Electrode manufacturing method and liquid composition set

Abstract

To provide an electrode manufacturing method that can form a uniform insulating layer on a surface of an electrode substrate.SOLUTION: An electrode manufacturing method includes: a first liquid composition application step of applying a first liquid composition to a surface of an electrode substrate having an opening on the surface before a second liquid composition containing particles so as to allow deposition of the second liquid composition on the surface; a first liquid composition solidification step of solidifying the first liquid composition applied to the surface; and a second liquid composition deposition step of applying the second liquid composition to the surface to be in contact with the solidified first liquid composition to deposit the second liquid composition on the surface.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing electrodes and a liquid composition set. [Background technology]

[0002] Conventionally, in electrochemical elements such as lithium-ion secondary batteries, electric double-layer capacitors, lithium-ion capacitors, and redox capacitors, it has been proposed to form an insulating layer on the electrode substrate for the purpose of preventing short circuits between the positive and negative electrodes (see, for example, Patent Document 1). [Overview of the project] [Problems that the invention aims to solve]

[0003] However, because the electrode substrates of electrochemical elements have a wide range of specifications, including materials and volume density, depending on their purpose, it is extremely difficult to uniformly form an insulating layer containing insulating particles on the electrode substrate.

[0004] The present invention aims to provide a method for manufacturing electrodes that can form a uniform insulating layer on the surface of an electrode substrate. [Means for solving the problem]

[0005] The present invention, as a means for solving the aforementioned problems, is an electrode manufacturing method comprising: a first liquid composition application step of applying a first liquid composition to the surface of an electrode substrate having an opening on its surface, before the second liquid composition, such that a second liquid composition containing particles can be deposited on the surface; a first liquid composition solidification step of solidifying the first liquid composition applied to the surface; and a second liquid composition deposition step of applying the second liquid composition to the surface in contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. The process includes a heating step of heating an electrode substrate on which the second liquid composition is deposited, wherein the first liquid composition is a liquid compound that is volatile in the heating step. . [Effects of the Invention]

[0006] According to the present invention, a method for manufacturing an electrode capable of forming a uniform insulating layer on the surface of an electrode substrate can be provided.

Brief Description of the Drawings

[0007] [Figure 1] FIG. 1 is a schematic view showing an example of a coating apparatus having a cooling unit. [Figure 2] FIG. 2 is a schematic view showing another example of a coating apparatus having a cooling unit. [Figure 3] FIG. 3 is a schematic view showing an example of details of the coating unit and the cooling unit of the coating apparatus of FIG. 1. [Figure 4] FIG. 4 is a schematic view showing an example of details of the coating unit and the cooling unit of the coating apparatus of FIG. 2. [Figure 5] FIG. 5 is a schematic view showing another example of details of the coating unit and the cooling unit of the coating apparatus of FIG. 1. [Figure 6] FIG. 6 is a schematic view showing another example of details of the coating unit and the cooling unit of the coating apparatus of FIG. 2. [Figure 7] FIG. 7 is a schematic view showing an example of a coating apparatus having a cooling unit.

Embodiments for Carrying Out the Invention

[0008] (Liquid Composition Set) The liquid composition set of the present invention includes a first liquid composition containing a liquid compound and a second liquid composition containing particles and a dispersion medium. The liquid composition set satisfies any one of the following (1) and (2). (1) The cohesive energy density A1 (J / mol), which is the value obtained by multiplying the molecular volume of the liquid compound in the first liquid composition by the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH), is greater than the cohesive energy density A2 (J / mol), which is the value obtained by multiplying the molecular volume of the dispersion medium in the second liquid composition by the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH). (2) The absolute value of the difference (A1-A2) between the cohesive energy density A1 and the cohesive energy density A2 is 5,000 J / mol or less. The liquid composition set of the present invention, by satisfying either of the above conditions (1) and (2), can form an insulating layer more uniformly on the electrode substrate.

[0009] Here, the cohesive energy density is Mvol × tot HSP 2 Molecular volume: Mvol and tot HSP 2 This is the material property value obtained by multiplying by [a certain factor]. tot HSP 2 It is calculated using the following formula. tot HSP 2 =δD 2 +δP 2 +δH 2 However, δD, δP, and δH are Hansen solubility parameters. Hansen's solubility parameter is a representation of the solubility parameter introduced by Hildebrand, divided into three components: a dispersion term δD, a polarity term δP, and a hydrogen bonding term δH, and expressed in three-dimensional space. The dispersion term δD represents the effect due to dispersion forces, the polarity term δP represents the effect due to inter-dipole forces, and the hydrogen bonding term δH represents the effect due to hydrogen bonding forces.

[0010] In this invention, the Hansen solubility parameters used were those described in Charles M. Hansen, "Hansen Solubility Parameters: A Users Handbook" (CRC Press, 2007). Values ​​not described in the above-mentioned literature were either those described in Japanese Patent Publication No. 6787147, or those calculated using the group contribution method for estimating Hansen solubility parameters by Stefanis and Panayiotou (Stefanis, E.; Panayiotou, C. Int. J. Thermophys., 29, 568-585.(2008)).

[0011] The cohesive energy density A1 of the liquid compound in the first liquid composition is preferably 30,000 J / mol or more, and more preferably 50,000 J / mol or more. When the cohesive energy density A1 is 30,000 J / mol or more, an insulating layer can be formed more uniformly on the electrode substrate.

[0012] <First liquid composition> The first liquid composition mainly consists of a volatile liquid compound (solvent). In this specification, the first liquid composition is described as "mainly composed of a volatile liquid compound" to the extent that the residue remaining after drying the first liquid composition does not adversely affect, for example, the electrode composite layer, but preferably contains 20% by mass or more of a volatile liquid compound under normal pressure, more preferably 50% by mass or more, and particularly preferably 100% by mass of the first liquid composition is a volatile liquid compound.

[0013] Furthermore, the compound may be a liquid compound that can volatilize under reduced pressure by vacuum drying in a vacuum oven or the like. In this case, the degree of vacuum is preferably -0.05 MPa or less from atmospheric pressure, and more preferably -0.1 MPa or less, as measured by a differential pressure gauge. Vacuum drying is a common process in the manufacturing process of electrochemical elements such as lithium-ion secondary batteries. The temperature at which the volatile liquid compound contained in the first liquid composition volatilizes, i.e., the boiling point, is preferably 80°C or higher, and more preferably 150°C or higher, from the viewpoint of drying properties.

[0014] In this specification, room temperature means 25°C. The volatile liquid compound (solvent) contained in the first liquid composition solidifies into a solid when cooled. The temperature at which the volatile liquid compound becomes solid, i.e., the melting point Mp (hereinafter treated as synonymous with "freezing point"), is preferably below room temperature, in that it allows the volatile liquid compound to be solidified with a simple configuration. It is more preferably -196°C or higher, as it is a cooling temperature that can be used in a typical production plant, and even more preferably 0°C or higher, as it allows the volatile liquid compound to be solidified with a simple configuration.

[0015] The volatile liquid compound contained in the first liquid composition may be one liquid compound (a single solvent) or two or more liquid compounds (a mixed solvent). The elemental solvent can be any solvent that is liquid at room temperature and becomes solid when cooled below room temperature, and from the viewpoint of cooling temperature, it is preferable that it is a solvent that solidifies between 0°C and room temperature. Examples of the elemental solvents include cyclohexane, t-butyl alcohol, dimethyl carbonate, water, pyrimidine, p-xylene, 1-methylcyclohexanol, cyclohexylbenzene, cyclohexanol, cyclooctanone, vinylene carbonate, ethylene carbonate, ethanolamine, dimethyl sulfoxide (DMSO), dimethyl succinate, acetophenone, 1,2-dimethoxybenzene (veratrol), 1,4-butanediol, bicyclohexyl, 2-pyrrolidone, 1H-1,2,3-triazole, 1,3-dimethyl-2-imidazolidinone (DMI), ethanolamine, anethole, glycerol, 4-acetylmorpholine, 2-phenoxyethanol, 2-acetylthiophene, ethyl cinnamate, tetradecane, 1,8-cineole (eucalyptol), and dimethyl phthalate. These may be used individually or in combination of two or more.

[0016] Examples of the mixed solvent include a mixed solvent of the elemental solvents, or a mixed solvent of the elemental solvent and a liquid compound with a melting point higher than room temperature. Furthermore, there may be multiple elemental solvents and liquid compounds with melting points higher than room temperature, as long as they are liquid at room temperature and become solid when cooled below room temperature. Among these, those that become solid between 0°C and room temperature are more preferable from the viewpoint of cooling temperature. Examples of liquid compounds with melting points higher than room temperature include neopentyl alcohol, cyclooctanone, ethylene carbonate, dimethyl carbonate, 1,6-hexanediol, cyclododecane, 2,6-dimethoxyphenol, 1,9-nonanediol, 4'-methoxyacetophenone, 4'-ethoxyacetophenone, methyl 4-methylbenzoate, 1,2-cyclohexanedione, guaiacol, and dibutyl sulfoxide. These may be used individually or in combination of two or more.

[0017] The mixing ratio of the elemental solvent and the liquid compound with a melting point higher than room temperature in the mixed solvent is not particularly limited and can be appropriately selected depending on the purpose. However, in order to enable a higher cooling temperature when solidifying the first liquid composition on the electrode substrate and to allow it to be easily liquefied at room temperature, the mass ratio of the liquid compound in the mixed solvent is preferably 70% by mass or more of the ratio that results in a saturated solution, more preferably 80% by mass or more, and even more preferably the ratio that results in a saturated solution.

[0018] The first liquid composition is not particularly limited and can be produced using known dispersion devices. Examples of such dispersion devices include stirrers, ball mills, bead mills, ring mills, high-pressure dispersers, rotary high-speed shearers, and ultrasonic dispersers.

[0019] The melting point of the first liquid composition is preferably 0°C to 25°C, in that it allows for the solidification of volatile liquid compounds with a simple structure. The viscosity of the first liquid composition at 25°C is preferably 50 mPa·s or less, and more preferably 30 mPa·s or less. When the viscosity of the first liquid composition at 25°C is 50 mPa·s or less, the first liquid composition can be sufficiently impregnated into the electrode substrate when it is applied to the electrode substrate. Furthermore, when the first liquid composition is ejected by an inkjet method, from the viewpoint of ejection performance, the viscosity of the first liquid composition at 25°C is preferably 50 mPa·s or less, and more preferably 30 mPa·s or less. There are no particular restrictions on the method for measuring the viscosity of the first liquid composition, and it can be appropriately selected depending on the purpose. For example, it can be measured in accordance with JIS Z 8803. There are no particular restrictions on the apparatus used for the measurement, and it can be appropriately selected depending on the purpose. For example, a TV25 type viscometer (cone plate type viscometer, manufactured by Toki Sangyo Co., Ltd.) can be used.

[0020] <Second liquid composition> The second liquid composition contains particles and a dispersion medium, preferably a dispersant and a resin, and may further contain other components as needed.

[0021] -particle- The particles refer to colorants (pigments) with low solubility in the solvent. Here, the solubility of the particles in the solvent is typically less than 0.1% by mass. Examples of materials constituting the particles include inorganic oxides such as carbon, calcium carbonate, calcium phosphate, aluminum oxide, silica, titanium oxide, silicon oxide, and zirconium oxide; inorganic nitrides containing metals similar to metal oxides; metal sulfides; organic materials such as azo compounds, phthalocyanines, and quinacridone; resin materials such as polystyrene, melamine resin, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polypropylene, and polyethylene; or organic-inorganic composite materials combining the above materials. These may be used individually or in combination of two or more. Among these, inorganic oxides such as alumina and silica are preferred due to their high insulating and heat-resistant properties, with alumina being particularly preferred.

[0022] There is no particular limitation on the type of the alumina, and it can be appropriately selected according to the purpose. For example, α-alumina, γ-alumina, β-alumina, fused alumina, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, α-alumina is preferable from the viewpoints of insulation and abrasion resistance. When using two or more kinds of alumina, it is preferable that the main component of the alumina is α-alumina. Here, the main component being α-alumina means that the content rate of α-alumina in the total alumina is 50% by mass or more, and the content rate of α-alumina in the total alumina is preferably 60% by mass or more, and more preferably 70% by mass or more.

[0023] The median diameter (D 50 ) of the particles is preferably 50 nm or more and 1,000 nm or less, more preferably 50 nm or more and 800 nm or less, and still more preferably 100 nm or more and 600 nm or less from the viewpoint of dispersibility as a liquid composition. The measurement of the median diameter (D 50 ) of the particles includes, for example, a dynamic light scattering device (DLS), specifically, a thick system particle size analyzer (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.), etc. Examples of the shape of the particles include rectangular, spherical, elliptical, cylindrical, oval, dog bone shape, amorphous, etc. Note that the particles may be fibrous.

[0024] The content of the particles is preferably 20% by mass or more and 55% by mass or less, more preferably 25% by mass or more and 52% by mass or less, and still more preferably 35% by mass or more and 50% by mass or less with respect to the total amount of the second liquid composition. The content of the particles shows a high solid content concentration as compared with a liquid composition such as an ink suitable for coating on paper. By setting the content of the particles within such a range, unevenness in the coating film thickness after drying can be suppressed.

[0025] -Dispersion medium- Examples of dispersion media include dimethyl sulfoxide (DMSO), 1-methyl-2-pyrrolidone (NMP), ethyl lactate (EL), 2-butanone (MEK), butyl acetate, 2-heptanone, ethyl hexanoate, isopropyl alcohol (IPA), ethanol, n-butanol, ethyl acetate, butyl acetate, ethylene glycol (EG), propylene glycol (PG), hexylene glycol (2-methyl-2,4-pentanediol, HG), styrene, and water. These may be used individually or in combination of two or more.

[0026] -Dispersant- Dispersants are compounds that adsorb or bind to the surface of particles and have the function of suppressing aggregation of insulating particles through electrostatic repulsion due to Coulomb forces or steric hindrance due to molecular chains. The number-average molecular weight of the dispersant is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of suppressing an increase in the viscosity of the second liquid composition, it is preferably 1,000 to 100,000, more preferably 1,000 to 10,000, and even more preferably 1,000 to 5,000. The dispersant preferably has a dispersive group. When the second liquid composition is used as an electrode material for an electrochemical element, the dispersive group is preferably a nonionic group from the viewpoint of ionic conductivity. Here, nonionic means not having ionic properties, and a nonionic group refers to a substituent that does not have ionic properties.

[0027] The dispersible group is not particularly limited as long as it has a structure that is soluble in the solvent and the auxiliary solvent, but when used as an electrochemical element, an oligoether group is preferred from the viewpoint of ionic conductivity. The oligoether group refers to a group obtained by removing a hydroxyl group from the terminal end of an ethylene glycol or propylene glycol polymer. The number-average molecular weight of the ethylene glycol or propylene glycol polymer is preferably 100 or more and 10,000 or less, and more preferably 100 or more and 5,000 or less. When the number-average molecular weight of the ethylene glycol or propylene glycol polymer is 100 or more, the dispersibility of insulating particles in the liquid composition is improved, and when it is 10,000 or less, the increase in viscosity of the liquid composition can be suppressed. There are no particular restrictions on the method for measuring the number-average molecular weight, and it can be appropriately selected depending on the purpose. For example, it can be measured by gel permeation chromatography. The unbonded end of the oligoether group may be a hydroxyl group, a methoxy group, an ethoxy group, a propoxy group, or the like. Furthermore, using a dispersant containing an oligoether group improves the dispersibility of insulating particles, even when using a highly polar solvent.

[0028] As the dispersant, a polymeric dispersant having an ionic group with a polarity opposite to that of the insulating particles as an adsorbent group is preferred, from the viewpoint of adsorption strength with insulating particles. Commercially available polymer dispersants can be used, and examples of such commercial products include DISPERBYK®-103, DISPERBYK-118, DISPERBYK-2155 (all manufactured by Bic Chemie), NOPCOSPERSE®-092, SN-SPERSE-2190, SN-DISPERSANT-9228 (all manufactured by Sunnopco), Esream® AD-3172M, Esream 2093, Marialim® AKM-0513, Marialim HKM-50A, Marialim HKM-150A, Marialim SC-0505K, Marialim SC-1015F, Marialim SC-0708A (all manufactured by NOF Corporation). These may be used individually or in combination of two or more. The content of the polymer dispersant is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.01% by mass or more and 10% by mass or less relative to the particles, and more preferably 0.1% by mass or more and 10% by mass or less from the viewpoint of the dispersibility of the particles.

[0029] -resin- The resin acts as a dispersant for particles in the second liquid composition, or as a binder for particles in the insulating layer. Furthermore, the inclusion of the resin improves the abrasion resistance of the electrode and the adhesion between the insulating layer and the electrode substrate.

[0030] The resin preferably has an acid group or a salt thereof as a functional group. Furthermore, considering the conduction of lithium ions within the insulating layer, high single-ion conductivity is preferable. As the acid group or salt thereof, a sulfonic acid group or a sulfonate salt is preferred. Furthermore, the primary particle diameter estimated from the BET specific surface area of ​​the particles contained in the insulating layer is very small, less than 40 nm. In a second liquid composition containing such particles, the number of particles per unit volume is greater than in conventional compositions. From the viewpoint of dispersion, it is preferable that an appropriate amount of resin is bonded to each particle. For this reason, particles with a small primary particle diameter estimated from the BET specific surface area tend to have a large amount of resin. A large amount of resin leads to an increase in the viscosity of the second liquid composition, and if the viscosity is too high, it becomes difficult to eject the second liquid composition, for example, by an inkjet method. Therefore, it is important to improve the affinity between the particles and the resin in order to reduce the amount of resin.

[0031] To improve the affinity between the resin and the particle surface and to enable the resin to be efficiently adsorbed onto the particle surface, it is preferable that the functional groups of the resin have acidic groups that have high affinity with the particles, such as sulfonic acid groups, sulfonate salts, sulfonic acid ester groups, carboxylic acid groups, carboxylic acid salts (salts are alkali metals, ammonium salts, amine compounds), carboxylic acid ester groups, carboxylic acid anhydrides, phosphate groups, and phosphate ester groups. It is even more preferable that the resin has sulfonic acid groups or sulfonate salts (salts are alkali metals, ammonium salts, amine compounds) to improve the performance of the electrochemical element. Examples of alkali metals include Li, Na, and K. Examples of amine compounds include monoethanolamine, diethanolamine, and triethanolamine.

[0032] As resins having sulfonic acid groups or salts thereof, commercially available products can be used. Examples of such commercially available products include aqueous polystyrene sulfonic acid solution (manufactured by Sigma-Aldrich), aqueous poly(2-acrylamido-2-methyl-1-propanesulfonic acid) solution (manufactured by Sigma-Aldrich), Nafion™ dispersion solution (manufactured by Sigma-Aldrich), Aquivion D75-25BS dispersion solution (manufactured by Sigma-Aldrich), sulfonated polyethersulfone (manufactured by Konishi Chemical Co., Ltd.), polysulfone (manufactured by Sigma-Aldrich), and poly(1,4-phenylene ether-ether-sulfone) (manufactured by Sigma-Aldrich). The number-average molecular weight (Mn) of the resin having an acid group or a salt thereof is preferably 1,000 to 100,000, more preferably 1,000 to 10,000 from the viewpoint of dispersion stability of the liquid composition, and even more preferably 1,000 to 5,000 from the viewpoint of inkjet ejection performance. The number-average molecular weight of resins containing acidic groups or salts thereof can be measured, for example, by gel permeation chromatography (GPC). The mass ratio of resin to particles is preferably 0.01 to 10, preferably 1 to 10 from the viewpoint of particle dispersibility, and more preferably 2 to 5 from the viewpoint of the electrode's liquid retention.

[0033] The second liquid composition may use resins other than those having the acid group or salt thereof. From the viewpoint of the dischargeability of the second liquid composition, the other resin is preferably a resin emulsion or resin particles. Examples of other resins include resins containing acrylic acid, methacrylic acid, fumaric acid, vinylbenzoic acid, and trimeric acid as repeating unit structures. Specifically, examples include styrene, polyethylene glycol, polyester, styrene-butadiene resin (SBR), acrylic resin, urethane resin, polyvinylpyrrolidone (PVP), and polyvinylidene fluoride (PVDF). The second liquid composition may further contain monomers and polymerization initiators as resin precursors. In this case, the resin is produced by heating or irradiating the second liquid composition with light.

[0034] -Other ingredients- The second liquid composition may further contain other components depending on the purpose, such as adjusting viscosity, adjusting surface tension, controlling solvent evaporation, improving additive solubility, improving particle dispersibility, or sterilization. Examples of these other components include surfactants, pH adjusters, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, and chelating agents.

[0035] The second liquid composition is not particularly limited and can be produced using known dispersion devices. Examples of such dispersion devices include stirrers, ball mills, bead mills, ring mills, high-pressure dispersers, rotary high-speed shearers, and ultrasonic dispersers.

[0036] In the liquid composition set of the present invention, it is preferable that the melting point of the first liquid composition is higher than the melting point of the second liquid composition. This relationship allows for smooth application of the second liquid composition to the electrode substrate while suppressing solidification. In the liquid composition set of the present invention, it is preferable that the boiling point and vapor pressure (evaporation rate) of the first liquid composition are higher than the boiling point and lower than the vapor pressure of the second liquid composition. By having such a relationship, a smoother insulating layer can be formed. The liquid composition set may have a plurality of first liquid compositions or a plurality of second liquid compositions.

[0037] The liquid composition set of the present invention is not particularly limited and can be appropriately selected depending on the purpose, but is preferably used in the electrode manufacturing method described below.

[0038] (Method of manufacturing electrodes) The electrode manufacturing method of the present invention comprises a first liquid composition application step, a first liquid composition solidification step, and a second liquid composition deposition step, and preferably includes an electrode composite layer formation step and a drying step, and further includes other steps as necessary.

[0039] <First liquid composition application step> The first liquid composition application step is a step of applying the first liquid composition to the surface of an electrode substrate having an opening on its surface, before the second liquid composition, so that the second liquid composition containing particles can be deposited on the surface.

[0040] -Electrode base- The electrode substrate includes an electrode composite layer and a current collector. Since typical electrode composite layers have a structure in which particulate active material is superimposed, the electrode composite layer surface or at least the surface has pores with openings. The shape, size, and structure of the opening are not particularly limited as long as the particles contained in the second liquid composition can seep into the electrode composite layer through the opening, thereby forming a mixed layer containing the active material and the particles contained in the second liquid composition. These can be appropriately selected according to the purpose. The presence of the aforementioned opening can be confirmed, for example, by optical microscopy, surface SEM, cross-sectional SEM, stylus-type surface roughness meter, atomic force microscope, etc. Furthermore, the presence of a mixed layer can be determined by cross-sectional SEM observation, based on the presence of active material in the up, down, left, and right directions of the particles contained in the second liquid composition.

[0041] In this case, when the second liquid composition is applied, the particles, along with the dispersion medium contained in the liquid composition, become embedded in the electrode composite layer, and areas that cannot be fully covered by the insulating layer may be formed. In other words, if the electrode substrate has a structure that allows insulating particles to permeate, such as the electrode composite layer, the insulating layer may become embedded in the electrode composite layer, and areas that cannot be fully covered by the insulating layer may be formed. This is more pronounced when the cross-sectional area of ​​the opening on the surface of the electrode substrate is such that it includes the largest cross-sectional area of ​​the particles contained in the insulating layer. Furthermore, this is also more pronounced when the electrode substrate has communicating holes in which the holes communicate with each other within the electrode substrate.

[0042] In addition, in general electrode composite layers, a liquid composition for electrode composite layers is applied to increase the electrode capacity, and after drying, the formed electrode composite layer is pressed. In the case of a negative electrode, flaky natural graphite may be used as the negative electrode active material, but it may also be spherical to increase the electrode density. Even when pressing negative electrode active materials of such shape, the surface shape after pressing depends on the shape of the negative electrode active material, and it is easy to form irregularities, and voids are likely to occur between the negative electrode active materials. In these cases, the arithmetic surface roughness of the electrode composite layer tends to be high. If the second liquid composition is applied to the surface of an electrode composite layer with a high arithmetic surface roughness of 0.1 μm to 5 μm without applying the first liquid composition, and the thickness of the insulating layer formed is thinner than the surface irregularities of the electrode composite layer, the insulating layer tends to be embedded in the irregularities of the electrode composite layer surface in terms of cross-sectional shape.

[0043] The method for measuring arithmetic surface roughness is not particularly limited and can be appropriately selected depending on the purpose. Examples of contact-type measurement methods include atomic force microscopes and stylus-type roughness meters. For non-contact measurement methods, for example, arithmetic surface roughness can be obtained from depth-of-field composite images of an optical microscope. Specifically, depth-of-field composite images can be created using a digital microscope (VHX-7000, manufactured by Keyence Corporation) to obtain arithmetic surface roughness. In this case, since arithmetic surface roughness is affected by the observation magnification and observation pitch of the depth-of-field composite image, the observation magnification should be set to about 100x to obtain a higher-resolution image, and the depth-of-field composite image should be obtained at a finer pitch than the observed arithmetic surface roughness pitch. Multiple images may be combined to obtain a wide field of view image so that the observation field is sufficiently wide. The apparatus used for the observation is not particularly limited and can be appropriately selected depending on the purpose.

[0044] As described above, when the insulating layer becomes embedded in the irregularities on the surface of the electrode composite layer, the whiteness (L) of the surface of the electrode composite layer * When measuring this, the uncoated area turns black, so the whiteness (L * ) decreases. The whiteness (L * This can be measured using, for example, a colorimeter (RM200QC, manufactured by X-Rite). Although the negative electrode was used as an example, it is not limited to the negative electrode; the positive electrode can also be used. Regarding the surface of the positive electrode, if the arithmetic surface roughness is between 0.1 μm and 5 μm, the insulating layer tends to become embedded in the irregularities of the electrode composite layer surface.

[0045] The aforementioned first liquid composition is the first liquid composition in the liquid composition set of the present invention. There are no particular limitations on the method for applying the first liquid composition, and it can be appropriately selected depending on the purpose. Examples include dip coating, spray coating, spin coating, bar coating, slot die coating, doctor blade coating, curtain coating, offset printing, gravure printing, flexographic printing, letterpress printing, screen printing, inkjet printing, and electrophotographic printing using a liquid development method. Among these, spray coating and inkjet printing are preferred, and inkjet printing is more preferred because it is possible to control the position at which the liquid droplets are ejected.

[0046] The temperature at which the first liquid composition is applied can be set without any particular limitations, as long as the first liquid composition is a liquid. The first liquid composition is a liquid at room temperature (25°C), and when applied by an inkjet method, it can be applied without solidifying before droplet placement, without being affected by the ambient temperature during ejection from the inkjet head. Therefore, the inkjet method is more preferable than the method of applying a solid by heating it.

[0047] <First liquid composition solidification step> The first liquid composition solidification step is a step of solidifying the first liquid composition applied to the surface. The solidification of the first liquid composition is preferably carried out by cooling the first liquid composition. If the first liquid composition solidifies, the interval between the application of the first liquid composition and the second liquid composition may be approximately simultaneous. The application interval depends on the performance of the cooling device for cooling the first liquid composition applied to the electrode substrate. Therefore, from the viewpoint of productivity, it is preferable to apply the first liquid composition onto the electrode substrate, which has been cooled in advance to a predetermined temperature at which the first liquid composition solidifies upon contact.

[0048] The solidification method in the first liquid composition solidification step is not particularly limited and can be appropriately selected depending on the purpose. Examples include rollers connected to chillers (water-cooled, air-cooled, etc., no particular restrictions), thermoelectric cool plates (cooling stages, cooling plates, etc.), thermoelectric cooling rollers, air coolers, dry ice powder cooling devices, liquid nitrogen spray devices, and cooling mechanisms combining liquid nitrogen cold traps and conveying rollers. These may be used individually or in combination of two or more. To prevent condensation or frost from forming on the electrodes during cooling, it is preferable to cool them under a dry air or nitrogen atmosphere. If condensation or frost forms on the electrodes, the second liquid composition may aggregate, leading to unevenness, and the active material in the electrode substrate, especially the positive electrode active material, and the binder, especially the water-soluble binder, may be adversely affected by water, potentially causing a deterioration in performance. Furthermore, if the interval between the application of the first liquid composition and its drying is approximately simultaneous, and no condensation or frost occurs on the electrodes, solidification is possible under any atmospheric conditions.

[0049] <Second liquid composition deposition process> The second liquid composition deposition step is a step of depositing the second liquid composition onto the surface by applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition.

[0050] There are no particular limitations on the method of applying the second liquid composition, and it can be appropriately selected depending on the purpose. Examples include dip coating, spray coating, spin coating, bar coating, slot die coating, doctor blade coating, curtain coating, offset printing, gravure printing, flexographic printing, letterpress printing, screen printing, inkjet printing, and electrophotographic printing using a liquid development method. Among these, spray coating and inkjet printing are preferred, and inkjet printing is more preferred because it is possible to control the position at which the liquid droplets are ejected.

[0051] When using the inkjet method, if the first liquid composition and the second liquid composition are dispensed from the ejection head almost simultaneously, a mixture of the first liquid composition and the second liquid composition, in which particles have aggregated, is applied to the electrode substrate. Examples of methods for ejecting the second liquid composition in the inkjet method include methods that impart mechanical energy to the second liquid composition and methods that impart thermal energy to the second liquid composition. Among these, the method that imparts mechanical energy to the second liquid composition is preferred in terms of dispersion stability. One method for applying the aforementioned mechanical energy is a piezoelectric method, in which a voltage is applied to a piezoelectric element in close contact with the liquid chamber to deform the liquid chamber, thereby pushing out the second liquid composition from the nozzle and discharging it. One method for supplying the aforementioned thermal energy is a thermal method that rapidly applies heat to the second liquid composition using a heater or the like, and utilizes the bubbles generated when the second liquid composition boils. When using a liquid dispensing method, techniques based on the liquid dispensing principles of known liquid dispensing devices can be applied. In this case, it is preferable to use a solvent that is resistant to the flow path and nozzle of the liquid dispensing head installed in the liquid dispensing device.

[0052] <Electrode composite layer formation process> The electrode composite layer formation step is a step of applying a liquid composition for the electrode composite layer onto a current collector to form an electrode composite layer. The electrode composite layer may be formed on one side of the current collector or on both sides of the current collector. The liquid composition for the electrode composite layer preferably contains an active material and a dispersion medium, and more preferably contains a conductive additive and a dispersant, and may further contain other components as needed. Examples of methods for applying the liquid composition for the electrode composite layer include the comma coater method, the die coater method, the curtain coat method, the spray coat method, and the liquid discharge method.

[0053] -Current collector- The material constituting the current collector is not particularly limited, as long as it is a material that is conductive and stable to the applied potential, as is commonly used for current collectors. Examples of current collectors include negative electrode current collectors for creating a negative electrode and positive electrode current collectors for creating a positive electrode.

[0054] -Active material- As the active material, either a positive electrode active material or a negative electrode active material can be used. The positive electrode active material or the negative electrode active material may be used alone, or two or more may be used in combination. The positive electrode active material is not particularly limited as long as it is capable of inserting or releasing alkali metal ions, but alkali metal-containing transition metal compounds can be used. Examples of alkali metal-containing transition metal compounds include lithium-containing transition metal compounds such as composite oxides containing lithium and one or more elements selected from the group consisting of cobalt, manganese, nickel, chromium, iron, and vanadium. Examples of lithium-containing transition metal compounds include lithium cobaltate, lithium nickelate, and lithium manganeseate. As alkali metal-containing transition metal compounds, polyanionic compounds having an XO4 tetrahedron (X=P,S,As,Mo,W,Si, etc.) in their crystal structure can also be used. Among these, lithium-containing transition metal phosphate compounds such as lithium iron phosphate and lithium vanadium phosphate are preferred in terms of cycle characteristics, and lithium vanadium phosphate is particularly preferred in terms of lithium diffusion coefficient and power characteristics. Furthermore, in terms of electronic conductivity, it is preferable that the polyanionic compound is composited with a conductive additive such as a carbon material on its surface.

[0055] The negative electrode active material is not particularly limited as long as it is capable of inserting or releasing alkali metal ions, but a carbon material containing graphite having a graphite-type crystal structure can be used. Examples of carbon materials include natural graphite, artificial graphite, hard carbon (difficult to graphitize), and soft carbon (easily graphitizable). Examples of negative electrode active materials other than carbon materials include lithium titanate and titanium oxide. Furthermore, from the standpoint of energy density for non-aqueous energy storage elements, it is preferable to use high-capacity materials such as silicon, tin, silicon alloys, tin alloys, silicon oxide, silicon nitride, and tin oxide as the negative electrode active material.

[0056] -Dispersion medium- Examples of dispersion media include aqueous dispersion media such as water, ethylene glycol, and propylene glycol, as well as N-methyl-2-pyrrolidone, 2-pyrrolidone, cyclohexanone, butyl acetate, mesitylene, 2-n-butoxymethanol, 2-dimethylethanol, and N,N-dimethylacetamide. These may be used individually or in combination of two or more.

[0057] -Conductive additive- As conductive additives, for example, conductive carbon black produced by furnace processes, acetylene processes, gasification processes, etc., as well as carbon materials such as carbon nanofibers, carbon nanotubes, graphene, and graphite powder can be used. As conductive additives other than carbon materials, for example, metal particles such as aluminum and metal fibers can be used. The conductive additive may be compounded with the active material beforehand.

[0058] -Dispersant- Examples of dispersants include polymeric dispersants such as polycarboxylic acid-based dispersants, naphthalene sulfonic acid formalin condensation-based dispersants, polyethylene glycol, polycarboxylic acid partial alkyl ester-based dispersants, polyether-based dispersants, and polyalkylene polyamine-based dispersants; surfactants such as alkyl sulfonic acid-based dispersants, quaternary ammonium salt-based dispersants, higher alcohol alkylene oxide-based dispersants, polyhydric alcohol ester-based dispersants, and alkyl polyamine-based dispersants; and inorganic dispersants such as polyphosphate-based dispersants.

[0059] -Other ingredients- Other ingredients are not particularly limited and can be selected as appropriate depending on the purpose. Examples include dispersants, surfactants, pH adjusters, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, and chelating agents.

[0060] <Drying process> There are no particular restrictions on the drying method in the drying process, and it can be appropriately selected according to the purpose. For example, the electrode that has undergone the second liquid composition deposition process may be dried from below, i.e., from the electrode substrate side, or from above, i.e., from the second liquid composition side, or the entire electrode may be dried uniformly. Methods for drying from below, i.e., from the electrode substrate side, include, for example, hot plate drying and induction heating.

[0061] Methods for drying from above, i.e., from the side of the second liquid composition, include, for example, vacuum drying and infrared drying. One method for uniformly drying the entire electrode is, for example, hot air drying. In the aforementioned hot air drying method, gas is circulated to raise the temperature inside the furnace to a constant temperature. When a highly thermally conductive electrode substrate coated with the second liquid composition is introduced into or transported into the furnace, the entire electrode is heated instantaneously, thus drying the entire electrode uniformly on a macroscopic level. On the other hand, on a microscopic level, drying occurs from above, i.e., from the side of the second liquid composition, due to the convection of the circulating gas.

[0062] Furthermore, in the hot plate drying method described above, although the electrode substrate is in contact with the electrode from below, by preheating to a certain temperature, the gas directly above the hot plate is heated and convects, so microscopically, drying also occurs from above the electrode. These drying methods can be appropriately selected or combined depending on the purpose. Among these, the hot air drying method or the infrared drying method is more preferable from the viewpoint of being applicable to a roll-to-roll apparatus. Among these, it is preferable to dry from above, i.e., from the side of the second liquid composition. By drying the first liquid composition after or simultaneously with drying the second liquid composition, the seepage of the second liquid composition into the electrode composite layer, which is the electrode substrate, is suppressed, and a uniform insulating layer can be formed.

[0063] <Other processes> Other processes are not particularly restricted and can be selected as appropriate depending on the purpose, such as the transportation process.

[0064] Here, an embodiment of a coating apparatus having a cooling device will be described in detail with reference to the drawings. Note that the number, position, shape, etc., of the components are not limited to this embodiment, and may be set to a number, position, shape, etc., that is preferable for carrying out the present invention.

[0065] Figure 1 is a schematic diagram of a coating apparatus with a cooling device. A rolled electrode substrate is placed in the transport section, and the electrode substrate is transported by the transport mechanism in the transport section. In the coating section 1, the first liquid composition is applied to the electrode substrate. Next, in the cooling section, the first liquid composition on the electrode substrate is frozen, forming a uniform surface on the electrode substrate. The electrode with the uniform surface substrate is then coated with the second liquid composition in the coating section 2, enters the drying section, and the dispersion medium contained in the second liquid composition and the first liquid composition are dried. After that, it passes through the air cooling section and is wound into a roll again in the winding section.

[0066] Figure 2 is a modified version of Figure 1, in which the positions of the coating section 1 and the cooling section are swapped. Although not shown, the cooling section and the conveying section in Figure 2 may be integrated. As mentioned above, the cooling section can be placed under dry air or a nitrogen atmosphere to prevent condensation, frost, etc., or under any atmosphere if the performance of the cooling device allows coating, cooling, and drying to be performed almost simultaneously and prevents condensation, frost, etc. Although not shown in Figures 1 and 2, additional rollers or control devices may be used as appropriate to improve the stability of conveying and winding.

[0067] Figures 3, 4, 5, and 6 are detailed diagrams showing specific examples of the configurations of coating unit 1, coating unit 2, and cooling unit. Unless otherwise specified, the coating unit may be configured to coat both sides of the electrode substrate at once, and the arrangement of components can be selected as appropriate. The atmosphere control region can be controlled, for example, by creating a positive pressure with dry air or nitrogen in an area enclosed by partitions to the extent that it does not hinder the transport of the electrode substrate.

[0068] Figure 3 is a schematic diagram showing an example of the details of the coating section 1, coating section 2, and cooling section of the coating apparatus shown in Figure 1. In Figure 3, the cooling section uses a device that cools the electrode substrate via nozzles, such as an air cooler, a dry ice powder cooling device, or a liquid nitrogen spray device. Figure 4 is a schematic diagram showing an example of the details of the coating section 1, coating section 2, and cooling section of the coating apparatus shown in Figure 2. In Figure 4, the cooling section uses a device that cools the electrode substrate via nozzles, such as an air cooler, a dry ice powder cooling device, or a liquid nitrogen spray device. Figure 5 is a schematic diagram showing another example of the details of the coating section 1, coating section 2, and cooling section of the coating apparatus shown in Figure 1. In Figure 5, the cooling section uses a device that cools the electrode substrate with rollers having a cooling mechanism. Figure 6 is a schematic diagram showing another example of the details of the coating section 1, coating section 2, and cooling section of the coating apparatus shown in Figure 2. In Figure 6, the cooling section uses a device that cools the electrode substrate with rollers having a cooling mechanism.

[0069] Here, Figure 7 is a schematic diagram showing an example of a coating apparatus having a cooling device. In the coating apparatus 11 of Figure 7, the cartridges 20, each containing a first liquid composition and a second liquid composition, are housed in a carriage 18 within the main body housing 12. In this state, the first liquid composition and the second liquid composition are supplied from the cartridge 20 to the discharge head 18a mounted on the carriage 18. The discharge head 18a can discharge the first liquid composition and the second liquid composition almost simultaneously. The discharge head 18a mounted on the carriage 18 is guided and moved by the guide shafts 21 and 22 by a timing belt 23 driven by the main scanning motor 24. Meanwhile, the electrode base is positioned by the platen 19 to face the discharge head 18a. In Figure 7, 16 represents the gear mechanism, 17 represents the sub-scanning motor, and 26 represents the main scanning motor.

[0070] <Method for manufacturing electrochemical elements> A method for manufacturing an electrochemical element includes a step of manufacturing an electrode using the electrode manufacturing method of the present invention, and further includes other steps as necessary.

[0071] In an electrochemical element, the negative electrode and positive electrode are stacked with a separator in between. Here, the positive electrode is stacked on both sides of the negative electrode. Furthermore, lead wires are connected to the current collector for the negative electrode, and lead wires are connected to the current collector for the positive electrode.

[0072] The negative electrode is the same as the negative electrode described above, except that a negative electrode composite material layer is formed on both sides of the negative electrode current collector. The positive electrode is the same as the positive electrode described above, except that a positive electrode composite material layer is formed on both sides of the positive electrode current collector. Furthermore, there are no particular restrictions on the number of stacked negative and positive electrodes in the electrode element. Also, the number of negative electrodes and the number of positive electrodes in the electrode element may be the same or different.

[0073] -Separator- A separator is placed between the negative and positive electrodes to prevent a short circuit between them. The separator is not particularly limited and can be appropriately selected depending on the purpose. Examples of separators include paper such as kraft paper, vinylon blended paper, and synthetic pulp blended paper, cellophane, polyethylene graft membranes, polyolefin nonwovens such as polypropylene meltblown nonwovens, polyamide nonwovens, glass fiber nonwovens, and micropore membranes. The size of the separator is not particularly limited, as long as it can be used in the electrochemical element. The separator may have a single-layer structure or a multi-layer structure. Note that the separator can be omitted when using a solid electrolyte.

[0074] An electrochemical element has an electrolyte layer formed by injecting an electrolyte solution or a non-aqueous electrolyte into an electrode element, and is sealed by an outer casing. In an electrochemical element, the lead wires are led out to the outside of the outer casing. The electrochemical element may have other components as needed. There are no particular limitations on the electrochemical element, and examples include lithium-ion secondary batteries. The shape of the electrochemical element is not particularly limited and can be appropriately selected according to the purpose. Examples include laminate type, cylinder type with sheet electrodes and separators arranged in a spiral, cylinder type with an inside-out structure combining pellet electrodes and separators, and coin type with stacked pellet electrodes and separators.

[0075] -Aqueous electrolyte solution- There are no particular restrictions on the electrolyte salts that make up the aqueous electrolyte solution, and they can be appropriately selected depending on the purpose. Examples include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, ammonium chloride, zinc chloride, zinc acetate, zinc bromide, zinc iodide, zinc tartrate, and zinc perchloride.

[0076] -Non-aqueous electrolytes- As the non-aqueous electrolyte, a solid electrolyte or a non-aqueous electrolyte solution can be used. The non-aqueous electrolyte solution is an electrolyte solution in which the electrolyte salt is dissolved in a non-aqueous solvent.

[0077] There are no particular restrictions on the non-aqueous solvent, but it is preferable to use, for example, an aprotic organic solvent. As the aprotic organic solvent, carbonate-based organic solvents such as linear carbonates and cyclic carbonates can be used. Among these, linear carbonates are preferred due to their high solubility of electrolyte salts. Furthermore, it is preferable that the aprotic organic solvent has low viscosity. Examples of the aforementioned chain-like carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC). The content of the linear carbonate in the non-aqueous solvent is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 50% by mass or more. When the content of linear carbonates in the non-aqueous solvent is 50% by mass or more, even if the non-aqueous solvent other than the linear carbonates is a cyclic substance with a high dielectric constant (e.g., cyclic carbonate, cyclic ester), the content of the cyclic substance will be reduced. As a result, even when a high-concentration non-aqueous electrolyte of 2M or more is prepared, the viscosity of the non-aqueous electrolyte will be low, and the penetration of the non-aqueous electrolyte into the electrode and ion diffusion will be good.

[0078] Examples of the cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC). In addition to carbonate-based organic solvents, other non-aqueous solvents that can be used include, for example, ester-based organic solvents such as cyclic esters and linear esters, and ether-based organic solvents such as cyclic ethers and linear ethers. Examples of the aforementioned cyclic esters include γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone. Examples of the chain-like esters include alkyl propionate esters, dialkyl malonate esters, alkyl acetate esters (e.g., methyl acetate (MA), ethyl acetate), and alkyl formate esters (e.g., methyl formate (MF), ethyl formate). Examples of the cyclic ethers include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, and 1,4-dioxolane. Examples of the chain-like ethers include 1,2-dimethylethane (DME), diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.

[0079] The electrolyte salt is not particularly limited as long as it has high ionic conductivity and can be dissolved in a non-aqueous solvent. The electrolyte salt preferably contains halogen atoms. The electrolyte salt can be composed of cations or anions. Examples of cations constituting the electrolyte salt include lithium ions (lithium salts). Examples of anions constituting the electrolyte salt include BF4 - PF6 - AsF6 - CF3SO3 - , (CF3SO2)2N - (C2F5SO2)2N - These are some examples.

[0080] The lithium salt is not particularly limited and can be appropriately selected depending on the purpose. Examples of the lithium salts include lithium hexafluorophosphate (LiPF6), lithium borofluoride (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethasulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2), and lithium bis(pentafluoroethylsulfonyl)imide (LiN(C2F5SO2)2). These may be used individually or in combination of two or more. Among these, LiPF6 is preferred in terms of ionic conductivity, and LiBF4 is preferred in terms of stability.

[0081] There are no particular restrictions on the concentration of the electrolyte salt in the non-aqueous electrolyte, and it can be appropriately selected according to the purpose. For example, if the non-aqueous energy storage element is of the swing type, the concentration of the electrolyte salt in the non-aqueous electrolyte is preferably 1 mol / L or more and 2 mol / L or less, and if the non-aqueous energy storage element is of the reserve type, it is preferably 2 mol / L or more and 4 mol / L or less.

[0082] The above describes an example in which an electrode substrate includes an electrode composite layer, the electrode composite layer has openings into which particles contained in the second liquid composition can permeate, and particles contained in the second liquid composition are deposited on the electrode substrate. However, there are no particular limitations on the electrode substrate as long as it has openings into which particles contained in the second liquid composition can permeate, and can be appropriately selected according to the purpose. Examples include a solid electrolyte layer and a separator.

[0083] <Applications of electrochemical elements> Applications of electrochemical elements include, for example, lithium-ion secondary batteries, magnesium-ion secondary batteries, sodium-ion secondary batteries, and sodium-ion secondary batteries. The electrochemical element can be applied to, for example, battery-powered vehicles such as EVs and PHVs, wearable devices such as head-mounted displays and smartwatches, smartphones, laptops, pen-input computers, mobile computers, e-book players, cell phones, portable fax machines, portable copiers, portable printers, headphone stereos, video cameras, LCD televisions, handheld vacuum cleaners, portable CDs, MiniDiscs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting fixtures, toys, game consoles, clocks, strobes, cameras, and the like. Among these, the electrochemical element according to this embodiment is preferably used in battery-powered vehicles that require many electrochemical elements, and in wearable devices that are in close contact with the user's body. [Examples]

[0084] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0085] In the following examples and comparative examples, the median diameter of the particles, the viscosity of the liquid composition, and the arithmetic surface roughness of the electrode composite layer were measured by the following methods.

[0086] [Particle size distribution] The particle size distribution of the obtained liquid composition was measured at room temperature (25°C) using a laser diffraction particle size distribution analyzer Mastersizer 3000 (Malvern). The diameter at the maximum value of the particle size distribution in the measured liquid composition was defined as the median diameter (D 50 ) was calculated as follows.

[0087] [Viscosity of liquid compositions] The viscosity of the obtained liquid composition at 100 rpm was measured at room temperature (25°C) using a TV25 type viscometer (cone plate type viscometer, manufactured by Toki Sangyo Co., Ltd.).

[0088] [Arithmetic surface roughness of electrode composite layer] A depth-stacked image was acquired at a magnification of 100x using a digital microscope (VHX-7000, manufactured by Keyence Corporation), and the arithmetic surface roughness was measured.

[0089] (Example 1) <First liquid composition 1> Dimethyl sulfoxide (DMSO) was used as the first liquid composition 1. The viscosity of the first liquid composition 1 at 25°C was 2 mPa·s.

[0090] <Example 1 of manufacturing the second liquid composition> -Preparation of dispersion 1- A polyfunctional comb-type functional polymer (SC-0708A, manufactured by NOF Corporation) having maleic anhydride groups in the main chain and polyoxyalkylene chains in the graft chains, and 50% by mass of alumina particles (AKP3000, manufactured by Sumitomo Chemical Co., Ltd.) with a central particle size of 0.8 μm were thoroughly dispersed in 47.5% by mass of ethyl lactate to obtain dispersion 1 with a solid content of 50% by mass. The resulting dispersion 1 has a median diameter (D 50 ) is 1 μm or less, D 90 The particle size was 2 μm or less.

[0091] -Preparation of the second liquid composition 1- The obtained dispersion 1 was mixed with 80.0% by mass and 20.0% by mass of ethyl lactate to obtain a second liquid composition 1 with a solid content of 40% by mass. The obtained second liquid composition 1 has a median diameter (D 50 ) is 1 μm or less, D 90 The particle size was 2 μm or less. The viscosity at 25°C was 7 mPa·s.

[0092] <Liquid Composition Set 1> The first liquid composition 1 and the second liquid composition 1 were combined to form liquid composition set 1.

[0093] <Fabrication of the negative electrode> A slurry for the negative electrode composite layer, obtained by kneading negative electrode active material (SCMG-XRs, manufactured by Showa Denko K.K.), water, and resin (AZ-9129, manufactured by Nippon Zeon Co., Ltd., and Selogen HS-6, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to both sides of a copper foil current collector for the negative electrode using a comma coater, and then dried to form the negative electrode composite layer. Next, the formed negative electrode composite layer was pressed with a force of approximately 100 kN to produce the negative electrode.

[0094] Next, using liquid composition set 1, an arithmetic mean roughness of 1.3 μm and a volume density of 1.2 g / cm³ were obtained. 3 An insulating layer was formed on the negative electrode composite layer. At this time, the first liquid composition 1 of liquid composition set 1 was applied by bar coating with a basis weight of 0.7 mg / cm². 2 The mixture was prepared in such a manner. The second liquid composition 1 of liquid composition set 1 was prepared by inkjet printing with a basis weight of 0.7 mg / cm². 2 It was assigned in such a way that it would result in the following:

[0095] The negative electrode composite layer coated with the first liquid composition 1 was cooled to below room temperature (25°C) using a thermoelectric cool plate (SA-800, manufactured by Sansho Co., Ltd.) to smooth the surface of the negative electrode composite layer, after which the second liquid composition 1 was applied and dried using a hot plate. Furthermore, in order to clarify which physical properties of the liquid compound are responsible for the effect of adding the main liquid compound (elementary solvent) to the first liquid composition 1, the physical properties of the main liquid compound are listed in Table 1.

[0096] The physical properties listed in Table 1 are as follows: • Melting point (°C): Mp Hansen solubility parameter ((J / cm) 3 ) 1 / 2 ): δD, δP, δH ·Molecular weight (g / mol): Mwt ·Density (g / cm 3 Density • Molecular volume (cm³) 3 / mol): Mvol • tot HSP 2 (J / cm 3) tot HSP 2 It is calculated using the following formula. tot HSP 2 =δD 2 +δP 2 +δH 2 • Cohesive energy density (J / mol): Mvol × tot HSP 2 Cohesive energy density: Mvol × tot HSP 2 Molecular volume: Mvol and tot HSP 2 This is the material property value obtained by multiplying by [a certain factor].

[0097] Hansen's solubility parameter is a representation of the solubility parameter introduced by Hildebrand, divided into three components: a dispersion term δD, a polarity term δP, and a hydrogen bonding term δH, and expressed in three-dimensional space. The dispersion term δD represents the effect due to dispersion forces, the polarity term δP represents the effect due to inter-dipole forces, and the hydrogen bonding term δH represents the effect due to hydrogen bonding forces. The Hansen solubility parameters used were those described in Charles M. Hansen's "Hansen Solubility Parameters: A Users' Handbook" (CRC Press, 2007). For the following two liquid compounds not mentioned in the above literature, the values ​​described in the following literature were used. The HSP value for DMI (1,3-dimethyl-2-imidazolidinone) was taken from the value described in Japanese Patent Publication No. 6787147. The HSP value for dimethyl succinate was calculated using the group contribution method for estimating the Hansen solubility parameter, as described by Stefanis and Panayiotou (Stefanis, E.; Panayiotou, C. Int. J. Thermophys., 29, 568-585.(2008)).

[0098] <Whiteness (L * ) measurement> Whiteness of the negative electrode surface after drying (L *The whiteness (L) of the surface of the negative electrode composite layer before applying liquid composition set 1 was measured using a colorimeter (RM200QC, manufactured by X-Rite). The results are shown in Table 2. * The value measured was 42.

[0099] (Examples 2-19) In Example 1, a liquid composition set was obtained in the same manner as in Example 1, except that the first liquid composition 1 was changed to the main liquid compound (solvent) listed in Table 1. An insulating layer was then formed on the negative electrode using this liquid composition set. Liquid compounds with a melting point Mp of 25°C or higher were heated to a liquid state and then mixed with dimethyl carbonate in a ratio of 8:2 (by weight) of the liquid compound with a melting point Mp of 25°C or higher to dimethyl carbonate. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 2.

[0100] (Comparative Example 1) In Example 1, the second liquid composition 1 was applied to the negative electrode in the same manner as in Example 1, except that the first liquid composition 1 from the liquid composition set 1 was not applied, and an insulating layer was formed on the negative electrode. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 2.

[0101] (Example 20) <Example 2 of manufacturing the second liquid composition> -Preparation of dispersion 2- In preparing dispersion 1, alumina particles (AKP3000, manufactured by Sumitomo Chemical Co., Ltd.) with an average particle size of 0.5 μm and a BET specific surface area of ​​7.8 g / m² were used. 2 Dispersion 2 was obtained in the same manner as the preparation of dispersion 1, except that the α-alumina particles produced by grinding were used instead.

[0102] -Preparation of the second liquid composition 2- In preparing the second liquid composition 1, the second liquid composition 2 was obtained in the same manner as in the preparation of the second liquid composition 1, except that dispersion 1 was replaced with dispersion 2. The viscosity at 25°C was 8 mPa·s.

[0103] In Example 1, a liquid composition set was obtained in the same manner as in Example 1, except that the second liquid composition 1 of liquid composition set 1 was replaced with the second liquid composition 2. An insulating layer was then formed on the negative electrode using this liquid composition set. The arithmetic mean roughness of the negative electrode composite layer was 1.3 μm. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 2.

[0104] (Examples 21-38) In Example 20, a liquid composition set was obtained in the same manner as in Example 20, except that the first liquid composition 1 was replaced with a liquid compound (solvent) listed in Table 2. An insulating layer was then formed on the negative electrode using this liquid composition set. Liquid compounds with a melting point Mp of 25°C or higher were heated to a liquid state and then mixed with dimethyl carbonate in a ratio of 8:2 (by weight) of the liquid compound with a melting point Mp of 25°C or higher to dimethyl carbonate. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 2.

[0105] (Comparative Example 2) In Example 20, the second liquid composition 2 was applied to the negative electrode in the same manner as in Example 20, except that the first liquid composition 1 from liquid composition set 1 was not applied, thereby forming an insulating layer on the negative electrode. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 2.

[0106] [Table 1] *DMSO: Dimethyl sulfoxide *DMI: 1,3-dimethyl-2-imidazolidinone *1: Since it is a solid at 25°C, the viscosity at 25°C of a solution mixed with DMC in a weight ratio of 8:2 is listed. *2: The viscosity value at 25°C is a reference value.

[0107] [Table 2] *DMSO: Dimethyl sulfoxide *DMI: 1,3-dimethyl-2-imidazolidinone

[0108] From the results in Table 2, the whiteness (L) of Examples 1-38 was determined. * ) all refer to the whiteness (L) of the negative electrode composite layer. * ) became higher than 42. In particular, the cohesive energy density A1:Mvol×HSP of the first liquid composition 2 When the concentration is 50,000 J / mol or higher, the whiteness (L) is higher. * The ) was high, indicating that the insulating layer could be uniformly formed on the negative electrode composite layer. Whiteness (L) of Comparative Examples 1-2 without the first liquid composition * The temperature was almost the same as or slightly higher than that of the negative electrode composite layer, indicating that a uniform insulating layer could not be formed on the negative electrode composite layer.

[0109] (Examples 39-66 and Comparative Examples 3-14) <Liquid Composition Set> Using the liquid composition sets of the first and second liquid compositions shown in Table 3, an insulating layer was formed on the negative electrode in the same manner as in Examples 1 to 38 and Comparative Examples 1 to 2. Next, the whiteness (L) of the obtained negative electrode surface * The values ​​were measured in the same manner as in Example 1. The results are shown in Table 3.

[0110] [Table 3] *DMSO: Dimethyl sulfoxide *DMI: 1,3-dimethyl-2-imidazolidinone

[0111] From the results in Table 3, Examples 39-66, which satisfy either (1) or (2) below, showed a higher whiteness (L) compared to Comparative Examples 3-14, which did not satisfy either (1) or (2) below. * The ) was high, indicating that the insulating layer could be uniformly formed on the negative electrode composite layer. (1) The cohesive energy density A1 (J / mol), which is the product of the molecular volume of the solvent in the first liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH), is greater than the cohesive energy density A2 (J / mol), which is the product of the molecular volume of the dispersion medium in the second liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH). (2) The absolute value of the difference (A1-A2) between the cohesive energy density A1 and the cohesive energy density A2 is 5,000 J / mol or less.

[0112] Examples of the present invention are as follows: <1> A first liquid composition application step, in which a first liquid composition is applied to the surface of an electrode substrate having an opening on its surface, before the second liquid composition, such that a second liquid composition containing particles can be deposited on the surface; A first liquid composition solidification step for solidifying the first liquid composition applied to the surface, A second liquid composition deposition step involves applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. This is a method for manufacturing electrodes, characterized by including [a specific component]. <2> The arithmetic surface roughness of the electrode substrate surface is 0.1 μm or more and 5 μm or less, <1> This is a method for manufacturing electrodes as described above. <3> The electrode substrate is an electrode composite layer, <1> from <2> This is a method for manufacturing electrodes as described in any of the above. <4> The electrode substrate is a solid electrolyte layer, <1> from <2> This is a method for manufacturing electrodes as described in any of the above. <5> The electrode substrate is a separator, <1> from <2> This is a method for manufacturing electrodes as described in any of the above. <6> The solidification of the first liquid composition is carried out by cooling the first liquid composition. <1> from <5> This is a method for manufacturing electrodes as described in any of the above. <7> The melting point of the first liquid composition is 0°C or higher and 25°C or lower. <1> from <6> This is a method for manufacturing electrodes as described in any of the above. <8> The first liquid composition application step is performed at a temperature of 25°C or higher. The first liquid composition solidification step is performed at a temperature of 0°C or higher and less than 25°C. <1> from <7> This is a method for manufacturing electrodes as described in any of the above. <9> In the first liquid composition application step, the electrode substrate to which the first liquid composition is applied is at a temperature below the melting point of the first liquid composition. <1> from <8> This is a method for manufacturing electrodes as described in any of the above. <10> The first liquid composition solidification step is performed under either dry air or a nitrogen atmosphere. <1> from <9> This is a method for manufacturing electrodes as described in any of the above. <11> The process includes a heating step of heating the electrode substrate on which the second liquid composition is deposited. <1> from <10> This is a method for manufacturing electrodes as described in any of the above. <12> The second liquid composition is heated to a temperature at which the vapor pressure of the dispersion medium contained in the first liquid composition and the vapor pressure of the liquid compound contained in the first liquid composition are equal to or less than atmospheric pressure. <11> This is a method for manufacturing electrodes as described above. <13> The process includes heating the second liquid composition to a temperature at which the vapor pressure of the dispersion medium contained in the second liquid composition becomes equal to or equal to atmospheric pressure, and heating the first liquid composition to a temperature at which the vapor pressure of the liquid compound contained in the first liquid composition becomes equal to or equal to atmospheric pressure. <11> This is a method for manufacturing electrodes as described above. <14> A first liquid composition containing a liquid compound, A second liquid composition containing particles and a dispersion medium, This is a liquid composition set characterized by satisfying either (1) or (2) below. (1) The cohesive energy density A1 (J / mol), which is the product of the molecular volume of the liquid compound in the first liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH), is greater than the cohesive energy density A2 (J / mol), which is the product of the molecular volume of the dispersion medium in the second liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH). (2) The absolute value of the difference (A1-A2) between the cohesive energy density A1 and the cohesive energy density A2 is 5,000 J / mol or less. <15> The cohesive energy density A1 is 50,000 J / mol or more, <14> This is a set of liquid compositions as described above. <16> The viscosity of the first liquid composition at 25°C is 50 mPa·s or less. <14> from <15> This is a liquid composition set as described in any of the following. <17> The first liquid composition consists of one type of liquid compound, <14> from <16> This is a liquid composition set as described in any of the following. <18> The first liquid composition consists of multiple types of liquid compounds, <14> from <16> This is a liquid composition set as described in any of the following. <19> The particles are inorganic oxide particles, <14> from <18> This is a liquid composition set as described in any of the following. <20> The particles are alumina, <14> from <19> This is a liquid composition set as described in any of the following.

[0113] The aforementioned <1> from <13> A method for manufacturing an electrode as described in any of the above, and the <14> from <20> According to any of the liquid composition sets described above, the problems of the conventional methods can be solved and the objectives of the present invention can be achieved. [Explanation of symbols]

[0114] 11 Coating equipment 12 Main Unit 18 Carriage 18a Discharge head 20 cartridges 21 Guide shaft 22 Guide shaft 23 Timing belt 24 Main scanning motor [Prior art documents] [Patent Documents]

[0115] [Patent Document 1] Japanese Patent Publication No. 2017-123269

Claims

1. A first liquid composition application step, in which a first liquid composition is applied to the surface of an electrode substrate having an opening on its surface, before the second liquid composition, such that a second liquid composition containing particles can be deposited on the surface; A first liquid composition solidification step for solidifying the first liquid composition applied to the surface, A second liquid composition deposition step involves applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. The process includes a heating step of heating the electrode substrate on which the second liquid composition is deposited, A method for producing an electrode, characterized in that the first liquid composition is a liquid compound that can be volatilized in the heating step.

2. A first liquid composition application step, in which a first liquid composition is applied to the surface of an electrode substrate having an opening on its surface, before the second liquid composition, such that a second liquid composition containing particles can be deposited on the surface, A first liquid composition solidification step for solidifying the first liquid composition applied to the surface, A second liquid composition deposition step involves applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. A method for manufacturing an electrode, characterized in that the solidification of the first liquid composition is carried out by cooling the first liquid composition.

3. A first liquid composition application step of applying a first liquid composition to the surface of an electrode substrate having an opening on its surface, such that a second liquid composition containing particles can be deposited on the surface before the second liquid composition, A first liquid composition solidification step for solidifying the first liquid composition applied to the surface, A second liquid composition deposition step involves applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. The first liquid composition application step is performed at a temperature of 25°C or higher. A method for manufacturing an electrode, characterized in that the first liquid composition solidification step is performed at a temperature of 0°C or higher and less than 25°C.

4. A first liquid composition application step of applying a first liquid composition to the surface of an electrode substrate having an opening on its surface, such that a second liquid composition containing particles can be deposited on the surface before the second liquid composition, A first liquid composition solidification step for solidifying the first liquid composition applied to the surface, A second liquid composition deposition step involves applying the second liquid composition to the surface so as to come into contact with the solidified first liquid composition, thereby depositing the second liquid composition on the surface. A method for manufacturing an electrode, characterized in that, in the first step of applying the liquid composition, the electrode substrate to which the first liquid composition is applied is at a temperature below the melting point of the first liquid composition.

5. The method for manufacturing an electrode according to any one of claims 1 to 4, wherein the arithmetic surface roughness of the surface of the electrode substrate is 0.1 μm or more and 5 μm or less.

6. The method for manufacturing an electrode according to any one of claims 1 to 5, wherein the surface layer of the electrode substrate is an electrode composite layer.

7. The method for manufacturing an electrode according to any one of claims 1 to 5, wherein the surface layer of the electrode substrate is a solid electrolyte layer.

8. The method for manufacturing an electrode according to any one of claims 1 to 5, wherein the surface layer of the electrode substrate is a separator.

9. The method for manufacturing an electrode according to any one of claims 1 to 8, wherein the melting point of the first liquid composition is 0°C or higher and 25°C or lower.

10. The method for manufacturing an electrode according to any one of claims 1 to 9, wherein the first liquid composition solidification step is performed under either dry air or a nitrogen atmosphere.

11. A method for manufacturing an electrode according to any one of claims 2 to 10, comprising a heating step of heating an electrode substrate on which the second liquid composition is deposited.

12. A method for producing an electrode according to claim 1 or 11, comprising heating at a temperature such that the vapor pressure of the dispersion medium contained in the second liquid composition and the vapor pressure of the liquid compound contained in the first liquid composition are equal to or less than atmospheric pressure.

13. A method for producing an electrode according to claim 1 or 11, comprising: heating the second liquid composition at a temperature such that the vapor pressure of the dispersion medium contained in the second liquid composition becomes equal to or equal to atmospheric pressure; and heating the first liquid composition at a temperature such that the vapor pressure of the liquid compound contained in the first liquid composition becomes equal to or equal to atmospheric pressure.

14. A first liquid composition containing a liquid compound, A second liquid composition containing particles and a dispersion medium, A liquid composition set for forming an insulating layer on the surface of an electrode substrate, characterized by satisfying either (1) or (2) below. (1) The cohesive energy density A1 (J / mol), which is the product of the molecular volume of the liquid compound in the first liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH), is greater than the cohesive energy density A2 (J / mol), which is the product of the molecular volume of the dispersion medium in the second liquid composition and the sum of the squares of each term of the Hansen solubility parameters (δD, δP, δH). (2) The absolute value of the difference (A1-A2) between the cohesive energy density A1 and the cohesive energy density A2 is 5,000 J / mol or less.

15. The liquid composition set according to claim 14, wherein the cohesive energy density A1 is 50,000 J / mol or more.

16. The liquid composition set according to any one of claims 14 to 15, wherein the viscosity of the first liquid composition at 25°C is 50 mPa·s or less.

17. The liquid composition set according to any one of claims 14 to 16, wherein the first liquid composition comprises one liquid compound.

18. The liquid composition set according to any one of claims 14 to 16, wherein the first liquid composition comprises a plurality of liquid compounds.

19. The liquid composition set according to any one of claims 14 to 18, wherein the particles are inorganic oxide particles.

20. The liquid composition set according to any one of claims 14 to 19, wherein the particles are alumina.

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