Method for producing sulfide solid electrolyte

Abstract

Provided is a method for producing a sulfide solid electrolyte capable of producing a sulfide solid electrolyte having a target crystal structure and capable of reducing the energy input during production, the method including heating (heating (1)) while bringing hydrogen sulfide into contact with a starting material-containing substance, the temperature (T1 (DEG C)) of the heating (1) being 170 DEG C or less.

Description

Technical Field

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

[0002] In recent years, with the rapid spread of information-related and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries used as their power sources has also gained significant attention. Batteries used for these applications have traditionally used electrolytes containing flammable organic solvents. However, by making batteries fully solid-state, the need for flammable organic solvents is eliminated. This simplifies safety features, reduces manufacturing costs, and improves productivity. Consequently, the development of batteries that replace the electrolyte with a sulfide solid electrolyte layer, known as all-solid-state batteries, is underway.

[0003] Sulfide solid electrolytes are conventionally known as sulfide solid electrolytes used in sulfide solid electrolyte layers. Although sulfide solid electrolytes have high ion conductivity, there is a demand for the development of a simpler method for producing high-quality sulfide solid electrolytes.

[0004] As a method for producing a sulfide solid electrolyte, a method of heating a raw material for producing a sulfide solid electrolyte together with hydrogen sulfide (H 2 S) is known (Patent Documents 1 to 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-167845

[0008] Patent Document 2: Japanese Patent Application Publication No. 2018-97954

[0009] Patent Document 3: International Publication No. 2020 / 213340 Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a sulfide solid electrolyte that can produce a sulfide solid electrolyte having a desired crystal structure and can reduce energy input during production.

[0012] Solutions for solving the above technical problems

[0013] The method for producing a sulfide solid electrolyte of the present invention is a method for producing a sulfide solid electrolyte that can produce a sulfide solid electrolyte having a target crystal structure while reducing the energy input during production.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide a method for producing a sulfide solid electrolyte that can produce a sulfide solid electrolyte having a target crystal structure and can reduce energy input during production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flowchart illustrating an example of a preferred mode of the production method of this embodiment.

[0017] Figure 2 These are the XRD patterns of the crystalline sulfide solid electrolyte (1) and the amorphous sulfide solid electrolyte (1) obtained in Example 1.

[0018] Figure 3 These are the XRD patterns of the crystalline sulfide solid electrolyte (2) and the amorphous sulfide solid electrolyte (2) obtained in Example 2.

[0019] Figure 4 These are the XRD patterns of the crystalline sulfide solid electrolyte (3) and the amorphous sulfide solid electrolyte (3) obtained in Example 3.

[0020] Figure 5 These are the XRD patterns of the crystalline sulfide solid electrolyte (4) and the amorphous sulfide solid electrolyte (4) obtained in Example 4.

[0021] Figure 6 These are XRD patterns of the crystalline sulfide solid electrolyte (C1) and the amorphous sulfide solid electrolyte (C1) obtained in Comparative Example 1.

[0022] Figure 7 These are the XRD patterns of the crystalline sulfide solid electrolyte (5) and the amorphous sulfide solid electrolyte (5) obtained in Example 5.

[0023] Figure 8 These are the XRD patterns of the crystalline sulfide solid electrolyte (6) and the amorphous sulfide solid electrolyte (6) obtained in Example 6. DETAILED DESCRIPTION

[0024] Hereinafter, an embodiment of the present invention (hereinafter sometimes referred to as "the present embodiment") will be described. In addition, in this specification, the upper and lower limits of the numerical ranges of "above", "below", and "to" are numerical values that can be combined arbitrarily, and the numerical values of the examples can also be used as the upper and lower limits. In addition, any preferred provisions can be adopted. That is, one preferred provision can be combined with another preferred provision or multiple preferred provisions. It can be said that the combination of preferred provisions is more preferred.

[0025] (Discovery made by the present inventors to complete the present invention)

[0026] The present inventors have conducted intensive studies to solve the above-mentioned technical problems, and as a result, have found the following matters and have completed the present invention.

[0027] In Patent Document 1, lithium sulfide and phosphorus sulfide are heated together with H2S to produce a sulfide solid electrolyte. When producing the sulfide solid electrolyte at high temperatures, such as 190°C or higher, H2S is used to suppress the release of sulfur atoms. Therefore, the purpose of using H2S differs from the production method of the present invention, which uses H2S to reduce the heating temperature during production of the sulfide solid electrolyte. Furthermore, the production of the sulfide solid electrolyte described in Patent Document 1 requires high temperatures, and H2S is used to address the problems that arise at these high temperatures. Therefore, the concept of lowering the production temperature is not disclosed, significantly different from the present invention, which relates to a production method that does not require high temperatures.

[0028] Patent Document 2 uses H₂S to remove elemental sulfur contained in the sulfide solid electrolyte material during the production of the sulfide solid electrolyte. This purpose differs significantly from that of the present invention. Patent Document 2 heats the sulfide solid electrolyte material at 200°C while circulating a gas containing H₂S. This is the temperature required to produce the sulfide solid electrolyte from the sulfide solid electrolyte material. Therefore, there is no disclosure of the concept of lowering this temperature, significantly different from the present invention, which relates to a production method that does not require high temperatures.

[0029] Patent Document 3 uses H2S to remove oxygen-containing compounds such as LiOH contained in Li2S, a purpose significantly different from that of the present invention. Furthermore, Patent Document 3 includes a firing step at 500°C under a flow of H2S gas, significantly different from the heating temperature of the present invention.

[0030] If the sulfide solid electrolyte is heated to a high temperature during production, the resulting sulfide solid electrolyte will also contain crystal structures other than the target crystal structure, making it impossible to obtain a sulfide solid electrolyte with high ionic conductivity. Furthermore, for example, in Patent Document 1, the raw materials are heated in the presence of H2S, but the high temperature is maintained for a long time by holding the raw materials at 230°C for 12 hours, requiring a large amount of energy to produce the sulfide electrolyte. This increased energy input during production leads to increased production costs.

[0031] The present inventors focused on the heating of the raw material contents and studied the relationship between the heating atmosphere and the heating temperature. They tried heating the raw material contents while bringing hydrogen sulfide into contact with them (heating (1)) and setting the temperature (T1 (°C)) of the heating (1) to 170°C or lower. They then discovered that when producing a sulfide solid electrolyte, certain reactions occurred by using the raw material contents described later and heating them while bringing them into contact with hydrogen sulfide. They further discovered that by setting T1 to 170°C or lower, the produced sulfide solid electrolyte could obtain the target crystal structure. Based on this understanding, the present inventors completed the following production method of the present embodiment. The production method of the present embodiment does not require high temperature. As a result, the generation of non-target crystal structures generated at high temperatures can be suppressed, and a sulfide solid electrolyte having the target crystal structure can be produced. In addition, since high temperature is not required, the energy input during production can be reduced, so it can be said that productivity is excellent.

[0032] Hereinafter, methods for producing the sulfide solid electrolyte according to the first to twelfth aspects of the present embodiment will be described.

[0033] The method for producing a sulfide solid electrolyte according to the first aspect of the present embodiment is the following method for producing a sulfide solid electrolyte:

[0034] The method includes heating the raw material content while bringing hydrogen sulfide into contact with the raw material content (heating (1)), wherein the temperature (T1 (°C)) of the heating (1) is 170°C or less.

[0035] Figure 1 A flowchart illustrating a preferred embodiment of the method for producing a sulfide solid electrolyte according to this embodiment is shown in FIG. The method of this embodiment allows the heating temperature to be suppressed by heating the raw material while bringing hydrogen sulfide into contact with the raw material. Furthermore, the method may further include pulverization, temperature increase, and heating (2) as described below, as needed.

[0036] In this embodiment, the "raw material content" includes the solid electrolyte raw material when producing the sulfide solid electrolyte, and refers to a single substance or compound containing lithium atoms, phosphorus atoms, and sulfur atoms, or a mixture thereof. The solid electrolyte raw material may contain halogen atoms as needed.

[0037] In this embodiment, "heating" refers to heating (1) described later, and may further include heating (2) as needed.

[0038] In the present embodiment, the "temperature (T1 (° C.))" of heating (1) refers to the highest temperature in heating (1).

[0039] In this embodiment, the "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere, and the "sulfide solid electrolyte" refers to a solid electrolyte containing lithium atoms, sulfur atoms, and phosphorus atoms and, if necessary, halogen atoms, and having ionic conductivity due to lithium atoms.

[0040] As reasons why the heating temperature can be suppressed, the following assumptions (1) and (2) can be cited, and it is believed that they work individually or in combination. In addition, it is also considered that other factors become dominant factors and the above assumptions (1) and / or (2) work in a subordinate manner.

[0041] Assumption (1) is as follows: the raw material contains compounds that react with H2S, such as lithium hydroxide (LiOH), lithium sulfide (Li2S) and phosphorus pentasulfide (P2S5, usually phosphorus pentasulfide as P4S 10 When a solid electrolyte raw material such as sulfhydryl is present, it reacts with H2S to generate a thiol group (-SH). It is believed that one molecule of H2S is separated from the two generated thiol groups and condensed (hereinafter also referred to as de-H2S condensation). A conceptual diagram is shown.

[0042] [Chemistry 1]

[0043]

[0044] Since compounds containing thiol groups react easily with each other, the formation of a sulfide solid electrolyte is also easier when a solid electrolyte raw material reacts with HS to produce thiol groups, compared to using only a solid electrolyte raw material without thiol groups. In compounds that react with HS contained in the solid electrolyte raw material, it is not necessary for all substituents that react with HS to become thiol groups. Even if some of them do, the activation energy for the formation of Li3PS4 can be reduced, thus it is believed that the above-mentioned heating temperature can be reduced.

[0045] The conceptual diagram shows a state where H2S reacts with one P(=S)-SP(=S), but it can also react simultaneously or at different times. The reaction of multiple P(=S)-SP(=S) with H2S generates mercapto groups, which reduces the activation energy for Li3PS4 formation and is therefore preferred. In this hypothesis (1), H2S functions as a catalyst.

[0046] In hypothesis (2), LiSH is generated in the same manner as in hypothesis (1). LiOH and Li2S are solid at room temperature, and granular substances are usually used as solid electrolyte materials. The particles of LiOH and Li2S react with H2S, and a part of the granules becomes LiSH, thereby obtaining a result that the specific surface area is increased compared to the particles of LiOH and Li2S. If the specific surface area becomes larger, the chance of collision with P2S5 is further increased. In addition, since Li2S becomes LiSH (1 molecule of Li2S becomes 2 molecules of LiSH), the number of molecules is also doubled, so the chance of collision with P2S5 is also doubled. It is believed that the reactivity is improved by their synergistic effect.

[0047] The hydrogen sulfide used in this embodiment can function as a solid electrolyte raw material for introducing sulfur atoms into the sulfide solid electrolyte, similar to the raw material components used to produce the sulfide solid electrolyte. It can also be said that its main function is to serve as a catalyst that reduces the activation energy during the production of the sulfide solid electrolyte. Furthermore, it is believed that the generation of the intermediate having a mercapto group and the decomposition of the intermediate by condensation due to H₂S removal (also referred to as mercapto group decomposition) as described above can produce a sulfide solid electrolyte even when the heating temperature is suppressed.

[0048] The method for producing a sulfide solid electrolyte according to a second aspect of the present embodiment is as follows: in the first aspect,

[0049] The heating (1) is carried out under a gas flow of hydrogen sulfide.

[0050] In the present embodiment, the method for supplying hydrogen sulfide is not particularly limited as long as heating is performed while hydrogen sulfide is in contact with the raw material-containing material. However, it is preferred to perform heating under a hydrogen sulfide gas flow because the supply amount of hydrogen sulfide can be easily adjusted by changing the flow rate or by changing the partial pressure of hydrogen sulfide when it is supplied as a mixture with other gases.

[0051] A third method for producing a sulfide solid electrolyte according to the present embodiment is, in the second method described above,

[0052] The method includes further heating (heating (2)) after stopping the flow of hydrogen sulfide, wherein the temperature (T2 (° C.)) of the heating (2) is 170° C. or less.

[0053] As in the second embodiment, when hydrogen sulfide is supplied by a hydrogen sulfide gas stream, its supply can be easily stopped. Further heating (2) is preferred because H2S removal condensation from two mercapto groups is performed to produce a sulfide solid electrolyte.

[0054] In the present embodiment, the "temperature (T2 (° C.))" of heating (2) refers to the highest temperature in heating (2).

[0055] It is believed that heating (1) mainly generates mercapto groups, and heating (2) mainly de-H2S condensation. It is believed that the method for producing a sulfide solid electrolyte of this embodiment can reduce the heating temperature required for production by generating mercapto groups. By performing heating (1) in this way, the heating temperature during production can be reduced, and further heating (2) is performed to consume the raw material mixture and / or intermediates, thereby improving the yield of the sulfide solid electrolyte, and therefore it is preferred. The raw material contents remaining in the sulfide solid electrolyte after production are the main cause of the reduction in the ionic conductivity of the sulfide solid electrolyte. By fully consuming the raw material contents, the ionic conductivity of the sulfide solid electrolyte is improved, and therefore it is preferred to perform heating (2). In the case of performing heating (1) alone, the production of the sulfide solid electrolyte is carried out by generating the intermediate having a mercapto group by heating (1) and decomposing the intermediate by de-H2S condensation (i.e., via the intermediate having a mercapto group). On the other hand, when heating (1) and heating (2) are performed, the intermediate having a mercapto group is generated by heating (1), and the intermediate is decomposed by heating (2) due to de-H2S condensation of the intermediate, thereby producing a sulfide solid electrolyte. Furthermore, as described above, by passing through the intermediate having a mercapto group, the sulfide solid electrolyte can be produced while suppressing the heating temperature.

[0056] A fourth method for producing a sulfide solid electrolyte according to the present embodiment is, in the third method described above,

[0057] The heating (2) is performed in an atmosphere of nitrogen or a rare gas, or under reduced pressure.

[0058] The heating (2) mentioned above mainly removes H2S and condenses it. It is preferably carried out in a nitrogen or rare gas atmosphere, rather than in a hydrogen sulfide atmosphere, or under reduced pressure. The reason for this is as follows: since the partial pressure of hydrogen sulfide in the atmosphere is reduced, the removal of H2S is facilitated, and the reaction equilibrium tilts toward the formation of a sulfide solid electrolyte.

[0059] A fifth method for producing a sulfide solid electrolyte according to the present embodiment is, in the third or fourth method,

[0060] The T1 and the T2 satisfy the relationship of T1≤T2≤170°C.

[0061] As described above, the maximum temperatures of each heating temperature in heating (1) and heating (2) are T1 and T2, and they are preferably both below 170°C. In order to obtain a sulfide solid electrolyte having a target crystal structure, it is preferred that T1 and T2 are both below 170°C.

[0062] T2 is preferably greater than T1, and more preferably higher than T1. This is because first, mercapto groups are generated to increase the mercapto group content of the intermediate, and then the temperature is raised to remove H2S condensation. This allows the heating temperature to be lowered during the production of the sulfide solid electrolyte.

[0063] A sixth method for producing a sulfide solid electrolyte according to the present embodiment is as follows: in the fifth method,

[0064] The temperature is increased from T1 to T2 under a gas flow of hydrogen sulfide.

[0065] When T2 is higher than T1, the temperature increase from T1 to T2 is preferably performed under a hydrogen sulfide gas flow because this further promotes the generation of mercapto groups during the temperature increase and suppresses side reactions such as decomposition of mercapto groups during the temperature increase.

[0066] Furthermore, it is preferable to carry out the treatment under a hydrogen sulfide gas flow because the supply amount of hydrogen sulfide can be easily adjusted.

[0067] A seventh method for producing a sulfide solid electrolyte according to the present embodiment is, in any one of the first to sixth methods,

[0068] The median diameter (D 50 ) is less than 15μm.

[0069] The reason is as follows: if the raw material used in this embodiment contains D 50 When the particle size is less than 15 μm, the reaction rates by heating (1) and heating (2) become faster, and thus a sulfide solid electrolyte can be produced at a low temperature and in a short time.

[0070] The eighth aspect of the present embodiment is a method for producing a sulfide solid electrolyte, in any one of the first to seventh aspects,

[0071] Further comprising crushing.

[0072] The details of the pulverization will be described later. The method for producing the sulfide solid electrolyte of this embodiment preferably further includes pulverizing the raw material content (solid electrolyte raw material), pulverizing the intermediate described later, or pulverizing after heating (2). This is because, by pulverizing the raw material content (solid electrolyte raw material) and / or pulverizing the intermediate described later, the reaction rate of heating (1) and / or heating (2) becomes faster, and by pulverizing, the raw material content becomes more easily in contact with H2S, thereby improving the reactivity and reducing the unreacted raw material content. If the content of unreacted raw materials is reduced, the ionic conductivity of the sulfide solid electrolyte is improved. In addition, when the solid electrolyte raw material and / or intermediate, especially lithium halide and Li3PS4, are heated, they are easily dispersed evenly, and the halogen atoms are more evenly distributed in the manufactured sulfide solid electrolyte, thereby improving the ionic conductivity, and thus the battery characteristics of the lithium ion battery using it are excellent.

[0073] A ninth aspect of the present embodiment is a method for producing a sulfide solid electrolyte, in any one of the first to eighth aspects,

[0074] The heating (1) is performed at least twice,

[0075] A tenth method for producing a sulfide solid electrolyte according to the present embodiment is, in the eighth or ninth method,

[0076] The heating (1) is performed at least twice, and the heating (1), the pulverization, and the heating (1) are performed in sequence.

[0077] By performing heating (1) at least twice, the generation of the intermediate can be further advanced, thereby improving the ionic conductivity of the resulting sulfide solid electrolyte. Furthermore, by combining heating (1) at least twice with pulverization, the miscibility of the intermediate is further improved, thereby enabling more efficient heating (1) and preferably heating (2). Therefore, not only can energy be further reduced and a sulfide solid electrolyte having a desired crystal structure be easily produced, but the ionic conductivity of the resulting sulfide solid electrolyte can also be further improved.

[0078] The eleventh aspect of the present embodiment is a method for producing a sulfide solid electrolyte, wherein, in any one of the eighth to tenth aspects,

[0079] The pulverization includes pulverizing the raw material contents.

[0080] The reason for this is as follows: by pulverizing the raw material content used in this embodiment, the reaction rates of heating (1) and heating (2) are accelerated as described above, and the ion conductivity of the sulfide solid electrolyte is also improved.

[0081] A twelfth aspect of the present embodiment is a method for producing a sulfide solid electrolyte, in any one of the first to eleventh aspects,

[0082] The raw material content is a mixture of solid electrolyte raw materials containing at least one selected from lithium atoms, sulfur atoms, and phosphorus atoms.

[0083] The reason for this is as follows: by making the raw material content used in this embodiment a mixture of solid electrolyte raw materials containing at least one selected from lithium atoms, sulfur atoms, and phosphorus atoms, it is easy to produce a sulfide solid electrolyte having a target crystal structure, and it is easy to produce a sulfide solid electrolyte having a crystal system with high ion conductivity.

[0084] The method for producing the sulfide solid electrolyte of the present embodiment will be described in more detail below based on the above-described embodiment.

[0085] [Method for producing sulfide solid electrolyte]

[0086] The method for producing a sulfide solid electrolyte according to the present embodiment includes heating a raw material-containing material while bringing hydrogen sulfide into contact with the material (heating (1)), wherein the temperature (T1 (°C)) of the heating (1) is 170°C or less.

[0087] Hereinafter, after explaining the production method, details of the raw material content, the sulfide solid electrolyte, and the like will be explained.

[0088] <Exposure to Hydrogen Sulfide>

[0089] The method for producing a sulfide solid electrolyte according to this embodiment requires contacting hydrogen sulfide with the raw material content described below while performing heating, as described below. By contacting and heating the raw material content with hydrogen sulfide, the solid electrolyte raw material contained in the raw material content becomes an intermediate having a thiol group within its structure, as described above. The generation of this intermediate reduces the activation energy for producing the sulfide solid electrolyte, making high-temperature heating unnecessary, which is preferable.

[0090] As a method of reducing the heating temperature during manufacture, there is a known method of using a complexing agent (e.g., WO2020 / 105737 pamphlet). This method manufactures a solid electrolyte via a complex by treating the raw material containing substance together with the complexing agent. Therefore, high-temperature heating is not required, and it can be manufactured in a short time using a simple manufacturing device, so it can be said to be an excellent manufacturing method. However, on the other hand, since the complexing agent needs to be removed from the complex, a process for removing the complexing agent from the complex is required. In contrast, the method for manufacturing the sulfide solid electrolyte of the present embodiment does not require the use of a complexing agent, so there is no need for its removal process. Hydrogen sulfide is a gas at room temperature, so it can be easily removed. In this respect, it can be said that the method for manufacturing the sulfide solid electrolyte of the present embodiment is an excellent manufacturing method.

[0091] The method of contacting the raw material-containing material with hydrogen sulfide is not particularly limited, but the atmosphere during heating is preferably an atmosphere containing hydrogen sulfide or a hydrogen sulfide atmosphere. It is also preferred to heat the raw material-containing material together with a solvent in which hydrogen sulfide is dissolved, as described below.

[0092] During the heating (1) and temperature increase described below, hydrogen sulfide reacts with the raw material contents and is consumed over time, so it is preferably added as needed. Therefore, the heating (1) and temperature increase may be performed intermittently, where hydrogen sulfide is introduced into a closed apparatus and added each time the internal pressure decreases. However, heating (1), where the consumption of hydrogen sulfide is high, is preferably performed under a hydrogen sulfide gas flow.

[0093] Here, heating while in contact is performed in order to avoid the consumption of hydrogen sulfide and the reduction of the amount of hydrogen sulfide in contact with the raw material content, thereby heating in a non-contact state. This is because if heating is performed in a non-contact state, it is conceivable that hydrogen sulfide will be separated from the intermediate, resulting in a state where a sufficient amount of mercapto groups are not present in the intermediate. Therefore, before heating (2) described later, it is preferable to be able to supply a sufficient amount of hydrogen sulfide so as to be placed under a hydrogen sulfide gas flow. In addition, when pulverizing the intermediate, it is preferable to carry out the pulverization in a hydrogen sulfide gas flow until it cools to near room temperature (the definition of "room temperature" will be described later).

[0094] In this disclosure, "airflow" refers to the supply of hydrogen sulfide from outside the heating apparatus and its subsequent discharge to the outside of the apparatus, preferably so that the discharged hydrogen sulfide is recirculated and supplied again. Furthermore, to prevent the discharged hydrogen sulfide from being released into the environment, a hydrogen sulfide capture device is preferably provided as needed.

[0095] The flow rate of the gas stream can be appropriately selected depending on the size of the reaction apparatus, the amount of the raw material content used, the amount of the solvent used, and the like. It is preferably adjusted so that the formation of the intermediate takes precedence over the decomposition of the intermediate during heating (1) and temperature increase. The flow rate is not particularly limited, but is preferably from 0.1 mL / min to 500 mL / min, and more preferably from 0.3 mL / min to 400 mL / min, relative to 1 g of the raw material content.

[0096] <Heating>

[0097] The method for producing the sulfide solid electrolyte of the present embodiment needs to include heating.

[0098] The heating needs to include heating (1) of heating while bringing hydrogen sulfide into contact with the raw material-containing material, and preferably includes further heating (heating (2)) after stopping the flow of hydrogen sulfide.

[0099] The following describes heating (1) and heating (2) in more detail.

[0100] (Heating (1))

[0101] In the heating (1), heating is performed while hydrogen sulfide is brought into contact with the raw material content, and the temperature (T1 (°C)) of the heating (1) needs to be 170°C or less. The heating (1) can be performed once at a heating temperature of 170°C or less while in contact with hydrogen sulfide, or it can be heated at least twice. In the case of performing heating (1) at least twice, the heating can be performed at least twice at one heating temperature, or it can be heated at two or more heating temperatures. From the viewpoint of further promoting the generation of intermediates and improving the ionic conductivity of the obtained sulfide solid electrolyte, the heating (1) is preferably performed at least twice. As a result, it is also possible to more efficiently and easily produce a sulfide solid electrolyte having a desired crystal structure while reducing energy.

[0102] During heating (1), the temperature does not need to be always T1 (°C), and heating is usually started from room temperature (in this specification, room temperature refers to a temperature without external heating or cooling. It is usually a temperature around 25°C.) and controlled to a temperature lower than T1 (°C).

[0103] The heating method is not particularly limited and can be appropriately selected according to the size and shape of the reaction apparatus and the heating temperature. For example, it can be appropriately selected from a hot water bath, an oil bath, a mantle heater, a heating jacket, and the like.

[0104] (Temperature of heating (1) (T1 (°C)))

[0105] As described above, heating (1) is heating for producing the intermediate. If T1 (°C) is a temperature higher than 170°C, the decomposition of the formed thiol group takes precedence over the formation of the thiol group. In order to sufficiently generate thiol groups and obtain more intermediates, T1 (°C) needs to be 170°C or lower. T1 (°C) is preferably 150°C or lower, more preferably 120°C or lower, and particularly, in order to promote the consumption of the raw material content, it is further preferably 100°C or lower. On the other hand, in order to increase the reaction rate of the formation of the thiol group, it is preferably room temperature or higher, more preferably 30°C or higher, further preferably 35°C or higher, and further preferably 40°C or higher. As a combination of the upper limit and the lower limit, it is preferably room temperature or higher and 170°C or lower, more preferably 30°C or higher and 150°C or lower, further preferably 35°C or higher and 120°C or lower, and further preferably 40°C or higher and 100°C or lower.

[0106] In this disclosure, the heating temperatures (T1 (°C) and T2 (°C)) refer to the temperatures of the heated object. When a solvent is used, the heating temperature can be considered the temperature of the solvent. When a powder is heated, the heating temperature can be considered the temperature measured by placing a thermocouple or the like in contact with the powder. When the reactor is heated in an oil bath or the like, the heating temperature can be considered the temperature of the oil bath.

[0107] When heating (1) is performed at least twice, the first heating temperature T 1A (°C) (hereinafter, the first heating temperature in the case of heating (1) at least twice may be referred to as "T 1A "T 1A ” is the temperature included in the heating temperature “T1” of heating (1), and the matters applicable to “T1” also apply to “T 1A ".), preferably above room temperature, more preferably above 30°C, more preferably above 40°C, further preferably above 45°C, and the upper limit is preferably below 80°C, more preferably below 70°C, further preferably below 60°C, further preferably below 55°C.

[0108] The second and subsequent heating temperatures can be the same as the first heating temperature T 1A (℃) is the same, it can also be higher than the heating temperature T 1A (℃), preferably heating temperature T 1A (°C) or above. As a specific temperature range, for example, it is preferably higher than 80°C, more preferably higher than 85°C, further preferably higher than 90°C, and further preferably higher than 95°C. As an upper limit, it is preferably lower than 110°C, more preferably lower than 108°C, and further preferably lower than 105°C. The second heating temperature T when the heating is performed twice 1B(°C) (Hereinafter, the second heating temperature in the case where heating (1) is performed at least twice may be referred to as "T 1B "T 1B ” is also related to the above “T 1A ” Similarly, the temperature included in the heating temperature “T1” of heating (1) is the temperature, and the matters applicable to “T1” also apply to “T 1B ".) It is sufficient to select from the above-mentioned temperature range. In addition, when it is carried out three or more times, it is sufficient to select multiple heating temperatures from the above-mentioned temperature range. The heating temperatures can be selected in a manner that the heating temperatures become higher or lower, and it is preferred to select in a manner that the heating temperatures become higher.

[0109] When heating (1) is performed at least twice, heating (1) can be performed at least twice before the pulverization described later, heating (1) can be performed after the pulverization described later, or heating (1) can be performed at least twice after the pulverization described later. Among them, as heating (1), it is preferred to perform heating (1) after the pulverization described later, that is, heating of heating (1), pulverization, and heating (1) are performed in sequence. In this case, for example, heating (1) can be performed once or multiple times before pulverization, and heating (1) can be performed once or multiple times after pulverization. It is preferred to perform the first heating of heating (1) before pulverization, pulverization, and heating of the second and subsequent heating of heating (1) in sequence, and more preferably, the first heating of heating (1) before pulverization, pulverization, and heating of the second and subsequent heating of heating (1) in sequence. In this way, by combining heating (1) and pulverization, heating can be performed more efficiently. Therefore, in addition to further reducing energy and making it easier to produce a sulfide solid electrolyte having a desired crystal structure, the miscibility of the intermediate is further improved, and thus the ionic conductivity of the obtained sulfide solid electrolyte can be further improved.

[0110] It is also possible to further perform heating (2) after the second or subsequent heating of heating (1). Performing heating (1) and then heating (2) after pulverization is effective in improving the ionic conductivity of the resulting sulfide solid electrolyte.

[0111] In the case of heating (1) after pulverization, the first heating temperature T 1A (℃) from the above heating temperature T 1A (°C) can be appropriately selected from the preferred temperature range. In addition, as the second and subsequent heating temperatures, the first heating temperature T 1A (℃) can be appropriately selected from the preferred temperature range, and the second heating temperature T 1B (°C) is preferably set to the same temperature as the heating temperature T 1A (℃)Same temperature.

[0112] In addition, in the case of performing heating (1) three or more times, the heating temperature after the third time may be appropriately selected from the preferred temperature range of the heating temperature after the second time. Further, the heating temperature after the third time is also a temperature included in the heating temperature “T1” of heating (1), and matters applicable to “T1” are also applicable to the heating temperature after the third time. 1A and T 1B Similarly, it is a temperature included in the heating temperature “T1” of heating (1), and matters applicable to “T1” are also applicable to the heating temperature after the third time.

[0113] (Heating (2))

[0114] The method for manufacturing a sulfide solid electrolyte according to the present embodiment preferably includes further performing heating (heating (2)) after stopping the gas flow of hydrogen sulfide, and the temperature (T2 (°C)) of the heating (2) is 170 °C or lower.

[0115] This is because by performing heating (2), as described above, H2S is detached from the intermediate, and the de-H2S condensation further proceeds.

[0116] (Temperature (T2 (°C)) of heating (2))

[0117] T2 (°C) is preferably 170 °C or lower, more preferably 160 °C or lower, further preferably 150 °C or lower, still more preferably 140 °C or lower, and particularly preferably 135 °C or lower. In addition, in order to shorten the heating time, it is preferably 50 °C or higher, more preferably 70 °C or higher, further preferably 80 °C or higher, still more preferably 90 °C or higher, and particularly preferably 100 °C or higher. As a combination of the upper limit value and the lower limit value, it is preferably 50 °C or higher and 170 °C or lower, more preferably 70 °C or higher and 160 °C or lower, further preferably 80 °C or higher and 150 °C or lower, still more preferably 90 °C or higher and 140 °C or lower, and particularly preferably 100 °C or higher and 135 °C or lower.

[0118] As described above, the de-H2S condensation preferentially proceeds at a temperature higher than the generation and decomposition of mercapto groups. In addition, in order to obtain the target crystal structure, T1 and T2 are preferably 170 °C or lower. Therefore, it is preferred that the T1 and the T2 satisfy the relationship of T1 ≤ T2 ≤ 170 °C. In this specification, “decomposition of mercapto groups” means returning to the state before the generation of mercapto groups, etc.

[0119] The temperatures of T1 and T2 may be equal, may be T1 < T2, and are preferably T1 < T2.

[0120] When performing heating (1) once, the temperature difference (T2 - T1) between T2 and T1 can be 0 °C, but is preferably 10 °C or more and 150 °C or less, more preferably 20 °C or more and 130 °C or less, further preferably 30 °C or more and 110 °C or less, still further preferably 40 °C or more and 100 °C or less, and particularly preferably 50 °C or more and 90 °C or less.

[0121] When heating (1) is performed at least in two steps, the heating temperature T of the first step 1A is preferably selected from the temperature range of the above-mentioned temperature difference (T2 - T1) between T2 and T1. In addition, when heating (1) is performed in two steps, the heating temperature T of the second stage 1B is preferably the heating temperature T of the first step as described above 1A or higher, and more preferably set to a temperature higher than T 1A . In addition, based on the relationship between the heating temperature of the above-mentioned heating (1) and the heating temperature of heating (2), the heating temperature T of the second time 1B is preferably equal to or lower than the heating temperature T2 of heating (2) (T 1B ≤ T2), and more preferably less than T2 (T 1B < T2). In addition, when heating (1) is performed three or more times, the heating temperature (T 1C ) after the third time is preferably equal to or higher than the heating temperature (T 1A ) of the first time and the heating temperature (T 1B ) of the second time. As an upper limit, it is preferably equal to or lower than the heating temperature T2 of heating (2) (T 1C ≤ T2), and more preferably less than T2 (T 1C < T2).

[0122] In addition, when heating (1) is performed at least in two steps, as the temperature difference (T2 - T1) between the heating temperature T1 of heating (1) (set as the highest heating temperature in heating (1), preferably the above-mentioned T 1B or T 1C ) and the heating temperature T2 of heating (2), it is preferably 3 °C or more and 30 °C or less, more preferably 5 °C or more and 15 °C or less, and still more preferably 7.5 °C or more and 12.5 °C or less.

[0123] The heating (2) is preferably performed after stopping the gas flow of hydrogen sulfide. Thus, as described above, the progress of de-H2S condensation is promoted. The heating (2) is preferably performed in an atmosphere of nitrogen or noble gas or under reduced pressure to further promote the progress of de-H2S condensation. Therefore, from the viewpoint of ease of implementation, etc., it is more preferably in a nitrogen atmosphere including under a nitrogen gas flow.

[0124] <Temperature increase>

[0125] As described above, it is preferable that T1 < T2. In this case, the temperature increase from T1 to T2 can be a direct temperature increase, or can be a temperature increase after temporarily cooling from T1 to room temperature, or can be cooled after increasing the temperature from T1 above T2 to set it to T2. Even when the temperature is increased above T2, it is preferably not more than 170°C. In addition, when increasing the temperature from T1 to T2, it is preferably carried out under a hydrogen sulfide gas flow, and the hydrogen sulfide gas flow can be carried out under the same conditions as the hydrogen sulfide gas flow preferably carried out during the above-mentioned heating (1).

[0126] The heating rate can be appropriately selected according to the shape, size, heating method, usage amount of the raw material inclusion, T1, T2, etc. of the device used in the present embodiment, and is preferably 0.01°C / min or more and 100°C / min or less, more preferably 0.1°C / min or more and 50°C / min or less.

[0127] The heating rate can be calculated by the temperature difference between T2 and T1 during heating (assuming room temperature when temporarily set to room temperature) and the time (t (minutes)) required from heating (1) to setting to heating (2) ((T2 - T1) / t).

[0128] By increasing the temperature from T1°C to T2°C under a hydrogen sulfide gas flow, the decomposition of the mercapto group of the intermediate can be suppressed, so it is preferred.

[0129] In addition, as described above, when heating (1) is carried out at least in two steps, the heating temperature T in the second heating 1B is higher than the heating temperature T in the first heating 1A and the heating temperature T in the heating after the third time 1C is higher than the heating temperature T in the first heating 1A is higher, a temperature increase is also carried out. In this case, the temperature increase is also preferably carried out under a hydrogen sulfide gas flow in the same manner as the temperature increase from T1 to T2 above. In addition, the heating rate is also the same as the temperature increase from T1 to T2 above.

[0130] <Comminution>

[0131] The method for manufacturing a sulfide solid electrolyte of the present embodiment preferably further includes comminution.

[0132] The pulverization preferably includes at least one of pulverizing the raw material content (solid electrolyte raw material), pulverizing the intermediate described later, or pulverizing after heating (2). As the object of pulverization, when only heating (1) is performed, solid electrolyte raw materials and sulfide solid electrolytes can be exemplified. In addition, when heating (1) and heating (2) are performed, solid electrolyte raw materials, intermediates, and sulfide solid electrolytes can be exemplified. By including pulverizing the raw material content (solid electrolyte raw material) and / or pulverizing the intermediate described later, the reaction rate of heating (1) and / or heating (2) becomes faster. In addition, by pulverizing, the raw material content becomes more easily in contact with H2S, thereby improving the reactivity and reducing the unreacted raw material content, which is preferred. From this point of view, it is preferred to pulverize the solid electrolyte raw material. In addition, when the intermediate is pulverized, particles are formed with the parts that are not in direct contact with hydrogen sulfide as the surface, causing these parts to contact with hydrogen sulfide. As a result, if the generation of mercapto groups further proceeds and the content of unreacted raw materials is reduced, the ionic conductivity of the sulfide solid electrolyte is improved, which is preferred.

[0133] When solid electrolyte raw materials and / or intermediates, particularly lithium halides and Li3PS4, are heated, they are more uniformly dispersed, resulting in a more uniform distribution of halogen atoms in the produced sulfide solid electrolyte. This improves ionic conductivity, and lithium ion batteries using the sulfide solid electrolyte exhibit excellent battery characteristics, which is preferred. The pulverization preferably involves pulverizing the raw material contents in order to reduce the amount of residual raw material components in the sulfide solid electrolyte, increase the reaction rate, and shorten the production time of the sulfide solid electrolyte.

[0134] When the intermediate is pulverized, it can be performed before, after, or during the above-mentioned heating. However, it is preferred that after heating (1), the intermediate is cooled to near room temperature, pulverized in an atmosphere of hydrogen sulfide, nitrogen, or a rare gas, and then heated and heated (2). In addition, when heating (1) is performed at least twice, after heating (1), the intermediate is cooled to near room temperature and pulverized in an atmosphere of hydrogen sulfide, nitrogen, or a rare gas, it is preferred that the intermediate is heated and heated (1) is performed thereafter. It is also preferred that the intermediate is heated and heated (1) is performed thereafter and then heated (2). By performing heating (1) and / or heating (2) after pulverization, it is possible to further reduce energy while facilitating the production of a sulfide solid electrolyte having a desired crystal structure, and it is also possible to further improve the ionic conductivity of the obtained sulfide solid electrolyte. The heating temperatures in heating (1) and (2) are as described above.

[0135] When the heating (1) is performed at least twice and pulverization is performed between the multiple heating steps of the heating (1), it is preferred to cool to near room temperature before pulverization, as described above. The cooling is preferably performed under a stream of hydrogen sulfide, similar to the heating. The cooling rate to room temperature may be selected from the numerical ranges described above as the heating rate.

[0136] By the pulverization, it is preferred that the median diameter (D 50 ) is less than 15 μm, more preferably less than 12 μm, and further preferably less than 10 μm.

[0137] Median diameter (D 50 ) can be measured, for example, using the method described in the examples.

[0138] The pulverization method is not particularly limited as long as the raw material content (solid electrolyte raw material), the intermediate, and the sulfide solid electrolyte powder can be pulverized, and any method commonly used in the production of sulfide solid electrolytes may be used.

[0139] By adjusting the peripheral speed of the pulverizer's rotor, it is possible to adjust the crushing (micronization) and granulation (grain growth) of the powder. In other words, in addition to mixing, the median diameter can be reduced by crushing or increased by granulation, making it easy to freely adjust the powder's morphology.

[0140] As a more specific example of a pulverizer, a media pulverizer can be used. Media pulverizers are broadly classified into container-driven pulverizers and media-stirring pulverizers. When the powder is a slurry containing a solvent, a wet pulverizer that can handle wet pulverization is preferred among media pulverizers.

[0141] Examples of container-driven pulverizers include stirring tanks, pulverizing tanks, or combinations thereof of ball mills and beads mills. Various types of ball mills and beads mills can be employed, including rotary, rolling, vibrating, and planetary types.

[0142] In addition, as media stirring type pulverizers, there are: impact type pulverizers such as cutter mills, hammer mills, and pin mills; tower type pulverizers such as tower mills; stirring trough type pulverizers such as attritors, wet sand mills (aquamizers), and sand mills; flow trough type pulverizers such as viscose mills and coarse crushers; flow tube type pulverizers; ring type pulverizers such as combined ball mills; continuous dynamic type pulverizers; and other various pulverizers.

[0143] When mechanically processing powders to form a slurry, container-driven pulverizers are preferred, with bead mills and ball mills being particularly preferred, as they facilitate adjustment of the desired morphology. Container-driven pulverizers such as bead mills and ball mills include a rotating body capable of stirring the powder, along with a container such as a stirring tank or a grinding tank for storing the powder. Therefore, as described above, the powder morphology can be easily adjusted by adjusting the circumferential speed of the rotating body.

[0144] Bead mills and ball mills can adjust the shape by adjusting the particle size, material, and amount of beads and balls used, allowing for finer shape adjustment and even unprecedented shape adjustment. For example, centrifugal bead mills can also be used, which can use extremely fine particles (approximately 0.015 to 1 mm in diameter), also known as microbeads (e.g., Ultra Apex Mill (UAM)).

[0145] The particle size of the media used in a bead mill, a ball mill, etc. may be appropriately determined in consideration of the desired form and the type and scale of the apparatus used, but is usually preferably 0.01 mm or more, more preferably 0.015 mm or more, further preferably 0.02 mm or more, and even more preferably 0.04 mm or more. The upper limit is preferably 10 mm or less, and more preferably 5 mm or less.

[0146] Examples of the material of the medium include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconium oxide and silicon nitride; and minerals such as agate.

[0147] The treatment time of the mechanical treatment and the peripheral speed of the rotating body during the mechanical treatment (rotation speed in devices such as bead mills and ball mills) can be appropriately determined in consideration of the desired form and the type and scale of the device used.

[0148] <Ingredients>

[0149] The raw material used in this embodiment preferably contains lithium atoms, sulfur atoms, and phosphorus atoms, and more preferably is a mixture of solid electrolyte raw materials containing at least one selected from lithium atoms, sulfur atoms, and phosphorus atoms. More specifically, it is a material containing the following substances (hereinafter also referred to as "solid electrolyte raw materials"): containing one or more substances selected from the group consisting of these atoms. The raw material used in this embodiment preferably contains two or more solid electrolyte raw materials.

[0150] Furthermore, in order to form a mercapto group with hydrogen sulfide during heating (1), the solid electrolyte raw material preferably contains at least one compound that reacts with H 2 S as described above.

[0151] Furthermore, from the viewpoint of improving ion conductivity, the raw material-containing substance used in the present embodiment preferably further contains a halogen atom.

[0152] Representative examples of the solid electrolyte raw materials contained in the raw material content include: lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus 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, P2 I4); thiophosphoryl halides such as thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and other raw materials composed of at least two atoms selected from the above four atoms; halogen monomers such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).

[0153] As substances other than the above-mentioned substances that can be used as solid electrolyte raw materials, for example, solid electrolyte raw materials containing at least one atom selected from the above-mentioned four atoms and atoms other than the four atoms, more specifically, there can be mentioned: 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; phosphoric acid compounds such as sodium phosphate and lithium phosphate; alkali metal halides 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; halogenated phosphorus oxides such as phosphorus oxychloride (POCl3) and phosphorus oxybromide (POBr3); etc.

[0154] Among the above, lithium sulfide is preferred as a solid electrolyte raw material containing lithium atoms, sulfur atoms, and phosphorus atoms; phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5) are preferred, and phosphorus pentasulfide is preferred among the phosphorus sulfides.

[0155] When oxygen atoms are introduced into the solid electrolyte, lithium oxide, lithium hydroxide, and phosphoric acid compounds such as lithium phosphate are preferred.

[0156] As the halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are preferred, and a chlorine atom, a bromine atom, and an iodine atom are more preferred. As the solid electrolyte raw material, a solid electrolyte raw material containing these halogen atoms can be exemplified. As the halogen atom, these halogen atoms can be used alone or in combination, and a combination of multiple types is preferred.

[0157] As the solid electrolyte raw material containing a halogen atom, for example, halogen monomers 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 can be preferably exemplified. As the halogen monomer, chlorine (Cl2), bromine (Br2), and iodine (I2) are more preferred, and as the lithium halide, lithium chloride, lithium bromide, and lithium iodide are more preferred.

[0158] As combinations of solid electrolyte raw materials, for example, preferably there can be mentioned a combination of lithium sulfide and phosphorus pentasulfide, a combination of lithium sulfide, phosphorus pentasulfide and a halogen monomer, and a combination of lithium sulfide, phosphorus pentasulfide and a lithium halide. As the halogen monomer, chlorine, bromine and iodine are preferred, and as the lithium halide, lithium chloride, lithium bromide and lithium iodide are preferred.

[0159] In this embodiment, Li3PS4 containing a PS4 structure can also be used as part of the raw material. Specifically, Li3PS4 and the like are first produced and prepared, and then used as the raw material.

[0160] The content of Li3PS4 relative to the total amount of the raw materials is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and further preferably 70 to 80 mol%.

[0161] In addition, when Li3PS4 and a halogen monomer are used, the content of the halogen monomer relative to Li3PS4 is preferably 1 to 50 mol%, more preferably 10 to 40 mol%, further preferably 20 to 30 mol%, and further preferably 22 to 28 mol%.

[0162] The lithium sulfide used in this embodiment is preferably in the form of particles.

[0163] The median diameter of lithium sulfide particles (D 50 ) is preferably 0.1 μm or more and less than 15 μm, more preferably 0.5 μm or more and 13 μm or less, further preferably 1 μm or more and 12 μm or less, further preferably 1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, further preferably 1 μm or more and 3 μm or less. In this specification, the median diameter (D 50 ) is the particle size when the particle size distribution cumulative curve is drawn, starting from the smallest particle size and accumulating to 50% (volume basis) of the total. The volume distribution is, for example, the average particle size that can be measured using a laser diffraction / scattering particle size distribution measuring device. In addition, the solid raw material among the raw materials exemplified as the solid electrolyte raw material preferably has an average particle size of the same magnitude as that of the lithium sulfide particles, that is, the median diameter (D) of the raw material content. 50) is preferably less than 15 μm, more preferably less than 13 μm, further preferably less than 12 μm, further preferably less than 10 μm, more especially preferably less than 5 μm, and further especially preferably less than 3 μm. As a combination of the upper limit and the lower limit, it is preferably greater than 0.1 μm and less than 15 μm, more preferably greater than 0.5 μm and less than 13 μm, further preferably greater than 1 μm and less than 12 μm, further preferably greater than 1 μm and less than 10 μm, more especially preferably greater than 1 μm and less than 5 μm, and further especially preferably greater than 1 μm and less than 3 μm. In the manufacturing method of this embodiment, as the raw material content (the solid electrolyte raw material contained therein), a substance that initially has the above-mentioned median diameter can be used, and a substance that has the above-mentioned median diameter by pulverizing as described above can also be used.

[0164] When lithium sulfide, phosphorus pentasulfide, and lithium halide are used as solid electrolyte raw materials, the ratio of lithium sulfide to the total of lithium sulfide and phosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, further preferably 70 mol% or more, and further preferably 74 mol% or more, from the viewpoint of obtaining higher chemical stability and higher ion conductivity. The upper limit is preferably 85 mol% or less, more preferably 83 mol% or less, and further preferably 80 mol% or less.

[0165] When lithium sulfide, phosphorus pentasulfide, lithium halide, and other solid electrolyte raw materials used as needed, the content of lithium sulfide and phosphorus pentasulfide relative to the total of these is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more. The upper limit is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and even more preferably 80 mol% or less.

[0166] When lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 mol% or more, more preferably 20 mol% or more, further preferably 35 mol% or more, further preferably 45 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 90 mol% or less, further preferably 75 mol% or less, further preferably 60 mol% or less.

[0167] In addition, when lithium bromide and lithium chloride are used in combination as the lithium halide, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 mol% or more, more preferably 15 mol% or more, further preferably 25 mol% or more, and further preferably 35 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 75 mol% or less, further preferably 60 mol% or less, and further preferably 45 mol% or less.

[0168] When a halogen monomer is used as a raw material and lithium sulfide and phosphorus pentasulfide are used, the ratio of the number of moles of lithium sulfide obtained by removing the same number of moles of lithium sulfide as the number of moles of the halogen monomer to the total number of moles of lithium sulfide and phosphorus pentasulfide obtained by removing the same number of moles of lithium sulfide as the number of moles of the halogen monomer is preferably in the range of 60 to 90%, more preferably in the range of 65 to 85%, even more preferably in the range of 68 to 82%, even more preferably in the range of 72 to 78%, and particularly preferably in the range of 73 to 77%. These ratios result in higher ionic conductivity.

[0169] Furthermore, from the same viewpoint, when lithium sulfide, phosphorus pentasulfide, and a halogen monomer are used, the content of the halogen monomer relative to the total amount of lithium sulfide, phosphorus pentasulfide, and the halogen monomer is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, further preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0170] When lithium sulfide, phosphorus pentasulfide, a halogen monomer and a lithium halide are used, the content of the halogen monomer relative to the total amount of lithium sulfide, phosphorus pentasulfide, the halogen monomer and the lithium halide (α mol%) and the content of the lithium halide relative to the total amount of these (β mol%) preferably satisfy the following formula (2), more preferably satisfy the following formula (3), further preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5).

[0171] 2≤2α+β≤100…(2)

[0172] 4≤2α+β≤80…(3)

[0173] 6≤2α+β≤50…(4)

[0174] 6≤2α+β≤30…(5)

[0175] When two halogens are used as monomers, if the number of moles of one halogen atom in the substance is set to A1 and the number of moles of the other halogen atom in the substance is set to A2, then A1:A2 is preferably 1:99 to 99:1, more preferably 10:90 to 90:10, further preferably 20:80 to 80:20, and further preferably 30:70 to 70:30.

[0176] When two halogen monomers are used and the two halogen monomers are bromine and iodine, if the number of moles of bromine is set to A1 and the number of moles of iodine is set to A2, then A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, further preferably 35:65 to 80:20, and further preferably 45:55 to 70:30.

[0177] Furthermore, when the two halogen monomers are bromine and chlorine, if the number of moles of bromine is set to B1 and the number of moles of chlorine is set to B2, then B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, further preferably 25:75 to 60:40, and further preferably 35:45 to 65:55.

[0178] (Intermediate)

[0179] When the heating (1) and the heating (2) are used, the intermediate is produced by the heating (1) and contains a compound having a mercapto group in its structure. The chemical composition of the intermediate depends on the content of the raw materials used.

[0180] When heating (1) is performed only once, the sulfide solid electrolyte is obtained through an intermediate during heating (1), and therefore, in principle, it is not separated as an intermediate. In addition, when heating (1) is performed at least twice, the intermediate is generated by the first heating, but further intermediates are generated by the second heating.

[0181] <Sulfide Solid Electrolyte>

[0182] The sulfide solid electrolyte produced in this embodiment is solid, preferably in granular form. The sulfide solid electrolyte obtained by the production method of this embodiment includes both a crystalline sulfide solid electrolyte having a crystal structure and an amorphous sulfide solid electrolyte. In this specification, "crystalline sulfide solid electrolyte" refers to a sulfide solid electrolyte in which peaks derived from the sulfide solid electrolyte are observed in the X-ray diffraction pattern during X-ray diffraction measurement, regardless of whether peaks derived from the raw materials of the sulfide solid electrolyte are present. In other words, the crystalline sulfide solid electrolyte contains a crystal structure derived from the sulfide solid electrolyte, and may contain a crystal structure derived from the sulfide solid electrolyte in part or entirely. Furthermore, the crystalline sulfide solid electrolyte may also contain an amorphous sulfide solid electrolyte in part, as long as it has the above-mentioned X-ray diffraction pattern. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous sulfide solid electrolyte to a temperature above the crystallization temperature.

[0183] In this specification, the term "amorphous sulfide solid electrolyte" means that the X-ray diffraction pattern is a halo pattern in which substantially no peaks other than peaks derived from the material are observed in X-ray diffraction measurement, regardless of the presence or absence of peaks derived from the raw materials of the sulfide solid electrolyte.

[0184] In addition, the content of lithium atoms, phosphorus atoms, and sulfur atoms in the sulfide solid electrolyte can be determined by measurement based on an inductively coupled plasma (ICP) emission spectrometer, and the content of organic groups can be determined by focusing on the characteristic functional groups of the organic groups and appropriately combining Fourier transform infrared spectrophotometry (FT-IR), solid-state nuclear magnetic resonance (NMR) spectroscopy, gas chromatography, gas chromatography-mass spectrometry (GC-Mass), etc.

[0185] (Amorphous sulfide solid electrolyte)

[0186] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment preferably contains lithium atoms, sulfur atoms, phosphorus atoms and, if necessary, halogen atoms. Representative amorphous sulfide solid electrolytes include, for example, sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide and lithium halide, such as Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and sulfide solid electrolytes such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI, which also contain other atoms such as oxygen atoms and silicon atoms. From the perspective of obtaining higher ionic conductivity, amorphous 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.

[0187] The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed by, for example, an ICP emission spectrometer.

[0188] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.6, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.08 to 0.4. In addition, when bromine and iodine are used in combination as halogen atoms, the blending ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine and iodine is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.02-0.25:0.02-0.25, more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.03-0.2:0.03-0.2, and further preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms and halogen atoms within the above-mentioned range, a solid electrolyte with higher ionic conductivity such as the type II crystal structure of the sulfide crystalline lithium superion conductor region and the argyrodite-type crystal structure described later can be easily obtained.

[0189] (Crystalline sulfide solid electrolyte)

[0190] The crystalline sulfide solid electrolyte obtained by the manufacturing method of the present embodiment may be a so-called glass-ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher. As its crystal structure, examples include a Li3PS4 crystal structure, a Li4P2S6 crystal structure, a Li7PS6 crystal structure, a Li7P3S 11 crystal structure, a crystal structure having peaks near 2θ = 20.2° and 23.6° (for example, Japanese Patent Laid-Open No. 2013-16423), etc.

[0191] As the crystalline sulfide solid electrolyte containing a halogen atom, a crystalline sulfide solid electrolyte having the following crystal structure can be preferably exemplified: having the structural framework of Li7PS6 described above, and a thiogermanate crystal structure in which a part of P is replaced by Si.

[0192] As the compositional formula of the thiogermanate crystal structure, for example, it can be exemplified by the compositional formula Li 7-x P 1-y Si y S6 and Li 7+x P 1- y Si y S6 (x is -0.6 to 0.6, y is 0.1 to 0.6). The thiogermanate crystal structure represented by this compositional formula is cubic or orthorhombic, preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0° and 52.0°.

[0193] As the compositional formula of the thiogermanate crystal structure, it can also be exemplified by the compositional formula Li 7-x-2y PS 6-x-y Cl x (0.8 ≤ x ≤ 1.7, 0 < y ≤ -0.25x + 0.5). The thiogermanate crystal structure represented by this compositional formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0° and 52.0°.

[0194] In addition, as the compositional formula of the thiogermanate crystal structure, it can also be exemplified by the compositional formula Li 7-x PS 6-x Ha x(Ha is Cl or Br, and x is preferably 0.2 to 1.8.) The argyrodite-type crystal structure represented by this composition formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, has peaks primarily appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0195] In addition, these peak positions can fluctuate within a range of ±0.5°.

[0196] Another example is Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148 (7) A742-746 (2001)), and Li 4-x Ge 1-x P x S4 type thio-LISICON Region II type crystal structure (see Solid State Ionics, 177 (2006), 2721-2725). From the perspective of obtaining higher ionic conductivity, the crystal structure of the crystalline sulfide solid electrolyte obtained by the method for producing the sulfide solid electrolyte of this embodiment is preferably a thio-LISICON Region II type crystal structure among the above. Here, "thio-LISICON Region II type crystal structure" means Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type crystal structure, and Li 4-x Ge 1-x P x Any crystal structure similar to the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type. Here, the above-mentioned "Li 4-x Ge 1-x P xThe expression of the crystal structure of the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type refers to the crystal structure found in the above-mentioned literature as a crystal structure composed of Li, Ge, P and S atoms. The sulfide solid electrolyte obtained by the manufacturing method of this embodiment preferably contains lithium atoms, phosphorus atoms, sulfur atoms and halogen atoms, and therefore may not be included in the "Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type "Li 4-x Ge 1-x P x S4". However, in the case of having the same diffraction peak as the above-mentioned "sulfide crystalline lithium superion conductor region type II crystal structure" (including the above-mentioned "similar crystal structure"), it can be said that the sulfide solid electrolyte obtained by the production method of this embodiment has a sulfide crystalline lithium superion conductor region type II crystal structure preferably composed of lithium atoms, phosphorus atoms, sulfur atoms and halogen atoms. The same applies to the above-mentioned argyrodite-type crystal structure.

[0197] The crystalline sulfide solid electrolyte obtained by the production method of this embodiment may contain the aforementioned crystalline lithium sulfide superion conductor region-type II crystal structure, or may contain the crystalline lithium sulfide superion conductor region-type II crystal structure as a main crystal. From the perspective of achieving higher ionic conductivity, it is preferred that the crystalline lithium sulfide superion conductor region-type II crystal structure be contained as a main crystal. In this specification, "containing as a main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or greater, preferably 90% or greater, and more preferably 95% or greater. Furthermore, from the perspective of achieving higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the production method of this embodiment preferably does not contain crystalline Li3PS4 (β-Li3PS4).

[0198] In the X-ray diffraction measurement using CuKα rays, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°; the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°; the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°; and the diffraction peaks of the Li7P3S 11The diffraction peaks of the crystal structure appear near 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, for example. 4-x Ge 1-x P x The diffraction peaks of the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) crystal structure appear near 2θ=20.1°, 23.9°, and 29.5°, which are similar to the Li 4-x Ge 1-x P x The diffraction peaks of the S4-type thio-LISICON Region II-type crystal structure appear, for example, near 2θ = 20.2 and 23.6°. Furthermore, these peak positions can fluctuate within a range of ±0.5°.

[0199] In the sulfide solid electrolyte produced in the present embodiment, as a crystalline sulfide solid electrolyte, the contents of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms are the same as those of the above-mentioned amorphous sulfide solid electrolyte.

[0200] Furthermore, the atomic composition ratios of the crystalline sulfide solid electrolyte are preferably within the range of the atomic composition ratios of the amorphous sulfide solid electrolyte described above, as determined by the composition formulas corresponding to the various crystal structures described above. Within this range of atomic composition ratios, a sulfide crystalline lithium superion conductor region-type II crystal structure or an argyrodite-type crystal structure is likely to be formed in the crystal structure described above.

[0201] (Properties of sulfide solid electrolyte)

[0202] The sulfide solid electrolyte obtained by the production method of this embodiment has a granular shape.

[0203] The median diameter of the granular sulfide solid electrolyte (D 50) is preferably less than 15 μm. As a result, the contact interface between the electrode active material and the sulfide solid electrolyte is easily formed, and the paths for ion conduction and electron conduction become good. It is more preferably less than 7.0 μm, further preferably less than 5.0 μm, and further preferably less than 4.0 μm. It can be adjusted by the above-mentioned crushing. The lower limit is not particularly limited, and is preferably greater than 0.01 μm, more preferably greater than 0.03 μm, further preferably greater than 0.05 μm, and further preferably greater than 0.1 μm. In the manufacturing method of this embodiment, it is impossible to generalize due to the raw material contents used, and the heating conditions of heating (1) and heating (2), but there is a case where a sulfide solid electrolyte with the above-mentioned median diameter can be obtained without crushing the obtained sulfide solid electrolyte, and it can also be adjusted to the above-mentioned median diameter by crushing.

[0204] Similarly, the particle size (D 10 ) is preferably 0.05 μm or more and 10.0 μm or less, more preferably 0.50 μm or more and 6.0 μm or less, and even more preferably 1.0 μm or more and 4.0 μm or less.

[0205] Furthermore, the particle size (D 90 ) is preferably 0.10 μm or more and 20.0 μm or less, more preferably 1.0 μm or more and 15.0 μm or less, and even more preferably 3.0 μm or more and 10.0 μm or less.

[0206] The particle size distribution of the sulfide solid electrolyte is given by (D 90 -D 10 ) / D 50 A value of 3.00 or less indicates a narrow particle size distribution, which is preferred. A value of 2.50 or less is more preferred, 2.00 or less is even more preferred, and 1.50 or less is even more preferred. While the lower limit is not particularly limited, it is preferably 0.01 or greater based on the performance and productivity of the spray drying apparatus.

[0207] The median diameter of the sulfide solid electrolyte can be measured, for example, by the measurement method described in Examples. In addition, the particle size distribution can be determined, for example, from the shape of the particle size distribution of the sulfide solid electrolyte.

[0208] The crystallite diameter of the sulfide solid electrolyte of this embodiment is preferably 30 nm or greater. From the perspective of improving ionic conductivity, it is preferably 33 nm or greater, more preferably 35 nm or greater, even more preferably 40 nm or greater, even more preferably 70 nm or greater, and even more preferably 80 nm or greater. The upper limit is not particularly limited, but from the perspective of productivity, it is preferably 300 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and even more preferably 130 nm or less.

[0209] The sulfide solid electrolyte of this embodiment, obtained by the production method of this embodiment, has an extremely high ionic conductivity due to controlled particle size, and can generally be 0.01 mS / cm or higher. It is more preferably 1.00 mS / cm or higher, further preferably 2.00 mS / cm or higher, even more preferably 2.50 mS / cm or higher, even more preferably 3.00 mS / cm or higher, and particularly preferably 3.50 mS / cm or higher. The upper limit is not particularly limited.

[0210] <Mixed>

[0211] In the method for producing a sulfide solid electrolyte according to the present embodiment, mixing is preferably performed during heating (1), heating (2), and temperature increase in order to promote the progress of the reaction.

[0212] The mixing may include stirring and pulverizing, and is preferably performed using a stirrer, a mixer or a pulverizer, more preferably a stirrer and a mixer.

[0213] As agitators and mixers, for example, a mechanical stirring mixer having a stirring blade in a tank can be exemplified. Mechanical stirring mixers can exemplify high-speed stirring mixers, double-arm type mixers, etc., and from the viewpoint of improving the uniformity of the raw materials in the mixture of the raw material containing material and the complexing agent, and obtaining higher ion conductivity, it is preferred to use a high-speed stirring mixer. In addition, as high-speed stirring mixers, vertical axis rotation type mixers, horizontal axis rotation type mixers, etc. can be exemplified, and any type of mixer can also be used.

[0214] The shape of the stirring blade used in the mechanical stirring mixer includes blade type, arm type, anchor type, paddle type, stirring paddle type, belt type, multi-stage blade type, double arm type, bucket type, biaxial blade type, flat blade type, C-type blade type, etc. From the viewpoint of improving the uniformity of the raw materials in the raw material content and obtaining higher ion conductivity, bucket type, flat blade type, C-type blade type, etc. are preferably used.

[0215] In addition, when a small amount is produced, stirring with a stirring bar may be used.

[0216] As the pulverizer, the pulverizer described above can be used.

[0217] (Solvent)

[0218] In the production method of this embodiment, a solvent can be used during heating (1) and / or heating (2) to form a slurry of the raw material content and / or the intermediate. In particular, using a solvent during heating (1) is preferred because hydrogen sulfide in the hydrogen sulfide atmosphere dissolves in the solvent, facilitating the reaction with the raw material content. As the solvent used, a wide range of solvents conventionally used in the production of sulfide solid electrolytes can be employed, with non-polar solvents and dispersants being preferred.

[0219] The solvent preferably contains a non-polar solvent, as described below, because it dissolves hydrogen sulfide and facilitates contact with the raw material contents while suppressing the effects of reactions with the raw material contents and the intermediate. Furthermore, the solvent preferably contains a dispersant, as described below, because the raw material contents are easily dispersed in the solvent, and the reaction to form the intermediate and the sulfide solid electrolyte is facilitated.

[0220] The amount of the solvent used is preferably 0.1 g to 50.0 g, more preferably 1.0 g to 30.0 g, and even more preferably 5.0 g to 25.0 g, relative to 1 g of the total mass of the raw material contents.

[0221] The nonpolar solvent and dispersant are described below.

[0222] (non-polar solvent)

[0223] The non-polar solvent used in the production method of this embodiment is preferably a solvent that poorly dissolves the raw material components, intermediates, and sulfide solid electrolyte. Specifically, a hydrocarbon solvent containing no heteroatoms is preferred. Examples of non-polar solvents include aliphatic hydrocarbon solvents such as pentane, hexane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, and tert-butylbenzene. Suitable solvents may be selected from these.

[0224] Among these solvents, aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents are preferred, and aromatic hydrocarbon solvents are more preferred. More specifically, 2-ethylhexane, heptane, octane, cyclohexane, benzene, toluene, xylene, ethylbenzene, or mesitylene are preferred, methylcyclohexane, benzene, toluene, xylene, or ethylbenzene are more preferred, and toluene or ethylbenzene are further preferred.

[0225] They can be used individually or in combination.

[0226] The amount of the nonpolar solvent used is preferably 0.1 g to 50.0 g, more preferably 0.5 g to 30.0 g, further preferably 1.0 g to 20.0 g, and even more preferably 3.0 g to 10.0 g, relative to 1 g of the total mass of the raw material contents.

[0227] (Dispersant)

[0228] The dispersant used in the production method of this embodiment has the property of dispersing the raw material content, the intermediate, and the sulfide solid electrolyte, but is preferably a dispersant that does not react with these. More specifically, an ether compound is preferred.

[0229] Examples of the ether compound include ether compounds such as aliphatic ether, alicyclic ether, heterocyclic ether and aromatic ether, and these ether compounds can be used alone or in combination of two or more.

[0230] Examples of the aliphatic ether include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and tert-butyl methyl ether; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, and diethoxyethane; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme) and triethylene glycol dimethyl ether; and ethers containing hydroxyl groups such as diethylene glycol and triethylene glycol.

[0231] The number of carbon atoms in the aliphatic ether is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ether is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0232] Examples of the alicyclic ether include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, and dioxolane. Examples of the heterocyclic ether include furan, benzofuran, benzopyran, dioxine, dioxin, morpholine, methoxyindole, and hydroxymethyldimethoxypyridine.

[0233] The carbon number of the alicyclic ether or heterocyclic ether is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0234] Examples of the aromatic ether include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether and naphthyl ether.

[0235] The number of carbon atoms in the aromatic ether is preferably 7 or more, more preferably 8 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0236] The amount of the dispersant used is preferably 0.10 g to 500.00 g, more preferably 0.50 g to 300.00 g, further preferably 0.80 g to 200.00 g, and even more preferably 1.00 g to 100.00 g, relative to 100 g of the total mass of the raw material contents.

[0237] (Crystallization)

[0238] The method for producing the sulfide solid electrolyte of the present embodiment may further include crystallization in order to obtain a crystalline sulfide solid electrolyte. Crystallization is preferably performed by heating.

[0239] Furthermore, heating the crystalline sulfide solid electrolyte to increase the crystallite size is preferred because it can also improve the ion conductivity.

[0240] Crystallization can also be performed by the above-mentioned heating (1) or heating (1) and heating (2), but including crystallization is preferred because a sulfide solid electrolyte having target crystals can be obtained.

[0241] When heating an amorphous sulfide solid electrolyte to obtain a crystalline sulfide solid electrolyte, the heating temperature can be determined based on the structure of the crystalline sulfide solid electrolyte. Using a differential thermal analyzer (DTA) apparatus, the amorphous sulfide solid electrolyte is subjected to differential thermal analysis (DTA) at a temperature increase rate of 10°C / minute. The starting point is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, with the upper limit being not particularly limited, but being approximately 40°C or lower. By setting the temperature within this 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 generally specified, but is generally preferably 200°C or higher, more preferably 300°C or higher, and even more preferably 350°C or higher. The upper limit is not particularly limited, but is preferably 600°C or lower, more preferably 500°C or lower, and even more preferably 450°C or lower.

[0242] The heating time is not particularly limited as long as it is a time that can produce the desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte. For example, it is preferably 1 minute or longer, more preferably 10 minutes or longer, even more preferably 30 minutes or longer, and even more preferably 1 hour or longer. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or shorter, more preferably 20 hours or shorter, even more preferably 15 hours or shorter, and even more preferably 10 hours or shorter.

[0243] Furthermore, heating is preferably performed in an inert gas atmosphere (e.g., nitrogen or argon) or under reduced pressure (particularly in a vacuum). This is because it prevents degradation (e.g., oxidation) of the crystalline sulfide solid electrolyte. The heating method is not particularly limited; examples include methods using a hot plate, a vacuum heater, an argon atmosphere furnace, or a firing furnace. Furthermore, industrially, horizontal dryers equipped with a heating unit and a feed mechanism, such as horizontal vibrating fluidized bed dryers, can also be used; the method can be selected based on the desired throughput.

[0244] (dry)

[0245] The method for producing a sulfide solid electrolyte according to the present embodiment preferably includes drying the sulfide solid electrolyte in order to obtain the sulfide solid electrolyte as a powder when the raw material-containing material is slurried using a solvent and the slurry is brought into contact with hydrogen sulfide.

[0246] Examples of drying methods include filtration using a glass filter, solid-liquid separation by decantation, and solid-liquid separation using a centrifuge. Specifically, in solid-liquid separation, the suspension is transferred to a container, and after solid precipitation, the complexing agent and, if necessary, the solvent are removed from the supernatant by decantation, or filtration using a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm, is easily performed.

[0247] Alternatively, drying may be performed by heating using a dryer or the like.

[0248] The drying can be carried out under any pressure conditions, such as increased pressure, normal pressure, or reduced pressure, but is preferably carried out under normal pressure or reduced pressure. In particular, if drying at a lower temperature is considered, it is preferably carried out under reduced pressure, or further under vacuum, using a vacuum pump or the like.

[0249] The drying temperature may be at or above the boiling point of the solvent used as needed. The specific temperature conditions vary depending on the type of solvent used and cannot be generalized, but are preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. The upper limit is preferably 110°C or lower, more preferably 85°C or lower, and even more preferably 70°C or lower.

[0250] In addition, as described above, the pressure condition is preferably set to normal pressure or reduced pressure. When set to reduced pressure, specifically, it is preferably 85 kPa or less, more preferably 80 kPa or less, and further preferably 70 kPa or less. The lower limit can be vacuum (0 kPa). Considering the ease of pressure adjustment, it is preferably 1 kPa or more, more preferably 2 kPa or more, and further preferably 3 kPa or more.

[0251] (use)

[0252] The sulfide solid electrolyte obtained by the production method of this embodiment has high ionic conductivity and a small median diameter, and therefore exhibits excellent battery performance and is suitable for use in lithium-ion batteries, especially all-solid-state batteries.

[0253] The sulfide solid electrolyte obtained by the production method of this embodiment can be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer. In addition, these layers can be produced by known methods.

[0254] Furthermore, the battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer. A known current collector can be used. For example, a layer obtained by coating a substance that reacts with the sulfide solid electrolyte, such as Au, Pt, Al, Ti, or Cu, with Au or the like can be used.

[0255] Example

[0256] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[0257] (1) Measurement method

[0258] (1-1) Crystal form determination based on powder X-ray diffraction (XRD) measurement

[0259] Powder X-ray diffraction (XRD) measurements were performed as follows.

[0260] The sulfide solid electrolyte powder obtained in the Examples and Comparative Examples was filled into a 20 mm diameter, 0.2 mm deep cell and flattened with glass to prepare a sample. This sample was sealed with a Kapton film for XRD and isolated from air, and measurements were performed under the following conditions.

[0261] Measuring device: D2 PHASER, manufactured by Bruker Corporation

[0262] Tube voltage: 30kV

[0263] Tube current: 10mA

[0264] X-ray wavelength: Cu-Kα ray

[0265] Optical system: Concentration method

[0266] Slit configuration: Soller slit 4°, divergence slit 1mm, Kβ filter (Ni plate)

[0267] Detector: semiconductor detector

[0268] Measuring range: 2θ = 10-60 degrees

[0269] Step width, scanning speed: 0.05deg, 0.05deg / second

[0270] The crystal form was determined from the 2θ value of the obtained peak.

[0271] (1-2) Measurement of Residual Li2S

[0272] The amount of Li2S remaining in each sulfide solid electrolyte was determined from the results of XRD measurements of the sulfide solid electrolytes obtained in the Examples and Comparative Examples. The residual amount of Li2S was analyzed using the solver function in Excel. The 2θ value of the measurement result obtained in (1-1) is designated A, the peak intensity is designated B, and the baseline used in the calculation and the intensity of the glass are designated C and D, respectively. Furthermore, the peak intensity for each 2θ value during baseline calculation was empirically calculated using the measurement system as follows.

[0273] C=-45.72*A+4600-457.2

[0274] When the peak angles are represented by E, F, G, and H, the widths are represented by I, J, K, and L, and the intensities are represented by M, N, O, and P, the glass strength D is calculated by the following mathematical formula.

[0275] [Number 1]

[0276]

[0277] In addition, if the background correction data for calculation is set to Q, it is as follows.

[0278] Q=BC

[0279] The peak position of the raw material Li2S at the initial stage of the reaction and the peak shift of the calculated Li2S peak are defined as R, and all peaks are added to R and reflected in the above Q. In addition, the peak intensity of the Li2S at the initial stage of the reaction is defined as S, and the peak intensity is fitted by multiplying the peak intensity S at the initial stage of the reaction by the coefficient T. If the total of the fitting residuals is defined as U, the result is as follows.

[0280] [Number 2]

[0281] U=∑(QT×SC)

[0282] In the calculation using the solver function, E, F, G, H, I, J, K, L, M, N, O, P, R, and T are used as variables, and the calculation is performed so that U becomes the minimum in the GRG nonlinearity to fit the Li2S residual.

[0283] (1-3) Measurement of ionic conductivity

[0284] The ionic conductivity of the sulfide solid electrolytes obtained in the present example and the comparative example was measured as follows.

[0285] Each crystalline solid electrolyte obtained in the examples and comparative examples was formed into a 10 mm diameter (cross-sectional area S: 0.785 cm 2 ), round particles with a height (L) of 0.1 to 0.3 cm are used to make a sample. The upper and lower parts of the sample are taken as electrode terminals, and the AC impedance method is used for measurement at 25°C (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. Near the right end of the arc observed in the high-frequency side area, the real part Z'(Ω) at the point where -Z"(Ω) is the minimum is used as the bulk resistance R(Ω) of the electrolyte, and the ionic conductivity σ(S / cm) is calculated according to the following formula.

[0286] R=ρ(L / S)

[0287] σ=1 / ρ

[0288] (1-4) median diameter (D 50 )

[0289] The volume-based median diameter is measured using a laser diffraction / scattering particle size distribution measuring device ("Partica LA-950V2 Model LA-950W2", manufactured by Horiba, Ltd.). A mixture of dehydrated toluene (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) and tert-butyl alcohol (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) at a weight ratio of 93.8:6.2 is used as a dispersion medium. 50 ml of the dispersion medium is injected into the flow cell of the device and circulated, and then the measurement object is added for ultrasonic treatment, and then the particle size distribution is measured. In addition, the amount of the measurement object is adjusted so that the red light transmittance (R) corresponding to the particle concentration converges to 90-90% and the blue light transmittance (B) converges to 70-90% in the measurement screen specified in the device. In addition, for the calculation conditions, 2.16 is used as the refractive index value of the measurement object, and 1.49 is used as the refractive index value of the dispersion medium. In the distribution form setting, the number of repetitions is fixed at 15 times to perform particle size calculation and calculate the median diameter (D 50 ).

[0290] (2) Slurry manufacturing method

[0291] (2-1) Method for producing slurry (1)

[0292] Under a nitrogen atmosphere, 33.06 g of lithium sulfide (Li2S), 45.69 g of phosphorus pentasulfide (P2S5), and 591 g of ethylbenzene were placed in a 1 L reaction tank equipped with a stirring blade. After the stirring blade was rotated, a pulverization process was started using a circulating bead mill (Star Mill LMZ015, manufactured by Ashizawa Finetech Co., Ltd.) under the specified conditions (bead material: zirconia, bead diameter: 0.5 mmφ, bead amount: 456 g, pump flow rate: 650 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 0°C). While the pulverization process was being carried out, a solution of 13.04 g of iodine (I2) dissolved in 260 g of ethylbenzene was added dropwise to the reaction tank over 30 minutes. Subsequently, 8.21 g of bromine (Br2) was added dropwise to the reaction tank over 30 minutes. After the addition was completed, the pulverization process was further carried out for 30 minutes to obtain slurry (1).

[0293] (2-2) Method for producing slurry (2)

[0294] Slurry (2) was obtained in the same manner as in the method for producing slurry (1) (2-1) except that toluene was used instead of ethylbenzene.

[0295] (Example 1)

[0296] Under a nitrogen atmosphere, 30 mL of the slurry (1) was placed in a Schlenk flask (capacity: 100 mL) equipped with a stirrer, and the stirrer was rotated. After hydrogen sulfide (H2S) was passed through the slurry (1) at room temperature for 1 hour at a flow rate of 100 mL / min, the temperature was raised to 50°C while hydrogen sulfide was still being passed, and hydrogen sulfide was passed at 50°C for 1 hour. Furthermore, the temperature was raised to 130°C while hydrogen sulfide was still being passed, and when the temperature reached 130°C, the flow of hydrogen sulfide was stopped, and nitrogen (N2) was passed at a flow rate of 100 mL / min, and nitrogen was passed at 130°C for 1 hour. Then, the slurry was cooled to room temperature and dried under reduced pressure at room temperature to obtain an amorphous sulfide solid electrolyte (1).

[0297] The obtained amorphous sulfide solid electrolyte (1) was subjected to XRD measurement and the Li2S balance was calculated to be 7%. The X-ray diffraction pattern is as follows Figure 2 shown.

[0298] Furthermore, the obtained amorphous sulfide solid electrolyte (1) was decompressed at 180°C for 2 hours to obtain a crystalline solid electrolyte (1). XRD measurement was performed on the obtained crystalline solid electrolyte (1). As a result, crystallization peaks were detected at 2θ=20.2° and 23.6° in the X-ray diffraction pattern, confirming the specific type II crystal structure of the sulfide crystallized lithium superion conductor region. The X-ray diffraction pattern is as follows: Figure 2Furthermore, the ionic conductivity of the obtained crystalline solid electrolyte (1) was measured and found to be 1.2 mS / cm.

[0299] (Example 2)

[0300] Under a nitrogen atmosphere, 30 mL of the slurry (1) and 4 mL of dibutyl ether were placed in a Schlenk flask (capacity: 100 mL) equipped with a stirrer, and the stirrer was rotated. After hydrogen sulfide (H2S) was passed through the slurry at room temperature for 1 hour at a flow rate of 100 mL / min, the temperature was raised to 50°C while hydrogen sulfide was still being passed, and hydrogen sulfide was passed at 50°C for 1 hour. Furthermore, the temperature was raised to 110°C while hydrogen sulfide was still being passed, and when the temperature reached 110°C, the flow of hydrogen sulfide was stopped, and nitrogen (N2) was passed at a flow rate of 100 mL / min, and nitrogen was passed at 110°C for 1 hour. Thereafter, the slurry was cooled to room temperature and then dried under reduced pressure at room temperature to obtain an amorphous sulfide solid electrolyte (2).

[0301] The obtained amorphous sulfide solid electrolyte (2) was subjected to XRD measurement and the Li2S balance was calculated to be 3%. The X-ray diffraction pattern is as follows Figure 3 shown.

[0302] Furthermore, the obtained amorphous sulfide solid electrolyte (2) was decompressed at 180°C for 2 hours to obtain a crystalline solid electrolyte (2). XRD measurement was performed on the obtained crystalline solid electrolyte (2). As a result, crystallization peaks were detected at 2θ=20.2° and 23.6° in the X-ray diffraction pattern, confirming that it had a type II crystal structure in the sulfide crystallized lithium superion conductor region. The X-ray diffraction spectrum is shown in Figure 3 Furthermore, the ionic conductivity of the obtained crystalline solid electrolyte (2) was measured and found to be 0.9 mS / cm.

[0303] (Example 3)

[0304] An amorphous sulfide solid electrolyte (3) and a crystalline solid electrolyte (3) were obtained in the same manner as in Example 2, except that the slurry (2) was used instead of the slurry (1).

[0305] The Li2S balance was measured using the obtained amorphous sulfide solid electrolyte (3), and the crystal form and ion conductivity were measured using the crystalline solid electrolyte (3). The measurement results are shown in Table 2. The X-ray diffraction patterns of the amorphous sulfide solid electrolyte (3) and the crystalline solid electrolyte (3) are shown in Figure 4 .

[0306] (Example 4)

[0307] Under a nitrogen atmosphere, 30 mL of the slurry (1) and 4 mL of dibutyl ether were added to a Schlenk flask (capacity: 100 mL) equipped with a stirrer, and the stirrer was rotated. Nitrogen (N2) was circulated in the slurry at a flow rate of 100 mL / min, and the temperature was raised to 110°C. When the temperature reached 110°C, the flow of nitrogen was switched to the flow of hydrogen sulfide (H2S) at a flow rate of 100 mL / min, and hydrogen sulfide was circulated at 110°C for 1 hour. Furthermore, the flow of hydrogen sulfide was stopped, and nitrogen was circulated at a flow rate of 100 mL / min and 110°C for 1 hour. Then, after cooling to room temperature, it was dried under reduced pressure at room temperature to obtain an amorphous sulfide solid electrolyte (4).

[0308] The obtained amorphous sulfide solid electrolyte (4) was reduced in pressure at 180°C for 2 hours to obtain a crystalline solid electrolyte (4).

[0309] The Li2S balance was measured using the obtained amorphous sulfide solid electrolyte (4), and the crystal form and ion conductivity were measured using the crystalline solid electrolyte (4). The measurement results are shown in Table 2. The X-ray diffraction patterns of the amorphous sulfide solid electrolyte (4) and the crystalline solid electrolyte (4) are shown in Figure 5 .

[0310] (Comparative Example 1)

[0311] An amorphous sulfide solid electrolyte (C1) and a crystalline solid electrolyte (C1) were obtained in the same manner as in Example 1, except that nitrogen (N2) was circulated instead of hydrogen sulfide (H2S).

[0312] The obtained amorphous sulfide solid electrolyte (C1) and crystalline solid electrolyte (C1) were used to measure the Li2S residual amount, crystal form and ion conductivity. The measurement results are recorded in Table 2. The X-ray diffraction patterns of the amorphous sulfide solid electrolyte (C1) and the crystalline solid electrolyte (C1) are shown in Figure 6 .

[0313] The outlines of the production methods performed in Examples 1 to 4 and Comparative Example 1 are summarized in Table 1. In the table, "rt" represents room temperature, and "H2S" and "N2" represent hydrogen sulfide gas flow and nitrogen gas flow, respectively.

[0314] [Table 1]

[0315]

[0316] [Table 2]

[0317] Table 2

[0318] <![CDATA[Remainder of Li2S]]> Crystal form Ionic conductivity Example 1 7％ R-II 1.2 Example 2 3％ R-II 0.9 Example 3 4％ R-II 0.9 Example 4 10％ R-II 0.5 Comparative Example 1 33％ Inadequate response 0.1

[0319] It was found that the Li2S in the produced powders (1) to (4) was consumed, and the amount of residual Li2S was small. In addition, it was confirmed that the crystalline solid electrolytes (1) to (4) had the target sulfide crystalline lithium superion conductor region II type crystal structure (recorded as R-II in Table 2) and also showed high ionic conductivity.

[0320] In contrast, the powder (C1) and crystalline solid electrolyte (C1) obtained in Comparative Example 1 still contained 33% of Li2S, indicating that the reaction had not progressed sufficiently. Furthermore, due to the incomplete reaction, the target crystal structure was not obtained from XRD (described as "incomplete reaction" in Table 2), and the ionic conductivity was also low.

[0321] (Example 5)

[0322] Under a nitrogen atmosphere, 30 mL of the slurry (1) and 4 mL of dibutyl ether were added to a Schlenk flask (capacity: 100 mL) equipped with a stirrer, and the stirrer was rotated. After hydrogen sulfide (H2S) was circulated in the slurry at room temperature at a flow rate of 100 mL / min for 1 hour, the temperature was raised to 50°C while hydrogen sulfide was circulated, and hydrogen sulfide was circulated at 50°C for 1 hour. Furthermore, the temperature was raised to 100°C while hydrogen sulfide was circulated, and hydrogen sulfide was circulated at 100°C for 1 hour. Then, the temperature was raised to 110°C while hydrogen sulfide was circulated, and at the time of reaching 110°C, the flow of hydrogen sulfide was stopped, and nitrogen (N2) was circulated at a flow rate of 100 mL / min, and nitrogen was circulated at 110°C for 1 hour. After cooling to room temperature, the slurry was dried under reduced pressure at room temperature to obtain an amorphous sulfide solid electrolyte (5).

[0323] Furthermore, the obtained amorphous sulfide solid electrolyte (5) was reduced in pressure at 180°C for 2 hours to obtain a crystalline solid electrolyte (5).

[0324] The Li2S balance was measured using the obtained amorphous sulfide solid electrolyte (5), and the crystal form and ion conductivity were measured using the crystalline solid electrolyte (5). The measurement results are shown in Table 4. The X-ray diffraction patterns of the amorphous sulfide solid electrolyte (5) and the crystalline solid electrolyte (5) are shown in Figure 7 .

[0325] (Example 6)

[0326] 450 mL of the slurry (2) and 60 mL of dibutyl ether were placed in a reaction tank (capacity: 1 L) equipped with a stirring blade under a nitrogen atmosphere, and the stirring blade was rotated. After hydrogen sulfide (H2S) was flowed through the slurry at room temperature at a flow rate of 100 mL / min for 90 minutes, the temperature was raised to 50°C while hydrogen sulfide was still flowing, and hydrogen sulfide was flowed at 50°C for 90 minutes. Then, the temperature was lowered to room temperature while hydrogen sulfide was still flowing. When the temperature reached room temperature, the flow of hydrogen sulfide was stopped, and nitrogen (N2) was flowed at a flow rate of 100 mL / min at room temperature for 1 hour. Then, a pulverization treatment was carried out for 30 minutes using a circulating bead mill (Star Mill LMZ015, manufactured by Ashizawa Finetech Co., Ltd.) under the specified conditions (bead material: zirconia, bead diameter: 0.3 mmφ, bead amount: 456 g, pump flow rate: 650 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 0°C). After hydrogen sulfide was passed through the obtained slurry at room temperature for 90 minutes at a flow rate of 100 mL / min, the temperature was raised to 50°C while hydrogen sulfide was still being passed, and hydrogen sulfide was passed at 50°C for 90 minutes. Furthermore, the temperature was raised to 110°C while hydrogen sulfide was still being passed, and when the temperature reached 110°C, the flow of hydrogen sulfide was stopped, and nitrogen (N2) was passed at a flow rate of 100 mL / min, and nitrogen was passed at 110°C for 90 minutes. After cooling to room temperature, the mixture was dried under reduced pressure at room temperature to obtain an amorphous sulfide solid electrolyte (6).

[0327] Furthermore, the obtained amorphous sulfide solid electrolyte (6) was reduced in pressure at 200°C for 2 hours to obtain a crystalline solid electrolyte (6).

[0328] The Li2S balance was measured using the obtained amorphous sulfide solid electrolyte (6), and the crystal form and ion conductivity were measured using the crystalline solid electrolyte (6). The measurement results are shown in Table 4. The X-ray diffraction patterns of the amorphous sulfide solid electrolyte (6) and the crystalline solid electrolyte (6) are shown in Figure 8 .

[0329] Table 3 summarizes the production methods performed in Examples 5 and 6. In the table, "rt" represents room temperature, and "H2S" and "N2" represent hydrogen sulfide gas flow and nitrogen gas flow, respectively.

[0330] [Table 3]

[0331] Table 3

[0332]

[0333] [Table 4]

[0334] Table 4

[0335] <![CDATA[Remainder of Li2S]]> Crystal form Ionic conductivity Example 5 2％ R-II 1.6 Example 6 2％ R-II 2.8

[0336] The results of Examples 5 and 6 confirmed that by performing multiple heating (1), the residual amount of Li2S can be further reduced and the ionic conductivity can be improved compared to Examples 1 to 4. In addition, the comparison between Examples 5 and 6 also confirmed that the ionic conductivity is further improved by performing pulverization between multiple heating (1). Although the residual amount of the raw material content remains unchanged, the ionic conductivity is improved. Therefore, it is believed that by combining heating (1) and pulverization, the miscibility of the intermediate is further improved, thereby forming more crystal form R-II of the crystalline solid electrolyte. As a result, it was confirmed that the ionic conductivity of the obtained sulfide solid electrolyte is further improved.

[0337] Industrial Applicability

[0338] According to the method for producing a sulfide solid electrolyte of the present embodiment, a sulfide solid electrolyte having a target crystal structure can be produced without requiring a high temperature during production.

[0339] The sulfide solid electrolyte obtained by the production method of this embodiment is suitable for use in lithium-ion batteries, particularly lithium-ion batteries used in information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones.

Claims

1. A method for producing a sulfide solid electrolyte, characterized in that: The method includes heating (1) of heating the raw material content while bringing hydrogen sulfide into contact with the raw material content, wherein the temperature T1 (° C.) of the heating (1) is 170° C. or lower.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The heating (1) is carried out under a gas flow of hydrogen sulfide.

3. The method for producing a sulfide solid electrolyte according to claim 2, wherein: The method comprises heating (2) for further heating after stopping the flow of hydrogen sulfide, wherein the temperature T2 (° C.) of the heating (2) is 170° C. or lower.

4. The method for producing a sulfide solid electrolyte according to claim 3, wherein: The heating (2) is performed in an atmosphere of nitrogen or a rare gas, or under reduced pressure.

5. The method for producing a sulfide solid electrolyte according to claim 3 or 4, wherein: The T1 and the T2 satisfy the relationship of T1≤T2≤170°C.

6. The method for producing a sulfide solid electrolyte according to claim 5, wherein: The temperature is increased from T1 to T2 under a gas flow of hydrogen sulfide.

7. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 6, wherein: The median diameter D of the raw material content 50 Less than 15μm.

8. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 7, wherein: Further comprising crushing.

9. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 8, wherein: The heating (1) is performed at least twice.

10. The method for producing a sulfide solid electrolyte according to claim 8 or 9, wherein: The heating (1) is performed at least twice, and the heating (1), the pulverization, and the heating (1) are performed in sequence.

11. The method for producing a sulfide solid electrolyte according to any one of claims 8 to 10, wherein: The pulverization includes pulverizing the raw material contents.

12. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 11, wherein: The raw material content is a mixture of sulfide solid electrolyte raw materials containing at least one selected from lithium atoms, sulfur atoms, and phosphorus atoms.

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