Method for producing carbon-composited sulfur polymer for positive electrode of lithium-sulfur secondary battery

Abstract

To provide a method for producing a carbon-composited sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, the carbon-composited sulfur polymer giving a lithium-sulfur secondary battery excellent in battery capacity characteristics and cycle life characteristics and having high flexibility.SOLUTION: There is provided a method for producing a carbon-composited sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, the method including: a first step of adding sulfur, a crosslinking agent, and a catalyst as reaction materials into a reaction vessel; a second step of heating sulfur while stirring the reaction materials to melt the sulfur, and then adding a carbon material into the reaction materials in a fluid state while stirring the reaction materials, to obtain a carbon-material-mixed reaction material; and a third step of reacting the carbon-material-mixed reaction material at 120-220°C to obtain the carbon-composited sulfur polymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a carbon-composite sulfur polymer for use in a positive electrode of a lithium-sulfur secondary battery, which is obtained by reacting sulfur with a crosslinking agent to form a composite with a carbon material. [Background technology]

[0002] Sulfur polymers are obtained by reacting sulfur with a crosslinking agent to polymerize sulfur using the crosslinking agent, and are currently used in a variety of applications or are expected to be used in a variety of applications.

[0003] One application of sulfur polymers is as a cathode material for lithium-sulfur secondary batteries. These lithium-sulfur secondary batteries are expected to be the next generation of storage batteries because they use sulfur, which is a resource that is abundant, as the cathode material and have a high theoretical capacity (1672 mAh / g). However, one of the challenges in commercializing lithium-sulfur secondary batteries is the conversion of the sulfur intermediate Li2S into the electrolyte. X The reaction intermediate Li2S is produced by copolymerizing sulfur with the cross-linking agent. X Since sulfur polymers can reduce the elution of sulfur and alleviate stress caused by the expansion and contraction of sulfur, they are suitable for use as positive electrode materials in lithium-sulfur secondary batteries.

[0004] As a sulfur polymer for use as a positive electrode material in lithium-sulfur secondary batteries, for example, Patent Document 1 discloses a positive electrode active material for lithium-sulfur secondary batteries containing a poly(S-co-triallyloxy-triazine) vulcanized polymer obtained by reacting sulfur with triallyloxy-triazine.

[0005] The cathode material for lithium-sulfur secondary batteries is required to have high battery capacity and excellent cycle characteristics as battery performance. Therefore, Patent Document 2 discloses a method for producing a sulfur / carbon composite conductive material obtained only from initial sulfur and initial carbon, which comprises the following successive steps:2 The method includes the steps of: placing 50% to 10% by weight of initial carbon (not more than 100% by weight) in a reactor under atmospheric pressure so that the sum of the respective proportions of the initial sulfur and the initial carbon reaches 100%, hermetically sealing the reactor under atmospheric pressure, and heating the reactor to a heating temperature (Tc) ranging from 125°C to 200°C without externally controlling the pressure inside the reactor, and maintaining the reactor at the heating temperature (Tc) to form the sulfur / carbon composite conductive material in powder form by heat treatment, wherein the temperature of the reactor naturally and gradually returns to ambient temperature after the heat treatment, and the heat treatment step is carried out in the presence of air. Cited Document 2 attempts to embed a carbonaceous material in a sulfur polymer as a method for increasing the conductivity of a cathode material and improving battery capacity and cycle characteristics. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent No. 10-2103799 [Patent Document 2] Special Publication No. 2020-518536 Summary of the Invention [Problem to be solved by the invention]

[0007] Since lithium-sulfur secondary batteries are used for a long period of time through repeated charge and discharge cycles, they are required to have not only a high battery capacity but also a long life, and therefore, as an electrochemical performance, lithium-sulfur secondary batteries must have excellent cycle life characteristics.

[0008] However, for long-term use of lithium-sulfur secondary batteries, merely having excellent cycle life characteristics is not enough. In other words, lithium-sulfur secondary batteries require not only excellent cycle life characteristics but also high flexibility of the battery materials. This is because high flexibility of the battery materials can absorb shocks caused by volume expansion and contraction of the battery, improving the cycle characteristics of the lithium-sulfur battery.

[0009] Therefore, an object of the present invention is to provide a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, which provides a lithium-sulfur secondary battery with excellent battery capacity characteristics and cycle life characteristics, and to provide a method for producing a carbon-composite sulfur polymer for a highly flexible positive electrode of a lithium-sulfur secondary battery. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that, by first mixing sulfur, a crosslinking agent, and a catalyst without mixing a carbonaceous material, and then heating the mixture of sulfur, crosslinking agent, and catalyst to melt the sulfur, and then stirring the sulfur, crosslinking agent, and catalyst, the crosslinking agent and catalyst can be well dispersed in the sulfur, thereby enhancing the subsequent reactivity between the sulfur and the crosslinking agent. Furthermore, by adding a carbonaceous material to the reaction raw material in a fluid state in which the crosslinking agent and catalyst are well dispersed in the sulfur, and mixing the mixture with stirring, the carbonaceous material can be well dispersed in the sulfur polymer. These findings have led to the completion of the present invention.

[0011] That is, the present invention (1) comprises a first step of adding sulfur, a crosslinking agent, and a catalyst as reaction raw materials to a reaction vessel; a second step of heating and melting sulfur while stirring the reaction raw material, and then adding a carbonaceous material to the reaction raw material in a fluidized state while stirring the reaction raw material to obtain a carbonaceous material mixed reaction raw material; a third step of reacting the carbonaceous material mixed reaction raw material at 120 to 220°C to obtain a carbon-composite sulfur polymer; having The present invention provides a method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, characterized by the above-mentioned.

[0012] The present invention (2) also provides a crosslinking agent represented by the following general formula (1):

[0013] [ka]

[0014] (In the formula, R 1 , R 2 and R 3 one, two or all of the R 1 , R 2 and R 3 When one or two of the groups are an allyloxy group or a substituted allyloxy group having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms), the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkenyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen atom), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a glycidyl group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, a silyl group, and a hydrogen atom. 1 , R 2 and R 3 may be the same or different.) and / or a triazine derivative represented by the following general formula (2):

[0015] [ka]

[0016] (In the formula, R 4 , R 5 and R 6 one, two or all of the groups are substituents capable of reacting with sulfur, and the substituents capable of reacting with sulfur are selected from the group consisting of linear or branched alkenyl groups having 2 to 15 carbon atoms (which may contain a halogen element), linear or branched alkynyl groups having 2 to 15 carbon atoms (which may contain a halogen element), sulfide groups, mercapto groups, glycidyl groups, cyano groups, carbonyl groups, and linear or branched hydrocarbon groups having 1 to 15 carbon atoms and having a halogen, and R 4 , R 5 and R 6 When one or two of the above groups are substituents capable of reacting with sulfur, the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen element), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen element), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfonyl group, a silyl group, and a hydrogen atom. 4 , R 5 and R 6 may be the same or different.) The present invention provides a method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, characterized in that the carbon-composite sulfur polymer is an isocyanuric acid derivative represented by the formula (1).

[0017] The present invention (3) also provides the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to (1) or (2), characterized in that in the second step, the temperature of the reaction raw materials is 120 to 220°C when the addition of the carbon material to the reaction raw materials is started.

[0018] The present invention (4) also provides the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to any one of (1) to (3), characterized in that in the second step, the time from starting the addition of the carbonaceous material to the reaction raw materials to finishing the addition of the carbonaceous material to the reaction raw materials is 0 to 15 minutes.

[0019] The present invention (5) also provides the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to any one of (1) to (4), characterized in that in the first step, the amount of the crosslinking agent added is 5.0 to 100.0 parts by mass per 100.0 parts by mass of the sulfur.

[0020] The present invention (6) also provides the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to any one of (1) to (5), characterized in that the amount of the carbon material added in the second step is 1.0 to 30.0 parts by mass per 100.0 parts by mass of the total of the sulfur and the crosslinking agent.

[0021] The present invention (7) also provides the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to any one of (1) to (6), characterized in that in the third step, the heating temperature of the carbonaceous material mixed reaction raw material is 120 to 220°C.

[0022] The present invention (8) also provides a method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to any one of (1) to (7), characterized in that the carbon material is powdered carbon. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a method for producing a highly flexible carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, which provides a lithium-sulfur secondary battery with excellent battery capacity characteristics and cycle life characteristics. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram showing charge-discharge curves of the carbon-composite sulfur polymer of Example 1. [Figure 2] FIG. 1 is a graph showing the charge / discharge curve (30 cycles) of an electrode prepared using the carbon-composite sulfur polymer of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0025] The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery of the present invention includes a first step of adding sulfur, a crosslinking agent, and a catalyst as reaction raw materials to a reaction vessel; a second step of heating and melting sulfur while stirring the reaction raw material, and then adding a carbonaceous material to the reaction raw material in a fluidized state while stirring the reaction raw material to obtain a carbonaceous material mixed reaction raw material; a third step of reacting the carbonaceous material mixed reaction raw material at 120 to 220°C to obtain a carbon-composite sulfur polymer; having The present invention relates to a method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, the method comprising the steps of:

[0026] The first step in the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery of the present invention is a step of adding sulfur, a crosslinking agent, and a catalyst as reaction raw materials to a reaction vessel.

[0027] The sulfur (sulfur molecules) used in the first step are a raw material for sulfur polymers and typically exist as cyclic molecules of S8. When the raw material sulfur (sulfur molecules) is heated or heated in the presence of a catalyst, a portion of the molecular chain is cleaved, resulting in ring-opening, or further cleavage of the molecular chain after ring-opening produces a linear sulfur chain of 8 atoms or less. The raw material sulfur (sulfur molecules) is not particularly limited and may be produced from any raw material or by any production method. The crystalline form of sulfur is not particularly limited and may be any of α-sulfur (orthorhombic sulfur), β-sulfur (monoclinic sulfur), γ-sulfur (monoclinic sulfur), or a mixture thereof.

[0028] The crosslinking agent in the first step is a raw material for a sulfur polymer, and is a crosslinking agent for crosslinking the raw material sulfur (sulfur molecules) to form a sulfur polymer.

[0029] Examples of the crosslinking agent in the first step include a crosslinking agent represented by the following general formula (1):

[0030] [ka]

[0031] (In the formula, R 1 , R 2 and R 3 one, two or all of the R 1 , R 2 and R 3 When one or two of the groups are an allyloxy group or a substituted allyloxy group having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms), the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkenyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen atom), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a glycidyl group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, a silyl group, and a hydrogen atom. 1 , R 2 and R 3 may be the same or different.) a triazine derivative represented by the following general formula (2):

[0032] [ka]

[0033] (In the formula, R 4 , R 5 and R 6 one, two or all of the groups are substituents capable of reacting with sulfur, and the substituents capable of reacting with sulfur are selected from the group consisting of linear or branched alkenyl groups having 2 to 15 carbon atoms (which may contain a halogen element), linear or branched alkynyl groups having 2 to 15 carbon atoms (which may contain a halogen element), sulfide groups, mercapto groups, glycidyl groups, cyano groups, carbonyl groups, and linear or branched hydrocarbon groups having 1 to 15 carbon atoms and having a halogen, and R 4 , R 5 and R 6 When one or two of the above groups are substituents capable of reacting with sulfur, the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen element), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen element), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfonyl group, a silyl group, and a hydrogen atom. 4 , R 5 and R 6 may be the same or different.) Examples of the isocyanuric acid derivatives include those represented by the following formula:

[0034] In general formula (1), R 1 , R 2 and R 3 is any one of the following (i) to (iii), and among these, (i) is preferred. (i) All of R1, R2 and R3 are allyloxy groups or substituted allyloxy groups having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms). (ii)R 1 , R 2 and R 3Among these, two are allyloxy groups or substituted allyloxy groups having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms), and one is a group selected from the group consisting of a linear or branched alkyl group having 1 to 15, preferably 1 to 10, carbon atoms (which may contain a halogen atom), a linear or branched alkenyl group having 2 to 15, preferably 2 to 10, carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15, preferably 2 to 10, carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15, preferably 2 to 10, carbon atoms (which may contain a halogen atom), a linear or branched alkoxy group having 2 to 15, preferably 2 to 10, carbon atoms (which may contain a halogen atom), an aryl group having 6 to 20, preferably 6 to 10, carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a glycidyl group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, a silyl group, and a hydrogen atom. (iii)R 1 , R 2 and R 3 and two are groups selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms (which may contain a halogen atom), a linear or branched alkenyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen atom), a linear or branched alkoxy group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen atom), an aryl group having 6 to 20 carbon atoms, preferably 6 to 10 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a glycidyl group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, a silyl group, and a hydrogen atom. In addition, R 1 , R 2 and R 3may be the same or different. Furthermore, a substituted allyloxy group having 4 to 15 carbon atoms refers to an allyloxy group in which hydrogen atoms are substituted with an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms. Furthermore, "optionally containing a halogen element" refers to both a group in which none of the hydrogen atoms in the group are substituted with a halogen atom, and a group in which some of the hydrogen atoms in the group are substituted with a halogen atom. For example, the allyloxy group includes a 2-propen-1-yloxy group (allyloxy group), the alkyl group includes a methyl group, the alkoxy group includes an oxyethanol group, the aryl group includes a phenyl group, and the glycidyl group includes a 2-oxiranylmethoxy group.

[0035] The triazine derivative represented by the general formula (1) includes the following formula (1A):

[0036] [ka]

[0037] Examples of the triazine derivatives represented by the general formula (1) include 2,4,6-tris(allyloxy)-1,3,5-triazine represented by the following general formula (1): 2-methyl-4,6-bis(2-propen-1-yloxy)-1,3,5-triazine, 2,4-bis(2-propen-1-yloxy)-6-(2-propyn-1-yloxy)-1,3,5-triazine, 2-[[4,6-bis(2-propen-1-yloxy)-1,3,5-triazin-2-yl]oxy]ethanol, 2-phenyl-4,6-bis(2-propen-1-yloxy)-1,3,5-triazine, and 2-(2-oxiranylmethoxy)-4,6-bis(2-propen-1-yloxy)-1,3,5-triazine.

[0038] In general formula (2), R 4 , R 5 and R 6 is any one of the following (i) to (iii), and among these, (i) is preferred. (i)R 4 , R5 and R 6 are all substituents capable of reacting with sulfur, that is, groups selected from the group consisting of straight-chain or branched alkenyl groups (which may contain a halogen element) having 2 to 15, preferably 2 to 10, and particularly preferably 3, carbon atoms, straight-chain or branched alkynyl groups (which may contain a halogen element) having 2 to 15 carbon atoms, sulfide groups, mercapto groups, glycidyl groups, cyano groups, carbonyl groups, and straight-chain or branched hydrocarbon groups having 1 to 15 carbon atoms and containing a halogen. (ii)R 4 , R 5 and R 6 Among these, two are substituents capable of reacting with sulfur, that is, groups selected from the group consisting of straight-chain or branched alkenyl groups (which may contain a halogen element) having 2 to 15 carbon atoms, preferably 2 to 10, and particularly preferably 3 carbon atoms, straight-chain or branched alkynyl groups (which may contain a halogen element) having 2 to 15 carbon atoms, sulfide groups, mercapto groups, glycidyl groups, cyano groups, carbonyl groups, and straight-chain or branched hydrocarbon groups having 1 to 15 carbon atoms and having a halogen, and one is a group selected from the group consisting of straight-chain or branched alkyl groups (which may contain a halogen element) having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, straight-chain or branched alkoxy groups (which may contain a halogen element) having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, aryl groups having 6 to 20 carbon atoms, preferably 6 to 10 carbon atoms, amino groups, amido groups, imino groups, carboxyl groups, hydroxyl groups, ester groups, nitro groups, nitrile groups, sulfonyl groups, silyl groups, and hydrogen atoms. (iii)R 4 , R 5 and R 6one of them is a substituent capable of reacting with sulfur, that is, a group selected from the group consisting of a linear or branched alkenyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, and particularly preferably 3 carbon atoms (which may contain a halogen element), a linear or branched alkynyl group having 2 to 15 carbon atoms (which may contain a halogen element), a sulfide group, a mercapto group, a glycidyl group, a cyano group, a carbonyl group, and a linear or branched hydrocarbon group having 1 to 15 carbon atoms and which has a halogen; and two of them are groups selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms (which may contain a halogen element), a linear or branched alkoxy group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen element), an aryl group having 6 to 20 carbon atoms, preferably 6 to 10 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfonyl group, a silyl group, and a hydrogen atom. In addition, R 4 , R 5 and R 6 may be the same or different. Furthermore, the term "sulfur-reactive substituent" refers to a group that can react with sulfur in a crosslinking reaction with sulfur by heating in the presence of a catalyst such as a dithiocarbamate catalyst, and examples thereof include a linear or branched alkenyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen element), a linear or branched alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms (which may contain a halogen element), a sulfide group, a mercapto group, a glycidyl group, a cyano group, a carbonyl group, and a linear or branched hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, which has a halogen. Furthermore, "which may contain a halogen element" refers to both groups in which no hydrogen atoms are substituted with halogen atoms and groups in which some of the hydrogen atoms are substituted with halogen atoms. For example, examples of the alkyl group include a methyl group or a chloromethyl group, examples of the alkenyl group include a 2-propen-1-yl group (allyl group), a 2-methyl-2-propen-1-yl group, or a 2-buten-1-yl group, examples of the alkynyl group include an ethynyl group, examples of the alkoxy group include a 2-hydroxyethyl group, and examples of the mercapto group include a 2-mercaptoethyl group.

[0039] The isocyanuric acid derivative represented by the general formula (2) includes the isocyanuric acid derivative represented by the following formula (2A):

[0040] [ka]

[0041] Examples of the isocyanuric acid derivatives represented by the general formula (2) include 1-(2-methyl-2-propen-1-yl)-3,5-di-2-propen-1-yl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1-methyl-3,5-di-2-propen-1-yl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3-di-2-buten-1-yl-5-methyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1-(chloromethyl)-3,5-di-2-propen-1-yl-1,3,5-triazine-2, 4,6(1H,3H,5H)-trione, 1,3-di-2-buten-1-yl-5-methyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-triethynyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1-(2-hydroxyethyl)-3,5-di-2-propen-1-yl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1-(2-mercaptoethyl)-3,5-di-2-propyn-1-yl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0042] Examples of the crosslinking agent used in the first step include 2,4,6-tris(allyloxy)-1,3,5-triazine and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0043] The crosslinking agent in the first step is preferably a triazine derivative represented by general formula (1) and / or an isocyanuric acid derivative represented by general formula (2), more preferably a triazine derivative represented by general formula (1). When the crosslinking agent in the first step is a combination of a triazine derivative represented by general formula (1) and an isocyanuric acid derivative represented by general formula (2), the proportion of the triazine derivative represented by general formula (1) to the total of the triazine derivative represented by general formula (1) and the isocyanuric acid derivative represented by general formula (2) is preferably 50.0 to 100.0 mass%, more preferably 80.0 to 100.0 mass%.

[0044] The catalyst for the first step is a catalyst for promoting the reaction between sulfur and a crosslinking agent. Examples of the catalyst for the first step include dithiocarbamate catalysts. Dithiocarbamate catalysts are represented by the general formula (3): R 7 R 8 NCS2 - (3) In general formula (3), R is a salt of an anion represented by the formula (3) and a metal cation. 7 and R 8 R is a straight or branched alkyl group having 1 to 6 carbon atoms, preferably a straight alkyl group having 1 to 3 carbon atoms, and specific examples thereof include methyl, ethyl, and propyl. 7 and R 8may have the same structure or different structures. Examples of metal cations that serve as counter cations to the anions represented by general formula (3) include zinc ions, sodium ions, silver ions, iron ions, ammonium ions, cobalt ions, nickel ions, copper ions, lithium ions, and manganese ions. Examples of dithiocarbamate catalysts include zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper diethyldithiocarbamate, silver diethyldithiocarbamate, and disodium dimethyldithiocarbamate. Of these, zinc diethyldithiocarbamate and copper diethyldithiocarbamate are preferred.

[0045] Examples of the catalyst used in the first step include zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper diethyldithiocarbamate, silver diethyldithiocarbamate, and disodium dimethyldithiocarbamate.

[0046] In the first step, the amount of the crosslinking agent added is not particularly limited, but is preferably 5.0 to 100.0 parts by mass, more preferably 10.0 to 80.0 parts by mass, relative to 100.0 parts by mass of sulfur. When the amount of the crosslinking agent added is within the above range, a flexible carbon-composite sulfur polymer with a high sulfur content can be obtained.

[0047] In the first step, the amount of catalyst added is not particularly limited, but is preferably 0.10 to 5.0 parts by mass, more preferably 0.50 to 3.0 parts by mass, relative to 100.0 parts by mass of the total of sulfur and crosslinking agent. When the amount of catalyst added is within the above range, the carbon-composite sulfur polymer can be obtained in good yield.

[0048] In the first step, the method for adding sulfur, a crosslinking agent, and a catalyst to a reaction vessel is not particularly limited, and for example, sulfur, a crosslinking agent, and a catalyst may be added separately to the reaction vessel, or sulfur, a crosslinking agent, and a catalyst may be mixed in advance in different vessels and then added to the reaction vessel. In addition, in the first step, after adding sulfur, a crosslinking agent, and a catalyst to the reaction vessel, these reaction raw materials may be stirred and mixed before starting heating of the reaction raw materials in the second step, or heating of the reaction raw materials may be started in the second step without stirring and mixing of the reaction raw materials.

[0049] The second step in the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery of the present invention is a step of heating the reaction raw materials in a reaction vessel while stirring them, and then adding a carbon material to the reaction raw materials in a fluidized state to obtain a carbon material-mixed reaction raw material.

[0050] In the second step, the reaction raw materials in the reaction vessel are first heated while stirring to melt the sulfur, and then the sulfur, crosslinking agent, and catalyst are stirred and mixed in the molten sulfur state. In the second step, the temperature of the reaction raw materials when the carbonaceous material is added to the reaction raw materials is a temperature equal to or higher than the temperature at which the reaction raw materials become fluidized due to the melting of sulfur, preferably 120 to 220°C, more preferably 140 to 180°C, and particularly preferably 140 to 160°C. In the second step, before mixing the carbonaceous material with the reaction raw materials (sulfur, crosslinking agent, and catalyst), the sulfur, crosslinking agent, and catalyst are stirred and mixed in the molten sulfur state, thereby obtaining a reaction raw material with a high degree of dispersion of the crosslinking agent and catalyst in the sulfur. Therefore, in the third step, the reaction efficiency between the sulfur and the crosslinking agent in the reaction raw materials mixed with the carbonaceous material is increased, resulting in a composite material that achieves both a high conversion rate to a sulfur polymer and high dispersibility in the carbonaceous material. In the second step, by bringing the reaction raw materials to the above temperature before adding the carbonaceous material to the reaction raw materials, a small amount of reaction between sulfur and the crosslinking agent may occur. However, as long as the reaction is to an extent that does not inhibit dispersion of the carbonaceous material in the reaction raw materials, a small amount of reaction between sulfur and the crosslinking agent may occur in the reaction raw materials before adding the carbonaceous material to the reaction raw materials.

[0051] In the second step, next, in a state in which the sulfur is molten, a carbonaceous material is added to the reaction raw material in a fluidized state while stirring the reaction raw material, thereby obtaining a carbonaceous material mixed reaction raw material.

[0052] Examples of the carbon material used in the second step include conductive carbon powder such as ketjen black and acetylene black, carbon nanofiber, graphene, etc. Among these, ketjen black, acetylene black, carbon nanofiber, etc. are preferred as the carbon material.

[0053] When the carbon material is a conductive carbon powder, the primary particle size of the conductive carbon powder is preferably 0.01 to 100 μm, more preferably 0.01 to 10 μm.

[0054] In the second step, while the sulfur in the reactant is in a molten state, a predetermined amount of carbonaceous material is added to the fluidized reactant in one or multiple batches while stirring the reactant. To achieve a good dispersion, it is preferable to continue stirring after adding the predetermined amount of carbonaceous material. In the second step, the reactant is in a fluidized state when the carbonaceous material is added. Adding the carbonaceous material to the reactant while stirring the fluidized reactant results in a good dispersion of the carbonaceous material in the reactant. The reactant enters the pores of the carbonaceous material while maintaining uniformity and polymerizes, achieving both a high conversion rate and good dispersibility in the carbonaceous material. The fluidized state of the reactant refers to a state in which the viscosity of the dissolved reactant is low and can be easily stirred with a stirrer, such as a magnetic stirrer. In the second step, the viscosity of the reactant when the carbonaceous material is added can be, for example, 10,000 mPa·s or less.

[0055] In the second step, the amount of the carbon material added is not particularly limited, but is preferably 1.0 to 30.0 parts by mass, and more preferably 3.0 to 15.0 parts by mass, relative to 100.0 parts by mass of the total amount of sulfur and crosslinking agent. By adding the carbon material in the above range, a uniform composite material having a high sulfur content can be obtained.

[0056] In the second step, the temperature of the reaction raw materials when the addition of the carbonaceous material to the reaction raw materials is started varies depending on the amount of sulfur used, the crystalline state of the sulfur used as the raw material, and, if a mixture of sulfur with different crystalline states is used as the raw material, the mixing ratio thereof. Therefore, the temperature of the reaction raw materials when the addition of the carbonaceous material to the reaction raw materials is started is appropriately selected depending on the amount of sulfur used, the crystalline state of the sulfur used as the raw material, and, if a mixture of sulfur with different crystalline states is used as the raw material, the mixing ratio thereof. In the second step, the temperature of the reaction raw materials when the addition of the carbonaceous material to the reaction raw materials is started is preferably 120 to 220°C, more preferably 140 to 180°C, and particularly preferably 140 to 160°C.

[0057] In the second step, the carbonaceous material is added to the reaction raw materials while the reaction raw materials are in a fluidized state. The timing for ending the addition of the carbonaceous material to the reaction raw materials varies depending on the reaction scale, and is appropriately selected within a range in which the effects of the present invention are achieved while the reaction raw materials are in a fluidized state. In the second step, the temperature of the reaction raw materials when the addition of the carbonaceous material to the reaction raw materials is ended is preferably 120 to 220°C, more preferably 140 to 180°C, and particularly preferably 140 to 160°C. If the temperature of the reaction raw materials becomes too high in the second step, sulfur polymerization will proceed excessively, reducing the fluidity of the reaction raw materials and reducing the dispersibility of the carbonaceous material in the reaction raw materials. Therefore, in the second step, it is preferable to end the addition of the carbonaceous material to the reaction raw materials within the above temperature range.

[0058] In the second step, the time from the start of adding the carbonaceous material to the reaction raw materials to the end of adding the carbonaceous material to the reaction raw materials is preferably 0 to 15 minutes, more preferably 1 to 10 minutes, thereby obtaining a carbon-composite sulfur polymer in which the carbonaceous material is highly dispersed.

[0059] In the second step, it is preferable to add at least 50 mass % of the carbonaceous material to the reaction raw material, more preferably at least 80 mass %, and particularly preferably the entire amount, within 10 minutes from the start of adding the carbonaceous material to the reaction raw material, thereby obtaining a carbon-composite sulfur polymer in which the carbonaceous material is highly dispersible.

[0060] In the second step, it is preferable to add at least 50 mass % of the carbonaceous material to the reaction raw materials while the temperature of the raw materials is 220° C. or less, more preferably at least 80 mass %, and particularly preferably the entire amount, which results in a carbon-composite sulfur polymer in which the carbonaceous material is highly dispersible.

[0061] In the second step, it is preferable to add the entire amount of the carbonaceous material to the reaction raw materials when the viscosity of the reaction raw materials is 10,000 mPa·s or less, thereby obtaining a carbon-composite sulfur polymer in which the carbonaceous material is highly dispersible.

[0062] In the second step, the third step may be carried out immediately after the addition of the carbonaceous material to the reaction raw material is completed, or the third step may be carried out after continuing to heat the carbonaceous material mixed reaction raw material for a predetermined time.

[0063] In the second step, the carbonaceous material is added to the fluidized reactant while stirring the reactant, thereby obtaining a carbonaceous material mixed reactant.

[0064] The third step in the method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery of the present invention is a step in which the mixed reaction raw carbon material obtained by carrying out the second step is reacted at 120 to 220°C to obtain a carbon-composite sulfur polymer.

[0065] In the third step, the carbonaceous material mixed reaction raw material is reacted at 120 to 220°C, and in a state where the carbonaceous material is dispersed in a mixture of sulfur and a crosslinking agent in the carbonaceous material mixed reaction raw material, the sulfur and the crosslinking agent are reacted to produce a sulfur polymer, thereby obtaining a carbon-composite sulfur polymer in which the carbonaceous material is dispersed in the sulfur polymer.

[0066] In the third step, the reaction temperature is 120 to 220°C, more preferably 130 to 200°C. In the third step, the reaction time is not particularly limited and may be appropriately selected as long as it is within a range in which the reaction between sulfur and the crosslinking agent occurs. In the third step, the carbonaceous material mixed reaction raw material may be reacted while being stirred, or may be reacted while being left to stand.

[0067] The second and third steps may be carried out in an open air atmosphere, or may be carried out in an inert gas atmosphere such as nitrogen gas.

[0068] In this manner, the third step is carried out to obtain a carbon-composite sulfur polymer, that is, a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery in which a carbon material is dispersed in the sulfur polymer.

[0069] The carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode of the present invention is suitable for use as a positive electrode material for the lithium-sulfur secondary battery. Lithium-sulfur secondary batteries using the carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode of the present invention as a positive electrode material have a high sulfur content, are flexible, and are presumed to absorb volume expansion and contraction shocks during charge and discharge, resulting in high battery capacity and a long cycle life.

[0070] The carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode of the present invention is highly flexible, and therefore a lithium-sulfur secondary battery using the carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode of the present invention as a positive electrode material will have high durability against physical fluctuations.

[0071] In the present invention, a nanoindentation test can be used to assess the flexibility of a carbon-composite sulfur polymer for use in a lithium-sulfur secondary battery positive electrode. The nanoindentation test measures the composite elastic modulus of the carbon-composite sulfur polymer particles themselves. The carbon-composite sulfur polymer for use in a lithium-sulfur secondary battery positive electrode, obtained by the method for producing a carbon-composite sulfur polymer for use in a lithium-sulfur secondary battery positive electrode of the present invention, has a low composite elastic modulus as determined by the nanoindentation test. The lower the composite elastic modulus as determined by the nanoindentation test, the higher the flexibility.

[0072] In the carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method of the present invention for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode, the carbon material is dispersed in a sulfur polymer matrix, i.e., the sulfur polymer comprises a sulfur polymer matrix and a carbon material dispersed in the sulfur polymer matrix. The sulfur polymer is obtained by crosslinking sulfur (sulfur molecules) using a crosslinking agent, and therefore has a molecular structure in which many sulfur chains, in which sulfur atoms are linked in a linear fashion, are connected by reactive residues of the crosslinking agent. In other words, in the carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode obtained by the method of the present invention for producing a carbon-composite sulfur polymer for a lithium-sulfur secondary battery positive electrode, the sulfur polymer has many sulfur chains and reactive residues of the crosslinking agent bonded to multiple sulfur chains. [Example]

[0073] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples shown below.

[0074] Example 1 11.9 g of sulfur (Kanto Chemical Co., Ltd.), 2.1 g of TAOT (2,4,6-tris(allyloxy)-1,3,5-triazine, Sigma-Aldrich Co., Ltd.), and 0.14 g of zinc diethyldithiocarbamate (Tokyo Chemical Industry Co., Ltd.) were weighed and added to a polyfluoroalkoxy resin (PFA) container. Next, the reaction ingredients were lightly mixed with a spatula, a stirrer was placed in the container, and the mixture was heated to an oil bath temperature of 170°C while stirring with a magnetic stirrer. The time was measured starting from the point where the thermocouple in the reaction ingredients indicated 140°C. After heating for 3 minutes, the stirrer was removed. The temperature at this point was 152°C. Next, 0.74 g of Ketjenblack (porous hollow carbon black, Lion Specialty Chemicals, primary particle size 34 nm) was added and quickly mixed with a spatula. Next, the mixture was preheated at 170°C for 10 to 15 minutes while being kneaded by hand with the flat part of the spatula to mix evenly. The container was then removed from the oil bath and heated in a constant temperature oven at 140°C for 6 hours under a nitrogen stream. After heating, the container was allowed to cool naturally to room temperature under a nitrogen atmosphere to obtain a carbon-composite sulfur polymer. The obtained carbon-composite sulfur polymer was placed in an agate mortar and pre-pulverized with a pestle, and then pulverized using a freeze pulverizer (As One Corporation, HTPT-01) under liquid nitrogen freezing conditions. The pulverized product was classified using a 100 μm sieve, and particles that did not pass through the sieve were removed to obtain a pulverized carbon-composite sulfur polymer. The particle size distribution of the pulverized carbon-composite sulfur polymer obtained was measured by laser diffraction / scattering using a particle size distribution analyzer (Shimadzu Corporation, SALD-7500), and the median diameter was 30.0 μm. The sulfur content of the resulting pulverized carbon composite sulfur polymer was measured using S632 manufactured by LECO Corporation, and was found to be 74.0 mass %. The resulting pulverized carbon-composite sulfur polymer was then subjected to the following charge-discharge test and nanoindentation test, the results of which are shown in Table 1 and FIG.

[0075] <Fabrication of electrodes using carbon-composite sulfur polymers, fabrication of coin cells, and charge / discharge tests> The pulverized carbon composite sulfur polymer obtained above, acetylene black (Denka Black HS-100, manufactured by Denka Corporation), and binder (sodium carboxymethyl cellulose (CMC) (Daicel Corporation, product number 2200)) were weighed out so that the mass ratio of the sulfur polymer in the carbon composite sulfur polymer was 63%, the total of the carbon material and acetylene black in the carbon composite sulfur polymer was 32%, and the binder was 5%. Next, the carbon composite sulfur polymer pulverized product and acetylene black were placed in an agate mortar and mixed, and then a binder was added and further mixed. Next, pure water was added in several batches and mixed in the mortar. The prepared sample was mixed in a planetary centrifugal mixer (2000 rpm, 3 min) to obtain a slurry. An electrode was applied to aluminum foil with a film thickness of 200 μm and dried at 40°C for 12 hours. The obtained electrode was punched out with a φ16 hole. The punched electrode was pressed in a uniaxial press to achieve a porosity of approximately 30-40%. The prepared electrode was placed in a glass tube oven and vacuum dried at 50°C for 14 hours. Coin cells (CR2032) were fabricated by assembling electrodes made of lithium foil, a separator, and sulfur polymer in a glove box filled with high-purity argon. The electrolyte was 1M LiTFSI (Sigma-Aldrich) / 0.2M LiNO3 (Ström Chemicals) dissolved in 1,3-dioxolane (Sigma-Aldrich) / 1,2-dimethoxyethane (Kishida Chemical). Electrochemical measurements were performed using a Meiden Hokuto HJ1001SD8. Constant-current discharge / charge voltages were measured at 0.05 C (1 C - 1675 mAh / g) between 1.0 and 3.0 V at 25 °C. All discharge / charge capacities were calculated based on the weight of sulfur.

[0076] (Measurement of composite elastic modulus) <Nanoindentation test procedure and conditions> The carbon composite sulfur polymer pulverized material obtained above was embedded in epoxy resin and cross-sectioned using an ultramicrotome. Measurements were performed using a HYSITRON TI Premier Multi Scale with a Berkovich indenter (diamond), a maximum load of 250 μN, a loading / unloading time of 5 seconds, and a maximum load holding time of 2 seconds.

[0077] (Comparative Example 1) 14.0 g of sulfur (manufactured by Kanto Chemical Co., Ltd.) was weighed and added to a polyfluoroalkoxy resin (PFA) container. Next, a stirrer was placed in the container, and the mixture was heated in an oil bath at 170°C while stirring with a magnetic stirrer. The time was measured starting from the point where the thermocouple in the reaction raw material indicated 140°C. After heating for 3 minutes, the stirrer was removed. Next, 0.74 g of Ketjenblack (porous hollow carbon black, Lion Specialty Chemicals, primary particle size 34 nm) was added and quickly mixed with a spatula. Next, the mixture was preheated at 170°C for 10 to 15 minutes while being kneaded by hand with the flat part of the spatula to mix evenly. The container was then removed from the oil bath and heated in a constant temperature oven under a nitrogen stream for 6 hours. After heating, the container was allowed to cool naturally to room temperature under a nitrogen atmosphere to obtain a carbon-carbon composite sulfur. The obtained carbon composite sulfur was pulverized and classified in the same manner as in Example 1, and the particle size distribution was measured. As a result, a pulverized carbon composite sulfur product with a median particle size of 12.6 μm was obtained. The carbon composite sulfur pulverized product was then subjected to the above-mentioned charge / discharge test and nanoindentation test. The results are shown in Table 1.

[0078] (Comparative Example 2) 11.9 g of sulfur (manufactured by Kanto Chemical Co., Ltd.) and 0.14 g of zinc diethyldithiocarbamate (manufactured by Tokyo Chemical Industry Co., Ltd.) were weighed and added to a polyfluoroalkoxy resin (PFA) container. Next, these ingredients were lightly mixed with a spatula, a stirrer bar was placed in the container, and the mixture was heated to 170°C in an oil bath while stirring with a magnetic stirrer. When the thermocouple reading in the reaction mixture reached 140°C, the stirrer bar was removed, and 0.74 g of Ketjenblack (porous hollow carbon black, Lion Specialty Chemicals, primary particle size 34 nm) was added and mixed with a spatula for 1 minute. Next, 2.1 g of TAOT (2,4,6-tris(allyloxy)-1,3,5-triazine, Sigma-Aldrich) was added, and the mixture was preheated at 170°C for 10-15 minutes while being hand-kneaded with the flat part of the spatula to ensure a uniform mixture. The container was then removed from the oil bath and heated in a constant temperature oven at 140°C for 6 hours under a nitrogen stream. After the additional heating, the container was allowed to cool to room temperature under a nitrogen atmosphere to obtain a carbon-composite sulfur polymer. The obtained carbon-composite sulfur polymer was pulverized and classified in the same manner as in Example 1, and the particle size distribution was measured. As a result, a pulverized carbon-composite sulfur polymer product having a median diameter of 21.9 μm was obtained. The resulting carbon-composite sulfur polymer pulverized product was then subjected to the above-mentioned charge-discharge test and nanoindentation test. The results are shown in Table 1.

[0079] [Table 1]

Claims

1. A first step of adding sulfur, a crosslinking agent, and a catalyst as reaction raw materials to a reaction vessel; a second step of heating and melting sulfur while stirring the reaction raw material, and then adding a carbonaceous material to the reaction raw material in a fluidized state while stirring the reaction raw material to obtain a carbonaceous material mixed reaction raw material; a third step of reacting the carbonaceous material mixed reaction raw material at 120 to 220°C to obtain a carbon-composite sulfur polymer; having A method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery, characterized by:

2. The crosslinking agent is represented by the following general formula (1): 【Chemical 1】 (In the formula, R １ , R ２ and R ３ one, two or all of R are allyloxy groups or substituted allyloxy groups having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms), １ , R ２ and R ３ When one or two of the groups are an allyloxy group or a substituted allyloxy group having 4 to 15 carbon atoms (the substituent is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms), the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkenyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkynyl group having 2 to 15 carbon atoms (which may contain a halogen atom), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen atom), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a glycidyl group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, a silyl group, and a hydrogen atom. １ , R ２ and R ３ may be the same or different.) and / or a triazine derivative represented by the following general formula (2): 【Chemistry 2】 (In the formula, R ４ , R ５ and R ６ one, two or all of the groups are substituents capable of reacting with sulfur, and the substituents capable of reacting with sulfur are selected from the group consisting of linear or branched alkenyl groups having 2 to 15 carbon atoms (which may contain a halogen element), linear or branched alkynyl groups having 2 to 15 carbon atoms (which may contain a halogen element), sulfide groups, mercapto groups, glycidyl groups, cyano groups, carbonyl groups, and linear or branched hydrocarbon groups having 1 to 15 carbon atoms and having a halogen, and R ４ , R ５ and R ６ When one or two of the above groups are substituents capable of reacting with sulfur, the remaining groups are selected from the group consisting of a linear or branched alkyl group having 1 to 15 carbon atoms (which may contain a halogen element), a linear or branched alkoxy group having 2 to 15 carbon atoms (which may contain a halogen element), an aryl group having 6 to 20 carbon atoms, an amino group, an amido group, an imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfonyl group, a silyl group, and a hydrogen atom. ４ , R ５ and R ６ may be the same or different.) 2. The method for producing a carbon-sulfur polymer composite for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein the carbon-sulfur polymer composite for a positive electrode of a lithium-sulfur secondary battery is an isocyanuric acid derivative represented by the formula:

3. 2. The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein the temperature of the reaction raw materials is 120 to 220°C when the addition of the carbon material to the reaction raw materials is started in the second step.

4. 2. The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein in the second step, a time from starting to finishing adding the carbonaceous material to the reaction raw materials is 0 to 15 minutes.

5. 2. The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein the amount of the crosslinking agent added in the first step is 5.0 to 100.0 parts by mass per 100.0 parts by mass of sulfur.

6. 2. The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein the amount of the carbon material added in the second step is 1.0 to 30.0 parts by mass with respect to a total of 100.0 parts by mass of the sulfur and the crosslinking agent.

7. 2. The method for producing a carbon-composite sulfur polymer for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein in the third step, the heating temperature of the carbonaceous material mixed reaction raw material is 120 to 220°C.

8. 2. The method for producing a carbon-sulfur polymer composite for a positive electrode of a lithium-sulfur secondary battery according to claim 1, wherein the carbon material is a conductive carbon powder.

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