Manufacturing method of metal sulfide and metal sulfide

Abstract

To provide a manufacturing method etc., of metal sulfide that does not require high temperature and can be manufactured under atmospheric environment.SOLUTION: A manufacturing method of metal sulfide comprises an electrolysis step of bringing an anode (11) comprising a metal element M and a cathode (12) into contact with an electrolytic solution (20) comprising a sulfur source and energizing the anode (11) and the cathode (12) to precipitate metal sulfide comprising the metal element M at least one of in the electrolytic solution (20) and on the surface of the cathode (12).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a metal sulfide and to a metal sulfide. [Background technology]

[0002] In recent years, metal sulfides such as tin sulfide, zinc sulfide, molybdenum sulfide, and tungsten sulfide have attracted attention as raw materials for producing sulfide-based solid electrolytes used in sulfide-based all-solid-state batteries.

[0003] Patent Document 1 describes a method for producing tin disulfide, which is characterized by firing a mixture of metallic tin and sulfur in an open system in an atmosphere of a mixed gas of inert gas and sulfur gas at a temperature of not less than the boiling point of sulfur and not more than 700°C.

[0004] Patent Document 2 describes a method for producing a metal sulfide, which comprises placing a metal component and sulfur in a conductive container and applying a direct current pulse current to the container in a non-oxidizing atmosphere to heat and react the raw materials, thereby reacting the metal component with sulfur. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-84401 [Patent Document 2] International Publication No. 2009 / 028326 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional methods described in Patent Documents 1 and 2 require high temperatures for the reactants or the reaction vessel, and a specific gas atmosphere, which poses problems in terms of production costs and environmental impact.

[0007] An object of one aspect of the present invention is to provide a method for producing a metal sulfide that does not require heating of the reactants or the reaction vessel, etc., and that can be produced in an air atmosphere. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, a method for producing a metal sulfide according to one embodiment of the present invention includes an electrolysis step in which an anode containing a metal element M and a cathode are brought into contact with an electrolytic solution containing a sulfur source, and a current is applied to deposit a metal sulfide containing the metal element M in the electrolytic solution or on the surface of the cathode. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a method for producing a metal sulfide that does not require heating the reactants or reaction vessel to high temperatures and that can be produced in an air atmosphere. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an electrolysis device used to carry out a method for producing a metal sulfide according to one embodiment of the present invention. [Figure 2] FIG. 1 shows TG curves obtained from the precipitate of Example 6 and SnS2 of Reference Example 1. [Figure 3] FIG. 1 shows TG curves obtained from the precipitate of Example 7 and ZnS of Reference Example 2. [Figure 4] FIG. 1 shows X-ray diffraction patterns of the precipitates of Examples 1 and 6 and SnS2 of Reference Example 1. [Figure 5] FIG. 1 is a diagram showing an X-ray diffraction pattern of the precipitate of Example 7. [Figure 6] FIG. 1 shows Raman spectra of the precipitates of Examples 1 and 6 and SnS2 of Reference Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Method for producing metal sulfide] An embodiment of the present invention will be described in detail below. A method for producing a metal sulfide according to an embodiment of the present invention includes an electrolysis step and may further include a washing step. In this specification, a method for producing a metal sulfide according to an embodiment of the present invention may be simply referred to as "the present production method." Furthermore, in this specification, when multiple values ​​are selectively described for at least one of the upper and lower limits of a numerical range, these can be arbitrarily combined to form a numerical range.

[0012] (Electrolysis process) The electrolysis step is a step in which an anode containing a metal element M and a cathode are brought into contact with an electrolyte containing a sulfur source and a current is passed through them, thereby precipitating a metal sulfide containing the metal element M in the electrolyte or on the surface of the cathode or both.

[0013] Fig. 1 is a schematic diagram showing an example of an electrolysis apparatus 1 used to carry out the present production method. In Fig. 1, "+" indicates an anode and "-" indicates a cathode. As shown in Fig. 1, the electrolysis apparatus 1 includes an electrolytic cell 10, an anode 11, a cathode 12, a power source 13, and a stirrer 14.

[0014] The electrolytic cell 10 is a component having an internal space capable of storing the electrolytic solution 20, and may be, for example, a rectangular box. The wall members, such as the side walls and bottom wall, that constitute the internal space of the electrolytic cell 10 are preferably made of an insulating material. Examples of such materials include synthetic resin and glass. Examples of synthetic resins include polyolefin, polycarbonate, acrylic, vinyl chloride, and ABS (Acrylonitrile-Butadiene-Styrene) resin. The material of the wall members of the electrolytic cell 10 may be one of these materials, or a mixture of two or more of these materials. Furthermore, the material of the wall members of the electrolytic cell 10 is preferably a transparent resin or glass, from the viewpoint of making it easy to check the progress of the electrolysis process.

[0015] The electrolytic solution 20 is a liquid to which a current is applied in the electrolysis step and contains a sulfur source. The sulfur source may be elemental sulfur, a sulfur compound, or a source containing both elemental sulfur and a sulfur compound. The sulfur source may or may not be dissolved in the solvent of the electrolytic solution 20. The sulfur source may be added to the electrolytic solution 20 in advance in an amount required for the electrolysis step, or may be additionally added to the electrolytic solution 20 during the electrolysis step.

[0016] Elemental sulfur is a sulfur molecule composed only of sulfur atoms, such as octasulfur (S8 sulfur). When the electrolyte solution 20 contains elemental sulfur as a sulfur source, the reaction between sulfur and the metal element M during electrolysis can proceed efficiently. Sulfur compounds are compounds containing sulfur atoms, such as sulfur monochloride, sulfur dichloride, sulfur tetrachloride, hydrogen sulfide, and carbon disulfide.

[0017] The content of the sulfur source in the electrolytic solution 20 is not particularly limited, but may be, for example, 1% by mass or more, 2% by mass or more, 4% by mass or more, 6% by mass or more, or 8% by mass or more, from the viewpoint of efficiently proceeding with the reaction with the metal element M. Furthermore, the content of the sulfur source in the electrolytic solution 20 may be 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0018] The electrolytic solution 20 may further contain an electrolyte. The electrolyte is not particularly limited as long as it is a substance that dissolves in the solvent of the electrolytic solution 20 and dissociates into cations and anions, and salts, acids, or alkalis commonly used in the fields of electrochemistry or batteries can be used. The salt is not particularly limited, and examples that can be used include inorganic ion salts such as alkali metal salts and alkaline earth metal salts; ammonium salts; imidazolium salts; pyridinium salts; phosphonium salts; oxazolium salts; guanidinium salts; and thiazolium salts. Specific examples of salts include halogen ions, SCN ions, and the like. - , ClO4 - , BF4 - , CF3SO3 - , (CF3SO2)2N- , (C2F5SO2)2N - , PF6 - , AsF6 - , CH3COO - , CH3(C6H4)SO3 - , and (C2F5SO2)3C - Examples of the counter anion include Li salts, Na salts, K salts, ammonium salts, imidazolium salts, pyridinium salts, phosphonium salts, oxazolium salts, guanidinium salts, and thiazolium salts, each having a counter anion selected from the group consisting of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMITFB), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBF4). By including an electrolyte in the electrolytic solution 20, the conductivity of the electrolytic solution 20 is increased, allowing the reaction between sulfur and the metal element M to proceed efficiently by electrolysis.

[0019] The content of the electrolyte in the electrolytic solution 20 is not particularly limited, but may be, for example, 0.01 mol / L or more, 0.02 mol / L or more, 0.05 mol / L or more, or 0.10 mol / L or more from the viewpoint of the efficiency of applying current to the electrolytic solution 20. Furthermore, the content of the electrolyte in the electrolytic solution 20 may be 20.00 mol / L or less, 10.00 mol / L or less, 5.00 mol / L or less, or 2.00 mol / L or less.

[0020] The solvent of the electrolytic solution 20 is not particularly limited, but preferably contains an organic solvent, and more preferably is an organic solvent. The organic solvent is not particularly limited, and organic solvents commonly used in the fields of electrochemistry or batteries can be used. Examples of organic solvents include acetic anhydride, methanol, ethanol, tetrahydrofuran, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, butylene carbonate, propylene carbonate, nitromethane, acetonitrile, acetylacetone, N-methylformamide, N,N-dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, dimethoxyethane, diethoxyfuran, γ-butyrolactone, γ-valerolactone, sulfolane, propionitrile, butyronitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionamide, methylpyrrolidinone, 2-(N-methyl)-2-pyrrolidinone, dimethyl sulfoxide, dioxolane, diisopropyl ether, methylpropanol ... Examples of suitable organic solvents include hexane, toluene, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyl dimethyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, tris(trifluoromethyl)phosphate, tris(pentafluoroethyl)phosphate, triphenyl phosphate, tricresyl phosphate, 2-ethylhexyl phosphate, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphortriamide, 4-methyl-2-pentanone, dioctyl phthalate, dioctyl sebacate, ethylene glycol, diethylene glycol, and triethylene glycol monobutyl ether. Among these, the organic solvent is preferably an alcohol such as methanol or ethanol, and more preferably methanol. If the solvent of the electrolytic solution 20 is an organic solvent, the possibility of unintended reactions such as electrolysis of the solvent occurring when electricity is applied to the electrolytic solution 20 can be reduced, and metal sulfides can be efficiently precipitated.

[0021] In the electrolysis step, the temperature of the electrolytic solution 20 is not particularly limited, and the electrolysis step can be performed at room temperature, for example. In this specification, room temperature is assumed to be 15°C or higher and 30°C or lower. That is, according to the present production method, there is no need to particularly heat or cool the electrolytic solution 20 or the like in the electrolysis step. The electrolytic solution 20 may be heated or cooled. The temperature of the electrolytic solution 20 in the electrolysis step may be, for example, 0°C or higher and 50°C or lower, 5°C or higher and 45°C or lower, or 10°C or higher and 40°C or lower. When the electrolytic solution 20 is heated or cooled in the electrolysis step, a temperature adjustment device such as a heater may be in contact with the electrolytic solution 20, or the electrolytic cell 10 may have a function for adjusting the temperature of the electrolytic solution 20.

[0022] Anode 11 contains metal element M and is electrically connected to the positive terminal of power source 13. Cathode 12 is electrically connected to the negative terminal of power source 13. Anode 11 and cathode 12 are conductive and are each in contact with electrolytic solution 20. Anode 11 and cathode 12 pass a current supplied from power source 13 through electrolytic solution 20.

[0023] The metal element M contained in the anode 11 is a metal element that is sulfurized during the deposition of the metal sulfide obtained by this production method. The metal element M may be any metal element that reacts with sulfur, such as a typical metal element or a transition metal element. Examples of typical metal elements include alkali metal elements, alkaline earth metal elements, zinc group elements, and earth metal elements. The transition metal element may be any of the first transition metal elements, second transition metal elements, third transition metal elements, and fourth transition metal elements. The metal element M may be one of these metal elements, or may contain two or more of them.

[0024] Among these, the metal element M is preferably at least one selected from the group consisting of Sn (tin), Zn (zinc), W (tungsten), and Mo (molybdenum). When the metal element M is such an element, metal sulfides such as tin sulfide, zinc sulfide, tungsten sulfide, or molybdenum sulfide, which are in high industrial demand, can be produced by this production method.

[0025] Although the amount of metal element M contained in anode 11 is not particularly limited, for example, anode 11 preferably contains metal element M as a main component. The main component of anode 11 refers to the component that is contained in anode 11 in the largest amount.

[0026] Specifically, anode 11 preferably contains 50 mass% or more, more preferably 60 mass% or more, more preferably 70 mass% or more, more preferably 80 mass% or more, more preferably 90 mass% or more, more preferably 95 mass% or more, and more preferably 99 mass% or more of metal element M. With this configuration, metal sulfide can be efficiently deposited by the present production method.

[0027] The material of the anode 11 preferably includes, as a material containing the metal element M, for example, a metal (single element) made of the metal element M, an alloy containing the metal element M, or a compound containing the metal element M, more preferably a metal (single element) made of the metal element M or an alloy containing the metal element M, and even more preferably a metal (single element) made of the metal element M.

[0028] The material of the cathode 12 is not particularly limited as long as it is conductive, but is preferably a metal or carbon. When the cathode 12 is a metal, the metal element contained therein may be at least one of the metal elements M described above. When the cathode 12 is a metal, the metal element contained therein may be the same metal element as the metal element M contained in the anode 11, or may be a different metal element. When the cathode 12 is a metal, it may contain, for example, Pt or Ni as a main component.

[0029] The shapes of the anode 11 and the cathode 12 are not particularly limited, and examples thereof include plate-like, rod-like, cylindrical, mesh-like, spherical, irregularly shaped, and wire-like. Preferably, the anode 11 and the cathode 12 are both plate-like and disposed in the electrolytic cell 10 so that one surface of the anode 11 and one surface of the cathode 12 face each other. If the anode 11 is plate-like, the contact area of ​​the anode 11 with the electrolyte 20 can be easily increased, and therefore, the ionization of the metal element M and the elution into the electrolyte 20 can easily proceed. Furthermore, if the cathode 12 is plate-like, the precipitation of metal sulfide on the surface of the cathode 12 can easily proceed.

[0030] The anode 11 and the cathode 12 are in contact with the electrolytic solution 20. The manner of contact is not particularly limited, but for example, it is preferable that at least a portion of each of the anode 11 and the cathode 12 is immersed in the electrolytic solution 20. Furthermore, at least one of the anode 11 and the cathode 12 may be in contact with only the liquid surface of the electrolytic solution 20. From the viewpoint of the efficiency of passing current through the electrolytic solution 20 and the efficiency of depositing metal sulfide, it is preferable that the contact area of ​​the anode 11 and the cathode 12 with the electrolytic solution 20 is large. Therefore, it is preferable that both the anode 11 and the cathode 12 are immersed in the electrolytic solution 20 and in contact with it.

[0031] As the electrolysis process progresses, the volume of the anode 11 decreases as the metal element M is consumed. The contact portion of such anode 11 with the electrolytic solution 20 may be changed as the electrolysis process progresses. For example, the shape of the anode 11 may be a metal (single element) made of the metal element M that is long in the vertical direction and has a plate or rod shape, and at the start of the electrolysis process, only a lower portion of the anode 11 is brought into contact with the electrolytic solution 20. Then, as the electrolysis process progresses, the anode 11 may be moved so as to be pressed down into the electrolytic solution 20, thereby changing the contact portion of the anode 11 with the electrolytic solution 20.

[0032] Alternatively, for example, a portion of the anode 11 may be formed into a mesh-like cage shape using a metal that does not react in the electrolysis process, and a plurality of spherical metal (simple substance) elements made of the metal element M may be placed in the cage as part of the anode 11. At the start of the electrolysis process, these plurality of spherical metal (simple substance) elements made of the metal element M are subjected to a dissolution (oxidation) reaction. As the electrolysis process progresses, additional spherical metal (simple substance) elements made of the metal element M may be added to the cage, thereby changing the portion of the anode 11 that comes into contact with the electrolytic solution 20.

[0033] These methods allow the anode 11 consumed in the electrolysis process to be continuously supplied. Furthermore, when the anode 11 is continuously supplied in this manner, the sulfur source contained in the electrolytic solution 20 may also be additionally supplied to the electrolytic solution 20 during the electrolysis process. These methods allow the precipitation of metal sulfides to proceed continuously without interrupting the electrolysis process, without requiring operations such as replacing the anode 11, the cathode 12, and the electrolytic solution 20. Furthermore, even when the precipitate deposited in the electrolysis process is recovered from the surface of the cathode 12 and / or the electrolytic solution 20, the interruption time of the electrolysis process can be minimized, allowing intermittent precipitation of metal sulfides.

[0034] Power supply 13 is electrically connected to anode 11 and cathode 12, and supplies a current to anode 11 and cathode 12 for passing electricity through electrolytic solution 20. Power supply 13 is preferably a constant current power supply or a constant voltage power supply that can apply a predetermined amount of current or voltage to electrolytic solution 20.

[0035] In the electrolysis step, the voltage for applying current to the electrolytic solution 20 is not particularly limited. However, from the viewpoint of efficiently depositing metal sulfides, it is preferable to set the power source 13 so that the potential difference between the anode 11 and the cathode 12 is 0.5 V or more and 3.0 V or less. In other words, in the electrolysis step, it is preferable for the power source 13 to apply a voltage of 0.5 V or more and 3.0 V or less to the electrolytic solution 20. The potential difference between the anode 11 and the cathode 12 may be 1.0 V or more, 1.2 V or more, or 1.5 V or more. Furthermore, the potential difference between the anode 11 and the cathode 12 may be 2.5 V or less, or 2.0 V or less.

[0036] In order to apply such a voltage to the electrolyte 20, the current density of the current flowing through the electrolyte 20 relative to the electrode area of ​​the anode 11 and the cathode 12 is 1 mA / cm 2 It may be more than 2 mA / cm 2 It may be more than 5mA / cm 2 The current density of the current flowing through the electrolytic solution 20 relative to the electrode area of ​​the anode 11 and the cathode 12 is 1000 mA / cm 2 or more. 2 may be less than 800mA / cm 2 may be less than 500mA / cm 2 It may be the following:

[0037] In the electrolysis step, the time for which current is applied to the electrolytic solution 20 is not particularly limited. From the viewpoint of obtaining a predetermined amount of precipitate, the time may be, for example, 0.5 hours or more, preferably 1 hour or more, and more preferably 3 hours or more. When the anode 11 and the sulfur source are continuously supplied during the electrolysis step, the time for which current is applied to the electrolytic solution 20 may be as long as the supply continues. When the anode 11 and / or the sulfur source are not continuously supplied during the electrolysis step, applying current for an excessive time reduces the reaction efficiency due to the loss of the anode 11 and / or the sulfur source. In this case, the time for which current is applied may be, for example, 48 hours or less, preferably 36 hours or less, and more preferably 24 hours or less.

[0038] The stirrer 14 is a member for stirring the electrolyte solution 20. The stirrer 14 may be, for example, a magnetic stirrer that rotates by magnetic force to stir the electrolyte solution 20. The stirring of the electrolyte solution 20 may be performed by means other than the stirrer 14; for example, the electrolyte solution 20 may be stirred by a stirring blade (stirring blade) or a stirring rod, or the electrolyte solution 20 may be stirred together with the electrolytic cell 10 by a shaker, a rotator, or the like. Furthermore, stirring the electrolyte solution 20 is not essential.

[0039] In the electrolysis step, the electrolytic solution 20 may be energized while an inert gas is flowing into the electrolytic solution 20. Examples of the inert gas include argon gas, nitrogen gas, and helium gas. By flowing the inert gas into the electrolytic solution 20, it is possible to reduce deterioration such as oxidation of the deposited metal sulfide.

[0040] The inflow rate of the inert gas into the electrolyte 20 is not particularly limited, and may be, for example, 20 mL / (min·L) or more, 40 mL / (min·L) or more, or 60 mL / (min·L) or more relative to the volume of the electrolyte 20. The inflow rate may also be 400 mL / (min·L) or less, 300 mL / (min·L) or less, 200 mL / (min·L) or less, or 160 mL / (min·L) or less.

[0041] The mechanism by which metal sulfides are produced in this production method is not particularly limited. For example, it is thought that the following reaction occurs in the electrolysis device 1, causing metal sulfides to precipitate in the electrolytic solution 20 and / or on the surface of the cathode 12.

[0042] First, at the anode 11, ionization due to oxidation of the metal element M occurs as shown in the following formula (1). - represents the number of electrons, and n represents the valence when the metal element M is ionized to form a cation. M → M n+ + ne - (1)

[0043] At the cathode 12, the type of sulfur source, sulfide ions S in the electrolyte 20 2- The concentration of cations of ionized metal element M (M n+ ) and sulfide ions S 2- When the reaction represented by the following formula (2) proceeds on the surface of the cathode 12, metal sulfide MS 2 is formed on at least one of the surface of the cathode 12 and the electrolytic solution 20. n / 2 It is thought that precipitates. M n+ + (n / 2)S + ne - → MS n / 2 (2) S + 2e - → S 2- (3)

[0044] In the electrolytic solution 20, the sulfur source dissolves in the solvent and the reaction of the above formula (3) occurs, whereby sulfide ions S 2- It is believed that when the reaction shown in the following formula (4) proceeds in such an electrolytic solution 20, metal sulfide MS n / 2 It is thought that precipitates. 2M n+ + nS 2- → 2MS n / 2 (4)

[0045] Thus, according to one embodiment of the present invention, metal sulfides can be produced by precipitating them through an electrolytic process. As described above, conventional methods for producing metal sulfides require high temperatures for reactants such as a sulfur source or a reaction vessel. Furthermore, it is essential to carry out the reaction in a specific atmosphere, such as a mixed gas atmosphere of an inert gas and a sulfur gas or a non-acidic atmosphere. This poses challenges in terms of production cost and energy efficiency, and there is also room for improvement in terms of environmental impact.

[0046] A method for producing metal sulfides according to one embodiment of the present invention has the advantageous effect of enabling production of metal sulfides at room temperature in an air atmosphere, for example, without requiring high temperatures and a specific atmosphere as in conventional methods. Another advantageous effect is that metal sulfides can be produced by directly using electrical energy in the electrolysis process, without the need to convert electrical energy into other energy as in conventional methods. Another advantageous effect is that metal sulfides can be produced by directly using electrical energy generated from renewable energy, for example, in the electrolysis process. These effects contribute to the achievement of, for example, Goal 7.3 "Improve global energy efficiency" and Goal 13.3 "Climate change mitigation" of the Sustainable Development Goals (SDGs) proposed by the United Nations.

[0047] (Cleaning process) The washing step is a step of washing the metal sulfide after the electrolysis step. Washing the metal sulfide refers to bringing the metal sulfide into contact with a washing solution used for washing the metal sulfide, and then separating the metal sulfide from the washing solution. The contact of the metal sulfide with the washing solution may be performed by immersing the metal sulfide in the washing solution, by pouring the washing solution over the metal sulfide, or by other methods.

[0048] Furthermore, the separation of the cleaning solution and the metal sulfide may be performed by a method of separating the metal sulfide from the cleaning solution by filtration, or by a method of individually recovering the metal sulfide from the cleaning solution using a spatula, tweezers, or the like, or by other methods.

[0049] By such a washing step, impurities contained in the metal sulfide precipitated in the electrolysis step can be dissolved in the washing liquid, and the metal sulfide can be separated from the impurities, thereby improving the purity of the metal sulfide.

[0050] The cleaning solution may be, for example, carbon disulfide. By using carbon disulfide as the cleaning solution, impurities derived from the compound used as the sulfur source in the electrolysis step can be efficiently removed, and the risk of an unintended reaction occurring between the metal sulfide and the cleaning solution can be reduced.

[0051] Before and / or after the washing step, an additional washing step may be carried out as necessary, in which the metal sulfide is washed with water, an acidic aqueous solution, an alkaline aqueous solution, an organic solvent, or the like. In the additional washing step, washing is preferably carried out with a substance different from the washing solution used in the washing step. For example, when carbon disulfide is used as the washing solution in the washing step and an organic solvent is used in the additional washing step, it is preferable that the organic solvent be an organic solvent other than carbon disulfide.

[0052] The cleaning step may include, before cleaning with carbon disulfide, a step of recovering precipitates produced in the electrolysis step from at least one of the surface of cathode 12 and electrolytic solution 20. The recovery method may be a method of separating the electrolytic solution 20 and the like from the precipitates by filtration, a method of recovering the precipitates individually with a spatula or tweezers, or another method.

[0053] The washing step is preferably carried out from the viewpoint of improving the purity of the metal sulfide, but is not essential.

[0054] (Metal sulfides produced) The metal sulfide produced by this production method may be crystalline or amorphous. Here, "amorphous metal sulfide" preferably means that the metal sulfide is amorphous as a whole or substantially amorphous, but it is sufficient that at least a portion of the produced metal sulfide is amorphous.

[0055] The metal sulfide is preferably amorphous, because amorphous metal sulfides are more suitable for use as a raw material for a sulfide-based solid electrolyte used in a sulfide-based all-solid-state battery, for example, in terms of improving the ionic conductivity of the sulfide-based solid electrolyte, compared to crystalline metal sulfides.

[0056] When a metal sulfide is amorphous, the peak at the minimum 2θ in the X-ray diffraction pattern when 2θ is 10° or more is broader than when the metal sulfide is crystalline. Therefore, it is preferable that the half-width of the peak at the minimum 2θ in the X-ray diffraction pattern when 2θ is 10° or more is 0.5° or more. Such a metal sulfide can be said to be amorphous or substantially amorphous.

[0057] The X-ray diffraction pattern of the metal sulfide may be obtained by performing X-ray diffraction measurement using an X-ray diffractometer in the range of 2θ from 5 to 80°.

[0058] The chemical structure of metal sulfides is "MS n / 2 While metal sulfides are identified as "crystalline," as mentioned above, it is known that their physical properties vary greatly depending on their crystalline state. It is common technical knowledge that the state of metal sulfides varies greatly depending on the manufacturing method. The above-mentioned definition of the crystalline state based on the X-ray diffraction pattern is useful as an indicator of whether a metal sulfide is amorphous or not, but it cannot be said that it alone completely identifies the state of the metal sulfide. Completely identifying the state of a metal sulfide is either impossible or, if not, is almost impractical, since it would be necessary to identify it based on an extremely large number of parameters obtained by various measurement methods.

[0059] 〔summary〕 A method for producing a metal sulfide according to a first aspect of the present invention includes an electrolysis step of contacting an anode containing a metal element M and a cathode with an electrolytic solution containing a sulfur source, and applying a current to the anode and cathode to deposit a metal sulfide containing the metal element M in the electrolytic solution or on the surface of the cathode.

[0060] A second aspect of the present invention relates to the method for producing a metal sulfide according to the first aspect, and the metal element M may be one or more selected from the group consisting of Sn, Zn, W, and Mo.

[0061] A third aspect of the present invention relates to the method for producing a metal sulfide according to the first or second aspect, wherein the anode may contain the metal element M in an amount of 50 mass % or more.

[0062] A fourth aspect of the present invention relates to the method for producing a metal sulfide according to any one of the first to third aspects, wherein the sulfur source may contain elemental sulfur.

[0063] A fifth aspect of the present invention relates to the method for producing a metal sulfide according to any one of the first to fourth aspects, wherein the electrolytic solution further contains an electrolyte.

[0064] A sixth aspect of the present invention relates to the method for producing a metal sulfide according to any one of the first to fifth aspects, wherein the electrolytic solution may contain an organic solvent as a solvent.

[0065] A seventh aspect of the present invention relates to the method for producing a metal sulfide according to any one of the first to sixth aspects, and further relates to a step of electrolyzing the metal sulfide, in which a potential difference between the anode and the cathode is set to 0.5 V or more and 3.0 V or less.

[0066] A method for producing a metal sulfide according to an eighth aspect of the present invention is the method for producing a metal sulfide according to any one of the first to seventh aspects, and may further include a washing step of washing the metal sulfide after the electrolysis step.

[0067] A metal sulfide according to a ninth aspect of the present invention is obtained by the method for producing a metal sulfide according to the first aspect, and has an X-ray diffraction pattern in which the half-width of the peak at the minimum 2θ is 0.5° or more when 2θ is 10° or more.

[0068] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0069] An embodiment of the present invention will now be described.

[0070] 〔material〕 As the electrolytic cell 10, a 50 mL Glass Cell with PTFE stopper (ESYNTH003-1EA, manufactured by SIGMA ALDRICH) or a 1 L beaker (only in Example 6) was used.

[0071] The anode 11 and the cathode 12 were made of the following metal plates: Metal tin plate (60mm x 20mm x 1.0mm or 80mm x 60mm x 1.0mm) Metal zinc plate (60mm x 20mm x 1.0mm) Metal molybdenum plate (60mm x 20mm x 1.0mm) Metal nickel plate (60mm x 20mm x 1.0mm) Platinum plate (60mm x 5mm x 0.5mm)

[0072] As the power supply 13, a DC stabilized power supply (PS30V5A10, manufactured by AS ONE Corporation) was used.

[0073] A magnetic stirrer was used as the stirring bar 14 .

[0074] Methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the solvent for the electrolytic solution 20. EMITFB (1-ethyl-3-methylimidazolium tetrafluoroborate, manufactured by Tokyo Chemical Industry Co., Ltd.), LiClO4 (lithium perchlorate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), or LiBF4 (lithium tetrafluoroborate, manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the electrolyte. Powdered sulfur (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the sulfur source.

[0075] In Reference Examples 1 to 3, the following standards (reagents) were used: SnS2 (tin disulfide, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ZnS (zinc sulfide, manufactured by SIGMA ALDRICH) MoS2 (molybdenum disulfide, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0076] [Manufacturing method] Example 1 47.52 g of methanol was used as a solvent, and 2.38 g of EMITFB as an electrolyte was dissolved in methanol, and 3.42 g of sulfur was further added as a sulfur source to prepare the electrolytic solution 20 according to Example 1.

[0077] The obtained electrolytic solution 20 was added to the electrolytic cell 10 at room temperature. The subsequent steps were also carried out at room temperature. In the electrolytic cell 10, the anode 11 and the cathode 12 were both made of metal tin plates and were placed so that the distance between the electrodes was 3 mm. The metal tin plates used as the anode 11 and the cathode 12 each had a size of 60 mm × 20 mm × 1.0 mm and were placed so that they were approximately half immersed in the electrolytic solution 20, with the contact area with the electrolytic solution 20 being 12.6 cm 2 It was decided.

[0078] In the electrolysis step, argon gas was flowed into the electrolytic solution 20 in the electrolytic cell 10 at a rate of 5 mL / min while the electrolytic solution 20 was stirred with a stirrer 14, and a constant voltage setting of 2.0 V was applied between the anode 11 and the cathode 12 by the power source 13. In this way, a current of 79 to 209 mA was applied to the electrolytic solution 20 for 7 hours, thereby carrying out the electrolysis step according to Example 1. The weight of the anode 11 after the electrolysis step was reduced by 2.18 g compared to the weight before the step started.

[0079] After the electrolysis step was completed, a washing step was carried out. In the washing step, the precipitate attached to the surface of the cathode 12 and the precipitate in the electrolytic solution 20 were filtered and dried under reduced pressure at 50°C to obtain 5.74 g of a brown powder. 114.8 g of carbon disulfide was added to the obtained brown powder, and the mixture was stirred at room temperature for 20 minutes, filtered, and dried under reduced pressure at 50°C to obtain 3.32 g of an ochre powder (precipitate after the washing step).

[0080] (Examples 2 to 10 and Comparative Example 1) For Examples 2 to 10 and Comparative Example 1, the preparation of the electrolytic solution 20, the electrolysis step, and the cleaning step were carried out in the same manner as in Example 1, but under the conditions shown in Table 1 below.

[0081] In Example 2 and Comparative Example 1, the platinum plate used as the cathode 12 was placed so that it was immersed in the electrolyte 20 by about half, and the contact area with the electrolyte 20 was 3.3 cm 2 It was decided.

[0082] In Example 6, the electrolysis process was carried out using two metal tin plates each measuring 80 mm × 60 mm × 1.0 mm as the anode 11 and the cathode 12. In Example 6, the metal tin plates of the anode 11 and the cathode 12 were placed so as to be almost completely immersed in the electrolytic solution 20, and the contact area with the electrolytic solution 20 was 194.4 cm. 2 It was decided.

[0083] In the electrolysis steps of Examples 3 and 5 and Comparative Example 1, the power source 13 was set to a constant voltage, while in Examples 2, 4, and 6 to 10, the power source 13 was set to a constant current.

[0084] In each of the Examples and Comparative Examples, the weight loss of the anode 11 due to the electrolysis step and the weight of the deposit after the washing step were as shown in Table 1 below.

[0085] In Examples 2 to 6, the precipitate obtained after the washing step was an ochre powder, similar to Example 1. In Comparative Example 1, a precipitate formed on the surface of the cathode 12 after the electrolysis step, and the precipitate obtained after the washing step was a gray powder. In Examples 7 and 8, a milky white powder was obtained as the precipitate after the washing step. In Examples 9 and 10, a black powder was obtained as the precipitate after the washing step.

[0086] [Table 1]

[0087] [Evaluation of precipitates after cleaning process] (SEM-EDX) The precipitates obtained after the cleaning process in Examples 6, 7, and 9 (hereinafter simply referred to as "precipitates") were subjected to elemental analysis by energy dispersive X-ray spectroscopy (SEM-EDX) using an SEM (scanning electron microscope, JSM-6510, manufactured by JEOL Ltd.), and simple quantitative analysis of elements was performed using the ZAF method. Observation of the samples using the SEM was performed under conditions of an accelerating voltage of 10 kV and a magnification of 10,000 times. For comparison, similar analyses were also performed on standard products, SnS (Reference Example 1), ZnS (Reference Example 2), and MoS (Reference Example 3).

[0088] The results of the simple quantitative analysis are shown in the following Tables 2 to 4. In the following Tables 2 to 4, "ND" indicates that the result was below the detection limit.

[0089] [Table 2]

[0090] [Table 3]

[0091] [Table 4]

[0092] As shown in Table 2, in the precipitate of Example 6, Sn and S were detected as the main components, similar to SnS2 of Reference Example 1, the standard product, indicating that tin sulfide was obtained. As shown in Table 3, in the precipitate of Example 7, Zn and S were detected as the main components, similar to ZnS of Reference Example 2, the standard product, indicating that zinc sulfide was obtained. As shown in Table 4, in the precipitate of Example 9, Mo and S were detected as the main components, similar to MoS2 of Reference Example 3, the standard product, indicating that molybdenum sulfide was obtained.

[0093] (TG-DTA) The precipitates obtained in Examples 1 to 8 were subjected to thermogravimetric analysis at a heating rate of 10°C / min under a nitrogen gas flow using a TG-DTA apparatus (differential thermal-thermogravimetric simultaneous analyzer, STA7300, manufactured by Hitachi High-Tech Corporation). For comparison, the precipitate obtained in Comparative Example 1 and the standard products SnS2 (Reference Example 1) and ZnS (Reference Example 2) were also analyzed in the same manner.

[0094] FIG. 2 shows TG curves obtained from the precipitate of Example 6 and SnS2 of Reference Example 1. As shown in FIG. 2, the precipitate of Example 6 showed a weight loss of about 5% up to around 400°C, which was thought to be due to impurities, but the weight loss after 500°C showed the same behavior as SnS2 of Reference Example 1. This confirmed that the main component of the precipitate of Example 6 was tin disulfide. Furthermore, the precipitates of Examples 1 to 5 also showed TG curves substantially similar to that of the precipitate of Example 6, confirming that the main component of these precipitates was tin disulfide.

[0095] The TG curve obtained from the precipitate of Comparative Example 1 behaved differently from the TG curve obtained from SnS2 of Reference Example 1, and DTA curve analysis confirmed an endothermic peak indicating a melting point near 232°C, the same as that of metallic tin. In other words, it was confirmed that the main component of the precipitate of Comparative Example 1 was metallic tin.

[0096] Next, Figure 3 shows TG curves obtained from the precipitate of Example 7 and the ZnS of Reference Example 2. As shown in Figure 3, the precipitate of Example 7 showed a weight loss of about 25% up to around 800°C, which was thought to be due to impurities, but the weight loss after 900°C showed the same behavior as that of the ZnS of Reference Example 2. This confirmed that the main component of the precipitate of Example 7 was zinc sulfide. Note that the precipitate of Example 8 also showed a TG curve substantially similar to that of the precipitate of Example 7, confirming that the main component was zinc sulfide.

[0097] (XRD) The precipitates obtained in Examples 1, 6, and 7 were subjected to X-ray diffraction measurement using an XRD device (X-ray diffractometer, MiniFlex600, manufactured by Rigaku Co., Ltd.) with Cu Kα radiation as the X-ray source in the 2θ range of 5 to 80°. For comparison, a standard SnS2 (Reference Example 1) was also analyzed in the same manner.

[0098] Fig. 4 shows the X-ray diffraction patterns of the precipitates of Examples 1 and 6 and the SnS2 of Reference Example 1. As shown in Fig. 4, the X-ray diffraction patterns obtained from the precipitates of Examples 1 and 6 showed multiple peaks that matched the X-ray diffraction pattern obtained from the SnS2 of Reference Example 1. This indicated that both the precipitates of Examples 1 and 6 contained tin disulfide.

[0099] Furthermore, the peaks in the X-ray diffraction patterns of the precipitates of Examples 1 and 6 were broader than the corresponding peaks of SnS2 of Reference Example 1, suggesting that the obtained powder was amorphous. In the X-ray diffraction patterns, the half-width of the peak at the minimum 2θ (2θ = 15°) at 2θ of 10° or more was 1.35° for the precipitate of Example 1, 0.57° for the precipitate of Example 6, and 0.092° for SnS2 of Reference Example 1.

[0100] Next, FIG. 5 shows the X-ray diffraction pattern of the precipitate of Example 7. As shown in FIG. 5, the X-ray diffraction pattern of the precipitate of Example 7 confirmed broad peaks of the (111) diffraction line and the (311) diffraction line, which indicate zinc sulfide. This indicated that the precipitate of Example 7 contained zinc sulfide. This also suggested that the precipitate of Example 7 was amorphous. In the X-ray diffraction pattern, the half-width of the peak at the minimum 2θ (2θ = 30°) when 2θ was 10° or more was 13° for the precipitate of Example 7.

[0101] (Raman spectroscopy) The precipitates obtained in Examples 1 and 6 were subjected to Raman spectroscopic analysis using a Raman spectroscopic analyzer (inVia, manufactured by Renishaw). For comparison, a standard product, SnS2 (Reference Example 1), was also analyzed in the same manner.

[0102] 6 is a diagram showing the Raman spectra of the precipitates of Examples 1 and 6 and the SnS of Reference Example 1. As shown in FIG. 6, the Raman spectra of the precipitates of Examples 1 and 6 match the Raman spectrum of the SnS of Reference Example 1, with a peak at 317 cm -1 A peak around 1000 nm was confirmed, which indicated that the precipitates of Examples 1 and 6 contained tin disulfide. [Industrial Applicability]

[0103] An embodiment of the present invention can be utilized in the production of metal sulfides. [Explanation of symbols]

[0104] 1 Electrolyzer 10 Electrolytic cell 11 Anode 12 Cathode 13 Power supply 14 Stirring bar 20 Electrolyte

Claims

1. A method for producing a metal sulfide, comprising an electrolysis step of contacting an anode containing a metal element M and a cathode with an electrolytic solution containing a sulfur source and applying current thereto, thereby depositing a metal sulfide containing the metal element M in the electrolytic solution or on at least one of the surface of the cathode.

2. 2. The method for producing a metal sulfide according to claim 1, wherein the metal element M is one or more selected from the group consisting of Sn, Zn, W, and Mo.

3. The method for producing a metal sulfide according to claim 1 , wherein the anode contains the metal element M in an amount of 50 mass % or more.

4. The method for producing metal sulfides according to claim 1 , wherein the sulfur source comprises elemental sulfur.

5. The method for producing a metal sulfide according to claim 1 , wherein the electrolytic solution further contains an electrolyte.

6. The method for producing a metal sulfide according to claim 1 , wherein the electrolytic solution contains an organic solvent as a solvent.

7. The method for producing a metal sulfide according to any one of claims 1 to 6, wherein in the electrolysis step, a potential difference between the anode and the cathode is set to 0.5 V or more and 3.0 V or less.

8. The method for producing a metal sulfide according to claim 7 , further comprising, after the electrolysis step, a washing step of washing the metal sulfide.

9. A metal sulfide obtained by the method for producing a metal sulfide according to claim 1, A metal sulfide having a half-width of a peak at the minimum 2θ of 0.5° or more when 2θ in an X-ray diffraction pattern is 10° or more.

Images