Electrode material

Abstract

Provided is an electrode material which is suitable for use as a material for forming electrodes for use in lithium ion secondary batteries, etc. and which makes it possible to heighten the rate characteristics of batteries. The electrode material is characterized by comprising a polymer having, in a side chain, a fluoflavin skeleton such as that shown by the formula and an inorganic active material, the polymer being contained in an amount of 1 mass% or less with respect to the solid components.

Description

electrode material

[0001] The present invention relates to an electrode material containing a polymer having a fluofuravin skeleton in the side chain.

[0002] In recent years, electronic devices have become smaller and lighter, and this has led to a demand for smaller and lighter batteries as their power sources. Non-aqueous electrolyte secondary batteries such as lithium-ion batteries have been put to practical use as small, lightweight, high-capacity, rechargeable batteries, and are used in portable electronic devices and communication devices such as small video cameras, mobile phones, and laptop computers.

[0003] Lithium-ion secondary batteries have excellent advantages, such as high energy density, higher capacity, and higher operating voltage than other batteries. However, due to their high energy density, they are at risk of overheating and fire depending on the conditions of use, so high safety standards are required. In particular, hybrid vehicles, which have recently been attracting attention, require higher energy density and output characteristics, making even higher safety standards necessary.

[0004] Generally, lithium-ion secondary batteries are composed of a positive electrode, a negative electrode, and an electrolyte. During charging, lithium ions escape from the positive electrode active material into the electrolyte and are inserted into the negative electrode active material, such as carbon particles. During discharging, lithium ions escape from the negative electrode active material into the electrolyte and are inserted into the positive electrode active material, allowing current to be extracted to an external circuit. In this way, charging and discharging occur within the lithium-ion secondary battery as lithium ions move back and forth between the positive and negative electrodes via the electrolyte.

[0005] Meanwhile, with the improvement in performance of portable electronic devices and the like, batteries with higher capacities are in demand, and active research is being conducted on negative electrode active materials such as Sn and Si, which have much higher capacities per unit weight than existing carbon. However, when Si or Si alloys are used as negative electrode active materials, there is a problem of large volume expansion and poor cycle characteristics. To solve this problem, graphite is mixed, but if the graphite is unevenly distributed during mixing, the cycle characteristics (lifespan) may be reduced.

[0006] In recent years, further improvements in rate characteristics are being demanded as lithium-ion secondary batteries are increasingly used in a variety of applications, such as as high-output power sources for plug-in hybrid vehicles, hybrid vehicles, power tools, etc. Batteries used as these high-output power sources are required to be able to charge and discharge at high speeds.

[0007] The theoretical capacity of currently available positive electrode active materials is significantly lower than that of negative electrode active materials. Therefore, to achieve high capacity and high power output in lithium-ion batteries, it is necessary to impart high electrical and ionic conductivity to the positive electrode. To improve the electronic conductivity of the positive electrode, a method of adding a carbon material to the electrode as a conductive additive has been used. Examples of such carbon materials include graphite, acetylene black, and ketjen black. Recently, the use of carbon nanotubes and graphene has been reported. However, increasing the amount of such conductive additive reduces the amount of active material in the electrode, resulting in a decrease in battery capacity.

[0008] Furthermore, in order to enhance the electronic conductivity of electrode materials, electrode materials have been proposed in which the particle surface of an electrode active material is coated with an organic compound that serves as a carbon source, and then the organic compound is carbonized to form a carbonaceous coating on the surface of the electrode active material, with the carbon of this carbonaceous coating interposed as an electronic conductive material (e.g., Patent Document 1). However, the carbonization process requires prolonged heat treatment at high temperatures of 500°C or higher in an inert gas atmosphere, which reduces the capacity of the electrode. Furthermore, since the carbonization process involves heating at high temperatures of 500-800°C in a reducing or inert atmosphere, there is a possibility that the positive electrode active material itself may be reduced. Therefore, usable positive electrode active materials have been limited to lithium iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, lithium manganese phosphate, etc. For other positive electrode active materials, the carbon source has been limited to conductive polymer materials. As such, materials suitable for improving the electronic conductivity of electrode materials are still limited, and further improvements are desired.

[0009] Japanese Patent Application Laid-Open No. 2001-15111

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrode material that can be suitably used as a material for forming electrodes used in lithium ion secondary batteries and the like, and that can improve the rate characteristics of the batteries.

[0011] As a result of extensive research to achieve the above object, the inventors have found that a battery manufactured using an electrode material containing a small amount of a polymer having a fluoroflavin skeleton in its side chain and an inorganic active material has excellent rate characteristics, and have completed the present invention.

[0012] That is, the present invention provides the following electrode materials: 1. An electrode material comprising a polymer having a fluoroflavin skeleton in a side chain and an inorganic active material, wherein the polymer accounts for 1 mass % or less of the solid content. 2. The electrode material of 1, wherein the polymer is a polymer containing a repeating unit represented by the following formula (1): [wherein Z is a group represented by the following formula (Z-1), (Z-2) or (Z-3): (In the formula, R M represents a hydrogen atom or a methyl group; Y represents a single bond, —O—, —CO—, —COO—, —OCO—, —CH—, —NH—, —NCH—, —NHCO—, —CONH—, —CHNHCO—, —CONHCH—, or —S—; R 1 each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carboxy group, an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms which may be substituted with a halogen atom, and * represents a bond.] 3. An electrode material according to 2, wherein the above Z is a partial structure represented by formula (Z-1). 4. The above R 1are all hydrogen atoms. 5. The electrode material of any one of 1 to 3, wherein Y is a single bond. 6. The electrode material of 5, wherein the inorganic active material is at least one selected from metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides, and metal nitrides. 7. The electrode material of any one of 1 to 6, further comprising a solvent. 8. The electrode material of any one of 1 to 7, further comprising a conductive additive and a binder. 9. An electrode having an active material layer made of any one of the electrode materials of 1 to 8. 10. A secondary battery comprising the electrode of 9. 11. A polymer comprising a repeating unit represented by the following formula (1): [wherein Z is a group represented by the following formula (Z-1), (Z-2) or (Z-3): (In the formula, R M represents a hydrogen atom or a methyl group), Y represents a single bond, -O-, -CO-, -COO-, -OCO-, -CH2-, -NH-, -NCH3-, -NHCO-, -CONH-, -CH2NHCO-, -CONHCH2-, or -S- (provided that when Z is a partial structure represented by formula (Z-1), it is not -CH2NHCO-, and when Z is a partial structure represented by formula (Z-2), it is not a single bond), R 1 each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carboxy group, an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms which may be substituted with a halogen atom, and * represents a bond.] 12. A polymer according to 11, wherein the Z is a partial structure represented by formula (Z-1). 13. A polymer according to 11, wherein the R 1 14. A polymer according to any one of 11 to 13, wherein Y is a single bond.

[0013] By using the electrode material of the present invention, a battery with excellent rate characteristics can be provided.

[0014] 1 is a CP-MS spectrum of polymer A obtained in Example 1-1. It is a cyclic voltammogram of the polymer lithium secondary battery produced in Example 2. It is a graph showing the measurement results of the potential difference with a reference electrode when the charge / discharge capacity of the polymer lithium secondary battery produced in Example 2 is changed. It is a diagram showing the charge / discharge cycle characteristics of the polymer lithium secondary battery produced in Example 2.

[0015] The electrode material of the present invention is characterized by comprising a polymer having a fluorofuravin skeleton in its side chain (hereinafter referred to as a "fluorofuravin skeleton-containing polymer" or simply as a "polymer") and an inorganic active material, with the polymer accounting for 1 mass % or less of the solid content. In the present invention, by using the fluorofuravin skeleton-containing polymer in combination with an inorganic active material, a battery with excellent rate characteristics and cycle characteristics can be obtained even with a small amount of addition. Note that the solid content here refers to components other than the solvent contained in the electrode material of the present invention.

[0016] The fluorofuravin skeleton-containing polymer is not particularly limited as long as it has a fluorofuravin skeleton in the side chain, but in the present invention, a polymer containing a repeating unit represented by the following formula (1) is preferred.

[0017]

[0018] In the formula, Z represents the following formula (Z-1), (Z-2) or (Z-3): (In the formula, * represents a bond. R M is a hydrogen atom or a methyl group.) Among these, the partial structure represented by the above formula (Z-1) is preferred.

[0019] Y represents a single bond, -O-, -CO-, -COO-, -OCO-, -CH2-, -NH-, -NCH3-, -NHCO-, -CONH-, -CH2NHCO-, -CONHCH2-, or -S-. When Z is a partial structure represented by formula (Z-1) or (Z-3), Y is preferably a single bond. Furthermore, when Z is a partial structure represented by formula (Z-2), Y is preferably -COO-.

[0020] R1 each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carboxy group, an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms which may be substituted with a halogen atom.

[0021] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0022] Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups. Among these, alkyl groups having 1 to 5 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred.

[0023] Examples of alkoxy groups having 1 to 10 carbon atoms include methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentoxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, and n-decyloxy. Among these, alkoxy groups having 1 to 5 carbon atoms are preferred, and alkoxy groups having 1 to 3 carbon atoms are more preferred.

[0024] Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-biphenylyl group, and a 2-biphenylyl group. Of these, a phenyl group is preferred.

[0025] In the alkyl group, alkoxy group, and aryl group, some or all of the hydrogen atoms may be substituted with halogen atoms, including those exemplified above.

[0026] In the present invention, the above R 1 is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom.

[0027] RM represents a hydrogen atom or a methyl group, preferably a hydrogen atom.

[0028] The repeating unit represented by formula (1) is preferably one represented by the following formula (1-1).

[0029] (Wherein Z, Y and R 1 is the same as above.)

[0030] More preferred embodiments of the repeating unit represented by formula (1) include, but are not limited to, those represented by the following formulas (2-1) to (2-3).

[0031] (In the formula, R 1 and R M is the same as above.)

[0032] Specific preferred examples of the repeating unit represented by formula (1) include those represented by the following formulae (3-1) to (3-3), but are not limited thereto.

[0033]

[0034] The weight-average molecular weight of the fluoroflavin skeleton-containing polymer is typically 1,000 to 500,000, preferably 2,000 to 200,000. By setting the weight-average molecular weight at or below the upper limit of the above range, the polymer can be easily dissolved in a solvent when preparing an electrode slurry (active material layer-forming composition) using the polymer. Furthermore, by setting the weight-average molecular weight at or above the lower limit of the above range, the polymer can be prevented from dissolving in an electrolyte when a battery is manufactured using an electrode in which an active material layer is formed using the electrode slurry. In the present invention, the weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0035] The amount of the fluoroflavin skeleton-containing polymer blended is 1% by mass or less of the solid content, and from the viewpoint of effectively improving the rate characteristics and cycle characteristics of the resulting secondary battery, it is preferably 0.01 to 0.8% by mass, more preferably 0.05 to 0.5% by mass.

[0036] It is believed that the excellent effect achieved when the polymer is used in combination with an inorganic active material, even with such a small amount, is due to the polymer's own charge storage ability. In the present invention, "having charge storage ability" means that a secondary battery equipped with an electrode using only a fluorofuravin skeleton-containing polymer with charge storage ability as the active material provides a discharge capacity of 10 mAh / g or more. From the viewpoint of improving rate characteristics and cycle characteristics, this discharge capacity is preferably 30 mAh / g or more, and more preferably 45 mAh / g or more. The upper limit is not particularly limited, but is typically 200 mAh / g or less, taking into account deterioration during cycling. In the present invention, the discharge capacity within the above range results in less decrease in charge capacity compared to when a compound that does not have capacity by itself is added.

[0037] When synthesizing a polymer containing a repeating unit represented by formula (3-1) as the fluorofuravin skeleton-containing polymer, for example, the method shown in Scheme 1 below can be used.

[0038] (In the formula, X 1 represents a halogen atom.)

[0039] In Scheme 1, first, a fluorofuravin derivative (10) having a halogen atom and 2,5-norbornadiene (11) are reacted in a solvent in the presence of a catalyst to synthesize a fluorofuravin skeleton-containing monomer (12) (first step). The resulting monomer (12) is then polymerized in a solvent in the presence of a catalyst (second step), thereby synthesizing a fluorofuravin skeleton-containing polymer (3-1). The fluorofuravin derivative (10) can be synthesized according to a known synthesis method. For example, the synthesis method can be described with reference to the method described in Journal of Photochemistry and Photobiology A: Chemistry 198 (2008) 60-68.

[0040] Examples of the fluofuravin derivative (10) include, but are not limited to, 2-chloro-5,11-dihydroquinoxalino[2,3-b]quinoxaline and 2-bromo-5,11-dihydroquinoxalino[2,3-b]quinoxaline.

[0041] The solvent used in the first step is not particularly limited as long as it can disperse or dissolve the raw materials used. Examples of such solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, acetonitrile, acetone, alcohols (methanol, ethanol, 1-propanol, 2-propanol, etc.), glycols (ethylene glycol, triethylene glycol, etc.), cellosolves (ethyl cellosolve, methyl cellosolve, etc.), polyhydric alcohols (glycerin, pentaerythritol, etc.), tetrahydrofuran, toluene, ethyl acetate, butyl acetate, benzene, toluene, xylene, pentane, hexane, heptane, chlorobenzene, dichlorobenzene, trichlorobenzene, hexadecane, benzyl alcohol, and oleylamine. Among these, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred from the viewpoints of reaction temperature and reaction concentration. These solvents may be selected appropriately depending on the raw materials used. The above solvents may be used alone or in combination of two or more.

[0042] Examples of the catalyst used in the first step include copper catalysts such as copper chloride, copper bromide, and copper iodide; and palladium catalysts such as Pd(PPh) (tetrakis(triphenylphosphine)palladium), Pd(PPh)Cl (bis(triphenylphosphine)dichloropalladium), Pd(dba) (bis(dibenzylideneacetone)palladium), Pd(dba) (tris(dibenzylideneacetone)dipalladium), Pd(P-t-Bu) (bis(tri(t-butylphosphine))palladium), and Pd(OAc) (palladium acetate). These catalysts may be used alone or in combination of two or more. These catalysts may also be used together with known appropriate ligands. Examples of such a ligand include tertiary phosphines such as triphenylphosphine, tri-o-tolylphosphine, diphenylmethylphosphine, phenyldimethylphosphine, trimethylphosphine, triethylphosphine, tributylphosphine, tri-t-butylphosphine, di-t-butyl(phenyl)phosphine, di-t-butyl(4-dimethylaminophenyl)phosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, and 1,1′-bis(diphenylphosphino)ferrocene; and tertiary phosphites such as trimethyl phosphite, triethyl phosphite, and triphenyl phosphite.

[0043] The amount of the catalyst used can be about 0.01 to 0.2 moles, preferably about 0.02 to 0.1 moles, per mole of the fluoroflavin derivative represented by formula (10). When a ligand is used, the amount thereof can be 0.1 to 5 equivalents, preferably 1 to 2 equivalents, relative to the metal complex (catalyst) used.

[0044] In the first step, a base may be used, and examples of the base that can be used include sodium hydride, pyridine, triethylamine, diisopropylethylamine, etc., with sodium hydride, pyridine, and triethylamine being preferred. The amount of the base used is preferably 1 mole to the solvent amount per mole of the fluoroflavin derivative.

[0045] The blending ratio (molar ratio) of 2,5-norbornadiene and the fluorofuravin derivative is not particularly limited, but from the viewpoint of preventing polymerization of the produced monomers, it is preferable that both components are equimolar or that 2,5-norbornadiene is in excess relative to the fluorofuravin derivative. In the present invention, the blending ratio is preferably 1 to 8 moles, more preferably 1.5 to 5 moles, per mole of the monomer.

[0046] The reaction temperature in the first stage may be set appropriately within the range from the melting point to the boiling point of the solvent used, and is particularly preferably about 0 to 200°C, and more preferably 30 to 130°C. Reflux may be performed during heating. The reaction time cannot be generally specified because it depends on the reaction temperature and the reactivity of the raw materials, but is usually about 1 to 48 hours, and when the reaction temperature is 30 to 130°C, it is generally about 10 to 30 hours. After completion of the reaction, post-treatment is carried out according to conventional methods to obtain the desired monomer that will serve as the basis for the fluorofuravin skeleton-containing polymer.

[0047] In the second step, the fluoriflavin skeleton-containing monomer (12) obtained in the first step is polymerized in a solvent. The polymerization is usually carried out by ring-opening metathesis polymerization. The conditions may be those of a conventional method, such as an olefin metathesis reaction using a Grubbs catalyst.

[0048] The solvent used in the second stage is not particularly limited as long as it can disperse or dissolve the raw materials used. Examples of such solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, acetonitrile, acetone, alcohols (methanol, ethanol, 1-propanol, 2-propanol, etc.), glycols (ethylene glycol, triethylene glycol, etc.), cellosolves (ethyl cellosolve, methyl cellosolve, etc.), polyhydric alcohols (glycerin, pentaerythritol, etc.), tetrahydrofuran, toluene, ethyl acetate, butyl acetate, benzene, toluene, xylene, pentane, hexane, heptane, chlorobenzene, dichlorobenzene, trichlorobenzene, hexadecane, benzyl alcohol, and oleylamine. Among these, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred from the viewpoints of reaction temperature and reaction concentration. These solvents may be selected appropriately depending on the raw materials used. The above solvents may be used alone or in combination of two or more.

[0049] When polymerization is carried out by ring-opening metathesis reaction, various Grubbs catalysts can be used as the catalyst, but in the present invention, a third-generation Grubbs catalyst is preferably used. The amount of the catalyst used can be about 0.005 to 0.1 mol, preferably about 0.005 to 0.05 mol, per mol of monomer.

[0050] The reaction temperature may be set appropriately within the range from the melting point to the boiling point of the solvent used, and is particularly preferably about 0 to 200°C, more preferably 20 to 100°C. Reflux may be performed during heating. The reaction time cannot be generally specified because it depends on the reaction temperature and the reactivity of the raw materials, but is usually about 1 to 48 hours, and when the reaction temperature is 20 to 100°C, it is generally about 1 to 10 hours. After completion of the reaction, post-treatment is carried out according to a conventional method to obtain the desired fluorofuravin skeleton-containing polymer.

[0051] When synthesizing a polymer containing a repeating unit represented by formula (3-2) as the fluorofuravin skeleton-containing polymer, for example, the method shown in Scheme 2 below can be used.

[0052] (In the formula, R a represents a methyl group, an ethyl group, a propyl group, or a butyl group.

[0053] In Scheme 2, first, a fluofuravin skeleton-containing polymer monomer (22) is synthesized by transesterification of 2-hydroxy-5,11-dihydroquinoxalino[2,3-b]quinoxaline (20) with an acrylic ester compound (21) (Step 1). The resulting monomer (22) is then polymerized in solution in the presence of a catalyst (Step 2), thereby synthesizing a fluofuravin skeleton-containing polymer (3-2). The fluofuravin derivative (20) can be synthesized according to a known synthesis method. For example, the synthesis method can be described with reference to the method described in Journal of Photochemistry and Photobiology A: Chemistry 198 (2008) 60-68.

[0054] Examples of the acrylate compound (21) include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate.

[0055] The solvent used in the transesterification reaction is not particularly limited as long as it can disperse or dissolve the raw materials used. Examples of such solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, acetonitrile, acetone, alcohols (methanol, ethanol, 1-propanol, 2-propanol, etc.), glycols (ethylene glycol, triethylene glycol, etc.), cellosolves (ethyl cellosolve, methyl cellosolve, etc.), polyhydric alcohols (glycerin, pentaerythritol, etc.), tetrahydrofuran, toluene, benzene, toluene, xylene, pentane, hexane, heptane, chlorobenzene, dichlorobenzene, trichlorobenzene, hexadecane, benzyl alcohol, and oleylamine. These solvents may be selected appropriately depending on the raw materials used. The above solvents may be used alone or in combination of two or more.

[0056] In the above transesterification reaction, an appropriate acid or base can be used as a catalyst. Specific examples include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.; organic carboxylic acids such as acetic acid, propionic acid, phthalic acid, benzoic acid, etc.; organic sulfonic acids such as methylsulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, etc.; alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.; alkali metal or alkaline earth metal carbonates and hydrogen carbonates such as sodium hydrogen carbonate, potassium carbonate, calcium hydrogen carbonate, etc.

[0057] In addition, a known polymerization inhibitor may be added to the transesterification reaction. Examples of the polymerization inhibitor include phenols such as hydroquinone and hydroquinone monomethyl ether, sulfur compounds such as phenothiazine and ethylenethiourea, copper salts such as copper dibutyldithiocarbamate, manganese salts such as manganese acetate, nitro compounds, nitroso compounds, and N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl.

[0058] The transesterification reaction can be carried out by a method generally known to those skilled in the art for producing acrylic esters. During the transesterification reaction, it is necessary to azeotropically remove the by-produced lower alcohol with the lower acrylic ester and / or the solvent. For this reason, a batch reaction tank equipped with a rectification column is used as the reaction apparatus.

[0059] In the second step, the fluoroflavin skeleton-containing monomer (22) obtained in the first step is polymerized in a solvent. The polymerization method is not particularly limited and can be appropriately selected from polymerization methods commonly used in the polymerization of acrylic polymers. Examples of the polymerization method include solution polymerization, emulsion polymerization, and suspension polymerization.

[0060] When synthesizing a polymer containing a repeating unit represented by formula (3-3) as the fluorofuravin skeleton-containing polymer, for example, the method shown in Scheme 3 below can be used.

[0061] (In the formula, R b represents a methyl group, an ethyl group, an n-propyl group, or an n-butyl group; X 1 is the same as above.)

[0062] In Scheme 3, first, a vinyl group is introduced into fluorofuravin derivative (10) by Stille cross-coupling reaction using organotin compound (30) in the presence of a palladium catalyst in a solvent to synthesize fluorofuravin derivative (31) (Step 1), and then the C═C double bond of the introduced vinyl group is oxidized and epoxidized to obtain fluorofuravin skeleton-containing monomer (32) (Step 2). Next, the obtained monomer (32) is polymerized (Step 3) to synthesize fluorofuravin skeleton-containing polymer (3-3).

[0063] In the first step, the palladium catalyst may be one known to be used in the Stille cross-coupling reaction, and examples thereof include the same palladium catalysts as those exemplified in the reaction between (10) and (11) above. As the organotin compound (30), from the viewpoint of increasing the reaction rate and suppressing side reactions, Rb is preferably an n-butyl group.

[0064] The solvent used in the Stille coupling is not particularly limited as long as it can disperse or dissolve the raw materials used. Examples of such solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, acetonitrile, acetone, alcohols (methanol, ethanol, 1-propanol, 2-propanol, etc.), glycols (ethylene glycol, triethylene glycol, etc.), cellosolves (ethyl cellosolve, methyl cellosolve, etc.), polyhydric alcohols (glycerin, pentaerythritol, etc.), tetrahydrofuran, toluene, ethyl acetate, butyl acetate, benzene, toluene, xylene, pentane, hexane, heptane, chlorobenzene, dichlorobenzene, trichlorobenzene, hexadecane, benzyl alcohol, and oleylamine. These solvents may be selected appropriately depending on the raw materials used. The above solvents may be used alone or in combination of two or more.

[0065] The oxidation of the introduced allyl group in the second step can be carried out by a known method such as a method of oxidizing the allyl group with an oxidizing agent such as peroxide.

[0066] In the third step, the fluofuravin skeleton-containing monomer (32) obtained in the second step is polymerized. The polymerization method and conditions may be appropriately selected from methods and conditions commonly used in cationic ring-opening polymerization of epoxides.

[0067] As the inorganic active material (hereinafter sometimes simply referred to as "active material"), various active materials that have conventionally been used in electrodes for energy storage devices such as secondary batteries can be used, and examples thereof include metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides, and metal nitrides.

[0068] Specific examples of the inorganic active materials include the following: Metal active materials include Al, Sn, and Zn. Metalloid active materials include Si, Ge, and As. Metal alloy active materials include Li-Al alloys, Li-Mg alloys, Li-Al-Ni alloys, Na-Hg alloys, and Na-Zn alloys. Metal oxide active materials include AlO. x , SnO x , SbO x , Bio x , PbO x , ZnO x , CdO x , InO x , TiO x and GaO x (where 0<x≦2), V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2 (wherein M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, and 0.05≦z≦1.10, 0.5≦y≦1.0), ternary active material (Li(Ni a Co b Mn c )O2 (where 0<a<1, 0<b<1, 0<c<1, a+b+c=1)), tin silicon oxide (SnSiO3), lithium bismuth oxide (Li3BiO4), lithium zinc oxide (Li2ZnO2), and lithium titanium oxide (Li4Ti5O 12 Examples of semi-metal oxide active materials include SiO x , GeO x and AsO x (where 0<x≦2) and the like. Examples of metal phosphate active materials include lithium iron phosphate (LiFePO4, LFP). Examples of metal sulfide active materials include FeS2, TiS2, MoS2, Li2S, and lithium iron sulfide (Li x FeS2 (where 0<x≦3) and lithium copper sulfide (Li xCuS (where 0<x≦3) and the like. Examples of metal nitride active materials include Li x M y Examples of the metals include M, M=Co, Ni, Cu, 0≦x≦3, 0≦y≦0.5, and x and y cannot be 0 at the same time, and lithium iron nitride (Li3FeN4).

[0069] In the present invention, among these, FeS2, TiS2, MoS2, LiFePO4, V2O6, and V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2 (wherein M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, and 0.05≦z≦1.10, 0.5≦y≦1.0), Li (Ni a Co b Mn c )O2 (where 0<a<1, 0<b<1, 0<c<1, a+b+c=1), Li4Ti5O 12 , Si, SiO x , AlO x , SnO x , SbO x , Bio x , GeO x , AsO x , PbO x , ZnO x , CdO x , InO x , TiO x and GaO x (where 0<x≦2) is preferred, and LiFePO4 is more preferred.

[0070] Furthermore, Li(Ni a Co b Mn c )O2, it is more preferable that it satisfies the conditions 1 / 3≦a<1, 0<b≦1 / 3, 0<c≦1 / 3, and a+b+c=1. a Co b Mn c)O2 can also be obtained as a commercially available product, and examples of such commercially available products include NCM111 (manufactured by Beijing Easping Material Technology, manufactured by Toshima Manufacturing Co., Ltd., a=1 / 3, b=1 / 3, c=1 / 3), NCM523 (manufactured by Beijing Easping Material Technology, manufactured by JIANGSU Easping Material Technology, a=0.5, b=0.2, c=0.3), NCM622 (manufactured by Beijing Easping Material Technology, a=0.6, b=0.2, c=0.2), NCM811 (manufactured by Beijing Easping Material Technology, Examples include a PTFE-based ...

[0071] The amount of inorganic active material to be added varies depending on the required electrical and thermal properties, the viscosity of the composition, production costs, etc., but is preferably 80 to 99.8 mass % of the solid content, more preferably 85 to 98.5 mass %, and even more preferably 89 to 98 mass %.

[0072] The mass ratio of the inorganic active material to the fluoroflavin skeleton-containing polymer (inorganic active material:fluoroflavin skeleton-containing polymer) is preferably 100:0.01 to 100:1.25, more preferably 100:0.1 to 100:1.05, even more preferably 100:0.1 to 100:0.9, and even more preferably 100:0.1 to 100:0.6. By setting the mass ratio within the above range, the rate characteristics and cycle characteristics of the resulting secondary battery can be effectively improved.

[0073] The electrode material of the present invention preferably further contains a conductive assistant, a binder and a solvent (dispersion medium) as needed.

[0074] Examples of the conductive additive include carbon materials such as graphite, carbon black, acetylene black, vapor-grown carbon fiber, carbon nanotube, carbon nanohorn, and graphene, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. The conductive additives can be used alone or in combination of two or more.

[0075] The amount of the conductive additive is not particularly limited, but is preferably 0.05 to 9 mass %, more preferably 0.1 to 6 mass %, and even more preferably 0.2 to 3 mass % of the solid content. By setting the amount of the conductive additive within the above range, good electrical conductivity can be obtained.

[0076] The binder can be appropriately selected from known materials and is not particularly limited, but examples of binders that can be used in the present invention include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinyl alcohol, polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyaniline, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, etc. These can be used alone or in combination of two or more.

[0077] The amount of the binder is not particularly limited, but is preferably 0.1 to 15 mass % of the solid content, more preferably 0.5 to 12 mass %, and even more preferably 1 to 10 mass %. By setting the amount of the binder within the above range, good adhesion to the current collecting substrate can be obtained without reducing the capacity.

[0078] If necessary, the binder may be dissolved in a suitable solvent, which will be described later, before mixing.

[0079] The solvent is not particularly limited as long as it can disperse or dissolve the raw materials used. Examples of such solvents include water, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), hexamethylphosphoric triamide, acetonitrile, acetone, alcohols (methanol, ethanol, 1-propanol, 2-propanol, etc.), glycols (ethylene glycol, triethylene glycol, etc.), cellosolves (ethyl cellosolve, methyl cellosolve, etc.), polyhydric alcohols (glycerin, pentaerythritol, etc.), tetrahydrofuran, toluene, ethyl acetate, butyl acetate, benzene, toluene, xylene, pentane, hexane, heptane, chlorobenzene, dichlorobenzene, trichlorobenzene, hexadecane, benzyl alcohol, and oleylamine. Among these, water, NMP, dimethyl sulfoxide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, etc. are preferred. These solvents may be appropriately selected depending on the raw materials used, but NMP is preferred when a water-insoluble binder such as PVdF is used. The above solvents may be used alone or in combination of two or more.

[0080] When preparing an electrode material for forming an active material layer, the preparation method is not particularly limited, and the respective components may be mixed in any order. When the solvent used in the synthesis of the fluorofuravin skeleton-containing polymer is the same as the solvents exemplified above or a solvent miscible with them, the resulting reaction solution may be used as is. On the other hand, when the solvent used in the synthesis of the fluorofuravin skeleton-containing polymer is a solvent immiscible with the solvents exemplified above, it is preferable to use a solution isolated by removing the solvent from the resulting reaction solution, or to use a solution substituted with an appropriate solvent.

[0081] The electrode of the present invention has an active material layer (thin film) formed on a substrate, which is a current collector, and the active material layer is made of the electrode material described above. When the active material layer is formed on a substrate, the active material layer can be formed by pressure molding an electrode-forming composition prepared without using a solvent onto the substrate (dry method), or by preparing an electrode-forming composition (electrode slurry) using a solvent, applying it to a current collector, and drying it (wet method). These methods are not particularly limited, and various conventionally known methods can be used. For example, wet methods include various printing methods such as offset printing and screen printing, doctor blade methods, dip coating, spin coating, bar coating, slit coating, and inkjet printing.

[0082] Examples of substrates used for the electrodes include metal substrates such as platinum, gold, iron, stainless steel, copper, aluminum, and lithium; alloy substrates made of any combination of these metals; oxide substrates such as indium tin oxide (ITO), indium zinc oxide (IZO), and antimony tin oxide (ATO); and carbon substrates such as glassy carbon, pyrolytic graphite, and carbon felt.

[0083] The thickness of the active material layer is not particularly limited, but is preferably about 0.01 to 1,000 μm, more preferably about 1 to 200 μm. When the thin film is used alone as an electrode, the thickness is preferably 10 μm or more.

[0084] Furthermore, to further suppress elution of the active material contained in the electrode, the active material layer may further contain a polyalkylene oxide and an ion-conductive salt, or the electrode may be coated with a protective film. The protective film preferably contains a polyalkylene oxide and an ion-conductive salt. The polyalkylene oxide is not particularly limited, but polyethylene oxide, polypropylene oxide, and the like are preferred. The number-average molecular weight of the polyalkylene oxide is preferably 300,000 to 900,000, more preferably 500,000 to 700,000. The number-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

[0085] Examples of the ion-conductive salt include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), etc. The ion-conductive salt is preferably contained in an amount of 5 to 50 parts by mass per 100 parts by mass of the polyalkylene oxide.

[0086] The protective film can be formed, for example, by applying a composition containing a polyalkylene oxide, an ion-conductive salt, and a solvent to the substrate on which the active material layer has been formed by a dipping method or the like, and then drying the applied composition at 40 to 60°C for 30 to 120 minutes. Preferred examples of the solvent include acetonitrile and dichloromethane. The thickness of the protective film is not particularly limited, but is preferably about 10 to 1,000 μm, and more preferably about 50 to 500 μm.

[0087] The secondary battery of the present invention is provided with the above-described electrodes, and more specifically, is provided with at least one pair of positive and negative electrodes, a separator interposed between the electrodes, and an electrolyte, at least one of the positive and negative electrodes being the above-described electrode. Other constituent members of the battery element may be appropriately selected from conventionally known components.

[0088] Examples of materials used for the separator include porous polyolefin, polyamide, and polyester.

[0089] As the electrolyte, an electrolytic solution composed of an electrolyte salt, which is the main body of ion conduction, a solvent, etc. can be suitably used from the viewpoint of easily achieving practically sufficient performance.

[0090] Examples of the electrolyte salt include lithium salts such as LiPF, LiBF, LiN(CFSO), LiAsF, LiSbF, LiAlF, LiGaF, LiInF, LiClO, LiN(CFSO), LiCFSO, LiSiF, and LiN(CFSO)(CFSO), metal iodides such as LiI, NaI, KI, CsI, and CaI, iodide salts of quaternary imidazolium compounds, iodide salts and perchlorates of tetraalkylammonium compounds, and metal bromides such as LiBr, NaBr, KBr, CsBr, and CaBr. These electrolyte salts can be used alone or in combination.

[0091] The solvent is not particularly limited as long as it does not corrode or decompose the materials constituting the battery, thereby deteriorating performance, and dissolves the electrolyte salt. For example, non-aqueous solvents include cyclic esters such as ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone, ethers such as tetrahydrofuran and dimethoxyethane, and chain esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. These solvents can be used alone or in combination.

[0092] The electrode may be pressed as necessary. In this case, the pressing pressure is preferably 1 kN / cm or more. A commonly used pressing method can be used, but mold pressing and roll pressing are particularly preferred. The pressing pressure is not particularly limited, but is preferably 2 kN / cm or more, more preferably 3 kN / cm or more. The upper limit of the pressing pressure is preferably about 40 kN / cm, more preferably about 30 kN / cm.

[0093] A battery manufactured using the above electrode material has superior rate characteristics and cycle characteristics compared to general secondary batteries.

[0094] The type of secondary battery and the type of electrolyte are not particularly limited, and any type of battery such as a lithium ion battery, nickel-metal hydride battery, manganese battery, or air battery may be used, but a lithium ion battery is preferred. The lamination method and production method are also not particularly limited.

[0095] The shape of the cell is not particularly limited, and various conventionally known cell shapes, such as cylindrical, flat-wound prismatic, laminated prismatic, coin, flat-wound laminate, and laminated, can be used. When applied to a coin-shaped cell, the electrode of the present invention described above can be punched into a predetermined disk shape. For example, a lithium-ion secondary battery can be produced by placing one electrode on a coin cell lid to which a washer and spacer are welded, placing a separator of the same shape impregnated with an electrolyte solution on top of that, and then placing the electrode of the present invention on top with the active material layer facing downwards. A case and a gasket are then placed on top, and the resulting battery is sealed using a coin cell crimping machine.

[0096] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The equipment and measurement conditions used are as follows: (1) Rotating / revolving mixer: Awatori Rentaro AR-100, manufactured by Thinky Corporation (2) Ball mill kneading: Mini-Mill Pulverisette 23, manufactured by FRISCH (3) 1H-NMR spectrum: Nuclear magnetic resonance spectrometer ECX-500 (solvent: dimethyl sulfoxide-d6 (DMSO-d6), internal standard: tetramethylsilane) manufactured by JEOL Ltd. (4) IR spectrum: Fourier transform infrared spectrophotometer FT / IR-6100 manufactured by JASCO Corporation (5) Elemental analysis: Perkin Elmer, elemental analyzer PE2400 II (6) Molecular weight measurement: Shimadzu Corporation RID-10A / CBM-20A / DGU-20A3 / LC-20AD / SPD-20A / CTO-20A (column: Shimadzu Corporation TSgel SuperAW-H, column temperature: 50 ° C, solvent: DMF, detector: UV (275 nm) / RI detector (built-in), calibration curve: standard polystyrene) (7) CV measurement, battery characteristic evaluation: ALSCH1760EW manufactured by BAS Co., Ltd. (8) CP-MS spectrum: ECA-400 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd.

[0097] [1] Synthesis of Polymer A [Synthesis Example 1] Synthesis of 2-bromo-5,11-dihydroquinoxalino[2,3-b]quinoxaline (BrFF)

[0098] 2-Bromo-5,11-dihydroquinoxalino[2,3-b]quinoxaline (12) was synthesized as follows, with reference to the method described in Journal of Photochemistry and Photobiology A: Chemistry 198 (2008) 60-68. To a 100 mL flask were added 1.0 g (5.35 mmol) of 4-bromo-1,2-phenylenediamine (11) (Tokyo Chemical Industry Co., Ltd.) and 1.6 g (8.03 mmol) of 2,3-dichloroquinoxaline (12) (Aldrich Co., Ltd.), followed by the addition of 10 mL of ethylene glycol, and the reaction was carried out at 150°C for 2 hours. After completion of the reaction, the mixture was purified by precipitation into methanol, recrystallized with acetic acid, and then vacuum dried to obtain 2-bromo-5,11-dihydroquinoxalino[2,3-b]quinoxaline (12) as brown crystals.

[0099] [Synthesis Example 2] Synthesis of 2-norbornene-5,11-dihydroquinoxalino[2,3-b]quinoxaline (FFNB)

[0100] To a 100 mL flask were placed 200 mg (0.641 mmol) of 2-bromo-5,11-dihydroquinoxalino[2,3-b]quinoxaline (12) obtained in Synthesis Example 1, 11 mg (0.0160 mmol) of bis(triphenylphosphine)palladium(II) dichloride (manufactured by Tokyo Chemical Industry Co., Ltd.), 200 μL (1.92 mmol) of 2,5-norbornadiene (13) (manufactured by Tokyo Chemical Industry Co., Ltd.), 190 μL (1.92 mmol) of triethylamine (manufactured by Kanto Chemical Co., Inc.), 60 μL (1.28 mmol) of formic acid (manufactured by Kanto Chemical Co., Inc.), and 40 mL of N,N-dimethylformamide (DMF), and the mixture was reacted at 80° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, the product was purified by column chromatography using a mixed solvent of ethyl acetate / hexane (=4 / 6 / (V / V)), recrystallized using a mixed solvent of methanol / acetic acid (=3 / 1 (V / V)), and then vacuum dried to obtain 2-norbornene-5,11-dihydroquinoxalino[2,3-b]quinoxaline (14) as yellow crystals.

[0101] Example 1-1 Synthesis of Polymer A (PFNB) 2-norbornene-5,11-dihydroquinoxalino[2,3-b] (500.0 mg, 1.54 mmol) obtained in Synthesis Example 2, Grubbs catalyst third generation (manufactured by Aldrich Corporation) (13.6 mg, 0.0154 mmol), and 31 mL of DMF were added to a 30 mL flask, and the mixture was reacted at 60°C for 3 hours. The reaction solution was added dropwise to 300 mL of methanol, and the precipitated solid was separated by filtration. Insoluble matter was recovered through Soxhlet purification using methanol, and the mixture was dried in vacuo to obtain Polymer A, which is composed of repeating units represented by the following formula (3-1), as a brown solid. The number average molecular weight Mn of Polymer A was 3.0 × 10 4 , weight average molecular weight Mw is 4.2 × 10 4 The polydispersity Mw / Mn was 1.40 (Mn is the number average molecular weight measured under the same conditions as Mw, and the same applies hereinafter). The CP-MS spectrum is shown in FIG.

[0102]

[0103] Comparative Example 1-1 Synthesis of Polyvinylanthraquinone (PVAQ) 100 mg of 2-vinylanthraquinone (Tokyo Chemical Industry Co., Ltd.) and 0.709 mg of AIBN (Tokyo Chemical Industry Co., Ltd.) were added to a 10 mL ampoule, and 2.14 mL of 1,2-dichloroethane was added, followed by a reaction at 60°C for 14 hours. The reaction solution was added dropwise to 100 mL of methanol, and the precipitated solid was filtered off. Insoluble matter was recovered through Soxhlet purification using methanol, and the mixture was vacuum dried to obtain PVAQ as a yellow solid. The number average molecular weight Mn of PVAQ was 3.3 x 10 4 , weight average molecular weight Mw is 7.2 × 10 4 The polydispersity Mw / Mn was 2.2.

[0104] [2] Evaluation of Electrodes and Batteries Containing Polymers [Example 2] CV Measurement of Thin-Film Electrode Using Polymer A 5 mg of polymer A, 40 mg of vapor-grown carbon fiber, and 250 mg of a 2% by mass PVDF NMP solution were added to a ball mill and kneaded for 15 minutes to obtain an electrode slurry. The obtained electrode slurry was applied to aluminum foil and heated and vacuum-dried at 80°C for 16 hours to obtain a thin-film electrode (film thickness approximately 20 μm).

[0105] A polymer lithium secondary battery was fabricated using the resulting electrode as the positive electrode and metallic lithium as the negative electrode, with a 1 mol / L solution of lithium hexafluorophosphate in EC / DEC (= 3 / 7 (v / v)) selected as the electrolyte. The polymer lithium secondary battery was fabricated using the following method. The polymer / carbon composite electrode was cut out to a radius of 10 mm, and the separator was cut out to a radius of 16 mm. A plastic gasket, carbon composite electrode, separator, metallic lithium, spacer, and washer were stacked in this order on the positive terminal case, and a cap was attached and thoroughly crimped using a crimping machine holder to fabricate a polymer lithium secondary battery (coin cell).

[0106] Using this coin cell, CV measurement was carried out at a scan rate of 5 mV / sec. The results are shown in Figure 2. From the results in Figure 2, it can be seen that the thin film electrode prepared using polymer A exhibited a high E 1 / 2 It was confirmed that redox waves appeared at +3.3 V and -3.7 V and remained stable even after repeated sweeps.

[0107] A similarly prepared battery was charged at a constant current of 5.78 μA (0.5 C) until the voltage reached 4.2 V, and then discharged at 5.78 μA (0.5 C). The voltage stabilized at around 3.3 and 3.6 V, then rapidly decreased, resulting in a discharge capacity of 99 mAh / g (60% of the theoretical capacity). The coulombic efficiency was approximately 91%. This confirmed that Polymer A functions as an effective charge storage material. When the voltage rose to 4.2 V, the battery was charged again, and then charged and discharged 50 times in the range of 3.0 to 4.2 V. Figure 3 shows the results of measuring the potential difference with the reference electrode when the charge / discharge capacity was varied, and Figure 4 shows the cycle characteristics during charge / discharge. Even after 100 charge / discharge cycles, the charge / discharge capacity remained at 98% or higher.

[0108] [3] Fluoroflavin skeleton-containing polymer and inorganic active material containing hybrid electrode and lithium ion battery using the electrode [Example 3-1] 0.475 g of lithium iron phosphate (LFP, TATUNG FINE CHEMICALS CO.) as an inorganic active material, 0.0525 g of a 1 mass% N-methylpyrrolidone (NMP) solution of polymer A produced in Example 1-1, 0.352 g of polyvinylidene fluoride (PVdF) NMP solution (12 mass%, Kureha Corporation, KF Polymer L # 1120) as a binder, 0.0106 g of acetylene black as a conductive additive (solid content mass ratio 89.9: 0.1: 8.0: 2.0), further mixed with 0.210 g of NMP so that the total solid content concentration was 48 mass%. This was mixed in a rotation / revolution mixer (2,000 rpm, 10 minutes for three times) to prepare a slurry for forming an electrode. This was uniformly spread on aluminum foil (EQ-CC-Al-18u-260, manufactured by MTI Corporation, substrate thickness 18 μm) using a doctor blade method (wet film thickness 100 μm), and then dried at 80°C for 30 minutes and then at 120°C for 30 minutes to form an active material layer. This was pressure-bonded using a roll press to produce electrode C1 (film thickness 30 μm).

[0109] [Comparative Example 3-1] 0.475 g of lithium iron phosphate (LFP, TATUNG FINE CHEMICALS CO.) was used as an inorganic active material, 0.352 g of an NMP solution of polyvinylidene fluoride (PVdF) (12% by mass, KF Polymer L#1120, manufactured by Kureha Corporation) was used as a binder, and 0.0106 g of acetylene black (solid content mass ratio 90:8.0:2.0) was used as a conductive additive. 0.255 g of NMP was further mixed to give a total solid content of 48% by mass. This was mixed in a rotation / revolution mixer (2,000 rpm, 10 minutes 3 times) to prepare an electrode-forming slurry. This was spread uniformly on aluminum foil (EQ-CC-Al-18u-260, manufactured by MTI Corporation, substrate thickness 18 μm) by the doctor blade method (wet film thickness 100 μm), and then dried at 80° C. for 30 minutes and then at 120° C. for 30 minutes to form an active material layer. This was pressed using a roll press to produce electrode C2 (film thickness 30 μm).

[0110] [Comparative Example 3-2] 0.475 g of lithium iron phosphate (LFP, TATUNG FINE CHEMICALS CO.) as an inorganic active material, 0.0525 g of a 1 mass% N-methylpyrrolidone (NMP) solution of the polymer PVAQ produced in Comparative Example 1-1, 0.352 g of an NMP solution of polyvinylidene fluoride (PVdF) as a binder (12 mass%, Kureha Corporation, KF Polymer L # 1120), 0.0106 g of acetylene black as a conductive additive (solid content mass ratio 89.9: 0.1: 8.0: 2.0), and 0.210 g of NMP was mixed so that the total solid content concentration was 48 mass%. This was mixed in a rotation / revolution mixer (2,000 rpm, 10 minutes 3 times) to prepare a slurry for forming an electrode. This was spread uniformly on aluminum foil (EQ-CC-Al-18u-260, manufactured by MTI Corporation, substrate thickness 18 μm) by the doctor blade method (wet film thickness 100 μm), and then dried at 80° C. for 30 minutes and then at 120° C. for 30 minutes to form an active material layer. This was pressed using a roll press to produce electrode C3 (film thickness 30 μm).

[0111] [Comparative Example 3-3] 0.475 g of lithium iron phosphate (LFP, TATUNG FINE CHEMICALS CO.) as an inorganic active material, 0.0525 g of a 1 mass% N-methylpyrrolidone (NMP) solution of PMMA, 0.352 g of a 12 mass% NMP solution of polyvinylidene fluoride (PVdF) as a binder (12 mass%, Kureha Corporation, KF Polymer L # 1120), 0.0106 g of acetylene black as a conductive additive (solid content mass ratio 89.9: 0.1: 8.0: 2.0), and 0.210 g of NMP was further mixed so that the total solid content concentration was 48 mass%. This was mixed in a rotation / revolution mixer (2,000 rpm, 10 minutes 3 times) to prepare a slurry for forming an electrode. This was spread uniformly on aluminum foil (EQ-CC-Al-18u-260, manufactured by MTI Corporation, substrate thickness 18 μm) by the doctor blade method (wet film thickness 100 μm), and then dried at 80° C. for 30 minutes and then at 120° C. for 30 minutes to form an active material layer. This was pressed using a roll press to produce electrode C4 (film thickness 30 μm).

[0112] [Comparative Example 3-4] 0.475 g of lithium iron phosphate (LFP, TATUNG FINE CHEMICALS CO.) as an inorganic active material, 0.0525 g of a 1 mass% N-methylpyrrolidone (NMP) solution of PAN, 0.352 g of a 12 mass% NMP solution of polyvinylidene fluoride (PVdF) as a binder (12 mass%, Kureha Corporation, KF Polymer L # 1120), 0.0106 g of acetylene black as a conductive additive (solid content mass ratio 89.9: 0.1: 8.0: 2.0), and 0.210 g of NMP was further mixed so that the total solid content concentration was 48 mass%. This was mixed in a rotation / revolution mixer (2,000 rpm, 10 minutes 3 times) to prepare an electrode-forming slurry. This was spread uniformly on aluminum foil (EQ-CC-Al-18u-260, manufactured by MTI Corporation, substrate thickness 18 μm) by the doctor blade method (wet film thickness 100 μm), and then dried at 80° C. for 30 minutes and then at 120° C. for 30 minutes to form an active material layer. This was pressed using a roll press to produce electrode C5 (film thickness 30 μm).

[0113] Example 4-1: The electrode C1 obtained in Example 3-1 was punched out into a 10 mm diameter disk. After measuring its mass, it was vacuum-dried at 100°C for 15 hours and transferred to an argon-filled glove box. A lithium foil (Honjo Chemical Co., Ltd., 1.0 mm thick) punched out to a diameter of 15 mm was placed on the lid of a 2032-type coin cell (Hosen Co., Ltd.) with a washer and spacer welded to the lid. A separator (Celgard Co., Ltd., 2400) punched out to a diameter of 16 mm and impregnated with an electrolyte (Kishida Chemical Co., Ltd., ethylene carbonate:diethyl carbonate = 3:7 (volume ratio), containing 1 mol / L of lithium hexafluorophosphate as an electrolyte) for at least 24 hours was placed on top of the foil. An electrode was then placed on top of the foil, with the side with the active material layer facing down. After one drop of electrolyte was dropped onto the battery, the case and gasket were placed on the battery, and the battery was sealed with a coin cell crimping machine. The battery was then left to stand for 24 hours to prepare a secondary battery for testing.

[0114] Comparative Examples 4-1 to 4-4 Test secondary batteries were fabricated in the same manner as in Example 4-1, except that electrodes C2 to C5 fabricated in Comparative Examples 3-1 to 3-4, respectively, were used instead of electrode C1.

[0115] The physical properties of the electrodes of the lithium ion secondary batteries produced in Example 4-1 and Comparative Examples 4-1 to 4-4 were evaluated under the following conditions using a charge / discharge measuring device. The discharge voltage and discharge capacity at a discharge rate of 10 C for each secondary battery are shown in Table 1. [Measurement conditions] Rate characteristics: Current: 0.5 C constant current charge, 10 C constant current discharge (LFP capacity was set to 152 mAh / g) Cut-off voltage: 4.20 V - 2.00 V Temperature: Room temperature

[0116] The physical properties of the electrodes of the lithium ion secondary batteries produced in Example 4-1 and Comparative Examples 4-1 to 4-5 were evaluated under the following conditions using a charge / discharge measuring device. The charge voltage and discharge capacity at a charge rate of 10 C for each secondary battery are shown in Table 2. [Measurement conditions] Rate characteristics: Current: 10 C constant current charge, 0.5 C constant current discharge (LFP capacity was set to 152 mAh / g) Cut-off voltage: 4.20 V - 2.00 V Temperature: Room temperature

[0117]

[0118]

[0119] From the results in Tables 1 and 2, it was confirmed that a battery having excellent rate characteristics can be obtained by using an electrode material containing the fluorofuravin skeleton-containing polymer defined in the present invention.

Claims

1. An electrode material comprising a polymer having a flavin skeleton in a side chain and an inorganic active material, wherein the polymer is 1% by mass or less in solid content.

2. The electrode material according to claim 1, wherein the polymer is a polymer containing a repeating unit represented by the following formula (1). (In the formula, R M represents a hydrogen atom or a methyl group.), represents a partial structure represented by, Y represents a single bond, -O-, -CO-, -COO-, -OCO-, -CH2-, -NH-, -NCH3-, -NHCO-, -CONH-, -CH2NHCO-, -CONHCH2-, or -S-, R 1 each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carboxy group, an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms which may be substituted with a halogen atom, and * represents a bond. ] 3. The electrode material according to claim 2, wherein the Z is a partial structure represented by the formula (Z-1).

4. The electrode material according to any one of claims 1 to 3, wherein all of the R 1 are hydrogen atoms.

5. The electrode material according to any one of claims 1 to 4, wherein the Y is a single bond.

6. The electrode material according to claim 5, wherein the inorganic active material is at least one selected from metals, semimetals, metal alloys, metal oxides, semimetal oxides, metal phosphates, metal sulfides and metal nitrides.

7. The electrode material according to any one of claims 1 to 6, further containing a solvent.

8. The electrode material according to any one of claims 1 to 7, further containing a conductive assistant and a binder.

9. An electrode having an active material layer made of the electrode material according to any one of claims 1 to 8.

10. A secondary battery including the electrode according to claim 9.

11. A polymer containing a repeating unit represented by the following formula (1). (In the formula, R Mrepresents a hydrogen atom or a methyl group. ) represents a partial structure represented by, and Y represents a single bond, -O-, -CO-, -COO-, -OCO-, -CH2-, -NH-, -NCH3-, -NHCO-, -CONH-, -CH2NHCO-, -CONHCH2-, or -S- (provided that when Z is a partial structure represented by formula (Z-1), it does not become -CH2NHCO-, and when Z is a partial structure represented by formula (Z-2), it does not become a single bond. ), R 1 each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms which may be substituted with a halogen atom, and * represents a bond. ] 12. The polymer according to claim 11, wherein the above Z is a partial structure represented by formula (Z-1).

13. The above R 1 The polymer according to claim 11 or 12, wherein all are hydrogen atoms.

14. The polymer according to any one of claims 11 to 13, wherein the above Y is a single bond.

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