Electrode-forming composition and additives

Abstract

The present invention provides a composition for electrode formation that, via a simple method, suppresses thickening and gelation and improves storage stability, and that enables a high concentration of solid content. Provided is a composition for electrode formation comprising a heterocycle-containing compound, a positive electrode active material, a binder, and a solvent, wherein the heterocycle-containing compound has a five-membered ring heterocycle having not less than two N atoms and has at least one group selected from the group consisting of a hydroxy group and a thiol group.

Description

[Technical Field]

[0001] The present invention relates to an electrode-forming composition and an additive. [Background technology]

[0002] Lithium-ion secondary batteries have a high energy density per weight and volume, which contributes to the miniaturization and lightening of electronic devices. In recent years, the spread of electric vehicles has accelerated as part of efforts to achieve zero-emissions automobiles, and there is a demand for batteries with even lower resistance, longer life, higher capacity, safety, and lower cost.

[0003] Lithium-ion batteries generally have a three-layer structure consisting of a positive electrode, a separator, and a negative electrode, all of which contain an electrolyte. The positive and negative electrodes are manufactured by, for example, coating a current collector with an electrode slurry, which is a mixture of an active material, a conductive material, and a binder. Currently, the most common method for manufacturing negative electrodes is to coat a copper foil current collector with the negative electrode slurry and then dry it. The most common method for manufacturing positive electrodes is to prepare a positive electrode slurry using an organic solvent such as N-methylpyrrolidone as the solvent, and then coat the aluminum foil current collector with the positive electrode slurry.

[0004] Inorganic compounds such as transition metal oxides and transition metal chalcogens containing alkali metals are known as positive electrode active materials for lithium-ion secondary batteries, as they can provide a battery voltage of around 4 V. Among these, highly alkaline positive electrode active materials containing large amounts of nickel and manganese are used to obtain high-capacity lithium-ion secondary batteries.

[0005] For example, Li x High-nickel positive electrode active materials, such as NiO2, have a high discharge capacity and are attractive positive electrode materials, but alkaline components such as LiOH, Li2O, LiHCO3, and Li2CO3 are generated on the surface through proton exchange reactions with raw material residues or moisture, and reactions with moisture and carbon dioxide in the air.

[0006] When such a positive electrode active material is used, the electrode slurry may thicken or gel, gradually losing its fluidity, which not only makes it difficult to achieve a uniform coating thickness but also makes it impossible to apply the electrode slurry, resulting in waste of material.

[0007] The main cause of this is thought to be that during the process of producing the positive electrode, alkaline components present on the surface of the positive electrode active material, in the presence of trace amounts of moisture, promote the dehydrofluorination reaction of the fluorine-based binder, such as PVdF, which has a vinylidene fluoride structure and is used as a binder.

[0008] Furthermore, alkaline components corrode the aluminum foil commonly used as a current collector for the positive electrode, thereby increasing the resistance of the battery, and may also react with the electrolyte in the battery, increasing the resistance of the battery and shortening its lifespan.

[0009] The thickening and gelation described above can be suppressed by handling the raw materials and the electrode slurry in a dry environment and controlling the water content. However, this requires large-scale facilities for a series of mass production processes from the preparation of the electrode slurry to the manufacture of the battery, and also poses problems of increased costs and increased environmental load due to the use of large amounts of electricity.

[0010] To solve this problem, for example, Patent Document 1 discloses a technique for suppressing gelation of an electrode slurry by preparing the electrode slurry (cathode material slurry) so that it does not exhibit strong alkalinity even when dispersed in water. However, preparing an electrode slurry that does not exhibit strong alkalinity using the method described in Patent Document 1 not only requires strict pH control, but also requires a process in which the cathode active material is first dispersed in water, filtered to extract the cathode active material from the dispersion, and then dried. This results in cumbersome operations and a reduced yield. Furthermore, such a process may cause a decrease in the performance of the cathode active material itself.

[0011] Furthermore, Patent Document 2 reports a technology that uses a compound such as ultra-high molecular weight (weight average molecular weight of 2.2 million or more) polyethylene oxide to bind water through interactions with water (e.g., hydrogen bonding), thereby suppressing the reaction between the alkaline component of the positive electrode active material and water, thereby suppressing thickening and gelation. However, ultra-high molecular weight polymers with strong thickening effects require time and cost to dissolve uniformly in a solvent, and also have handling issues such as the difficulty of producing a highly concentrated solution. Furthermore, because the above-mentioned ultra-high molecular weight polymers have a high ability to bind water, there is a concern that the polymer itself may bring in water, and to prevent this, strict control over pre-drying is required.

[0012] Patent Documents 3 and 4 propose adding an organic or inorganic acid to the positive electrode of a lithium-ion secondary battery to prevent gelation of the electrode slurry (positive electrode mixture slurry). Patent Document 3 uses maleic acid, citraconic acid, and malonic acid in the positive electrode mixture, while Patent Document 4 uses acetic acid, phosphoric acid, sulfuric acid, or the like in the electrode slurry (positive electrode paste). However, neutralizing the alkali with an acid requires the addition of a large amount of acid, which may result in a decrease in the energy density of the battery or an increase in the battery resistance. Another problem is that the acid corrodes the device used to fabricate the electrode.

[0013] Patent Document 5 reports a method for treating a positive electrode active material with fluorine gas and immobilizing the remaining LiOH as LiF, thereby preventing gelation and suppressing gas generation. However, fluorine gas is highly toxic and difficult to handle. In addition, LiF produced as a by-product increases the internal resistance of the battery, reducing capacity, and corrosion of the positive electrode active material by fluorine gas also reduces capacity. Furthermore, there is a problem in that the residual fluorine reacts with traces of moisture present in the active material and electrolyte to produce hydrogen fluoride, which easily causes cycle deterioration.

[0014] Patent Document 6 reports that unreacted lithium hydroxide and impurities derived from raw materials can be removed by washing with an aqueous solution containing a lithium salt. However, this method has issues such as increased environmental impact due to the wastewater generated during washing and the costs associated with treating the wastewater. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-90917 [Patent Document 2] Japanese Patent Application Publication No. 2019-121471 [Patent Document 3] Japanese Patent Application Publication No. 9-306502 [Patent Document 4] Japanese Patent Application Publication No. 10-79244 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-286240 [Patent Document 6] International Publication No. 2017-034001 Summary of the Invention [Problem to be solved by the invention]

[0016] In light of the above circumstances, the present invention aims to provide an electrode-forming composition that can suppress thickening and gelation of electrode slurries using a simple method, thereby improving storage stability, increasing the solid content concentration, and suppressing battery deterioration, as well as an additive that is effective in suppressing gelation of electrode-forming compositions. [Means for solving the problem]

[0017] The inventors of the present invention have conducted extensive research to achieve the above-mentioned object, and have found that adding a specific heterocycle-containing compound having a five-membered heterocycle with two or more N atoms and at least one group selected from the group consisting of a hydroxyl group and a thiol group to an electrode-forming composition containing at least a positive electrode active material, a binder, and a solvent can suppress thickening and gelation of the composition and improve storage stability. Furthermore, electrodes fabricated using the electrode-forming composition of the present invention can suppress deterioration in batteries caused by alkaline components and can also improve battery performance.

[0018] That is, the present invention provides the following electrode-forming composition and additives. 1. An electrode-forming composition comprising a heterocycle-containing compound, a positive electrode active material, a binder, and a solvent, The electrode-forming composition is one in which the heterocycle-containing compound has a five-membered heterocycle having two or more N atoms and at least one group selected from the group consisting of a hydroxy group and a thiol group. 2. The electrode-forming composition according to 1, wherein the heterocycle-containing compound is a heterocycle-containing compound represented by any one of the following formulas (1) to (5): [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3. 3. R ​​above a ~R d and X a 10. The electrode-forming composition of claim 2, wherein the substituent is at least one selected from the group consisting of a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, a halogen atom, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, and a thiol group. 4. R above a ~R d 2 or 3. The electrode-forming composition of claim 2, wherein at least one of the groups is a hydroxy group or a thiol group. 5. Above X a are each independently a hydrogen atom, a lithium atom, or a sodium atom. 6. An electrode-forming composition according to any one of 1 to 5, further comprising a conductive additive. 7. The electrode-forming composition according to any one of 1 to 6, wherein the positive electrode active material contains 30 mass % or more of S, Fe or Ni. 8. The electrode-forming composition according to any one of 1 to 7, further comprising a dispersant, the dispersant being a polymer containing a pyrrolidone structure or a nitrile group. 9. The electrode-forming composition of 8, wherein the dispersant is at least one selected from the group consisting of polyvinylpyrrolidone and polyacrylonitrile. 10. The electrode-forming composition of any one of 1 to 9, wherein the content of the heterocycle-containing compound is 0.001 to 0.5 mass % of the solid content. 11. An additive for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5): [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R fare each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3. 12. 11 additives that are gelation inhibitors. 13. An additive solution for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive solution comprising an additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5) and a solvent. [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R fare each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3. [Effects of the Invention]

[0019] The electrode-forming composition of the present invention is resistant to thickening and gelation and has high storage stability, making it suitable for use in forming positive electrodes for energy storage devices. When an energy storage device is manufactured using the composition, benefits such as improved quality and yield due to the improved storage stability of the composition, cost reduction and reduced environmental impact due to a high solids concentration, and suppression of deterioration within the battery caused by alkaline components can be expected, contributing to reduced manufacturing costs for the energy storage device and improved battery characteristics.

[0020] Although the mechanisms of the thickening and gelation and the suppression effect are unclear, it is believed that the addition of a specific heterocycle-containing compound to the electrode-forming composition forms a protective film on the surface of the alkaline component. This protective film suppresses the reaction between the alkaline component and the binder, particularly the fluorine-based binder, thereby suppressing the thickening and gelation of the composition and improving its storage stability. Suppressing the thickening and gelation of the electrode-forming composition improves the dispersibility of solid components such as the positive electrode active material and conductive additive, enabling the formation of a homogeneous positive electrode layer. It also improves the solid concentration in the electrode slurry, reducing the cost and environmental impact of producing energy storage devices. Furthermore, it can suppress corrosion of aluminum foil, commonly used as a current collector foil, and the degradation of battery characteristics due to reaction with the electrolyte, which are caused by the alkaline component. However, these are speculations, and the present invention should not be interpreted as being limited to these mechanisms. DETAILED DESCRIPTION OF THE INVENTION

[0021] The electrode-forming composition of the present invention is an electrode-forming composition comprising a heterocycle-containing compound, a positive electrode active material, a binder, and a solvent, wherein the heterocycle-containing compound has a five-membered heterocycle having two or more N atoms and at least one group selected from the group consisting of a hydroxy group and a thiol group.

[0022] The heterocyclic compound is preferably a heterocyclic compound represented by any one of the following formulas (1) to (5), more preferably a heterocyclic compound represented by any one of formulas (1), (2), (4), and (5), and particularly preferably a heterocyclic compound represented by any one of formulas (1) and (4).

[0023] [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R eis an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3.

[0024] In the above formulas (1) to (4), L is a single bond and R a ~R d At least one of X is a hydrogen atom or a halogen atom, or a is a hydrogen atom, a lithium atom, or a sodium atom, they may be structural isomers. Specifically, isomers of the heterocycle-containing compound represented by formula (1) include heterocycle-containing compounds represented by formulas (1-A) to (1-C) below, isomers of the heterocycle-containing compound represented by formula (2) include heterocycle-containing compounds represented by formulas (2-A) to (2-D) below, isomers of the heterocycle-containing compound represented by formula (3) include heterocycle-containing compounds represented by formulas (3-A) to (3-C) below, and isomers of the heterocycle-containing compound represented by formula (4) include heterocycle-containing compounds represented by formulas (4-A) to (4-C) below. a ~R d When at least one of the groups is a hydroxyl group or a thiol group, they can become a ketone group or a thioketone group, thereby creating a structural isomer.

[0025] [ka]

[0026] Z is N and CR d is preferred.

[0027] R a ~Rd The alkyl group having 1 to 6 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include linear or branched alkyl groups having 1 to 6 carbon atoms such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, and n-hexyl group; and cyclic alkyl groups having 3 to 6 carbon atoms such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, and cyclohexyl group.

[0028] R a ~R d Examples of the alkenyl group having 2 to 6 carbon atoms represented by the formula (I) include an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, and an n-1-pentenyl group.

[0029] R a ~R d Examples of the aryl group having 6 to 12 carbon atoms represented by the formula (I) include a phenyl group, a tolyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0030] Above R a and R c Examples of the ring having 4 to 12 carbon atoms formed by bonding together include a cyclopentane ring, a cyclohexane ring, a benzene ring, a naphthalene ring, a triazole ring, a pyridine ring, and a pyrazine ring.

[0031] Above R a ~R dmay have a substituent. Examples of the substituent include a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, a halogen atom, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, and a thiol group. Examples of the alkoxysilyl group include a trimethoxysilyl group, a dimethoxymethylsilyl group, a methoxydimethylsilyl group, a triethoxysilyl group, a diethoxymethylsilyl group, and an ethoxydimethylsilyl group. In the present invention, a carboxy group, a hydroxy group, and a thiol group are preferred. The above R a ~R d When has a substituent, the number of the substituents is preferably 1 to 6, and more preferably 1 to 3.

[0032] Above R a ~R d Examples of the alkyl group include a hydrogen atom, a carboxy group, a hydroxy group, a thiol group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, and R a and R c are preferably bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent.

[0033] Also, the above R a ~R d Examples of the alkyl group include a hydrogen atom, a carboxy group, a hydroxy group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, and R a and R c However, it is more preferable that they are bonded to each other to form an aromatic ring having 4 to 12 carbon atoms which may have a substituent.

[0034] Furthermore, the above R a ~R d Examples of the alkyl group include a hydrogen atom, a carboxy group, a hydroxy group, a thiol group, an alkyl group having 1 to 3 carbon atoms, an aryl group having 6 to 10 carbon atoms, and R a and R c are bonded to each other to form an aromatic ring having 6 to 10 carbon atoms which may have a substituent.

[0035] Furthermore, the above R a ~R d Examples of the alkyl group include a hydrogen atom, a carboxy group, a hydroxy group, a thiol group, a methyl group, a phenyl group, and R a and R b More preferred is an optionally substituted benzene ring formed by bonding together:

[0036] In addition, the heterocycle-containing compound is R a ~R d At least one of the groups is preferably a hydroxy group or a thiol group.

[0037] L is preferably a single bond, an ester bond or an amide bond, and more preferably a single bond.

[0038] X a The alkyl group having 1 to 6 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include linear or branched alkyl groups having 1 to 6 carbon atoms such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, and n-hexyl group; and cyclic alkyl groups having 3 to 6 carbon atoms such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, and cyclohexyl group.

[0039] X a Examples of the aryl group having 6 to 12 carbon atoms represented by the formula (I) include a phenyl group, a tolyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0040] Above X amay have a substituent. Examples of the substituent include a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, a halogen atom, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, and a thiol group. Examples of the alkoxysilyl group include a trimethoxysilyl group, a dimethoxymethylsilyl group, a methoxydimethylsilyl group, a triethoxysilyl group, a diethoxymethylsilyl group, and an ethoxydimethylsilyl group. In the present invention, a carboxy group, a hydroxy group, a thiol group, and an alkoxysilyl group are preferred, and a carboxy group and a trimethoxysilyl group are more preferred. The above X a When has a substituent, the number of the substituents is preferably 1 to 6, and more preferably 1 to 3.

[0041] R e The alkyl group having 1 to 10 carbon atoms and represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include linear or branched alkyl groups having 1 to 10 carbon atoms, such as a methyl group, ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group, n-octyl group, n-nonyl group, and n-decyl group; and cyclic alkyl groups having 3 to 10 carbon atoms, such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and 1-adamantyl group.

[0042] R e Examples of the alkanol group having 1 to 10 carbon atoms represented by the formula include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxypentyl group, a hydroxyhexyl group, a hydroxyoctyl group, a hydroxynonyl group, and a hydroxydecyl group.

[0043] R eExamples of the alkenyl group having 2 to 10 carbon atoms represented by the formula (I) include an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, an n-1-pentenyl group, and an n-1-decenyl group.

[0044] R e Examples of the aryl group having 6 to 12 carbon atoms represented by the formula (I) include a phenyl group, a tolyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0045] Above X a Examples of the alkyl group include a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, and -CHNR e 2 is preferred.

[0046] Also, the above X a Examples of the alkyl group include a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, and -CHNR e 2 is preferred.

[0047] Furthermore, the above X a Examples of the alkyl group include a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 3 carbon atoms, an aryl group having 6 to 8 carbon atoms, and -CHNR e 2 is more preferred.

[0048] Furthermore, the above X a Examples include a hydrogen atom, a lithium atom, a sodium atom, a methyl group, a phenyl group, and -CHNR e 2 is even more preferred.

[0049] Furthermore, the above X a As the atom, a hydrogen atom, a lithium atom and a sodium atom are more preferred.

[0050] Furthermore, the above X a As the atom, a hydrogen atom is most preferred.

[0051] Above R e As the alkyl group, an alkyl group having 1 to 3 carbon atoms and an aryl group having 6 to 10 carbon atoms are preferred, and a methyl group and a phenyl group are more preferred.

[0052] R f The alkyl group having 1 to 6 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include linear or branched alkyl groups having 1 to 6 carbon atoms such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, and n-hexyl group; and cyclic alkyl groups having 3 to 6 carbon atoms such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, and cyclohexyl group.

[0053] R f Examples of the alkenyl group having 2 to 6 carbon atoms represented by the formula (I) include an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, and an n-1-pentenyl group.

[0054] R f Examples of the aryl group having 6 to 12 carbon atoms represented by the formula (I) include a phenyl group, a tolyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0055] Above R f Preferred examples of the alkyl group include a halogen atom, a carboxy group, a hydroxy group, an ester group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0056] Above R fMore preferred examples of the alkyl group include a halogen atom, a carboxy group, a hydroxy group, an ester group, a phenyl group, an alkoxysilyl group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0057] Above R f As the alkyl group, a hydroxy group, a thiol group and a methyl group are more preferred.

[0058] n is preferably 0 to 2, and more preferably 1 to 2.

[0059] As the heterocycle-containing compounds represented by the above formulas (1) to (5), heterocycle-containing compounds represented by the following formulas (1a) to (5a) are preferred.

[0060] [ka] (In the formula, R a ~R c , R f , Z and X a is the same as above.)

[0061] The heterocycle-containing compound is more preferably a heterocycle-containing compound represented by any one of the following formulae (1b) and (3b) to (5b).

[0062] [ka] (In the formula, R a ~R c , R f and Z are the same as above.)

[0063] Specific examples of the heterocycle-containing compound represented by the above formula (1) include heterocycle-containing compounds represented by the following formulae (1-1) to (1-7).

[0064] [ka]

[0065] Specific examples of the heterocycle-containing compound represented by the above formula (2) include heterocycle-containing compounds represented by the following formulas (2-1) to (2-2).

[0066] [ka]

[0067] Specific examples of the heterocycle-containing compound represented by the above formula (3) include the heterocycle-containing compound represented by the following formula (3-1).

[0068] [ka]

[0069] Specific examples of the heterocycle-containing compound represented by the above formula (4) include heterocycle-containing compounds represented by the following formulae (4-1) to (4-4).

[0070] [ka]

[0071] Specific examples of the heterocycle-containing compound represented by the above formula (5) include the heterocycle-containing compound represented by the following formula (5-1).

[0072] [ka]

[0073] The content of the heterocycle-containing compound is preferably 0.001 to 4 mass% of the solid content, more preferably 0.001 to 2 mass%, even more preferably 0.001 to 0.5 mass%, even more preferably 0.001 to 0.3 mass%, and particularly preferably 0.001 to 0.2 mass%. An even more preferable lower limit of the content of the heterocycle-containing compound is 0.01 mass% of the solid content. By keeping the content of the heterocycle-containing compound within the above range, the adhesion between the current collector and the electrode layer can be improved, and the battery characteristics of the resulting battery can be maintained. In the present invention, the solid content refers to the components other than the solvent that constitute the composition (the same applies hereinafter).

[0074] The positive electrode active material preferably contains 30% by mass or more of S, Fe, or Ni, because it improves battery capacity, uses fewer rare metals, and is low cost. In the present invention, considering further reductions in the amount of rare metals used and the need to obtain a battery with a longer life, a material containing 35% by mass or more of Fe or Ni is more preferred, and a material containing 45% by mass or more is even more preferred. The upper limit is not particularly limited, but is typically 65% ​​by mass or less. Such a positive electrode active material can be appropriately selected from various active materials conventionally used in electrodes for energy storage devices such as secondary batteries, and can be used if it satisfies the above conditions. For example, in the case of lithium secondary batteries or lithium ion secondary batteries, chalcogen compounds or lithium ion-containing chalcogen compounds capable of adsorbing and desorbing lithium ions, polyanionic compounds, elemental sulfur and its compounds, etc. can be used.

[0075] Examples of lithium ion-containing chalcogen compounds include LiNiO2, Li x Ni y M 1-y O2 (M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, and 0.05≦x≦1.10, 0.3≦y≦1.0), Li a Ni (1-x-y) Co x M 1 y M2 z X w O2(M 1 is at least one selected from the group consisting of Mn and Al, M 2 represents at least one selected from the group consisting of Zr, Ti, Mg, B, Zr, W, and V, and examples thereof include 1.00≦a≦1.50, 0.00≦x≦0.50, 0≦y≦0.50, 0.000≦z≦0.020, and 0.000≦w≦0.020). Examples of polyanion compounds include LiFePO 4、 Li a Mn b Fe c D d PO4 (wherein 1.00≦a≦1.15, 0.01≦b≦0.99, 0.01≦c≦0.99, 0.00≦d≦0.10, D is selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, and at least a portion of which has an olivine structure). Examples of sulfur compounds include sulfur, Li2S, FeS2, TiS2, MoS2, and rubeanic acid. These positive electrode active materials can be used alone or in combination of two or more.

[0076] In the present invention, among the above positive electrode active materials, Li a Ni (1-x-y) Co x M 1 y M 2 z X w O2(M 1 is at least one selected from the group consisting of Mn and Al, M 2 represents at least one selected from the group consisting of Zr, Ti, Mg, W, and V, preferably 1.00≦a≦1.50, 0.00≦x≦0.50, 0≦y≦0.50, 0.000≦z≦0.020, 0.000≦w≦0.020. These positive electrode active materials can be used singly or in combination of two or more.

[0077] The content of the positive electrode active material is preferably 88.0 to 99.949 mass % of the solid content, more preferably 88.0 to 99.899 mass %, and even more preferably 95.0 to 99.0 mass %.

[0078] The binder can be appropriately selected from known materials and is not particularly limited. Specific examples include fluorine-based binders such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, copolymers containing at least one monomer selected from the group consisting of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene, and non-aqueous binders such as polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, polyethylene, and polypropylene. In the present invention, the use of a fluorine-based binder is preferred from the viewpoint of improving the storage stability of the composition. Furthermore, the fluorine-based binder is preferably modified with a polar functional group such as a carboxyl group or a hydroxyl group. The polar functional group can be confirmed by the presence or absence of a clear peak detected in the range of 10 to 15 ppm in measurement using a nuclear magnetic resonance (NMR) spectrometer. The binders can be used alone or in combination of two or more.

[0079] The weight average molecular weight (Mw) of the binder is usually about 600,000 to 3,000,000, preferably 700,000 to 2,000,000, and more preferably 700,000 to 1,500,000, from the viewpoint of improving the adhesion between the current collector and the electrode layer. The weight average molecular weight is a polystyrene-equivalent value determined by gel permeation chromatography (GPC).

[0080] From the viewpoint of reducing costs and obtaining a high energy density, the content of the binder is preferably 0.05 to 8 mass % of the solid content, more preferably 0.05 to 5 mass %, even more preferably 0.05 to 4 mass %, still more preferably 0.1 to 3 mass %, particularly preferably 0.2 to 2 mass %, and most preferably 0.3 to 1.5 mass %.

[0081] The electrode-forming composition of the present invention may further contain a conductive additive to improve electrical conductivity. Examples of the conductive additive include carbon materials such as graphite, carbon black, acetylene black (AB), vapor-grown carbon fiber, carbon nanotubes (CNT), carbon nanohorns, and graphene, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. The conductive additives may be used alone or in combination of two or more.

[0082] When the conductive additive is contained, its content is not particularly limited, but is preferably 0.05 to 5 mass % of the solid content, more preferably 0.05 to 4 mass %, even more preferably 0.1 to 3 mass %, and even more preferably 0.2 to 2 mass %. By keeping the content of the conductive additive within the above range, good electrical conductivity can be obtained.

[0083] The electrode-forming composition of the present invention may further contain a dispersant to improve the dispersibility of the active material and conductive additive. The dispersant can be selected from those conventionally used as dispersants for conductive carbon materials such as CNTs. However, from the viewpoint of stability within the battery, it is preferable to contain a nonionic polymer. Examples of the nonionic polymer include polyvinylpyrrolidone (PVP) and polymers having at least one group selected from the group consisting of a nitrile group, a hydroxy group, a carbonyl group, an amino group, a sulfonyl group, and an ether group. Specific examples of the polymer include polyvinyl alcohol, polyacrylonitrile, polylactic acid, polyester, polyimide, polyphenyl ether, polyphenylsulfone, polyethyleneimine, and polyaniline. In the present invention, polymers containing a pyrrolidone structure or a nitrile group are preferred, and polyvinylpyrrolidone and polyacrylonitrile are more preferred. The dispersants can be used alone or in combination.

[0084] When the dispersant is contained, its content is not particularly limited, but is preferably 0.001 to 0.5 mass% of the solid content, more preferably 0.001 to 0.3 mass%, and even more preferably 0.001 to 0.2 mass%. An even more preferable lower limit of the content of the dispersant is 0.01 mass% of the solid content. Furthermore, in consideration of the adhesion between the resulting electrode layer and the current collector, the total amount of the heterocycle-containing compound and the dispersant is preferably 0.001 to 1 mass % of the solid content, and more preferably 0.01 to 1 mass %.

[0085] The electrode-forming composition of the present invention contains a solvent. The solvent is not particularly limited as long as it is one that has conventionally been used in preparing electrode-forming compositions, and examples thereof include water; ethers such as tetrahydrofuran (THF), diethyl ether, and 1,2-dimethoxyethane (DME); halogenated hydrocarbons such as methylene chloride, chloroform, and 1,2-dichloroethane; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP); ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butanol. Examples of suitable solvents include alcohols; aliphatic hydrocarbons such as n-heptane, n-hexane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and organic solvents such as γ-butyrolactone, dimethyl sulfoxide (DMSO), dioxolane, and sulfolane. These solvents can be used alone or in combination of two or more.

[0086] The binder may be used by dissolving or dispersing it in these solvents as required. Suitable solvents in this case include water, NMP, DMSO, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, THF, dioxolane, sulfolane, DMF, DMAc, and the like. The solvent may be appropriately selected depending on the type of binder. NMP is suitable for water-insoluble binders such as PVdF, and water is suitable for water-soluble binders.

[0087] The solid content of the electrode-forming composition of the present invention is appropriately set taking into consideration the coatability of the composition, the thickness of the electrode to be formed, and the like, but is typically about 60 to 92 mass %, preferably about 65 to 90 mass %, and more preferably about 70 to 85 mass %.

[0088] The viscosity of the electrode-forming composition of the present invention is set appropriately taking into consideration the coating method, the thickness of the electrode to be formed, etc., but is typically about 100 to 2,000,000 mPa·s, preferably about 300 to 1,000,000 mPa·s, and more preferably about 400 to 800,000 mPa·s. The above viscosity is a value measured at 25°C using an E-type viscometer.

[0089] The electrode-forming composition of the present invention can be obtained by mixing the above-mentioned components. When the composition contains optional components other than the additive (heterocycle-containing compound) of the present invention, the positive electrode active material, and the binder, the positive electrode additive and the active material may be mixed together with the optional components, or both components may be mixed in advance and then mixed with the optional components. Either method can achieve the effects of the present invention.

[0090] The electrode of the present invention comprises an electrode layer made of the electrode-forming composition described above on at least one surface of a substrate serving as a current collector. A method for forming an electrode layer on a substrate includes applying a prepared electrode-forming composition to a substrate to form a coating film, followed by drying the coating film. This method is not particularly limited, and various conventionally known methods can be used. Specific examples of coating methods include various printing methods such as offset printing and screen printing, blade coating, dip coating, spin coating, bar coating, slit coating, inkjet printing, and die coating.

[0091] When drying the coating film, either natural drying or heat drying may be used, but heat drying is preferred from the viewpoint of production efficiency. When heat drying is performed, the temperature is preferably about 50 to 400°C, and more preferably about 70 to 150°C.

[0092] 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. In particular, the thickness of the substrate is not particularly limited, but in the present invention, it is preferably 1 to 100 μm, more preferably 3 to 30 μm, and most preferably 5 to 25 μm.

[0093] The thickness of the electrode layer is not particularly limited, but is preferably about 0.01 to 1,000 μm, more preferably about 5 to 300 μm. When the electrode layer is used as an electrode alone, the thickness is preferably 10 μm or more.

[0094] The electrode may be pressed as necessary. A commonly used pressing method can be used, with mold pressing and roll pressing being particularly preferred. The pressing pressure is not particularly limited, but is preferably 1 kN / cm or more, more preferably 2 kN / cm or more, and more preferably 5 kN / cm or more. The upper limit of the pressing pressure is not particularly limited, but is preferably 50 kN / cm or less.

[0095] The secondary battery of the present invention is provided with the above-described electrodes, and more specifically, is configured with at least one pair of positive and negative electrodes, a separator interposed between the electrodes, and an electrolyte, and the positive electrode is configured with the above-described electrode. Other constituent members of the battery element may be appropriately selected from conventionally known components.

[0096] Examples of materials used for the separator include glass fiber, cellulose, porous polyolefin, polyamide, and polyester.

[0097] The electrolyte may be either liquid or solid, and may be either aqueous or non-aqueous. From the viewpoint of easily achieving practically sufficient performance, however, an electrolytic solution composed of an electrolyte salt, a solvent, etc. may be preferably used.

[0098] Examples of the electrolyte salt include LiPF6, LiBF4, and LiN(SO2F) 2、 Examples of the electrolyte salt include lithium salts such as LiN(C2F5SO2)2, LiAsF6, LiSbF6, LiAlF4, LiGaF4, LiInF4, LiClO4, LiN(CF3SO2)2, LiCF3SO3, LiSiF6, LiN(CF3SO2), and (C4F9SO2), metal iodides such as LiI, NaI, KI, CsI, and CaI2, iodide salts of quaternary imidazolium compounds, iodide salts and perchlorates of tetraalkylammonium compounds, and metal bromides such as LiBr, NaBr, KBr, CsBr, and CaBr2. These electrolyte salts can be used alone or in combination of two or more.

[0099] 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; chain esters such as methyl acetate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and nitriles such as acetonitrile. These solvents can be used alone or in combination of two or more.

[0100] In addition, as the solid electrolyte, inorganic solid electrolytes such as sulfide-based solid electrolytes and oxide-based solid electrolytes, and organic solid electrolytes such as polymer-based electrolytes can be suitably used. By using these solid electrolytes, an all-solid-state battery can be obtained that does not require an electrolytic solution.

[0101] The sulfide-based solid electrolyte may be a Li2S-SiS2-lithium compound (wherein the lithium compound is Li3PO 4、 At least one selected from the group consisting of LiI and Li4SiO4 、 LiS-PO 5、 Li2S-B2S 5、 Examples include thiolithium-based materials such as Li2S-P2S5-GeS2.

[0102] The oxide-based solid electrolyte is Li5La3MO, an oxide with a garnet structure. 12 (M=Nb, Ta) and Li7La3Zr2O 12 , γ-Li3PO4 structure-based oxygen acid salt compounds collectively known as LISICON, perovskite type, Li 3.3 PO 3.8 N 0.22 , sodium / alumina, etc. Examples of the polymer solid electrolyte include polyethylene oxide materials and polymer compounds obtained by polymerizing or copolymerizing monomers such as hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride. The polymer solid electrolyte may contain a supporting salt and a plasticizer.

[0103] Examples of the supporting salt contained in the polymer solid electrolyte include lithium (fluorosulfonylimide), and examples of the plasticizer include succinonitrile.

[0104] A battery manufactured using the electrode-forming composition of the present invention has high battery characteristics even though it contains less fluorine binder than a typical secondary battery.

[0105] 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.

[0106] When applied to a coin cell, the electrode of the present invention described above may be punched into a predetermined disk shape for use. 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, placing the electrode of the present invention on top with the electrode layer facing downwards, placing a case and a gasket on top, and sealing the battery with a coin cell crimping machine.

[0107] The present invention also provides an additive for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5): The additive can be suitably used as a gelation inhibitor for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent.

[0108] [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3.

[0109] In formulas (1) to (5), Z and R a ~R d , L, X a , R e and R f Specific examples of the above are the same as those given in the description of the electrode-forming composition.

[0110] The positive electrode active material, binder, and solvent of the electrode-forming composition are also the same as those described above.

[0111] Furthermore, the present invention provides an additive solution for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive solution comprising an additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5), and a solvent. Use of the additive solution of the present invention makes it easier to mix the additive with the electrode-forming composition.

[0112] [ka] (wherein Z is N or CLR) d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L's each independently represent a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X aare each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or -CHNR e 2, R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3.

[0113] In formulas (1) to (5), Z and R a ~R d , L, X a , R e and R f Specific examples of the above are the same as those given in the description of the electrode-forming composition.

[0114] The additive solution is preferably one in which the heterocycle-containing compound represented by any one of formulas (1) to (5) is dissolved or dispersed in a solvent, more preferably one in which the heterocycle-containing compound is dissolved in a solvent.

[0115] Usable solvents include those exemplified in the description of the electrode-forming composition, among which NMP, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate are particularly suitable for use in the present invention.

[0116] The positive electrode active material and binder of the electrode-forming composition are also the same as those described above.

[0117] The solids concentration of the additive solution of the present invention is appropriately set taking into consideration the saturated solubility in the solvent, storage stability, etc., but is usually about 1 to 60 mass %, preferably about 3 to 55 mass %, and more preferably about 3 to 50 mass %. [Example]

[0118] 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 apparatus used is as follows.

[0119] (1) Rotation-revolution type mixer: Thinky Corporation, Awatori Mixer, atmospheric pressure type ARE-310 (2) Dry Booth: Manufactured by Nihon Spindle Manufacturing Co., Ltd. (3) E-type viscometer: VISCOMETER TV-22 manufactured by Toki Sangyo Co., Ltd., measurement temperature: 25°C, rotor: 1°34' x R24. The viscosity was measured 5 minutes after the start of measurement under the following measurement conditions.

[0120] The raw materials used are as follows: <Active material> NCA: Lithium nickel oxide (LiNi 0.88 Co 0.11 Al 0.01 O2, NCA-034H, Ni ratio: 55% by mass), manufactured by Ecopro <Fluorine-based binder> Solef-5130: Polyvinylidene fluoride (PVdF), manufactured by SOLVAY <Conductive additive> AB: Denka Black (registered trademark) Li100 (high-purity acetylene black), manufactured by Denka Co., Ltd. <Solvent> NMP: Nippon Refine Co., Ltd. <Additive A> [Additives used in the examples] A1: 2-Mercaptobenzimidazole, manufactured by Tokyo Chemical Industry Co., Ltd. A2: 5-Mercapto-1-methyltetrazole, manufactured by Tokyo Chemical Industry Co., Ltd. A3: 7-Hydroxy-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine, manufactured by Tokyo Chemical Industry Co., Ltd. [ka] [Additives used in comparative examples] a1: Oxalic acid, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. a2: Piperonylic Acid, manufactured by Tokyo Chemical Industry Co., Ltd. a3:8-Quinolinol, manufactured by Tokyo Chemical Industry Co., Ltd. a4: Anthranil, manufactured by Tokyo Chemical Industry Co., Ltd. a5: Phthalazone, manufactured by Tokyo Chemical Industry Co., Ltd. a6: Pyridine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. [ka]

[0121] Preparation of positive electrode composition (electrode slurry) [Examples 1-1 to 1-3, Comparative Examples 1-1 to 1-7] A 5% by mass NMP solution was prepared for each additive. A 7% by mass NMP solution of PVdF was prepared. The positive electrode active material, binder solution, conductive additive, additive solution, NMP, and water were mixed in a dry mixer to obtain the composition shown in Table 1, and mixed using a rotation-revolution mixer to obtain an electrode slurry. The total amount of the prepared slurries was 20 g each, with a solid content of 80% by mass. The solvent composition of the slurry was adjusted to NMP / HO = 97 / 3 (mass ratio). Note that the water was added to intentionally create a high moisture content in the slurry.

[0122] The viscosity of the slurries obtained above was measured using an E-type viscometer immediately after preparation. After storage at 40°C for 24 hours, the presence or absence of gelation was confirmed visually. For those that did not gel, the viscosity was similarly measured using an E-type viscometer to check for thickening and a tendency toward gelation, and the results were evaluated based on the following criteria. Table 1 also summarizes these evaluations. "Judgment criteria" A: Not gelled B: The composition gelled and could not be used to form electrodes.

[0123] [Table 1]

[0124] From the results in Table 1 above, it was confirmed that the electrode-forming composition of the present invention to which the specific heterocycle-containing compound was added was inhibited from thickening or gelling, and had improved storage stability.

Claims

1. An electrode-forming composition comprising a heterocycle-containing compound, a positive electrode active material, a binder, and a solvent, The electrode-forming composition, wherein the heterocycle-containing compound is a heterocycle-containing compound represented by any one of the following formulas (1) to (5): 【Chemical 1】 wherein Z is N or C-L-R d ; R a to R d each independently represent a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent; R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent; L each independently represents a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a s each independently represent a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or —CH 2 NR e 2 ; R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R f s each independently represent a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; n is an integer from 0 to 3.

2. The above R a ~R d and X a 2. The electrode-forming composition according to claim 1, wherein the substituent of is at least one selected from the group consisting of a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, a halogen atom, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, and a thiol group.

3. The above R a ~R d 2. The electrode-forming composition according to claim 1, wherein at least one of the groups is a hydroxy group or a thiol group.

4. Above X a 2. The electrode-forming composition according to claim 1, wherein each of the groups independently represents a hydrogen atom, a lithium atom, or a sodium atom.

5. The electrode-forming composition according to claim 1 , further comprising a conductive assistant.

6. 2. The electrode-forming composition according to claim 1, wherein the positive electrode active material contains 30 mass % or more of S, Fe or Ni.

7. 2. The electrode-forming composition according to claim 1, further comprising a dispersant, the dispersant being a polymer containing a pyrrolidone structure or a nitrile group.

8. 8. The electrode-forming composition according to claim 7, wherein the dispersant is at least one selected from the group consisting of polyvinylpyrrolidone and polyacrylonitrile.

9. 9. The electrode-forming composition according to claim 1, wherein the content of the heterocycle-containing compound is 0.001 to 0.5% by mass based on the solid content.

10. An additive for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5): 【Chemistry 2】 (Wherein, Z is N or C-L-R d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L each independently represents a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or —CH 2 NR e 2 and R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3.

11. The additive of claim 10, which is a gelation inhibitor.

12. An additive solution for an electrode-forming composition containing a positive electrode active material, a binder, and a solvent, the additive solution comprising an additive comprising a heterocycle-containing compound represented by any one of the following formulas (1) to (5) and a solvent: 【Chemistry 3】 (Wherein, Z is N or C-L-R d and R a ~R d each independently represents a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, R a and R c may be bonded to each other to form a ring having 4 to 12 carbon atoms which may have a substituent, L each independently represents a single bond, a carbonyl group, an ether bond, an ester bond, or an amide bond; X a are each independently a hydrogen atom, a lithium atom, a sodium atom, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or —CH 2 NR e 2 and R e is an alkyl group having 1 to 10 carbon atoms, an alkanol group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R f are each independently a halogen atom, a carboxy group, a hydroxy group, an aldehyde group, an ester group, a ketone group, an amino group, a phenyl group, an alkoxysilyl group, an epoxy group, a carboxylic acid chloride group, a thiol group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, n is an integer from 0 to 3.

Images