Method for manufacturing sulfur-containing materials

Abstract

To provide a method for manufacturing a sulfur-containing material that enables the formation of a battery with high discharge capacity.SOLUTION: A method for manufacturing a sulfur-containing material includes a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a sulfur-containing material. [Background technology]

[0002] Batteries are used for a variety of purposes. The characteristics of a battery depend on its constituent parts, such as electrodes, separators, and electrolytes, and research and development of each of these components is being actively conducted. In electrodes, electrode active materials are important, along with binders and current collectors, and research and development of electrode active materials is being actively conducted. For example, sulfur-containing materials and their manufacturing methods are known as electrode active materials (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,620,772 [Patent Document 2] International Publication No. 2019 / 176618 [Patent Document 3] US Patent Application Publication No. 2014 / 0134485 Summary of the Invention [Problem to be solved by the invention]

[0004] The sulfur-containing material used in Patent Document 1 and the like is required to be capable of forming a battery with a large discharge capacity, but the sulfur-containing material obtained by conventional manufacturing methods has the problem of insufficient discharge capacity.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a method for producing a sulfur-containing material that can form a battery with a large discharge capacity. [Means for solving the problem]

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a method for producing a sulfur-containing material, which includes a step of treating a specific material containing sulfur by a mechanochemical method, can solve the above-mentioned problems, and have thus completed the present invention.

[0007] That is, as a first aspect, the present disclosure provides a method for producing a sulfur-containing material, which includes a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound.

[0008] According to the first aspect of the present disclosure, it is possible to provide a method for producing a sulfur-containing material that can easily produce a sulfur-containing material that can be used to form a battery with a large discharge capacity.

[0009] In the first aspect of the present disclosure, the raw material composition preferably contains the sulfur component in an amount of 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the sulfur-modified compound.

[0010] In the first aspect of the present disclosure, in powder X-ray diffraction using Cu-Kα radiation, the sulfur-containing material preferably has a ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° of 1.5 or less (A / B≦1.5).

[0011] In the first aspect of the present disclosure, the mechanochemical treatment is preferably a dry grinding treatment.

[0012] In a second aspect, the present disclosure provides a method for producing a sulfur-containing material, the method including a heat treatment step of heat-treating a mixture containing elemental sulfur and an organic compound to form a heat-treated product, and a mechanochemical treatment step of mechanochemically treating the heat-treated product obtained in the heat treatment step.

[0013] According to the second aspect of the present disclosure, it is possible to provide a method for producing a sulfur-containing material that can easily produce a sulfur-containing material that can be used to form a battery with a large discharge capacity.

[0014] In the second aspect of the present disclosure, the heat treatment in the heat treatment step is preferably a treatment in which the mixture is heated at 250° C. or higher and 500° C. or lower in a non-oxidizing atmosphere.

[0015] In the second aspect of the present disclosure, the heat treatment is preferably a treatment in which heating is performed while discharging sulfur vapor.

[0016] In the second aspect of the present disclosure, in powder X-ray diffraction using Cu-Kα radiation, the sulfur-containing material preferably has a ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° of 1.5 or less (A / B≦1.5). [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a method for producing a sulfur-containing material that can easily produce a sulfur-containing material that can be used to form a battery with a large discharge capacity. DETAILED DESCRIPTION OF THE INVENTION

[0018] A. Methods for producing sulfur-containing materials The method for producing the sulfur-containing material of the present disclosure will now be described in detail.

[0019] The method for producing a sulfur-containing material of the present disclosure includes at least a mechanochemical treatment step, and can be divided into two aspects: a first aspect including a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound; and a second aspect including a heat treatment step of heat-treating a mixture containing elemental sulfur and an organic compound to form a heat-treated product, and a mechanochemical treatment step of mechanochemically treating the heat-treated product obtained in the heat treatment step.

[0020] According to the present disclosure, it is possible to produce a sulfur-containing material capable of forming a battery with a large discharge capacity.

[0021] The reason why the method for producing a sulfur-containing material according to the present disclosure can produce a sulfur-containing material capable of forming a battery with such a large discharge capacity is not clear, but is presumed to be as follows. That is, by mechanochemically treating the raw material composition or heat-treated product described above, a product can be obtained in which a stable interaction is formed between sulfur atoms and components derived from the sulfur-modified compound in the raw material composition or the organic compound in the heat-treated product (hereinafter, sometimes referred to as "sulfur-modified compounds, etc."). More specifically, a stable interaction can be generated between sulfur atoms derived from the sulfur component or elemental sulfur and atoms of the sulfur-modified compound in the raw material composition or atoms derived from the organic compound in the heat-treated product. For example, it is presumed that sulfur atoms derived from the sulfur component are incorporated into the sulfur-modified compound and become atoms constituting the sulfur-modified compound, or that sulfur atoms derived from the sulfur component are stably attached to the surface of the sulfur-modified compound. As a result, the product after the mechanochemical treatment process has a high sulfur content, but the sulfur atoms form a stable interaction with the sulfur-modified compound, etc. By being able to make such a product, the sulfur-containing material can be used to form batteries with a large discharge capacity.

[0022] In the present disclosure, the term "sulfur-containing material" refers to a material obtained by subjecting the raw material composition or heat-treated product to a mechanochemical treatment process. The sulfur-containing material may contain, for example, a sulfur-modified compound, elemental sulfur, and impurities. Hereinafter, the method for producing a sulfur-containing material according to the present disclosure will be described in detail with respect to each aspect.

[0023] A-1. First aspect The method for producing a sulfur-containing material according to the first embodiment of the present disclosure includes a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound.

[0024] In the mechanochemical treatment step in the first embodiment, a raw material composition containing a sulfur component and a sulfur-modified compound is subjected to mechanochemical treatment.

[0025] 1. Raw material composition The raw material composition used in the first embodiment contains a sulfur component and a sulfur-modified compound. Each component contained in such a raw material composition will be described below.

[0026] (1-1) Sulfur components The sulfur component used in the raw material composition used in the present disclosure is an inorganic sulfur compound containing sulfur atoms, which is blended as a component separate from the sulfur-modified compound. Such a sulfur component may be any component that can be blended as a component of a raw material composition and subjected to mechanochemical treatment together with a sulfur-modified compound to form a sulfur-containing material that can form a battery with a large discharge capacity, which is the effect of the present disclosure. Examples of the inorganic sulfur compound include compounds of sulfur and metals, elemental sulfur, and rubber-like sulfur. The compounds of sulfur and metals include those in which sulfur and metal are bonded together, such as Li2S, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, and MoS3. The elemental sulfur may be one having a structure in which eight sulfur atoms are bonded in a ring (S8 structure), and examples thereof include crystalline sulfur such as α-sulfur, β-sulfur, and γ-sulfur. The rubbery sulfur may be one in which an infinite number of sulfur atoms are bonded in a linear chain, and when stretched, the rubbery sulfur has the property of exhibiting rubber-like elasticity. In the present disclosure, the inorganic sulfur compounds may be used alone or in combination of two or more kinds in any ratio. In the present disclosure, the inorganic sulfur compound is preferably elemental sulfur, from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity.

[0027] The average particle size of the sulfur component is not particularly limited, but from the viewpoint of facilitating the reaction with the sulfur-modified compound, it is preferably in the range of 0.1 μm or more and 500 μm or less, more preferably in the range of 1 μm or more and 400 μm or less, and most preferably in the range of 10 μm or more and 300 μm or less.

[0028] In the present disclosure, the term "average particle size" refers to the median particle size measured by a laser diffraction light scattering method. In the laser diffraction light scattering method, the particle size is a volume-based diameter, and the secondary particle size of the object to be measured is measured. When measuring the average particle size by the laser diffraction light scattering method, the object to be measured can be measured by dispersing it in an aqueous dispersion medium.

[0029] From the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the content of the sulfur component in the raw material composition is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 90 parts by mass or less, and most preferably 25 parts by mass or more and 75 parts by mass or less, relative to 100 parts by mass of the sulfur-modified compound.

[0030] (1-2) Sulfur-modified compounds A sulfur-modified compound is an organic compound containing a sulfur atom in its structure, and can be, for example, an organic compound in which a sulfur atom and an atom other than sulfur form a covalent bond, etc. Therefore, for example, in a mixture of an organic compound and elemental sulfur described below, if the organic compound does not contain a sulfur atom in its structure, the mixture of the organic compound and elemental sulfur does not fall under the category of a sulfur-modified compound. The sulfur atoms contained in the sulfur-modified compound may be in a state in which a plurality of sulfur atoms are continuously bonded together, such as in a disulfide or trisulfide. The atoms other than sulfur contained in the sulfur-modified compound are atoms derived from organic compounds, such as carbon atoms, oxygen atoms, hydrogen atoms, nitrogen atoms, boron atoms, and phosphorus atoms. The sulfur-modified compound can be produced by heat treating a mixture containing elemental sulfur and an organic compound.

[0031] Examples of the organic compound include acrylic compounds, polyether compounds, pitches, polynuclear aromatic ring compounds, aliphatic hydrocarbon oxides, aliphatic polymer compounds, polymer compounds having a thiophene structure, and halogenated unsaturated hydrocarbons. In the present disclosure, from the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the organic compound is preferably any one of an acrylic compound, a polyether compound, pitches, a polynuclear aromatic ring compound, an aliphatic hydrocarbon oxide, an aliphatic polymer compound, and a polymer compound having a thiophene structure, more preferably any one of an acrylic compound and a polyether compound, and most preferably an acrylic compound.

[0032] In the present disclosure, examples of acrylic compounds include polyacrylonitrile compounds and other acrylic compounds.

[0033] Examples of the sulfur-modified compound include sulfur-modified acrylic compounds, sulfur-modified polyether compounds, sulfur-modified pitch compounds, sulfur-modified polynuclear aromatic ring compounds, sulfur-modified aliphatic hydrocarbon oxides, polythienoacene compounds, and polycarbon sulfides.

[0034] In the present disclosure, from the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the sulfur-modified compound is preferably either a sulfur-modified acrylic compound or a sulfur-modified polyether compound, and more preferably a sulfur-modified acrylic compound.

[0035] The total sulfur content in the sulfur-modified compound is not particularly limited, but from the viewpoint of further increasing the discharge capacity, it is preferably 30% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 75% by mass or less, and most preferably 45% by mass or more and 70% by mass or less. Here, the total sulfur content in the sulfur-modified compound can be calculated from the analysis results using a CHNS analyzer capable of analyzing sulfur and oxygen.

[0036] The content of the sulfur-modified compound is not particularly limited, but from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the content is preferably 50 parts by mass or more and 95 parts by mass or less, more preferably 53 parts by mass or more and 90 parts by mass or less, and most preferably 55 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the raw material composition.

[0037] In the present disclosure, the content of the sulfur-modified compound can be measured by a known method. For example, when the sulfur-modified compound is a sulfur-modified polyacrylonitrile compound, the content of the sulfur-modified compound can be measured by subjecting the raw material composition to thermogravimetric analysis. In the thermogravimetric analysis, the heating start temperature is set to 100°C or less, and the heating rate is set to a constant rate of 10°C / min. The thermal weight loss retention rate until the temperature reaches 350°C is measured, and the content ratio (mass%) of the remaining substance is confirmed, thereby measuring the content of the sulfur-modified compound in the raw material composition.

[0038] The sulfur-modified acrylic compound used in the sulfur-containing material of the present disclosure may be, for example, a compound in which sulfur and an atom in the acrylic compound are covalently bonded. Examples of methods for producing such a sulfur-modified acrylic compound include a method of heating elemental sulfur and an acrylic compound.

[0039] Examples of the sulfur-modified acrylic compound include sulfur-modified polyacrylonitrile compounds and other sulfur-modified acrylic compounds. In the present disclosure, from the viewpoint of forming a battery with a large discharge capacity, the sulfur-modified acrylic compound is preferably a sulfur-modified polyacrylonitrile compound.

[0040] The total sulfur content in the sulfur-modified acrylic compound is not particularly limited, but from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, it is preferably 30% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 75% by mass or less, and most preferably 45% by mass or more and 70% by mass or less. Here, the total sulfur content in the sulfur-modified acrylic compound can be calculated from the analysis results using a CHNS analyzer capable of analyzing sulfur and oxygen.

[0041] The sulfur-modified polyacrylonitrile compound may be, for example, a compound in which a sulfur atom of the sulfur component is covalently bonded to an atom in a polyacrylonitrile-based compound. A method for producing such a sulfur-modified polyacrylonitrile compound includes heating elemental sulfur and a polyacrylonitrile-based compound. The sulfur-modified polyacrylonitrile compound of the present disclosure may also include a compound obtained by heating elemental sulfur and particles in which a hydrocarbon is encapsulated in an outer shell made of a polyacrylonitrile-based compound. The encapsulated hydrocarbon may be a saturated or unsaturated aliphatic hydrocarbon having 3 to 8 carbon atoms.

[0042] In the present disclosure, the polyacrylonitrile-based compound may contain at least one of acrylonitrile and methacrylonitrile as a constituent unit. From the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the polyacrylonitrile-based compound preferably contains at least a constituent unit derived from acrylonitrile.

[0043] From the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the content of the structural units derived from acrylonitrile and methacrylonitrile is preferably 10 parts by mass or more, and more preferably 30 parts by mass or more, in 100 parts by mass of the polyacrylonitrile-based compound.

[0044] When the polyacrylonitrile-based compound contains a structural unit derived from acrylonitrile, from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the content of the structural unit derived from acrylonitrile is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 80 parts by mass or more, even more preferably 85 parts by mass or more, even more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and most preferably 100 parts by mass, in 100 parts by mass of the polyacrylonitrile-based compound. In other words, it is most preferable that the polyacrylonitrile-based compound consists only of structural units derived from acrylonitrile.

[0045] When the polyacrylonitrile-based compound contains a structural unit derived from methacrylonitrile, from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the content of the structural unit derived from methacrylonitrile is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 30 parts by mass or more and 95 parts by mass or less, even more preferably 30 parts by mass or more and 90 parts by mass or less, even more preferably 30 parts by mass or more and 85 parts by mass or less, and most preferably 30 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of the polyacrylonitrile-based compound.

[0046] The polyacrylonitrile compound may contain a constituent unit derived from a monomer other than acrylonitrile and methacrylonitrile. Examples of the other monomer include acrylic monomers such as (meth)acrylate, (meth)acrylic acid ester, (meth)acrylamide, ethylene glycol (meth)acrylate, 1,6-hexanediol (meth)acrylate, neopentyl glycol di(meth)acrylate, and glycerin di(meth)acrylate; and conjugated dienes such as butadiene and isoprene. Two or more of these other monomers can be used in combination. Here, "(meth)acrylate" refers to either "acrylate" or "methacrylate", and "(meth)acrylic" refers to either "acrylic" or "methacrylic".

[0047] The other sulfur-modified acrylic compound may be, for example, a compound in which sulfur and an atom in the other acrylic compound are covalently bonded. A method for producing such other sulfur-modified acrylic compound includes heating elemental sulfur and the other acrylic compound.

[0048] The other acrylic compounds contain an acrylic monomer other than acrylonitrile and methacrylonitrile as a structural unit. The acrylic monomer may be the same as the acrylic monomer described as the other monomer. The other sulfur-modified acrylic compounds may contain the conjugated diene as a structural unit.

[0049] The sulfur-modified polyether compound may be, for example, a compound in which sulfur and an atom in the polyether compound are covalently bonded. The sulfur-modified polyether compound may be produced, for example, by heating a mixture of elemental sulfur and a polyether compound as an organic compound. Examples of polyether compounds include polyethylene glycol, polypropylene glycol, ethylene oxide / propylene oxide copolymer, and polytetramethylene glycol. The polyether compound may be terminated with an alkyl ether group, an alkylphenyl ether group, or an acyl group, or may be an ethylene oxide adduct of a polyol such as glycerin or sorbitol.

[0050] The weight average molecular weight of the polyether compound is not particularly limited, but from the viewpoint of ease of handling, it is preferably 100 or more and 20,000 or less, more preferably 150 or more and 10,000 or less, and most preferably 200 or more and 8,000 or less. Here, the weight average molecular weight is a value calculated using gel permeation chromatography (GPC) in terms of polystyrene.

[0051] The sulfur-modified pitch compound can be, for example, a compound in which sulfur and an atom in a pitch are covalently bonded. The sulfur-modified pitch compound can be produced, for example, by heating a mixture of elemental sulfur and an organic compound such as a pitch. Examples of pitches include petroleum pitch, coal pitch, mesophase pitch, asphalt, coal tar, coal tar pitch, organic synthetic pitch obtained by polycondensation of condensed polycyclic aromatic hydrocarbon compounds, and organic synthetic pitch obtained by polycondensation of heteroatom-containing condensed polycyclic aromatic hydrocarbon compounds. Pitches are mixtures of various compounds and may contain condensed polycyclic aromatic compounds. The condensed polycyclic aromatic compounds contained in pitches may be a single type or multiple types. The condensed polycyclic aromatic compounds may contain nitrogen atoms or sulfur atoms in addition to carbon and hydrogen in the ring.

[0052] The sulfur-modified polynuclear aromatic ring compound can be, for example, a compound in which sulfur and an atom in the polynuclear aromatic ring compound are covalently bonded. The sulfur-modified polynuclear aromatic ring compound can be produced, for example, by heating a mixture of elemental sulfur and a polynuclear aromatic ring compound as an organic compound. Examples of polynuclear aromatic ring compounds include benzene-based aromatic ring compounds such as naphthalene, anthracene, tetracene, pentacene, phenanthrene, chrysene, picene, pyrene, benzopyrene, perylene, and coronene; aromatic ring compounds in which some of the benzene-based aromatic ring compounds are five-membered rings; and heteroatom-containing heteroaromatic ring compounds in which some of the carbon atoms are replaced with sulfur, oxygen, nitrogen, or the like. Furthermore, these polynuclear aromatic ring compounds may have a substituent such as a linear or branched alkyl group having from 1 to 12 carbon atoms, an alkoxyl group, a hydroxyl group, a carboxyl group, an amino group, an aminocarbonyl group, an aminothio group, a mercaptothiocarbonylamino group, or a carboxyalkylcarbonyl group.

[0053] The sulfur-modified aliphatic hydrocarbon oxide may be, for example, a compound in which sulfur and an atom in an aliphatic hydrocarbon oxide are covalently bonded. The sulfur-modified aliphatic hydrocarbon oxide may be produced by heating a mixture of elemental sulfur and an aliphatic hydrocarbon oxide as an organic compound. Examples of the aliphatic hydrocarbon oxide include aliphatic hydrocarbon oxides such as aliphatic alcohols, aliphatic aldehydes, aliphatic ketones, aliphatic epoxides, and fatty acids.

[0054] The polythienoacene compound can be a compound having a sulfur-containing polythienoacene structure represented by the following general formula (1).

[0055] [ka]

[0056] The polythienoacene compound can be produced by heating a mixture of an aliphatic polymer compound having a linear chain structure, such as polyethylene, or a polymer compound having a thiophene structure, such as polythiophene, and elemental sulfur.

[0057] The polycarbon sulfide is represented by the general formula (CS x ) n (wherein x is 0.5 to 2, and n is a number of 4 or more). The polycarbon sulfide can be produced by reacting a complex of an alkali metal sulfide such as sodium sulfide and elemental sulfur with a halogenated unsaturated hydrocarbon such as hexachlorobutadiene as an organic compound.

[0058] (1-3) Other ingredients The raw material composition may contain other components as necessary. From the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the total content of the sulfur component and the sulfur-modified compound is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, even more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, even more preferably 99 parts by mass or more, and most preferably 100 parts by mass, in 100 parts by mass of the raw material composition. In other words, it is most preferable that the raw material composition does not contain any components other than the sulfur component and the sulfur-modified compound.

[0059] (1-4) Total content of sulfur atoms in the raw material composition In the present disclosure, from the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the total content of sulfur atoms in the raw material composition is preferably 50% by mass or more and 90% by mass or less, more preferably 51% by mass or more and 85% by mass or less, even more preferably 52% by mass or more and 80% by mass or less, still more preferably 55% by mass or more and 75% by mass or less, and most preferably 56% by mass or more and 70% by mass or less. Here, the total content of sulfur atoms in the raw material composition means the content of sulfur atoms per total mass of the raw material composition. For example, when the raw material composition contains only a sulfur component and a sulfur-modified compound, the total content of sulfur atoms per total mass of the raw material composition can be the sum of the content of sulfur atoms in the sulfur component and the content of sulfur atoms in the sulfur-modified compound.

[0060] 2. Mechanochemical treatment The mechanochemical treatment performed on the raw material composition may be any treatment that can impart mechanical energy to the raw material composition containing a sulfur component and a sulfur-modified compound and can form a sulfur-containing material that can form a battery with a large discharge capacity, which is the effect of the present disclosure.

[0061] Although the mechanism that promotes the formation of interactions between sulfur atoms in the sulfur component and atoms in the sulfur-modified compound has not been identified, it is presumed that the application of mechanical energy to a raw material composition containing the sulfur component and the sulfur-modified compound causes changes in the thermodynamic, crystallographic, chemical properties, etc. of at least one of the sulfur component and the sulfur-modified compound, resulting in modification of the surface of the sulfur component, the sulfur-modified compound, or both, thereby promoting the formation of interactions between sulfur atoms in the sulfur component and atoms in the sulfur-modified compound. The mechanical energy is, for example, energy generated in the pulverization process of a solid substance, and examples thereof include impact, compression, shear, shear stress, frictional force, centrifugal force, and the like.

[0062] Such mechanochemical treatments include pulverization, but dry pulverization is preferred from the viewpoint of promoting the formation of interactions between sulfur atoms in the sulfur component and atoms in the sulfur-modified compound. The dry pulverization can provide a composite of mechanical energies such as impact, compression, shear, shear stress, frictional force, and centrifugal force, making it easier to obtain a sulfur-containing material capable of forming a battery with a large discharge capacity.

[0063] From the viewpoint of easily obtaining a sulfur-containing material capable of forming a battery with a large discharge capacity, the above-mentioned pulverization treatment is more preferably a pulverization treatment capable of imparting any mechanical energy such as impact, compression, shear, shear stress, frictional force, centrifugal force, etc. to the raw material composition, even more preferably a pulverization treatment capable of imparting impact, compression, and shear, and most preferably a pulverization treatment capable of imparting impact, compression, shear, and centrifugal force.

[0064] Examples of the grinding equipment used in the grinding treatment include known grinding equipment such as a ball mill, a bead mill, a vibration mill, a media stirring mill, a roller mill, a planetary mill, a disc mill, a roll crusher, a gliding roll, a jet mill, a cyclone mill, and a mortar. In the present disclosure, the grinding device is preferably any one of a ball mill, a bead mill, a roller mill, a disk mill, a media stirring mill, and a planetary mill, because it can efficiently apply impact, compression, and shear to the raw material composition, and can easily form a sulfur-containing material capable of forming a battery with a large discharge capacity. In the present disclosure, the grinding device is more preferably a media agitation mill or a planetary mill, because it can apply impact, compression, shear, and centrifugal force to the raw material composition, and can easily form a sulfur-containing material capable of forming a battery with a large discharge capacity. In the present disclosure, it is particularly preferable that the pulverizing device is a planetary mill, because a large centrifugal force can be applied to the raw material composition, and a sulfur-containing material capable of forming a battery with a large discharge capacity can be easily formed in a short time.

[0065] The mechanochemical treatment may be carried out in a vacuum atmosphere, an oxidizing atmosphere, or a non-oxidizing atmosphere. However, it is preferable to carry out the treatment in a non-oxidizing atmosphere, from the viewpoint of being able to suppress oxidation reactions due to contact of the produced sulfur-containing material with moisture, oxygen, etc.

[0066] The vacuum atmosphere may be, for example, an atmosphere in which moisture, carbon dioxide, etc. are forcibly removed by using a vacuum pump or the like to maintain the pressure at 100 Pa or less.

[0067] The oxidizing atmosphere may be an atmosphere containing an oxidizing gas, such as oxygen, ozone, or nitrogen dioxide.

[0068] The non-oxidizing atmosphere may be, for example, an atmosphere with an oxygen concentration of less than 5% by volume. From the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the oxygen concentration is preferably less than 2% by volume, more preferably 1% by volume or less, even more preferably 0.1% by volume or less, even more preferably 0.05% by volume or less, and most preferably an atmosphere that is substantially free of oxygen.

[0069] Specific examples of the non-oxidizing atmosphere include an inert gas atmosphere such as nitrogen, helium, argon, etc., a sulfur gas atmosphere, a hydrogen sulfide gas atmosphere, etc. From the viewpoint of the working environment, the non-oxidizing atmosphere is preferably an inert gas atmosphere such as nitrogen or argon.

[0070] When a raw material composition containing a sulfur component and a sulfur-modified compound is mechanochemically treated, conditions such as rotation speed, treatment time, temperature, pressure, and gravitational acceleration applied to the mixture can be appropriately set depending on the composition of the raw material composition and the treatment amount.

[0071] From the viewpoint of efficiently forming an interaction between the sulfur component and the sulfur-modified compound, the conditions of the mechanochemical treatment are preferably such that the reduction rate of the sulfur content in the raw material composition before and after the mechanochemical treatment step is 30% by mass or less, more preferably 25% by mass or less, and most preferably 20% by mass or less.

[0072] From the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the conditions of the mechanochemical treatment are such that the A / B of the raw material composition after the mechanochemical treatment step ((A / B of the raw material composition after the mechanochemical treatment step) / (A / B of the raw material composition before the mechanochemical treatment step)) is 2 / 3 or less, more preferably 1 / 2 or less, and most preferably 2 / 5 or less, relative to the A / B of the raw material composition before the mechanochemical treatment step. This is because, after the mechanochemical treatment step, the A / B ratio of the raw material composition becomes smaller, which allows the mechanochemical treatment to proceed effectively, and the resulting sulfur-containing material can be easily used to form a battery with a large discharge capacity. It is presumed that the sulfur component is consumed due to an interaction between the sulfur atoms in the sulfur component contained in the raw material composition and atoms other than sulfur in the sulfur-modified compound, resulting in a decrease in the intensity of the peak intensity (A), which is thought to be a diffraction peak derived from the sulfur component.

[0073] Here, the A / B of the raw material composition refers to the ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° in a diffraction chart of the raw material composition measured by powder X-ray diffraction using Cu-Kα radiation under the measurement conditions described below.

[0074] Regarding the measurement conditions for powder X-ray diffraction using Cu-Kα radiation, a powder X-ray diffractometer can be used, such as the Rigaku Ultima IV powder X-ray diffractometer, etc. The measurement conditions can be Cu-Kα radiation, tube voltage: 40 kV, tube current: 40 mA, scan speed: 0.5° / min, step width: 0.02°, number of accumulations: 1, and diffraction angle (2θ): 10° to 40°. Under the above measurement conditions, a diffraction peak attributable to, for example, a sulfur component having a crystalline structure such as elemental sulfur can be observed around 23.0° to 23.4°, and a diffraction peak attributable to, for example, a typical broad halo pattern attributable to an amorphous sulfur-modified compound can be observed around 24.8° to 25.2°.

[0075] In this disclosure, the "maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4°" refers to the difference between the maximum value I (A-max) of the diffraction intensity (cps) measured in the range of 23.0° to 23.4° and the minimum value I (min) of the diffraction intensity (cps) measured in the range of 20.0° to 40.0°. In other words, (A) = I (A-max) - I (min). Furthermore, the "maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2°" refers to the difference between the maximum value I(B-max) of the diffraction intensity (cps) measured in the range of 24.8° to 25.2° and the minimum value I(min) of the diffraction intensity (cps) measured in the range of 20.0° to 40.0°. In other words, (B) = I(B-max) - I(min).

[0076] From the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the conditions of the mechanochemical treatment are such that the content of sulfur components contained in the sulfur-containing material obtained after the mechanochemical treatment step, i.e., the content of sulfur components that remain without reacting with the sulfur-modified compound among the sulfur components added as components of the raw material composition, is preferably 20 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less, even more preferably 1 mass% or less, and most preferably 0 mass%, i.e., no sulfur components that remain without reacting with the sulfur-modified compound.

[0077] 3. Other processes The method for producing a sulfur-containing material according to the first embodiment includes a mechanochemical treatment step, but may also include other steps, such as a mixing step and a desulfurization step, as necessary.

[0078] (3-1) Mixing process The mixing step is a step of mixing the sulfur component and the sulfur-modified compound, and is preferably performed before the mechanochemical treatment step. By uniformly dispersing the sulfur component and the sulfur-modified compound, it becomes easier to obtain a sulfur-containing material that can form a battery with a large discharge capacity. The method for mixing the sulfur component and the sulfur-modified compound is not particularly limited, and examples thereof include a method of mixing using a grinding device capable of carrying out the dry treatment described in the section "(2) Mechanochemical Treatment Step," and a method of mixing using a known dry blending device such as a blender, a rocking mill, or a Henschel mixer.

[0079] (3-2) Desulfurization process In the present disclosure, the mechanochemical treatment step may be followed by a desulfurization step for removing unreacted sulfur components. Examples of the desulfurization step include a thermal desulfurization method and a solvent desulfurization method. Examples of the thermal desulfurization method include a method in which the sulfur-containing material is heated in a non-oxidizing atmosphere at a temperature of about 100° C. to 600° C. to gasify and remove the sulfur components in the sulfur-containing material (e.g., sulfur gas or hydrogen sulfide). The treatment time can be appropriately set depending on the treatment temperature, etc. The solvent desulfurization method may, for example, be a method in which the sulfur components in the sulfur-containing material are absorbed into a solvent, and the solvent that has absorbed the sulfur components is then removed. Examples of the solvent include an aqueous alkali solution, acetone, toluene, xylene, carbon disulfide, pinacoline, methicyl oxide, acetophenone, benzophenone, acetylacetone, 2-butanone, methanol, ethanol, propanol, butanol, acetonitrile, propionitrile, butyronitrile, nitromethane, nitroethane, nitropropane, nitrobenzene, dimethyl sulfoxide, N,N'-dimethylformamide, N,N'-dimethylacetamide, pyridine, N-methylpyrrolidinone, trimethyl phosphate, triethyl phosphate, hexamethylphosphoramide, phosphorane, etc. In this step, one solvent may be used, or multiple solvents may be used in combination. The treatment time for allowing the solvent to absorb the sulfur component can be appropriately set depending on the type of solvent. In the present disclosure, the desulfurization step is preferably a thermal desulfurization method, from the viewpoint that a sulfur-containing material capable of forming a battery with a large discharge capacity can be easily obtained.

[0080] 4. Sulfur-containing materials In the present disclosure, from the viewpoint of reducing the proportion of unreacted sulfur components derived from the raw material composition and facilitating the formation of a battery with a large discharge capacity, the sulfur-containing material obtained in the first embodiment preferably has a peak intensity ratio (A / B) of 1.5 or less (A / B≦1.5), more preferably 1.2 or less (A / B≦1.2), even more preferably 1.0 or less (A / B≦1.0), and most preferably 0.8 or less (A / B≦0.8).

[0081] In the present disclosure, the peak intensity ratio (A / B) can be adjusted by adjusting the conditions of each step in the method for producing a sulfur-containing material, such as by adjusting the conditions of the mechanochemical treatment in the mechanochemical treatment step or by adjusting the content of the sulfur component in the raw material composition to be subjected to the mechanochemical treatment. Specifically, the peak intensity ratio (A / B) can be reduced by increasing the treatment time in the mechanochemical treatment, increasing the rotation speed, or otherwise increasing the mechanical energy imparted to the raw material composition per unit time, or by both.

[0082] From the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the total content of sulfur atoms in the sulfur-containing material is preferably 50% by mass or more and 90% by mass or less, more preferably 51% by mass or more and 85% by mass or less, even more preferably 52% by mass or more and 80% by mass or less, even more preferably 55% by mass or more and 75% by mass or less, and most preferably 56% by mass or more and 70% by mass or less. Here, the total content of sulfur atoms in the sulfur-containing material means the content of sulfur atoms per total mass of the sulfur-containing material. Specifically, it can be the sum of the content of sulfur atoms in the sulfur-modified compound and the unreacted sulfur component and the content of sulfur atoms in the sulfur-modified compound per total mass of the sulfur-containing material. The content of sulfur atoms in the sulfur-containing material can be calculated from the analysis results obtained using a CHNS analyzer (vario MICRO cube, manufactured by Elementar Corporation) capable of analyzing sulfur and oxygen.

[0083] In the present disclosure, from the viewpoint that the resulting sulfur-containing material can form a battery with a large discharge capacity, the content of the sulfur-modified compound is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, even more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, even more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and most preferably 99 parts by mass or more, per 100 parts by mass of the sulfur-containing material.

[0084] The use of the obtained sulfur-containing material is not particularly limited, but it can be used in an electrode layer of an electrode in a battery, and is particularly useful as an active material for the electrode layer. By using it in an electrode layer of an electrode in a battery, the discharge capacity of the battery can be increased. The battery may be either a primary battery or a secondary battery, but a secondary battery is preferred.

[0085] When the sulfur-containing material is an active material in an electrode layer of a battery, the sulfur-containing material is preferably an active material contained in an electrode layer used in a secondary battery, and more preferably an active material contained in a positive electrode active material layer used in a secondary battery, i.e., a positive electrode active material.

[0086] The battery configuration is not particularly limited, and any known configuration can be appropriately adopted.

[0087] A-2. Second mode The method for producing a sulfur-containing material according to the second aspect of the present disclosure includes a heat treatment step of heat-treating a mixture containing elemental sulfur and an organic compound to form a heat-treated product, and a mechanochemical treatment step of mechanochemically treating the heat-treated product obtained in the heat treatment step.

[0088] 1. Heat treatment process In the heat treatment step in the second embodiment, a mixture containing elemental sulfur and an organic compound is heat treated to form a heat-treated product.

[0089] (1-1)Mixture The mixture used in the second embodiment contains elemental sulfur and an organic compound. The elemental sulfur that can be used is the same as the elemental sulfur described in the section "(1-1) Sulfur component" of "1. Raw material composition" in "A-1. First embodiment," and therefore a description thereof will be omitted here. The organic compound is an organic compound that serves as a raw material for the sulfur-modified compound, and can be the same as the organic compound described in the section "(1-2) Sulfur-modified Compound" in "A-1. First Aspect," so a description thereof will be omitted here. From the viewpoint of facilitating the production of a sulfur-containing material that can form a battery with a large discharge capacity, the organic compound used in the second aspect is preferably any of acrylic compounds, polyether compounds, pitches, polynuclear aromatic ring compounds, aliphatic hydrocarbon oxides, aliphatic polymer compounds, and polymer compounds having a thiophene structure, more preferably any of acrylic compounds and polyether compounds, and most preferably an acrylic compound. Examples of acrylic compounds include polyacrylonitrile compounds and other acrylic compounds.

[0090] In the present disclosure, from the viewpoint of facilitating the production of a sulfur-containing material capable of forming a battery with a large discharge capacity, the content of elemental sulfur in the mixture is preferably 100 parts by mass or more and 1,500 parts by mass or less, and more preferably 120 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the organic compound.

[0091] The method for mixing elemental sulfur and the organic compound can be the same as the method for mixing the sulfur component and the sulfur-modified compound described in the section "3. Other steps" of "A-1. First embodiment," and therefore, the explanation here is omitted.

[0092] (1-2) Heat treatment From the viewpoint of facilitating the production of a sulfur-containing material capable of forming a battery with a large discharge capacity, the temperature at which the mixture containing elemental sulfur and the organic compound is heated is preferably 250°C or higher and 500°C or lower, and more preferably 260°C or higher and 450°C or lower. The heat treatment is preferably a treatment in which the material is heated in a vacuum atmosphere or a non-oxidizing atmosphere, and more preferably a treatment in which the material is heated in a non-oxidizing atmosphere, from the viewpoint that an oxidation reaction due to contact of the heat-treated material with moisture, oxygen, etc. can be suppressed and a sulfur-containing material capable of forming a battery with a large discharge capacity can be easily obtained. In this step, from the viewpoint that the obtained sulfur-containing material can form a battery with a large discharge capacity, the heat treatment is preferably performed at 250°C or higher and 500°C or lower in a non-oxidizing atmosphere or a vacuum atmosphere, more preferably at 250°C or higher and 500°C or lower in a non-oxidizing atmosphere, and most preferably at 260°C or higher and 450°C or lower in a non-oxidizing atmosphere. The vacuum atmosphere and non-oxidizing atmosphere can be the same as those described in the section "2. Mechanochemical treatment" of "A-1. First embodiment," and therefore a description thereof will be omitted here.

[0093] In this step, elemental sulfur may be heated to form sulfur vapor, which may then react with the organic compound to form a heat-treated product (sulfur-modified compound). Because sulfur vapor has a high vapor pressure, the pressure inside the system may increase during the heat treatment. To prevent this pressure increase, the heat treatment may involve heating while discharging the sulfur vapor outside the system. Examples of methods for heating while discharging the sulfur vapor include a method of reducing the pressure inside the system and discharging the sulfur vapor, and a method of introducing an inert gas into the system to create a non-oxidizing atmosphere, as described in "2. Mechanochemical Treatment" of "A-1. First Aspect." Note that hydrogen sulfide may be generated by the reaction between sulfur vapor and the organic compound. Therefore, hydrogen sulfide may be discharged together with the sulfur vapor to protect the working environment.

[0094] Examples of devices capable of heating while discharging sulfur vapor outside the system include those described in JP-A-2014-22123, JP-A-2013-201100, and WO 2021 / 060044.

[0095] In this step, it is preferable to perform the heat treatment while mixing the elemental sulfur and the organic compound, from the viewpoint of facilitating the production of a heat-treated product with a uniform composition. Examples of a method of heat-treating while mixing the elemental sulfur and the organic compound include a method of providing a stirring blade such as a bamboo stirrer in a heating container and rotating it to heat-treat the elemental sulfur and the organic compound while mixing them, and a method of rotating the heating container itself to heat-treat the elemental sulfur and the organic compound while mixing them under their own weight. When mixing the elemental sulfur and the organic compound by rotating the heating container, it is preferable to use a heating container with a cylindrical structure or a combination of cylindrical shapes, from the viewpoint of facilitating the mixing of the elemental sulfur and the organic compound.

[0096] From the viewpoint of facilitating the production of a sulfur-containing material capable of forming a battery with a large discharge capacity, the sulfur content in the heat-treated product obtained in the heat treatment step is preferably 30% by mass or more and 80% by mass or less, more preferably 33% by mass or more and 70% by mass or less, and most preferably 35% by mass or more and 60% by mass or less.

[0097] 2.Mechanochemical treatment process In the mechanochemical treatment step in the second embodiment, the heat-treated product obtained in the heat treatment step is subjected to mechanochemical treatment. The mechanochemical treatment method in the second embodiment can be the same as that in the section "2. Mechanochemical treatment step" of "A-1. First embodiment," except that the raw material composition is replaced with the heat-treated product, and therefore further explanation will be omitted here.

[0098] 3. Other processes The method for producing a sulfur-containing material according to the second embodiment includes a heat treatment step and a mechanochemical treatment step, but may include other steps as necessary. Other processes include a mixing process, a recovery process, a sulfur content adjustment process, a desulfurization process, and the like.

[0099] (3-1) Mixing process The mixing step is a step of mixing elemental sulfur and an organic compound, and is preferably carried out before the heat treatment step. The mixing step can be the same as the step "(3-1) Mixing Step" in "3. Other Steps" of "A-1. First Aspect," except that the sulfur component is replaced with elemental sulfur and the sulfur-modified compound is replaced with the organic compound, and therefore a detailed description thereof will be omitted here.

[0100] (3-2) Recovery process The recovery step is a step of recovering the sulfur vapor and hydrogen sulfide discharged outside the system in the heat treatment step and returning them to the mixture in the heat treatment step. By including the recovery step in the method for producing a sulfur-containing material according to the second aspect, it is possible to achieve energy savings and an improvement in the working environment. Methods for recovering sulfur vapor and hydrogen sulfide include a method in which the sulfur vapor and hydrogen sulfide discharged to the outside of the system are condensed or cooled, and the liquefied sulfur is returned to the heating vessel. From the viewpoint of preventing blockage of the pipe for recovering the sulfur vapor and hydrogen sulfide discharged to the outside of the system, it is preferable to condense or cool the sulfur vapor and hydrogen sulfide at a temperature slightly higher than the melting point of sulfur, for example, in the range of 120°C to 150°C.

[0101] (3-3) Sulfur content adjustment process The sulfur content adjusting step is a step of adjusting the sulfur content, which is performed between the heat treatment step and the mechanochemical treatment step. By including the sulfur content adjusting step in the method for producing a sulfur-containing material according to the second aspect, it becomes easy to produce a sulfur-containing material having a desired sulfur content. The sulfur content may be adjusted by decreasing or increasing the content of elemental sulfur in the heat-treated product. Examples of methods for decreasing the content of elemental sulfur in the heat-treated product include a method for heat-treating the heat-treated product, a method for decompressing the heat-treated product, and a method for combining heat treatment and decompression treatment. Examples of methods for increasing the content of elemental sulfur in the heat-treated product include a method for adding elemental sulfur to the heat-treated product obtained in the heat treatment step.

[0102] When the heat-treated product is heat-treated to reduce the content of elemental sulfur, the heat-treatment temperature is preferably in the range of 200°C or higher and 600°C or lower, more preferably in the range of 230°C or higher and 550°C or lower, and most preferably in the range of 250°C or higher and 500°C or lower, from the viewpoint of efficiently reducing the elemental sulfur.

[0103] When the heat-treated product is subjected to reduced pressure treatment to reduce the content of the elemental sulfur, from the viewpoint of efficiently reducing the elemental sulfur, the degree of reduced pressure is more preferably 100 hPa or less, even more preferably 50 hPa or less, and most preferably 25 hPa or less.

[0104] The time required to reduce the content of elemental sulfur can be appropriately set depending on the heating and decompression treatment conditions. From the viewpoint of efficiently reducing elemental sulfur, when the heating temperature is 260°C, treatment is preferably performed at a reduced pressure of 20 hPa for 2 hours or more, when the heating temperature is 300°C, treatment is preferably performed at a reduced pressure of 20 hPa for 1 hour or more, and when the heating temperature is 350°C, treatment is preferably performed at a reduced pressure of 20 hPa for 0.5 hours to 15 hours.

[0105] (3-4) Desulfurization process The above-mentioned desulfurization step can be the same as that described in "(3-2) Desulfurization Step" of "3. Other Steps" in "A-1. First Aspect," except that the sulfur component is replaced with elemental sulfur and the sulfur-modified compound is replaced with an organic compound, and therefore a detailed description thereof will be omitted here.

[0106] 4. Sulfur-containing materials The sulfur-containing material produced by the second embodiment can be the same as that described in the section "4. Sulfur-containing material" of "A-1. First embodiment," and therefore, a description thereof will be omitted here.

[0107] B. Other The present disclosure includes the following aspects. [1] A method for producing a sulfur-containing material, comprising a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound. [2] The method for producing a sulfur-containing material according to [1], wherein the raw material composition contains a sulfur component in an amount of 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the sulfur-modified compound. [3] The method for producing a sulfur-containing material according to [1] or [2], wherein the ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° is 1.5 or less (A / B≦1.5) in powder X-ray diffraction using Cu-Kα radiation. [4] The method for producing a sulfur-containing material according to any one of [1] to [3], wherein the mechanochemical treatment is a dry grinding treatment. [5] a heat treatment step of heat-treating a mixture containing elemental sulfur and an organic compound to form a heat-treated product; and a mechanochemical treatment step of mechanochemically treating the heat-treated product obtained in the heat treatment step. [6] The method for producing a sulfur-containing material according to [5], wherein the heat treatment in the heat treatment step is a treatment of heating the mixture at 250°C or higher and 500°C or lower in a non-oxidizing atmosphere. [7] The method for producing a sulfur-containing material according to [5] or [6], wherein the heat treatment is a treatment in which heating is performed while discharging sulfur vapor. [8] A method for producing a sulfur-containing material according to any one of [5] to [7], wherein the ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° is 1.5 or less (A / B≦1.5) in powder X-ray diffraction using Cu-Kα radiation.

[0108] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea described in the claims and exhibits similar effects is included within the technical scope of the present disclosure. [Example]

[0109] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0110] Comparative Example 1: Preparation of sulfur-modified compound A Sulfur-modified polyacrylonitrile was produced according to the manufacturing example described in JP 2013-054957 A. Specifically, 10 parts by mass of polyacrylonitrile powder (Sigma-Aldrich, average particle size 200 μm) as an organic compound and 30 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α-sulfur) as elemental sulfur were mixed in a mortar. 20 g of the mixture was placed in a bottomed cylindrical glass tube with an outer diameter of 45 mm and a length of 120 mm. A silicone stopper equipped with a gas inlet tube and a gas outlet tube was attached to the opening of the glass tube. After the air inside the glass tube was replaced with nitrogen, the lower part of the glass tube was inserted into a crucible-type electric furnace. Nitrogen was introduced through the gas inlet tube to remove the generated hydrogen sulfide. The mixture was heated at 400 °C for 1 hour to obtain an intermediate product. The sulfur vapor condensed at the top or lid of the glass tube and refluxed. The obtained intermediate product was placed in a glass tube oven at 260°C, the pressure was reduced to 20 hPa, and the oven was heated for 180 minutes to remove elemental sulfur, thereby obtaining a sulfur-modified compound A. The total sulfur content in the sulfur-modified compound A was 49 mass%.

[0111] Comparative Example 2: Preparation of sulfur-modified compound B 10 parts by mass of polyacrylonitrile powder (Sigma-Aldrich, average particle size 200 μm) as an organic compound and 130 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α sulfur) as elemental sulfur were mixed in a mortar. 20 g of the mixture was placed in a bottomed cylindrical glass tube with an outer diameter of 45 mm and a length of 120 mm. A silicone stopper equipped with a gas inlet tube and a gas outlet tube was attached to the opening of the glass tube. After the air inside the glass tube was replaced with nitrogen, the bottom of the glass tube was inserted into a crucible-type electric furnace. Nitrogen was introduced through the gas inlet tube to remove the generated hydrogen sulfide. The mixture was heated at 400 °C for 1 hour to obtain an intermediate product. The sulfur vapor condensed on the top or lid of the glass tube and refluxed. The resulting intermediate product was placed in a glass tube oven at 260 °C, depressurized to 20 hPa, and heated for 90 minutes to remove the elemental sulfur, yielding sulfur-modified compound B. The total sulfur content in sulfur-modified compound B was 60% by mass.

[0112] [Example 1] Production of sulfur-containing material A A raw material composition containing 100 parts by mass of the sulfur-modified compound A produced in Comparative Example 1 and 30 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α sulfur) as a sulfur component was mechanochemically treated using a planetary ball mill (Fritsch, P-7 Classic Line) under an argon atmosphere at a rotation speed of 1,600 rpm for a treatment time of 300 minutes to obtain a sulfur-containing material A. The total content of sulfur atoms in the sulfur-containing material A was 60% by mass.

[0113] [Example 2] Production of sulfur-containing material B Ten parts by mass of polyacrylonitrile powder (Sigma-Aldrich, average particle size 200 μm) as an organic compound and 30 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α-sulfur) as elemental sulfur were mixed in a mortar. 20 g of the mixture was placed in a bottomed cylindrical glass tube with an outer diameter of 45 mm and a length of 120 mm. A silicone stopper equipped with a gas inlet and outlet tube was attached to the opening of the glass tube. After the air inside the glass tube was replaced with nitrogen, the lower part of the glass tube was inserted into a crucible-type electric furnace. Nitrogen was introduced through the gas inlet tube to remove the generated hydrogen sulfide. The mixture was heated at 400 °C for 1 hour to obtain an intermediate product. The sulfur vapor condensed on the top or lid of the glass tube and refluxed. The resulting intermediate product was placed in a glass tube oven at 260 °C and heated for 90 minutes to remove elemental sulfur, yielding a heat-treated product. The sulfur content in the heat-treated product was 60% by mass. Thereafter, the entire heat-treated product was subjected to mechanochemical treatment using a planetary ball mill (Fritsch, P-7 Classic Line) under an argon atmosphere at a rotation speed of 1,600 rpm for 300 minutes to obtain a sulfur-containing material B. The total content of sulfur atoms in the sulfur-containing material B was 60 mass%.

[0114] [Example 3] Production of sulfur-containing material C A raw material composition containing 100 parts by mass of the sulfur-modified compound A produced in Comparative Example 1 and 70 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α sulfur) as a sulfur component was mechanochemically treated using a planetary ball mill (Fritsch, P-7 Classic Line) under an argon atmosphere at a rotation speed of 1,600 rpm for a treatment time of 300 minutes to obtain a sulfur-containing material C. The total content of sulfur atoms in the sulfur-containing material C was 70% by mass.

[0115] [Comparative Example 3] Production of sulfur-containing material a A sulfur / carbon black composite with a sulfur content of 71% by mass was prepared by mixing 7.5 parts by mass of sulfur powder (Sigma-Aldrich, average particle size 200 μm, α sulfur) as elemental sulfur and 3 parts by mass of carbon black as an organic compound and heating the mixture at 155°C under an argon atmosphere. The X-ray diffraction analysis of the obtained sulfur / carbon black composite confirmed that the A / B ratio was 1.5 or less. 100 parts by mass of the sulfur-modified compound A produced in Comparative Example 1 was treated in an argon atmosphere at a rotation speed of 1,600 rpm for 300 minutes using a planetary ball mill (Fritsch, P-7 Classic Line). After treatment, 100 parts by mass of the previously prepared sulfur / carbon black composite was added and mixed by hand blending for 5 minutes to obtain a sulfur-containing material a. The total content of sulfur atoms in the sulfur-containing material a was 60% by mass.

[0116] (1) Total sulfur content (mass%) The total sulfur content in sulfur-modified compounds A and B, and the total sulfur atom content (mass%) in sulfur-containing materials A to C and sulfur-containing material a produced in Examples 1 to 3 and Comparative Examples 1 to 3 were calculated from the analysis results using a CHNS analyzer (model: varioMICROcube, manufactured by Elementar Analysensysteme GmbH) capable of analyzing sulfur and oxygen. The combustion tube temperature was 1150°C, the reduction tube temperature was 850°C, and a tin boat was used as the sample container. The results are shown in Tables 1 and 2.

[0117] (2) X-ray diffraction The sulfur-modified compounds A and B, sulfur-containing materials A to C, and sulfur-containing material a produced in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to X-ray diffraction analysis. A powder X-ray diffractometer (RINT Ultima+ manufactured by Rigaku Corporation) was used to measure the diffraction pattern under the following measurement conditions. The ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° was calculated. The results are shown in Tables 1 and 2.

[0118] <X-ray Diffraction Measurement Conditions> X-ray: Cu-Kα ray Tube voltage: 40 kV Tube current: 40 mA Step width: 0.02° Integration times: 1 time Scan speed: 0.5° / min Scanning mode: Continuous Scanning range: 10° to 40° Scanning axis: 2θ / θ

[0119] (3) Battery Evaluation Battery evaluations were performed using sulfur-modified compounds A and B, and sulfur-containing materials A to C and sulfur-containing material a produced in Examples 1 to 3 and Comparative Examples 1 to 3. <​​​​​​​​​​​​​​​​​An electrolyte was prepared by dissolving LiPF6 at a concentration of 1.0 mol / L in a mixed solvent consisting of 50% by volume of fluoroethylene carbonate and 50% by volume of diethyl carbonate.

[0123] (3-4) Battery construction A glass filter as a separator was sandwiched between the positive and negative electrodes and held in the case. Next, the electrolyte prepared above was poured into the case, and the case was sealed to prepare secondary batteries (coin type with a diameter of 20 mm and a thickness of 3.2 mm).

[0124] (3-5) Evaluation method The fabricated secondary battery was placed in a thermostatic chamber at 25°C, and 10 charge / discharge cycles were performed at a charge rate of 0.1C and a discharge rate of 0.1C, with a charge cut-off voltage of 3.0V and a discharge cut-off voltage of 1.0V. The discharge capacity (mAh / g) at the 10th cycle was measured. Note that, in this disclosure, "g" in the discharge capacity (mAh / g) represents the mass of the positive electrode active material in the electrode layer. The results are shown in Tables 1 and 2.

[0125] [Table 1]

[0126] [Table 2]

[0127] From Tables 1 and 2, it was found that the batteries using the sulfur-containing materials obtained by the production methods of the sulfur-containing materials of the Examples had large discharge capacities.

Claims

1. A method for producing a sulfur-containing material, comprising a mechanochemical treatment step of mechanochemically treating a raw material composition containing a sulfur component and a sulfur-modified compound.

2. 2. The method for producing a sulfur-containing material according to claim 1, wherein the raw material composition contains the sulfur component in an amount of 5 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the sulfur-modified compound.

3. The sulfur-containing material has a ratio (A / B) of a maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° and a maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2° in powder X-ray diffraction using Cu-Kα rays. The method for producing a sulfur-containing material according to claim 1, wherein the ratio (A / B) is 1.5 or less (A / B≦1.5).

4. 2. The method for producing a sulfur-containing material according to claim 1, wherein the mechanochemical treatment is a dry grinding treatment.

5. a heat treatment step of heat-treating a mixture containing elemental sulfur and an organic compound to form a heat-treated product; and a mechanochemical treatment step of mechanochemically treating the heat-treated product obtained in the heat treatment step.

6. 6. The method for producing a sulfur-containing material according to claim 5, wherein the heat treatment in the heat treatment step is a treatment of heating the mixture at 250°C or higher and 500°C or lower in a non-oxidizing atmosphere.

7. 7. The method for producing a sulfur-containing material according to claim 5, wherein the heat treatment is a treatment in which heating is performed while discharging sulfur vapor.

8. The sulfur-containing material has a ratio (A / B) of the maximum peak intensity (A) at a diffraction angle (2θ) of 23.0° to 23.4° in powder X-ray diffraction using Cu-Kα rays to the maximum peak intensity (B) at a diffraction angle (2θ) of 24.8° to 25.2°, which is 1.5 or less (A / B≦1.5). The method for producing a sulfur-containing material according to claim 5.

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