Cleaning method for devices, and production method and production apparatus for sulfide solid electrolyte

Abstract

Provided are: a cleaning method for safely and efficiently cleaning the insides of devices that configure a production apparatus for a sulfide solid electrolyte; and a production method and a production apparatus for a sulfide solid electrolyte.　This cleaning method for devices that configure a production apparatus for a sulfide solid electrolyte comprises: cleaning, with water, a sulfur atom-containing substance attached to the insides of the devices; and bringing a fluid containing a gas generated by the cleaning into contact with an alkaline aqueous solution. This production method for a sulfide solid electrolyte adopts said method. This production apparatus for a sulfide solid electrolyte comprises a water supply facility used in said cleaning method for devices.

Description

Equipment cleaning method, sulfide solid electrolyte manufacturing method and manufacturing device

[0001] The present invention relates to a method for cleaning equipment, a method for producing a sulfide solid electrolyte, and a production apparatus thereof.

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

[0003] As a method for producing a solid electrolyte used in a solid electrolyte layer, mass production has been studied, and a production method using a complexing agent has attracted attention as a method that is easily adaptable to scale-up. For example, a solid production method including using a specific compound having an amino group as a complexing agent and mixing the complexing agent with a solid electrolyte raw material to prepare an electrolyte precursor (see, for example, Patent Document 1), and a solid electrolyte production method including drying a slurry containing a complexing agent and an electrolyte precursor by fluidized drying using media particles (see, for example, Patent Document 2) are known.

[0004] International Publication No. 2020 / 105737 Pamphlet International Publication No. 2023 / 167237 Pamphlet

[0005] The present invention has been made in view of the above circumstances, and aims to provide a cleaning method for safely and efficiently cleaning the inside of devices constituting a sulfide solid electrolyte production apparatus, and also to provide a method and apparatus for producing a sulfide solid electrolyte.

[0006] The method for cleaning equipment according to the present invention is a method for cleaning equipment constituting an apparatus for producing a sulfide solid electrolyte, the method comprising: cleaning sulfur atom-containing substances adhering to the inside of the equipment with water; and bringing a fluid containing a gas generated by the cleaning into contact with an aqueous sodium hydroxide solution.

[0007] A method for producing a sulfide solid electrolyte according to the present invention is a method for producing a sulfide solid electrolyte, comprising: cleaning sulfur atom-containing substances adhering to the inside of equipment constituting an apparatus for producing a sulfide solid electrolyte by the method for cleaning equipment described above; and then using the apparatus for producing a sulfide solid electrolyte.

[0008] The sulfide solid electrolyte production apparatus according to the present invention is an apparatus for producing a sulfide solid electrolyte, comprising a water supply device that supplies water used for cleaning equipment.

[0009] According to the present invention, it is possible to provide a cleaning method for safely and efficiently cleaning the inside of devices constituting a sulfide solid electrolyte production apparatus, as well as a method and apparatus for producing a sulfide solid electrolyte.

[0010] FIG. 2 is a flow diagram illustrating the heating equipment and the separating equipment used in the examples and comparative examples.

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0012] (Findings Obtained by the Inventor to Achieve the Present Invention) The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found the following points, which have led to the completion of the present invention.

[0013] As the practical application of all-solid-state batteries is being studied, mass production of sulfide solid electrolytes has become an urgent issue, and as demand for sulfide solid electrolytes increases, efforts are underway to move from lab-scale facilities to plant-scale manufacturing equipment for longer-term, more stable, full-scale operation aimed at mass production. Unlike the production of sulfide solid electrolytes in lab-scale facilities, full-scale operation using plant-scale manufacturing equipment requires efficient maintenance work for the equipment.

[0014] The maintenance work mainly includes repair and replacement of the equipment and various parts used in the equipment, as well as cleaning of the interior of the equipment. The sulfide solid electrolyte manufacturing equipment is a device that handles substances containing sulfur atoms (hereinafter also referred to as "sulfur atom-containing substances"), such as solid electrolyte raw materials such as lithium sulfide and diphosphorus pentasulfide, intermediates such as electrolyte precursors, and the final sulfide solid electrolyte. These sulfur atom-containing substances may react with moisture in the atmosphere to generate a gas-containing fluid, typically a fluid containing hydrogen sulfide, so safety must be taken into consideration.

[0015] When maintenance work is performed while paying attention to safety, it often results in a decrease in work efficiency, and safety and work efficiency are in a trade-off relationship. Therefore, when proceeding with full-scale operation of plant-scale manufacturing equipment, maintenance work that achieves both safety and work efficiency at a high level is required.

[0016] Incidentally, among the above-mentioned maintenance work, when repairing, replacing, or the like, equipment and parts used in the equipment, it is extremely effective to clean the equipment to be maintained, particularly the interior of the equipment, beforehand. Performing the work while constantly worrying about sulfur-atom-containing substances adhering to the interior of the equipment reacting with moisture in the atmosphere to generate gas-containing fluids, typically fluids containing hydrogen sulfide, leads to a significant decrease in work efficiency. Cleaning the interior of the equipment prior to maintenance work enables easier safety measures, improving work efficiency while ensuring safety. Therefore, improving the work efficiency of cleaning the interior of the equipment while ensuring safety leads to improved safety and work efficiency in maintenance work, and further allows for easier full-scale operation of plant-scale manufacturing equipment, leading to an improvement in the availability of the equipment.

[0017] The present inventors focused on the cleaning medium used for cleaning equipment to be maintained, particularly the interior of the equipment. When water is used to clean the interior of the equipment, a reaction between sulfur-containing substances adhering to the interior of the equipment and water may generate a fluid typically containing hydrogen sulfide. Therefore, the inventors investigated the use of a sodium hydroxide aqueous solution as an alkaline aqueous solution highly reactive with hydrogen sulfide. However, it was found that cleaning with a sodium hydroxide aqueous solution tends to leave sodium in the equipment, and the remaining sodium entrains with the solid electrolyte, reducing the performance of the solid electrolyte. Furthermore, it was found that attempting to clean the remaining sodium in the equipment with water to a level that does not affect the performance of the solid electrolyte requires multiple cleanings, resulting in a significant decrease in work efficiency and an increase in wastewater. This phenomenon occurs not only with sodium hydroxide aqueous solution but also with other alkaline aqueous solutions.

[0018] Therefore, the present inventors decided to use water as a cleaning medium and investigated the recovery of hydrogen sulfide, which is typically generated. Using water as a cleaning medium and employing an alkaline aqueous solution to recover the fluid containing the generated gas, typically a fluid containing hydrogen sulfide, made it possible to improve work efficiency while ensuring safety. Thus, the cleaning method of the present invention made it possible to safely and efficiently clean the interior of the components constituting an apparatus for producing a sulfide solid electrolyte.

[0019] (Regarding various aspects of the present embodiment) A method for cleaning equipment according to a first aspect of the present embodiment is a method for cleaning equipment constituting an apparatus for producing a sulfide solid electrolyte, the method including: cleaning sulfur atom-containing substances adhering to the inside of the equipment with water; and bringing a fluid containing a gas generated by the cleaning into contact with an alkaline aqueous solution.

[0020] When a sulfide solid electrolyte production apparatus is operated to produce a sulfide solid electrolyte, sulfur-containing substances (sulfur atom-containing substances) such as solid electrolyte raw materials such as lithium sulfide and diphosphorus pentasulfide, intermediates such as electrolyte precursors produced during the production process, and the final sulfide solid electrolyte are present and adhered to the interior of the equipment. When performing maintenance work on equipment with sulfur atom-containing substances adhered to its interior, particularly on its interior, it is essential to clean and remove the sulfur atom-containing substances adhered to the interior of the equipment, as described above. Cleaning the interior of the equipment safely and efficiently improves the safety and efficiency of maintenance work, ultimately facilitating full-scale operation of plant-scale production equipment and improving the availability of the equipment.

[0021] Sulfur-atom-containing substances have the property of easily reacting with water, and are substances that easily generate hydrogen sulfide through this reaction. Therefore, from the viewpoint of safety, efforts have been made to prevent contact between sulfur-atom-containing substances and water. In contrast, the equipment cleaning method of this embodiment uses water, which has been avoided in facilities that handle sulfur-atom-containing substances, and focuses on safely and reliably recovering a fluid containing the generated gas, typically a fluid containing hydrogen sulfide. Then, the generated gas-containing fluid is brought into contact with an alkaline aqueous solution, and the gas-containing fluid, typically hydrogen sulfide gas contained in the fluid, is dissolved in the alkaline aqueous solution and recovered. In this way, the equipment cleaning method of this embodiment is believed to enable safe and efficient cleaning of the interior of equipment.

[0022] The equipment cleaning method according to a second aspect of the present embodiment is the above-described first aspect, wherein the sulfur atom-containing substance is at least one substance selected from a solid electrolyte raw material, an electrolyte precursor, and a sulfide solid electrolyte, each containing a sulfur atom.

[0023] The target of cleaning in the equipment cleaning method of this embodiment is a sulfur atom-containing substance adhering to the inside of equipment constituting an apparatus for producing a sulfide solid electrolyte, and typically includes at least one substance selected from the group consisting of a solid electrolyte raw material, an electrolyte precursor, and a sulfide solid electrolyte, each containing a sulfur atom. Cleaning these sulfur atom-containing substances improves the safety and efficiency of maintenance work, ultimately leading to easier full-scale operation of a plant-scale production apparatus and an improvement in the availability of the facility.

[0024] A method for cleaning equipment according to a third aspect of the present embodiment is the first or second aspect, wherein the cleaning is performed by filling the inside of the equipment with water and then draining it. A method for cleaning equipment according to a fourth aspect is any one of the first to third aspects, wherein the cleaning is performed by spray cleaning using the water.

[0025] In the equipment cleaning method of this embodiment, the method of cleaning the sulfur atom-containing substances adhering to the inside of the equipment with water is preferably carried out by filling the inside of the equipment with water and then draining it, or by spray cleaning with water, from the viewpoint of safer, more efficient, and more reliable cleaning.

[0026] The equipment cleaning method according to a fifth aspect of the present embodiment is the method of any one of the first to fourth aspects, wherein the contacting is carried out by supplying an inert gas into the equipment and bringing the generated gas and a fluid containing the inert gas into contact with the alkaline aqueous solution.The equipment cleaning method according to a sixth aspect is the method of any one of the first to fifth aspects, wherein the contacting is carried out using a gas-liquid contactor.

[0027] In the equipment cleaning method of this embodiment, preferred methods for contacting a fluid containing a gas generated by cleaning with an alkaline aqueous solution include a method in which an inert gas is supplied into the equipment and the fluid containing the generated gas and the inert gas is brought into contact with an alkaline aqueous solution, and a method in which a gas-liquid contactor is used, from the viewpoint of more safely and efficiently recovering hydrogen sulfide more reliably by contacting a gas contained in the fluid, typically hydrogen sulfide, with an alkaline aqueous solution.

[0028] A seventh aspect of the present embodiment is a method for cleaning equipment according to any one of the first to sixth aspects, wherein the cleaning is performed without using an alkaline aqueous solution.

[0029] By performing cleaning without using an alkaline aqueous solution, it is possible to suppress the entrainment of metal atoms constituting the alkaline compounds contained in the alkaline aqueous solution into the solid electrolyte, thereby suppressing a decrease in the performance of the solid electrolyte. Furthermore, it is possible to suppress the metal atoms constituting the alkaline compounds contained in the alkaline aqueous solution from remaining inside the device, which eliminates the need for multiple cleanings and enables more efficient device cleaning.

[0030] An equipment cleaning method according to an eighth aspect of the present embodiment is any one of the first to seventh aspects, wherein the water used for the cleaning has a metal ion content of 1000 mass ppm or less, and an equipment cleaning method according to a ninth aspect is any one of the first to eighth aspects, wherein the water used for the cleaning has an alkali metal ion content of 1000 mass ppm or less.

[0031] The water used in the equipment cleaning method of the present embodiment is water that does not contain metal ions, nor alkali metal ions. By performing cleaning using such water, entrainment of metal ions contained in the water into the solid electrolyte can be suppressed, thereby suppressing a decrease in the performance of the solid electrolyte and simultaneously suppressing metal residue inside the equipment. This eliminates the need for multiple cleanings and enables more efficient equipment cleaning.

[0032] An equipment cleaning method according to a tenth aspect of the present embodiment is any one of the first to ninth aspects, wherein the amount of alkaline compound contained in the alkaline aqueous solution supplied per 1 molar part of hydrogen sulfide supplied in the generated gas is 2.5 molar parts or more. An equipment cleaning method according to an eleventh aspect is any one of the first to tenth aspects, wherein the alkaline aqueous solution is a sodium hydroxide aqueous solution.

[0033] By using an alkaline aqueous solution in an amount within the above range, it becomes possible to more reliably recover gases contained in the fluid, typically hydrogen sulfide. Furthermore, by using sodium hydroxide as the alkaline aqueous solution, it becomes possible to more reliably recover gases contained in the fluid, typically hydrogen sulfide.

[0034] A method for producing a sulfide solid electrolyte according to a twelfth aspect of the present embodiment is a method for producing a sulfide solid electrolyte, comprising cleaning sulfur atom-containing substances adhering to the inside of equipment constituting an apparatus for producing a sulfide solid electrolyte by the method for cleaning equipment according to any one of the first to eleventh aspects, and then using the apparatus for producing a sulfide solid electrolyte.

[0035] In the method for producing a sulfide solid electrolyte of this embodiment, the equipment can be cleaned safely and efficiently by performing cleaning using the equipment cleaning method of this embodiment. This makes it easier to operate a sulfide solid electrolyte production apparatus, particularly a plant-scale production apparatus, equipped with the cleaned equipment, and improves its availability. That is, the method for producing a sulfide solid electrolyte of this embodiment makes it possible to clean the equipment safely and efficiently and quickly perform equipment maintenance work as needed. This makes it easier to operate a sulfide solid electrolyte production apparatus, particularly a plant-scale production apparatus, and improves its availability.

[0036] A thirteenth aspect of the present embodiment relates to the method for producing a sulfide solid electrolyte of the twelfth aspect, wherein a content of metal atoms constituting an alkali compound contained in the alkaline aqueous solution contained in the sulfide solid electrolyte is less than 1 ppm by mass.

[0037] According to the method for producing a sulfide solid electrolyte of this embodiment, the interior of the device is washed using water, and therefore the content of the above metal atoms contained in the obtained sulfide solid electrolyte can be extremely reduced. Therefore, the obtained sulfide solid electrolyte is of high quality, with few impurities and high ionic conductivity. A content of the above metal atoms of less than 1 ppm by mass can be said to mean that an alkaline aqueous solution is not used to wash the interior of the device.

[0038] As described above, according to the method for producing a sulfide solid electrolyte of the present embodiment, not only can the full-scale operation of a sulfide solid electrolyte production apparatus, particularly a plant-scale production apparatus, be more easily performed, and the operating rate can be improved, but also a high-quality sulfide solid electrolyte can be produced.

[0039] A sulfide solid electrolyte manufacturing apparatus according to a fourteenth aspect of the present embodiment includes a water supply device that supplies water used for cleaning equipment.

[0040] The sulfide solid electrolyte production apparatus of this embodiment is equipped with the water supply device, and thus can be cleaned using the equipment cleaning method of this embodiment, enabling safe and efficient equipment cleaning. Therefore, the sulfide solid electrolyte production apparatus of this embodiment can be more easily operated on a full scale, and its availability rate can be increased. Furthermore, the water supply device can be easily scaled, allowing it to be easily adapted to the scale of the production apparatus, and can be easily adapted to plant-scale apparatus.

[0041] A sulfide solid electrolyte manufacturing apparatus according to a fifteenth aspect of the present embodiment is the fourteenth aspect, further comprising an inert gas supply device that supplies an inert gas to the device.

[0042] By providing an inert gas supply device, the method for cleaning equipment according to the fifth embodiment of the present invention, i.e., contacting, can be more easily carried out by supplying an inert gas into the interior of the equipment and bringing the generated gas and a fluid containing the inert gas into contact with the alkaline aqueous solution.

[0043] A sulfide solid electrolyte production apparatus according to a sixteenth aspect of this embodiment is the fourteenth or fifteenth aspect, further comprising a gas-liquid contactor that brings a fluid containing gas generated by cleaning the equipment into contact with an alkaline aqueous solution.

[0044] By providing the gas-liquid contactor, the equipment cleaning method according to the sixth embodiment of the present invention, that is, contact using the gas-liquid contactor, can be more easily carried out.

[0045] The solid electrolyte of this embodiment will be described in more detail below in accordance with the above embodiment.

[0046] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. The solid electrolyte in this embodiment preferably contains lithium atoms, phosphorus atoms, and sulfur atoms, and more preferably contains halogen atoms, and is a solid electrolyte that uses lithium atoms as conductive species and has ionic conductivity due to the lithium atoms. Here, those containing sulfur atoms are also called "sulfide solid electrolytes."

[0047] The term "solid electrolyte" includes both crystalline solid electrolytes and amorphous solid electrolytes. In this specification, a crystalline solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in an X-ray diffraction pattern in X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present. That is, a crystalline solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a portion of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as a crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also contain an amorphous solid electrolyte in part. Therefore, crystalline solid electrolytes include so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature equal to or higher than its crystallization temperature. Furthermore, in this specification, an amorphous solid electrolyte is an electrolyte in which a halo pattern in X-ray diffraction measurement shows substantially no peaks other than those derived from the material, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0048] [Equipment Cleaning Method] The equipment cleaning method of the present embodiment is a method for cleaning equipment constituting an apparatus for producing a sulfide solid electrolyte, and includes cleaning sulfur atom-containing substances adhering to the inside of the equipment with water, and bringing a fluid containing a gas generated by the cleaning into contact with an alkaline aqueous solution.

[0049] The equipment constituting the sulfide solid electrolyte production apparatus to be cleaned by the equipment cleaning method of this embodiment varies depending on the production method, but mainly includes reaction equipment used in the reaction of solid electrolyte raw materials; heating equipment for removing a solvent (including a complexing agent) from a slurry or solution containing the solid electrolyte raw material and / or electrolyte precursor and the solvent (including a complexing agent) when a solvent (including a complexing agent) is used; heating equipment for crystallization, etc.; separation equipment for separating the sulfide solid electrolyte; particle size adjustment equipment for adjusting the particle size of the sulfide solid electrolyte; and piping connecting these equipment. These equipment will be described in detail in the description of the sulfide solid electrolyte production method and production apparatus of this embodiment. When the sulfide solid electrolyte production apparatus is operated, sulfur atom-containing substances such as solid electrolyte raw materials, intermediates such as an electrolyte precursor when a complexing agent is used, and even the final product, the sulfide solid electrolyte, adhere to the interior of these equipment and piping. In the equipment cleaning method of this embodiment, all equipment constituting the sulfide solid electrolyte production apparatus and to which sulfur atom-containing substances may adhere during operation are targeted for cleaning.

[0050] The sulfur-atom-containing substances removed from the interior of equipment by the equipment cleaning method of this embodiment include, as described above, solid electrolyte raw materials, electrolyte precursors when a complexing agent is used, and sulfide solid electrolyte products. These sulfur-atom-containing substances may adhere individually to the interior of the equipment, or multiple types of sulfur-atom-containing substances may adhere to the interior of a single equipment. For example, the solid electrolyte raw materials and sulfide solid electrolyte, or the electrolyte precursor when a complexing agent is used, adhere to the interior of the reactor. The remaining solid electrolyte raw materials, the electrolyte precursor, and the sulfide solid electrolyte produced by removing the complexing agent from the electrolyte precursor adhere to the interior of the heating equipment. The sulfide solid electrolyte, as well as the remaining solid electrolyte raw materials and electrolyte precursor, adhere to the separation equipment. Thus, the sulfur-atom-containing substances removed from the interior of equipment by the equipment cleaning method of this embodiment are at least one substance selected from solid electrolyte raw materials, electrolyte precursors, and sulfide solid electrolytes containing sulfur atoms. Details of these sulfur-atom-containing substances will be described in detail in the description of the method and apparatus for producing a sulfide solid electrolyte of this embodiment.

[0051] (Cleaning with Water) The method for cleaning the inside of a device according to this embodiment includes cleaning the sulfur atom-containing substance attached to the inside of the device with water. By using water for cleaning, unnecessary metal atoms are prevented from remaining inside the device. Therefore, it is possible to suppress the entrainment of metal atoms remaining inside the device into the sulfide solid electrolyte, and a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity can be obtained.

[0052] Preferred examples of water used in washing include distilled water, ion-exchanged water, etc. From the viewpoint of suppressing entrainment of metal atoms remaining inside the device into the sulfide solid electrolyte and obtaining a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity, it is preferable not to use various aqueous solutions such as alkaline aqueous solutions as water for washing.

[0053] The water used in the method for cleaning the interior of equipment according to this embodiment, such as the distilled water and ion-exchanged water exemplified above, preferably has a metal ion content of 1,000 ppm by mass or less, more preferably 800 ppm by mass or less, even more preferably 500 ppm by mass or less, and even more preferably 100 ppm by mass. Furthermore, since the lower the metal ion content in water, the better, there is no particular lower limit. 0 ppm by mass, i.e., no metal ions, is preferred. However, considering the increased cost of using such water, the metal ion content may be typically 0.1 ppm by mass or more, even 1 ppm by mass or more, 3 ppm by mass or more, or 5 ppm by mass or more. Furthermore, for alkali metal ions (e.g., typically sodium ions and potassium ions) contained in distilled water, ion-exchanged water, etc., the alkali metal ion content is preferably in the same range as the metal ion content. The metal ion and alkali metal ion content in water can be measured, for example, using an atomic absorption spectrophotometer. Thus, the water used in the method for cleaning the inside of equipment according to this embodiment is water also known as pure water.

[0054] The method of cleaning with water is not particularly limited as long as it uses water, but preferred examples include a method in which the inside of the equipment is filled with water and then drained, and a method in which water is sprayed for cleaning. Cleaning with water using these methods allows for safer, more efficient, and more reliable cleaning. In the method for cleaning equipment of this embodiment, these methods may be used alone or in combination. For example, it is possible to fill the inside of the equipment with water, then drain the water, and then spray clean.

[0055] When sulfur atom-containing substances adhering to the inside of equipment are washed with water, hydrogen sulfide gas is generated by the reaction between the sulfur atom-containing substances and water. Therefore, examples of fluids containing the generated gas include fluids containing hydrogen sulfide gas. Gas-containing fluids may include, for example, water vapor generated by evaporation of a portion of the water used for washing, as well as inert gases used as needed. The inert gases used as needed are primarily used by contact, as described below.

[0056] The water used in washing with water may be discarded as is, or may be treated as necessary depending on the content of sulfur atom-containing compounds before being discarded. When treating the water, for example, treatment of sulfur atom-containing substances and treatment of hydrogen sulfide can be performed using water treatment equipment such as removal equipment for removing sulfur atom-containing substances from wastewater containing water used for washing equipment and removal equipment for removing hydrogen sulfide from wastewater. These removal treatments may be performed based on methods commonly used industrially.

[0057] Furthermore, the water used in washing with water can be reused in washing with water. The reuse of water can be carried out using, for example, a water recycling system including the above-mentioned water treatment facility, a water storage tank, a water circulation pump, and other equipment, as well as piping connecting these treatment facilities and equipment.

[0058] (Contacting the fluid containing the generated gas with an alkaline aqueous solution) The method for cleaning equipment of this embodiment includes contacting the fluid containing the gas generated by cleaning with an alkaline aqueous solution (hereinafter also simply referred to as "contacting"). As described above, the fluid containing the gas generated by cleaning contains hydrogen sulfide as a gas, and therefore, by contacting this with an alkaline aqueous solution, it is possible to recover hydrogen sulfide from the fluid.

[0059] In the equipment cleaning method of this embodiment, the cleaning with water and the contacting are preferably carried out simultaneously. In the cleaning with water, gas, typically hydrogen sulfide, is generated as soon as water is supplied to the interior of the equipment, i.e., from the moment water comes into contact with the sulfur atom-containing substance. Therefore, it is safer and more efficient to immediately recover the generated gas with an alkaline aqueous solution.

[0060] The aqueous alkali solution used for contacting may be either an inorganic aqueous alkali solution containing an inorganic alkali compound or an organic alkali compound containing an organic alkali compound. Preferred examples of the inorganic alkali compound contained in the aqueous inorganic alkali solution include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; compounds containing metal atoms such as alkali metal carbonates or bicarbonates such as lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate; and compounds such as ammonia.

[0061] Preferred examples of the organic alkali compound contained in the organic alkali aqueous solution include compounds such as alkanolamines such as monoethanolamine, diethanolamine, and methyldiethanolamine; alkylamines such as methylamine, dimethylamine, ethylamine, diethylamine, N-methylethylamine, propylamine, and butylamine; and aralkylamines such as benzylamine.

[0062] Among the above alkaline aqueous solutions, inorganic alkaline aqueous solutions containing inorganic alkaline compounds are preferred from the viewpoint of high reactivity with hydrogen sulfide and more reliable recovery of hydrogen sulfide. Among the inorganic alkaline aqueous solutions, alkali metal hydroxides are preferred, with sodium hydroxide being more preferred. Furthermore, the metal atom contained in the inorganic alkaline compound is preferably an alkali metal, with potassium and sodium being preferred, and sodium being more preferred.

[0063] The content of the alkaline compound in the alkaline aqueous solution cannot be generalized because it varies depending on the type of alkaline compound, but is usually 0.1% by mass or more and 50% by mass or less, preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, with the upper limit preferably being 30% by mass or less. When the content is within the above range, hydrogen sulfide can be recovered more reliably and the handleability of the alkaline aqueous solution is improved.

[0064] The amount of alkaline aqueous solution supplied is not particularly limited as long as hydrogen sulfide can be recovered, but from the viewpoint of more reliably recovering hydrogen sulfide, the amount of alkaline compound contained in the alkaline aqueous solution supplied per 1 molar part of hydrogen sulfide supplied in the generated gas is preferably 2.5 molar parts or more, more preferably 3.5 molar parts or more, and even more preferably 5.0 molar parts or more. There is no particular upper limit, and from the viewpoint of more efficiently recovering hydrogen sulfide, it may be 15.0 molar parts or less, preferably 12.5 molar parts or less, and more preferably 10.0 molar parts or less.

[0065] The method for contacting a fluid containing a gas generated by washing with an alkaline aqueous solution is not particularly limited as long as it can bring the fluid into contact with the alkaline aqueous solution, but preferred examples include a method in which an inert gas is supplied into an apparatus and the fluid containing the generated gas and the inert gas is brought into contact with the alkaline aqueous solution, and a method in which a gas-liquid contactor is used. As described above, these methods enable hydrogen sulfide to be recovered more safely and efficiently, and more reliably by contacting a gas contained in the fluid, typically hydrogen sulfide, with an alkaline aqueous solution.

[0066] These methods can be carried out alone or in combination. When these methods are carried out in combination, the generated gas and inert gas can be contacted with the alkaline aqueous solution using a gas-liquid contactor.

[0067] The method using an inert gas is a method in which the gas generated by the cleaning is supplied to an alkaline aqueous solution using the inert gas, and contacted with the alkaline aqueous solution. Supplying an inert gas facilitates contact with the alkaline aqueous solution without using an exhaust fan, which is effective in reducing energy consumption. Preferred inert gases include rare gases such as helium and argon; nitrogen, and the like, with nitrogen being preferred from an economical viewpoint.

[0068] When the above-mentioned method using an inert gas is adopted, the sulfide solid electrolyte production apparatus is preferably equipped with an inert gas supply facility that supplies an inert gas to the devices constituting the production apparatus. The type of the inert gas supply facility is not particularly limited as long as it can supply an inert gas to the devices.

[0069] In the above method using an inert gas, the generated gas and the fluid containing the inert gas may be brought into contact with the aqueous alkaline solution using a gas-liquid contactor described below.

[0070] The gas-liquid contactor is usually also called a scrubber, and a wet scrubber capable of contacting a fluid containing a gas with an alkaline aqueous solution is preferably used. The gas-liquid contactor is not particularly limited in type as long as it can contact a fluid containing the generated gas with an alkaline aqueous solution, and preferred examples include devices generally provided in wet scrubbers, such as a washing tower where the contact takes place, a tank for storing the alkaline aqueous solution that serves as the washing liquid, a pump for circulating the alkaline aqueous solution, and an exhaust fan as needed, and devices equipped with piping connecting these devices.

[0071] As the scrubbing tower used in the gas-liquid contactor, any scrubbing tower commonly used in scrubbers can be used without limitation, and preferred examples include scrubbing towers such as bubble towers and spray towers. Various types of scrubbers, such as Venturi scrubbers, can also be used. As the scrubbing tower, a scrubbing tower of a type in which an alkaline aqueous solution can be supplied from the top of the scrubbing tower and a gas-containing fluid can be supplied from the bottom is preferred. Furthermore, the scrubbing tower is preferably equipped with a spray nozzle (also called a shower nozzle, etc.) so that the alkaline aqueous solution can be supplied in a spray form to better contact with the gas-containing fluid, i.e., a spray tower scrubbing tower.

[0072] The scrubbing tower may be provided with a packed bed composed of packing materials such as Raschig rings, Pall rings, etc., in order to promote contact between the gas-containing fluid and the alkaline aqueous solution. In addition, a demister may be provided at the top of the scrubbing tower in order to reduce entrainment of water droplets.

[0073] The optional exhaust fan is a fan provided to discharge a fluid containing the generated gas from the equipment to be cleaned and supply it to the scrubbing tower. When the method using an inert gas is not adopted, i.e., when the generated gas is brought into contact with an alkaline aqueous solution without using an inert gas, it is preferable to use an exhaust fan. The exhaust fan may be provided, for example, between the equipment to be cleaned and the scrubbing tower, or on a pipe that releases the fluid discharged from the scrubbing tower into the atmosphere.

[0074] [Method for Producing Sulfide Solid Electrolyte] A method for producing a sulfide solid electrolyte according to the present embodiment is a method for producing a sulfide solid electrolyte, comprising cleaning sulfur atom-containing substances adhering to the inside of equipment constituting an apparatus for producing a sulfide solid electrolyte by the above-described method for cleaning equipment according to the present embodiment, and then using the apparatus for producing a sulfide solid electrolyte.

[0075] The method for producing a sulfide solid electrolyte of this embodiment includes cleaning sulfur atom-containing substances adhering to the inside of equipment constituting an apparatus for producing a sulfide solid electrolyte by the above-described equipment cleaning method of this embodiment. This allows the inside of the equipment constituting the production apparatus to be cleaned safely and efficiently, allowing maintenance work to be performed promptly. This reduces the downtime of the production apparatus due to maintenance work, making it possible to produce a sulfide solid electrolyte with a higher operating rate even when using the same production apparatus.

[0076] The method for producing a sulfide solid electrolyte of this embodiment includes, following the above-mentioned cleaning, using a sulfide solid electrolyte production apparatus. The sulfide solid electrolyte production apparatus employed in the method for producing a sulfide solid electrolyte of this embodiment includes a water supply device that supplies water used to clean at least the sulfur atom-containing substance adhering to the inside of the apparatus. Furthermore, the sulfide solid electrolyte production apparatus employed in the method for producing a sulfide solid electrolyte of this embodiment further includes, in addition to the water supply device, various devices according to the production technique used to react solid electrolyte raw materials to obtain a sulfide solid electrolyte.

[0077] (Washing the sulfur atom-containing substance) The method for washing the sulfur atom-containing substance is the equipment washing method of the present embodiment. The specific washing method is as described above for the equipment washing method of the present embodiment.

[0078] (Use of an Apparatus for Producing a Sulfide Solid Electrolyte) In the method for producing a sulfide solid electrolyte of this embodiment, using an apparatus for producing a sulfide solid electrolyte essentially means producing a sulfide solid electrolyte, that is, obtaining a sulfide solid electrolyte by reacting solid electrolyte raw materials. As described above, the apparatus for producing a sulfide solid electrolyte includes various devices according to the production method used to obtain a sulfide solid electrolyte by reacting solid electrolyte raw materials. The apparatus for producing a sulfide solid electrolyte will be described below in conjunction with the reaction of solid electrolyte raw materials to obtain a sulfide solid electrolyte.

[0079] In obtaining a sulfide solid electrolyte by reacting the solid electrolyte raw materials, the reaction of the solid electrolyte raw materials may be carried out by a known method such as a mechanical milling method, a melt-cooling method, or a slurry method (including a solution method).

[0080] (Mechanical Milling Method) When the mechanical milling method is employed, the apparatus for producing the sulfide solid electrolyte may include at least a reaction device equipped with a pulverizer that pulverizes the solid electrolyte raw materials to cause a reaction, and further, as necessary, a heating device that performs heating for crystallization, etc. The sulfide solid electrolyte and remaining solid electrolyte raw materials may adhere to the inside of the reaction device equipped with the pulverizer and the heating device.

[0081] As the pulverizer, a media-type pulverizer using a pulverizing medium can be used. Media-type pulverizers are broadly classified into container-driven pulverizers and media-agitation pulverizers. Examples of container-driven pulverizers include agitation tanks, grinding tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation pulverizers include impact pulverizers such as cutter mills, hammer mills, and pin mills; tower-type pulverizers such as tower mills; agitation tank pulverizers such as attritors, aquamizers, and sand grinders; flow tank pulverizers such as Viscomill and pearl mills; flow pipe pulverizers; annular pulverizers such as Coball mills; continuous dynamic pulverizers; and single- or multi-shaft kneaders. Considering the ease of adjusting the particle size of the resulting sulfide, the ball mills and bead mills exemplified as container-driven pulverizers are preferred, and planetary pulverizers are particularly preferred.

[0082] Furthermore, when a solvent is used to pulverize the solid electrolyte raw material and the material to be pulverized is in a liquid or slurry state, a flow-through pulverizer capable of circulating the material as needed can also be used. Specific examples of the flow-through pulverizer include a pulverizer that circulates the slurry between a pulverizer (pulverizer mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel).

[0083] When a solvent is used during mechanical milling of the solid electrolyte raw material, drying may be performed to remove the solvent. When removing the solvent, various dryers can be used, such as vacuum dryers; pneumatic dryers such as stationary dryers, fluidized dryers, medium-fluidized dryers, and spray dryers; and dryers combining these types. The heating temperature in this case cannot be generalized because it varies depending on the type of solvent to be removed and the pressure conditions during drying. However, it is usually 5 to 100°C, preferably 10 to 85°C, and more preferably 15 to 70°C, and reduced-pressure drying (vacuum drying) is preferred. Drying can also be performed by filtration using a glass filter or the like, solid-liquid separation by decantation, or solid-liquid separation using a centrifuge or the like. Drying using the above-mentioned various dryers and drying by solid-liquid separation can also be performed in combination.

[0084] As described above, heating for crystallization or the like may be performed. Examples of heating equipment used in this case include a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a baking furnace, a vacuum baking furnace, etc., depending on the scale of the treatment. In addition, various dryers used for drying to remove the solvent can also be used, and the heating equipment for removing the solvent and the heating equipment for crystallization or the like may be shared.

[0085] The heating temperature for crystallization cannot be generalized because it varies depending on the crystal structure to be obtained, but is usually preferably 130° C. or higher, more preferably 135° C. or higher, and even more preferably 140° C. or higher, and although there is no particular upper limit, it is preferably 600° C. or lower, more preferably 550° C. or lower, and even more preferably 500° C. or lower. Heating for crystallization can be carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in vacuum).

[0086] (Melt quenching method) When the melt quenching method is adopted, the apparatus for producing a sulfide solid electrolyte may include at least a reaction device including a heater for reacting the solid electrolyte raw materials, and a quenching device including a quenching tank for quenching the fired product (melted product) fired by the heating device. The sulfide solid electrolyte and remaining solid electrolyte raw materials may adhere to the inside of the reaction device including the heater and the quenching device including the quenching tank.

[0087] The heating device is not particularly limited as long as it can heat the solid electrolyte raw material to a temperature at which it can melt (preferably 400 to 1000°C, more preferably 800 to 900°C), and can be appropriately selected from the heating devices exemplified as heating devices used for heating for crystallization in the mechanical milling method described above. The quenching tank can be a tank that can cool the molten solid electrolyte raw material to a temperature at which it can be quenched (preferably 10°C or less, more preferably 0°C or less), for example, a tank that can hold a refrigerant such as ice or liquid nitrogen.

[0088] (Slurry Method) When a slurry method (including a solution method) is employed, for example, when a solid electrolyte raw material is reacted while being mixed in a solvent (complexing agent) containing a heteroatom, the sulfide solid electrolyte production apparatus may be equipped with a reaction vessel having a stirring blade for mixing the solid electrolyte raw material with the solvent (complexing agent) containing a heteroatom to produce an electrolyte precursor; a heating device for removing the complexing agent from the electrolyte precursor; a heating device for crystallization, etc. When a slurry method (including a solution method) is employed, the electrolyte precursor and remaining solid electrolyte raw material may adhere to the inside of the reaction vessel equipped with the reaction vessel, and the sulfide solid electrolyte, remaining solid electrolyte raw material, and electrolyte precursor may adhere to the inside of the heating device for removing the complexing agent and the heating device for crystallization, etc.

[0089] The reaction equipment may be, for example, a mechanically agitated mixer equipped with an agitating blade inside a reaction vessel. Examples of mechanically agitated mixers include high-speed agitation mixers and double-arm mixers. High-speed agitation mixers are preferably used from the viewpoint of improving the uniformity of the solid electrolyte raw material in a mixture of the solid electrolyte raw material and the solvent (complexing agent) containing a heteroatom, thereby obtaining higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers, and either type of mixer may be used.

[0090] In the above-mentioned reactor, a mixture (slurry) containing the electrolyte precursor, residual complexing agent that does not contribute to the reaction with the solid electrolyte raw material, and other solvents used as needed is obtained. When a slurry method is employed, a dryer may be provided to remove the residual complexing agent and other solvents used as needed from the mixture (slurry). Furthermore, when a slurry method (including a solution method) is employed, a grinding device may be provided to grind and mix the mixture (slurry) obtained in the above-mentioned reactor. The grinding device can be appropriately selected from the various grinders exemplified as grinders that can be used to grind and react the solid electrolyte raw material in the above-mentioned mechanical milling method.

[0091] An amorphous sulfide solid electrolyte is obtained by removing the complexing agent from the electrolyte precursor. The complexing agent can be removed from the electrolyte precursor by heating. The heating device used in this process can be appropriately selected from the various dryers exemplified as dryers that can be used to remove the solvent in the mechanical milling method. From the viewpoint of more efficiently removing the complexing agent from the electrolyte precursor, it is preferable to use a flash dryer. Furthermore, when removing the residual complexing agent and other solvents used as needed from the mixture (slurry), the dryer used to remove the solvent can also be appropriately selected from the various dryers exemplified as dryers that can be used to remove the solvent in the mechanical milling method.

[0092] The heating equipment for crystallization, etc. can be appropriately selected from the various heating equipments exemplified as heating equipment for heating for crystallization, etc. in the mechanical milling method described above. Various dryers used for removing the complexing agent can also be used, and the heating equipment for removing the complexing agent and the heating equipment for crystallization, etc. can be shared. The heating temperature for crystallization, etc. can be appropriately selected from the temperature range exemplified as the heating temperature for heating for crystallization, etc. in the mechanical milling method described above.

[0093] The heating equipment for crystallization or the like may also be used as a heating equipment for obtaining an amorphous sulfide solid electrolyte. In this case, for example, after removing the complexing agent from the electrolyte precursor using a heating equipment for removing the complexing agent, heating may be performed using a heating equipment for crystallization or the like. When the complexing agent cannot be sufficiently removed from the electrolyte precursor using a heating equipment for removing the complexing agent, and the electrolyte precursor remains, a more homogeneous amorphous sulfide solid electrolyte can be obtained by heating using a heating equipment for crystallization or the like. When a crystalline sulfide solid electrolyte is to be obtained, further heating using a heating equipment for crystallization or the like is sufficient. When a heating equipment for crystallization or the like is used to remove the complexing agent from the electrolyte precursor, the removal of the complexing agent and crystallization may be performed using the same heating equipment.

[0094] (Method Using a Pressure-Resistant Container) The reaction of the solid electrolyte raw materials can also be carried out by heat-treating them in a solvent using a pressure-resistant container or while refluxing (hereinafter, this may be referred to as the "method using a pressure-resistant container"). These heat-treatment methods are effective in producing a sulfide solid electrolyte having an argyrodite-type crystal structure, as described below. When this method is employed, the sulfide solid electrolyte production apparatus may include at least a reaction device equipped with a pressure-resistant container for heat-treating the solid electrolyte raw materials in a solvent; a cooling device for refluxing the solvent; and a calcination device for calcining the heat-treated product obtained by the heat treatment. An intermediate (heat-treated product) that can become a sulfide solid electrolyte by calcination in the subsequent calcination device, as well as remaining solid electrolyte raw materials, may adhere to the inside of the reaction device equipped with the pressure-resistant container. Furthermore, the sulfide solid electrolyte, remaining solid electrolyte raw materials, and the intermediate (heat-treated product) may adhere to the inside of the calcination device.

[0095] When the heat treatment is carried out using a pressure vessel, if the heating temperature exceeds the boiling point of the solvent used, it is preferable to use a heating device such as an autoclave. When the heat treatment is carried out while refluxing the solvent, the method is not particularly limited, and for example, a cooling device (e.g., a Dimroth device) that cools the vapor and returns it to the solvent can be used.

[0096] It is preferable to remove the solvent after the heat treatment in the solvent. By performing the heat treatment, a slurry containing the solvent and the heat-treated product is obtained, and by removing the solvent from the slurry, the heat-treated product is obtained. For example, the solvent can be removed by using an appropriate dryer selected from the various dryers exemplified as dryers for removing the solvent in the mechanical milling method.

[0097] The heat-treated product obtained by removing the solvent is preferably calcined. This allows a solid electrolyte, preferably a crystalline solid electrolyte, to be produced. The heating temperature in calcining the heat-treated product may be appropriately selected depending on the composition of the solid electrolyte to be obtained, and is, for example, preferably 300°C or higher, more preferably more than 300°C, even more preferably 320°C or higher, even more preferably 350°C or higher, particularly preferably 380°C or higher, with the upper limit being preferably 470°C or lower, more preferably 460°C or lower, even more preferably 450°C or lower, still more preferably 440°C or lower, particularly preferably 430°C or lower.

[0098] The firing can be carried out using a heating device such as a firing furnace, including a stationary hearth kiln and a rotary kiln, etc. The firing is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum).

[0099] (Other Equipment) The solid electrolyte raw material can be pulverized whether the reaction of the solid electrolyte raw material is carried out by the mechanical milling method, the melt quenching method, the slurry method, or the method using a pressure-resistant container. The solid electrolyte raw material may adhere to the inside of the pulverizer used to pulverize the solid electrolyte raw material. The pulverizer used to pulverize the solid electrolyte raw material can be appropriately selected from the various pulverizers exemplified as the pulverizer used to pulverize the solid electrolyte raw material for reaction in the mechanical milling method. A pin mill is also preferred because it has a short processing time and allows for continuous pulverization operations.

[0100] Whether the reaction of the solid electrolyte raw materials is carried out by the mechanical milling method, the melt quenching method, the slurry method, or a method using a pressure-resistant vessel, the solid electrolyte raw materials can be preliminarily mixed. The solid electrolyte raw materials may adhere to the inside of a mixer used for premixing the solid electrolyte raw materials. Mixers that can be used for premixing can be appropriately selected from the various reaction vessels exemplified as reaction vessels equipped with stirring blades used to mix the solid electrolyte raw materials and the heteroatom-containing solvent (complexing agent) in the slurry method. Mixers of various types, such as a rotating container mixer or a fixed container mixer, as well as a Nauta mixer, which is a conical screw mixer, or an FM mixer, which is a high-speed stirring mixer, can also be used.

[0101] Whether the reaction of the solid electrolyte raw materials is carried out by the mechanical milling method, the melt quenching method, the slurry method, or the method using a pressure vessel, the sulfide solid electrolyte production apparatus may be equipped with a particle size adjustment device such as a grinder or a classifier for particle size adjustment, such as fine particle size adjustment, depending on the application of the sulfide solid electrolyte. The sulfide solid electrolyte, remaining solid electrolyte raw materials, and electrolyte precursor may adhere to the inside of the particle size adjustment device for particle size adjustment. The particle size adjustment device can be appropriately selected from the various grinders exemplified as the grinders that grind the solid electrolyte raw materials to cause reaction in the mechanical milling method.

[0102] When a flash dryer is used as the heating device, particularly when a slurry method (including a solution method) is used, the sulfide solid electrolyte can be separated from the airflow. A preferred example of a separation device for separating the sulfide solid electrolyte is a bag filter. This allows the powder to be easily separated from a fluid containing the heated airflow used in the flash dryer and the powder dried by the flash dryer. The sulfide solid electrolyte, remaining solid electrolyte raw materials, and electrolyte precursor may adhere to the inside of the separation device.

[0103] As the bag filter, commercially available bag filters can be used without any particular restrictions. The bag filter may also have a brushing means, for example, a pulsating counterpressure system or a pulse jet system is preferred, with a pulse jet system being preferred. An induced draft fan may be provided in the line from the exhaust port of the bag filter to forcibly exhaust the gas exhausted from the exhaust port. By exhausting the gas using an induced draft fan or the like, filtration in the bag filter proceeds smoothly, and the slurry can be dried in a shorter time.

[0104] The solid electrolyte raw materials, solvents, etc. used in the sulfide solid electrolyte manufacturing apparatus of the present embodiment will be described below.

[0105] (Solid electrolyte raw material) The solid electrolyte raw material used in the above reaction may be selected depending on the solid electrolyte to be obtained, and preferably includes a solid electrolyte raw material containing at least one atom selected from lithium atoms, phosphorus atoms, and sulfur atoms, and it is preferable to use multiple types of solid electrolyte raw materials. Furthermore, from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte, a solid electrolyte raw material further containing a halogen atom is also preferable. As the raw material used in the sulfide solid electrolyte production apparatus of this embodiment, a material containing multiple types of the above solid electrolyte raw materials (hereinafter sometimes referred to as a "raw material containing material") can be preferably used.

[0106] Examples of the solid electrolyte raw material include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides; raw materials containing at least two atoms selected from the above-mentioned atoms, and fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Representative examples of the raw material include a halogen element such as halogen, phosphorus, sulfur, and the like; and a raw material consisting of one atom selected from the above-mentioned elements.

[0107] Among the above, examples of the solid electrolyte raw material containing lithium atoms, sulfur atoms, and phosphorus atoms include lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0108] Among the above, lithium sulfide, diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides, fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide are preferred. When oxygen atoms are introduced into the solid electrolyte, lithium oxide, lithium hydroxide, and phosphate compounds such as lithium phosphate are preferred.

[0109] Among the above, either a simple halogen or a lithium halide can be preferably used as the solid electrolyte raw material containing a halogen atom, because the use of a solid electrolyte raw material containing a halogen atom can improve the ionic conductivity of the sulfide solid electrolyte.

[0110] As the lithium halide, lithium chloride, lithium bromide, and lithium iodide are more preferred. When attempting to obtain a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure, it is preferable to use at least one of lithium chloride and lithium bromide, and it is more preferable to use lithium chloride and lithium bromide in combination. Furthermore, when attempting to obtain a crystalline sulfide solid electrolyte having a thiolicon region II-type crystal structure, it is preferable to use at least one of lithium bromide and lithium iodide, and it is more preferable to use lithium bromide and lithium iodide in combination.

[0111] The halogen element is chlorine (Cl ２ ), bromine (Br ２ ), iodine (I２ ) is more preferred. When attempting to obtain a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure, it is preferable to use at least one of chlorine and bromine, and it is more preferred to use chlorine and bromine in combination. When attempting to obtain a crystalline sulfide solid electrolyte having a thiolicon region II-type crystal structure, it is preferable to use at least one of bromine and iodine, and it is more preferred to use bromine and iodine in combination.

[0112] Preferred examples of the combination of solid electrolyte raw materials contained in the raw material inclusions include a combination of lithium sulfide, phosphorus sulfide, and lithium halide, a combination of lithium sulfide, phosphorus sulfide, and a simple halogen, and a combination of lithium sulfide, phosphorus sulfide, lithium halide, and a simple halogen. More preferred examples include a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and a simple halogen. Among the above combinations, preferred lithium halides are lithium chloride, lithium bromide, and lithium iodide, and preferred simple halogens are chlorine, bromine, and iodine. As mentioned above, the solid electrolyte raw materials containing halogen atoms can be selected depending on the type of solid electrolyte to be obtained.

[0113] P.S. ４ Li containing structure ３ P.S. ４ can also be used as a solid electrolyte raw material. ３ P.S. ４ In this case, the combination of the solid electrolyte raw materials contained in the raw material contents may be Li ３ P.S. ４ and the lithium halide, Li ３ P.S. ４ and the above-mentioned elemental halogens, Li ３ P.S. ４ and the lithium halide and the elemental halogen.

[0114] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide as solid electrolyte raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity, and the upper limit is preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less. The range is typically preferably 60 to 85 mol%, more preferably 65 to 83 mol%, even more preferably 70 to 80 mol%, and even more preferably 74 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 74 to 78.5 mol%, 74 to 78 mol%, and 74 to 76 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 76 to 83 mol%, 77 to 80 mol%, and 78 to 80 mol% are preferred.

[0115] When the raw material content includes lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as necessary as solid electrolyte raw materials, the content of lithium sulfide and diphosphorus pentasulfide relative to the total is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more, with the upper limit being 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. The range is typically preferably 50 to 100 mol%, more preferably 55 to 90 mol%, even more preferably 60 to 85 mol%, and even more preferably 60 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 65 to 90 mol%, 70 to 85 mol%, and 75 to 83 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 50 to 78 mol%, 55 to 70 mol%, and 55 to 65 mol% are preferred.

[0116] (Solvent) Preferred examples of the solvent used in the reaction include polar solvents such as solvents containing heteroatoms. Polar solvents such as solvents containing heteroatoms are preferably used in the slurry method. Heteroatoms such as nitrogen atoms, oxygen atoms, halogen atoms such as chlorine atoms, and sulfur atoms have a high affinity with lithium atoms and tend to bond with the solid electrolyte raw materials contained in the raw material contents to form complexes (hereinafter also simply referred to as "complexes"). Therefore, as mentioned above, solvents containing heteroatoms can also be called "complexing agents." A solvent (complexing agent) containing a heteroatom forms a complex with the solid electrolyte raw materials, which makes it easier to maintain the uniform dispersion state of the solid electrolyte raw materials, particularly the dispersion state of the halogen atoms, and as a result, it is thought that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0117] Among the above, nitrogen and oxygen atoms are preferred as heteroatoms contained in the complexing agent. Examples of solvents containing nitrogen atoms as heteroatoms include solvents having a group containing a nitrogen atom, such as an amino group, an amide group, a nitro group, or a nitrile group. Solvents having a group containing a nitrogen atom are preferably used in the slurry method (a method for forming a complex), and among these, solvents having an amino group are preferred.

[0118] As the solvent having an amino group, an aliphatic amine is preferred from the viewpoint of obtaining higher ionic conductivity. Examples of the aliphatic amine include ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), tetramethyldiaminopropane (TMPDA), tetraethylethylenediamine, and tetraethyldiaminopropane. Among these aliphatic amines, a polyamine having two or more amino groups is preferred, and a diamine having two amino groups is preferred.

[0119] The solvent having an amino group is preferably a tertiary amine having a tertiary amino group as the amino group, more preferably a tertiary diamine having two tertiary amino groups, even more preferably a tertiary diamine having two tertiary amino groups at both ends, and even more preferably an aliphatic tertiary diamine having tertiary amino groups at both ends. As the aliphatic tertiary diamine, the above-mentioned tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane are preferred, and tetramethylethylenediamine and tetraethylethylenediamine are more preferred.

[0120] Preferred examples of solvents other than those having an amino group include aliphatic nitrile solvents such as acetonitrile, acrylonitrile, propionitrile, chloropropionitrile, isobutyronitrile, tert-butyronitrile, capronitrile, isocapronitrile, malononitrile, and fumaronitrile; alicyclic nitrile solvents such as cyclohexylnitrile; and aromatic nitrile solvents such as benzonitrile and fluorobenzonitrile. These nitrile solvents are preferably used in the above-mentioned reaction of the solid electrolyte raw material in a method using a pressure-resistant vessel, and are more preferably used in combination with a non-polar solvent such as a hydrocarbon solvent described below. In this case, among the above-mentioned nitrile solvents, aliphatic nitrile solvents are preferred, and propionitrile, isobutyronitrile, and isocapronitrile are more preferred.

[0121] Preferred examples of the solvent other than the solvent having an amino group include solvents containing a nitrogen atom, such as dimethylformamide, nitrobenzene, and dimethylacetamide.

[0122] Preferred examples of the complexing agent include ether solvents and ester solvents containing an oxygen atom as a heteroatom, as well as alcohol solvents, aldehyde solvents, and ketone solvents. As the complexing agent containing an oxygen atom, from the viewpoint of obtaining higher ionic conductivity, ether solvents and ester solvents are preferred, and ether solvents are more preferred. Preferred ether solvents include aliphatic ethers such as dimethyl ether, diethyl ether, tert-butyl methyl ether, dimethoxymethane, dimethoxyethane, diethylene glycol dimethyl ether (diglyme), triethylene oxide glycol dimethyl ether (triglyme), diethylene glycol, and triethylene glycol; and alicyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, and dioxane. Among these, alicyclic ethers are more preferred, and tetrahydrofuran is preferred in view of availability and other factors.

[0123] Among the reactions of the above-mentioned solid electrolyte raw materials, in the method using a pressure vessel, aliphatic ethers and alicyclic ethers are preferred, and diethyl ether and tetrahydrofuran are particularly preferred.

[0124] Preferred examples of the ester solvent include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate; and aliphatic esters such as methyl propionate, ethyl propionate, dimethyl oxalate, diethyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, and diethyl succinate.

[0125] Preferred examples of the solvent include alcohol solvents such as ethanol and butanol; aldehyde solvents such as formaldehyde, acetaldehyde and dimethylformamide; and ketone solvents such as acetone and methyl ethyl ketone. When a solution method is employed, it is preferable to use an alcohol solvent. Among solvents having a group containing an oxygen atom, alcohol solvents are preferably used in the solution method.

[0126] Furthermore, as the solvent, a non-polar solvent such as a hydrocarbon solvent can also be used as a solvent other than the above-mentioned solvent containing a hetero atom. Examples of hydrocarbon solvents include saturated or unsaturated aliphatic hydrocarbons such as hexane, hexene, pentane, 2-ethylhexane, heptane, heptene, octane, decane, undecane, dodecane, and tridecane; saturated or unsaturated alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and cyclohexene; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, and tert-butylbenzene. Among these, aromatic hydrocarbon solvents are preferred, and toluene and xylene are more preferably used.

[0127] In the method using the pressure vessel, it is preferable to use a combination of a polar solvent such as the above-mentioned heteroatom-containing solvent (complexing agent) and a non-polar solvent such as a hydrocarbon solvent. In this case, the non-polar solvent is preferably an aromatic hydrocarbon solvent, particularly toluene or ethylbenzene, and the polar solvent is preferably a nitrile solvent, which has the property of forming an azeotrope with an aromatic hydrocarbon solvent such as toluene and is easily removed together with the aromatic hydrocarbon solvent such as toluene.

[0128] (Amorphous Solid Electrolyte) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment becomes either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte depending on the firing conditions. The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment preferably contains lithium atoms, sulfur atoms, and phosphorus atoms, and more preferably further contains halogen atoms, and representative examples thereof include Li, ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５-LiI-LiBr, etc., sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; and solid electrolytes further containing other atoms such as oxygen atoms and silicon atoms, for example, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-P ２ S ５ -Li ２ O-LiI-LiBr, Li ２ S-SiS ２ -P ２ S ５ In order to obtain higher ionic conductivity, a sulfide solid electrolyte such as LiI is preferable. ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ A sulfide solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI-LiBr, is preferred. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0129] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the compounding 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. Further, when bromine and iodine are used in combination as halogen atoms, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine, and iodine is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.02 to 0.25: 0.02 to 0.25, more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.03 to 0.2: 0.03 to 0.2, and even more preferably 1.35 to 1.45: 1.4 to 1.7: 0.3 to 0.45: 0.04 to 0.18: 0.04 to 0.18. By setting the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte having a higher ionic conductivity and a crystal structure described below, particularly a thiolisiconregion II crystal structure or an argyrodite crystal structure.

[0130] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ５０ The average particle size (D) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 5 μm or less, further 3.0 μm or less, 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less. ５０ ) is the particle size at which 50% (volume basis) of the total particle size is reached when the particle sizes are sequentially added together starting from the smallest particle size when an integrated particle size distribution curve is drawn, and the volume distribution refers to an average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device.

[0131] With respect to the metal atoms contained in the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the content of metal atoms constituting the alkali compound contained in the alkaline aqueous solution is less than 15 ppm by mass, and further, 10 ppm by mass or less, 8 ppm by mass or less, 5 ppm by mass or less, 3 ppm by mass or less, 1 ppm by mass or less, or less than 1 ppm by mass. As mentioned above, examples of the metal atoms constituting the alkali compound include alkali metals. The content of metal atoms constituting the alkali compound can be confirmed, for example, by an ICP atomic emission spectrometer.

[0132] Regarding the metal atoms contained in the amorphous sulfide solid electrolyte, the metal atoms constituting the alkali compounds contained in the alkaline aqueous solution are basically not contained unless an alkaline aqueous solution is used to clean the inside of the equipment. In other words, the content of the metal atoms within the above range means that an alkaline aqueous solution is not used to clean the inside of the equipment. As such, the amorphous sulfide solid electrolyte obtained by the production method of this embodiment uses water to clean the inside of the equipment, and therefore the amount of metal atoms constituting the alkali compounds contained in the alkaline aqueous solution entrained in the solid electrolyte can be kept to an extremely small amount, resulting in a sulfide solid electrolyte with excellent performance.

[0133] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and its crystalline structure may be Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P.S. ６ Crystal structure, Li ７ P ３ S １１ Examples of such structures include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0134] Li ４－ｘ Ge １－ｘP ｘ S ４ Thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples of the crystal structure include a crystal structure similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, in that higher ionic conductivity can be obtained. Here, the "thio-LISICON Region II type crystal structure" refers to a crystal structure in which Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ This indicates that the thiolisicon region II type crystal structure has a similar crystal structure to the thiolisicon region II type. As will be described later, the thiolisicon region II type crystal structure and the similar crystal structure have similar diffraction peaks, and are therefore very close to each other. Therefore, it is technically reasonable to treat the "thiolisicon region II type crystal structure" as including the thiolisicon region II type crystal structure and the similar crystal structure.

[0135] Here, the above "Li ４－ｘ Ge １－ｘ P ｘ S ４The notation of the crystal structure "thio-LISICON Region II type" means that the crystal structure was found in the above document to be composed of Li, Ge, P, and S atoms. The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and therefore, is not a "Li ４－ｘ Ge １－ｘ P ｘ S ４ "Li in thio-LISICON Region II type" ４－ｘ Ge １－ｘ P ｘ S ４ However, when the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the same diffraction peak as the above-mentioned "thiolisiconregion II type crystal structure" (including the above-mentioned "similar crystal structure"), it can be said that the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. The same applies to the argyrodite type crystal structure described below.

[0136] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may contain the above-mentioned thiolicon region II type crystal structure or may contain it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the proportion of the target crystal structure among the crystal structures is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains crystalline Li ３ P.S. ４ (β-Li ３ P.S. ４ It is preferable that the main crystal does not contain thiolicon region II crystal structure. Although the above-mentioned main crystal is explained using the thiolicon region II crystal structure as an example, the same applies to other crystal structures.

[0137] In X-ray diffraction measurement using CuKα radiation, Li ３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of thio-LISICON Region II type appear, for example, at 2θ=20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0138] The above Li ７ P.S. ６ A preferred example of the crystalline sulfide solid electrolyte is an argyrodite-type crystal structure having a structural skeleton in which part of P is substituted with Si. The composition formula of the argyrodite-type crystal structure is, for example, the composition formula Li ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６(x is −0.6 to 0.6, y is 0.1 to 0.6) The argyrodite-type crystal structure represented by this composition formula is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0139] The composition formula of the argyrodite-type crystal structure is Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦−0.25x+0.5) is also included. The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The composition formula of the argyrodite-type crystal structure is preferably the composition formula Li ７－ｘ P.S. 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 a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Note that these peak positions may vary within a range of ±0.5°.

[0140] The atomic composition ratios contained in the crystalline sulfide solid electrolyte are those according to the composition formulas corresponding to the various crystal structures, and are preferably within the range of the atomic composition ratios of the amorphous sulfide solid electrolyte. When the atomic composition ratios are within the range, it is easy to form a thiosilicon region II type crystal structure or an argyrodite type crystal structure, among the above crystal structures.

[0141] The content of the metal atoms constituting the alkali compound contained in the crystalline sulfide solid electrolyte is the same as the content of the metal atoms contained in the amorphous sulfide solid electrolyte, and the average particle size is also the same.

[0142] (Solvent Content) When a solvent is used in the reaction of the solid electrolyte raw materials, the content of the solvent contained in the obtained crystalline sulfide solid electrolyte is preferably 0 mass %, i.e., no solvent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte having high ionic conductivity, the content is usually 10 mass % or less, further 8 mass % or less, 5 mass % or less, 3 mass % or less, or 1 mass % or less, and the lower limit is about 0.01 mass % or more.

[0143] [Apparatus for Producing Sulfide Solid Electrolyte] The apparatus for producing a sulfide solid electrolyte of this embodiment is an apparatus for producing a sulfide solid electrolyte that includes a water supply device that supplies water used for cleaning equipment.

[0144] The sulfide solid electrolyte production apparatus of this embodiment is equipped with a water supply device that supplies water used for cleaning the equipment, which allows the interior of the equipment constituting the production apparatus to be cleaned safely and efficiently, thereby enabling maintenance work to be performed promptly. As a result, the downtime of the production apparatus due to maintenance work can be shortened, making it possible to produce a sulfide solid electrolyte with a higher operating rate.

[0145] The sulfide solid electrolyte production apparatus of this embodiment is only required to include the water supply device, and the equipment other than the water supply device for cleaning the equipment may vary depending on the method for producing a sulfide solid electrolyte employed. The equipment that the sulfide solid electrolyte production apparatus of this embodiment can include is as described above in the method for producing a sulfide solid electrolyte of this embodiment.

[0146] (Applications) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment is suitable for use in electrode composites and batteries, particularly lithium ion batteries, and particularly all-solid-state batteries. The sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be used in the positive electrode layer or negative electrode layer of a lithium ion battery, or in the electrolyte layer of an all-solid-state battery in addition to the positive electrode tank and negative electrode tank. Each layer can be manufactured by a known method.

[0147] [Electrode Mixture] The sulfide solid electrolyte obtained by the manufacturing method of this embodiment can be used for an electrode mix, as described above. The electrode mix using the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is an electrode mix containing the solid electrolyte of this embodiment and an electrode active material.

[0148] As the electrode active material, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode mixture is used for a positive electrode or a negative electrode, and as the positive electrode active material and the negative electrode active material, materials conventionally used as these active materials can be used.

[0149] The compounding ratio (mass ratio) of the solid electrolyte to the electrode active material in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40, in order to improve battery performance and in consideration of production efficiency.

[0150] The electrode composite using the sulfide solid electrolyte obtained by the production method of this embodiment may contain, in addition to the sulfide solid electrolyte obtained by the production method of this embodiment and the electrode active material, other components such as a conductive material such as a carbon-based material, a thermoplastic elastomer, a binder such as a resin, etc.

[0151] [Lithium-ion battery] A lithium-ion battery using the sulfide solid electrolyte obtained by the manufacturing method of this embodiment includes at least one of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment described above and an electrode composite containing the sulfide solid electrolyte.

[0152] The lithium ion battery using the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is not particularly limited in its configuration as long as it contains either the sulfide solid electrolyte obtained by the manufacturing method of this embodiment or an electrode composite containing the sulfide solid electrolyte, and for example, a solid electrolyte of another form or an electrode composite containing the solid electrolyte may be used. Furthermore, the configuration of the lithium ion battery may be any configuration of a commonly used lithium ion battery.

[0153] A lithium ion battery using the sulfide solid electrolyte obtained by the manufacturing method of this embodiment preferably includes, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. The positive electrode layer and the negative electrode layer preferably use an electrode mixture using the sulfide solid electrolyte obtained by the manufacturing method of this embodiment, and the electrolyte layer preferably uses the sulfide solid electrolyte obtained by the manufacturing method of this embodiment. A lithium ion battery using a solid electrolyte as the electrolyte layer is also called an all-solid-state battery.

[0154] The battery preferably includes a current collector in addition to the positive electrode layer, the electrolyte layer, and the negative electrode layer, and a known current collector can be used. For example, a layer of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used.

[0155] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0156] (Regarding the Production Apparatus) The production apparatus used in the Examples and Comparative Examples was an apparatus having, in order, a reaction device for mixing and reacting a solid electrolyte raw material with a solvent (complexing agent) having a heteroatom, a pulverizer for mixing and pulverizing a slurry containing the electrolyte precursor and solvent (complexing agent) obtained by the reaction, a heating device equipped with a medium-fluidized dryer for removing the complexing agent from the electrolyte precursor, a separation device for separating the sulfide solid electrolyte obtained by removing the complexing agent from the electrolyte precursor, a heating device for heating the sulfide solid electrolyte separated in the separation device, and a further heating device for crystallization. This production apparatus enables the production of a sulfide solid electrolyte by a slurry method.

[0157] Here, the heating equipment and separation equipment used to remove the complexing agent from the electrolyte precursor were configured as shown in FIG. 1 . The fluidized media dryer, which is the heating equipment shown in FIG. 1 , uses media particles as a medium, fluidizes the media particles in the dryer with a gas, and supplies a slurry containing the electrolyte precursor and a solvent, such as a complexing agent, to be dried into the fluidized bed of media particles, whereupon the slurry is dried. By drying the slurry, the complexing agent is removed from the electrolyte precursor, yielding a sulfide solid electrolyte powder, and the remaining solvent, such as the complexing agent, is exhausted. Also shown in FIG. 1 is a bag filter, which is a separation equipment. The sulfide solid electrolyte powder produced by the fluidized media dryer is separated and recovered using the bag filter, which is also a separation equipment. The recovered powder is heated using a heating equipment to ultimately yield a crystalline sulfide solid electrolyte.

[0158] Example 1 1. Cleaning of the Interior of the Equipment After the sulfide solid electrolyte was produced using the above-mentioned production equipment, the production equipment was shut down. Next, the interior of the fluidized-medium dryer in the production equipment was cleaned. The interior of the fluidized-medium dryer (internal capacity: 100 L) was cleaned by filling the fluidized-medium dryer with water, leaving it to stand for 3 hours, and then draining it. Sulfur-atom-containing materials (mainly electrolyte precursors and amorphous sulfide solid electrolytes) adhered to the interior of the fluidized-medium dryer. The fluid containing the gas generated by filling the fluid with water was supplied to a wet scrubber, a gas-liquid contact device, and the fluid containing the generated gas (hydrogen sulfide) was contacted with an alkaline aqueous solution of sodium hydroxide (sodium hydroxide content: 5% by mass). The hydrogen sulfide content in the exhaust gas from the scrubber was less than 0.1 ppm by volume, confirming that the hydrogen sulfide was recovered by the scrubber. The inside of the fluidized bed dryer was washed with water, and then the inside of the fluidized bed dryer was dried using nitrogen (temperature: 100° C.) for 12 hours.

[0159] 2. Production of sulfide solid electrolyte After cleaning the inside of the equipment as described in 1 above, production of a sulfide solid electrolyte was started. Specifically, the following operations were performed. A 40 L reaction vessel equipped with a stirring blade (anchor blade) was used as the reaction vessel. 25.5 L of cyclohexane and lithium sulfide (Li ２ S) 440g, diphosphorus pentasulfide (P ２ S ５ 709 g of lithium bromide (LiBr), 139 g of lithium iodide (LiI), and 3.3 L of tetramethylethylenediamine (TMEDA), a solvent (complexing agent) having a heteroatom as a solvent, were sequentially added, and the stirring and mixing was continued for 12 days at a stirring rotation speed of 80 rpm. Next, the reaction vessel was connected to a bead mill equipped with a circulation pump ("LME4 (model number)", manufactured by Ashizawa Finetech Co., Ltd., filled with 8.7 kg of 0.5 mm diameter zirconia beads), and the pump flow rate: 2 L / min, bead mill peripheral speed: 12 m / sec. The bead mill was used as a grinder for 4 hours to grind and mix the mixture, and a slurry containing the electrolyte precursor and the solvent was obtained.

[0160] Next, using a heating device equipped with a fluidized bed dryer for removing a complexing agent from the electrolyte precursor and a separation device for separating the sulfide solid electrolyte, having the configuration shown in Figure 1, the gas supply temperature to the fluidized bed dryer was set to 100°C, the supply rate was set to 2.4 m / s (the flow rate at 100°C for a cross section of a fluidized bed of a 98 mm diameter medium (media particles)), and the slurry containing the electrolyte precursor and solvent was supplied so that the temperature of the fluid containing the gas and powder extracted from the top of the fluidized bed dryer was 70°C. Here, ceramic particles with a particle size of 2 mm were used as the medium media particles, and the filling rate of the ceramic particles was 30% by volume with respect to the volume of the fluidized bed dryer. Nitrogen was used as the gas for fluidizing the medium media particles.

[0161] After the operation of the fluidized bed dryer reached a steady state, drying was continued for 1 hour, and the electrolyte precursor powder collected by the bag filter was heated at 110°C under vacuum for 2 hours to obtain an amorphous sulfide solid electrolyte. The amorphous sulfide solid electrolyte was further heated at 180°C under vacuum for 2 hours to obtain a crystalline sulfide solid electrolyte.

[0162] The element contents of the obtained crystalline sulfide solid electrolyte were measured by the standard addition method using an ICP atomic emission spectrometer, and no sodium atoms were detected (exceeding the measurement limit and being less than 1 ppm by mass).

[0163] Example 2 A sulfide solid electrolyte was produced in the same manner as in Example 1, except that a bag filter (internal capacity: 1000 L) was filled with water for cleaning instead of the medium fluidized dryer. The element contents of the obtained crystalline sulfide solid electrolyte were measured by the standard addition method using an ICP atomic emission spectrometer, and no sodium atoms were detected (the content was above the measurement limit and less than 1 ppm by mass).

[0164] Example 3 A sulfide solid electrolyte was produced in the same manner as in Example 2, except that the inside of the equipment (bag filter) was cleaned by spraying water for 1 minute using a spray nozzle (number of spray nozzles: 2, water supply rate: 100 L / min). The element contents of the obtained crystalline sulfide solid electrolyte were measured by the standard addition method using an ICP atomic emission spectrometer, and no sodium atoms were detected (the content was above the measurement limit and less than 1 ppm by mass).

[0165] Comparative Example 1 A sulfide solid electrolyte was produced in the same manner as in Example 1, except that the interior of the fluidized medium dryer was filled with an aqueous sodium hydroxide solution (sodium hydroxide content: 1% by mass), the aqueous sodium hydroxide solution was discharged, and then the interior was filled with water, and after allowing to stand for 3 hours, the water was discharged. When the element content of the obtained crystalline sulfide solid electrolyte was measured by the standard addition method using an ICP atomic emission spectrometer, sodium atoms were detected and the content was 15 ppm by mass.

[0166] From the results of the above Examples and Comparative Examples, it was confirmed that the equipment cleaning method of this embodiment allows safe and efficient cleaning of the inside of the equipment constituting the sulfide solid electrolyte production apparatus. Furthermore, it was also confirmed that the sulfide solid electrolyte production method of this embodiment, which employs the equipment cleaning method of this embodiment, allows the inside of the equipment to be cleaned safely and efficiently, allowing maintenance work to be started more quickly. It was also confirmed that the obtained sulfide solid electrolyte has an extremely low content of metal atoms constituting the alkaline compounds contained in the alkaline aqueous solution, resulting in a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity.

[0167] Furthermore, it was confirmed that a production apparatus equipped with a water supply device for supplying water used for cleaning equipment according to this embodiment allows the interior of the equipment to be cleaned safely and efficiently, thereby enabling maintenance work to be started more quickly. Therefore, it was also confirmed that the sulfide solid electrolyte obtained using the production apparatus according to this embodiment has an extremely low content of metal atoms constituting the alkaline compounds contained in the alkaline aqueous solution, and as a result, a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity can be obtained.

[0168] The equipment cleaning method of this embodiment is suitable for use in an apparatus for producing a sulfide solid electrolyte. Furthermore, the sulfide solid electrolyte obtained by the production method of this embodiment and the sulfide solid electrolyte obtained using the production apparatus of this embodiment have high ionic conductivity, and are therefore suitable for use as a solid electrolyte or electrode composite in lithium ion batteries, particularly lithium ion batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones, and particularly all-solid-state batteries.

Claims

1. A method for cleaning equipment constituting a sulfide solid electrolyte manufacturing apparatus, the method comprising: cleaning sulfur atom-containing substances adhering to the inside of the equipment with water; and contacting a fluid containing gas generated by the cleaning with an alkaline aqueous solution.

2. The method for cleaning equipment according to claim 1, wherein the sulfur atom-containing substance is at least one substance selected from the group consisting of a solid electrolyte raw material containing sulfur atoms, an electrolyte precursor, and a sulfide solid electrolyte.

3. The method for cleaning equipment according to claim 1 or 2, wherein the cleaning is carried out by filling the inside of the equipment with water and then draining the water.

4. The method for cleaning equipment according to any one of claims 1 to 3, wherein the cleaning is carried out by spray cleaning with the water.

5. A method for cleaning equipment according to any one of claims 1 to 4, wherein the contacting is carried out by supplying an inert gas to the interior of the equipment and bringing the generated gas and a fluid containing the inert gas into contact with the alkaline aqueous solution.

6. The method for cleaning equipment according to any one of claims 1 to 5, wherein the contacting is carried out using a gas-liquid contactor.

7. The method for cleaning equipment according to any one of claims 1 to 6, wherein the cleaning is carried out without using an alkaline aqueous solution.

8. A method for cleaning equipment according to any one of claims 1 to 7, wherein the metal ion content of the water used for the cleaning is 1000 mass ppm or less.

9. The method for cleaning equipment according to any one of claims 1 to 8, wherein the water used for the cleaning has an alkali metal ion content of 1,000 mass ppm or less.

10. A method for cleaning equipment according to any one of claims 1 to 9, wherein the amount of alkaline compound contained in the alkaline aqueous solution supplied is 2.5 molar parts or more per 1 molar part of hydrogen sulfide supplied in the generated gas.

11. The method for cleaning equipment according to any one of claims 1 to 10, wherein the alkaline aqueous solution is an aqueous sodium hydroxide solution.

12. A method for producing a sulfide solid electrolyte, comprising cleaning sulfur atom-containing substances adhering to the inside of equipment constituting a sulfide solid electrolyte production apparatus by the equipment cleaning method recited in any one of claims 1 to 11, and then using the sulfide solid electrolyte production apparatus.

13. The method for producing a sulfide solid electrolyte according to claim 12, wherein the content of metal atoms constituting the alkaline compound contained in the alkaline aqueous solution contained in the sulfide solid electrolyte is less than 1 ppm by mass.

14. A sulfide solid electrolyte manufacturing apparatus equipped with a water supply device for supplying water used for cleaning the equipment.

15. The sulfide solid electrolyte manufacturing apparatus according to claim 14, further comprising an inert gas supply device for supplying an inert gas to the device.

16. The sulfide solid electrolyte manufacturing apparatus according to claim 14 or 15, further comprising a gas-liquid contactor for bringing a fluid containing gas generated by cleaning the equipment into contact with an alkaline aqueous solution.

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