Sulfur-modified polyacrylonitrile, electrode active material, electrode for secondary battery and method for producing the same, and non-aqueous electrolyte secondary battery

Abstract

The present invention provides a sulfur-modified polyacrylonitrile, an electrode active material containing the sulfur-modified polyacrylonitrile, an electrode for a secondary battery containing the electrode active material, a method for manufacturing the electrode, and a non-aqueous electrolyte secondary battery using the electrode. The total sulfur content of the sulfur-modified polyacrylonitrile is 30% by mass to 55% by mass, and the value of the calculation formula (1) defined in the specification is less than 0.08.

Description

Technical Field

[0001] The present invention relates to a sulfur-modified polyacrylonitrile, an electrode active material containing the sulfur-modified polyacrylonitrile, an electrode for a secondary battery containing the electrode active material, a method for producing the electrode, and a nonaqueous electrolyte secondary battery using the electrode. Background Art

[0002] Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are small and lightweight, have high energy density, and can be repeatedly charged and discharged, and are widely used as power sources for portable electronic devices such as portable personal computers, handheld video cameras, and information terminals. In addition, from the perspective of environmental issues, the practical application of electric vehicles using non-aqueous electrolyte secondary batteries and hybrid vehicles in which a part of the power is utilized is underway. Therefore, in recent years, the further improvement of the performance of secondary batteries has been sought.

[0003] The characteristics of non-aqueous electrolyte secondary batteries depend on the electrodes, separators, electrolytes, etc., which are its components, and the research and development of each component is being carried out vigorously. In the electrode, the electrode active material is important together with the binder, the current collecting material, etc., and the research and development of the electrode active material is being carried out vigorously.

[0004] Sulfur-modified polyacrylonitrile obtained by heat-treating a mixture of polyacrylonitrile and sulfur in a non-oxidizing atmosphere has a large charge-discharge capacity and is known as an electrode active material with little decrease in charge-discharge capacity accompanying repeated charge and discharge (hereinafter sometimes referred to as cycle characteristics) (for example, see Patent Documents 1 to 3). Sulfur-modified polyacrylonitrile has been studied mainly as an electrode active material for a positive electrode, and has also been studied as an electrode active material for a negative electrode (for example, see Patent Document 3).

[0005] On the other hand, thermal desorption mass spectrometry is an analysis method that heats a sample in an ultra-high vacuum and uses a mass spectrometer to analyze the adsorbed and desorbed gas components, and can quantify gas components based on the inherent m / z of the fragment ions of the gas components. Thermal desorption mass spectrometry is also used in the field of battery electrodes to analyze volatile organic groups of positive electrode materials (for example, see Patent Document 4), analyze gases based on oxygen release from lithium transition metal composite oxides (for example, see Patent Document 5), etc., but no example of its application to sulfur-based electrode active materials is known.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2010 / 044437

[0009] Patent Document 2: Japanese Patent Application Publication No. 2014-022123

[0010] Patent Document 3: Japanese Patent Application Publication No. 2014-096327

[0011] Patent Document 4: International Publication No. 2011 / 062019

[0012] Patent Document 5: Japanese Patent Application Publication No. 2019-114454 Summary of the invention

[0013] Problems to be solved by the invention

[0014] Non-aqueous electrolyte secondary batteries seek to further improve battery characteristics, and electrode active materials also seek higher performance. If a secondary battery is stored for a long period of time in a charged state, the amount of electricity stored will decrease due to natural discharge, and self-discharge is likely to occur, especially at high temperatures. Sulfur-modified polyacrylonitrile is known as an electrode active material that can obtain non-aqueous electrolyte secondary batteries with low self-discharge at room temperature and excellent power retention characteristics, but the power retention characteristics at high temperatures are insufficient.

[0015] Solutions for solving problems

[0016] The present inventors have conducted intensive studies and have found that an electrode having excellent power storage characteristics even at high temperatures can be obtained by analyzing sulfur-modified polyacrylonitrile by thermal desorption mass spectrometry, thereby completing the present invention.

[0017] That is, the present invention is a sulfur-modified polyacrylonitrile in which the total sulfur content is 30% by mass to 55% by mass and the value of the following calculation formula (1) is less than 0.08.

[0018] <Calculation formula (1)>

[0019] E1 / (E1+E2+E3)(1)

[0020] (In the formula, E1, E2 and E3 are respectively 32 +2F 64 The value of F 32 and F 64 and m / z=32 and m / z=64, respectively, when the sulfur-modified polyacrylonitrile is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C. E1 represents the F fragment ion intensities at a measurement temperature range of 55°C or higher and less than 270°C. 32 +2F 64 E2 indicates that the measurement temperature range is 270°C or higher and less than 570°C. 32 +2F 64E3 indicates that the F value is within the measurement temperature range of 570°C or higher and 1000°C or lower. 32 +2F 64 .

[0021] Effects of the Invention

[0022] According to the present invention, there is provided a sulfur-modified polyacrylonitrile useful as an electrode active material for a non-aqueous electrolyte secondary battery having a large charge and discharge capacity and excellent power storage characteristics even at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a graph showing the results of thermal desorption mass spectrometry analysis of SPAN7 (Example 5) based on the electron ionization method. DETAILED DESCRIPTION

[0024] In the present invention, sulfur-modified polyacrylonitrile refers to a compound obtained by heat-treating polyacrylonitrile and elemental sulfur in a non-oxidizing atmosphere. Polyacrylonitrile may also be a homopolymer of acrylonitrile. In addition, it may also be a copolymer of acrylonitrile and other monomers. In the case where polyacrylonitrile is a copolymer, if the content of acrylonitrile is low, the battery performance is low, so the content of acrylonitrile in the copolymer is preferably at least 90% by mass. As other monomers, for example, acrylic acid, vinyl acetate, N-vinyl formamide, N, N'-methylenebis (acrylamide) can be listed.

[0025] In the sulfur-modified polyacrylonitrile of the present invention, the total sulfur content is 30% to 55% by mass. When the total sulfur content is less than 30% by mass, a large charge and discharge capacity may not be obtained, and when it is more than 55% by mass, excellent cycle characteristics may not be obtained. The total sulfur content of the sulfur-modified polyacrylonitrile of the present invention is preferably 33% to 45% by mass, and more preferably 35% to 43% by mass. It should be noted that the sulfur content of the sulfur-modified polyacrylonitrile can be calculated based on the analysis results using a CHN analysis device that can analyze sulfur and oxygen.

[0026] The sulfur-modified polyacrylonitrile of the present invention is characterized in that the intensity of the fragment ion at m / z=32 when measured by thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C is defined as F 32 , and the fragment ion intensity of m / z = 64 is set as F 64 , set the F in the range of 55℃ or more and less than 270℃ 32 +2F 64 The value of F is set to E1, and the temperature range of F is between 270℃ and 570℃. 32 +2F64 The value of F is set to E2, and the range of F is between 570°C and 1000°C. 32 +2F 64 When the value of is set to E3, the value of E1 / (E1+E2+E3) in calculation formula (1) is less than 0.08.

[0027] In the present invention, the measurement temperature range of thermal desorption mass analysis is set to 55°C to 1000°C, thereby not only being able to analyze the free sulfur contained in the sulfur-modified polyacrylonitrile and the thermally unstable polysulfide-bound sulfur, but also being able to analyze most of the sulfur in the sulfur-modified polyacrylonitrile in a gaseous state. In thermal desorption mass analysis, when the heating rate is too fast, the unevenness of the measured values ​​sometimes becomes larger, and when the heating rate is slow, sometimes no obvious peak can be observed. Therefore, the heating rate of thermal desorption mass analysis in the present invention is set to 60°C / minute. It should be noted that in the stage of reaching 1000°C, sulfur still remains in the measured sample, so 1000°C is maintained even after reaching 1000°C, and the measurement is continued for 5 minutes after reaching 1000°C.

[0028] In thermal desorption spectroscopy mass analysis, when the amount of sample used for measurement is too much, the contamination of the device becomes larger, so the sample amount is preferably small, but when it is too small, the unevenness becomes larger, so the sampling amount of sulfur-modified polyacrylonitrile in the thermal desorption spectroscopy mass analysis of the present invention is preferably 30ng to 80ng. In addition, when the particle size of the sulfur-modified polyacrylonitrile is too large, the release of gas from the inside of the particle sometimes becomes insufficient, so the average particle size of the sulfur-modified polyacrylonitrile used for measurement is preferably 30μm or less. It should be noted that in the present invention, the 50% particle size measured by the laser diffraction light scattering method is taken as the average particle size. In the laser diffraction light scattering method, the particle size is a volume-based diameter, and the secondary particle size of the measured particles is measured.

[0029] The ionization method of thermal desorption mass analysis in the present invention is the electron ionization method. Compared with other ionization methods, the desorbed gas from the measurement sample is more likely to become low-mass fragments in the electron ionization method. When the measurement sample is sulfur-modified polyacrylonitrile, the S-derived gas can be stably obtained. + The fragment ion m / z=32 and the fragment ion from S2 + The fragment ion m / z = 64. In the present invention, the fragment ion intensity of m / z = 32 is set as F 32 , and the fragment ion intensity of m / z = 64 is set as F 64 , do not use F 32 and F 64 The total of F 32 +2F 64 The index is due to the consideration of the mass of the fragment ions.

[0030] Regarding the sulfur-modified polyacrylonitrile of the present invention, the value of E1 / (E1+E2+E3) of the calculation formula (1) needs to be less than 0.08. When the value of E1 / (E1+E2+E3) of the calculation formula (1) is 0.08 or more, excellent cycle characteristics may not be obtained. The value of E1 / (E1+E2+E3) of the calculation formula (1) is preferably less than 0.05, more preferably less than 0.03, and most preferably less than 0.02.

[0031] It should be noted that the value of E1 / (E1+E2+E3) in calculation formula (1) is preferably lower, but a lot of work is required to make it less than 0.0005, so the value of E1 / (E1+E2+E3) in calculation formula (1) is preferably greater than 0.0005.

[0032] From the perspective of obtaining excellent power retention characteristics at high temperatures, the sulfur-modified polyacrylonitrile of the present invention is further preferably calculated in such a way that the value of E2 / (E1+E2+E3) of formula (2) is less than 0.29. After charging, the battery has a reduced residual capacity due to self-discharge, and the self-discharge is greater at high temperatures. In the present invention, the power retention characteristics at high temperatures refer to the characteristics of suppressing the reduction in residual capacity of the charged battery caused by self-discharge under high temperature conditions. The value of E2 / (E1+E2+E3) of formula (2) is preferably less than 0.26, and more preferably less than 0.23. It should be noted that a lot of labor is required to reduce the value of E2 / (E1+E2+E3) of formula (2), and the improvement effect of the power retention characteristics at high temperatures on the labor is also saturated, so the value of E2 / (E1+E2+E3) of formula (2) is preferably greater than 0.01.

[0033] The sulfur-modified polyacrylonitrile of the present invention is obtained by the following manufacturing method, which includes: a heat treatment step, in which polyacrylonitrile and elemental sulfur are heat-treated. The mixing ratio of polyacrylonitrile to elemental sulfur is preferably 100 to 1500 parts by mass relative to 100 parts by mass of polyacrylonitrile, and the temperature of the heat treatment is preferably 250°C to 550°C. The heat treatment is preferably carried out in a non-oxidizing atmosphere. From the perspective of uniform sulfur modification, polyacrylonitrile and elemental sulfur are preferably powders. When the particle size of polyacrylonitrile and elemental sulfur is too small, a lot of labor is required for particle size reduction, and when it is too large, sulfur modification is insufficient. Therefore, the particle size of polyacrylonitrile and elemental sulfur is preferably 1 μm to 1000 μm in terms of average particle size.

[0034] The sulfur-modified polyacrylonitrile obtained by heat treatment contains sulfur that is easily detached by heating. Therefore, in order to reduce the value of E1 / (E1+E2+E3), the sulfur-modified polyacrylonitrile obtained by heat treatment can be heated to remove the sulfur that is easily detached. However, when the heating temperature is too low, a long time is required, and when the heating temperature is too high, it costs money to remove the detached sulfur. Therefore, it is preferred to remove the sulfur by combining heating and decompression. The heating temperature is preferably 260 to 600°C, more preferably 300 to 550°C, and more preferably 350 to 500°C. The pressure in the case of decompression is preferably 100 hPa or less, more preferably 50 hPa or less, and most preferably 25 hPa or less. The time required for removing sulfur varies depending on the heating temperature and the decompression pressure. For example, it is preferred that at 260°C, decompression is performed at a pressure of 20 hPa for more than 10 hours; at 300°C, decompression is performed at a pressure of 20 hPa for more than 1 hour; at 350°C, decompression is performed at a pressure of 20 hPa for 0.5 hours to 15 hours.

[0035] The particle size of the sulfur-modified polyacrylonitrile of the present invention is preferably 0.1μm to 50μm in terms of average particle size. The particle size is a volume-based diameter. In the laser diffraction light scattering method, the diameter of the secondary particles is measured. In the present invention, the average particle size refers to the 50% particle size (D50) measured by the laser diffraction light scattering method. In order to make the average particle size of the sulfur-modified polyacrylonitrile less than 0.1μm, a lot of labor is required and further improvement in battery performance cannot be expected. In the case of more than 50μm, it is sometimes easy to cause peeling of the electrode mixture layer. The average particle size of the sulfur-modified polyacrylonitrile of the present invention is more preferably 0.5μm to 30μm, and more preferably 1μm to 20μm.

[0036] The sulfur-modified polyacrylonitrile of the present invention has a large charge-discharge capacity and excellent cycle characteristics as an electrode active material, and can be preferably used as an electrode active material of an electrode of a non-aqueous electrolyte secondary battery. Specifically, the sulfur-modified polyacrylonitrile of the present invention is applied to a current collector to form an electrode mixture layer having the sulfur-modified polyacrylonitrile. The electrode mixture layer is formed by adding the sulfur-modified polyacrylonitrile of the present invention, a binder, and a conductive additive to a solvent to prepare a slurry, applying the prepared slurry on the current collector, and drying.

[0037] It should be noted that the sulfur-modified polyacrylonitrile of the present invention can be used alone as an electrode active material or in combination with other sulfur-based active materials. Examples of other sulfur-based active materials include organic polysulfide (R-S-Sm-R: R is a hydrocarbon group, m = 1 to 50), carbon-sulfur polymer (C2S x ) y ∶x=2.5~50,y≥2) etc.

[0038] The binder can be a binder known as a binder for electrodes. For example, styrene-butadiene rubber, butadiene rubber, polyethylene, polypropylene, polyamide, polyamide-imide, polyimide, polyacrylonitrile, polyurethane, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-propylene-diene rubber, fluororubber, styrene-acrylate copolymer, ethylene-vinyl alcohol copolymer, acrylonitrile-butadiene rubber, styrene-isoprene rubber, polymethyl methacrylate, polyacrylate, polyvinyl alcohol, polyvinyl ether, carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose, cellulose nanofiber, polyethylene oxide, starch, polyvinyl pyrrolidone, polyvinyl chloride, polyacrylic acid, etc. can be listed.

[0039] As the binder, a water-based binder is preferred from the viewpoint of low environmental load and excellent adhesiveness, and styrene-butadiene rubber, sodium carboxymethylcellulose, and polyacrylic acid are particularly preferred. The binder may be used alone or in combination of two or more.

[0040] The content of the binder in the slurry is preferably 1 to 30 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the sulfur-modified polyacrylonitrile of the present invention.

[0041] The conductive aid can be a conductive aid known as a conductive aid for an electrode, specifically, natural graphite, artificial graphite, carbon black, Ketjen black, acetylene black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, vapor grown carbon fiber (VGCF), graphene, fullerene, needle cokes and other carbon materials; metal powders such as aluminum powder, nickel powder, titanium powder; conductive metal oxides such as zinc oxide and titanium oxide; sulfides such as La2S3, Sm2S3, Ce2S3, TiS2. The average particle size of the conductive aid is preferably 0.0001 μm to 100 μm, more preferably 0.01 μm to 50 μm.

[0042] The content of the conductive additive in the slurry is usually 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass, based on 100 parts by mass of the sulfur-modified polyacrylonitrile of the present invention.

[0043] Examples of the solvent used for preparing the slurry include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, nitromethane, N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, polyethylene oxide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, water, alcohol, etc. The amount of the solvent used can be adjusted according to the coating method of the slurry. For example, in the case of the doctor blade method, the amount of the solvent is preferably 20 to 300 parts by mass, and more preferably 30 to 200 parts by mass, relative to 100 parts by mass of the total amount of the sulfur-modified polyacrylonitrile, the binder, and the conductive auxiliary agent.

[0044] The slurry may contain other components. Examples of other components include a viscosity modifier, a reinforcing material, and an antioxidant.

[0045] There are no particular limitations on the method for preparing the slurry, and examples thereof include methods using a common ball mill, sand mill, bead mill, pigment disperser, pestle, ultrasonic disperser, homogenizer, rotation / revolution stirrer, planetary stirrer, Filmix, JETPASTER, and the like.

[0046] As the current collector, conductive materials such as titanium, titanium alloy, aluminum, aluminum alloy, copper, nickel, stainless steel, and nickel-plated steel are used. These conductive materials are sometimes coated with carbon on the surface. As the shape of the current collector, foil, plate, mesh, etc. can be listed. Among them, aluminum is preferred from the viewpoint of conductivity and price, and the shape is preferably foil. The thickness of the foil in the case of foil is usually 1 to 100 μm.

[0047] The method of applying the slurry to the collector is not particularly limited, and can use die coater method, comma coater method, curtain coater (curtain coater) method, spray coater method, gravure coater method, flexible coater method, blade coater method, scraper method, reverse roll method, brush coating method, dipping method and other methods. From the aspect of the surface state that can obtain a good coating layer according to the physical properties such as the viscosity of the slurry and the dryness, preferably die coater method, scraper method, scraper coater method.

[0048] The slurry can be applied on a single side of the collector or on both sides. When applied on both sides of the collector, each single side can be applied sequentially or both sides can be applied simultaneously. In addition, the slurry can be applied continuously to the surface of the collector or can be applied intermittently to the surface of the collector or can be applied in stripes. The thickness, length and width of the coating layer can be appropriately determined according to the size of the battery.

[0049] As a method for drying the slurry applied to the collector, there is no particular limitation, and various methods such as drying using warm air, hot air, low humidity air, vacuum drying, irradiation with far infrared rays, infrared rays, electron beams, etc., which are placed in a heating furnace, etc., can be used. According to the drying, volatile components such as solvents evaporate from the coating of the slurry to form an electrode mixture layer on the collector. Then, the electrode can also be pressed as needed. As a method for pressing, for example, mold pressing and roller pressing can be listed.

[0050] The electrode of the present invention has the same structure as a known electrode. Specifically, it comprises a current collector and an electrode mixture layer formed on the current collector. Furthermore, the electrode mixture layer contains the sulfur-modified polyacrylonitrile of the present invention.

[0051] The electrode of the present invention is not particularly limited and can be used in a non-aqueous secondary battery having a non-aqueous electrolyte. The non-aqueous electrolyte may also be any of a liquid electrolyte, a gel electrolyte, a solid electrolyte, etc. The electrode of the present invention can be more preferably used in a lithium ion secondary battery. The electrode of the present invention can be used as a positive electrode or a negative electrode.

[0052] The non-aqueous electrolyte secondary battery is usually composed of a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. When the electrode of the present invention is used as a positive electrode, an electrode having a known negative electrode active material can be used as a negative electrode, and when the electrode of the present invention is used as a negative electrode, an electrode having a known positive electrode active material can be used as a positive electrode. It should be noted that the negative electrode when the electrode of the present invention is used as a positive electrode and the positive electrode when the electrode of the present invention is used as a negative electrode are referred to as opposing electrodes.

[0053] Examples of known negative electrode active materials include natural graphite, artificial graphite, non-graphitizable carbon, easily graphitizable carbon, lithium, lithium alloys, silicon, silicon alloys, silicon oxide, tin, tin alloys, tin oxide, phosphorus, germanium, indium, copper oxide, antimony sulfide, titanium oxide, iron oxide, manganese oxide, cobalt oxide, nickel oxide, lead oxide, ruthenium oxide, tungsten oxide, and zinc oxide. In addition, examples include LiVO2, Li2VO4, Li4Ti5O 12 These negative electrode active materials may be used alone or in combination of two or more.

[0054] Examples of known positive electrode active materials include lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, and lithium-containing silicate compounds.

[0055] As the transition metal of the lithium transition metal composite oxide, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper and the like are preferred. Specific examples of lithium transition metal composite oxides include: lithium cobalt composite oxides such as LiCoO2; lithium nickel composite oxides such as LiNiO2; lithium manganese composite oxides such as LiMnO2, LiMn2O4, Li2MnO3; lithium transition metal composite oxides in which part of the transition metal atoms that form the main body of these lithium transition metal composite oxides are replaced by other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium and the like. As specific examples of lithium transition metal composite oxides in which part of the transition metal atoms that form the main body are replaced by other metals, for example, the following can be listed: Li 1.1 Mn 1.8 Mg 0.1 O4、Li 1.1 Mn 1.85 Al 0.05 O4、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Mn 0.5 O2、LiNi 0.80 Co 0.17 Al 0.03 O2、LiNi 0.80 Co 0.15 Al 0.05 O2、Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiMn 1.8 Al 0.2 O4、LiNi 0.5 Mn 1.5 O4, Li2MnO3-LiMO2 (M=Co, Ni, Mn), etc.

[0056] As the transition metal of the lithium-containing transition metal phosphate compound, vanadium, titanium, manganese, iron, cobalt, nickel, etc. are preferred. As specific examples, for example, LiFePO4, LiMn x Fe 1-xIron phosphate compounds such as PO4 (0<x<1); iron sulfate compounds such as LiFeSO4F; cobalt phosphate compounds such as LiCoPO4; lithium-containing transition metal phosphate compounds in which a part of the transition metal atoms that constitute the main body of these lithium-containing transition metal phosphate compounds are replaced by other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, niobium, etc.; vanadium phosphate compounds such as Li3V2(PO4)3, etc.

[0057] Examples of the lithium-containing silicate compound include Li 2 FeSiO 4 , etc. These positive electrode active materials may be used alone or in combination of two or more.

[0058] The counter electrode can be produced by replacing the sulfur-modified polyacrylonitrile of the present invention with the above-mentioned known negative electrode active material or known positive electrode active material.

[0059] Examples of non-aqueous electrolytes include: liquid electrolytes obtained by dissolving a supporting electrolyte in an organic solvent; polymer gel electrolytes obtained by dissolving a supporting electrolyte in an organic solvent and gelling the polymer; pure polymer electrolytes obtained by dispersing a supporting electrolyte in a polymer without containing an organic solvent; inorganic solid electrolytes, and the like.

[0060] As supporting electrolytes used in liquid electrolytes and polymer gel electrolytes, for example, conventionally known lithium salts can be used, for example, LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiCF3CO2, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SO2F)2, LiC(CF3SO2)3, LiB(CF3SO3)4, LiB(C2O4)2, LiBF2(C2O4), LiSbF6, LiSiF5, LiSCN, L iClO4, LiCl, LiF, LiBr, LiI, LiAlF4, LiAlCl4, LiPO2F2 and their derivatives, etc., among which it is preferred to use one or more selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SO2F)2, LiC(CF3SO2)3, derivatives of LiCF3SO3, and derivatives of LiC(CF3SO2)3.

[0061] The content of the supporting electrolyte in the liquid electrolyte and the polymer gel electrolyte is preferably 0.5 to 7 mol / L, more preferably 0.8 to 1.8 mol / L.

[0062] Examples of supporting electrolytes used in pure polymer electrolytes include LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SO2F)2, LiC(CF3SO2)3, LiB(CF3SO3)4, and LiB(C2O4)2.

[0063] Examples of inorganic solid electrolytes include Li 1+x A x B 2-y (PO4)3 (A = Al, Ge, Sn, Hf, Zr, Sc, Y, B = Ti, Ge, Zn, 0 < x < 0.5), LiMPO4 (M = Mn, Fe, Co, Ni), Li3PO4 and other phosphate materials, Li3XO4 (X = As, V), Li 3+x A x B 1-x O4 (A=Si, Ge, Ti, B=P, As, V, 0<x<0.6), Li 4+x A x Si 1-x O4 (A=B, Al, Ga, Cr, Fe, 0<x<0.4) (A=Ni, Co, 0<x<0.1), Li 4-3y Al y SiO4(0<y<0.06), Li 4-2y Zn y GeO4 (0<y<0.25), LiAlO2, Li2BO4, Li4XO4 (X=Si, Ge, Ti), lithium titanate (LiTiO2, LiTi2O4, Li4TiO4, Li2TiO3, Li2Ti3O7, Li4Ti5O 12 ) and other lithium composite oxides, compounds containing lithium and halogen such as LiBr, LiF, LiCl, LiPF6, LiBF4, compounds containing lithium and nitrogen such as LiPON, LiN(SO2CF3)2, LiN(SO2C2F5)2, Li3N, LiN(SO2C3F7)2, La 0.55 Li 0.35 TiO3 and other perovskite crystals with lithium ion conductivity, Li7-La3Zr2O 13 Crystals with garnet structure, 50Li4SiO4·50Li3BO3 and other glasses, Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75Lithium / phosphosulfide crystals such as S4, 30Li2S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 70Li2S·50GeS2, 50Li2S·50GeS2, etc. Lithium / phosphosulfide glasses such as Li7P3S 11 , Li 3.25 P 0.95 S4 and other glass ceramics, etc.

[0064] As the organic solvent used to prepare the liquid non-aqueous electrolyte used in the present invention, one or more organic solvents commonly used in liquid non-aqueous electrolytes can be used. Specifically, for example, saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds, amide compounds, saturated chain carbonate compounds, chain ether compounds, cyclic ether compounds, saturated chain ester compounds, etc. can be listed.

[0065] Among the organic solvents, saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds and amide compounds have high relative dielectric constants and thus play a role in increasing the dielectric constant of the non-aqueous electrolyte. Saturated cyclic carbonate compounds are particularly preferred.

[0066] Examples of the saturated cyclic carbonate compound include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, and 1,1-dimethylethylene carbonate.

[0067] Examples of the saturated cyclic ester compound include γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-caprolactone, δ-octanolactone, etc. Examples of the sulfoxide compound include dimethyl sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, thiophene, etc.

[0068] Examples of the sulfone compound include dimethyl sulfone, diethyl sulfone, dipropyl sulfone, diphenyl sulfone, sulfolane (also called tetramethylene sulfone), 3-methyl sulfolane, 3,4-dimethyl sulfolane, 3,4-diphenyl sulfolane, sulfolene, 3-methyl sulfolene, 3-ethyl sulfolene, and 3-bromomethyl sulfolene, among which sulfolane and tetramethyl sulfolene are preferred.

[0069] Examples of the amide compound include N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

[0070] In the described organic solvent, saturated chain carbonate compound, chain ether compound, cyclic ether compound and saturated chain ester compound can reduce the viscosity of nonaqueous electrolyte, can improve the mobility of electrolyte ions etc., can make the battery characteristics such as output density excellent.In addition, it is low viscosity, therefore can improve the performance of nonaqueous electrolyte under low temperature, particularly preferred saturated chain carbonate compound.

[0071] Examples of the saturated chain carbonate compound include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl butyl carbonate, tert-butyl methyl carbonate, diisopropyl carbonate, and tert-butylpropyl carbonate.

[0072] Examples of the chain ether compound or cyclic ether compound include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, tetrahydrofuran, dioxolane, dioxane, 1,2-bis(methoxycarbonyloxy)ethane, 1,2-bis(ethoxycarbonyloxy)ethane, 1,2-bis(ethoxycarbonyloxy)propane, ethylene glycol bis(trifluoroethyl) ether, propylene glycol bis(trifluoroethyl) ether, ethylene glycol bis(trifluoromethyl) ether, and diethylene glycol bis(trifluoroethyl) ether. Among them, dioxolane is preferred.

[0073] As the saturated chain ester compound, monoester compounds and diester compounds having a total of 2 to 8 carbon atoms in the molecule are preferred. Specific examples of the compound include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, methyl malonate, ethyl malonate, methyl succinate, ethyl succinate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, diacetylethylene glycol, diacetylpropylene glycol, and the like. Methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl propionate, and ethyl propionate are preferred.

[0074] In addition, as an organic solvent for preparing the non-aqueous electrolyte, for example, acetonitrile, propionitrile, nitromethane, derivatives thereof, and various ionic liquids can also be used.

[0075] Examples of polymers used in polymer gel electrolytes include polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyethylene, polyvinylidene fluoride, and polyhexafluoropropylene. Examples of polymers used in pure polymer electrolytes include polyethylene oxide, polypropylene oxide, and polystyrene sulfonic acid. There are no particular restrictions on the proportions and composite methods in the gel electrolyte, and any proportion or composite method known in the art may be used.

[0076] The non-aqueous electrolyte may include, for example, an electrode film forming agent, an antioxidant, a flame retardant, an anti-overcharge agent, and other known additives in order to improve battery life and safety. When other additives are used, the amount thereof is usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the non-aqueous electrolyte as a whole.

[0077] As a separator, a microporous film of a polymer commonly used in a non-aqueous electrolyte secondary battery can be used, without particular limitation. As a film, for example, a film formed by a polymer compound based on the following substances, its derivatives, copolymers of these substances, mixtures, etc. can be cited: polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyether sulfone, polycarbonate, polyamide, polyimide, polyethylene oxide, polypropylene oxide and other polyethers, carboxymethyl cellulose, hydroxypropyl cellulose and other celluloses, poly (meth) acrylic acid and its various esters, etc., these films can also be coated with ceramic materials such as aluminum oxide and silicon dioxide, magnesium oxide, aramid resin, and polyvinylidene fluoride.

[0078] These films can be used alone, or these films can be stacked and used as multilayer films. Moreover, in these films, various additives can be used, and their types and contents are not particularly limited. In these films, in the secondary battery manufactured by the manufacturing method of the secondary battery, a film consisting of polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone is preferably used. It should be noted that in the case where the nonaqueous electrolyte is a pure polymer electrolyte or an inorganic solid electrolyte, a separator may not be included.

[0079] The shape of the secondary battery is not particularly limited, and various shapes such as a coin shape, a cylindrical shape, a square shape, and a laminate shape may be adopted.

[0080] As the outer packaging member of the secondary battery, a laminated film or a metal container can be used. The thickness of the outer packaging member is usually less than 0.5 mm, preferably less than 0.3 mm. As the shape of the outer packaging member, flat (thin), square, cylindrical, coin-shaped, button-shaped, etc. can be listed.

[0081] The laminated film may also be a multilayer film having a metal layer between resin films. The metal layer is preferably an aluminum foil or an aluminum alloy foil for light weight. The resin film may be made of a polymer material such as polypropylene, polyethylene, nylon, polyethylene terephthalate, etc. The laminated film may be sealed by heat fusion and formed into the shape of an exterior member.

[0082] The metal container can be formed of, for example, stainless steel, aluminum or an aluminum alloy. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferred. In aluminum or an aluminum alloy, by setting the content of transition metals such as iron, copper, nickel, and chromium to less than 1%, the long-term reliability and heat dissipation in a high temperature environment can be greatly improved.

[0083] Example

[0084] The present invention will be described in further detail below by way of examples and comparative examples. However, the present invention is not limited by the following examples and the like. It should be noted that "parts" and "%" in the examples are by mass unless otherwise specified.

[0085] Raw material PAN mixture: 10 parts by mass of polyacrylonitrile powder (manufactured by Sigma-Aldrich, average particle size 200 μm) and 30 parts by mass of sulfur powder (manufactured by Sigma-Aldrich, average particle size 200 μm) were mixed in a mortar to prepare raw materials for sulfur-modified polyacrylonitrile in Production Examples 1 to 4.

[0086] [Production Example 1]

[0087] Sulfur-modified polyacrylonitrile was produced by the method according to the manufacturing example of Japanese Patent Publication No. 2013-054957. That is, after 20g of the raw material PAN mixture was placed in a bottomed cylindrical glass tube with an outer diameter of 45mm and a length of 120mm, a silicone plug with a gas inlet tube and a gas exhaust tube was assembled at 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 placed in a crucible-type electric furnace, and nitrogen was introduced from the gas inlet tube to remove the generated hydrogen sulfide while heating at 400°C for 1 hour. It should be noted that sulfur vapor condenses and refluxes at the upper part or the cover of the glass tube. The obtained intermediate product was placed in a glass tube oven at 260°C, decompressed, and heated at 20hPa for 1 hour to remove sulfur. After the obtained sulfur-modified product was crushed using a ball mill, it was classified by sieve to obtain sulfur-modified polyacrylonitrile SPAN1 with an average particle size of 10μm.

[0088] [Production Example 2]

[0089] In Production Example 1, except that the time for removing sulfur from the intermediate product was changed from 1 hour to 24 hours, the same operation as in Production Example 1 was carried out to obtain sulfur-modified polyacrylonitrile SPAN 2.

[0090] [Production Example 3]

[0091] Sulfur-modified polyacrylonitrile SPAN3 was obtained by the same operation as in Production Example 1 except that the conditions for removing sulfur from the intermediate product were changed from heating at 20 hPa under reduced pressure for 1 hour to heating at normal pressure under nitrogen flow for 24 hours.

[0092] [Production Example 4]

[0093] In Production Example 1, except that the temperature and time for removing sulfur from the intermediate product were changed from 260° C. for 1 hour to 300° C. for 3 hours, the same operation as in Production Example 1 was carried out to obtain sulfur-modified polyacrylonitrile SPAN4.

[0094] [Production Example 5]

[0095] In Production Example 1, except that the temperature and time for removing sulfur from the intermediate product were changed from 260° C. for 1 hour to 300° C. for 24 hours, the same operation as in Production Example 1 was carried out to obtain sulfur-modified polyacrylonitrile SPAN5.

[0096] [Production Example 6]

[0097] A heat-resistant glass tube with an outer diameter of 10 mm and an inner diameter of 6 mm was heated and expanded in the central portion to produce a whole pipette-type glass furnace core tube having an expanded portion with an outer diameter of 30 mm and a length of 50 mm in the central portion and capillaries with an outer diameter of 10 mm and a length of 150 mm at both ends.

[0098] 5 g of the raw material PAN mixture was placed in the expansion part of the furnace core tube, and the heating part was set in a 70 mm tubular electric furnace in such a way that the furnace core tube was inclined at 5°. After the furnace core tube was replaced with nitrogen, it was heated at 400°C for 1 hour while rotating once per minute to obtain an intermediate product. It should be noted that the gaps at both ends of the tubular electric furnace were filled with glass wool for insulation. During heating, nitrogen gas was transported from the lower end of the furnace core tube at a flow rate of 100 ml / min, and the generated hydrogen sulfide gas was discharged from the upper end of the furnace core tube. In addition, the heating part of the furnace core tube was set as the entire expansion part, but the sulfur sublimated and attached to the narrow tube part could be appropriately heated and dissolved and refluxed to the expansion part.

[0099] The obtained intermediate product was placed in a glass tube oven at 300°C, decompressed, and heated at 20 hPa for 3 hours to remove sulfur. The obtained sulfur-modified product was pulverized using a ball mill and classified using a sieve to obtain sulfur-modified polyacrylonitrile SPAN6 with an average particle size of 10 μm.

[0100] [Production Example 7]

[0101] In Production Example 6, except that the temperature for removing sulfur from the intermediate product was changed from 300° C. to 350° C., the same operation as in Production Example 6 was carried out to obtain sulfur-modified polyacrylonitrile SPAN7.

[0102] [Production Example 8]

[0103] In Production Example 6, sulfur-modified polyacrylonitrile SPAN 8 was obtained by performing the same operation as in Production Example 6 except that the temperature and time for removing sulfur from the intermediate product were changed from 300° C. for 3 hours to 250° C. for 1 hour.

[0104] [Production Example 9]

[0105] In Production Example 6, sulfur-modified polyacrylonitrile SPAN9 was obtained by performing the same operation as in Production Example 6, except that the temperature and time for removing sulfur from the intermediate product were changed from 300° C. for 3 hours to 250° C. for 5 hours.

[0106] [Production Example 10]

[0107] Sulfur-modified polyacrylonitrile SPAN6 and sulfur-modified polyacrylonitrile SPAN8 were mixed at a mass ratio of 25:75 to obtain sulfur-modified polyacrylonitrile SPAN10.

[0108] [Production Example 11]

[0109] Sulfur-modified polyacrylonitrile SPAN6 and sulfur-modified polyacrylonitrile SPAN8 were mixed at a mass ratio of 50:50 to obtain sulfur-modified polyacrylonitrile SPAN11.

[0110] The F of SPAN1 to 8 was determined by the following method. 32 、F 64 , sulfur content, and calculated E1 / (E1+E2+E3) and E2 / (E1+E2+E3). The results are shown in Tables 1 and 2. It should be noted that SPAN 2, 4 to 7, 9 to 11 are sulfur-modified polyacrylonitrile of the present invention, and therefore are Examples 1 to 8, and SPAN 1, 3, 8 are Comparative Examples 1 to 3.

[0111] 〔Sulfur content〕

[0112] The sulfur content was calculated from the analysis results using a CHN analyzer (Elementar Analysensysteme GmbH, model: varioMICROcube) capable of analyzing sulfur and oxygen. The combustion tube temperature was set to 1150°C, the reduction tube temperature was set to 850°C, and a tin boat was used as the sample container.

[0113] 〔Thermal Desorption Spectroscopy Mass Analysis〕

[0114] Thermal desorption mass analysis based on electron ionization method was performed using a thermal desorption analyzer (manufactured by Electronic Science Co., Ltd., model: TDS1200). It should be noted that the sampling amount of sulfur-modified polyacrylonitrile was set to 40 to 60 ng, the measurement temperature range was set to 55°C to 1000°C, the heating rate was set to 60°C / min, and after reaching 1000°C, it was maintained at 1000°C, and the data from the start of the measurement to 5 minutes after reaching 1000°C were used.

[0115] Just F 32 、F 64 For the fragment ion, the charge is measured in microamperes. 32 、F 64 Expressed as the amount of electricity per unit sample mass (mg).

[0116] It should be noted that Figure 1 This is a graph showing the results of thermal desorption mass spectrometry analysis of SPAN7 (Example 5) based on the electron ionization method.

[0117] [Table 1]

[0118]

[0119] [Table 2]

[0120]

[0121] [Manufacturing of electrodes containing sulfur-modified polyacrylonitrile]

[0122] Using the sulfur-modified polyacrylonitrile of Examples 1 to 8 and Comparative Examples 1 to 3, electrodes of Examples 1 to 8 and Comparative Examples 1 to 3 were produced by the following method.

[0123] 92.0 parts by mass of sulfur-modified polyacrylonitrile as electrode active material, 3.5 parts by mass of acetylene black (made by Denki Kagaku Kogyo) and 1.5 parts by mass of carbon nanotubes (made by Showa Denko, trade name VGCF) as conductive aids, 1.5 parts by mass of styrene-butadiene rubber (water dispersion, made by ZEON Japan) as binder, 1.5 parts by mass of carboxymethyl cellulose (made by DAICELFINECHEM) and 120 parts by mass of water as solvent were mixed using a self-rotating / revolutionary agitator to prepare a slurry. The slurry composition was applied to a collector of stainless steel foil (thickness 20 μm) by a doctor blade method and dried at 90°C for 3 hours. Then, the electrode was cut into a specified size and vacuum dried at 120°C for 2 hours to produce a disc-shaped electrode.

[0124] [Manufacturing of positive electrode 1]

[0125] 90.0 parts by mass of Li(Ni1 / 3 Co 1 / 3 Mn 1 / 3 )O2 (manufactured by Nippon Chemical Industry, trade name: NCM111, hereinafter referred to as NCM), 5.0 parts by mass of acetylene black (manufactured by Electric Chemical Industry) as a conductive aid, 5.0 parts by mass of polyvinylidene fluoride (manufactured by KUREHA) as a binder, and 100 parts by mass of N-methylpyrrolidone were mixed and dispersed using a rotation / revolution stirrer to prepare a slurry. The slurry composition was applied to a current collector of aluminum foil (thickness 20 μm) by a doctor blade method and dried at 90°C for 3 hours. Then, the electrode was cut into a specified size and vacuum dried at 120°C for 2 hours to produce a disc-shaped positive electrode 1.

[0126] [Manufacturing of negative electrode 1]

[0127] A lithium metal having a thickness of 500 μm was cut into a predetermined size to produce a disk-shaped negative electrode 1 .

[0128] 〔Preparation of non-aqueous electrolyte〕

[0129] LiPF6 was dissolved at a concentration of 1.0 mol / L in a mixed solvent consisting of 50 volume % of ethylene carbonate and 50 volume % of diethyl carbonate to prepare an electrolyte solution.

[0130] 〔Battery Assembly〕

[0131] The electrodes of Examples 1 to 8 and Comparative Examples 1 to 3 were used as positive electrodes, and negative electrode 1 was used as negative electrode, and the glass filter as a separator was sandwiched and held in a shell. Then, the non-aqueous electrolyte prepared in advance was injected into the shell, and the shell was sealed and sealed to produce non-aqueous electrolyte secondary batteries (coin-shaped with a diameter of 20 mm and a thickness of 3.2 mm) of Examples 9 to 16 and Comparative Examples 4 to 6.

[0132] In addition, the electrodes of Examples 1 to 8 and Comparative Examples 1 to 3 were used as negative electrodes, and positive electrode 1 was used as a positive electrode, and a polypropylene microporous membrane as a separator was sandwiched and held in a shell. Then, a non-aqueous electrolyte prepared in advance was injected into the shell, and the shell was sealed and sealed to produce non-aqueous electrolyte secondary batteries (coin-shaped with a diameter of 20 mm and a thickness of 3.2 mm) of Examples 17 to 24 and Comparative Examples 7 to 9.

[0133] [Evaluation as positive electrode active material]

[0134] The non-aqueous electrolyte secondary batteries of Examples 9 to 16 and Comparative Examples 4 to 6 were placed in a thermostatic chamber at 30°C, the charge termination voltage was set to 3.0V, the discharge termination voltage was set to 1.0V, and 12 cycles of charge and discharge at a charge rate of 0.2C and a discharge rate of 0.2C were performed to measure the charge and discharge capacity. Among them, after the charge of the 11th cycle was completed, the battery was stored at 60°C for 2 weeks and then discharged. The charge capacity before storage (charge capacity of the 11th cycle), the discharge capacity after storage (discharge capacity of the 11th cycle), the irreversible capacity (the difference between the charge capacity of the 11th cycle and the charge capacity of the 12th cycle), and the self-discharge capacity (the difference between the charge capacity before storage and the sum of the discharge capacity after storage and the irreversible capacity) are shown in Table 2. It should be noted that each capacity is the capacity per unit mass of sulfur-modified polyacrylonitrile as the positive electrode active material.

[0135] [Table 3]

[0136]

[0137] [Evaluation as negative electrode active material]

[0138] The non-aqueous electrolyte secondary batteries of Examples 17 to 24 and Comparative Examples 7 to 9 were subjected to the same operation as the evaluation of the positive electrode active material except that the charge end voltage was changed to 3.2 V and the discharge end voltage was changed to 0.8 V. The charge capacity before storage, the discharge capacity after storage, and the irreversible capacity are shown in Table 4. It should be noted that each capacity is the capacity per unit mass of the NCM as the positive electrode active material.

[0139] [Table 4]

[0140]

[0141] The discharge capacity of the non-aqueous electrolyte secondary battery after charging decreases due to self-discharge and increase in irreversible capacity, especially at high temperatures more than at low temperatures. This is the reason why the discharge capacity after storage is smaller than the charge capacity before storage in Tables 3 and 4. It can be seen that the batteries of Examples 9 to 16 and Examples 17 to 24 using the electrodes of Examples 1 to 8 have less reduction in discharge capacity after storage relative to the charge capacity before storage than the batteries of Comparative Examples 4 to 6 and Comparative Examples 7 to 9, and have excellent power storage characteristics at high temperatures.

Claims

1. A sulfur-modified polyacrylonitrile, wherein: The total sulfur content is 30% to 55% by mass, and the value of the following calculation formula (1) is less than 0.

08. Calculation formula (1): E1 / (E1+E2+E3)(1) In the formula, E1, E2 and E3 are respectively 32 +2F 64 The value of F 32 and F 64 and m / z=32 and m / z=64, respectively, when the sulfur-modified polyacrylonitrile is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C. E1 represents the F fragment ion intensities at a measurement temperature range of 55°C or higher and less than 270°C. 32 +2F 64 E2 indicates that the measurement temperature range is 270°C or higher and less than 570°C. 32 +2F 64 E3 indicates that the F value is within the measurement temperature range of 570°C or higher and 1000°C or lower. 32 +2F 64 The value of .

2. The sulfur-modified polyacrylonitrile according to claim 1, wherein The value of the following calculation formula (2) is less than 0.

50. Calculation formula (2): E2 / (E1+E2+E3)(2) In the formula, E1, E2 and E3 are respectively 32 +2F 64 The value of F 32 and F 64 and m / z=32 and m / z=64, respectively, when the sulfur-modified polyacrylonitrile is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C. E1 represents the F fragment ion intensities at a measurement temperature range of 55°C or higher and less than 270°C. 32 +2F 64 E2 indicates that the measurement temperature range is 270°C or higher and less than 570°C. 32 +2F 64 E3 indicates that the F value is within the measurement temperature range of 570°C or higher and 1000°C or lower. 32 +2F 64 The value of .

3. An electrode active material comprising the sulfur-modified polyacrylonitrile according to claim 1 or 2. 4 . An electrode for a secondary battery, comprising the electrode active material according to claim 3 . 5 . A non-aqueous electrolyte secondary battery using the secondary battery electrode according to claim 4 as a positive electrode. 6 . A non-aqueous electrolyte secondary battery, comprising the secondary battery electrode according to claim 4 as a negative electrode.

7. A method for producing an electrode for a non-aqueous electrolyte secondary battery, the electrode for a non-aqueous electrolyte secondary battery comprising an electrode active material containing sulfur-modified polyacrylonitrile, the method for producing an electrode for a non-aqueous electrolyte secondary battery comprising: In the analysis step, sulfur-modified polyacrylonitrile having a total sulfur content of 30% to 55% by mass is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C; as well as In a sorting step 1, sulfur-modified polyacrylonitrile having a value of the following calculation formula (1) of less than 0.08 is sorted as an electrode active material for an electrode for a non-aqueous electrolyte secondary battery, Calculation formula (1): E1 / (E1+E2+E3)(1) In the formula, E1, E2 and E3 are respectively 32 +2F 64 The value of F 32 and F 64 and m / z=32 and m / z=64, respectively, when the sulfur-modified polyacrylonitrile is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C. E1 represents the F fragment ion intensities at a measurement temperature range of 55°C or higher and less than 270°C. 32 +2F 64 E2 indicates that the measurement temperature range is 270°C or higher and less than 570°C. 32 +2F 64 E3 indicates that the F value is within the measurement temperature range of 570°C or higher and 1000°C or lower. 32 +2F 64 The value of .

8. A method for producing an electrode for a non-aqueous electrolyte secondary battery, comprising: In the analysis step, sulfur-modified polyacrylonitrile having a total sulfur content of 30% to 55% by mass is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C; A sorting step 1, sorting sulfur-modified polyacrylonitrile having a value of the following calculation formula (1) of less than 0.08 as an electrode active material for an electrode for a non-aqueous electrolyte secondary battery; as well as A sorting step 2 is to sort the sulfur-modified polyacrylonitrile having a value of the following calculation formula (2) less than 0.50 from the sulfur-modified polyacrylonitrile sorted in the sorting step 1 as an electrode active material for an electrode for a non-aqueous electrolyte secondary battery, Calculation formula (1): E1 / (E1+E2+E3)(1) Calculation formula (2): E2 / (E1+E2+E3)(2) In the formula, E1, E2 and E3 are respectively 32 +2F 64 The value of F 32 and F 64 and m / z=32 and m / z=64, respectively, when the sulfur-modified polyacrylonitrile is subjected to thermal desorption mass analysis based on an electron ionization method at a heating rate of 60°C / min and a measurement temperature range of 55°C to 1000°C. E1 represents the F fragment ion intensities at a measurement temperature range of 55°C or higher and less than 270°C. 32 +2F 64 E2 indicates that the measurement temperature range is 270°C or higher and less than 570°C. 32 +2F 64 E3 indicates that the F value is within the measurement temperature range of 570°C or higher and 1000°C or lower. 32 +2F 64 The value of .

9. An application, which is the application of the sulfur-modified polyacrylonitrile as claimed in claim 1 or 2 as an electrode active material.

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