Positive electrode composition for secondary battery, positive electrode for the secondary battery, and the secondary battery

Abstract

To provide a positive electrode composition for a secondary battery capable of producing an electrode having excellent electrolyte permeability and excellent electrode strength, and further having a high adhesion strength to a current collector in the case of a slurry electrode.SOLUTION: A positive electrode composition for a secondary battery contains a positive electrode active material, a binder resin, and an additive agent. In the positive electrode composition for the secondary battery, the additive agent is a compound (P) satisfying all of the following (i) to (iii): (i) it has a solubility parameter of 9.0 to 12.0 (cal / cm3)1 / 2; (ii) the compound (P) is a compound represented by the following general formula (1) of A-(EO)m-B... (1); and (iii) one of an atomic group A and an atomic group B has one group selected from a group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other one has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a positive electrode composition for a secondary battery, a positive electrode for a secondary battery, and a secondary battery. [Background technology]

[0002] Secondary batteries such as lithium-ion batteries are widely used in the field of portable information devices, including mobile phones and laptop computers. While the applications of secondary batteries continue to expand, their use in hybrid and electric vehicles, in addition to traditional applications, is also being considered, and some applications have already been put into practical use. To further popularize these applications, there is a demand for higher capacity and power output secondary batteries, and various technologies are being attempted.

[0003] One way to improve the capacity of secondary batteries is to increase electrode density. By densely packing the active material, more capacity can be obtained. However, increasing the electrode density makes it difficult for the electrolyte to penetrate the electrode, resulting in problems such as less capacity than the theoretical value and a deterioration in output characteristics.

[0004] To solve these problems, Patent Document 1 discloses a technique for improving electrolyte permeability by providing grooves on the electrode surface. Patent Document 2 discloses a technique for improving electrolyte permeability by adjusting the particle size and shape of the active material. Patent Document 3 discloses a technique for improving electrolyte permeability by adjusting the electrode density. Patent Document 4 also describes that electrolyte impregnation can be improved by incorporating a specific nonionic surfactant such as polyethylene glycol monooleate into the electrode active material layer of the electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-27633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-151088 [Patent Document 3] Japanese Patent Publication No. 2020-053282 [Patent Document 4] Patent No. 5742561 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method of Patent Document 1 involves a step of pressing the electrode surface with a roller having irregularities to form grooves on the surface, which necessitates the introduction of new equipment, which is a problem. Although the methods disclosed in Patent Documents 2 and 3 have shown some improvement in permeability in negative electrodes, the effect is not sufficient, and no study has been conducted on positive electrodes. Furthermore, the effects of these methods on required performance, such as the adhesive strength between the current collector and the electrode, have not been considered. Furthermore, Patent Document 4 discloses that the initial charge / discharge efficiency is improved in a battery equipped with an electrode containing a nonionic surfactant such as polyethylene glycol monooleate in the electrode active material layer, but the impregnation or permeability of the electrolyte was not actually evaluated, and the effect was unknown. Furthermore, the present inventors have found that although the initial charge-discharge efficiency of a battery equipped with an electrode containing the above-mentioned nonionic surfactant in the electrode active material layer is improved, the adhesive strength between the current collector and the electrode may be reduced.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a positive electrode composition for a secondary battery that can be used to produce an electrode that has excellent electrolyte permeability, excellent electrode strength, and, in the case of a slurry electrode, also has high adhesive strength to a current collector. [Means for solving the problem]

[0008] The present inventors have made extensive studies and arrived at the present invention. The present invention relates to any of the following: A positive electrode composition for a secondary battery comprising a positive electrode active material, a binder resin, and an additive, wherein the additive is a compound (P) that satisfies all of the following (i) to (iii): (i) The solubility parameter of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 is; (ii) The compound (P) is a compound represented by the following general formula (1): A-(EO) m -B (1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group, and (EO) m is a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group. A positive electrode for a secondary battery is obtained by compression molding the positive electrode composition for a secondary battery. A secondary battery comprising the above positive electrode for secondary batteries. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a positive electrode composition for a secondary battery that can produce an electrode that has excellent electrolyte permeability, excellent electrode strength, and, in the case of a slurry electrode, also has high adhesive strength with the current collector. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The present invention relates to a secondary battery positive electrode composition, a positive electrode for a secondary battery, and a lithium ion battery. The electrode composition for a secondary battery of the present invention may be an electrode composition for a lithium ion battery or an electrode composition for a sodium ion battery. In this specification, when lithium ion batteries and sodium ion batteries are mentioned, these concepts also include lithium ion secondary batteries and sodium ion secondary batteries, respectively. Hereinafter, the "secondary battery electrode composition" will also be referred to as the "electrode composition."

[0011] <Cathode composition for secondary batteries> The positive electrode composition for a secondary battery of the present invention is a positive electrode composition for a secondary battery containing a positive electrode active material, a binder resin, and an additive, wherein the additive is a compound (P) that satisfies all of the following (i) to (iii): (i) The solubility parameter of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 is; (ii) The compound (P) is a compound represented by the following general formula (1): A-(EO) m -B (1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group, and (EO) m is a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group.

[0012] The positive electrode composition of the present invention is an electrode composition for a positive electrode of a secondary battery. The positive electrode composition of the present invention itself does not contain an electrolyte solution, but as will be described later, a positive electrode layer for a secondary battery can be formed by adding an electrolyte solution to a positive electrode prepared using the positive electrode composition.

[0013] (Cathode active material) The positive electrode active material constituting the positive electrode composition for lithium ion batteries includes composite oxides of lithium and transition metals {composite oxides containing one type of transition metal (e.g., LiCoO2, LiNiO2, LiAlMnO4, LiMnO2, and LiMn2O4), composite oxides containing two types of transition metal elements (e.g., LiFeMnO4, LiNi 1-x Co x O2, LiMn 1-y Co y O2, LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2) and composite oxides containing three or more transition metal elements [e.g., LiM a M' b M'' c O2 (M, M' and M'' are different transition metal elements, and a + b + c = 1. For example, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), etc.}, lithium-containing transition metal phosphates (for example, LiFePO4, LiCoPO4, LiMnPO4, and LiNiPO4), transition metal oxides (for example, MnO2 and V2O5), transition metal sulfides (for example, MoS2 and TiS2), and conductive polymers (for example, polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole), and two or more of them may be used in combination. The lithium-containing transition metal phosphate may have some of the transition metal sites substituted with other transition metals. The positive electrode active material constituting the positive electrode composition for lithium ion batteries is preferably a composite oxide of lithium and a transition metal.

[0014] The cathode active material constituting the electrode composition for a sodium ion battery is not particularly limited as long as it can be used in a sodium ion battery. Specifically, examples thereof include layered active materials, spinel-type active materials, oxoacid salt active materials, etc. For example, NaFeO2, NaNiO2, NaCoO2, NaCrO2, NaMnO2, NaVO2, Na(Ni X Mn 1-X )O2(0 < X < 1), Na(Fe X Mn 1-X )O2(0 < X < 1), NaVPO4F, Na2FePO4F, Na3V2(PO4)3, etc. can be mentioned. Preferably, they are NaCoO2 and NaCrO2.

[0015] The volume average particle diameter (D50) of the above-mentioned cathode active material is preferably 3.5 to 25 μm, and more preferably 3.5 to 13 μm. In this specification, the value of "the volume average particle diameter (D50) of the cathode active material" means the value of the 50% diameter in the volume-based integrated fraction obtained by the laser diffraction measurement method.

[0016] The content of the cathode active material in the cathode composition is not particularly limited, but from the viewpoint of increasing the electrode density and the battery capacity, it is preferable that the content of the cathode active material is high. Based on the solid content weight of the cathode composition, it is preferably 89 to 98% by weight, and more preferably 94 to 98% by weight. Note that the "solid content weight of the cathode composition" means the weight of the material excluding volatile components such as organic solvents (the total value of the weights of the cathode active material, binder resin, conductive aid, and additive, etc.). Specifically, the weight of the residue when the cathode composition is heated at 100 °C for 8 hours is taken as the solid content weight.

[0017] (Binder resin) The binder resin is a resin used in lithium ion batteries or sodium ion batteries, and examples thereof include starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyethylene, and polypropylene, and two or more types may be used in combination. When the positive electrode composition contains these substances, it is considered to contain a binder resin. In this specification, the binder resin is a substance that is distinguished from the additive (compound (P)).

[0018] The content of the binder resin is preferably 1 to 10% by weight based on the weight of the solid content of the positive electrode composition.

[0019] (additives) The additive in the present invention is a compound (P) that satisfies all of the following (i) to (iii): (i) The solubility parameter of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 is; (ii) The compound (P) is a compound represented by the following general formula (1): A-(EO) m -B (1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group, and (EO) m is a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group.

[0020] In this specification, the solubility parameter (hereinafter sometimes referred to as the SP value) refers to a value calculated by the formula (28) on page 153 of the method by Fedors [Polymer Engineering and Science, February 1974, Vol. 14, No. 2, pp. 147-154] using the values ​​(heat of vaporization and molar volume at 25°C of atoms or functional groups) listed on page 152 (Table 5).

[0021] The SP value of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 The SP value of compound (P) is 9.0 (cal / cm 3 ) 1 / 2 Less than or equal to 12.0 (cal / cm 3 ) 1 / 2 If the SP value of the compound (P) is more than 9.2 to 11.6 (cal / cm), the electrolyte permeability of the positive electrode obtained from the positive electrode composition and the electrode strength (particularly, the adhesive strength between the positive electrode and the current collector in the case of a slurry electrode) tend to decrease. 3 ) 1 / 2 It is preferable that the viscosity is 9.8 to 11.6 (cal / cm 3 ) 1 / 2 It is more preferable that:

[0022] The SP value of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 The method for adjusting this can be, for example, by adjusting the number of repeating oxyethylene chains depending on the types of atomic group A and atomic group B of compound (P) described below.

[0023] The compound (P) is a compound represented by the following general formula (1). A-(EO) m -B (1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group, and (EO) mis a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.]

[0024] In general formula (1), m is a number of 5 to 30 representing the average repeating number of ethyleneoxy groups. If m is less than 5, the electrode strength (particularly bending resistance) of the positive electrode obtained from the positive electrode composition decreases. If m exceeds 30, the electrode strength of the positive electrode (adhesion strength between the positive electrode and the current collector in the case of a slurry electrode, and bending resistance) decreases, and further, the electrolyte permeability of the positive electrode may also decrease. m is preferably a number of 5 to 22, and more preferably a number of 7 to 22.

[0025] In general formula (1), A and B each represent an atomic group bonded to a polyoxyethylene chain. The ratio of the total weight proportion of the atomic group A and atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of atomic group A and atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51. For example, in the case of a compound in which m is 5, the formula weight of the polyoxyethylene chain is 44×5=220, so the sum of the formula weights of atomic group A and atomic group B of the compound is 2.2 to 211.4. When calculating the formula weight of the polyoxyethylene chain, atomic group A, and atomic group B, the atomic weight of each atom is calculated using the following values, with significant figures to one decimal place. Hydrogen (H): 1.0 Carbon (C): 12.0 Nitrogen (N): 14.0 Oxygen (O): 16.0 Sulfur (S): 32.1 Phosphorus (P): 31.0 Silicon (Si): 28.1

[0026] Furthermore, the weight ratio of the atomic group A based on the weight of the polyoxyethylene chain is 50% by weight or less, and the weight ratio of the atomic group B based on the weight of the polyoxyethylene chain is 50% by weight or less. The weight ratio of the atomic group A based on the weight of the polyoxyethylene chain is preferably 25% by weight or less. The weight ratio of the atomic group B based on the weight of the polyoxyethylene chain is preferably 25% by weight or less.

[0027] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group. As long as the above "ratio of the total weight proportion of atomic group A and atomic group B to the weight proportion of the polyoxyethylene chain" is satisfied, atomic group A and atomic group B may have a structure other than the one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, or the one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group. The atomic group A and the atomic group B may have a linear or branched structure, but from the viewpoint of electrolyte permeability and the like, a linear structure is preferred. Furthermore, the position in compound (P) at which the one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, or the one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group, is located is not particularly limited. However, it is preferred that atomic group A and / or atomic group B have a linear structure and that the one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and / or the one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group, is located at the molecular terminal of compound (P) (i.e., also at the terminal of atomic group A and / or atomic group B), as this makes the effects of the present invention particularly remarkable.

[0028] Whether or not compound (P) has a hydroxyl group in atomic group A or atomic group B can be confirmed by NMR analysis and measuring the hydroxyl value of compound (P). Whether or not compound (P) has an amino group in atomic group A or atomic group B can be confirmed by NMR analysis and measuring the amine value of compound (P). Whether or not compound (P) has a carboxyl group in atomic group A or atomic group B can be confirmed by NMR analysis and measuring the acid value of compound (P). The hydroxyl value can be measured by the method specified in JIS K0070, the amine value can be measured by the method specified in ASTM D2074, and the acid value can be measured by the method specified in JIS K0070.

[0029] The compound (P) is not particularly limited as long as it satisfies all of the above (i) to (iii), and specific examples include a compound (P2) represented by the following general formula (2), a compound (P3) represented by the following general formula (3), a compound (P4) represented by the following general formula (4), a compound (P5) represented by the following general formula (5), a compound (P6) represented by the following general formula (6), a compound (P7) represented by the following general formula (7), a compound (P8) represented by the following general formula (8), a compound (P9) represented by the following general formula (9), a compound (P10) represented by the following general formula (10), and a compound (P11) represented by the following general formula (11). R 1 O-(EO) m -H (2) H2N-R 2 O-(EO) m -R 3 (3) R 4 O-(EO) m -R 5 -COOH (4) H2N-(EO) m -CH2CH2-NH2(5) HOOC-R 6 O-(EO) m -R 7 -COOH (6) R 8 O-(EO) m -C(=O)-R9 -COOH (7) HOOC-R 10 -C(=O)O-(EO) m -C(=O)-R 11 -COOH (8) R 12 O-(EO) m -R 13 -C(=O)NH-R 14 -NH2(9) H2N-R 15 -HNC(=O)-R 16 -C(=O)O-(EO) m -C(=O)-R 17 -C(=O)NH-R 18 -NH2(10) H2N-R 19 -C(=O)O-(EO) m -C(=O)-R 20 -NH2(11) [In the formula, R 1 , R 3 , R 4 , R 8 and R 12 R are each independently an alkyl group having 1 to 2 carbon atoms or a hydrogen atom. 9 , R 10 , R 11 , R 14 , R 15 , R 18 , R 19 and R 20 are each independently a divalent hydrocarbon group having 1 to 24 carbon atoms. 2 , R 5 , R 6 , R 7 , R 13 , R 16 and R 17 are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms; EO is an ethyleneoxy group, and m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group; (EO) m is a polyoxyethylene chain, and (EO) in general formula (1) m is the same as

[0030] R in the above general formulas (2) to (11) 1 , R3 , R 4 , R 8 and R 12 are each independently an alkyl group having 1 to 2 carbon atoms (methyl group, ethyl group) or a hydrogen atom. From the viewpoint of battery performance (coulomb efficiency, battery capacity, etc.), a methyl group or a hydrogen atom is preferred.

[0031] R in the above general formulas (2) to (11) 9 , R 10 , R 11 , R 14 , R 15 , R 18 , R 19 and R 20 are each independently a divalent hydrocarbon group having 1 to 24 carbon atoms. Examples of the divalent hydrocarbon group having 1 to 24 carbon atoms include an alkylene group having 1 to 24 carbon atoms, an arylene group having 6 to 24 carbon atoms, and an aralkylene group having 7 to 24 carbon atoms.

[0032] Examples of the alkylene group having 1 to 24 carbon atoms include linear alkylene groups having 1 to 24 carbon atoms (e.g., methylene, ethylene, propylene, butylene, pentylene, hexylene, octylene, decylene, dodecylene, and octadecylene), branched alkylene groups having 1 to 24 carbon atoms (e.g., 1,1-dimethylethylene, ethylethylene, propylidene, methylethylene, 3,3-dimethylpentylene, and 4-isopropyl-5-propyloctylene), and cyclic alkylene groups having 1 to 24 carbon atoms (e.g., cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, and cyclooctylene).

[0033] Examples of the arylene group having 6 to 24 carbon atoms include a phenylene group, a methylphenylene group, a dimethylphenylene group, a biphenylene group, a naphthylene group, and a methylnaphthylene group, which may have a substituent (for example, an alkyl group having 1 to 5 carbon atoms).

[0034] Examples of the aralkylene group having 7 to 24 carbon atoms include a p-phenylenemethylene group, an m-phenylenemethylene group, a p-phenyleneethylene group, an m-phenyleneethylene group, a p-phenylene-methylmethylene group, a 3,5-dimethyl-1-methylene-1,4-phenylene group, a p-phenylenedimethylmethylene group, a p-phenylene-hexylene group, a p-biphenylenemethylene group, a naphthalene-4-methylene-1,4-diyl group, a naphthalene-6-methylene-2,6-diyl group, and a naphthalene-5-butylene-1,5-diyl group.

[0035] R in the above general formulas (2) to (11) 2 , R 5 , R 6 , R 7 , R 13 , R 16 and R 17 are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms include those having 10 or less carbon atoms among the above-mentioned "divalent hydrocarbon groups having 1 to 24 carbon atoms."

[0036] Specific examples of the compound (P2) represented by the general formula (2) include polyoxyethylene alkyl ethers (R 1 is an alkyl group having 1 to 2 carbon atoms) and polyethylene glycol (R 1 is a hydrogen atom). Polyoxyethylene alkyl ether can be produced, for example, by adding ethylene oxide to an alkyl alcohol (having 1 to 2 carbon atoms). The alkyl alcohol (having 1 to 2 carbon atoms) is methanol or ethanol. In this specification, "carbon number" may be expressed as "C number" or "C". "Ethylene oxide" may be expressed as "EO".

[0037] Specific examples of the compound (P3) represented by the above general formula (3) include polyoxyethylene alkyl ether amines. Polyoxyethylene alkyl ether amines can be produced, for example, by alkylating an ethylene oxide adduct of alkanolamine (ethylene oxide added to the hydroxyl group of alkanolamine) with alkyl chloride (C1-2). Examples of alkanolamines include aliphatic alkanolamines (methanolamine, ethanolamine, 3-amino-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol, 6-amino-1-hexanol, 7-amino-1-heptanol, 8-amino-1-octanol, 2-amino-1-propanol, 3-amino-1-butanol, 4-amino-1-pentanol, and heptaminol), and aromatic alkanolamines (4-aminophenol, 4-aminobenzyl alcohol, 2-(4-aminophenyl)ethanol, 4-(aminomethyl)phenol, and tyramine). The alkyl chloride (C1-2) is methyl chloride (methyl chloride) or ethyl chloride (ethyl chloride).

[0038] Specific examples of the compound (P4) represented by the above general formula (4) include polyoxyethylene alkyl ether carboxylic acids. Polyoxyethylene alkyl ether carboxylic acids can be produced, for example, by carboxymethylating an ethylene oxide adduct of an alkyl alcohol (C1-2) with a chlorocarboxylic acid. The alkyl alcohol (C1-2) is methanol or ethanol. Examples of chlorocarboxylic acids include monochloroacetic acid, 3-chloropropionic acid, 4-chlorobutyric acid, 5-chlorovaleric acid, 6-chlorocaproic acid, 7-chloroenanthic acid, 8-chlorocaprylic acid, and alkali metal salts thereof.

[0039] A specific example of the compound (P5) represented by the general formula (5) above is polyoxyethylene bisamine. Polyoxyethylene bisamine can be produced, for example, by reacting polyethylene glycol with ammonia in a hydrogen atmosphere.

[0040] A specific example of the compound (P6) represented by the general formula (6) above is polyoxyethylene dicarboxylic acid. Polyoxyethylene dicarboxylic acid can be produced, for example, by reacting polyethylene glycol with carbon monoxide or carbon dioxide in the presence of a metal catalyst, or by reacting polyethylene glycol with two equivalents of a chlorocarboxylic acid. Examples of chlorocarboxylic acids include monochloroacetic acid, 3-chloropropionic acid, 4-chlorobutyric acid, 5-chlorovaleric acid, 6-chlorocaproic acid, 7-chloroenanthic acid, 8-chlorocaprylic acid, and alkali metal salts thereof.

[0041] Specific examples of the compound (P7) represented by the above general formula (7) include polyoxyethylene alkyl ether carboxylic acid esters. Polyoxyethylene alkyl ether carboxylic acid esters can be produced, for example, by esterifying the OH terminal of an ethylene oxide adduct of an alkyl alcohol (C1-2) with a dicarboxylic acid. The alkyl alcohol (C1-2) is methanol or ethanol. Examples of dicarboxylic acids include aliphatic dicarboxylic acids (succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, maleic acid, fumaric acid, and itaconic acid), aromatic dicarboxylic acids (phthalic acid, 2,6- or 2,7-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, tolylenedicarboxylic acid, xylylenedicarboxylic acid, and 5-sulfoisophthalic acid), and alicyclic dicarboxylic acids (cyclopropanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cyclohexenedicarboxylic acid, bicyclohexyl-4,4'-dicarboxylic acid, and camphoric acid).

[0042] Specific examples of the compound (P8) represented by the above general formula (8) include polyoxyethylene dicarboxylic acid esters. Polyoxyethylene dicarboxylic acid esters can be produced, for example, by esterifying both ends of polyethylene glycol with dicarboxylic acids. As the dicarboxylic acid, the same ones as those exemplified as the raw material for (P7) above can be used.

[0043] Specific examples of the compound (P9) represented by the above general formula (9) include polyoxyethylene alkyl ether ester amides. The polyoxyethylene alkyl ether ester amide can be produced, for example, by amidating the above-mentioned polyoxyethylene alkyl ether carboxylic acid with a diamine. Examples of diamines include aliphatic diamines (ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, and decamethylenediamine), and aromatic diamines (1,4-phenylenediamine, 4-aminobenzylamine, and 4,4′-diaminodiphenyl ether).

[0044] Specific examples of the compound (P10) represented by the general formula (10) include polyoxyethylene dialkylamine ester amides. Polyoxyethylene dialkylamine ester amide can be produced, for example, by amidating the above-mentioned polyoxyethylene dicarboxylic acid ester with a diamine. As the diamine, the same ones as those exemplified as the raw materials for (P9) above can be used.

[0045] Specific examples of the compound (P11) represented by the above general formula (11) include polyoxyethylene dialkylamine esters. Polyoxyethylene dialkylamine esters can be produced, for example, by esterifying polyethylene glycol with an amino acid. Examples of amino acids include aliphatic amino acids (aminoacetic acid, 3-aminopropionic acid, 4-aminobutyric acid, 5-aminovaleric acid, 6-aminocaproic acid, 7-aminoenanthic acid, and 8-chlorocaprylic acid), and aromatic amino acids (4-aminobenzoic acid, 4-(aminomethyl)benzoic acid, 4-aminophenylacetic acid, 3-(4-aminophenyl)propionic acid, and 4-(4-aminophenyl)butyric acid).

[0046] Among the above (P2) to (P11), from the viewpoint of electrolyte permeability of the positive electrode, (P2), (P5) and (P6) are particularly preferred, (P2) is more preferred, and (P2) where m is 5 to 9 is most preferred. Among the above (P2) to (P11), from the viewpoint of the adhesive strength between the positive electrode and the current collector, (P3), (P4), (P5), (P6), (P7), (P8), (P9), (P10) and (P11) are particularly preferred, and (P3), (P5) and (P6) are even more preferred.

[0047] The content of the compound (P) is preferably 0.05 to 1.5 wt % and more preferably 0.1 to 1.5 wt % based on the weight of the positive electrode active material. When the content of the compound (P) is within this range, the ratio of the compound (P) to the positive electrode active material becomes appropriate, and the effect of including the compound (P) can be suitably exhibited.

[0048] The additive may contain one or more of the above compounds (P).

[0049] The positive electrode composition for a secondary battery of the present invention may contain a conductive aid in addition to the above-mentioned positive electrode active material, binder resin, and additives.

[0050] (Conductive additive) Examples of conductive additives include metals [aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.], carbon [graphite (flaky graphite (UP)), carbon black (acetylene black (AB), ketjen black, furnace black, channel black, thermal lamp black, etc.), carbon nanofibers (CNF), carbon nanotubes (CNT), etc.], and mixtures thereof, and two or more of them may be used in combination. As the conductive aid, carbon black and carbon nanotubes are preferred.

[0051] The content of the conductive additive is preferably 0 to 6% by weight, and more preferably 1 to 6% by weight, based on the weight of the solid content of the positive electrode composition.

[0052] <Method of manufacturing a positive electrode composition for secondary batteries> The positive electrode composition for a secondary battery of the present invention can be obtained by mixing the additive with other components (positive electrode active material, binder resin, and other components (conductive assistant, etc.) as needed). There are no particular limitations on the method for mixing the components, and the additives, the positive electrode active material, the binder resin, and, if necessary, other components may be dissolved or dispersed in a solvent to form a wet positive electrode composition (also referred to as a slurry positive electrode composition). Alternatively, a dry cathode composition may be prepared by mixing the additive, the cathode active material, and other components as necessary with a binder resin without using a solvent. When preparing a dry cathode composition, a binder resin that fibrillates under shear force, such as polytetrafluoroethylene, can be suitably used.

[0053] The compound (P) contained in the positive electrode composition for a secondary battery of the present invention has a polyoxyethylene chain and at least one of the atomic group A and atomic group B has one selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group that has affinity for the positive electrode active material. Therefore, it can be adsorbed to the surface of the positive electrode active material by a part of the polyoxyethylene chain and / or a functional group in the atomic group A or atomic group B. Furthermore, compound (P) has a polyoxyethylene chain and does not have a long-chain alkyl group in atomic group A or atomic group B, which has low affinity for the solvent of the electrolyte solution. Therefore, the contact between the solvent of the electrolyte solution and the polyoxyethylene chain is not inhibited, and the compound (P) has good affinity for the solvent of the electrolyte solution. As described above, it is believed that the compound (P) has affinity for both the positive electrode active material and the solvent of the electrolyte, and therefore can improve the permeability of the electrolyte into the positive electrode. Furthermore, compound (P) has one selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, which have affinity for the current collector (metal foil), in at least one of the atomic group A and atomic group B, and does not have a long-chain alkyl group, which has low affinity for the current collector (metal foil), in atomic group A or atomic group B. Therefore, even if compound (P) is added to a positive electrode composition for a secondary battery, the adhesion between the resulting positive electrode and the current collector (metal foil) is not significantly impaired.

[0054] <Positive electrodes for secondary batteries> The positive electrode for a secondary battery of the present invention is produced by compression molding the positive electrode composition for a secondary battery of the present invention. The positive electrode for the secondary battery may be a positive electrode for a lithium ion battery or a positive electrode for a sodium ion battery. The method for compression molding the positive electrode composition for a secondary battery is not particularly limited, and methods such as roll pressing and pressing with a press can be used. From the viewpoint of the performance (energy density, output characteristics, etc.) of the secondary battery, the electrode density of the electrode for a secondary battery obtained by compression molding the positive electrode composition for a lithium ion battery is 1.0 to 4.0 g / cm in the case of a positive electrode for a lithium ion battery. 3 is preferably 2.5 to 4.0 g / cm 3 In the case of a positive electrode for a sodium ion battery, it is more preferable that the content is 2.5 to 3.5 g / cm. 3 It is preferable that: The positive electrode for a secondary battery obtained using the positive electrode composition for a secondary battery of the present invention has a high electrode density (approximately 3.0 g / cm 3 ) which generally tends to deteriorate the electrolyte permeability. 3 Even in the above cases, the electrolyte permeability is excellent. The electrode density defined here means the density in a state where the electrolyte has not been permeated into the positive electrode composition for a secondary battery.

[0055] When the positive electrode composition for a secondary battery is a slurry positive electrode composition containing a solvent, it is preferable to remove the solvent by drying before compression molding (hereinafter, an electrode manufactured via a slurry electrode composition containing a solvent may be referred to as a "slurry electrode"). The lithium ion battery electrode of the present invention may be the above-mentioned slurry electrode, or may be an electrode produced by a dry process that does not use a solvent (hereinafter, sometimes referred to as a "dry electrode"). When the lithium ion battery electrode of the present invention is a dry electrode, it is not particularly limited, but a dry electrode containing a fibrillar resin such as polytetrafluoroethylene resin (PTFE) as a binder resin is preferred, as in the secondary battery electrode described in JP 2022-103141 A. Also preferred is a dry electrode containing coated negative electrode active material particles for lithium ion batteries and a conductive filler, as in the lithium ion battery negative electrode described in JP 2023-163593 A.

[0056] <Secondary battery> The secondary battery of the present invention includes the positive electrode for secondary batteries of the present invention, and since the electrolyte solution is sufficiently permeated into the positive electrode, it has excellent charge / discharge efficiency (Coulomb efficiency) and direct current resistance (DCR).

[0057] Examples of secondary batteries include lithium ion batteries and sodium ion batteries.

[0058] Known materials can be used for the components of the secondary battery of the present invention other than the positive electrode for the secondary battery. That is, known materials can be used for the negative electrode, current collector, electrolyte, separator, and the like. The electrolyte preferably uses, as a non-aqueous solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), or a mixture thereof. The electrolyte contained in the electrolyte can be any electrolyte used in known electrolytes. For example, a lithium salt can be used in the case of a lithium ion battery, and a sodium salt can be used in the case of a sodium ion battery.

[0059] Examples of lithium salts include lithium salts of inorganic anions such as LiPF, LiBF, LiSbF, LiAsF, LiClO, and LiN(FSO), and lithium salts of organic anions such as LiN(CFSO), LiN(CFS0), and LiC(CFSO). Of these, LiPF (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), and the like are preferably used.

[0060] Examples of sodium salts include inorganic sodium salts such as NaPF6, NaBF4, NaClO4, and NaAsF6, and organic sodium salts such as NaCF3SO3, NaN(CF3SO2)2, NaN(C2F5SO2)2, NaN(FSO2)2, and NaC(CF3SO2)3. Of these, NaPF6 is preferred from the viewpoint of battery output and charge / discharge cycle characteristics.

[0061] The secondary battery of the present invention can be used as a secondary battery for use in mobile phones, personal computers, hybrid vehicles, electric vehicles, stationary power sources, and the like.

[0062] The present specification discloses the following:

[0063] The present disclosure (I) is a positive electrode composition for a secondary battery containing a positive electrode active material, a binder resin, and an additive, wherein the additive is a compound (P) that satisfies all of the following (i) to (iii): (i) The solubility parameter of the compound (P) is 9.0 to 12.0 (cal / cm 3 ) 1 / 2 is; (ii) The compound (P) is a compound represented by the following general formula (1): A-(EO) m -B (1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repetitions of the ethyleneoxy group, and (EO) m is a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group.

[0064] The present disclosure (II) is the positive electrode composition for a secondary battery according to the present disclosure (I), in which the weight ratio of the atomic group A based on the weight of the polyoxyethylene chain is 50% by weight or less, and the weight ratio of the atomic group B based on the weight of the polyoxyethylene chain is 50% by weight or less.

[0065] The present disclosure (III) is a positive electrode composition for a secondary battery according to the present disclosure (I) or (II), in which m in the above general formula is a number of 5 to 22.

[0066] The present disclosure (IV) is a positive electrode composition for a secondary battery according to any one of the present disclosures (I) to (III), in which the content of the compound (P) is 0.05 to 1.5 wt % based on the weight of the positive electrode active material.

[0067] The present disclosure (V) is a positive electrode for a secondary battery obtained by compression molding the positive electrode composition for a secondary battery according to any one of the present disclosures (I) to (IV).

[0068] The present disclosure (VI) is a secondary battery comprising the positive electrode for secondary batteries according to the present disclosure (V). [Example]

[0069] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples as long as they do not deviate from the gist of the present invention. Unless otherwise specified, parts mean parts by weight and % means % by weight.

[0070] <Preparation of additive: compound (P)> The following compounds (P-1) to (P-22) and comparative compounds (Comparative P-1) to (Comparative P-18) were prepared. For each compound, the atomic group A, the group contained in atomic group A, atomic group B, the group contained in atomic group B, the number of repeating ethyleneoxy groups m, the SP value, the ratio of the total weight percentage of atomic group A and atomic group B to the weight percentage of polyoxyethylene chain (total of atomic group A and atomic group B / polyoxyethylene chain), the weight percentage of atomic group A based on the weight of polyoxyethylene chain, and the weight percentage of atomic group B based on the weight of polyoxyethylene chain are shown in Table 1. For compounds (P-1) to (P-22), the numbers of the corresponding general formulas (2) to (11) are also shown. Note that (Comparative P-1) to (Comparative P-5) are compounds that do not have a polyoxyethylene chain and cannot be represented by the structure of general formula (1). (Comparative P-6) to (Comparative P-18) are compounds that have a structure represented by general formula (1) but do not satisfy one or more of the features specific to the invention of claim 1 (the number of repeating ethyleneoxy groups, the structure at both ends, or the SP value).

[0071] (Compound (P-1)) The compound (P-1) was obtained as an ethylene oxide adduct of ethanol by adding ethylene oxide (EO) to ethanol. The average number of moles of EO added was 7.

[0072] (Compound (P-2)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as compound (P-2). The average number of moles of EO added was 5.

[0073] (Compound (P-3)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as compound (P-3). The average number of moles of EO added was 7.

[0074] (Compound (P-4)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as compound (P-4). The average number of moles of EO added was 22.

[0075] (Compound (P-5)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as compound (P-5). The average number of moles of EO added was 30.

[0076] (Compound (P-6)) PEG400 (manufactured by Sanyo Chemical Industries, Ltd.) was used as compound (P-6).

[0077] (Compound (P-7)) PEG1000 (manufactured by Sanyo Chemical Industries, Ltd.) was used as compound (P-7).

[0078] (Compound (P-8)) Methanolamine was reacted with di-tert-butyl dicarbonate to protect the amino group with a tert-butoxycarbonyl group (Boc group protection). To this was added 7 moles of EO to 1 mole of the compound, yielding a 7 mole EO adduct of Boc-protected methanolamine (EO adduct to the hydroxyl group of methanolamine). Next, 454 parts of the 7 mole EO adduct of Boc-protected methanolamine and 40 parts of sodium hydroxide were placed in a pressure-resistant reactor equipped with a thermometer, a heating / cooling device, a stirrer, and a dropping bomb. The atmosphere was replaced with nitrogen at 30°C. The vessel was then reduced in pressure, and 64 parts of ethyl chloride was added dropwise, keeping the temperature below 50°C. After the dropwise addition, the mixture was further aged for 8 hours. After the reaction was completed, 180 parts of water was added, the mixture was stirred at 70°C for 1 hour, and then allowed to stand for 1 hour. The separated upper layer was recovered, and Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added at a ratio of 1% of the weight of the recovered upper layer, and the mixture was stirred. After the Kyoward 600 was removed by suction filtration, the mixture was reacted with trifluoroacetic acid to deprotect the Boc group, and the by-product tert-butanol was removed under reduced pressure to obtain compound (P-8).

[0079] (Compound (P-9)) Methanolamine was reacted with di-tert-butyl dicarbonate to protect the amino group with a tert-butoxycarbonyl group (Boc group protection). Seven moles of EO were added to 1 mole of the compound, yielding a 7-mole EO adduct of Boc-protected methanolamine (EO adduct of methanolamine to the hydroxyl group of methanolamine). Next, 454 parts of the 7-mole EO adduct of Boc-protected methanolamine and 40 parts of sodium hydroxide were placed in a pressure-resistant reactor equipped with a thermometer, a heating / cooling device, a stirrer, and a dropping bomb. The atmosphere was purged with nitrogen at 30°C. The vessel was then reduced in pressure, and 50 parts of methyl chloride was added dropwise, keeping the temperature below 50°C. After the dropwise addition, the mixture was further aged for 8 hours. After the reaction was completed, 180 parts of water was added, the mixture was stirred at 70°C for 1 hour, and then allowed to stand for 1 hour. The separated upper layer was recovered, and Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added in an amount of 1% of the weight of the recovered upper layer, and the mixture was stirred. After the Kyoward 600 was removed by suction filtration, the mixture was reacted with trifluoroacetic acid to deprotect the Boc group, and the by-product tert-butanol was removed under reduced pressure to obtain compound (P-9).

[0080] (Compound (P-10)) 265.5 parts of compound (P-1) and 116.5 parts of sodium monochloroacetate were charged into a glass reaction vessel equipped with stirring and temperature control, and the temperature was maintained at 50°C while the degree of vacuum was gradually increased to 10 KPa. Subsequently, 45 parts of granular sodium hydroxide were charged over 2 hours while dehydrating under reduced pressure, and aging was further carried out for 6 hours. After completion of the reaction, 350 parts of water were added, and the mixture was acidified with 133 parts of 35% hydrochloric acid. After stirring for 30 minutes, the mixture was allowed to stand for 3 hours, and the liquid was separated and the lower liquid containing by-product salt was discarded to obtain compound (P-10).

[0081] (Compound (P-11)) A glass reactor equipped with stirring and temperature control was charged with 254 parts of compound (P-3) and 116.5 parts of sodium monochloroacetate, and the temperature was maintained at 50°C while the vacuum was gradually increased to 10 KPa. Subsequently, 45.2 parts of granular sodium hydroxide were charged over 2 hours while dehydrating under reduced pressure, and the mixture was further aged for 6 hours. After the reaction was completed, 350 parts of water was added, and the mixture was acidified with 133 parts of 35% hydrochloric acid. The mixture was stirred for 30 minutes, then allowed to stand for 3 hours, and the mixture was separated and the lower liquid containing by-product salt was discarded to obtain compound (P-11).

[0082] (Compound (P-12)) NH2-PEG8-NH2 (Sigma-Aldrich, reagent grade) was used as compound (P-12).

[0083] (Compound (P-13)) Polyoxyethylene bis(amine) MW1000 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as compound (P-13).

[0084] (Compound (P-14)) Carboxylic Acid (COOH) PEG MW300 (manufactured by Biopharma PEG) was used as compound (P-14).

[0085] (Compound (P-15)) Carboxylic Acid (COOH) PEG MW1000 (manufactured by Biopharma PEG) was used as compound (P-15).

[0086] (Compound (P-16)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as compound (P-16). The average number of moles of EO added was 15.

[0087] (Compound (P-17)) Methanolamine was reacted with di-tert-butyl dicarbonate to protect the amino group with a tert-butoxycarbonyl group (Boc group protection). To this was added 15 moles of EO to 1 mole of the compound, yielding a 15 mole EO adduct of Boc-protected methanolamine (EO added to the hydroxyl group of methanolamine). Next, 807 parts of the 15 mole EO adduct of Boc-protected methanolamine and 40 parts of sodium hydroxide were placed in a pressure-resistant reactor equipped with a thermometer, a heating / cooling device, a stirrer, and a dropping bomb. The atmosphere was replaced with nitrogen at 30°C. The vessel was then reduced in pressure, and 50 parts of methyl chloride was added dropwise, keeping the temperature below 50°C. After the dropwise addition, the mixture was further aged for 8 hours. After the reaction was completed, 180 parts of water was added, the mixture was stirred at 70°C for 1 hour, and then allowed to stand for 1 hour. The separated upper layer was recovered, and Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added in an amount of 1% of the weight of the recovered upper layer, and the mixture was stirred. After the Kyoward 600 was removed by suction filtration, the mixture was reacted with trifluoroacetic acid to deprotect the Boc group, and the by-product tert-butanol was removed under reduced pressure to obtain compound (P-17).

[0088] (Compound (P-18)) 519 parts of compound (P-16) and 116.5 parts of sodium monochloroacetate were charged into a glass reaction vessel equipped with a stirrer and temperature control, and the temperature was maintained at 50°C while the degree of vacuum was gradually increased to 10 KPa. Subsequently, 45 parts of granular sodium hydroxide were charged over 2 hours while dehydrating under reduced pressure, and the mixture was further aged for 6 hours. After completion of the reaction, 350 parts of water were added, and the mixture was acidified with 133 parts of 35% hydrochloric acid. After stirring for 30 minutes, the mixture was allowed to stand for 3 hours, and the liquid was separated and the lower liquid containing by-product salt was discarded to obtain compound (P-18).

[0089] (Compound (P-19)) A glass reactor equipped with a stirrer and temperature control was charged with 1000 parts of PEG1000 (Sanyo Chemical Industries, Ltd.), 236 parts of succinic acid, and 0.5 parts of paratoluenesulfonic acid as an esterification catalyst. The mixture was gradually heated to 190 ° C under a nitrogen atmosphere and subjected to an esterification reaction for 10 hours at a reduced pressure of 2.7 kPa. The mixture was cooled to 95 ° C, and Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added at a ratio of 1% based on the theoretical weight of the reactant. After stirring, Kyoward 600 was removed by suction filtration to obtain compound (P-22).

[0090] ((Compound (P-20)) In a glass reaction vessel equipped with a stirrer and a temperature control function, 398 parts of compound (P-11) and 108 parts of phenylenediamine were heated with stirring under a nitrogen atmosphere, and then the mixture was reacted at 150° C. while being dehydrated under a reduced pressure of 30 mmHg. After confirming that no more water was distilled, the reaction was terminated to obtain compound (P-20).

[0091] ((Compound (P-21)) In a glass reaction vessel equipped with a stirrer and a temperature control function, 1208 parts of compound (P-19) and 216 parts of phenylenediamine were heated with stirring under a nitrogen atmosphere, and then the mixture was reacted at 150° C. while being dehydrated under a reduced pressure of 30 mmHg. After confirming that no more water was distilled, the reaction was terminated to obtain compound (P-21).

[0092] ((Compound (P-22)) A glass reactor equipped with a stirrer and temperature control was charged with 1,000 parts of PEG1000 (Sanyo Chemical Industries, Ltd.), 178 parts of 3-aminopropionic acid, and 0.5 g of paratoluenesulfonic acid as an esterification catalyst. The mixture was gradually heated to 200°C under a nitrogen atmosphere and subjected to an esterification reaction for 10 hours at a reduced pressure of 2.7 kPa. The mixture was cooled to 95°C, and Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added at a ratio of 1% based on the theoretical weight of the reactant. After stirring, the Kyoward 600 was removed by suction filtration to obtain compound (P-22).

[0093] (Comparative compound (comparison P-1)) 1-Octanol (Tokyo Chemical Industry Co., Ltd., reagent grade) was used as a compound (comparison P-1).

[0094] (Comparative compound (comparison P-2)) Acetic acid (Tokyo Chemical Industry Co., Ltd., reagent grade) was used as a compound (comparison P-2).

[0095] (Comparative compound (comparison P-3)) Azelaic acid (Tokyo Chemical Industry Co., Ltd., reagent grade) was used as a compound (comparison P-3).

[0096] (Comparative compound (comparison P-4)) 8-Amino-1-octanol (Tokyo Chemical Industry Co., Ltd., reagent grade) was used as a compound (comparison P-4).

[0097] (Comparative compound (comparison P-5)) 1,8-Diaminooctane (Tokyo Chemical Industry Co., Ltd., reagent grade) was used as a compound (comparison P-5).

[0098] (Comparative compound (comparison P-6)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as (composition P-6). The average number of moles of EO added was 3.

[0099] (Comparative compound (comparison P-7)) The ethylene oxide adduct of methanol produced by adding EO to methanol was obtained as (composition P-7). The average number of moles of EO added was 50.

[0100] (Comparative compound (comparison P-8)) The ethylene oxide adduct of n-butanol (composition P-8) was produced by adding EO to n-butanol. The average number of moles of EO added was 7.

[0101] (Comparative compound (comparison P-9)) The ethylene oxide adduct of isodecyl alcohol (comparison P-9) was obtained by adding EO to isodecyl alcohol. The average number of moles of EO added was 8.

[0102] (Comparative compound (comparison P-10)) 158 parts of 4-aminodecane and 1.3 parts of potassium hydroxide were placed in a pressure-resistant reactor equipped with a thermometer, heating / cooling device, stirrer, and dropping bomb. After purging with nitrogen, the reactor was sealed and heated to 100°C. The pressure was then reduced to 3 mmHg and stirred for 1 hour. The temperature was then raised to 150°C, and 308 parts of ethylene oxide was added dropwise over 5 hours while adjusting the pressure to 0.5 MPa (G) or less. The mixture was then aged at the same temperature for 3 hours to obtain an ethylene oxide adduct of 4-aminodecane (comparison P-10). The average number of moles of EO added was 7.

[0103] (Comparative compound (comparison P-11)) An ethylene oxide adduct of 4-aminodecane was obtained as (Ratio P-11) in the same manner as in the production of (Ratio P-10), except that the charging ratio of 4-aminodecane to ethylene oxide was changed so that the average number of moles of EO added was 40. The average number of moles of EO added was 40.

[0104] (Comparative compound (comparison P-12)) A glass reactor equipped with stirring and temperature control was charged with 466 parts of compound (compound P-10) and 153 parts of acetic anhydride, and the mixture was heated to 120-150°C and reacted for approximately 1.5 hours. The reaction mixture was then washed with water to separate and recover the by-product acetic acid and unreacted acetic anhydride, followed by dehydration at a temperature of 110°C and a reduced pressure of 10 mmHg or less to obtain (compound P-12).

[0105] (Comparative compound (comparison P-13)) EO was added to dodecyl alcohol to obtain a 7-mol ethylene oxide adduct of dodecyl alcohol. Next, 494 parts of the 7-mol ethylene oxide adduct of dodecyl alcohol and 116.5 parts of sodium monochloroacetate were charged into a glass reaction vessel equipped with stirring and temperature control. While maintaining the temperature at 50°C, the pressure was gradually reduced to 10 kPa. Subsequently, 45.2 parts of granular sodium hydroxide were added over 2 hours while dehydrating under reduced pressure, and the mixture was further aged for 6 hours. After the reaction was completed, 350 parts of water was added, and the mixture was acidified with 133 parts of 35% hydrochloric acid. After stirring for 30 minutes, the mixture was allowed to stand for 3 hours, and the mixture was separated and the bottom liquid containing by-product salt was discarded to obtain (comparison P-13).

[0106] (Comparative compound (comparison P-14)) EO was added to dimethylaminoethanol to obtain a 7-mol EO adduct of dimethylaminoethanol. Next, 397 parts of the 7-mol EO adduct of dimethylaminoethanol and 40 parts of sodium hydroxide were added to a pressure-resistant reactor equipped with a thermometer, a heating / cooling device, a stirrer, and a dropping bomb. The atmosphere was replaced with nitrogen at 30°C. The vessel was then reduced in pressure, and 50 parts of methyl chloride were added dropwise, ensuring the temperature did not exceed 50°C. After the dropwise addition, the mixture was further aged for 8 hours. After the reaction was completed, 180 parts of water was added, the mixture was stirred at 70°C for 1 hour, allowed to stand for 1 hour, and the separated upper layer was recovered. Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added at a ratio of 1% by weight of the recovered upper layer, and the mixture was stirred. The Kyoward 600 was then removed by suction filtration to obtain (comparison P-14).

[0107] (Comparative compound (comparison P-15)) 339 parts of compound (P-3) and 153 parts of acetic anhydride were placed in a glass reaction vessel equipped with a stirrer and temperature control, a thermometer, a stirrer, and a reflux condenser, and the reaction was carried out for about 1.5 hours by heating to 120-150°C. The reaction product was then washed with water to separate and recover the by-product acetic acid and unreacted acetic anhydride, followed by dehydration at a temperature of 110°C and a reduced pressure of 10 mmHg or less to obtain (compound P-15).

[0108] (Comparative compound (comparison P-16)) EO was added to methanol to obtain a 20-mol EO adduct of methanol. Next, 896 parts of the 20-mol EO adduct of methanol and 40 parts of sodium hydroxide were added to a pressure-resistant reactor equipped with a thermometer, a heating / cooling device, a stirrer, and a dropping bomb. The atmosphere was replaced with nitrogen at 30°C. The vessel was then reduced in pressure, and 50 parts of methyl chloride were added dropwise, ensuring the temperature did not exceed 50°C. After the dropwise addition, the mixture was further aged for 8 hours. After the reaction was completed, 180 parts of water was added, the mixture was stirred at 70°C for 1 hour, allowed to stand for 1 hour, and the separated upper layer was recovered. Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added at a ratio of 1% by weight of the recovered upper layer, and the mixture was stirred. The Kyoward 600 was then removed by suction filtration to obtain (comparison P-16).

[0109] (Comparative compound (comparison P-17)) PEG2000 (manufactured by Sanyo Chemical Industries, Ltd.) was used (comparison P-17).

[0110] (Comparative compound (comparison P-18)) Diethylene glycol (Tokyo Chemical Industry Co., Ltd., reagent grade) was used (comparison P-18).

[0111] [Table 1]

[0112] (Preparation of positive electrode active material) The following positive electrode active materials were prepared. NCM:LiNi 0.8 Co0.1 Mn 0.1 O2 (manufactured by Nantong Reshine New Material Co., Ltd., product name "RL-08-D3")

[0113] (Preparing the binder resin) The following binder resins were prepared: Polyvinylidene fluoride: Product name "#9300", manufactured by Kishida Chemical Co., Ltd. (referred to as "PVDF" in Tables 2 and 3) PTFE: Polytetrafluoroethylene (product name "Polyflon PTFE F-104", manufactured by Daikin Industries, Ltd.)

[0114] (Preparation of conductive additive) The following conductive additives were prepared. Acetylene black: trade name "Li-100", manufactured by Denka Co., Ltd. (referred to as "AB" in Tables 2, 3, and 4)

[0115] (Examples 1 to 24 and Comparative Examples 1 to 19: Preparation of electrode compositions (positive electrode compositions) and slurry electrodes (positive electrodes) for lithium ion batteries) The positive electrode active material, binder resin, conductive additive, and compound (P) or comparative compound (relative P) were weighed out according to the parts shown in Table 2 or Table 3, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration of the composition became 70%, and the mixture was stirred at 2000 rpm for 5 minutes using a planetary stirring type mixer / kneader (Awatori Rentaro [manufactured by Thinky Corporation]) to prepare a positive electrode slurry. Each of the obtained positive electrode slurries was applied in air to one side of a current collector (aluminum foil: thickness 10 μm) using a film applicator with a digital film thickness adjustment function so that the active material weight was 10 mg / cm. 2The electrode sheet was then coated with a 16 mm diameter electrode sheet and dried in a circulating air dryer at 100°C for 20 minutes to form a positive electrode layer on the current collector. (Hereinafter, the current collector and positive electrode layer will be collectively referred to as the electrode sheet.) Nine 16 mm diameter electrode sheets were punched out near the center of the obtained electrode sheet, which were then dried in a vacuum dryer at 120°C for 3 hours and then pressed twice for 3 seconds at 1.5 MPa in a press to produce electrodes (3 pieces) for evaluating electrolyte permeability and electrodes (positive electrodes) (6 pieces) for battery evaluation. The electrode sheet was also cut into pieces with a cutter to have a width of 2.5 cm and a length of 8.0 cm. The pieces were then dried in a vacuum dryer at 120°C for 3 hours and then pressed in a roll press (manufactured by Tester Sangyo Co., Ltd.) to produce an electrode density of approximately 3.5 g / cm. 3 The electrode (positive electrode) for the peel test was prepared by pressing the electrode so that the thickness became equal to that of the positive electrode. Similarly, the electrode sheet was cut with a cutter to a width of 4.0 cm and a length of 8.0 cm, dried at 120°C for 3 hours in a vacuum dryer, and then pressed with a roll press (manufactured by Tester Sangyo Co., Ltd.) to an electrode density of approximately 3.5 g / cm. 3 The electrode (positive electrode) for bending test was prepared.

[0116] <Calculation of electrode density> The weight and thickness of the current collector and the electrode for evaluating electrolyte permeability were measured after two cycles of pressing at 1.5 MPa for 3 seconds, and the density was calculated using the following formula: The electrode densities shown in Tables 2 and 3 were calculated by averaging the weight and thickness of each of the three electrodes for evaluating electrolyte permeability in each Example and Comparative Example. Electrode density (g / cm 3 ) = (Electrode weight for electrolyte permeability evaluation (g) - Current collector weight (μg) x 10 -3 ) / (0.8 2 × 3.14 × ((electrode thickness for electrolyte permeability evaluation (μm) - current collector thickness (μm)) × 10 -4 ))

[0117] <Evaluation of electrolyte permeability (electrolyte permeation time) of slurry electrodes for lithium-ion batteries> 3 μL of electrolyte solution was dropped onto the electrodes for evaluating electrolyte solution permeability prepared in Examples 1 to 24 and Comparative Examples 1 to 19, and the time (minutes) until the electrolyte solution permeated into the electrode was measured. A shorter permeation time indicates better permeability. The measurement results are shown in Tables 3 and 4. When the electrolyte solution is dropped onto the electrode for evaluating electrolyte permeability, the color of the portion where the electrolyte solution is dropped becomes darker. Since the color returns to its original state when the electrolyte solution soaks into the electrode, the time (minutes) until the color of the electrode for evaluating electrolyte permeability returns to its original state was measured and used as the electrolyte permeation time (minutes). Note that the electrolyte permeation time of three electrodes for each example and comparative example was measured in 1-second increments, and the arithmetic mean value was used as the electrolyte permeation time (minutes). For each of the Examples and Comparative Examples, the electrolyte permeability was evaluated for three types of electrolytes: electrolyte 1 (EC / DEC = 1 / 1 (volume ratio), LiPF61M), electrolyte 2 (EC / DMC / EMC = 1 / 2 / 2 (volume ratio), LiPF61M), and electrolyte 3 (EC / EMC / DEC = 3 / 5 / 2 (volume ratio), LiPF61M). In the above, EC stands for ethylene carbonate, DMC stands for dimethyl carbonate, EMC stands for ethyl methyl carbonate, and DEC stands for diethyl carbonate. LiPF6 stands for lithium hexafluorophosphate.

[0118] <Peel testing of slurry electrodes for lithium-ion batteries (evaluation of adhesive strength between current collector and positive electrode (positive electrode layer))> A double-sided tape (Nichiban Nicetack: model number NW-K15) was attached to the electrode composition surface of the electrode (positive electrode) for peel test prepared in Examples 1 to 24 and Comparative Examples 1 to 19, and the electrode composition surface was attached to a SUS plate (thickness 1.2 mm) so that it faced each other to prepare a test specimen. The metal foil (aluminum foil) on one end of the test piece was peeled off from the SUS plate, and an interfacial fracture test was performed to peel the electrode composition from the current collector using a 20 N test jig at a tensile speed of 150 mm / min, with the SUS plate held in the chuck of the lower test jig and the metal foil held in the chuck of the upper jig of a bench-top precision universal testing machine (Autograph AGS-X, manufactured by Shimadzu Corporation). The measurement results were read in accordance with JIS K 6854-2:1999 to determine the average peel strength (N). The average peel strength was divided by the width of the test piece (0.025 m) and recorded as the interfacial fracture strength (N / m). The greater the interfacial destructive force, the higher the adhesive strength between the current collector and the positive electrode (positive electrode layer).

[0119] <Bending test of slurry electrodes for lithium-ion batteries (evaluation of bending resistance)> The bending test electrodes prepared in Examples 1 to 24 and Comparative Examples 1 to 19 were wrapped around a round rod of a predetermined Φ (mm) with both ends fixed, with the surface on which the positive electrode layer was formed facing outward, and a 100 g weight was suspended from the electrode. The test began with a round rod of Φ = 5 mm, and the diameter was gradually reduced to Φ = 4 mm, 3 mm, 2 mm, and 1 mm. The Φ (mm) at which the electrode began to crack was visually observed, and this is shown in Tables 3 and 4 as the crack initiation Φ (mm). If no cracks occurred in the electrode even with Φ=1 mm, it was recorded as "<1 mm." The smaller the crack initiation diameter (mm), the less likely it is to crack even when bent, and the greater the electrode strength.

[0120] (Preparation of lithium-ion battery (using slurry electrode) for charge / discharge test) Starting from the positive electrode side, the battery evaluation electrodes (positive electrodes) prepared in Examples 1 to 24 and Comparative Examples 1 to 19, a separator [product name "#3501", manufactured by Celgard Inc.], and lithium foil were stacked in this order, and after injecting electrolyte 1 (EC / DEC = 1 / 1 (volume ratio), LiPF61M), the mixture was vacuum laminated to prevent oxygen from entering, thereby preparing batteries for charge / discharge tests.

[0121] <Charge / discharge test> The initial performance of the charge / discharge test battery prepared in the above (Preparation of lithium-ion battery for charge / discharge test (using slurry electrode)) was evaluated at 25°C using a charge / discharge measuring device "HJ-SD8" (manufactured by Hokuto Denko Corporation). <Initial Coulombic Efficiency Measurement> Using the constant current constant voltage charging method (also known as CCCV mode), the battery was charged to 4.2V at a current of 0.05C, and then maintained at 4.2V until the current reached 0.0025C. After a 10-minute break, the battery was discharged to 2.5V at a current of 0.05C. The charged capacity was defined as [initial charge capacity (mAh)], and the discharged capacity was defined as [initial discharge capacity (mAh)]. The initial coulombic efficiency was calculated using the following formula, and the results are shown in Tables 2 and 3. For each example and comparative example, measurements were performed on three batteries, and the initial coulombic efficiency (%) was calculated, and the arithmetic mean value was used as the analytical value. Initial coulomb efficiency (%) = [initial discharge capacity] / [initial charge capacity] x 100 <10sDCR measurement method> In addition, the electrical resistance value (10sDCR) was calculated from the voltages measured at the start of discharge and after 10 seconds in the charge / discharge test using the following formula. 10sDCR(Ω·cm 2 ) = ([Voltage before discharge (V)] - [Voltage 10 seconds after discharge (V)]) / [Discharge current (A)] × 1.77 (1.77 cm 2 ) The smaller the 10sDCR, the smaller the internal resistance, which is preferable.

[0122] <Discharge capacity maintenance rate> The battery for charge / discharge test prepared as described above (Preparation of Lithium-ion Battery for Charge / Discharge Test (Using Slurry Electrode)) was charged to 4.2 V at a current of 0.5 C using a constant current / constant voltage (CCCV) charging method. Then, while maintaining 4.2 V, it was charged until the current reached 0.05 C. After a 10-minute rest, it was discharged to 2.5 V at a current of 0.5 C. This charge / discharge cycle was repeated 10 times. The battery capacity at the first charge (initial discharge capacity) and the battery capacity at the 10th charge cycle (discharge capacity after 10 cycles) were used to calculate the discharge capacity retention rate according to the following formula. The results are shown in Tables 2 and 3. Note that a larger value indicates less battery degradation after repeated charge / discharge. For each example and comparative example, the discharge capacity retention rate (%) was calculated for three batteries, and the arithmetic average value was used as the analytical value. Discharge capacity retention rate (%) = [Discharge capacity at 10th cycle] / [Discharge capacity at 1st cycle]

[0123] [Table 2]

[0124] [Table 3]

[0125] Tables 2 and 3 show that the electrodes (positive electrodes) of Examples 1 to 24 have higher electrolyte permeability and superior electrode strength (less likely to break when bent, and higher adhesive strength with the current collector) compared to the electrodes of Comparative Examples 1 to 19. Furthermore, the initial coulombic efficiency, internal resistance, and discharge capacity retention rate of the batteries of each Example were comparable to those of the battery containing no additive (Comparative Example 1), indicating that the inclusion of compound (P) had almost no adverse effect on these battery performances.

[0126] (Examples 25 to 29, Comparative Examples 20 to 22: Preparation of dry electrodes (dry positive electrodes) for lithium ion batteries) The positive electrode active material, binder resin, and conductive additive were weighed out according to the parts listed in Table 4 and premixed at room temperature using a universal mixer, high-speed mixer FS25 (manufactured by EarthTechnica Corporation) (50 rpm, 15 minutes), followed by mixing using a high-speed mixer (500 rpm, 1 minute). Subsequently, the compound (P) or (component P) in the number of parts listed in Table 4 was added, and further mixing was performed using the universal mixer, high-speed mixer FS25 (5000 rpm, 3 minutes, 80°C) to obtain a positive electrode composition. The positive electrode composition obtained above was formed into a bulk shape (thickness: approximately 1.5 mm) and rolled into a sheet. The rolling was carried out by heating to 80°C. The rolled sheet obtained above was then roughly crushed by folding it in half, and again formed into a bulk shape. After that, it was rolled into a sheet shape using a metal roll on a flat plate, and this process of promoting fibrillation was repeated four times. Further rolling was then carried out to obtain a dry positive electrode sheet with a thickness of 500 μm. Furthermore, the dry positive electrode sheet was cut out and placed in a press for rolling. Furthermore, a load of 5 kN was repeatedly applied to adjust the thickness, thereby obtaining a dry electrode (dry positive electrode). The final electrode density was approximately 3.0 g / cm 3 The mixture was rolled to a thickness of 100 mm. Nine pieces with a diameter of 16 mm were punched out from the center of the obtained dry electrode (dry positive electrode) to prepare three dry electrodes for evaluating electrolyte permeability, six dry electrodes for battery evaluation, and three dry electrodes for evaluating electrode strength.

[0127] The weight and thickness of the 16 mm diameter dry electrode for evaluating electrolyte permeability obtained above were measured and calculated using the following formula: The electrode density shown in the table was calculated by averaging the weight and thickness of each of three dry electrodes for evaluating electrolyte permeability in each Example and Comparative Example. Electrode density (g / cm 3 ) = Weight of dry electrode for electrolyte permeability evaluation (g) / (0.8 2 × 3.14 × (thickness of dry electrode for electrolyte permeability evaluation (μm)) × 10 -4 )

[0128] <Evaluation of electrolyte permeability (electrolyte permeation time) of dry electrodes for lithium-ion batteries> The electrolyte permeability was evaluated in the same manner as for the above slurry electrodes, except that the dry electrodes for evaluating electrolyte permeability produced in Examples 25 to 29 and Comparative Examples 20 to 22 were used as test pieces. The results are shown in Table 4.

[0129] <Bending test of dry electrodes for lithium-ion batteries (evaluation of bending resistance)> The dry electrodes (dry positive electrodes) for evaluating electrode strength prepared in Examples 25 to 29 and Comparative Examples 20 to 22 were used as test pieces, and the electrode strength was evaluated by a three-point bending test in accordance with ISO178 (Plastics - Determination of bending properties). The dry electrode for electrode strength evaluation (dry positive electrode) was placed on a jig with a support distance of 5 mm, and a load cell (rated load: 20 N) set in an autograph (manufactured by Shimadzu Corporation) was lowered toward the electrode at a speed of 1 mm / min. Three dry electrodes for electrode strength evaluation of each example and comparative example were measured, and the arithmetic mean value was taken as the electrode strength (kPa) for each level. The greater the electrode strength (kPa), the less likely it is to break even when bent, and the greater the electrode strength.

[0130] (Preparation of lithium-ion batteries (using dry electrodes) for charge / discharge tests) Starting from the positive electrode side, the dry electrodes (positive electrodes) for battery evaluation (produced in Examples 25 to 29 and Comparative Examples 20 to 22), a separator (product name "#3501", manufactured by Celgard), and lithium foil were stacked in this order, and after injecting electrolyte 1 (EC / DEC = 1 / 1 (volume ratio), LiPF61M), the mixture was vacuum laminated to prevent oxygen from entering, thereby producing batteries for charge / discharge tests.

[0131] <Charge / discharge test> For the battery for charge / discharge test prepared in the above (Preparation of lithium ion battery for charge / discharge test (using dry electrode)), the initial coulombic efficiency, 10s DCR, and discharge capacity retention rate were measured using the same method as the charge / discharge test method for lithium ion battery for charge / discharge test (using slurry electrode). The evaluation results are shown in Table 4.

[0132] [Table 4]

[0133] Table 4 shows that the electrodes (positive electrodes) of Examples 25 to 29 have higher electrolyte permeability and superior electrode strength (less likely to break when bent) compared to the electrodes of Comparative Examples 20 to 22. Furthermore, the initial coulombic efficiency and internal resistance of the batteries of each Example were comparable to those of a battery containing no additive (Comparative Example 20), indicating that the inclusion of compound (P) had almost no adverse effect on these battery performances.

Claims

1. A positive electrode composition for a secondary battery containing a positive electrode active material, a binder resin, and an additive, The positive electrode composition for a secondary battery, wherein the additive is a compound (P) that satisfies all of the following (i) to (iii): (i) The solubility parameter of the compound (P) is 9.0 to 12.0 (cal / cm ３ ) １／２ is; (ii) The compound (P) is a compound represented by the following general formula (1): 2-(59) ｍ 3(1) [In the formula, EO is an ethyleneoxy group, m is a number of 5 to 30 representing the average number of repeating ethyleneoxy groups, and (EO) ｍ is a polyoxyethylene chain. A and B each represent an atomic group bonded to the polyoxyethylene chain, and the ratio of the total weight proportion of the atomic group A and the atomic group B to the weight proportion of the polyoxyethylene chain in compound (P) (total of the atomic group A and the atomic group B / polyoxyethylene chain) is 1 / 99 to 49 / 51.] (iii) Either the atomic group A or the atomic group B has one group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group, and the other has one group selected from the group consisting of an alkyl group having 1 to 2 carbon atoms, a hydroxyl group, an amino group, and a carboxyl group.

2. 2. The positive electrode composition for a secondary battery according to claim 1, wherein the weight ratio of the atomic group A based on the weight of the polyoxyethylene chain is 50% by weight or less, and the weight ratio of the atomic group B based on the weight of the polyoxyethylene chain is 50% by weight or less.

3. 2. The positive electrode composition for a secondary battery according to claim 1, wherein m in said general formula is a number from 5 to 22.

4. 2. The positive electrode composition for secondary batteries according to claim 1, wherein the content of the compound (P) is 0.05 to 1.5% by weight based on the weight of the positive electrode active material.

5. A positive electrode for a lithium ion battery obtained by compression molding the positive electrode composition for a secondary battery according to any one of claims 1 to 4.

6. A secondary battery comprising the positive electrode for secondary batteries according to claim 5 .

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