Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
  • H01B1/10—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances sulfides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/22—Alkali metal sulfides or polysulfides
  • C01B17/24—Preparation by reduction
  • C01B17/26—Preparation by reduction with carbon
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/22—Alkali metal sulfides or polysulfides
  • C01B17/24—Preparation by reduction
  • C01B17/28—Preparation by reduction with reducing gases
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0065—Solid electrolytes
  • H01M2300/0068—Solid electrolytes inorganic
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a method for producing lithium sulfide.
• Patent Document 1 describes a method including a micronization step of adjusting a powder containing lithium sulfate into fine particles having a specific particle size and a reduction step of reducing the fine particles with carbon black to obtain lithium sulfide. ing.
• Patent Document 2 describes a step of reducing lithium sulfate to produce lithium sulfide by contacting a mixture containing lithium sulfate and graphite powder with a carbon molded body while heating the mixture, and the generated lithium sulfide is used as the carbon molded body.
• a method including a step of separating from is described.
• both the carbon material and the carbon molded product are used at the same time as a reducing agent for lithium sulfate.
• Examples of the reducing agent used in producing lithium sulfide include the carbon materials described in Patent Documents 1 and 2.
• a reducing gas may be used as the reducing agent.
• a method for obtaining high-purity lithium sulfide for example, a method of sufficiently reducing lithium sulfate using a large amount of reducing agent can be considered.
• a large amount of carbon material is used as the reducing agent, lithium carbonate is by-produced as an impurity, and as a result, high-purity lithium sulfide cannot be obtained.
• an object of the present invention is to provide a method capable of producing high-purity lithium sulfide.
• the present inventor has found that high-purity lithium sulfide can be produced by using a substance containing carbon and a reducing gas in combination as a reducing agent. ..
• the present invention is based on the above findings, and a raw material containing a lithium (Li) element and a sulfur (S) element is reduced with a reducing agent containing a carbon (C) element to obtain an intermediate.
• the present invention provides a method for producing lithium sulfide.
• the present invention also comprises a step of reducing a raw material containing a lithium (Li) element and a sulfur (S) element with a reducing agent containing carbon (C) and a reducing gas to obtain lithium sulfide. Is to provide.
• the present invention comprises the step A of obtaining lithium sulfide and Step B to obtain a raw material composition by mixing the lithium sulfide, diphosphorus pentasulfide, and lithium halide.
• the step C of firing the raw material composition is provided.
• the step A is the first step of reducing a raw material containing a lithium (Li) element and a sulfur (S) element with a reducing agent containing a carbon (C) element to obtain an intermediate, and the intermediate product.
• the present invention provides a method for producing a solid electrolyte, comprising a second step of reducing lithium sulfide with a reducing gas to obtain lithium sulfide.
• the present invention according to the method of manufacturing lithium sulfide (Li 2 S).
• a material containing a lithium (Li) element and a sulfur (S) element is used as a raw material for producing lithium sulfide.
• An intermediate is obtained by reducing this raw material (this step is also referred to as “first step” below), and then the intermediate is reduced (this step is also referred to as “second step” below). ) By doing so, the desired lithium sulfide is obtained.
• Preferred examples of the raw material used in the first step include compounds containing a lithium (Li) element and a sulfur (S) element.
• Examples of such compounds include lithium sulfate (Li 2 SO 4 ), lithium sulfite (Li 2 SO 3 ), lithium thiosulfate (Li 2 S 2 O 3 ) and the like.
• Li 2 SO 4 lithium sulfate
• Li 2 SO 3 lithium sulfite
• Li 2 S 2 O 3 lithium thiosulfate
• Lithium sulfate is generally subjected to the first step in a solid state such as powder or granules.
• Lithium sulfate is generally a hydrous salt, but in the present invention, the hydrous salt of lithium sulfate may be used as it is, or the hydrous salt of lithium sulfate may be dehydrated and used in the state of anhydrous salt.
• the above-mentioned raw material is reduced with a reducing agent to obtain a target intermediate of lithium sulfide.
• the reducing agent used in this step contains an element of carbon (C) from the viewpoint that high-purity lithium sulfate can be easily obtained.
• the "reducing agent containing a carbon (C) element” is a substance having a reducing power capable of reducing the above-mentioned raw materials and containing a carbon (C) element as a constituent element.
• the reducing agent containing a carbon (C) element is not particularly limited as long as it is a substance generally used as a carbon-based reducing agent, and may be a gas, a liquid, or a solid. ..
• the reducing agent may be any reducing agent that can be a source of carbon, and may contain non-carbon atoms. Examples of such reducing agents include organic compounds such as monohydric alcohols, polyhydric alcohols and reducing sugars such as glucose. Other examples include solid carbonaceous materials such as coal, coke, graphite, carbon black, fullerenes, carbon tubes, charcoal, carbide, and elemental carbon and its allotropes. Graphite is a typical example of elemental carbon and its allotropes.
• charcoal such as charcoal, bamboo charcoal, activated carbon, or carbon black
• activated carbon may be powdered activated carbon or granular activated carbon.
• the reducing agent containing a carbon element one of the above-mentioned materials may be used, or two or more of them may be used in combination.
• the shape of the reducing agent containing a carbon element is not particularly limited, and may be, for example, fibrous, powdery or granular, or powdery.
• the average particle size of the powdery reducing agent may be, for example, 1000 ⁇ m or less, 300 ⁇ m or less, or 150 ⁇ m or less.
• the average particle size of the reducing agent may be, for example, 0.1 ⁇ m or more, 1 ⁇ m or more, or 10 ⁇ m or more.
• the smaller the average particle size of the reducing agent the larger the contact area when mixed with the raw material, so that the reduction can be performed more efficiently.
• the average particle diameter here means the volume cumulative particle diameter D 50 in the cumulative volume 50% by volume by laser diffraction scattering particle size distribution measuring method.
• the first step is preferably a step of mixing the raw material and the reducing agent and reducing the raw material with the reducing agent.
• the reducing agent is a solid
• the reaction between the reducing agent and the above-mentioned raw material is a solid phase reaction. Therefore, the raw material can be efficiently reduced by being subjected to the reduction reaction in a state of being well mixed with each other. It is preferable because it can be used.
• the mixer used for mixing for example, a mixer that mixes by moving the container itself filled with the raw material to be mixed and the reducing agent may be used.
• both are mixed by rotating a rotating body having a plate shape, a screw shape, a ribbon shape, a cylinder shape, a disk shape, or any other shape, which is installed in a container filled with the raw material and the reducing agent.
• You may use a mixer to be used.
• a mixer may be used that fills the media, applies force to the media, and mixes the two by the motion of the media.
• a gas such as air may be used (so-called dry type).
• a liquid such as water or an organic solvent may be used (so-called wet type).
• the raw material and the reducing agent may be mixed under vacuum.
• a liquid used as the dispersion medium, a liquid that does not dissolve the raw material may be used, or a liquid that dissolves the raw material may be used.
• a liquid used as the dispersion medium, it may be mixed and then dried to remove the liquid.
• the first step is preferably a step of crushing at least one of the raw material and the reducing agent and then reducing the mixture.
• "Crushing at least one of the raw material and the reducing agent” means that only the raw material may be crushed or only the reducing agent may be crushed. In particular, it is preferable to pulverize both the raw material and the reducing agent. The reason is that the contact area between the raw material and the reducing agent can be made larger, so that the raw material can be efficiently reduced.
• both the raw material and the reducing agent are pulverized, the raw material and the reducing agent may be pulverized separately, or a mixture of the raw material and the reducing agent may be pulverized. In particular, it is preferable to adopt the latter because the process is simplified, it is economically advantageous, and it can be reduced more efficiently.
• Examples of the method for pulverizing at least one of the raw material and the reducing agent include wet pulverization and dry pulverization.
• the dispersion medium used in the wet pulverization is not particularly limited, and is preferably water, for example. It is economically preferable to use water as the dispersion medium.
• the raw material is water-soluble, for example, the raw material and the reducing agent are mixed and wet-ground to obtain a suspension in which the reducing agent is suspended in a raw material solution in which at least a part of the raw material is dissolved. ..
• the turbid liquid to which the dispersion medium is added it is preferable to dry the turbid liquid to which the dispersion medium is added in order to remove the dispersion medium as needed.
• a raw material and a reducing agent are mixed and wet-ground, the raw material is deposited on the surface of the reducing agent by drying after the wet grinding, and the raw material adheres around the reducing agent so as to cover the reducing agent. The resulting mixture is obtained.
• the raw material and the reducing agent are in closer contact with each other as compared with the case where the raw material and the powder of the reducing agent are simply mixed, which is a more preferable state for the solid phase reaction.
• both the mixing step and the crushing step are performed in a wet manner, it is economical to provide the drying step after performing both steps continuously or simultaneously in a wet manner because the drying step can be performed only in a single step. Is preferable.
• the reduction reaction may be carried out under non-heating or under heating depending on the type of the raw material and the reducing agent.
• the temperature inside the system is preferably set to 700 ° C. or higher and 850 ° C. or lower, and is set to 720 ° C. or higher and 830 ° C. or lower as the temperature condition from the viewpoint of efficiently carrying out the reduction reaction. It is more preferable to set the temperature at 750 ° C. or higher and 800 ° C. or lower.
• the heating time is preferably set to 0.5 hours or more and 6 hours or less, and more preferably 1 hour or more and 3 hours or less, from the viewpoint of efficiently performing the reduction reaction.
• the atmosphere at which the reducing reaction is carried out may be a reducing atmosphere or a non-reducing atmosphere.
• the first step is performed in a non-reducing atmosphere.
• the reducing atmosphere include a hydrogen gas atmosphere and a hydrogen gas atmosphere diluted with an inert gas.
• examples of the non-reducing atmosphere include an inert gas atmosphere such as a nitrogen gas atmosphere and an argon gas atmosphere.
• the concentration of the reducing gas and the raw material and the gas are appropriately adjusted so that the reducing agent containing the carbon (C) element does not remain after the reaction is completed in the first step. It is preferable to adjust the reaction temperature, the reaction time, and the like.
• the amount of the reducing agent used is preferably determined in relation to the amount of the above-mentioned raw materials used.
• the amount of the reducing agent may be less than or equal to the amount consumed substantially without excess or deficiency in the reaction in which all the raw materials are reduced to lithium sulfide (hereinafter referred to as "substantial equivalent").
• the reduction reaction of lithium sulfate can be represented by the following formula (1).
• Li 2 SO 4 + 2C ⁇ Li 2 S + 2CO 2 (1)
• reduction of 1 mole of lithium sulfate, to produce one mole of lithium sulfide (Li 2 S) is 2 moles of carbon alone is required, one equivalent of reduction with 2 molar be.
• Another way of looking at it is that when comparing the simple substance of carbon, which is the raw material, with the oxygen (O) element in carbon dioxide, which is the product, 2 mol of oxygen (O) element is compared with 1 mol of carbon (C) element. It can also be consumed.
• C / O2 the ratio of the amount of the reducing agent used to the amount of a certain raw material
• C / O2 the ratio of the amount of the reducing agent used to the amount of a certain raw material
• C / O2 the equivalent ratio represented by the formula (1).
• the “substantial equivalent” in the above is not equivalent to "C / O2 being 1" for the reason described later.
• the reaction product of the reduction is not limited to carbon dioxide, and depending on the conditions, carbon monoxide may be produced as shown in the following formula (2). ..
• Li 2 SO 4 + 4C ⁇ Li 2 S + 4CO (2) The carbon monoxide produced by the formula (2) may be discharged to the outside of the reaction system as it is, or may be further subjected to a reduction reaction as described by the formula (3). Li 2 SO 4 + 4CO ⁇ Li 2 S + 4CO 2 (3) If the equation (2) and the equation (3) occur consecutively, it can be said that the reaction of the equation (1) has occurred. In fact, the present inventor considers that the reactions of the formulas (1), (2) and (3) occur at the same time. Further, since at least a part of the produced carbon monoxide is discharged to the outside of the reaction system without being consumed by the reduction reaction, even if the amounts of the raw material and the reducing agent are adjusted so that the C / O2 becomes 1.
• the amount of reducing agent in that case is less than the substantial equivalent.
• the range of preferable C / O2 to be substantially equivalent or less is 0.8 or more and 1.3 or less, more preferably 0.9 or more and 1.2 or less, and 1.0 or more and 1.1. The following is more preferable.
• Making the amount of the reducing agent used as described above has the following advantages. That is, when the raw material is converted to the target lithium sulfide by a reduction reaction, it is advantageous to use a reducing agent in an amount equal to or more than a substantial equivalent in order to convert a larger amount of the raw material into lithium sulfide. be. However, if a reducing agent in an amount equal to or more than a substantial amount is used, all the raw materials are reduced, but the unreacted reducing agent remains in the product and a large amount of lithium carbonate is by-produced. ..
• the presence of the residual reducing agent and lithium carbonate in the product contributes to impairing the lithium ion conductivity of the sulfide solid electrolyte produced from lithium sulfide as a raw material.
• the raw material is reduced using a carbon-containing reducing agent, it is extremely difficult to produce only lithium sulfide without the by-product of lithium carbonate.
• the ratio of the amount of the reducing agent to the amount of the raw material is set to be substantially equivalent or less, thereby suppressing excessive by-production of lithium carbonate.
• the amount of the reducing agent to a substantial equivalent or less, excessive by-production of lithium carbonate can be suppressed, but unreacted (that is, unreduced) raw materials may remain in the reaction system. Therefore, in the present invention, in the second step described later, the raw material remaining in the reaction system is reduced, and lithium carbonate (if present in the reaction system) is also decomposed to produce high-purity lithium sulfide. I am trying to get it.
• This decomposition reaction of lithium carbonate can be expressed by the following formula (4). Li 2 CO 3 + H 2 ⁇ Li 2 O + CO + H 2 O (4)
• the substance existing in the system when the first step is completed that is, the intermediate obtained in the first step.
• the ratio of I C for I B (I C / I B ) is preferably 0.03 or more and 0.09 or less.
• the value of I A / I B is further preferably 0.05 or less.
• the value of I A / I B is most preferably zero.
• the value of I C / I B are further preferably 0.03 or more 0.08 or less.
• the first step is preferably carried out by placing the raw material and the reducing agent in a container that is inert to the reduction reaction.
• a container that is inert to the reduction reaction.
• examples of such a container include an alumina saggar.
• An intermediate is obtained by the reduction reaction in the first step.
• This intermediate is usually a mixture of unreacted raw materials, the desired product, lithium sulfide, and by-products.
• By-products vary depending on the type of raw material. If the raw material is, for example, lithium sulphate, the by-product is typically the lithium carbonate described above.
• the substance (the above-mentioned intermediate) existing in the reaction system is attached to the second step.
• an additional step may be performed between the first step and the second step. Examples of this additional step include a step of pulverizing the intermediate obtained in the first step. Since the reaction generated in the second step is an air-solid reaction between the intermediate which is a solid and the reducing gas, the contact between the intermediate and the reducing gas is promoted by adding the pulverization step, and the contact is efficiently performed. The reaction can proceed.
• the substance existing in the reaction system after the completion of the first step is reduced by using a reducing gas.
• the reducing gas include hydrogen gas and hydrogen gas diluted with an inert gas.
• the second step is preferably performed in the absence of the reducing agent used in the first step. That is, when the second step is performed, it is preferable that the reducing agent used in the first step is not present in the reaction system.
• the pressure of the reducing gas in the reaction system may be atmospheric pressure, or may be a pressure below or above atmospheric pressure. Generally, satisfactory results can be obtained by circulating the reducing gas in the reaction system under atmospheric pressure.
• the reduction reaction in the second step may be carried out under non-heating or under heating depending on the type of the reducing gas.
• the temperature inside the system is preferably set to 830 ° C. or higher and 930 ° C. or lower, and is set to 830 ° C. or higher and 900 ° C. or lower, as a temperature condition from the viewpoint of efficiently carrying out the reduction reaction. It is more preferable to set the temperature at 830 ° C. or higher and 870 ° C. or lower.
• the heating time is preferably set to 1 hour or more and 12 hours or less, more preferably 2 hours or more and 8 hours or less, and 3 hours or more and 6 hours or less, from the viewpoint of efficiently performing the reduction reaction. It is more preferable to set as follows.
• the second step may be performed at the same time as the first step, or may be performed after the first step.
• the substance existing in the reaction system after the completion of the first step that is, the intermediate obtained in the first step is reduced to further produce lithium sulfide.
• lithium sulfate which is an unreacted raw material contained in the intermediate
• lithium carbonate which is a by-product
• the two can be appropriately combined with respect to the conventional techniques in which lithium sulfide could not be successfully produced by the single use of the reducing gas and the single use of the carbon-based reducing agent. Therefore, it became possible for the first time to easily produce high-purity lithium sulfide.
• a carbon-based reducing agent is used in the first step and a reducing gas is used in the second step.
• the order is reversed and the reducing gas is used in the first step.
• the present inventor has confirmed that the desired effect cannot be obtained even if a carbon-based reducing agent is used in the second step.
• the substance existing in the system when the second step is completed, that is, the final product, lithium sulfide is X-ray diffractometer.
• the ratio of I C for the above-mentioned I B is preferably made 0.02 or less.
• the ratio of I D for I B is preferably 0.05 or less.
• the value of I C / I B is more preferably 0.01 or less.
• the value of I C / I B is most preferably zero.
• the value of I D / I B are further preferably 0.03 or less.
• the value of I D / I B is most preferably zero.
• the second step is preferably carried out by placing the intermediate obtained in the first step in a container that is inert to the reducing gas.
• a container that is inert to the reducing gas. Examples of such a container include an alumina saggar.
• the desired lithium sulfide can be obtained.
• This lithium sulfide is of high purity with a low content of impurities.
• Lithium oxide (Li 2 O) is mentioned as a main impurity.
• Lithium oxide is produced by the reduction of lithium carbonate in the second step.
• the lithium sulfide obtained after the completion of the second step can be applied to the third step.
• a reaction is carried out to convert lithium oxide contained in the lithium sulfide obtained in the second step into lithium sulfide.
• lithium oxide which is an impurity contained in lithium sulfide, is sulfurized to generate lithium sulfide.
• the sulfur-containing gas used in the third step for example, hydrogen sulfide and (H 2 S) gas, a sulfur (S) gas. These gases may be used alone or in combination of two or more. These gases may be used as they are, or may be diluted with a noble gas before use.
• the pressure of the sulfur-containing gas in the reaction system may be atmospheric pressure, or may be a pressure below or above atmospheric pressure. In general, sulfurization can be successfully performed by circulating a sulfur-containing gas in the reaction system under atmospheric pressure.
• the temperature in the system is preferably set to 200 ° C. or higher and 1000 ° C. or lower, and more preferably 300 ° C. or higher and 900 ° C. or lower, from the viewpoint of efficiently sulphurizing lithium oxide. It is more preferable to set the temperature to 400 ° C. or higher and 800 ° C. or lower.
• the heating time is preferably set to 15 minutes or more and 6 hours or less, more preferably 30 minutes or more and 4 hours or less, and 1 hour or more and 3 hours or less, from the viewpoint of efficiently performing the sulfurization reaction. It is more preferable to set as follows.
• the third step from the viewpoint of further increasing the purity of the target product, lithium sulfide, when the substance existing in the system is measured by an X-ray diffractometer at the time when the third step is completed, the substance is thereby measured.
• the ratio of I C for the above-mentioned I B (I C / I B ) it is preferred to carry out the third step such that 0.02.
• the ratio of I D for I B (I D / I It is preferable to perform the second step so that B) is 0.05 or less.
• the value of I C / I B is more preferably 0.01 or less.
• the value of I C / I B is most preferably zero.
• the value of I D / I B is 0.03 or less, preferably among others 0.02 or less, and particularly preferably 0.01 or less.
• the value of I D / I B is most preferably zero.
• lithium sulfide can also be obtained by reducing a raw material containing a lithium (Li) element and a sulfur (S) element with a reducing agent containing a carbon (C) element and a reducing gas.
• the types of the raw material, the reducing agent containing the carbon (C) element, and the reducing gas are the same as those described above.
• the pressure of the reducing gas is also the same as described above.
• the charging ratio of the raw material and the reducing agent containing the carbon (C) element is the same as that described above.
• the temperature condition in the system at the time of reduction is preferably set to 830 ° C. or higher and 870 ° C. or lower, and more preferably 840 ° C. or higher and 860 ° C. or lower, from the viewpoint of efficiently performing the reduction reaction of the raw material.
• the heating time is preferably set to 1 hour or more and 12 hours or less, more preferably 2 hours or more and 8 hours or less, and 3 hours or more and 6 hours or less, from the viewpoint of efficiently performing the reduction reaction. It is more preferable to set as follows.
• the desired high-purity lithium sulfide can also be obtained by performing reduction under the above conditions.
• the purity of the obtained lithium sulfide, particularly the amount of lithium oxide which is an impurity it is superior to performing the above-mentioned first step and the second step separately than this step.
• this lithium sulfide may be subjected to the sulfurization step which is the third step.
• the sulfurization step which is the third step.
• the lithium sulfide thus obtained is preferably used as a raw material for a solid electrolyte.
• the method for producing the solid electrolyte of the present invention includes a step A for obtaining lithium sulfide, a step B for mixing the lithium sulfide, diphosphorus pentasulfide, and lithium halide to obtain a raw material composition, and the raw material. It comprises the step C of firing the composition.
• the step A is the first step of reducing a raw material containing a lithium (Li) element and a sulfur (S) element with a reducing agent containing a carbon (C) element to obtain an intermediate, and the intermediate product.
• the present invention comprises a second step of reducing lithium sulfide with a reducing gas to obtain lithium sulfide.
• a second step of reducing lithium sulfide with a reducing gas to obtain lithium sulfide will be described, but since the step A can be the same as the above-mentioned method for producing lithium sulfide, the description here is omitted.
• the lithium halide used in the step B may be one kind or two or more kinds.
• Examples of lithium halide include lithium chloride (LiCl) and lithium bromide (LiBr).
• Examples of the mixing in step B include mechanical milling.
• Examples of the mechanical milling include a vibration mill, a ball mill, a turbo mill, a mechanical fusion, a disc mill, and the like, and a ball mill is preferable.
• the conditions of the ball mill are not particularly limited as long as the desired raw material composition can be obtained, but for example, the base rotation speed is preferably 200 rpm or more, particularly preferably 300 rpm or more, and 500 rpm or less, particularly 400 rpm or less. Is preferable.
• the processing time of the ball mill can be appropriately adjusted within, for example, 1 hour or more and 100 hours or less.
• the firing in the step C is performed under conditions where a desired solid electrolyte can be obtained. Specifically, it is preferable that the conditions are such that a solid electrolyte containing a crystal phase having an argylodite-type crystal structure can be obtained. From this point of view, it is preferable to fire in an atmosphere of hydrogen sulfide gas, for example.
• the firing temperature is, for example, preferably 300 ° C. or higher, particularly preferably 400 ° C. or higher, and preferably 700 ° C. or lower, particularly 600 ° C. or lower.
• the firing time can be appropriately adjusted according to the firing temperature, and is preferably 1 hour or more and 10 hours or less, particularly preferably 2 hours or more and 6 hours or less.
• the solid electrolyte obtained by the present invention has a halogen (X) element content (halogen (X) element) with respect to the phosphorus (P) element content from the viewpoint of having good lithium ion conductivity.
• the ratio of content / content of phosphorus (P) element) is preferably 0.50 or more and 2.1 or less, more preferably 0.80 or more and 2.0 or less, still more preferably 1.2 or more in terms of molar ratio. It is 1.8 or less.
• solid electrolyte composition formula Li a PS b represented by X c (wherein, X is at least one kind of halogen element , A is 3.0 or more and 6.5 or less, b is 3.5 or more and 5.5 or less, and c is 0.50 or more and 3.0 or less).
• X is at least one kind of halogen element
• A is 3.0 or more and 6.5 or less
• b is 3.5 or more and 5.5 or less
• c 0.50 or more and 3.0 or less.
• Example 1 Li 2 SO 4 ⁇ H 2 O powder was used as a raw material. Activated carbon powder was used as a solid reducing agent containing carbon. The amount of Li 2 SO 4 ⁇ H 2 O used was 86.26 g, and the amount of activated carbon used was 13.74 g. Therefore, the ratio of C / O2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O is 85%. there were.
• Two polyamide pots (volume 500 ml) were prepared, and 43.13 g and 6.87 g of Li 2 SO 4 ⁇ H 2 O and activated carbon were put into each.
• 125 g of pure water and 600 g of ZrO 2 beads (diameter 5 mm) were placed in each pot, and the pot lid was closed.
• the two pots were shaken with a paint shaker for 5 hours, and the mixed powder in the pot was pulverized and mixed. After pulverization and mixing, the slurry and beads were separated using a sieve having an opening of 1 mm, and then the slurry was placed in a 1 L reaction vessel with a jacket made of SUS and heated and dried while stirring.
• the obtained mixed powder was placed in a stainless steel container, and this container was placed in a vacuum dryer, and Li 2 SO 4 ⁇ H 2 O in the mixed powder was dehydrated in a vacuum at 200 ° C. 30.00 g of the above-mentioned mixed powder was filled in an alumina saggar having an internal size of 40 mm in length, 130 mm in width and 24 mm in depth and having an internal volume of 100 ml, and installed inside the core tube of a tubular furnace. While flowing argon gas through the core tube, the temperature was raised to 800 ° C. at a heating rate of 300 ° C./hour, and the mixture was heated as it was in an argon atmosphere for 2 hours.
• the furnace temperature was lowered to room temperature at a temperature lowering rate of 300 ° C./hour, and the intermediate was taken out from the furnace.
• Sampling a portion of the resulting intermediate product, after grinding in an agate mortar was measured by powder X-ray diffraction apparatus, the value of I A / I B and I C / I B in the X-ray diffraction pattern, the following table It became as shown in 1.
• the powder X-ray diffractometer a SmartLab manufactured by Rigaku Co., Ltd. was used. CuK ⁇ 1 line was used as a radiation source.
• ⁇ Second step> The rest of the intermediate material obtained in the first step was placed inside the core tube of the tube furnace while being kept in the above-mentioned saggar. While passing a mixed gas of hydrogen and nitrogen (hydrogen concentration 3.5 vol%) through the core tube, the temperature was raised to 850 ° C. at a heating rate of 300 ° C./hour, and the mixture was heated as it was in the mixed gas atmosphere for 4 hours. .. With the mixed gas flowing, the furnace temperature was lowered to room temperature at a temperature lowering rate of 300 ° C./hour, and lithium sulfide, which was the target product, was taken out from the furnace.
• a mixed gas of hydrogen and nitrogen hydrogen concentration 3.5 vol%
• the resulting withdrawn portion of lithium sulfide, pulverized in an agate mortar was measured by powder X-ray diffraction apparatus, the value of I C / I B and I D / I B in the X-ray diffraction pattern, the following table It became as shown in 1 and 2. From the removal of the target object from the furnace, the extraction of a part of the target object, the crushing of the target object, and the X-ray diffraction measurement of the target object with the powder X-ray diffractometer, N without exposing to the atmosphere. 2 We went in a gas atmosphere.
• Example 2 In the first step of Example 1, C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O. The ratio of / O2 was changed to 95%. Other than that, lithium sulfide was obtained in the same manner as in Example 1.
• Example 3 In the first step of Example 1, C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O. The ratio of / O2 was changed to 105%. Other than that, lithium sulfide was obtained in the same manner as in Example 1.
• Example 4 In the first step of Example 1, C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O. The ratio of / O2 was changed to 125%. Other than that, lithium sulfide was obtained in the same manner as in Example 1.
• Example 5 In the first step of Example 1, C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O. The ratio of / O2 was changed to 125%. Further, the heating temperature in the first step was changed to 700 ° C. Lithium sulfide was obtained in the same manner as in Example 1 except for them.
• Example 6 In the first step of Example 1, C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O. The ratio of / O2 was changed to 125%. Further, the heating temperature in the second step was changed to 900 ° C. Lithium sulfide was obtained in the same manner as in Example 1 except for them.
• Example 7 This embodiment is an example in which the third step is performed after the completion of the second step.
• C is the molar ratio of the carbon (C) element contained in the activated carbon to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O.
• the ratio of / O2 was changed to 125%.
• the third step was performed.
• lithium sulfide was obtained in the same manner as in Example 1.
• the lithium sulfide obtained in the second step was installed inside the core tube of the tube furnace with the lithium sulfide obtained in the second step still in the above-mentioned saggar.
• Example 8 This embodiment is an example in which the first step and the second step are performed at the same time.
• the ratio of C / O2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O was set to 105%. .. 30.00 g of mixed powder was filled in an alumina saggar having an internal size of 40 mm in length, 130 mm in width and 24 mm in depth and having an internal volume of 100 ml, and installed inside the core tube of a tubular furnace.
• Example 1 While passing a mixed gas of hydrogen and nitrogen (hydrogen concentration 3.5 vol%) through the core tube, the temperature was raised to 850 ° C. at a heating rate of 300 ° C./hour, and the mixture was heated as it was in the mixed gas atmosphere for 4 hours. .. With the mixed gas flowing, the furnace temperature was lowered to room temperature at a temperature lowering rate of 300 ° C./hour, and lithium sulfide, which was the target product, was taken out from the furnace. Other than those, the same as in Example 1.
• This comparative example corresponds to an example of Patent Document 1 (Japanese Unexamined Patent Publication No. 2013-227180).
• Li 2 SO 4 ⁇ H 2 O powder was used as a raw material.
• Activated carbon powder was used as a solid reducing agent containing carbon.
• the amount of Li 2 SO 4 ⁇ H 2 O used was 58.48 g, and the amount of activated carbon used was 11.52 g. Therefore, the ratio of C / O2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O is 105%. there were.
• Two polyamide pots (volume 500 ml) were prepared, and 29.24 g and 5.76 g of Li 2 SO 4 ⁇ H 2 O and activated carbon were put into each.
• the pot was shaken with a paint shaker for 5 hours to grind and mix the mixed powder in the pot. After pulverization and mixing, the slurry and beads were separated using a sieve having an opening of 1 mm, and then the slurry was dried by a dryer.
• the obtained mixed powder was placed in a stainless steel container, and this container was placed in a vacuum dryer, and Li 2 SO 4 ⁇ H 2 O in the mixed powder was dehydrated in a vacuum at 200 ° C. 30.00 g of the above-mentioned mixed powder was filled in an alumina saggar having an internal size of 40 mm in length, 130 mm in width and 24 mm in depth and having an internal volume of 100 ml, and installed inside the core tube of a tubular furnace. While flowing argon gas through the core tube, the temperature was raised to 830 ° C. at a heating rate of 300 ° C./hour, and the mixture was heated as it was in an argon atmosphere for 3 hours.
• the furnace temperature was lowered to room temperature at a temperature lowering rate of 300 ° C./hour, and the target product was taken out from the furnace.
• Sampling a portion of the resulting target product, after grinding in an agate mortar was measured by powder X-ray diffraction apparatus, the value of I C / I B and I D / I B in the X-ray diffraction pattern, the following table It became as shown in 1 and 2. From the removal of the target object from the furnace, the extraction of a part of the target object, the crushing of the target object, and the X-ray diffraction measurement of the target object with the powder X-ray diffractometer, N without exposing to the atmosphere. 2 We went in a gas atmosphere.
• Comparative Example 2 In Comparative Example 1, the ratio of C / O 2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O was calculated. Changed to 125%. Other than that, it was the same as in Comparative Example 1.
• This comparative example corresponds to an example of Patent Document 2 (Japanese Patent Laid-Open No. 2015-74567).
• Li 2 SO 4 ⁇ H 2 O powder was used as a raw material.
• Activated carbon powder was used as a solid reducing agent containing carbon.
• the amount of Li 2 SO 4 ⁇ H 2 O used was 61.36 g, and the amount of activated carbon used was 8.64 g. Therefore, the ratio of C / O2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O is 75%. there were.
• Two polyamide pots (volume 500 ml) were prepared, and 30.68 g and 4.32 g of Li 2 SO 4 ⁇ H 2 O and activated carbon were put into each.
• the pot was shaken with a paint shaker for 5 hours to grind and mix the mixed powder in the pot. After pulverization and mixing, the slurry and beads were separated using a sieve having an opening of 1 mm, and then the slurry was dried by a dryer.
• the obtained mixed powder was placed in a stainless steel container, and this container was placed in a vacuum dryer, and Li 2 SO 4 ⁇ H 2 O in the mixed powder was dehydrated in a vacuum at 200 ° C. 30.00 g of the above-mentioned mixed powder was filled in a graphite saggar having an internal size of 40 mm in length, 130 mm in width and 24 mm in depth and having an internal volume of 100 ml, and installed inside the core tube of a tubular furnace. While flowing argon gas through the core tube, the temperature was raised to 860 ° C. at a heating rate of 300 ° C./hour, and the mixture was heated as it was in an argon atmosphere for 3 hours.
• the furnace temperature was lowered to room temperature at a temperature lowering rate of 300 ° C./hour, and the target product was taken out from the furnace.
• Sampling a portion of the resulting target product, after grinding in an agate mortar was measured by powder X-ray diffraction apparatus, the value of I C / I B and I D / I B in the X-ray diffraction pattern, the following table It became as shown in 1. From the removal of the target object from the furnace, the extraction of a part of the target object, the crushing of the target object, and the X-ray diffraction measurement of the target object with the powder X-ray diffractometer, N without exposing to the atmosphere. 2 We went in a gas atmosphere.
• Comparative Example 4 In Comparative Example 3, the ratio of C / O2, which is the molar ratio of the carbon (C) element contained in the activated carbon, to 2 mol of the oxygen (O) element contained in the sulfate ion constituting Li 2 SO 4 ⁇ H 2 O was calculated. Changed to 85%. Other than that, it was the same as in Comparative Example 3.
• the sulfide solid electrolyte was uniaxially pressure-molded at a pressure of 200 MPa and further subjected to cold isotropic pressure (CIP) at a pressure of 200 MPa to prepare pellets having a diameter of 10 mm and a thickness of 2 to 5 mm.
• CIP cold isotropic pressure
• the lithium ion conductivity was measured by the AC impedance method at 25 ° C. All of these operations were performed in a glove box replaced with a well-dried argon gas (dew point -60 ° C or lower).
• the lithium sulfide obtained in each example contains less impurities lithium carbonate and lithium sulfate than the lithium sulfide of the comparative example. Due to this, the sulfide solid electrolyte using lithium sulfide as a raw material obtained in each example has a higher lithium ion conductivity than the sulfide solid electrolyte using lithium sulfide as a raw material in the comparative example. I understand.
• high-purity lithium sulfide can be produced.

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