Electrode coating film leveling method

Abstract

One embodiment of the present disclosure relates to an electrode coating film leveling method involving applying, to a current collector, an electrode paste for a power storage device, wherein the electrode paste contains a leveling agent for a power storage device, and the leveling agent contains a compound represented by general formula (1). In the general formula (1), R1 represents an alkyl or alkenyl group having 6-14 carbon atoms; EO represents an ethyleneoxy group; PO represents a propyleneoxy group; n and m are each an average addition amount on a mole basis and are each a number of 0-8; the sum of n and m is 8 or less; and R2 represents a hydrogen atom or a methyl group.　(1): R1-O-(EO)n(PO)m-R2

Description

Leveling method for electrode coatings

[0001] The present invention relates to a method for leveling electrode coatings, a leveling agent composition for energy storage devices, a dispersant composition for energy storage devices, a carbon material-based conductive material slurry, an electrode paste for energy storage devices, and the like.

[0002] In recent years, there has been a surge in the development of electric vehicles (EVs) that do not emit carbon dioxide, from the perspective of mitigating global warming. However, EVs have challenges compared to gasoline-powered vehicles, such as shorter driving ranges and longer battery charging times. To shorten charging time, it is necessary to increase the speed of electron movement in the electrodes. Currently, carbon-based conductive materials such as carbon nanotubes and carbon black are used as conductive materials for electrodes. Because these carbon-based conductive materials have strong cohesive properties, they increase the viscosity of the paste used to form the electrode coating. After applying the paste, the coating loses its smoothness before the electrode coating is formed, resulting in defects in the resulting electrode coating. Therefore, it is known that leveling agents are used to improve the smoothness of the electrode coating.

[0003] Japanese Patent Publication No. 2014-130775 (Patent Document 1) discloses a positive electrode composite layer for a non-aqueous electrolyte secondary battery, comprising one or more film-forming agents selected from polyvinyl acetal, polyoxyalkylene, polyacrylic acid, polyvinylpyrrolidone, alkylbenzene sulfonic acid, and their derivatives, with the aim of providing a non-aqueous electrolyte secondary battery with excellent durability. Japanese Patent Publication No. 2023-97438 (Patent Document 2) discloses an amide-modified product and / or neutralized product of a copolymer of olefin and maleic anhydride as a dispersant for energy storage device electrodes, which enables the preparation of a conductive material slurry with good dispersibility of carbon material-based conductive materials and achieves both good solubility in organic solvents at room temperature.

[0004] This disclosure relates, in one embodiment, to a method for leveling an electrode coating, which includes coating a current collector with an electrode paste for an energy storage device containing a leveling agent for an energy storage device that contains a compound represented by the following general formula (1). 1 -O-(EO) n (PO) m-R 2 (1) In the above general formula (1), R 1 represents an alkyl group or an alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are each the average number of added moles and are numbers from 0 to 8, the sum of n and m is 8 or less, and R 2 represents a hydrogen atom or a methyl group.

[0005] In one aspect, the present disclosure relates to a leveling agent composition for a power storage device containing a compound represented by the following general formula (1) and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 represents an alkyl group or an alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are each the average number of added moles and are numbers from 0 to 8, the sum of n and m is 8 or less, and R 2 represents a hydrogen atom or a methyl group.

[0006] In one aspect, the present disclosure relates to a dispersant composition for a power storage device containing a leveling agent for a power storage device containing a compound represented by the following general formula (1), a polymer dispersant, and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 represents an alkyl group or an alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are each the average number of added moles and are numbers from 0 to 8, the sum of n and m is 8 or less, and R 2 represents a hydrogen atom or a methyl group.

[0007] This disclosure relates, in one aspect, to a leveling agent for energy storage devices containing a compound represented by the following general formula (1), a carbon material-based conductive material, a polymer dispersant, and an organic solvent, as well as a carbon material-based conductive material slurry. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

[0008] This disclosure relates, in one embodiment, to an electrode paste for an energy storage device comprising a leveling agent for an energy storage device containing a compound represented by the following general formula (1), a carbon material-based conductive material, a binder, a positive electrode active material, a polymer dispersant, and an organic solvent. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

[0009] This disclosure relates, in one embodiment, to a method for manufacturing an electrode for an energy storage device, which includes preparing an electrode coating using the electrode paste for energy storage devices of this disclosure.

[0010] This disclosure relates, in one embodiment, to a method for manufacturing an energy storage device, which includes incorporating an electrode for an energy storage device obtained by the method for manufacturing an electrode for an energy storage device of this disclosure.

[0011] This disclosure relates, in one embodiment, to the use of a compound represented by the following general formula (1) as a leveling agent for energy storage devices. 1-O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

[0012] This disclosure relates, in one embodiment, to the use of a leveling agent for energy storage devices containing a compound represented by the following general formula (1) for the manufacture of electrode paste for energy storage devices. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group. Detailed description of the invention

[0013] It is known that improving the dispersibility of carbon-based conductive materials reduces the viscosity of pastes used for electrode coating formation. It is also known that highly dispersing the electrode active material within the paste reduces its viscosity.

[0014] Therefore, this disclosure provides an electrode coating leveling method, etc., which can improve the smoothness of the electrode coating by reducing the viscosity of the paste used for forming the electrode coating.

[0015] This disclosure is based on new findings that including a compound represented by the following general formula (1) (hereinafter also referred to as the "leveling agent") reduces the viscosity of electrode paste for energy storage devices and improves the smoothness of the electrode coating film formed using said electrode paste for energy storage devices. 1 -O-(EO) n (PO)m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

[0016] Although the details of the mechanism by which the effects of this disclosure are realized are not clear, it is presumed that the above leveling agent is included in the electrode paste for energy storage devices which contains a polymer dispersant, R 1 The leveling agent is adsorbed onto carbon-based conductive materials, contributing to improved dispersibility of the carbon-based conductive materials. EO and PO are adsorbed onto electrode active materials, contributing to improved dispersibility of the electrode active materials. Therefore, when an electrode paste for energy storage devices contains the leveling agent, the leveling agent contributes to a decrease in the viscosity of the electrode paste for energy storage devices. As a result, the viscosity-reducing effect of the leveling agent facilitates the volatilization of organic solvents during and after coating of the electrode paste for energy storage devices, improving the smoothness of the electrode coating obtained by drying the coating film. However, this disclosure shall not be interpreted as being limited to these mechanisms.

[0017] In one embodiment, this disclosure provides a leveling method for electrode coatings, which facilitates the volatilization of organic solvents during and after coating the electrode paste for energy storage devices onto the current collector, thereby improving the smoothness of the electrode coating obtained by drying the coating. In one embodiment, this disclosure provides a leveling agent composition for energy storage devices that enables the reduction of viscosity of the electrode paste used for forming the electrode coating, thereby improving the smoothness of the electrode coating. In one embodiment, this disclosure provides a dispersant composition for energy storage devices that includes the leveling agent composition for energy storage devices of this disclosure, thereby enabling the reduction of viscosity of the electrode paste used for forming the electrode coating, thereby improving the smoothness of the electrode coating. In one embodiment, this disclosure provides a carbon material-based conductive material slurry with good dispersibility of carbon material-based conductive materials that includes the leveling agent composition for energy storage devices of this disclosure. In one embodiment, this disclosure provides an electrode paste for energy storage devices that includes the leveling agent composition for energy storage devices of this disclosure, enabling the formation of an electrode coating film with low viscosity and excellent smoothness. In one embodiment, this disclosure enables the production of an electrode coating film for an energy storage device using the electrode paste for energy storage devices of this disclosure, thereby enabling the productive manufacture of electrodes for energy storage devices that include an electrode coating film with excellent smoothness. In one embodiment, this disclosure enables the production of energy storage devices by incorporating the electrodes for energy storage devices of this disclosure.

[0018] <Leveling Agent for Energy Storage Devices> This disclosure relates, in one embodiment, to a leveling agent for electrodes of energy storage devices. The leveling agent for energy storage devices of this disclosure (hereinafter sometimes abbreviated as "the leveling agent of this disclosure") includes a compound (leveling agent) represented by the above general formula (1).

[0019] [Leveling agent] In the above general formula (1), R 1 It adsorbs onto carbon-based conductive materials and contributes to improving the dispersibility of carbon-based conductive materials. 1This plays a role in reducing viscosity in carbon material-based conductive material slurries and electrode pastes for energy storage devices. From a productivity standpoint, good solubility in organic solvents is also desirable for leveling agents. This organic solvent is used in the preparation of leveling agent compositions for energy storage devices, dispersant compositions for energy storage devices, carbon material-based conductive material slurries, and electrode pastes for energy storage devices. 1 The number of carbon atoms is 14 or less, preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less, from the viewpoint of improving the solubility of the leveling agent in the organic solvent.

[0020] (EO) in the above general formula (1) n (PO) m It adsorbs onto the electrode active material and contributes to improving the dispersibility of the electrode active material. (EO) n (PO) m It also plays a role in reducing viscosity in carbon material-based conductive material slurries and electrode pastes for energy storage devices. Of (EO) and (PO), (PO) has higher adsorption to electrode active materials. n is preferably 0, and (EO) n (PO) m Preferably (PO) m Therefore, the sum of n and m is 8 or less, preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, even more preferably 3 or less, and preferably 1 or more, even more preferably 2 or more, from the viewpoint of controlling the solubility of the leveling agent in organic solvents.

[0021] In the above general formula (1), R 2 From the viewpoint of controlling the solubility of the leveling agent in organic solvents, this is a methyl group or a hydrogen atom, preferably a hydrogen atom.

[0022] In one embodiment, the leveling agent of this disclosure may consist only of the compound represented by the general formula (1), and not contain any other leveling agents. However, it may also be a mixture of the compound represented by the general formula (1) and other leveling agents, as long as the effects of the present invention are not impaired. From the viewpoint of reducing the viscosity of electrode paste for energy storage devices, the content of the compound represented by the general formula (1) in the leveling agent of this disclosure is preferably substantially 100% by mass, more preferably 100% by mass.

[0023] <Leveling Agent Composition for Energy Storage Devices> In one embodiment, this disclosure relates to a leveling agent composition for electrodes of energy storage devices. The leveling agent composition for energy storage devices of this disclosure (hereinafter sometimes abbreviated as "the leveling agent composition of this disclosure") comprises the leveling agent of this disclosure and a solvent. The content of the solvent in the leveling agent composition of this disclosure is, for example, the residue after excluding the leveling agent and the optional components listed below.

[0024] [Organic solvent] The solvent contained in the leveling agent composition of the present disclosure is preferably an organic solvent. Specifically, the organic solvent is preferably at least one selected from the group consisting of dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethyl acetate, γ-butyrolactone, and ε-caprolactone, more preferably containing highly soluble N-methylpyrrolidone, and even more preferably N-methylpyrrolidone (NMP).

[0025] [Optional Components] The leveling agent compositions of this disclosure may further contain other components, to the extent that the effects of this disclosure are not impaired. Examples of other components include antioxidants, defoamers, preservatives, dehydrators, rust inhibitors, plasticizers, binders, and the like.

[0026] The leveling agent content in the leveling agent composition of this disclosure is not particularly limited, but from the viewpoint of productivity, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and from the viewpoint of controlling solubility in organic solvents, it is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0027] The leveling agent composition of this disclosure can be prepared, for example, by mixing a mixture of the leveling agent and an organic solvent in a stirrer. Examples of the stirrer include rotary stirrers and high-speed stirrers.

[0028] <Dispersant Composition for Energy Storage Devices> This disclosure relates in one aspect to a dispersant composition for energy storage devices. The dispersant composition for energy storage devices of this disclosure (hereinafter sometimes abbreviated as "the dispersant composition of this disclosure") comprises the leveling agent composition of this disclosure and a polymer dispersant. Therefore, the dispersant composition of this disclosure comprises the leveling agent of this disclosure, a polymer dispersant, and an organic solvent. The preferred leveling agent composition and leveling agent of this disclosure used in the preparation of the dispersant composition of this disclosure are as described above. The preferred organic solvent contained in the dispersant composition of this disclosure is the same as the organic solvent suitable for the preparation of the leveling agent composition of this disclosure. The content of the organic solvent in the dispersant composition of this disclosure is, for example, the residue after excluding the leveling agent of this disclosure, the polymer dispersant, and the optional components listed below. Because the dispersant composition of this disclosure contains the leveling agent of this disclosure, it enables the reduction of viscosity of the electrode paste for energy storage devices used to form electrode coatings, and as a result, the smoothness of the electrode coating can be improved.

[0029] [Polymer Dispersant] The polymer dispersant included in the dispersant composition of this disclosure is not particularly limited, but examples include polyvinyl acetal, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral, methylcellulose, styrene butadiene, acrylonitrile butadiene or a part thereof hydrogenated, acrylic copolymer, or a polymer dispersant obtained by neutralizing an amide-modified copolymer of an olefin and maleic anhydride as needed (hereinafter, "polymer dispersant obtained by neutralizing an amide-modified copolymer of an olefin and maleic anhydride as needed" may be abbreviated as "polymer dispersant A"). Among these, polyvinyl acetal and at least one of polymer dispersant A are preferred. The degree of acetalization of polyvinyl acetal is preferably 20 mol% or more and 80 mol% or less, and the weight-average molecular weight is preferably 10,000 or more and 50,000 or less. As polymer dispersant A, for example, the dispersant disclosed in Patent Document 2 can be used.

[0030] The polymer dispersant disclosed in Patent Document 2 includes a constituent unit represented by the following general formula (2) (hereinafter also referred to as "constituent unit I") and a constituent unit represented by the following general formula (3) (hereinafter also referred to as "constituent unit II"). When the amidation rate is less than 100 mol%, the polymer dispersant further includes a constituent unit represented by the following general formula (4) (hereinafter also referred to as "constituent unit III").

[0031] Constituent units I, II, and III all contain a unit represented by the following general formula (5). This unit is responsible for solubility in organic solvents. M, which constitutes constituent units I and II, is a component that contributes to the dispersion of carbon material-based conductive materials in organic solvents. R, which constitutes constituent unit I. 5 This is a hydrophobic group and a component that functions as an adsorption group for carbon material-based conductive materials. At least R of constituent unit II 6 It functions as a spacer, and the long-chain alkyl group R 5 This suppresses the formation of association structures between the polymers and enhances the solubility of the polymer dispersant in organic solvents.

[0032] If the mole fractions of constituent units I, II, and III are b, c, and a, respectively, then b + c + a = 1. The sum of the mole fraction b of constituent unit I and the mole fraction c of constituent unit II, b + c, is also called the amidation rate or denaturation rate when a + b + c = 1. The mole fraction b of constituent unit I is the denaturation rate to constituent unit I, and the mole fraction c of constituent unit II is the denaturation rate to constituent unit II. The polymer dispersant A preferably satisfies the relationships 0.50 < b + c ≤ 1.00 and 0.50 ≤ b / (b + c) ≤ 0.95. If the sum of mole fractions b and c (b + c) exceeds 0.50, it means that the amidation rate to maleic anhydride exceeds 50 mol%, and if the sum of mole fractions b and c (b + c) is 1.00, it means that the amidation rate to maleic anhydride is 100 mol%.

[0033] From the viewpoint of adsorption to carbon material-based conductive materials, the modification rate b is preferably 0.50 or higher, more preferably 0.55 or higher, and even more preferably 0.60 or higher. Furthermore, from the viewpoint of improving solubility in organic solvents at room temperature, it is preferably 0.95 or lower, more preferably 0.90 or lower, even more preferably 0.85 or lower, and even more preferably 0.80 or lower. Note that the modification rate b is the alkyl group R having 16 to 22 carbon atoms used in the synthesis of the polymer dispersant A. 5 It can be calculated from the amount of amine compounds containing the specified compound used.

[0034] From the viewpoint of improving solubility in organic solvents at room temperature, the denaturation rate c is preferably 0.50 or less, more preferably 0.45 or less, and even more preferably 0.40 or less. Furthermore, from the viewpoint of improving solubility in organic solvents, it is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. Note that the denaturation rate c is used in the synthesis of polymer dispersant A. 6 and R 7 It can be calculated from the amount of amine compounds containing the specified compound used.

[0035] The sum of the denaturation rate b and the denaturation rate c is greater than 0.50, preferably 0.55 or more, more preferably 0.65 or more, even more preferably 0.70 or more, even more preferably 0.75 or more, and even more preferably 1.00. The polymer dispersant A may be one or more types selected from those in which the sum of the denaturation rate b and the denaturation rate c is greater than 0.50 and 1.00 or less. The sum of the denaturation rate b and the denaturation rate c is determined by the R used in the synthesis of polymer dispersant A. 5 The amount of amine compound having and R used 6 and R 7 It can be calculated from the total amount of amine compounds containing the specified compound used.

[0036] In the polymer dispersant A, from the viewpoint of adsorption to carbon material-based conductive materials, b / (b+c) is 0.50 or more, preferably 0.55 or more, more preferably 0.60 or more, and from the viewpoint of solubility at room temperature, it is 0.95 or less, preferably 0.90 or less, more preferably 0.85 or less, and even more preferably 0.80 or less. Note that b / (b+c) can be calculated from the amount of the amine compound used in the polymerization of the polymer dispersant A, as described later.

[0037] R 3 This is either a hydrogen atom or a methyl group, preferably a methyl group.

[0038] R 4 R is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aromatic hydrocarbon group having 1 to 10 carbon atoms, either substituted or unsubstituted, preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear or branched. 4 The number of carbon atoms is preferably 2 or more and 7 or less.

[0039] R 5 R is an alkyl group having 16 or more carbon atoms and 22 or less carbon atoms. 5 The number of carbon atoms is preferably 18 or more and 20 or less. 5 Examples of amine compounds used to introduce this compound include cetylamine, 1-aminoheptadecane, stearylamine, 1-aminononadecane, eicosylamine, and behenylamine.

[0040] M is hydrogen, NH4, a metal that yields a salt soluble in organic solvents, or an organic ammonium soluble in organic solvents, preferably hydrogen.

[0041] R 6 This is an alkyl group having 1 to 12 carbon atoms, a saturated hydrocarbon group having 1 to 12 carbon atoms including an alicyclic hydrocarbon group, or a saturated hydrocarbon group having 1 to 12 carbon atoms having a hydroxyl group. 6 The number of carbon atoms is R 5 From the perspective of suppressing the formation of association structures due to hydrophobic interactions between them, R 5 It is less than that of R. 6 The number of carbon atoms is preferably 2 or more from the viewpoint of suppressing the formation of the associated structure, preferably 11 or less from the viewpoint of availability and ease of synthesis of the dispersant, and more preferably 10 or less. 6 The number of hydroxyl groups is preferably 1 or more from the viewpoint of solubility, preferably 2 or less from the viewpoint of reactivity, and more preferably 1 or less. Spacer group R 6 From the viewpoint of solubility and availability, the position of the hydroxyl group is preferably at the end of the spacer group.

[0042] R 7 R is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a saturated hydrocarbon group having 1 to 12 carbon atoms including an alicyclic hydrocarbon group, or a saturated hydrocarbon group having 1 to 12 carbon atoms having a hydroxyl group. 7 For the reason that the solubility of the polymer dispersant in organic solvents at room temperature is improved, it is preferably an alkyl group having 1 to 12 carbon atoms, a saturated hydrocarbon group having 1 to 12 carbon atoms including an alicyclic hydrocarbon group, or a saturated hydrocarbon group having 1 to 12 carbon atoms having a hydroxyl group. 7 The number of carbon atoms is preferably 2 or more from the viewpoint of suppressing the formation of the associated structure, and preferably 11 or less, more preferably 10 or less, from the viewpoint of availability and ease of synthesis of the dispersant. 7 The number of hydroxyl groups is preferably 1 or more from the viewpoint of solubility, preferably 2 or less from the viewpoint of reactivity, and more preferably 1 or less. Spacer group R 7 From the viewpoint of solubility and availability, the position of the hydroxyl group is preferably at the end of the spacer group.

[0043] R 6 and R 7 Examples of amine compounds used to introduce these compounds include isobutylamine, tert-butylamine, n-butylamine, isohexylamine, 2-ethylhexylamine, isooctylamine, n-octylamine, n-butylamine, isodecylamine, diethylamine, dibutylamine, dicyclohexylamine, ethanolamine, N-methylethanolamine, N-ethylethanolamine, 2-amino-1-propanol, 2-amino-2-methyl-1-propanol, 1-amino-2-propanol, 2-amino-1,3-propanediol, and diethanolamine.

[0044] The weight-average molecular weight of the polymer dispersant is preferably 3,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more, from the viewpoint of adsorption to carbon material-based conductive materials. Furthermore, from the viewpoint of solubility in organic solvents, dispersibility of carbon material-based conductive materials, and lower viscosity of carbon material-based conductive material slurries and electrode pastes for energy storage devices, it is preferably 100,000 or less, more preferably 70,000 or less, and even more preferably 50,000 or less. In this disclosure, the weight-average molecular weight of the polymer dispersant is a value measured by GPC (gel permeation chromatography), and the details of the measurement conditions are as shown in the [Measurement of Weight-Average Molecular Weight] section of the Examples.

[0045] From the viewpoint of productivity, the content of the leveling agent of the present disclosure in the dispersant composition of the present disclosure is preferably 0.1% or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, and from the viewpoint of solubility in the solvent, it is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

[0046] The content of the polymeric dispersant in the dispersant composition of the present disclosure is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of productivity, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of solubility in organic solvents at room temperature.

[0047] [Optional Components] The dispersant compositions of this disclosure may further contain other components, to the extent that the effects of this disclosure are not impaired. Examples of other components include antioxidants, neutralizing agents, defoaming agents, preservatives, dehydrating agents, rust inhibitors, plasticizers, binders, and the like.

[0048] The dispersant composition of this disclosure can be prepared, for example, by mixing a mixture of the leveling agent composition and a polymer dispersant using a stirrer. A stirrer suitable for preparing the leveling agent composition of this disclosure can be used. The polymer dispersant may be mixed with the leveling agent composition after being dissolved in an organic solvent. The preferred organic solvent used to dissolve the polymer dispersant is the same as the organic solvent suitable for preparing the leveling agent composition.

[0049] <Carbon Material-Based Conductive Material Slurry> In one embodiment, this disclosure relates to a carbon material-based conductive material slurry (hereinafter also referred to as "the conductive material slurry of this disclosure") containing the leveling agent composition of this disclosure, the polymer dispersant, and a carbon material-based conductive material. Therefore, the conductive material slurry of this disclosure comprises a leveling agent, a polymer dispersant, a carbon material-based conductive material, and an organic solvent. Preferred leveling agents and leveling agent compositions of this disclosure used in the preparation of the conductive material slurry of this disclosure are as described above. Preferred organic solvents contained in the conductive material slurry of this disclosure are the same as organic solvents suitable for the preparation of the leveling agent composition and the dispersant composition of this disclosure. The content of organic solvents in the conductive material slurry of this disclosure is the remainder after excluding the leveling agent, the polymer dispersant, the carbon material-based conductive material, and the optional components listed below. Because the conductive material slurry of this disclosure contains the leveling agent of this disclosure, the dispersibility of the carbon material-based conductive material is good and it has low viscosity.

[0050] [Carbon-based conductive materials] Examples of carbon-based conductive materials in one or more embodiments include carbon nanotubes (hereinafter sometimes referred to as "CNT"), acetylene black, carbon black, graphite, graphene, etc. Among these, at least one selected from acetylene black and CNT is preferred, and CNT is more preferred, from the viewpoint of achieving high conductivity. The carbon-based conductive material may be one type or a combination of two or more types.

[0051] In one or more embodiments, carbon nanotubes (CNTs) that can be used as carbon material-based conductive materials have a cylindrical shape formed by winding a single surface of graphite. Those wound in one layer are called single-walled carbon nanotubes (SWCNTs), those wound in two layers are called double-walled carbon nanotubes (DWCNTs), and those wound in three or more layers are called multi-walled carbon nanotubes (MWCNTs). Depending on the properties required for the electrode coating film formed using an electrode paste for energy storage devices containing CNTs, the conductive material slurry of this disclosure may contain single-walled, double-walled, or multi-walled CNTs or mixtures thereof. The electrode coating film is a film-like layer obtained by coating an electrode substrate (current collector) with an electrode paste for energy storage devices and drying it.

[0052] The average diameter of the CNTs is not particularly limited, but from the viewpoint of improving the dispersibility of the CNTs, it is preferably 1 nm or more, more preferably 2 nm or more, and from the viewpoint of improving conductivity, it is preferably 100 nm or less, more preferably 50 nm or less. In this disclosure, the average diameter of the CNTs can be measured by scanning electron microscope (SEM) or atomic force microscope (AFM).

[0053] The average length of the CNTs is not particularly limited, but from the viewpoint of improving conductivity, it is preferably 2 μm or more, more preferably 5 μm or more, and from the viewpoint of improving dispersibility, it is preferably 1000 μm or less, more preferably 800 μm or less. In this disclosure, the average length of the CNTs can be measured by scanning electron microscope (SEM) or atomic force microscope (AFM).

[0054] (Optional Components) The conductive slurry of this disclosure may further contain other components, to the extent that the effects of this disclosure are not impaired. Examples of other components include antioxidants, defoamers, preservatives, dehydrators, rust inhibitors, plasticizers, binders, and the like.

[0055] (Content of leveling agent in conductive material slurry) From the viewpoint of reducing the viscosity of the conductive material slurry, the content of the leveling agent of this disclosure in the conductive material slurry is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of carbon material-based conductive material, and from the viewpoint of controlling solubility in organic solvents, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of carbon material-based conductive material.

[0056] (Content of carbon material-based conductive material in conductive material slurry) The content of carbon material-based conductive material in the conductive material slurry of this disclosure is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of improving the convenience of adjusting the concentration of the electrode paste for the energy storage device of this disclosure, which will be described in detail later, for multilayer CNTs, and preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less, from the viewpoint of making the conductive material slurry easy to handle viscosity. Similarly, for single-walled CNTs, the content is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, from the viewpoint of improving the convenience of adjusting the concentration of the electrode paste for the energy storage device of this disclosure, and preferably 2% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of making the conductive material slurry easy to handle viscosity.

[0057] (Content of polymer dispersant in conductive material slurry) From the viewpoint of improving the dispersibility of carbon material-based conductive materials, the content of polymer dispersant in the conductive material slurry of this disclosure is preferably 3 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of carbon material-based conductive material, and from the viewpoint of maintaining a high energy density of the energy storage device, it is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less, per 100 parts by mass of carbon material-based conductive material.

[0058] (Method for producing conductive material slurry) In one or more embodiments, the conductive material slurry of the present disclosure can be prepared by mixing a mixture of the leveling agent composition of the present disclosure, a polymer dispersant, a carbon material-based conductive material, an organic solvent and optional components added as needed, in a mixing and dispersing machine. Alternatively, the conductive material slurry of the present disclosure can be prepared by mixing a mixture of a leveling agent, a polymer dispersant, a carbon material-based conductive material, an organic solvent and optional components added as needed, in a mixing and dispersing machine.

[0059] Examples of the mixing and dispersing equipment include at least one selected from ultrasonic homogenizers, vibration mills, jet mills, ball mills, bead mills, sand mills, roll mills, homogenizers, high-pressure homogenizers, ultrasonic devices, attritors, dissolvers, and paint shakers. Some components of the conductive material slurry may be mixed beforehand and then mixed with the remainder, or each component may be added in multiple portions rather than all at once. The polymer dispersant may be dissolved in an organic solvent before being mixed with other components such as carbon material-based conductive materials. The state of the carbon material-based conductive material before mixing with other components may be dry or dispersed in an organic solvent.

[0060] <Electrode Paste for Energy Storage Device>In one aspect, the present disclosure relates to an electrode paste for an energy storage device (hereinafter sometimes abbreviated as "the electrode paste of the present disclosure") including the leveling agent composition of the present disclosure, the polymer dispersant, the carbon material-based conductive material, the electrode active material, and the binder. Therefore, the electrode paste of the present disclosure includes the leveling agent of the present disclosure, the polymer dispersant, the carbon material-based conductive material, the electrode active material, the binder, and an organic solvent. The preferred leveling agent composition of the present disclosure, the leveling agent of the present disclosure, the polymer dispersant, and the carbon material-based conductive material used for the preparation of the electrode paste of the present disclosure are as described above. The preferred organic solvent contained in the electrode paste of the present disclosure is the same as the organic solvent suitable for the preparation of the leveling agent composition of the present disclosure, the dispersant composition of the present disclosure, and the conductive material slurry of the present disclosure. The content of the organic solvent in the electrode paste of the present disclosure is the remainder excluding the above leveling agent, polymer dispersant, carbon material-based conductive material, electrode active material, binder, and the following optional components. Since the electrode paste of the present disclosure contains the leveling agent of the present disclosure, it has good dispersibility of the carbon material-based conductive material, low viscosity, and can form an electrode coating film with good smoothness.

[0061] [Electrode Active Material] The electrode active material is, for example, a positive electrode active material. There is no particular limitation on the positive electrode active material, and for example, a compound having an olivine structure, a lithium transition metal composite oxide, or the like can be used. Examples of the compound having an olivine structure include compounds represented by the general formula Li x M1 s PO4 (where M1 is a 3d transition metal, 0 ≦ x ≦ 2, 0.8 ≦ s ≦ 1.2). The compound having an olivine structure may be coated with amorphous carbon or the like. Examples of the lithium transition metal composite oxide include lithium manganese oxide having a spinel structure and a general formula Li x M2O 2-Examples include lithium transition metal composite oxides represented by δ (where M2 is a transition metal, 0.4 ≤ x ≤ 1.2, 0 ≤ δ ≤ 0.5). The transition metal M2 may include Co, Ni, or Mn. The lithium transition metal composite oxide may further contain one or more elements selected from Al, Fe, Cr, Ti, Zn, P, and B. From the viewpoint of stability in aqueous systems, lithium transition metal composite oxides such as lithium iron phosphate and lithium manganese iron phosphate are preferred.

[0062] [Binder] The binder (binding agent) is not particularly limited, but polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylonitrile, etc. can be used alone or in combination.

[0063] [Optional Components] The electrode paste of this disclosure may further contain other components (optional components) to the extent that the effects of this disclosure are not impeded. Examples of other components include antioxidants, defoamers, preservatives, dehydrating agents, rust inhibitors, plasticizers, and dispersants other than the polymer dispersants described above.

[0064] (Content of leveling agent in electrode paste) From the viewpoint of improving the smoothness of the electrode coating, the content of the leveling agent in the electrode paste of this disclosure is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of carbon material-based conductive material, and from the viewpoint of suppressing the increase in resistance of the electrode coating, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0065] (Content of carbon material-based conductive material in electrode paste) The content of carbon material-based conductive material in the electrode paste of this disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of conductivity of the electrode coating film, and preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of maintaining a high energy density of the energy storage device.

[0066] (Content of polymer dispersant in electrode paste) From the viewpoint of suppressing the increase in resistance of the electrode coating film, the content of polymer dispersant in the electrode paste of this disclosure is preferably 3 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of carbon material-based conductive material, and from the viewpoint of high conductivity, preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less.

[0067] (Content of electrode active material in electrode paste) The content of electrode active material in the electrode paste of this disclosure is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of energy density and stability, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, from the viewpoint of coating properties on current collectors.

[0068] (Binder content in electrode paste) The binder content in the total solids of the electrode paste of this disclosure is preferably 0.05% by mass or more from the viewpoint of coating properties of the composite layer and adhesion to the current collector, and preferably 10.0% by mass or less from the viewpoint of maintaining a high energy density of the energy storage device.

[0069] The solid content concentration of the electrode paste of this disclosure, and the content of the leveling agent, polymer dispersant, electrode active material, binder, carbon material-based conductive material, organic solvent, and the optional components in the electrode paste of this disclosure, can each be adjusted according to the viscosity suitable for applying the electrode paste to a current collector. From the viewpoint of drying properties, a small amount of organic solvent is preferable, but from the viewpoint of surface smoothness of the electrode coating film, it is preferable that the viscosity of the electrode paste is not too high. On the other hand, from the viewpoint of suppressing drying and obtaining a sufficient film thickness of the composite layer, it is preferable that the viscosity of the electrode paste is not too low.

[0070] (Method for Manufacturing Electrode Paste) In one or more embodiments, the electrode paste of this disclosure can be prepared by mixing and stirring the dispersant composition of this disclosure, electrode active material, carbon material-based conductive material, binder, organic solvent (additional solvent) for adjusting the solid content concentration, etc., and optionally the above-mentioned optional components. Some of the components used in the preparation of the electrode paste of this disclosure may be premixed and then mixed with the remainder. For example, a conductive material slurry of this disclosure may be prepared and then the electrode active material may be mixed into the conductive material slurry. Alternatively, the conductive material slurry and the electrode active material may be thoroughly stirred and mixed, and then the binder may be added. The state of the carbon material-based conductive material before mixing with other components may be dry or dispersed in an organic solvent. In addition, each component may be added in multiple portions rather than all at once. This reduces the mechanical load on the stirring device. A planetary mixer, bead mill, jet mill, etc. can be used for mixing and stirring, and these may also be used in combination.

[0071] <Method for Manufacturing an Electrode> In one embodiment, this disclosure relates to a method for manufacturing an electrode using the electrode paste of this disclosure. The method for manufacturing an electrode in this embodiment includes coating the electrode paste of this disclosure onto a current collector, drying it, and obtaining an electrode coating. After drying the coating obtained by coating with the electrode paste, it may be pressed as necessary. In this embodiment, a preferred electrode paste of this disclosure is as described above. In the method for manufacturing an electrode of this disclosure, an electrode can be manufactured by conventionally known methods, except for the use of the electrode paste of this disclosure.

[0072] The positive electrode is manufactured, for example, by coating a positive electrode paste (electrode paste containing positive electrode active material) onto a current collector such as aluminum foil and drying it. To increase the density of the positive electrode coating, compaction can be performed using a press. A die head, Conn Reverse Roll, Direct Roll, Gravure Roll, etc., can be used to coat the positive electrode paste. Drying after coating can be performed by heating, airflow, infrared irradiation, etc., individually or in combination. Drying after coating is performed at a temperature at which the organic solvent in the positive electrode paste can no longer be present in the positive electrode paste after a drying time. The drying temperature is not particularly limited as long as it is below the thermal decomposition temperature of the binder resin in the environment in which drying is performed (under atmospheric pressure or vacuum), but it is preferably above the boiling point of the organic solvent. The drying temperature is preferably 60°C to 220°C, and the drying time is preferably 10 minutes to 24 hours. The positive electrode can be pressed using a roll press or the like. Alternatively, after pressing, the positive electrode may be processed to a size suitable for integration into an energy storage device, and then re-dried under the conditions described above.

[0073] <Method for Leveling an Electrode Coating> In one embodiment, this disclosure relates to a method for leveling an electrode coating. The method for leveling an electrode coating according to this disclosure includes coating an electrode paste according to this disclosure, which contains a leveling agent according to this disclosure, onto a current collector. The method for leveling an electrode coating according to this disclosure further includes drying the electrode paste according to this disclosure that has been coated onto the current collector. The method for leveling an electrode coating according to this disclosure also includes pressing the dried electrode paste as necessary. The electrode paste that has been dried on the current collector and pressed as necessary becomes an electrode coating. In this embodiment, a preferred electrode paste according to this disclosure is as described above. In the method for leveling an electrode coating according to this disclosure, the method for coating the electrode paste according to this disclosure onto the current collector, the means for drying after coating, the drying temperature, the drying time, and the pressing method are the same as those of the electrode manufacturing method described above.

[0074] In the leveling method of the electrode coating film of the present disclosure, since the leveling agent of the present disclosure is contained in the electrode paste of the present disclosure, the viscosity of the electrode paste of the present disclosure is low, and the organic solvent is likely to volatilize during and after the coating of the electrode paste of the present disclosure on the current collector. Therefore, the smoothness of the electrode coating film obtained by drying the coating film is improved.

[0075] <Method for manufacturing a power storage device> In one aspect, the present disclosure relates to a method for manufacturing a power storage device. The method for manufacturing a power storage device according to this aspect includes incorporating an electrode obtained by the method for manufacturing an electrode of the present disclosure. As the power storage device, in one or more embodiments, a lithium-ion secondary battery, a lithium-air secondary battery, a sodium-ion battery, a sodium-sulfur secondary battery, a sodium-nickel chloride secondary battery, an organic radical battery, a zinc-air secondary battery, an all-solid-state battery, etc. can be mentioned.

[0076] The method for manufacturing a power storage device of the present disclosure includes the same steps as the known method for manufacturing a power storage device, except for using the electrode obtained by the method for manufacturing an electrode of the present disclosure as the electrode of the power storage device. In the method for manufacturing a power storage device of the present disclosure, for example, a step of overlapping two electrodes (a positive electrode and a negative electrode) via a separator and winding or laminating them into a battery shape, and a step of putting the obtained wound body or laminate into a battery container or a laminate container and injecting an electrolytic solution into the container and sealing it are included.

[0077] This application further discloses the following inventions.

[0078] <1> A method for leveling an electrode coating film, including coating an electrode paste for a power storage device containing a leveling agent for a power storage device containing a compound represented by the following general formula (1) on a current collector. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 represents an alkyl group or an alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are each the average number of added moles and are numbers from 0 to 8, and the sum of n and m is 8 or less, R 2R represents a hydrogen atom or a methyl group. <2> In the above general formula (1), R 1 The method for leveling an electrode coating film according to <1>, wherein the number of carbon atoms is 14 or less, preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. <3> The method for leveling an electrode coating film according to <1> or <2>, wherein in the above general formula (1), the sum of n and m is 8 or less, preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, even more preferably 3 or less, and preferably 1 or more, and even more preferably 2 or more. <4> In the above general formula (1), R 2 The method for leveling an electrode coating film according to any one of the items <1> to <3> above, wherein is a methyl group or a hydrogen atom, preferably a hydrogen atom. <5> A leveling agent composition for energy storage devices containing a compound represented by the following general formula (1) and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2represents a hydrogen atom or a methyl group. <6> The leveling agent composition for energy storage devices according to <5>, wherein the organic solvent is at least one selected from the group consisting of dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethyl acetate, γ-butyrolactone, and ε-caprolactone. <7> The leveling agent composition for energy storage devices according to <5> or <6>, wherein the content of the leveling agent is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. <8> A dispersant composition for energy storage devices containing a leveling agent for energy storage devices containing a compound represented by the following general formula (1), a polymer dispersant, and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2<9> The polymer dispersant composition for energy storage devices according to <8>, wherein the polymer dispersant is obtained by neutralizing, as necessary, polyvinyl acetal, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral, methylcellulose, styrene butadiene, acrylonitrile butadiene or a partially hydrogenated thereof, an acrylic copolymer, or an amide-modified copolymer of an olefin and maleic anhydride. <10> The content of the leveling agent is preferably 0.1% or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. The dispersant composition for energy storage devices according to <8> or <9>. <11> The dispersant composition for energy storage devices according to any one of <8> to <10>, wherein the content of the polymer dispersant is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. <12> The dispersant composition for energy storage devices according to any one of <8> to <11>, wherein the polymer dispersant is a vinyl polymer. <13> A carbon material-based conductive material slurry containing a leveling agent for energy storage devices containing a compound represented by the following general formula (1), a carbon material-based conductive material, a polymer dispersant, and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2<14> The carbon material-based conductive material slurry according to <13>, wherein the carbon material-based conductive material is one or more selected from carbon nanotubes, acetylene black, carbon black, graphite, and graphene. <15> The carbon material-based conductive material slurry according to <14>, wherein the average diameter of the carbon nanotubes is preferably 1 nm or more, more preferably 2 nm or more, and preferably 100 nm or less, and more preferably 50 nm or less. <16> The carbon material-based conductive material slurry according to any one of <13> to <15>, wherein the average length of the carbon nanotubes is preferably 2 μm or more, more preferably 5 μm or more, and preferably 1000 μm or less, and more preferably 800 μm or less. <17> The carbon material-based conductive material slurry according to any one of <13> to <16>, wherein the content of the leveling agent in the carbon material-based conductive material slurry is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, with respect to 100 parts by mass of the carbon material-based conductive material. <18> The carbon material-based conductive material slurry according to any one of <13> to <17>, wherein the content of the carbon material-based conductive material in the carbon material-based conductive material slurry is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less, with respect to 10% by mass or less, and even more preferably 8% by mass or less, with respect to 13> to <17>. <19> The carbon material-based conductive material slurry according to any one of <14> to <16>, wherein the amount of multilayer carbon nanotubes in the carbon material-based conductive material slurry is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less. <20> The carbon material-based conductive material slurry according to any one of <14> to <16>, wherein the amount of single-walled carbon nanotubes in the carbon material-based conductive material slurry is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and preferably 2% by mass or less, more preferably 1% by mass or less.<21> The carbon material-based conductive material slurry according to any one of <13> to <20>, wherein the content of the polymer dispersant in the carbon material-based conductive material slurry is preferably 3 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less, with respect to 100 parts by mass of the carbon material-based conductive material. <22> The electrode paste for an energy storage device comprising a leveling agent for an energy storage device containing a compound represented by the following general formula (1), a carbon material-based conductive material, a binder, a positive electrode active material, a polymer dispersant, and an organic solvent. R. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2represents a hydrogen atom or a methyl group. <23> The electrode paste for energy storage devices according to <22>, wherein the positive electrode active material is one or more selected from compounds having an olivine structure and lithium transition metal composite oxides. <24> The electrode paste for energy storage devices according to <22> or <23>, wherein the binder is one or more selected from polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, and polyacrylonitrile. <25> The electrode paste for energy storage devices according to any one of <22> to <24>, wherein the content of the leveling agent in the electrode paste for energy storage devices is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of carbon material-based conductive material. <26> The electrode paste for energy storage devices according to any one of <22> to <25>, wherein the content of the carbon material-based conductive material in the electrode paste for energy storage devices is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. <27> The electrode paste for energy storage devices according to any one of <22> to <26>, wherein the content of the polymer dispersant in the electrode paste for energy storage devices is preferably 3 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less, per 100 parts by mass of the carbon material-based conductive material. <28> The electrode paste for energy storage devices according to any one of <22> to <27>, wherein the content of the electrode active material in the electrode paste for energy storage devices is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.<29> A method for manufacturing an electrode for an energy storage device, comprising preparing an electrode coating film using an electrode paste for an energy storage device described in any of <22> to <28> above. <30> A method for manufacturing an energy storage device, comprising incorporating an electrode for an energy storage device obtained by the manufacturing method described in <29> above. <31> Use of a compound represented by the following general formula (1) as a leveling agent for an energy storage device. R. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group. <32> Use of a leveling agent for energy storage devices containing a compound represented by the following general formula (1) for the manufacture of electrode paste for energy storage devices. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

[0079] Examples and comparative examples of the present disclosure are shown below, but the present disclosure is not limited thereto.

[0080] 1. Measurement Method for Each Parameter [Solubility of Leveling Agent in Organic Solubility] The solubility of the leveling agents in manufacturing examples 1 to 7 shown in Table 1 below in organic solvents (NMP) was confirmed under the following conditions. The leveling agent was added to the organic solvent (NMP) in a vial to a concentration of 10% by mass, and the mixture was stirred at 200 rpm at room temperature for 2 hours to prepare the leveling agent composition. The solubility of the leveling agent in organic solvents (NMP) at 25°C was evaluated by visual inspection of the appearance of the obtained leveling agent composition according to the following criteria, and the results are shown in Table 2. A: The leveling agent composition is uniformly transparent, and the solubility of the leveling agent is good. B: The leveling agent composition is cloudy overall, and the solubility of the leveling agent is poor.

[0081] [Measurement of Electrode Paste Viscosity] The viscosity of the electrode (positive electrode) paste (at 25°C) was measured as follows: An Anton Paar MCR302 rheometer was fitted with a CP50 cone plate, and the shear rate was set to 0.1 s. -1 From 1000s -1 After raising it up to (outbound), 1000s -1 from 0.1s -1 Return to the starting point (return trip), and the shear rate on the return trip is 1s -1 The shear viscosity was measured as the viscosity of the electrode paste. The results are shown in Table 3.

[0082] [Smoothness of Electrode Coatings] The smoothness of electrode coatings prepared using the electrode pastes of Examples 1-5 and Comparative Examples 1-5 was evaluated under the following conditions. The electrode paste was dripped onto a polyester film and coated using an applicator to a thickness of 200 μm. The polyester film coated with this electrode paste was dried at 80°C for 1 hour to obtain an electrode coating with a thickness of 150 μm. The appearance of the obtained electrode coatings was visually inspected, and the smoothness of the electrode coatings was evaluated according to the following criteria, and the results are shown in Table 3. A: The electrode coating is free of defects and has good smoothness. B: The electrode coating has a few defects, but the smoothness is relatively good. C: The electrode coating has many defects, and the overall smoothness is poor. Defects refer to unevenness caused by indentations of 100 μm or more.

[0083] [Measurement of Weight-Average Molecular Weight of Polymer Dispersants] The weight-average molecular weight of polymer dispersants was measured by the GPC method. The detailed conditions were as follows: Measurement device: HLC-8320GPC (Tosoh Corporation) Column: α-M + α-M (Tosoh Corporation) Column temperature: 40°C Detector: Differential refractive index Eluent: N,N-dimethylformamide (DMF) solution of 60 mmol / L H3PO4 and 50 mmol / L LiBr Flow rate: 1 mL / min Standard sample used for calibration curve: Polystyrene Sample solution: DMF solution containing 0.5 wt% solid content of copolymer Injection volume of sample solution: 100 μL

[0084] 2. Leveling Agents Leveling agents specified by the above general formula (1) and Table 1 were prepared.

[0085] 3. Preparation of Leveling Agent Compositions Leveling agents 1 to 7 were each dissolved in NMP to obtain the leveling agent compositions of Production Examples 1 to 7. The concentration of the leveling agent in each leveling agent composition was 10% by mass.

[0086] 4. Polymer Dispersant For the preparation of the dispersant composition and electrode paste, the following polymer dispersants were prepared. [Polymer Dispersant A] R in the above general formulas (2) and (3) 3 CH3, R 4 i-C5H 11 , R 5 C 18 H 37 , R 6 C4H9, R 7 A polymeric dispersant with C4H9, M being H, b+c = 1.00, and b / b+c = 0.70 (average polymerization molecular weight Mw = 23300) [Polymeric dispersant B] Polyvinyl acetal Esrec BL-1H (manufactured by Sekisui Chemical Co., Ltd., degree of acetalization: approximately 69 mol%, molecular weight (catalog value) 2.0 × 10 4 )

[0087] 5. Preparation of Cathode Paste (Electrode Paste) [Example 1] A dispersant composition was obtained by mixing 1.6 g of the leveling agent composition from Production Example 1 (10% by mass NMP solution) with 4 g of polymer dispersant A (30% by mass NMP solution). Next, 5.6 g of the dispersant composition was mixed with 4 g of MWCNT (FT6810, manufactured by Canano) and 0.4 g of NMP to obtain a crude dispersion. The obtained crude dispersion was dispersed in a paint shaker for 12 hours using zirconia beads as a medium to obtain a conductive material slurry. Next, 0.95 g of the conductive material slurry, 1.714 g of NMP, and 2.375 g of PVDF (8% by mass) NMP solution (KF Polymer L#7208, manufactured by Kureha Corporation) were weighed into a 50 ml sample bottle and mixed uniformly with a spatula. Subsequently, 14.96 g of NCM523 (lithium nickel manganese cobaltate 5E12D, manufactured by Beijing Dangsheng) was added as the positive electrode active material, and the mixture was stirred again with a spatula until homogeneous. The mixture was then stirred for 2 minutes using a rotation-orbit mixer (AR-100, manufactured by Thinky Co., Ltd.) to obtain the positive electrode paste of Example 1. The mass ratio of the positive electrode active material, binder (PVDF), carbon material-based conductive material (carbon nanotube), polymer dispersant A, and leveling agent was 98.415:1.25:0.25:0.075:0.01 (in terms of solid content), and the solid content (mass%) of the positive electrode paste was 76% by mass. The total solid content of the positive electrode paste is the total mass of the positive electrode active material, binder, carbon material-based conductive material, polymer dispersant, and leveling agent contained in the positive electrode paste.

[0088] [Examples 2-5, Comparative Examples 2-4] The cathode pastes of Examples 2-5 and Comparative Examples 2-4 were prepared in the same manner as the cathode paste of Example 1, except that the polymer dispersant and leveling agent described in Table 3 were used.

[0089] [Comparative Example 1, Comparative Example 5] The cathode pastes of Comparative Example 1 and Comparative Example 5 were prepared in the same manner as the cathode paste of Example 1, except that they used the polymer dispersant described in Table 3 and did not contain a leveling agent.

[0090]

[0091] The viscosity of the positive electrode pastes in the examples containing leveling agents 1 to 4 was lower than that of the positive electrode pastes in Comparative Examples 1, 3, and 5. Furthermore, the smoothness of the electrode coating film formed using the positive electrode pastes in the examples was superior to that formed using the positive electrode pastes in the comparative examples. In the case of the positive electrode pastes in Comparative Examples 2 and 4, the solubility of the leveling agent in NMP was poor, making it impossible to produce positive electrode pastes and electrode coating films.

[0092] The leveling agent composition of this disclosure enables the reduction of viscosity of electrode paste for energy storage devices used to form electrode coatings, thereby improving the smoothness of the electrode coatings. Using the leveling agent composition of this disclosure contributes to improving the yield of electrode coatings and, consequently, to improving the productivity of energy storage devices.

Claims

1. A method for leveling an electrode coating, comprising applying an electrode paste for an energy storage device containing a compound represented by the following general formula (1) to a current collector. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

2. A leveling agent composition for a power storage device, comprising a leveling agent for a power storage device containing a compound represented by the following general formula (1) and an organic solvent. R 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 represents an alkyl group or an alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are each the average number of added moles, and are numbers from 0 to 8, and the sum of n and m is 8 or less, and R 2 represents a hydrogen atom or a methyl group.

3. The leveling agent composition for energy storage devices according to claim 2, wherein the content of the leveling agent is 1% by mass or more and 30% by mass or less.

4. A dispersant composition for energy storage devices, comprising a leveling agent for energy storage devices containing a compound represented by the following general formula (1), a polymer dispersant, and an organic solvent. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

5. The dispersant composition for energy storage devices according to claim 4, wherein the content of the leveling agent is 0.1% by mass or more and 10% by mass or less.

6. The dispersant composition for energy storage devices according to claim 4 or 5, wherein the content of the polymer dispersant is 10% by mass or more and 50% by mass or less.

7. The dispersant composition for energy storage devices according to any one of claims 4 to 6, wherein the polymer dispersant is a vinyl polymer.

8. A carbon material-based conductive material slurry containing a leveling agent for energy storage devices containing a compound represented by the following general formula (1), a carbon material-based conductive material, a polymer dispersant, and an organic solvent. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

9. The carbon material-based conductive material slurry according to claim 8, wherein the carbon material-based conductive material is one or more selected from acetylene black and carbon nanotubes.

10. An electrode paste for an energy storage device comprising a leveling agent for an energy storage device containing a compound represented by the following general formula (1), a carbon material-based conductive material, a binder, a positive electrode active material, a polymer dispersant, and an organic solvent. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

11. A method for manufacturing an electrode for an energy storage device, comprising preparing an electrode coating film using the electrode paste for energy storage devices described in claim 10.

12. A method for manufacturing an energy storage device, comprising incorporating electrodes for an energy storage device obtained by the manufacturing method described in claim 11.

13. Use of compounds represented by the following general formula (1) as leveling agents for energy storage devices. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

14. Use of a leveling agent for energy storage devices containing a compound represented by the following general formula (1) for the manufacture of electrode paste for energy storage devices. 1 -O-(EO) n (PO) m -R 2 (1) In the above general formula (1), R 1 R represents an alkyl or alkenyl group having 6 to 14 carbon atoms, EO represents an ethyleneoxy group, PO represents a propyleneoxy group, n and m are the average number of moles added, which are between 0 and 8, and the sum of n and m is 8 or less. 2 represents a hydrogen atom or a methyl group.

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