raw materials, wherein the raw materials comprise at least one selected from lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and the raw material-containing material comprises modified P2S5.

[0016] Figure 1 shows a flow chart illustrating a preferred embodiment of the method for producing a sulfide solid electrolyte according to this embodiment. In this embodiment, modified P2S5 is used instead of P2S5 used in conventional manufacturing methods. The manufacturing process only requires changing the materials used, and there is no need to change the conventional manufacturing equipment. Moreover, a sulfide solid electrolyte with superior properties to that obtained by conventional manufacturing methods can be obtained.

[0017] In this application, "modified P2S5" refers to P2S5 that has been modified in some way, resulting in a change in its chemical properties. Further details will be provided later. In the aforementioned Patent Document 1, organic compound groups are supported only on the surface of the inorganic solid electrolyte particles. However, by using modified P2S5 as in this embodiment, not only is the surface of the manufactured sulfide solid electrolyte uniformly modified, but the modification effect is also obtained inside it. As a result, while suppressing the decrease in ionic conductivity, the generation of hydrogen sulfide gas is suppressed even when the sulfide solid electrolyte comes into contact with water. The amount of hydrogen sulfide gas generated can be measured, for example, by the method described in the examples. The lower the amount of H2S generated, the higher the water resistance can be evaluated.

[0018] A method for producing a sulfide solid electrolyte according to a second embodiment of this embodiment is, in the first embodiment described above, The method for producing a sulfide solid electrolyte is a modified P2S5 having an organic group. The presence of organic groups in modified P2S5 is preferable because it ensures that the produced sulfide solid electrolyte has organic groups not only on its surface but also within its interior, thereby suppressing the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with moisture. In particular, the presence of organic groups in modified P2S5 ensures that the surface of the produced sulfide solid electrolyte is uniformly covered with organic groups, which reduces the opportunity for moisture in the atmosphere to come into contact with the sulfide solid electrolyte, thus suppressing the generation of hydrogen sulfide gas.

[0019] "Possessing organic groups" means that organic groups are present on or within the surface of particulate P2S5, and this concept includes both the attachment of organic groups to the surface of P2S5 and their incorporation into the crystal structure. Modified P2S5 is P2S5 that has been modified by possessing organic groups. "Possessing" includes chemical bonds, physicoadsorption, and coordination bonds. Using P2S5 equipped with organic groups is preferable because the organic groups can be uniformly distributed on the surface of the sulfide solid electrolyte and further distributed into the interior of the sulfide solid electrolyte.

[0020] A method for producing a sulfide solid electrolyte according to a third embodiment of this embodiment is, in the second embodiment described above, The present invention relates to a method for producing a sulfide solid electrolyte in which the organic group contains a heteroatom. The inclusion of a heteroatom in the organic group results in a strong bond between the organic group and P2S5, which is preferable because it suppresses the loss and reduction of the organic group during the manufacturing process of the sulfide solid electrolyte, and also suppresses further reduction after it has been formed into a sulfide solid electrolyte.

[0021] The method for producing a sulfide solid electrolyte according to the fourth embodiment of this embodiment is, in the third embodiment described above, The modified P2S5 is a method for producing a sulfide solid electrolyte, wherein the modified P2S5 contains a covalent bond between the phosphorus atom of P2S5 in the modified P2S5 and the heteroatom. It is preferable that the phosphorus atom in the modified P2S5 and the organic group are covalently bonded by the heteroatom of the organic group, because the organic group will not easily detach from the modified P2S5. This is also preferable because it strongly bonds with the sulfide solid electrolyte.

[0022] The method for producing a sulfide solid electrolyte according to the fifth embodiment of this embodiment is, in the third or fourth embodiment described above, The method for producing a sulfide solid electrolyte is such that the heteroatom is at least one selected from a sulfur atom, an oxygen atom, and a nitrogen atom. When the "provided" is a chemical bond, it is preferable that the heteroatom is the aforementioned atom because it can easily form a chemical bond. When the "provided" is physical adsorption or a coordinate bond, it is preferable that the atom has a lone pair of electrons, which increases the intermolecular forces or allows it to form a coordinate bond with a lithium atom or the like.

[0023] The method for producing a sulfide solid electrolyte according to the sixth embodiment of this embodiment is, in any of the second to fifth embodiments described above, The method for producing a sulfide solid electrolyte is wherein the organic group is at least one selected from the groups represented by the general formulas (a-1), (a-2), and (b-1).

[0024] [ka]

[0025] (In the formula, * represents the binding site with P2S5, R a1 , R a2 , R b1 and R b2 Each of these independently represents a monovalent organic group, X a1 and X a2 (Each of these independently represents either an oxygen atom or a sulfur atom.)

[0026] The molecular formula for phosphorus pentasulfide is P4S10 It is represented as shown and is known to have the following three-dimensional structure.

[0027] [ka]

[0028] When phosphorus pentasulfide reacts with, for example, two molecules of a thiol derivative, it produces a thiophosphate ester while generating one molecule of hydrogen sulfide (H2S), as shown below.

[0029] [ka]

[0030] Similarly, it reacts with carboxylic acid derivatives, thiocarboxylic acid derivatives, and amine derivatives. In this way, it is preferable that the group represented by general formula (a-1), (a-2), or (b-1) is covalently bonded to the phosphorus atom in the modified P2S5, as this results in a strong bond of the organic group. If the group is represented by the general formula (a-1), (a-2), or (b-1), the covalent bond is -PS-, -PO-, -PC(=O)-, -POC(=O)-, -PC(=S)-, -PSC(=O)-, -PSC(=S)-, -PN<.

[0031] The organic group having the structure described above allows for a strong interaction between the organic group and P2S5, which is preferable because it suppresses the shedding and reduction of the organic group during the manufacturing process of the sulfide solid electrolyte, and also suppresses further reduction after it has been converted into a sulfide solid electrolyte.

[0032] The method for producing a sulfide solid electrolyte according to the seventh embodiment of this embodiment is, in any of the first to sixth embodiments described above, This is a method for producing a sulfide solid electrolyte, wherein a stirrer, mixer, or pulverizer is used for the mixing process. Using a stirrer, mixer, or pulverizer is preferable because it allows for the rapid production of a homogeneous sulfide solid electrolyte.

[0033] The method for producing a sulfide solid electrolyte according to the eighth embodiment of this embodiment is, in any of the first to seventh embodiments described above, The method for producing a sulfide solid electrolyte involves mixing the raw material components with a complexing agent during the aforementioned mixing process. Using a complexing agent is preferable because it reduces the amount of energy required during mixing.

[0034] The method for producing a sulfide solid electrolyte according to the ninth embodiment of this embodiment is, in any of the first to eighth embodiments described above, This is a method for producing a sulfide solid electrolyte, in which the mixing is performed in a solvent. Mixing in a solvent is preferable because it facilitates mixing and shortens the mixing time.

[0035] The method for producing a sulfide solid electrolyte according to the tenth embodiment of this embodiment is, in any of the first to ninth embodiments described above, This is a method for producing a sulfide solid electrolyte, which includes further heating. Heating allows for the crystallization of amorphous sulfide solid electrolytes, as described later, increasing the crystallite size. Furthermore, if a complexing agent is used, the complexing agent can be removed from the formed complex, resulting in increased ionic conductivity, which is preferable.

[0036] The method for producing a sulfide solid electrolyte according to the eleventh embodiment of this embodiment is, in any of the first to tenth embodiments described above, The method for producing a sulfide solid electrolyte is such that the sulfide solid electrolyte contains a thiolysicon region type II crystal structure. A sulfide solid electrolyte is preferable because it contains a thiolysicon region II type crystal structure, which increases its ionic conductivity.

[0037] The sulfide solid electrolyte according to the twelfth embodiment of this invention is This is a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups, with the ratio of sulfur atoms, phosphorus atoms, and halogen atoms per mole of lithium atoms being lithium atoms:sulfur atoms:phosphorus atoms:halogen atoms = 1:1.1000~1.2000:0.2000~0.3500:0.1400~0.1550. The sulfide solid electrolyte of this embodiment is obtained by any of the first to ten embodiments described above, and is preferred because it has high ionic conductivity and suppresses the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with water.

[0038] The electrode composite material according to the thirteenth embodiment of this invention is This electrode composite material comprises a sulfide solid electrolyte according to the twelfth form and an electrode active material. The sulfide solid electrolyte according to the twelfth form has high ionic conductivity, and even when the sulfide solid electrolyte comes into contact with water, the generation of hydrogen sulfide gas is suppressed, so electrode composites using it have excellent properties.

[0039] The lithium-ion battery according to the fourteenth embodiment of this invention is This is a lithium-ion battery comprising at least one of a sulfide solid electrolyte according to the twelfth form and an electrode composite material according to the thirteenth form. Since the sulfide solid electrolyte and the electrode mixture have the excellent properties described above, the electrode mixture using them will have excellent battery characteristics.

[0040] The modified P2S5 according to the fifteenth embodiment of this present invention is This is a modified P2S5 compound containing organic groups, for the production of sulfide solid electrolytes. The modified P2S5 possesses organic groups, and among modified P2S5s, those with organic groups tend to exhibit particularly excellent effects. It is preferable that the modified P2S5 be included in the raw material components used in the method for producing sulfide solid electrolytes according to the second to eleventh embodiments described above, because it is possible to produce a sulfide solid electrolyte that has high ionic conductivity and suppresses the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with water.

[0041] The sulfide solid electrolyte, the method for producing the sulfide solid electrolyte, the electrode composite material, and the lithium-ion battery of this embodiment will be described in more detail below, following the above-described embodiment. [Method for producing sulfide solid electrolytes] The method for producing a sulfide solid electrolyte according to this embodiment includes mixing a raw material-containing material comprising two or more raw materials, wherein the raw materials comprise at least one selected from lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and the raw material-containing material comprises modified P2S5.

[0042] In this specification, "sulfide solid electrolyte" means an electrolyte that remains solid at 25°C under a nitrogen atmosphere. The sulfide solid electrolyte in this embodiment is a sulfide solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups, and has ionic conductivity due to the lithium atoms.

[0043] In this specification, "contains" and "contains as a component" include not only the literal meaning of "contains," but also cases where "contains" means being bonded with other atoms or molecules, for example, when at least one atom constituting a compound is bonded to at least one atom constituting another compound, while maintaining the composition of the compound at the time of mixing.

[0044] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystalline structure obtained by the manufacturing method of this embodiment, and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a sulfide solid electrolyte in which a peak originating from the sulfide solid electrolyte is observed in the X-ray diffraction pattern during X-ray diffraction measurement, regardless of whether or not a peak originating from the raw material of the sulfide solid electrolyte is observed. That is, a crystalline sulfide solid electrolyte includes a crystalline structure derived from the sulfide solid electrolyte, and may be a part of the crystalline structure derived from the sulfide solid electrolyte, or may be entirely derived from the sulfide solid electrolyte. Furthermore, a crystalline sulfide solid electrolyte may contain amorphous sulfide solid electrolyte as long as it has the X-ray diffraction pattern described above. Therefore, crystalline sulfide solid electrolytes include so-called glass ceramics obtained by heating amorphous sulfide solid electrolyte above its crystallization temperature.

[0045] Furthermore, in this specification, an amorphous sulfide solid electrolyte refers to a material in which the X-ray diffraction pattern observed in X-ray diffraction measurements is a halo pattern in which peaks other than those originating from the material are substantially absent, and does not refer to the presence or absence of peaks originating from the raw materials of the sulfide solid electrolyte.

[0046] The method for producing a sulfide solid electrolyte in this embodiment requires mixing a raw material-containing material that includes two or more raw materials, but may also include using a complexing agent as described later, passing through an electrolyte precursor, and heating as described later if necessary, as shown in Figure 1.

[0047] Details of the electrolyte precursor will be described later, but it is a complex obtained by mixing a complexing agent with a sulfide solid electrolyte.

[0048] Sulfide solid electrolytes can generate hydrogen sulfide due to hydrolysis reactions that occur when they come into contact with moisture such as humidity in the air. Therefore, ideally, the manufacturing process of sulfide solid electrolytes and batteries should be carried out in a low-dew-point environment with low moisture content. However, it is economically and physically difficult to carry out all processes at a low dew point, and in reality, it is required to be able to handle sulfide solid electrolytes at a high dew point (e.g., dew point of -60 to -20°C) at the level of a dry room. Manufacturing methods using complexing agents enable production at high dew points, resulting in excellent efficiency in scaling up the manufacturing process.

[0049] By using the modified P2S5, the organic groups described below can be introduced into the sulfide solid electrolyte. It is preferable to use modified P2S5 together with unmodified P2S5 as the raw material to adjust the amount of organic groups contained in the sulfide solid electrolyte, but to simplify the manufacturing method, it is preferable to contain only modified P2S5 as the P2S5. As described later, it is preferable to adjust the amount of organic groups contained in the sulfide solid electrolyte according to the amount of organic groups contained in the modified P2S5.

[0050] <Mixing> In the manufacturing method of this embodiment, the mixing is not particularly limited as long as it involves mixing a raw material-containing material that includes two or more raw materials, and the mixing may be done by either a liquid-phase method or a solid-phase method. Furthermore, the liquid-phase method may be a homogeneous method in which the raw material-containing material is completely dissolved in a solvent and then mixed, or a heterogeneous method in which the raw material-containing material is not completely dissolved and mixed via a suspension in which solid and liquid coexistence occurs. Mixing may involve mixing the raw material components with the complexing agent described below. Using a complexing agent is preferable because it allows for the production of a sulfide solid electrolyte by mixing without requiring high temperatures.

[0051] From the viewpoint of preventing granulation that increases particle size during the mixing process and enabling production at low temperatures with simple equipment, it is preferable to carry out the process in a solvent, such as the homogeneous method or the heterogeneous method. From the viewpoint of achieving high ionic conductivity and reducing the environmental burden associated with the use of solvents, the solid-phase method is preferred. The raw material components may be solid or liquid, but they are usually solid or slurry as described below.

[0052] There are no particular restrictions on the method of mixing raw material-containing materials that include two or more raw materials. The prepared raw material-containing materials can be placed in a device capable of mixing raw material-containing materials that include two or more raw materials and mixed. Furthermore, to shorten the mixing time, it is preferable to perform the mixing in a solvent as described later.

[0053] In the manufacturing method of this embodiment, mixing includes stirring and grinding in addition to mixing, and it is preferable to use a stirrer, mixer, or grinder for mixing, and it is more preferable to use a stirrer and mixer. Examples of agitators and mixers include mechanical agitators equipped with agitating blades inside the tank. Mechanical agitators include high-speed agitators and dual-arm mixers. High-speed agitators are preferred from the viewpoint of improving the uniformity of the raw materials in the mixture of raw material components and complexing agents and obtaining higher ionic conductivity. High-speed agitators include vertical-axis rotary mixers and horizontal-axis rotary mixers, and either type of mixer may be used.

[0054] Examples of impeller shapes used in mechanical agitation mixers include blade type, arm type, anchor type, paddle type, full zone type, ribbon type, multi-stage blade type, double arm type, shovel type, twin-shaft impeller type, flat impeller type, C-type impeller type, anchor type, paddle type, and full zone type. From the viewpoint of improving the uniformity of the raw materials in the raw material mixture and obtaining higher ionic conductivity, shovel type, flat impeller type, and C-type impeller type are preferred. For small-scale production, stirring using a stirring bar may also be acceptable.

[0055] There are no particular restrictions on the temperature conditions when mixing the raw material components, the complexing agent if necessary, and the solvent if necessary. For example, -30 to 100°C, preferably -10 to 50°C, and more preferably around room temperature (23°C) (for example, room temperature ± 5°C). The mixing time is 0.1 to 150 hours, and from the viewpoint of achieving more uniform mixing and higher ionic conductivity, it is preferably 0.2 to 120 hours, more preferably 0.3 to 100 hours, and even more preferably 0.5 to 80 hours.

[0056] Furthermore, a more specific example of a pulverizer is a media-type pulverizer. Media-type pulverizers are broadly classified into container-driven pulverizers and media-agitated pulverizers. Examples of container-driven grinders include agitation tanks, grinding tanks, or combinations thereof such as ball mills and bead mills. Ball mills and bead mills can be of various types, including rotary, rolling, vibrating, and planetary types. Furthermore, examples of media-agitating grinders include impact grinders such as cutter mills, hammer mills, and pin mills; tower-type grinders such as tower mills; agitated tank-type grinders such as attritors, aquamizers, and sand grinders; flow-tank-type grinders such as visco mills and pearl mills; flow-pipe-type grinders; annular-type grinders such as coball mills; and continuous dynamic grinders.

[0057] The particle size of the medium used in bead mills, ball mills, etc., can be appropriately determined considering the type and particle size of the raw materials used, the type and scale of the equipment used, etc., but is usually preferably 0.01 mm or larger, more preferably 0.015 mm or larger, even more preferably 0.02 mm or larger, and even more preferably 0.04 mm or larger, with an upper limit of preferably 3 mm or smaller, more preferably 2 mm or smaller, even more preferably 1 mm or smaller, and even more preferably 0.8 mm or smaller. Examples of materials used as the medium include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0058] Furthermore, when using ball mills or bead mills, the rotational speed varies depending on the scale of processing and cannot be generalized, but it is usually 10 to 1000 rpm, preferably 20 to 900 rpm. Furthermore, the grinding time in this case varies depending on the scale of processing and cannot be stated definitively, but it is usually 0.5 to 100 hours, preferably 1 to 72 hours, and more preferably 5 to 48 hours.

[0059] (To dry) The method for producing the sulfide solid electrolyte of this embodiment may include drying the electrolyte precursor and / or the sulfide solid electrolyte. This removes the complexing agent and solvent present as liquid, yielding a powder of the electrolyte precursor and / or the sulfide solid electrolyte. Pre-drying allows for efficient heating as described later. Note that drying and subsequent heating may be performed in the same step.

[0060] Drying can be carried out by drying the electrolyte precursor and / or sulfide solid electrolyte at a temperature appropriate to the type of solvent and residual complexing agent (complexing agent not incorporated into the material being dried). For example, it can be carried out at a temperature above the boiling point of the solvent or complexing agent. Alternatively, it can be carried out by 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 around room temperature (23°C) (for example, around room temperature ± 5°C) to volatilize the complexing agent.

[0061] Furthermore, drying may be performed by filtration of the electrolyte precursor and / or sulfide solid electrolyte using a glass filter or the like, solid-liquid separation by decantation, or solid-liquid separation using a centrifuge or the like. In this embodiment, drying may be performed under the above temperature conditions after solid-liquid separation. Specifically, solid-liquid separation can be easily performed by decantation, which removes the complexing agent and solvent that form the supernatant after the electrolyte precursor and / or sulfide solid electrolyte have precipitated, or by filtration using a glass filter with a pore size of approximately 10 to 200 μm, preferably 20 to 150 μm.

[0062] <To be heated> The method for producing a sulfide solid electrolyte according to this embodiment may further include heating after mixing the electrolyte precursor and / or the sulfide solid electrolyte. That is, it is preferable to include heating the electrolyte precursor to obtain the amorphous sulfide solid electrolyte described later, and heating the electrolyte precursor or amorphous sulfide solid electrolyte to obtain the crystalline sulfide solid electrolyte described later. By including heating the electrolyte precursor, complexing agents and solvents are removed from the electrolyte precursor, yielding amorphous sulfide solid electrolytes and crystalline sulfide solid electrolytes containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Furthermore, the electrolyte precursor heated in this process may be a pulverized product of an electrolyte precursor obtained by pulverization as described later. Furthermore, heating the crystalline sulfide solid electrolyte to increase the crystallite size is also preferable because it can increase the ionic conductivity.

[0063] The removal of the complexing agent from the electrolyte precursor is supported by the fact that the complexing agent constitutes a cocrystal of the precursor, as evidenced by the results of X-ray diffraction patterns and gas chromatography analysis, and by the fact that the sulfide solid electrolyte obtained by removing the complexing agent by heating the electrolyte precursor has the same X-ray diffraction pattern as the sulfide solid electrolyte obtained by conventional methods without using a complexing agent.

[0064] In the manufacturing method of this embodiment, the sulfide solid electrolyte is obtained by heating the electrolyte precursor to remove the complexing agent in the electrolyte precursor. While it is preferable to have as little complexing agent as possible in the sulfide solid electrolyte, it may contain a complexing agent in an amount that does not impair the performance of the sulfide solid electrolyte. The complexing agent content in the sulfide solid electrolyte should normally be 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. Since a lower content is preferable, the lower limit is not particularly limited.

[0065] In the manufacturing method of this embodiment, a crystalline sulfide solid electrolyte may be obtained by heating an electrolyte precursor, or by heating an electrolyte precursor to obtain an amorphous sulfide solid electrolyte, and then heating the amorphous sulfide solid electrolyte. In other words, an amorphous sulfide solid electrolyte can also be produced in the manufacturing method of this embodiment. Conventionally, obtaining a crystalline sulfide solid electrolyte with high ionic conductivity, such as a sulfide solid electrolyte having a thiolysiconregion II type crystal structure (described later), required first producing an amorphous sulfide solid electrolyte through mechanical pulverization such as mechanical milling, or other melt-and-cooling treatments, and then heating the amorphous sulfide solid electrolyte. However, the manufacturing method of this embodiment is superior to conventional manufacturing methods using mechanical milling, etc., because it can obtain a crystalline sulfide solid electrolyte having a thiolysiconregion II type crystal structure without mechanical pulverization or other melt-and-cooling treatments.

[0066] In the method for producing a sulfide solid electrolyte of this embodiment, whether to obtain an amorphous sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or to obtain an amorphous sulfide solid electrolyte first and then a crystalline sulfide solid electrolyte, or to obtain a crystalline sulfide solid electrolyte directly from an electrolyte precursor, can be appropriately selected as desired and can be adjusted by heating temperature, heating time, etc. The heating temperature of the electrolyte precursor can be determined, for example, when obtaining an amorphous sulfide solid electrolyte, according to the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte (or electrolyte precursor). Specifically, the amorphous sulfide solid electrolyte (or electrolyte precursor) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) under a heating condition of 10°C / min, and the temperature should be set to a range of preferably 5°C or lower, more preferably 10°C or lower, and even more preferably 20°C or lower, starting from the temperature of the peak top of the exothermic peak observed at the lowest temperature. There is no particular lower limit, but it should be approximately -40°C or higher from the temperature of the peak top of the exothermic peak observed at the lowest temperature. By using such a temperature range, amorphous sulfide solid electrolytes can be obtained more efficiently and reliably.

[0067] The heating temperature for obtaining amorphous sulfide solid electrolytes varies depending on the structure of the resulting crystalline sulfide solid electrolyte and cannot be specified in general terms. However, it is generally preferred to be 250°C or lower, more preferably 220°C or lower, and even more preferably 200°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.

[0068] Furthermore, heating is preferably carried out under reduced pressure, preferably 0.1 Pa or higher from an apparatus standpoint, more preferably 1.0 Pa or higher, and even more preferably 5.0 Pa or higher, from the viewpoint of obtaining a solid electrolyte with high ionic conductivity. It is preferably 100.0 Pa or less, more preferably 50.0 Pa or less, and even more preferably 20.0 Pa or less.

[0069] Furthermore, when obtaining a crystalline sulfide solid electrolyte by heating an amorphous sulfide solid electrolyte or directly from an electrolyte precursor, the heating temperature should be determined according to the structure of the crystalline sulfide solid electrolyte. It is preferable that the heating temperature be higher than that used to obtain the amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte (or precursor) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) under a heating rate of 10°C / min. The temperature should be set to a range of 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, starting from the temperature of the peak top of the exothermic peak observed at the lowest temperature. There is no particular upper limit, but it should be around 40°C or lower. By using such a temperature range, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining a crystalline sulfide solid electrolyte varies depending on the structure of the resulting crystalline sulfide solid electrolyte and cannot be specified in general terms. However, it is generally preferred to be 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. There is no particular upper limit, but it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0070] The heating time is not particularly limited as long as it is the time required to obtain the desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte, but for example, 1 minute or more is preferred, 10 minutes or more is more preferred, 30 minutes or more is even more preferred, and 1 hour or more is even more preferred. Also, there is no particular upper limit to the heating time, but 24 hours or less is preferred, 10 hours or less is more preferred, 5 hours or less is even more preferred, and 3 hours or less is even more preferred.

[0071] Furthermore, heating is preferably carried out in an inert gas atmosphere (e.g., nitrogen atmosphere, argon atmosphere) or a reduced pressure atmosphere (especially in a vacuum). This is because it prevents deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte. The heating method is not particularly limited, but examples include using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, or a calcination furnace. Industrially, horizontal dryers and horizontal vibrating fluid dryers having heating means and a feeding mechanism can also be used, and the appropriate method should be selected according to the amount of material to be heated.

[0072] (To crush) The method for producing the sulfide solid electrolyte of this embodiment preferably further includes pulverizing the electrolyte precursor and / or the sulfide solid electrolyte. By pulverizing the electrolyte precursor and / or the sulfide solid electrolyte, a sulfide solid electrolyte with a small particle size can be obtained while suppressing a decrease in ionic conductivity. The aforementioned pulverizer can be used as the pulverizer for pulverization in this embodiment.

[0073] By adjusting the peripheral speed of the rotating body of the pulverizer, the crushing (micronization) and granulation (grain growth) of the solid electrolyte can be controlled. In other words, in addition to mixing, the average particle size can be reduced by crushing, or increased by granulation, so the morphology of the sulfide solid electrolyte can be easily and freely adjusted. More specifically, crushing can be achieved by rotating the rotating body at a low peripheral speed, and granulation can be achieved by rotating the rotating body at a high peripheral speed. In this way, the morphology of the solid electrolyte can be easily adjusted simply by adjusting the peripheral speed of the rotating body.

[0074] Regarding the peripheral speed of a rotating body, low and high peripheral speeds cannot be defined in general terms, as they can vary depending on factors such as the particle size, material, and amount of the media used in the pulverizer. For example, in the case of devices that do not use pulverizing media such as balls or beads, such as high-speed swirling thin-film agitators, crushing mainly occurs even at relatively high peripheral speeds, and granulation is unlikely to occur. On the other hand, in the case of devices that use pulverizing media such as ball mills and bead mills, as described above, crushing can be done at low peripheral speeds, and granulation is possible at high peripheral speeds. Therefore, assuming the same conditions for the pulverizer, pulverizing media, etc., the peripheral speed at which crushing is possible is lower than the peripheral speed at which granulation is possible. Thus, for example, under conditions where granulation is possible at a peripheral speed of 6 m / s, low peripheral speed means less than 6 m / s, and high peripheral speed means 6 m / s or more.

[0075] In the pulverization (mechanical treatment) of sulfide solid electrolytes, container-driven pulverizers are preferred among the above-mentioned pulverizers, and bead mills and ball mills are particularly preferred, from the viewpoint of more easily adjusting the desired morphology. Container-driven pulverizers such as bead mills and ball mills are equipped with a rotating body capable of stirring the mechanical treatment precursor, and a container such as a stirring tank or pulverizing tank that houses the mechanical treatment precursor. Therefore, as described above, the morphology of the sulfide solid electrolyte can be easily adjusted by adjusting the peripheral speed of the rotating body. Bead mills and ball mills allow for morphological adjustment by controlling the particle size, material, and quantity of beads and balls used, enabling finer morphological adjustments and even the creation of morphologies previously unattainable. For example, centrifugal bead mills can be used with so-called microbeads of extremely fine size (approximately φ0.015~1mm), such as the Ultra Apex Mill (UAM).

[0076] Regarding the adjustment of morphology, reducing the energy imparted to the solid electrolyte, i.e., lowering the peripheral speed of the rotating body or reducing the particle size of beads, balls, etc., tends to result in a smaller average particle size (crushing) and a larger specific surface area. Conversely, increasing the energy, i.e., increasing the peripheral speed of the rotating body or increasing the particle size of beads, balls, etc., tends to result in a larger average particle size (granulation) and a smaller specific surface area. Furthermore, for example, the longer the mechanical processing time, the larger the average particle size tends to be (granulation).

[0077] The processing time for mechanical processing can be appropriately determined considering the desired morphology, the type and scale of the equipment used, etc., but is usually preferably 5 seconds or more, more preferably 30 seconds or more, even more preferably 3 minutes or more, and even more preferably 15 minutes or more, with an upper limit of preferably 5 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, and even more preferably 1.5 hours or less. The peripheral speed of a rotating body in mechanical processing (rotational speed in devices such as bead mills and ball mills) should be determined appropriately considering the desired morphology, the type and size of the device used, etc. However, it is usually preferably 0.5 m / s or more, more preferably 1 m / s or more, even more preferably 2 m / s or more, and even more preferably 3 m / s or more. The upper limit is preferably 55 m / s or less, more preferably 40 m / s or less, even more preferably 25 m / s or less, and even more preferably 15 m / s or less. The peripheral speed may remain the same or can be changed during the process.

[0078] [Sulfide solid electrolyte] The sulfide solid electrolyte of this embodiment can be easily manufactured by the method for manufacturing the sulfide solid electrolyte of this embodiment described above, and can be easily manufactured by using modified P2S5 having an organic group. In another embodiment, the sulfide solid electrolyte contains lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms and an organic group, and the ratio of the content (mol) of sulfur atoms, phosphorus atoms and halogen atoms per (mol) of lithium atoms is lithium atoms:sulfur atoms:phosphorus atoms:halogen atoms = 1:1.1000~1.2000:0.2000~0.3500:0.1400~0.1550. If the aforementioned ratio of content is not met, the required ionic conductivity cannot be obtained.

[0079] The sulfide solid electrolyte of this embodiment is required to contain the organic group, but in order to improve water resistance for every 1 mole of phosphorus atoms in the sulfide solid electrolyte with respect to the organic group, it is preferable that the amount of organic group be 0.005 mol or more, more preferably 0.01 mol or more, and even more preferably 0.03 mol or more. In order to suppress the decrease in the ionic conductivity of the sulfide solid electrolyte, it is preferable that the amount be 0.50 mol or less, more preferably 0.30 mol or less, even more preferably 0.20 mol or less, and even more preferably 0.15 mol or less.

[0080] The sulfide solid electrolyte of this embodiment exhibits excellent water resistance, and even when exposed to moisture in the atmosphere, the generation of hydrogen sulfide gas is suppressed. However, the amount of H2S generated is preferably 1.70 cc / g or less, more preferably 1.60 cc / g or less, even more preferably 1.50 cc / g or less, and even more preferably 1.00 cc / g or less. A lower amount of H2S generation is preferable, and there is no particular lower limit. The amount of H2S generated can be measured, for example, by the method described in the examples.

[0081] The ratio of phosphorus atoms (mol) to modifier (mol) in a sulfide solid electrolyte (modifier / P) can be estimated from the amount of modifier and P2S5 used when producing modified P2S5. Furthermore, the phosphorus atom content in the sulfide solid electrolyte can be determined by measurement using the inductively coupled plasma (ICP) emission spectrometer described in the examples, and the organic group content can be determined by focusing on the characteristic functional groups of the organic group and appropriately combining Fourier transform infrared spectrophotometer (FT-IR), solid-state nuclear magnetic resonance (NMR) spectroscopy, gas chromatography, gas chromatograph-mass spectrometer (GC-Mass), etc. The modifier is an agent used to introduce an organic group into P2S5, as will be described later.

[0082] In this specification, "solid electrolyte" refers to an electrolyte that remains solid at 25°C under a nitrogen atmosphere, and "sulfide solid electrolyte" refers to a solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and having ionic conductivity due to the lithium atoms.

[0083] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystalline structure and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a sulfide solid electrolyte in which a peak originating from the sulfide solid electrolyte is observed in the X-ray diffraction pattern in X-ray diffraction measurements, as described below. The presence or absence of peaks originating from the raw material is irrelevant to the material. That is, the crystalline sulfide solid electrolyte contains a crystalline structure derived from the sulfide solid electrolyte, and it may be a crystalline structure that is partly derived from the sulfide solid electrolyte, or it may be a crystalline structure that is entirely derived from the sulfide solid electrolyte. Furthermore, as long as the crystalline sulfide solid electrolyte has the above-described X-ray diffraction pattern, it may contain a part of an amorphous sulfide solid electrolyte, or it may not contain an amorphous sulfide solid electrolyte at all. Rather, the presence of an amorphous component is preferable as it makes it easier to process into a battery. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous sulfide solid electrolyte above its crystallization temperature. Glass ceramics are preferable in order to increase ionic conductivity.

[0084] In this specification, an amorphous sulfide solid electrolyte refers to a solid electrolyte whose X-ray diffraction pattern is substantially a halo pattern with no peaks observed in X-ray diffraction measurements, regardless of the presence or absence of peaks originating from the raw materials of the sulfide solid electrolyte, or the presence or absence of small amounts of crystals that inevitably form during the isolation process of the amorphous sulfide solid electrolyte. (Amorphous sulfide solid electrolyte)

[0085] In the sulfide solid electrolyte of this embodiment, the amorphous sulfide solid electrolyte contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Typical examples include sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and preferably sulfide solid electrolytes that further contain other atoms such as oxygen atoms and silicon atoms, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the viewpoint of obtaining higher ionic conductivity, sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred. The types of atoms constituting amorphous sulfide solid electrolytes can be determined, for example, by an ICP emission spectrometer.

[0086] In the sulfide solid electrolyte of this embodiment, if the amorphous sulfide solid electrolyte has 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. In the method for producing a sulfide solid electrolyte of this embodiment, if the amorphous sulfide solid electrolyte obtained is, for example, Li2S-P2S5-LiI-LiBr, the total content of lithium sulfide and phosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. Furthermore, 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%.

[0087] In the sulfide solid electrolyte of this embodiment, for the amorphous sulfide solid electrolyte, a ratio of sulfur atoms, phosphorus atoms, and halogen atoms per mole of lithium atoms is preferably 1:1.1000~1.2000:0.2000~0.3500:0.1400~0.1550, as this allows for a higher ionic conductivity of the sulfide solid electrolyte produced using this ratio. A more preferable ratio is 1:1.1200~1.1800:0.2400~0.3200:0.1410~0.1500, and an even more preferable ratio is 1:1.1300~1.1700:0.2700~0.3000:0.1440~0.1490.

[0088] Furthermore, when bromine and iodine are used as halogen atoms, the ratio of sulfur atoms, phosphorus atoms, bromine atoms, and iodine atoms per mole of lithium atoms is approximately: lithium atoms:sulfur atoms:phosphorus atoms:bromine atoms:iodine atoms = 1:1.1000~1.2000:0.2000~0.3500:0.0700~0.0760:0.070 It is preferable that the range is 0 to 0.0760, more preferably 1:1.1200 to 1.1800:0.2400 to 0.3200:0.0710 to 0.0755:0.0700 to 0.0755, and even more preferably 1:1.1300 to 1.1700:0.2700 to 0.3000:0.0720 to 0.0750:0.0700 to 0.0750. By setting the range as described above, it becomes easier to obtain sulfide solid electrolytes with higher ionic conductivity and having a thiolysicon region type II crystal structure, as described later.

[0089] Furthermore, there are no particular restrictions on the shape of the amorphous sulfide solid electrolyte, but for example, particulate form can be given. The average particle size (D) of the particulate amorphous sulfide solid electrolyte. 50 Examples of these ranges include 0.01 μm to 500 μm and 0.1 to 200 μm.

[0090] (Crystalline sulfide solid electrolyte) In the sulfide solid electrolyte of the present embodiment, the crystalline sulfide solid electrolyte may be so-called glass ceramics obtained by heating an amorphous sulfide solid electrolyte to a temperature equal to or higher than the crystallization temperature. As its crystal structure, a Li3PS4 crystal structure, a Li4P2S6 crystal structure, a Li7PS6 crystal structure, a Li7P3S 11 crystal structure, a crystal structure having peaks in the vicinity of 2θ = 20.2° and 23.6° (for example, see Japanese Patent Application Laid-Open No. 2013-16423), etc. can be mentioned. In the sulfide solid electrolyte of the present embodiment, it is preferable that the crystalline sulfide solid electrolyte contains a thio-LISICON Region II type crystal structure.

[0091] Also, Li 4-x Ge 1-x P<00,00012>S4-based thio-LISICON Region II (thio-LISICON Region II) type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148(7) A742-746(2001)), Li 4-x Ge 1-x P x S4-based thio-LISICON Region II (thio-LISICON Region II) type and similar crystal structures (see Solid State Ionics, 177(2006), 2721-2725), etc. can also be mentioned. The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of the sulfide solid electrolyte of the present embodiment is preferably a thio-LISICON Region II type crystal structure among the above in terms of obtaining higher ionic conductivity.

[0092] Here, the "thio-LISICON Region II type crystal structure" is Li 4-x Ge 1-x P x S4-based thio-LISICON Region II (thio-LISICON Region II) type crystal structure, Li 4-x Ge 1-x P xThis indicates that the crystal structure is similar to that of the S4-type thio-LISICON Region II. Furthermore, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may have the thio-LISICON Region II type crystal structure, or it may have it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having 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 sulfide solid electrolyte obtained by the manufacturing method of this embodiment does not contain crystalline Li3PS4 (β-Li3PS4).

[0093] In X-ray diffraction measurements using CuKα rays, diffraction peaks for the Li3PS4 crystal structure appear, for example, around 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, diffraction peaks for the Li4P2S6 crystal structure appear, for example, around 2θ = 16.9°, 27.1°, and 32.5°, diffraction peaks for the Li7PS6 crystal structure appear, for example, around 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and Li7P3S 11 Diffraction peaks of the crystal structure appear, for example, around 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, Li 4-x Ge 1-x P x The diffraction peaks of the S4-type thio-LISICON Region II crystal structure appear, for example, around 2θ = 20.1°, 23.9°, and 29.5°, and Li 4-x Ge 1-x P x Diffraction peaks similar to the S4-type thio-LISICON Region II crystal structure appear, for example, around 2θ = 20.2 and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0094] As described above, when a thio-Li3PS4 region II-type crystal structure is obtained in the present embodiment, it is preferably free of crystalline Li3PS4 (β-Li3PS4). The sulfide solid electrolyte of the present embodiment either does not have diffraction peaks at 2θ = 17.5° and 26.1° observed in crystalline Li3PS4, or even if it has such peaks, the detected peaks are extremely small compared to the diffraction peaks of the thio-Li3PS4 region II-type crystal structure.

[0095] Having the above-described structural framework of Li7PS6 and having a composition formula Li 7-x P 1-y Si y S6 and Li 7+x P 1-y Si y The crystal structure represented by S6 (where x is -0.6 to 0.6 and y is 0.1 to 0.6) is cubic or orthorhombic, preferably cubic, and in X-ray diffraction measurement using CuKα radiation, 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°. The above composition formula Li<00...​​​​​​​​​​​​​​​​In the sulfide solid electrolyte of this embodiment, the content of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in the crystalline sulfide solid electrolyte is the same as that of the amorphous sulfide solid electrolyte described above.

[0097] There are no particular restrictions on the shape of the crystalline sulfide solid electrolyte, but for example, particulate form can be used. The average particle size (D) of the particulate crystalline sulfide solid electrolyte. 50 Examples of these ranges include 0.01 μm to 500 μm and 0.1 to 200 μm.

[0098] The crystallite size of the sulfide solid electrolyte in this embodiment is preferably 30 nm or larger. From the viewpoint of improving ionic conductivity and water resistance, it is preferably 33 nm or larger, more preferably 35 nm or larger, even more preferably 40 nm or larger, even more preferably 70 nm or larger, and most preferably 80 nm or larger. As will be described later, the crystallite size of the sulfide solid electrolyte can be further increased by crystallization after step (A), in which case it is most preferably 90 nm or larger. There is no particular upper limit, but from the perspective of ease of manufacturing, ease of procurement, and ease of manufacturing batteries, etc., it is preferably 300 nm or smaller, more preferably 250 nm or smaller, even more preferably 200 nm or smaller, even more preferably 150 nm or smaller, and most preferably 130 nm or smaller.

[0099] The ionic conductivity of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is PS4 3- Due to its high phosphorus content, the level is extremely high, typically exceeding 0.01 mS / cm. It is more preferable that the value be 1.00 mS / cm or higher, even more preferable that it be 2.00 mS / cm or higher, even more preferable that it be 2.50 mS / cm or higher, even more preferable that it be 3.00 mS / cm or higher, and particularly preferable that it be 3.50 mS / cm or higher.

[0100] <Raw material content> The method for producing a sulfide solid electrolyte according to this embodiment requires mixing a raw material-containing material that includes two or more raw materials. The raw material content includes two or more raw materials, each of which contains at least one selected from lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and furthermore, the raw material content must contain the modified P2S5 described below.

[0101] As raw materials included in the raw material composition, for example, compounds containing at least one of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms can be used. More specifically, 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); amorphous Li3 obtained from lithium sulfide and phosphorus sulfide, having a PS4 structure as its molecular structure. A raw material consisting of at least two atoms selected from the four types of atoms mentioned above, such as solid electrolytes like PS4 or crystalline Li3PS4; thiophosphoryl fluorides such as thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and elemental halogens such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), preferably chlorine (Cl2), bromine (Br2), and iodine (I2), and more preferably bromine (Br2) and iodine (I2).

[0102] It is even more preferable that the aforementioned raw material contains at least one selected from lithium sulfide, lithium halide, phosphorus sulfide, phosphorus halide, and halogen molecules. In this embodiment, it is preferable to use at least one selected from lithium sulfide, lithium halide, phosphorus sulfide, phosphorus halide, and halogen molecules, as this yields a solid electrolyte with high ionic conductivity. Furthermore, it is preferable to use lithium halide together with a complexing agent and solvent to introduce halogen atoms into the fixed electrolyte, as this prevents the separation of halogen atoms in the subsequent step of removing the solvent, etc., and yields a solid electrolyte with high ionic conductivity.

[0103] Other materials that can be used as raw material components include, for example, raw materials that contain at least one atom selected from the four types of atoms and also contain 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, SnS2), aluminum sulfide, and zinc sulfide; phosphorus 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 halide, silicon halide, germanium halide, arsenic halide, selenium halide, tin halide, antimony halide, tellurium halide, and bismuth halide; and phosphorus oxyhalides such as phosphorus oxychloride (POCl3) and phosphorus oxybromide (POBr3).

[0104] In this embodiment, from the viewpoint of more easily obtaining a solid electrolyte having high ionic conductivity, among the above, phosphorus sulfides such as lithium sulfide, phosphorus trisulfide (P2S3), and phosphorus pentasulfide (P2S5), elemental halogens (halogen molecules) such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide are preferred as raw material components. For example, combinations of lithium sulfide, phosphorus pentasulfide, and lithium halides, and combinations of lithium sulfide, phosphorus pentasulfide, and elemental halogens are preferred, with lithium bromide and lithium iodide being preferred as lithium halides, and bromine and iodine being preferred as elemental halogens.

[0105] The raw material content of this embodiment must contain modified P2S5 as described above, and preferably contains modified P2S5, lithium sulfide, and lithium halide, and preferably contains either or both of lithium bromide and lithium iodide as lithium halide. In other words, a content containing modified P2S5 and lithium sulfide and either or both of lithium bromide and lithium iodide as lithium halide is preferred.

[0106] In this embodiment, the lithium sulfide used is preferably in the form of particles. Average particle size of lithium sulfide particles (D 50 The average particle size (D) is preferably 10 μm or more and 2000 μm or less, more preferably 30 μm or more and 1500 μm or less, and even more preferably 50 μm or more and 1000 μm or less. In this specification, the average particle size (D) 50 The volume distribution is the particle size at which the accumulation of particle diameters, starting from the smallest particle, reaches 50% of the total when plotting a particle diameter distribution integration curve. The volume distribution is the average particle size, which can be measured, for example, using a laser diffraction / scattering particle diameter distribution analyzer. Furthermore, among the raw materials exemplified above, solid raw materials are preferably those having an average particle size similar to that of the lithium sulfide particles, that is, those within the same range as the average particle size of the lithium sulfide particles.

[0107] <Modified P2S5> It is preferable that the modified P2S5 is P2S5 that contains an organic group.

[0108] As described above, modified P2S5 is preferable because the presence of organic groups suppresses the generation of hydrogen sulfide gas even when the sulfide solid electrolyte comes into contact with moisture. In modified P2S5, the amount of organic groups is preferably 0.005 mol or more, more preferably 0.01 mol or more, and even more preferably 0.03 mol or more, in order to suppress the decrease in the ionic conductivity of the sulfide solid electrolyte, it is preferably 0.50 mol or less, more preferably 0.30 mol or less, even more preferably 0.20 mol or less, and even more preferably 0.15 mol or less, in order to improve the water resistance of the modified P2S5. The ratio of phosphorus atoms (mol) to modifier (mol) in modified P2S5 (modifier / P) can be estimated from the amount of modifier (mol) and P2S5 used in the production of modified P2S5. The modifier is an agent used to introduce an organic group into P2S5, as will be described later.

[0109] The presence of a heteroatom in the organic group allows for a strong interaction between the organic group and P2S5, as described above. This suppresses the loss and reduction of the organic group during the manufacturing process of the sulfide solid electrolyte, and also suppresses further reduction after the sulfide solid electrolyte is formed, which is preferable. The modified P2S5 is preferable because it contains a covalent bond between the phosphorus atom of P2S5 and the heteroatom, preventing the organic group from easily detaching from the modified P2S5. This is also preferable because it strongly bonds with the sulfide solid electrolyte.

[0110] If the heteroatom is at least one selected from a sulfur atom, an oxygen atom, and a nitrogen atom, then when "provided" is a chemical bond, it is preferable that the heteroatom is one of the aforementioned atoms because it can easily form a chemical bond. If "provided" is physical adsorption or a coordinate bond, then it is preferable that the atom has a lone pair of electrons, which increases the intermolecular forces or allows it to form a coordinate bond with a lithium atom or the like.

[0111] The organic group being at least one selected from the groups represented by general formulas (a-1), (a-2), and (b-1) interacts strongly with P2S5, which is preferable because it suppresses the shedding and reduction of the organic group during the manufacturing process of the sulfide solid electrolyte, and also suppresses its reduction after it has been converted into a sulfide solid electrolyte. A sulfide solid electrolyte containing at least one group selected from the groups represented by general formulas (a-1), (a-2), and (b-1) is preferable to a sulfide solid electrolyte that does not contain these groups because, even with the inclusion of these groups, the decrease in ionic conductivity is suppressed, and the generation of hydrogen sulfide gas is suppressed even when in contact with moisture. The organic group is more preferably a group represented by general formula (a-1) or (b-1), even more preferably a group represented by general formula (a-1) because the decrease in ionic conductivity is suppressed, and even more preferably a group represented by general formula (b-1) because the generation of hydrogen sulfide gas is suppressed.

[0112] [ka]

[0113] In the groups represented by general formulas (a-1) and (a-2), R a1 and R a2Each of these groups is preferably an alkyl group having 1 to 30 carbon atoms or an alkenyl group having 2 to 30 carbon atoms, more preferably an alkyl group having 4 to 20 carbon atoms or an alkenyl group having 4 to 20 carbon atoms, even more preferably an alkyl group having 6 to 12 carbon atoms or an alkenyl group having 6 to 12 carbon atoms, and even more preferably a linear alkyl group having 6 to 10 carbon atoms or a linear alkenyl group having 6 to 10 carbon atoms. The hydrogen atoms in the alkyl and alkenyl groups may be substituted with monovalent alicyclic groups having 3 to 10 carbon atoms and / or monovalent aromatic groups having 6 to 10 carbon atoms, and the -CH2- groups in the alkyl and alkenyl groups may be substituted with divalent alicyclic groups having 3 to 10 carbon atoms and / or divalent aromatic groups having 6 to 10 carbon atoms.

[0114] In the group represented by the general formula (b-1), R b1 and R b2 Each of these groups is preferably an alkyl group having 1 to 30 carbon atoms or an alkenyl group having 2 to 30 carbon atoms, more preferably an alkyl group having 2 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, even more preferably an alkyl group having 2 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and still more preferably a linear alkyl group having 3 to 5 carbon atoms or a linear alkenyl group having 3 to 5 carbon atoms. The hydrogen atoms in the alkyl and alkenyl groups may be substituted with monovalent alicyclic groups having 3 to 10 carbon atoms and / or monovalent aromatic groups having 6 to 10 carbon atoms, and the -CH2- groups in the alkyl and alkenyl groups may be substituted with divalent alicyclic groups having 3 to 10 carbon atoms and / or divalent aromatic groups having 6 to 10 carbon atoms.

[0115] X a1 and X a2 Preferably, it is a sulfur atom. Sulfur atoms are atoms that make up sulfide solid electrolytes, and they are preferred because they cause little change in composition and result in a similar crystal structure even if the sulfide solid electrolyte contains an organic group containing a sulfur atom.

[0116] (modifier) The modifier in this embodiment is an agent used to introduce an organic group into P2S5. Modified P2S5 is P2S5 containing organic groups, and can be produced in the same manner as the mixing of P2S5 and the modifier described above. Further drying, heating, and pulverization may be performed as needed. The modifier is to be mixed only with P2S5 and is different from the complexing agent described later, which is to be mixed with compounds containing halogen atoms. The modifier is an agent used to introduce an organic group to P2S5, and should be capable of forming a covalent bond between the phosphorus atom of P2S5 and the heteroatom in the organic group. Preferably, the modifier has at least one group selected from those represented by general formulas (a-1), (a-2), and (b-1) in its structure.

[0117] More specifically, the modifier is preferably a compound represented by general formula (A-1), (A-2), or (B-1), and more preferably a compound represented by general formula (A-1) or (B-1).

[0118] [ka]

[0119] (In the formula, R A1 R a1 It expresses the same meaning as R A2 R a2 It expresses the same meaning as R B1 R b1 It expresses the same meaning as R B1 R b2 It expresses the same meaning as X A2 X a2 It expresses the same meaning as Y A1 and Y A2 Each of these independently represents a chlorine atom, a bromine atom, an iodine atom, an -OH group, or an -SH group.

[0120] R A1 , R A2 , R B1 , R B1and X A2 These correspond to the R a1 , R a2 , R b1 , R b2 and X a2 It is preferable that it be the same group as Y A1 It is preferably an -OH group or an -SH group, more preferably an -SH group, Y A2 It is preferably a chlorine atom or a bromine atom, and more preferably a chlorine atom.

[0121] More specifically, preferred modifiers are thiol compounds, secondary amine compounds, and alcohol compounds. When prioritizing the suppression of the decrease in ionic conductivity of the sulfide solid electrolyte, thiol compounds are preferred; when prioritizing water resistance, secondary amine compounds are preferred; and when prioritizing a balance between suppressing the decrease in ionic conductivity and water resistance, alcohol compounds are preferred.

[0122] As for thiol compounds, Y in the general formula (A-1) above is A1 However, it is an -SH group, R A1 However, it is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 4 to 12 carbon atoms, even more preferably an alkyl group having 6 to 10 carbon atoms, and even more preferably 1-octanthiol.

[0123] As a secondary amine compound, R in the general formula (B-1) is b1 and R b12 Each of these is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 2 to 8 carbon atoms, even more preferably an alkyl group having 3 to 6 carbon atoms, and even more preferably an n-dibutylamine.

[0124] As for alcohol compounds, Y in the general formula (A-1) above. A1 However, it is an -OH group, R A1However, it is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 4 to 12 carbon atoms, even more preferably an alkyl group having 6 to 10 carbon atoms, and even more preferably 1-octanol.

[0125] (electrolyte precursor) In the method for producing a sulfide solid electrolyte of this embodiment, it is preferable that the sulfide solid electrolyte can be produced by mixing without using high temperatures, by going through an electrolyte precursor. Electrolyte precursors refer to complexed precursors of sulfide solid electrolytes. The aforementioned electrolyte precursor is composed of a complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups, and is characterized in that, in X-ray diffraction measurements, a peak different from the peak derived from the raw material is observed in the X-ray diffraction pattern. It includes a complex crystal composed of a complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups. Simply mixing the raw material components alone resulted in the observation of peaks originating from the raw materials in the X-ray diffraction pattern. However, by mixing the raw material components with the complexing agent, peaks different from those originating from the raw materials were observed. This confirmed that the electrolyte precursor (complex crystal) has a structure clearly different from the raw materials themselves contained in the raw material components. Furthermore, the electrolyte precursor (complex crystal) is characterized by having a structure different from that of crystalline solid electrolytes. This has also been confirmed by X-ray diffraction patterns.

[0126] The complex crystal is composed of a complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and organic groups, and it is presumed that typically, the lithium atoms and other atoms form a complex structure in which they are directly bonded, with or without the complexing agent. The presence of the complexing agent in the complex crystal can be confirmed, for example, by gas chromatography analysis. Specifically, the complexing agent contained in the complex crystal can be quantified by dissolving the electrolyte precursor powder in methanol and performing gas chromatography analysis on the resulting methanol solution. The amount of complexing agent in the electrolyte precursor varies depending on the molecular weight of the complexing agent, but is usually between 10% by mass and 70% by mass, preferably between 15% by mass and 65% by mass.

[0127] In this embodiment, forming a complex crystal containing halogen atoms is preferable in terms of improving ionic conductivity. By using a complexing agent, a lithium-containing structure such as a PS4 structure and a lithium-containing raw material such as lithium halide bond (coordinate) via the complexing agent, making it easier to obtain a complex crystal in which halogen atoms are more dispersed and fixed, thereby improving ionic conductivity.

[0128] The presence of halogen atoms in an electrolyte precursor in a complex crystal can be confirmed by observing that a predetermined amount of halogen atoms remains in the electrolyte precursor even after solid-liquid separation of the slurry containing the complexing agent. This is because halogen atoms that do not form a complex crystal dissolve more easily than halogen atoms that form a complex crystal and are discharged into the liquid during solid-liquid separation. Furthermore, this can also be confirmed by compositional analysis of the electrolyte precursor or solid electrolyte using ICP analysis (inductively coupled plasma emission spectroscopy), which shows that the proportion of halogen atoms in the electrolyte precursor or solid electrolyte is not significantly lower than the proportion of halogen atoms supplied by the raw materials. The amount of halogen atoms remaining in the electrolyte precursor is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, relative to the initial composition. The upper limit for the amount of halogen atoms remaining in the electrolyte precursor is 100% by mass.

[0129] <Complexing agent> The complexing agent refers to a substance capable of forming a complex with lithium atoms, and has the property of promoting the formation of an electrolyte precursor containing a complex crystal by reacting with sulfides, halides, etc., containing lithium atoms, that are present in the raw material. The modifier and the complexing agent may be the same compound, but the modifier preferably bonds to the phosphorus atom of P2S5 in the modified P2S5 through a covalent bond with the heteroatom, while the complexing agent forms a complex with the lithium atom. Since the modifier is already bonded to P2S5, it does not contribute to the formation of the complex. By using a complexing agent to form an electrolyte precursor containing complex crystals, the elution of specific components such as halogen molecules, which were a cause of reduced conductivity in conventional techniques, can be suppressed, and a solid electrolyte with high ionic conductivity can be obtained.

[0130] As a complexing agent, any agent having the above-mentioned properties can be used without particular limitations. It is especially preferable to include compounds having heteroatoms with atoms that have a high affinity for lithium atoms, such as nitrogen atoms, oxygen atoms, and chlorine atoms, and more preferably to include compounds having groups containing these heteroatoms. This is because these heteroatoms and groups containing these heteroatoms can coordinate (bond) with lithium. The complexing agent is thought to have properties that make it easy to form aggregates by binding with lithium-containing structures such as Li3PS4, which typically contains the PS4 structure and is present as the main structure in the sulfide solid electrolyte obtained by the manufacturing method of this embodiment, as well as with lithium-containing raw materials such as lithium halides. Therefore, by mixing the raw material-containing material with the complexing agent, lithium-containing structures such as the PS4 structure or aggregates via the complexing agent, and lithium-containing raw materials such as lithium halides or aggregates via the complexing agent are evenly distributed, resulting in an electrolyte precursor in which specific components such as halogen atoms are more dispersed and fixed, and as a result, a sulfide solid electrolyte with high ionic conductivity is obtained. Furthermore, the aforementioned organic groups are preferable because they prevent the elution of modified P2S5 and organic groups in the sulfide solid electrolyte, resulting in a more even distribution of organic groups in the sulfide solid electrolyte.

[0131] Therefore, it is preferable that the molecule has at least two coordinating (bonding) heteroatoms, and more preferably that it has two groups containing at least one heteroatom. In this respect, it differs from a modifier. A carbonyl group has two oxygen atoms in its structure, but a carbonyl group has only one. By having a group containing at least two heteroatoms in the molecule, lithium-containing structures such as Li3PS4 containing a PS4 structure and lithium-containing raw materials such as lithium halides can be bonded via at least two heteroatoms in the molecule. As a result, halogen atoms are more dispersed and fixed in the electrolyte precursor, and consequently, a solid electrolyte with high ionic conductivity and suppressed hydrogen sulfide gas generation is obtained. Among the heteroatoms, nitrogen atoms are preferred, and among the groups containing nitrogen atoms, amino groups are preferred; that is, the complexing agent preferably contains a compound having an amino group.

[0132] Amine compounds having amino groups in their molecules are not particularly limited as they can promote the formation of electrolyte precursors, but it is preferable that the complexing agent contains a compound having at least two tertiary amino groups in its molecule. Having such a structure allows lithium-containing structures such as Li3PS4, which includes a PS4 structure, to be bonded to lithium-containing raw materials such as lithium halides via at least two nitrogen atoms in the molecule. As a result, halogen atoms are more dispersed and fixed in the electrolyte precursor, and consequently, a solid electrolyte with high ionic conductivity can be obtained.

[0133] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, which can be used individually or in combination.

[0134] More specifically, aliphatic diamines that are typically preferred include primary aliphatic diamines such as ethylenediamine, diaminopropane, and diaminobutane; secondary aliphatic diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; and tertiary aliphatic 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 provided herein, for example, diaminobutane, unless otherwise specified, includes all isomers relating to the position of the amino group, such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane, as well as all isomers relating to the position of the amino group, such as linear and branched isomers, for butane. The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, even more preferably 6 or more, with an upper limit of preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. Furthermore, the number of carbon atoms in the hydrocarbon group of the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, with an upper limit of preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0135] Typical examples of preferred alicyclic amines include primary alicyclic diamines such as cyclopropanediamine and cyclohexanediamine; secondary alicyclic diamines such as bisaminomethylcyclohexane; and tertiary alicyclic diamines such as N,N,N',N'-tetramethylcyclohexanediamine and bis(ethylmethylamino)cyclohexane. Typical examples of preferred heterocyclic amines include primary heterocyclic diamines such as isophoronediamine; secondary heterocyclic diamines such as piperazine and dipiperidylpropane; and tertiary heterocyclic 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 preferably 16 or less as the upper limit, more preferably 14 or less.

[0136] Furthermore, as aromatic amines, preferred examples include primary aromatic diamines such as phenyldiamine, tolylenediamine, and naphthalenediamine; secondary aromatic diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-bismethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; and tertiary aromatic diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine. The number of carbon atoms in the aromatic amine is preferably 6 or more, more preferably 7 or more, even more preferably 8 or more, with an upper limit of preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0137] The amine compounds used in this embodiment may be substituted with substituents such as alkyl groups, alkenyl groups, alkoxyl groups, hydroxyl groups, cyano groups, or halogen atoms. Although diamines were used as a specific example, it goes without saying that the amine compounds that can be used in this embodiment are not limited to diamines, but include, for example, aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the aforementioned aliphatic diamines; also 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 aforementioned alicyclic diamines. In addition to monoamines such as alicyclic monoamines such as the corresponding monoamine; heterocyclic monoamines corresponding to the heterocyclic diamine; and aromatic monoamines corresponding to the aromatic diamine, other monoamines can also be used. For example, 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.

[0138] Among the above, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the amine is a tertiary amine having a tertiary amino group as the amino group, more preferably a tertiary diamine having two tertiary amino groups, even more preferably a tertiary diamine having two tertiary amino groups at both ends, and even more preferably an aliphatic tertiary diamine having tertiary amino groups at both ends. Among the above amine compounds, as aliphatic tertiary diamines having tertiary amino groups at both ends, tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane are preferred, and considering ease of availability, tetramethylethylenediamine and tetramethyldiaminopropane are preferred.

[0139] Other complexing agents besides amine compounds include, for example, compounds having groups containing heteroatoms such as oxygen atoms, chlorine atoms, or other halogen atoms, which have a high affinity for lithium atoms and can be listed as other complexing agents besides the amine compounds mentioned above. Compounds having groups other than amino groups, such as nitro groups and amide groups, which contain a nitrogen atom as a heteroatom, can also produce similar effects.

[0140] Other complexing agents include, for example, alcoholic solvents such as ethanol and butanol; esteric solvents such as ethyl acetate and butyl acetate; aldehyde solvents such as formaldehyde, acetaldehyde, and dimethylformamide; ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; etheric solvents such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, diethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole; 2-methoxyethyl acetate, 2-ethoxyethyl acetate (ethylene glycol acetate), and 2-methoxy-1-methyl ethyl acetate. Examples of solvents include glycol ester solvents such as 2-ethoxymethylethyl acetate, 2-(2-ethoxyethoxy)ethyl acetate, (2-acetoxyethoxy)methyl acetate, 1-methyl-2-ethoxyethyl acetate (propylene glycol monoethyl ether acetate), ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, and 2-methoxyethyl 3-(2-methoxyethoxy)propionate; halogen atom-containing aromatic hydrocarbon solvents such as trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; and solvents containing carbon atoms and heteroatoms such as acetonitrile, dimethyl sulfoxide, and carbon disulfide. Among these, ether solvents and glycol ester solvents are preferred, and glycol ester solvents are more preferred. Furthermore, among ether-based solvents, diethyl ether, diisopropyl ether, dibutyl ether, and tetrahydrofuran are more preferred, and diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred. Among glycol ester-based solvents, acetate esters are more preferred, and 2-methoxy-1-methylethyl acetate and 2-ethoxymethylethyl acetate are even more preferred.

[0141] From the viewpoint of efficiently obtaining the effect of using the complexing agent, which is to form an electrolyte precursor in which halogen atoms are more dispersed and fixed, thereby obtaining a solid electrolyte with high ionic conductivity, the amount of complexing agent used per 1 g of total mass of the raw material is preferably 0.1 to 30 mL, more preferably 0.5 to 20 mL, and even more preferably 1.0 to 10 mL.

[0142] <Solvent> In this embodiment, it is preferable to add a solvent to "mixing" and "grinding". By mixing the raw material components with the complexing agent using a solvent, the effects of using the complexing agent, namely the formation of electrolyte precursors that react with lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, are promoted. This makes it easier to evenly distribute lithium-containing structures such as PS4 structures or aggregates via the complexing agent, lithium-containing raw materials such as lithium halides or aggregates via the complexing agent, and an electrolyte precursor with more dispersed and fixed halogen atoms is obtained, resulting in the effect of obtaining high ionic conductivity.

[0143] This embodiment is a so-called heterogeneous method, and it is preferable that the electrolyte precursor precipitates without completely dissolving in the solvent or liquid complexing agent. In this embodiment, the solubility of the electrolyte precursor can be adjusted by adding a solvent. In particular, halogen atoms tend to dissolve easily from the electrolyte precursor, so by adding a solvent, the dissolution of halogen atoms can be suppressed to obtain the desired electrolyte precursor. As a result, a crystalline solid electrolyte with high ionic conductivity can be obtained via an electrolyte precursor in which specific components such as halogens are dispersed. Additionally, the solvent can be further added to the slurry of the electrolyte precursor after mixing.

[0144] As solvents having such properties, solvents with a solubility parameter of 10 or less are preferred. In this specification, the solubility parameter is described in various literature, for example, the "Chemical Handbook" (published in 2004, revised 5th edition, Maruzen Co., Ltd.), and is a value calculated by the following formula (1): δ((cal / cm) 3 ) 1 / 2 ) is also called the Hildebrand parameter or SP value.

[0145]

number

[0146] By using a solvent with a solubility parameter of 10 or less, the solvent becomes less likely to dissolve halogen atoms, raw material components containing halogen atoms such as lithium halide, and components containing halogen atoms that constitute the complex crystal in the electrolyte precursor (for example, aggregates of lithium halide and complexing agent) compared to the modifier and complexing agent. This makes it easier to fix the organic groups and halogen atoms within the electrolyte precursor, resulting in the presence of organic groups and halogen atoms in a good dispersion state in the resulting modified P2S5, electrolyte precursor, and sulfide solid electrolyte, making it easier to obtain a sulfide solid electrolyte with high ionic conductivity and excellent water resistance. In other words, the solvent used in this embodiment preferably has properties that do not dissolve or do not dissolve the modifier or electrolyte precursor, and it is more preferable that the solvent contains raw material components, modifier, complexing agent, and electrolyte precursor. From a similar viewpoint, 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.

[0147] More specifically, the solvent used in this embodiment can be a wide range of solvents that have been conventionally used in the production of solid electrolytes. Examples include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; and carbon-containing solvents such as alcohol-based solvents, ester-based solvents, aldehyde-based solvents, ketone-based solvents, ether-based solvents, and solvents containing carbon atoms and heteroatoms. From these, it is preferable to appropriately select and use those whose solubility parameters fall within the aforementioned range.

[0148] More specifically, examples include aliphatic hydrocarbon solvents such as hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; alcoholic solvents such as ethanol and butanol; esteric solvents such as ethyl acetate and butyl acetate; aldehyde solvents such as formaldehyde, acetaldehyde, and dimethylformamide; ketone solvents such as acetone and methyl ethyl ketone; etheric solvents such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and heteroatoms such as acetonitrile, dimethyl sulfoxide, and carbon disulfide.

[0149] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred. From the viewpoint of obtaining higher ionic conductivity with greater stability, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents are preferred, with heptane, cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, toluene, and ethylbenzene being more preferred, and heptane, cyclohexane, methylcyclohexane, and ethylcyclohexane being even more preferred. The solvent used in this embodiment is preferably one of the organic solvents exemplified above, and is different from the organic solvent used for the complexing agent. In this embodiment, these solvents may be used individually or in combination of several types.

[0150] The amount of solvent used per gram of total mass of the raw material is preferably 5 to 50 mL, more preferably 5 to 30 mL, and even more preferably 5 to 20 mL, in order to obtain a sulfide solid electrolyte with high ionic conductivity and water resistance.

[0151] [Modified P2S5 containing organic groups for the production of sulfide solid electrolytes] The modified P2S5 for the production of sulfide solid electrolytes in this embodiment must be modified P2S5 for the production of sulfide solid electrolytes that includes an organic group. In the method for producing the sulfide solid electrolyte, if modified P2S5 for the production of sulfide solid electrolytes, which is equipped with organic groups, is used, a sulfide solid electrolyte with high ionic conductivity and excellent water resistance can be produced. Therefore, the modified P2S5 is as described above.

[0152] (Applications of sulfide solid electrolytes) The sulfide solid electrolyte of this embodiment has high ionic conductivity and excellent water resistance, making it suitable for use as an electrode composite material for lithium-ion batteries and in lithium-ion batteries themselves. It is particularly preferable when lithium is used as the conductive element. The sulfide solid electrolyte of this embodiment may be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer.

[0153] Furthermore, it is preferable that the battery uses a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and known current collectors can be used. For example, a layer coated with gold or the like, which reacts with the sulfide solid electrolyte, such as Au, Pt, Al, Ti, or Cu, can be used.

[0154] [Electrode composite material] The electrode mixture of this embodiment must include the sulfide solid electrolyte and the electrode active material described later.

[0155] (electrode active material) As for the electrode active materials, a positive electrode active material and a negative electrode active material are used depending on whether the electrode composite material is used as the positive electrode or the negative electrode.

[0156] The positive electrode active material can be used without particular limitations, as long as it is capable of promoting battery chemical reactions involving the movement of lithium ions, preferably due to atoms that exhibit ionic conductivity in relation to the negative electrode active material, and preferably lithium atoms. Examples of positive electrode active materials capable of such lithium ion insertion and removal include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0157] Preferred oxide-based cathode 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 cathode active materials include titanium sulfide (TiS2), molybdenum sulfide (MoS2), iron sulfide (FeS, FeS2), copper sulfide (CuS), and nickel sulfide (Ni3S2). In addition to the aforementioned positive electrode active material, niobium selenide (NbSe3) and other materials can also be used. The positive electrode active material can be used individually or in combination of multiple types.

[0158] As the negative electrode active material, any material that can promote a battery chemical reaction involving the movement of lithium ions, preferably caused by lithium atoms, can be used, such as an atom adopted as an atom that exhibits ionic conductivity, preferably a metal that can form an alloy with lithium atoms, an oxide thereof, or an alloy of said metal and lithium atoms. As such a negative electrode active material capable of lithium ion insertion and removal, any material known as a negative electrode active material in the battery field can be used without 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 that can form alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0159] The electrode active material used in this embodiment may have a coating layer with its surface coated. Examples of the material for forming the coating layer include ion conductors such as nitrides, oxides, or composites thereof of atoms that exhibit ionic conductivity in sulfide solid electrolytes, preferably lithium atoms. Specifically, lithium nitride (Li3N), conductors having a silicon-type crystal structure such as Li 4-2x Zn x GeO4, conductors having a Li3PO4-type framework structure such as Li 4-x Ge 1-x P x S4 and other conductors having a thiolsilicon-type crystal structure, conductors having a perovskite-type crystal structure such as La 2 / 3-x Li 3x TiO3, conductors having a NASICON-type crystal structure such as LiTi2(PO4)3, etc. Also, Li y Ti 3-y O4(0 < y < 3), lithium titanates such as Li4Ti5O 12 (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 systems, Li2O-B2O3-ZnO systems, Li2O-Al2O3-SiO2-P2O5-TiO2 systems, etc.

[0160] The electrode active material having a coating layer can be obtained, for example, by adhering a solution containing various atoms constituting the material for forming the coating layer to the surface of the electrode active material, and preferably firing the electrode active material after adhesion at 200°C or higher and 400°C or lower. Here, as the solution containing various atoms, for example, a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, tantalum isopropoxide, etc. may be used. In this case, as the solvent, alcohol-based solvents such as ethanol and butanol, aliphatic hydrocarbon solvents such as hexane, heptane, and octane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene, etc. may be used. Furthermore, the aforementioned adhesion can be achieved by immersion, spray coating, or the like.

[0161] The firing temperature is preferably 200°C to 400°C, more preferably 250°C to 390°C, from the viewpoint of improving manufacturing efficiency and battery performance, and the firing time is usually 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0162] The coverage rate of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100%, based on 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, with an upper limit of preferably 30 nm or less, and 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 ratio can be calculated from the thickness of the coating layer, elemental analysis values, and BET specific surface area.

[0163] (Other ingredients) The electrode mixture of this embodiment may contain other components in addition to the sulfide solid electrolyte and electrode active material, such as conductive materials and binders. That is, the method for manufacturing the electrode mixture of this embodiment may use other components in addition to the sulfide solid electrolyte and electrode active material, such as conductive materials and binders. The conductive materials, binders, and other components may be added to and mixed with the sulfide solid electrolyte and electrode active material when mixing them. Examples of conductive materials that improve battery performance by enhancing electronic conductivity include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolysis vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0164] Using a binder improves the strength of the positive and negative electrodes when they are fabricated. There are no particular restrictions on the binder as long as it can impart functions such as binding and flexibility. Examples 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 resins, acrylic polyol resins, polyvinyl acetal resins, polyvinyl butyral resins, and silicone resins.

[0165] In electrode composite materials, the mixing ratio (mass ratio) of electrode active material and sulfide solid electrolyte 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, considering both improved battery performance and manufacturing efficiency.

[0166] When a conductive material is included, there are no particular restrictions on the content of the conductive material in the electrode composite, but in order to improve battery performance and take into account manufacturing efficiency, it is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, with an upper limit of preferably 10% by mass or less, preferably 8% by mass or less, and even more preferably 5% by mass or less. Furthermore, when a binder is included, there are no particular restrictions on the binder content in the electrode composite material. However, considering the improvement of battery performance and manufacturing efficiency, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, with an upper limit of preferably 20% by mass or less, preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0167] [Lithium-ion battery] The lithium-ion battery of this embodiment must include at least one selected from the sulfide solid electrolyte of this embodiment and the electrode composite material.

[0168] The lithium-ion battery of this embodiment is not particularly limited in its configuration as long as it contains either the sulfide solid electrolyte of this embodiment or the electrode composite material containing the same, and can have the configuration of a commonly used lithium-ion battery.

[0169] The lithium-ion battery of this embodiment preferably comprises, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. Preferably, the electrode composite material of this embodiment is used for the positive electrode layer and the negative electrode layer, and preferably, the sulfide solid electrolyte of this embodiment is used for the electrolyte layer.

[0170] Furthermore, any known current collector can be used. For example, a layer coated with gold or the like, which reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, can be used. [Examples]

[0171] The present invention will now be specifically described with reference to examples, but the present invention is not limited in any way by these examples.

[0172] (1) Measurement method (1-1) Measurement of ionic conductivity In this embodiment, the ionic conductivity was measured as follows. From a sulfide solid electrolyte, a diameter of 10 mm (cross-sectional area S: 0.785 cm²) 2 ), circular pellets with a height (L) of 0.1 to 0.3 cm were formed as samples. Electrode terminals were taken from the top and bottom of the samples, and measurements were taken at 25°C using the AC impedance method (frequency range: 1 MHz to 100 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. Near the right end of the arc observed in the high-frequency region, the real part Z'(Ω) at the point where -Z''(Ω) is minimized was taken as the bulk resistance R(Ω) of the electrolyte, and the ionic conductivity σ(S / cm) was calculated according to the following formula.

[0173] R = ρ(L / S) σ = 1 / ρ

[0174] (1-2) Water resistance evaluation (H2S generation amount) The exposure test apparatus (Figure 2) mainly consists of a flask 10 for humidifying nitrogen, a static mixer 20 for mixing humidified and unhumidified nitrogen, a dew point meter 30 (VAISALA M170 / DMT152) for measuring the moisture content of the mixed nitrogen, a double reaction tube 40 for placing the sample to be measured, a dew point meter 50 for measuring the moisture content of the nitrogen discharged from the double reaction tube 40, and a hydrogen sulfide meter 60 (AMI Model 3000RS) for measuring the hydrogen sulfide concentration contained in the discharged nitrogen. These components are connected by tubes (not shown). The temperature of the flask 10 is set to 10°C by a cooling tank 11. Furthermore, 6mm diameter Teflon® tubing was used to connect each component. In Figure 2, the tubes are not shown, and instead, the flow of nitrogen is indicated by arrows.

[0175] The evaluation procedure was as follows: Approximately 0.15 g of the powder sample 41 was weighed into a nitrogen glow box with a dew point of -80°C, and placed inside the reaction tube 40, sandwiched between quartz wool 42, and then sealed.

[0176] Nitrogen was supplied into apparatus 1 from a nitrogen source (not shown) at 0.02 MPa. The supplied nitrogen passed through a bifurcated pipe BP, and a portion was supplied to flask 10 for humidification. The remainder was supplied directly to the static mixer 20 as unhumidified nitrogen. The amount of nitrogen supplied to flask 10 was adjusted by a needle valve V. The dew point is controlled by adjusting the flow rates of unhumidified nitrogen and humidified nitrogen using a flow controller / mass flow meter (KOFLOC: MODEL8500) FM. Specifically, the flow rate of unhumidified nitrogen was 750-800 mL / min and the flow rate of humidified nitrogen was 30-90 mL / min, both were supplied to the static mixer 20 for mixing, and the dew point of the mixed gas (a mixture of unhumidified and humidified nitrogen) was confirmed using a dew point meter 30.

[0177] After adjusting the dew point to -20°C, the three-way stopcock 43 was rotated to allow the mixed gas to flow through the reaction tube 40 for 2 hours. The amount of hydrogen sulfide contained in the mixed gas that passed through the sample 41 was measured using a hydrogen sulfide meter 60. The amount of hydrogen sulfide generated during this time was calculated on a per-gram basis (unit: cc / g). After measurement, the gas was passed through an alkaline trap 70 to remove hydrogen sulfide. After exposing the sample for a predetermined time, the supply of humidified nitrogen was stopped, and the reaction tube 40 was sealed with unhumidified nitrogen. (1-3) Average particle size (D 50 ) The volume-based average particle size was measured using a laser diffraction / scattering particle size distribution analyzer ("Partica LA-950V2 model LA-950W2," manufactured by Horiba, Ltd.). A mixture of dehydrated toluene (Wako Pure Chemical Industries, special grade) and tertiary butyl alcohol (Wako Pure Chemical Industries, special grade) in a weight ratio of 93.8:6.2 was used as the dispersion medium. 50 ml of the dispersion mixture was injected into the flow cell of the analyzer, circulated, and then the sample to be measured was added and subjected to ultrasonic treatment before measuring the particle size distribution. The amount of sample to be measured was adjusted so that the red light transmittance (R) corresponding to the particle concentration was between 90-90% and the blue light transmittance (B) was between 70-90% on the measurement screen specified by the analyzer. In addition, a refractive index of 2.16 was used for the sample to be measured and a refractive index of 1.49 was used for the dispersion medium in the calculation conditions. In setting the distribution pattern, the number of iterations was fixed at 15 for particle size calculation.

[0178] (1-4) Inductively coupled plasma (ICP) emission spectrometer (composition determination) The sulfide solid electrolyte powder was weighed and collected in a vial under an argon atmosphere. KOH alkaline aqueous solution was added to the vial, and the sample was dissolved while taking care to collect sulfur. The solution was then diluted as needed to prepare the measurement solution. The resulting measurement solution was measured using a Paschenrunge-type ICP-OES instrument (SPECTRO ARCOS, SPECTRO Corporation) to determine its composition.

[0179] Calibration curve solutions were prepared using 1000 mg / L standard solutions for ICP measurement for Li, P, and S; 1000 mg / L standard solution for ion chromatography for Br; and potassium iodide (reagent grade) for I. For each sulfide solid electrolyte, two measurement solutions were prepared, and four measurements were taken with each solution. The average value was then calculated. The composition was determined from the average of the measurements of these two solutions. From the obtained elemental ratios, the content of phosphorus atoms, sulfur atoms, and halogen atoms relative to the lithium atom content was calculated.

[0180] (2) Example of preparation of modified P2S5 Under an inert gas atmosphere in a glove box, 5.0 g (22.5 mmol) of P2S5 was weighed into a Schlenk flask containing a stirring bar, and 50 mL of toluene was added as the solvent. 67.2 mg of 1-octanthiol (0.0100 mol per 1 mol of phosphorus atoms in P2S5, corresponding to the modifier / P ratio in Table 1) was then added as a modifier, and the mixture was stirred at 120°C for 2 hours. After stopping the stirring, the pressure was reduced using a vacuum pump for 2 hours, and the liquid toluene was dried to obtain modified P2S5(1). Modified P2S5(2) to (6) were obtained using the modifiers listed in Table 1, except that the modifier / P listed in Table 1 was used.

[0181] [Table 1]

[0182] (Example 1) Under an inert gas atmosphere in a glove box, 1.91 g of the modified P2S5(1) described above, 1.17 g of Li2S, 0.369 g of LiBr, and 0.569 g of LiI were weighed into a Schlenk flask containing a stirring bar as raw material components. 8.9 mL of N,N,N',N'-tetramethylethylenediamine (TMEDA) was added as a complexing agent, and 40 mL of cyclohexane was added as a solvent. The mixture was stirred at room temperature for 3 days without external heating. After stopping the stirring, the pressure was reduced using a vacuum pump for 2 hours, and the liquid TMEDA and cyclohexane were dried to obtain the powdered electrolyte precursor (1).

[0183] The obtained electrolyte precursor (1) was heated at 110°C for 2 hours to obtain amorphous sulfide solid electrolyte (1). Furthermore, the obtained amorphous sulfide solid electrolyte (1) was heated at 180°C for 2 hours to obtain a crystalline sulfide solid electrolyte (1).

[0184] Figure 3 shows the XRD patterns of the raw material containing the modified P2S5 used, the electrolyte precursor (1), the amorphous sulfide solid electrolyte (1), and the crystalline sulfide solid electrolyte (1). The electrolyte precursor (1) showed a different pattern from the raw material containing, confirming that the raw material containing was consumed by the stirring. Furthermore, it was confirmed that the electrolyte precursor (1) became the amorphous sulfide solid electrolyte (1) upon heating, and that further heating and crystallization resulted in the crystalline sulfide solid electrolyte (1) containing a thiolysicon region II type crystal structure.

[0185] (Examples 2) to (Examples 6) Amorphous sulfide solid electrolytes (2) to (6) and crystalline sulfide solid electrolytes (2) to (6) were obtained in the same manner as in Example 1, except that modified P2S5 as listed in Table 2 was used in the amounts listed in Table 2, and Li2S was used in the amounts listed in Table 2, under an inert gas atmosphere in a glove box. From the XRD patterns of crystalline sulfide solid electrolytes (2) to (6), it was confirmed that they contained a thiolysicon region type II crystal structure.

[0186] [Table 2]

[0187] (Comparative Example 1) Under an inert gas atmosphere in a glove box, 1.89 g of unmodified P2S5, 1.17 g of Li2S, 0.369 g of LiBr, and 0.569 g of LiI were weighed into a Schlenk flask containing a stirring bar. 8.9 mL of N,N,N',N'-tetramethylethylenediamine (TMEDA) was added as a complexing agent, and 40 mL of cyclohexane was added as a solvent. The mixture was stirred at room temperature for 3 days without external heating. After stopping the stirring, the pressure was reduced using a vacuum pump for 2 hours, and the liquid TMEDA and cyclohexane were dried to obtain a powdered electrolyte precursor. The obtained electrolyte precursor was heated at 110°C for 2 hours to obtain an amorphous sulfide solid electrolyte. Furthermore, the obtained amorphous sulfide solid electrolyte (C1) was heated at 180°C for 2 hours to obtain a crystalline sulfide solid electrolyte (C1). From the XRD pattern of the crystalline sulfide solid electrolyte (C1), it was confirmed that it contained a thiolysicon region type II crystal structure.

[0188] (Comparative Example 2) Under an inert gas atmosphere in a glove box, 4.0 g of the crystalline sulfide solid electrolyte (C1) obtained in Comparative Example 1 was weighed into a Schlenk vial containing a stirring bar, and 50 mL of toluene was added as the solvent. After adding 250 mg of octanthiol, the mixture was stirred at room temperature for 12 hours. Stirring was stopped, and the pressure was reduced using a vacuum pump for 2 hours to dry the liquid toluene and octanthiol, thereby obtaining the crystalline sulfide solid electrolyte (C2). The XRD pattern of the crystalline sulfide solid electrolyte (C2) confirmed that it contained a thiolysicon region type II crystal structure.

[0189] (Comparative Example 3) In Comparative Example 1, a crystalline sulfide solid electrolyte (C3) was obtained in the same manner except that 110 mg of dibutylamine was used instead of octanthiol. From the XRD pattern of the crystalline sulfide solid electrolyte (C3), it was confirmed that it contained a thiolysicon region type II crystal structure.

[0190] Table 3 shows the ratios of the contents (mol) of sulfur atoms, phosphorus atoms, and halogen atoms per content (mol) of lithium atoms in each of the obtained sulfide solid electrolytes. For Examples 4 to 6, the contents per content of lithium atoms of nitrogen atoms or oxygen atoms (in the nitrogen atom / oxygen atom item in Table 3) are also described in Table 3. The ionic conductivity and the amount of H2S generation are described in Table 4.

[0191]

Table 3

[0192] From the results of Examples 1 to 6, it was found that the sulfide solid electrolyte of the embodiment of the present application has the same ionic conductivity as the sulfide solid electrolyte of Comparative Example 1.

[0193]

Table 4

[0194] From FIG. 4, it was confirmed that the sulfide solid electrolyte (Examples 1 to 6) of the present embodiment has a greater effect of suppressing the amount of H2S generation than the sulfide solid electrolyte of Comparative Example 1 into which no organic compound group is introduced. Further, it was confirmed that the effect of suppressing the amount of H2S generation is greater than that of the sulfide solid electrolyte (corresponding to Comparative Examples 2 and 3) in which an organic compound group is introduced into the sulfide solid electrolyte as in Patent Document 1. The sulfide solid electrolytes of Examples 1 to 3 using a thiol-based compound as a modifier are excellent in suppressing a decrease in ionic conductivity, the sulfide solid electrolyte of Example 4 using an alcohol-based compound as a modifier has a balance between suppressing a decrease in ionic conductivity and water resistance, and the sulfide solid electrolytes of Examples 5 and 6 using a secondary amine-based compound as a modifier tend to be excellent in water resistance.

[0195] Furthermore, when an electrode mixture and a lithium ion battery were manufactured using the crystalline sulfide solid electrolyte (1), it was confirmed that they had excellent battery characteristics. [Industrial applicability]

[0196] According to the method for producing a sulfide solid electrolyte of this embodiment, a crystalline sulfide solid electrolyte with high ionic conductivity and suppression of hydrogen sulfide gas generation can be easily produced. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is suitably used in lithium-ion batteries, particularly in lithium-ion batteries used in information-related equipment and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. mixing a raw material content containing two or more raw materials; the raw material contains at least one atom selected from a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, The raw material contains modified P ２ S ５ A method for producing a sulfide solid electrolyte, comprising:

2. The modified P ２ S ５ P having an organic group ２ S ５ The method for producing a sulfide solid electrolyte according to claim 1,

3. The method for producing a sulfide solid electrolyte according to claim 2 , wherein the organic group contains a heteroatom.

4. The modified P ２ S ５ However, the modified P ２ S ５ P inside ２ S ５ The method for producing a sulfide solid electrolyte according to claim 3 , wherein the phosphorus atom and the heteroatom are covalently bonded to each other.

5. The method for producing a sulfide solid electrolyte according to claim 3 or 4, wherein the heteroatom is at least one selected from a sulfur atom, an oxygen atom, and a nitrogen atom.

6. The method for producing a sulfide solid electrolyte according to claim 2 or 3, wherein the organic group is at least one selected from groups represented by general formulas (a-1), (a-2), and (b-1): 【Chemistry 1】 (wherein * represents P ２ S ５ represents the binding site with ａ１ , R ａ２ , R ｂ１ and R ｂ２ each independently represents a monovalent organic group; X ａ１ and X ａ２ each independently represents an oxygen atom or a sulfur atom.

7. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the mixing is performed using a stirrer, a mixer, or a pulverizer.

8. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the mixing step comprises mixing the raw material contents with a complexing agent.

9. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the mixing is carried out in a solvent.

10. The method for producing a sulfide solid electrolyte according to claim 1 or 2, further comprising heating.

11. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the sulfide solid electrolyte comprises a thiolisiconregion II type crystal structure.

12. containing a lithium atom, a sulfur atom, a phosphorus atom, a halogen atom, and an organic group; A sulfide solid electrolyte, wherein the ratio of the contents (mol) of sulfur atoms, phosphorus atoms, and halogen atoms per content (mol) of lithium atoms is lithium atoms:sulfur atoms:phosphorus atoms:halogen atoms=1:1.1000-1.2000:0.2000-0.3500:0.1400-0.1550.

13. An electrode mixture comprising the sulfide solid electrolyte according to claim 12 and an electrode active material.

14. A lithium ion battery comprising at least one of the sulfide solid electrolyte according to claim 12 and the electrode mixture according to claim 13.

15. Modified P for the production of sulfide solid electrolytes with organic groups ２ S ５ .

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