JP7613035B2 - Liquid composition set and method for producing electrochemical device - Google Patents

Description

The present invention relates to a liquid composition set and a method for manufacturing an electrochemical device.

Electrochemical elements such as lithium-ion secondary batteries, electric double-layer capacitors, lithium-ion capacitors, and redox capacitors are being installed in portable devices, hybrid cars, electric cars, etc., and demand is expanding. In addition, there is a growing need for thin batteries to be installed in various wearable devices and medical patches, and the requirements for electrochemical elements are becoming more diverse.

Conventionally, a method for manufacturing electrodes constituting an electrochemical element is known in which an electrode mixture layer is formed on an electrode substrate by applying an electrode material and a liquid composition for the electrode mixture layer, which contains a liquid, using a die coater, comma coater, reverse roll coater, or the like.

For example, the electrode mixture layer can be formed by screen printing the liquid composition for the electrode mixture layer onto the electrode substrate.

However, in order to screen print in a shape that meets the needs, a screen must be made for each need.

Therefore, a method of forming an electrode mixture layer by ejecting a liquid composition for the electrode mixture layer onto an electrode substrate using a liquid ejection device has been investigated (see, for example, Patent Documents 1 and 2).

For example, from the viewpoint of the drying efficiency of the liquid composition for the electrode mixture layer, it is possible to use a liquid with a low boiling point as the liquid contained in the liquid composition for the electrode mixture layer.

However, electrode materials (e.g., active materials, conductive additives, binders, electrolytes, etc.) that provide good characteristics for electrochemical elements do not always have good solubility or dispersibility in the liquid with the low boiling point.

In addition, from the viewpoint of the ejection characteristics of the liquid composition for the electrode mixture layer, it is also possible to use a liquid with a high boiling point as the liquid contained in the liquid composition for the electrode mixture layer.

Therefore, when designing a liquid composition for an electrode mixture layer that will have good electrochemical element characteristics and ejection characteristics, it is necessary to consider the electrochemical characteristics of the liquid and the electrochemical characteristics of the electrode material, as well as multiple other conditions such as the solubility and dispersibility of the electrode material in the liquid. For this reason, it is desirable to improve the degree of freedom in designing liquid compositions for electrode mixture layers.

The present invention aims to provide a liquid composition set that allows for a high degree of design freedom and can be used to form a positive electrode composite layer or a negative electrode composite layer that constitutes an electrochemical element.

One aspect of the present invention is a liquid composition set for forming a positive electrode composite layer or a negative electrode composite layer using a liquid ejection device , the liquid composition set comprising a first liquid composition in which a first electrode material is dissolved or dispersed in a first liquid, and a second liquid composition in which a second electrode material different from the first electrode material is dissolved or dispersed in a second liquid different from the first liquid, the first liquid composition and the second liquid composition both having a viscosity of 200 mPa·s or less at 25° C., and the second electrode material is more easily dissolved or dispersed in the second liquid than in the first liquid.

The present invention provides a liquid composition set that has a high degree of design freedom and can be used to form a positive electrode composite layer or a negative electrode composite layer that constitutes an electrochemical element.

FIG. 2 is a cross-sectional view showing an example of a negative electrode according to the present embodiment. 3A to 3C are schematic diagrams illustrating an example of a method for producing a negative electrode according to the present embodiment. 5A to 5C are schematic diagrams illustrating another example of the method for producing a negative electrode according to the present embodiment. 5A to 5C are diagrams illustrating another example of the method for producing the negative electrode according to the present embodiment. 5A to 5C are diagrams illustrating another example of the method for producing the negative electrode according to the present embodiment. 6 is a schematic diagram showing a modified example of the liquid ejection device of FIGS. FIG. 2 is a cross-sectional view showing an example of a positive electrode of the present embodiment. FIG. 2 is a cross-sectional view showing an example of an electrode element of the present embodiment. FIG. 1 is a cross-sectional view showing an example of an electrochemical element according to an embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to the drawings. Note that the same components are given the same reference numerals, and descriptions thereof may be omitted.

[Liquid composition set]
The liquid composition set of the present embodiment is used to form a positive electrode mixture layer or a negative electrode mixture layer.

The liquid composition set of this embodiment has a first liquid composition in which a first electrode material is dissolved or dispersed in a first liquid, and a second liquid composition in which a second electrode material different from the first electrode material is dissolved or dispersed in a second liquid different from the first liquid.

In this specification and claims, the term "liquid" refers to a liquid that functions as a medium for dissolving or dispersing the electrode material, and does not include a liquid that functions as a precursor of the binder (e.g., a monomer).

Here, the first electrode material can contain at least one of an active material, a conductive additive, a binder, and an electrolyte, and preferably contains a conductive additive. This improves the characteristics of the electrochemical element.

The second electrode material may include at least one of an active material, a conductive additive, a binder, and an electrolyte.

In the liquid composition set of this embodiment, the second electrode material is more easily dissolved or dispersed in the second liquid than in the first liquid.

As a result, the liquid composition set of this embodiment provides a liquid composition set with high design freedom and excellent electrochemical element characteristics and ejection characteristics.

The liquid composition set of this embodiment may contain at least one of the first liquid composition and the second liquid composition.

Here, "at least one of the first liquid composition and the second liquid composition" refers to only the first liquid composition, only the second liquid composition, or both the first liquid composition and the second liquid composition.

In addition, having at least one of the first liquid composition and the second liquid composition means having one type each of the first liquid composition and the second liquid composition, having two or more types of the first liquid composition and one type of the second liquid composition, having one type of the first liquid composition and two or more types of the second liquid composition, or having two or more types of both the first liquid composition and the second liquid composition.

In general, the conditions under which any of the electrode active material, conductive assistant, binder, and electrolyte constituting the electrode mixture layer dissolves or disperses well in a liquid may differ for each. Also, even if any of the electrode active material, conductive assistant, binder, and electrolyte constituting the electrode mixture layer dissolves or disperses well in the same liquid, when these are mixed together, they may no longer dissolve or disperse well.

If multiple types of electrode materials, including electrode active materials, conductive assistants, binders, and electrolytes, which are expected to have good characteristics for electrochemical elements, are dissolved or dispersed well in different liquids, it may be difficult to eject a liquid composition containing multiple types of these electrode materials.

Therefore, by having at least one of the first liquid composition and the second liquid composition, the design freedom of the liquid composition is improved.

When at least one of the first electrode material and the second electrode material contains an active material, the content of the active material in the liquid composition is preferably 20% by mass or more, and more preferably 25% by mass or more. When the content of the active material in the liquid composition is 20% by mass or more, the capacity of the electrochemical element is improved, and when it is 25% or more, the capacity of the electrochemical element is further improved.

The content of the active material in the liquid composition is preferably 60% by mass or less. If the content of the active material in the liquid composition is 60% by mass or less, the ejection properties of the liquid composition are improved.

It is preferable that the first liquid composition and the second liquid composition have a viscosity that allows them to be ejected from a liquid ejection head.

The viscosity of the liquid composition at 25°C is preferably 200 mPa·s or less. If the viscosity of the liquid composition at 25°C is 200 mPa·s or less, the ejection stability of the liquid composition is improved.

In this specification and claims, the electrode material being dissolved in a liquid means that the viscosity of the liquid composition at 25°C is 200 mPa·s or less.

Furthermore, the second electrode material being more soluble in the second liquid than the first liquid means that when the second liquid in the second liquid composition is replaced with the first liquid, the viscosity at 25°C increases or the second electrode material becomes insoluble in the first liquid.

It is preferable that the maximum particle diameter of the first electrode material and the second electrode material is smaller than the nozzle diameter of the liquid ejection head.

Here, the maximum particle size refers to the particle size at which the volumetric particle size distribution is 100%. The maximum particle size can be measured using a particle size distribution analyzer that uses the laser diffraction method.

The mode diameter of the first electrode material and the second electrode material is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. When the mode diameter of the first electrode material and the second electrode material is 20 μm or less, the ejection stability and sedimentation resistance of the first liquid composition and the second liquid composition are improved, when it is 10 μm or less, the ejection stability and sedimentation resistance of the first liquid composition and the second liquid composition are further improved, and when it is 3 μm or less, the ejection stability and sedimentation resistance of the first liquid composition and the second liquid composition are further improved.

Here, the mode diameter refers to the particle size that is the most frequent value in the particle size distribution. The mode diameter can be measured using a particle size distribution analyzer that uses the laser diffraction method.

In this specification and claims, the electrode material being dispersed in a liquid means that the mode diameter of the liquid composition is 3 μm or less.

Furthermore, the second electrode material being more easily dispersible in the second liquid than in the first liquid means that when the second liquid in the second liquid composition is replaced with the first liquid, the mode diameter increases or the second electrode material is no longer dispersible in the first liquid.

The 10% diameter (d10) of the first electrode material and the second electrode material is preferably 0.10 μm or more, and more preferably 0.15 μm or more. When the median diameter (d10) of the first electrode material and the second electrode material is 0.10 μm or more, the storage stability of the liquid composition is improved, and when it is 0.15 μm or more, the storage stability of the liquid composition is further improved.

The 10% diameter of the electrode material can be measured using a particle size distribution analyzer that uses the laser diffraction method.

<Active material>
As the active material, 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 in combination of two or more types.

There are no particular limitations on the positive electrode active material, so long as it is capable of absorbing or releasing alkali metal ions, but an alkali metal-containing transition metal compound can be used.

Here, "occlusion" refers to the insertion of alkali metal ions into the negative electrode active material. "release" refers to the desorption of alkali metal ions from the negative electrode active material.

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 cobalt oxide, lithium nickel oxide, and lithium manganese oxide.

As the alkali metal-containing transition metal compound, a polyanion-based compound having an _XO4 tetrahedron (X is P, S, As, Mo, W, Si, etc.) in the 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 output characteristics. In addition, the polyanion-based compound is preferably composited by being surface-coated with a conductive assistant such as a carbon material in terms of electronic conductivity.

There are no particular limitations on the negative electrode active material, so long as it is capable of absorbing or releasing alkali metal ions, but carbon materials containing graphite having a graphite-type crystal structure can be used.

Examples of carbon materials include natural graphite, artificial graphite, non-graphitizable carbon (hard carbon), and easily graphitizable carbon (soft carbon).

Examples of negative electrode active materials other than carbon materials include lithium titanate and titanium oxide.

In addition, from the viewpoint of the energy density of non-aqueous 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.

<Electrolytes>
As the electrolyte, a material for forming a solid electrolyte layer can be used. The material for forming the solid electrolyte layer is not particularly limited as long as it is a solid substance having electronic insulation and ion conductivity, but a sulfide-based solid electrolyte or an oxide-based solid electrolyte is preferable from the viewpoint of having high ion conductivity.

Examples of sulfide-based solid electrolytes include Li ₁₀ GeP ₂ S ₁₂ and Li ₆ PS ₅ X (X is F, Cl, Br, or I) having an argyrodite crystal structure.

Examples of oxide-based solid _electrolytes include LLZ ( _Li7La3Zr2O12 ) having a garnet-type crystal structure, LATP (Li1 _{+ xAlxTi20x} ( _PO4 ) ₃ ) ₍ 0.1≦x≦ _0.4 ) having a NASICON-type crystal structure _, LLT ( _{Li0.33La0.55TiO3 )} having _{a perovskite} -type crystal structure, and amorphous _LIPON ( _{Li2.9PO3.3N0.4} ).

These solid electrolytes may be used alone or in combination of two or more.

Examples of electrolyte materials that are dissolved or dispersed in liquid to form these solid electrolyte layers include solid electrolyte precursors such as Li ₂ S, P ₂ S ₅ , and LiCl, and solid electrolyte materials such as Li ₂ S-P ₂ S ₅ glass and Li ₇ P ₃ S ₁₁ glass ceramics.

Also, materials for forming a gel electrolyte layer can be used as the electrolyte.

There are no particular limitations on the gel electrolyte as long as it exhibits ionic conductivity. For example, polymers that make up the network structure of the gel electrolyte include polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, copolymers of vinylidene fluoride and propylene hexafluoride, and polyethylene carbonate.

In addition, examples of the solvent molecules held in the gel electrolyte include ionic liquids. Examples of ionic liquids include methyl-1-propylpyrrolidinium bis(fluorosulfonylimide), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonylimide), 1-methyl-1-propylpiperidinium bis(fluorosulfonylimide), 1-ethyl-3-methylimidazolium bis(fluorosulfonylimide), 1-methyl-3-propylimidazolium bis(fluorosulfonylimide), and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide.

Alternatively, a mixture of a lithium salt and a liquid such as tetraglyme, propylene carbonate, fluoroethylene carbonate, ethylene carbonate, or diethyl carbonate may be used.

The lithium salt is not particularly limited and can be appropriately selected depending on the purpose. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethasulfonate (LiCF ₃ SO ₃ ), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF ₃ SO ₂ ) ₂ ), and lithium bis(pentafluoroethylsulfonyl)imide (LiN(C ₂ F ₅ SO ₂ ) ₂ ).

These gel electrolytes may be used alone or in combination of two or more.

To form these gel electrolyte layers, the electrolyte material dissolved or dispersed in the liquid may be a solution in which the above-mentioned polymer compound and an ionic liquid or lithium salt are dissolved. In addition, the electrolyte material dissolved or dispersed in the liquid may be a material that serves as a precursor of the gel electrolyte (for example, a combination of polyethylene oxide or polypropylene oxide, both of which have acrylate groups at both ends, and a solution in which an ionic liquid or lithium salt is dissolved).

<Liquid>
The liquid is not particularly limited as long as it is capable of dispersing the positive electrode material or the negative electrode material, and examples of the liquid include water, ethylene glycol, propylene glycol, trimethylene glycol, N-methyl-2-pyrrolidone, 2-pyrrolidone, cyclohexanone, ethyl lactate, butyl acetate, mesitylene, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 2-n-butoxymethanol, 2-dimethylethanol, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, normal hexane, heptane, octane, nonane, decane, diethyl ether, dibutyl ether, di-tert-butyl ether, toluene, xylene, anisole, and mesitylene.

The liquids may be used alone or in combination of two or more.

<Conductive assistant>
As the conductive assistant, for example, conductive carbon black formed by a furnace method, an acetylene method, a gasification method, or the like, as well as carbon materials such as carbon nanofibers, carbon nanotubes, graphene, and graphite particles can be used.

Other conductive additives that can be used include, for example, metal particles such as aluminum, and metal fibers.

<Binder>
There are no particular limitations on the binder as long as it is capable of binding together negative electrode materials, between positive electrode materials, between a negative electrode material and a negative electrode substrate, and between a positive electrode material and a positive electrode substrate. However, from the viewpoint of preventing nozzle clogging of the liquid ejection head, it is preferable to use a material that does not increase the viscosity of the liquid composition.

As a material that does not increase the viscosity of the liquid composition, a polymeric compound that can be dissolved or dispersed in the liquid can be used.

When using a polymeric compound that can be dissolved in a liquid, the liquid composition in which the polymeric compound is dissolved in the liquid needs to have a viscosity that allows it to be ejected from a liquid ejection head.

Examples of polymer compounds include polyamide compounds, polyimide compounds, polyamideimide, ethylene-propylene-butadiene rubber (EPBR), styrene-butadiene rubber (SBR), nitrile butadiene rubber (HNBR), isoprene rubber, polyisobutene, polyethylene glycol (PEO), polymethyl methacrylic acid (PMMA), polyethylene vinyl acetate (PEVA), etc.

Polymer particles may be used as the polymer compound that can be dissolved in liquid.

The maximum particle diameter of the polymer particles must be smaller than the nozzle diameter of the liquid ejection head.

The mode diameter of the polymer particles is preferably 0.01 to 1 μm.

Examples of materials that make up polymer particles include thermoplastic resins such as polyvinylidene fluoride, acrylic resin, styrene-butadiene rubber, polyethylene, polypropylene, polyurethane, nylon, polytetrafluoroethylene, polyphenylene sulfide, polyethylene terephthalate, and polybutylene terephthalate.

The electrode material of this embodiment may also contain other electrode materials, such as binder precursors and dispersants, as long as the effects of the present invention are not impaired.

<Binder Precursor>
Examples of the binder precursor include polymerizable compounds such as monomers.

When a polymerizable compound is used, for example, a liquid composition in which the polymerizable compound is dissolved in a liquid is applied, and then the mixture is heated or irradiated with non-ionizing radiation, ionizing radiation, infrared radiation, or the like to polymerize and produce a binder.

There are no particular limitations on the polymerizable compound as long as it has a polymerizable group, but compounds that can be polymerized at 25°C are preferred.

By using a polymerizable compound, multiple pores can be formed inside the electrode mixture layer. In this case, it is preferable that the pores inside the electrode mixture layer are connected to other pores and spread three-dimensionally. By connecting the pores, the electrolyte can sufficiently penetrate into the electrode mixture layer, improving the ionic conductivity of the electrochemical element.

The polymerizable compound may be monofunctional or polyfunctional.

A polyfunctional polymerizable compound means a compound having two or more polymerizable groups.

There are no particular limitations on the polyfunctional polymerizable compound, so long as it can be polymerized by heating or by irradiation with non-ionizing radiation, ionizing radiation, or infrared radiation, and examples of such compounds include acrylate resins, methacrylate resins, urethane acrylate resins, vinyl ester resins, unsaturated polyesters, epoxy resins, oxetane resins, vinyl ethers, and resins that utilize ene-thiol reactions. Among these, from the viewpoint of productivity, acrylate resins, methacrylate resins, urethane acrylate resins, and vinyl ester resins are preferred.

Multifunctional acrylate resins can be used as Michael acceptors, allowing them to undergo polyaddition reactions with Michael donors.

Examples of polyfunctional acrylate resins include bifunctional acrylates such as low molecular weight compounds such as dipropylene glycol diacrylate and neopentyl glycol diacrylate, and high molecular weight compounds such as polyethylene glycol diacrylate, urethane acrylate, and epoxy acrylate; trifunctional acrylates such as trimethylolpropane triacrylate and pentaerythritol triacrylate; and tetrafunctional or higher acrylates such as pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate.

Examples of Michael donors include polyfunctional amines and polyfunctional thiols.

Examples of polyfunctional amines include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine.

Examples of polyfunctional thiols include 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 1,3,5-benzenetrithiol, and 4,4-biphenyldithiol.

Catalysts for the polyaddition reaction can be appropriately selected from those typically used in Michael addition reactions, and examples include amine catalysts such as diazabicycloundecene (DBU) and N-methyldicyclohexylamine, base catalysts such as sodium methoxide, sodium ethoxide, potassium t-butoxide, sodium hydroxide, and tetramethylammonium hydroxide, metallic sodium, and butyllithium.

Examples of polymerizable compounds capable of addition polymerization (radical polymerization) include esters in which the double bonds of terpenes having unsaturated bonds, such as myrcene, carene, ocimene, pinene, limonene, camphene, terpinolene, tricyclene, terpinene, fenchene, phellandrene, sylvestrene, sabinene, dipentene, bornene, isopulegol, and carvone, are epoxidized and acrylic acid or methacrylic acid is added; citronellol, pinocampheol, geraniol, and fenchyl. Alcohol, nerol, borneol, linalool, menthol, terpineol, thuyl alcohol, citronellal, ionone, iron, cinerol, citral, pinol, cyclocitral, carbomenthone, ascaridole, safranal, piperitol, menthenomonool, dihydrocarvone, carveol, sclareol, manol, hinokiol, ferruginol, totarol, sugiol, farnesol, patchouli alcohol, nerolidol, carotol, cajillool Esters of alcohols derived from terpenes such as nol, lantheol, eudesmol, and phytol with acrylic or methacrylic acid; citronellic acid, hinoki acid, and santalic acid; menthone, carbotanetone, ferrandrale, pimelitenone, perillaldehyde, thujone, calone, dagetone, camphor, bisabolene, santalene, zingiberene, caryophyllene, curcumene, cedrene, cadinene, longifolene, sesquibenihen, cedrol, guayol, kessoglycol, and cyperone. , eremophilone, zerumbone, campholene, podocarpulene, milene, phyllocladene, totarene, ketomanoyl oxide, manoyl oxide, abietic acid, pimaric acid, neoabietic acid, levopimaric acid, iso-d-pimaric acid, agathene dicarboxylic acid, rubenic acid, carotenoids, peraryaldehyde, piperitone, ascaridole, pimene, fencene, sesquiterpenes, diterpenes, triterpenes, etc., are included as acrylates or methacrylates having a skeleton in the side chain.

As the polymerization initiator, for example, a photopolymerization initiator or a thermal polymerization initiator can be used.

A photoradical generator can be used as the photopolymerization initiator.

Examples of the photoradical generator include α-hydroxyacetophenone, α-aminoacetophenone, 4-aroyl-1,3-dioxolane, benzil ketal, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bis(diethylamino)benzophenone, Michler's ketone, benzil, benzoin, benzil dimethyl ketal, tetramethylthiuram monosulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, azobisisobutyronitrile, benzoin peroxide, di-tert-butyl peroxide, (1-hydroxy cyclohexyl)phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, methyl benzoyl formate, benzoin isopropyl ether, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzoin n-propyl ether and other benzoin alkyl ethers, (1-hydroxycyclohexyl)phenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1, (1-hydroxycyclohexyl)phenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, bis(η ⁵ -2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one (Darocur 1173), bis(2,6-dimethoxybenzoyl) 4-(2-hydroxyethoxy)phenyl-2-hydroxy-2-methyl-1-propan-1-one, monoacylphosphine oxide, diacylphosphine oxide, titanocene, fluorescene, anthraquinone, thioxanthone, xanthone, lophine dimer, trihalomethyl compounds, dihalomethyl compounds, active ester compounds, and organic boron compounds.

In addition, a photocrosslinking radical generator such as a bisazide compound such as 2,2'-azobis(2,4-dimethylvaleronitrile) may be used in combination with the photoradical generator.

Examples of thermal polymerization initiators include azobisisobutyronitrile (AIBN).

A photoacid generator may be used as the polymerization initiator. In this case, when the applied liquid composition is irradiated with light, the photoacid generator generates acid, and the polymerizable compound polymerizes.

Examples of polymerizable compounds that polymerize in the presence of an acid include compounds having a cyclic ether group such as an epoxy group, an oxetane group, or an oxolane group, acrylic or vinyl compounds having the above-mentioned cyclic ether group in the side chain, carbonate compounds, low molecular weight melamine compounds, vinyl ethers, vinyl carbazoles, styrene derivatives, α-methylstyrene derivatives, and vinyl alcohol esters such as ester compounds of vinyl alcohol with acrylic acid, methacrylic acid, etc., and monomers having a vinyl group capable of cationic polymerization.

Examples of photoacid generators include onium salts, diazonium salts, quinone diazides, organic halides, aromatic sulfonates, disulfone compounds, sulfonyl compounds, sulfonates, sulfonium salts, sulfamides, iodonium salts, and sulfonyldiazomethane compounds. Among these, onium salts are preferred.

Examples of onium salts include diazonium salts, phosphonium salts, and sulfonium salts with a counter ion of fluoroborate ion, hexafluoroantimonate ion, hexafluoroarsenate ion, trifluoromethanesulfonate ion, or p-toluenesulfonate ion.

Other photoacid generators that can be used include halogenated triazines.

The photoacid generator may be used alone or in combination of two or more kinds. When using a photoacid generator, a sensitizing dye may be used in combination.

Sensitizing dyes include, for example, acridine, benzoflavin, perylene, anthracene, laser dyes, etc.

<Dispersant>
The liquid composition may further comprise a dispersant.

There are no particular limitations on the dispersant, so long as it is capable of improving the dispersibility of the electrode material in the liquid. Examples include polymeric dispersants such as polycarboxylic acid-based, naphthalenesulfonic acid-formaldehyde condensation-based, polyethylene glycol, polycarboxylic acid partial alkyl ester-based, polyether-based, and polyalkylene polyamine-based dispersants, low molecular weight dispersants such as alkylsulfonic acid-based, quaternary ammonium-based, higher alcohol alkylene oxide-based, polyhydric alcohol ester-based, and alkyl polyamine-based dispersants, and inorganic dispersants such as polyphosphate-based dispersants.

[Method of manufacturing electrochemical device]
The method for producing an electrochemical device of this embodiment includes a step of applying the liquid composition set of this embodiment onto an electrode substrate to form an electrode mixture layer.

Here, examples of the method for applying the liquid composition set onto the electrode substrate include a method in which the liquid compositions constituting the liquid composition set are applied sequentially onto the electrode substrate, and a method in which the liquid compositions constituting the liquid composition set are applied onto the electrode substrate approximately simultaneously.

The method for applying the liquid composition is not particularly limited, and examples thereof include spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, slit coating, capillary coating, spray coating, nozzle coating, gravure printing, screen printing, flexographic printing, offset printing, reverse printing, and liquid ejection methods. Among these, the liquid ejection method is particularly preferred in terms of electrode productivity.

When the liquid composition contains a polymerizable compound, the liquid composition is applied onto the electrode substrate, and then heated or irradiated with non-ionizing radiation, ionizing radiation, infrared radiation, or the like, to polymerize the polymerizable compound and produce the binder.

There are no particular limitations on the material that constitutes the electrode substrate (current collector), so long as it is conductive and stable with respect to the applied potential.

<Negative Electrode>
FIG. 1 shows an example of the negative electrode of this embodiment.

The negative electrode 10 has a negative electrode composite layer 12 formed on one side of the negative electrode substrate 11.

The negative electrode composite layer 12 may be formed on both sides of the negative electrode substrate 11.

The shape of the negative electrode 10 is not particularly limited, and may be, for example, a flat plate shape.

Examples of materials that can be used to form the negative electrode substrate 11 include stainless steel, nickel, aluminum, copper, etc.

<Method of Manufacturing Negative Electrode>
FIG. 2 shows an example of a method for producing the negative electrode of this embodiment.

The method for manufacturing the negative electrode 10 includes the steps of sequentially discharging a first liquid composition 12A and a second liquid composition 12B onto the negative electrode substrate 11 using liquid discharging devices 300A and 300B.

Here, the liquid composition contains a negative electrode material, and the negative electrode material contains a negative electrode active material, a conductive assistant, and a binder or a binder precursor.

Liquid composition 12A is stored in tank 307A and is supplied from tank 307A to liquid ejection head 306A via tube 308A. Similarly, liquid composition 12B is stored in tank 307B and is supplied from tank 307B to liquid ejection head 306B via tube 308B.

The number of liquid ejection devices is not limited to two and may be three or more.

The liquid ejection device 300A (or 300B) may also be provided with a mechanism for capping the nozzle to prevent drying when the liquid composition 12A (or 12B) is not being ejected from the liquid ejection head 306A (or 306B).

When manufacturing the negative electrode 10, the negative electrode substrate 11 is placed on a heatable stage 400, and then droplets of the first liquid composition 12A and the second liquid composition 12B are ejected from the liquid ejection heads 306A and 306B, respectively, onto the negative electrode substrate 11. At this time, the stage 400 may move, or the liquid ejection heads 306A and 306B may move.

When heating the liquid composition 12A dispensed onto the negative electrode substrate 11, it may be heated by the stage 400, or it may be heated by a heating mechanism other than the stage 400.

There are no particular limitations on the heating mechanism, so long as it does not come into direct contact with the first liquid composition 12A and the second liquid composition 12B, and examples of the heating mechanism include a resistance heater, an infrared heater, a fan heater, etc.

Note that multiple heating mechanisms may be installed.

An ultraviolet curing device may also be installed to polymerize the polymerizable compound.

There are no particular limitations on the heating temperature as long as it is a temperature at which the polymerizable compound polymerizes, and from the viewpoint of energy usage, it is preferable that the heating temperature is in the range of 70 to 150°C.

In addition, when heating the liquid composition 12A dispensed onto the negative electrode substrate 11, ultraviolet light may be irradiated.

In the method for manufacturing the negative electrode according to this embodiment, a negative electrode composite layer 12 is formed on the negative electrode substrate 11, and a negative electrode 10 is obtained.

Figure 3 shows another example of the method for manufacturing the negative electrode of this embodiment.

The method for manufacturing the negative electrode 10 includes a step of sequentially discharging a first liquid composition 12A and a second liquid composition 12B onto the negative electrode substrate 11 using a liquid discharging device 300C.

Liquid composition 12A is stored in tank 307A and is supplied from tank 307A to liquid ejection head 306C via tube 308A. Similarly, liquid composition 12B is stored in tank 307B and is supplied from tank 307B to liquid ejection head 306C via tube 308B.

When manufacturing the negative electrode 10, the negative electrode substrate 11 is placed on a heatable stage 400, and then droplets of the first liquid composition 12A and the second liquid composition 12B are ejected from the liquid ejection head 306C onto the negative electrode substrate 11 in sequence.

Figure 4 shows another example of the method for manufacturing the negative electrode of this embodiment.

The method for manufacturing the negative electrode 10 includes the steps of sequentially discharging a first liquid composition 12A and a second liquid composition 12B onto the negative electrode substrate 11 using liquid discharging devices 300A and 300B.

First, prepare an elongated negative electrode substrate 11. Then, the negative electrode substrate 11 is wound around a cylindrical core, and set on the feed roller 304 and the take-up roller 305 so that the side on which the negative electrode composite layer 12 is formed is the upper side in the figure. Here, the feed roller 304 and the take-up roller 305 rotate counterclockwise, and the negative electrode substrate 11 is transported from right to left in the figure. Then, droplets of the first liquid composition 12A and the second liquid composition 12B are sequentially ejected onto the negative electrode substrate 11 being transported from the liquid ejection heads 306A and 306B installed above the negative electrode substrate 11 between the feed roller 304 and the take-up roller 305 in the same manner as in FIG. 2. The droplets of the first liquid composition 12A and the droplets of the second liquid composition 12B are ejected so as to cover at least a part of the negative electrode substrate 11.

In addition, multiple liquid ejection heads 306A and 306B may be installed in a direction approximately parallel to or approximately perpendicular to the transport direction of the negative electrode substrate 11.

Also, similar to FIG. 3, liquid ejection device 300C may be installed instead of liquid ejection devices 300A and 300B (see FIG. 5).

Next, the negative electrode substrate 11 onto which the droplets of the first liquid composition 12A and the droplets of the second liquid composition 12B have been ejected is transported to the heating mechanism 309 by the delivery roller 304 and the take-up roller 305. As a result, the first liquid composition 12A and the second liquid composition 12B on the negative electrode substrate 11 are dried to form the negative electrode composite layer 12, and the negative electrode 10 is obtained. The negative electrode 10 is then cut to the desired size by punching or the like.

The heating mechanism 309 is not particularly limited as long as it does not come into direct contact with the first liquid composition 12A and the second liquid composition 12B, and examples of the heating mechanism include a resistance heater, an infrared heater, a fan heater, etc.

The heating mechanism 309 may be installed either above or below the negative electrode substrate 11, or multiple heating mechanisms may be installed.

There are no particular limitations on the heating temperature as long as it is a temperature at which the polymerizable compound polymerizes, and from the viewpoint of energy usage, it is preferable that the heating temperature is in the range of 70 to 150°C.

In addition, when heating the liquid composition 12A dispensed onto the negative electrode substrate 11, ultraviolet light may be irradiated.

Figure 6 shows modified examples of liquid ejection devices 300A and 300B.

Liquid ejection device 300A' can circulate first liquid composition 12A through liquid ejection head 306A, tank 307A, and tube 308A by controlling pump 310A and valves 311A and 312A. Similarly, liquid ejection device 300B' can circulate second liquid composition 12B through liquid ejection head 306B, tank 307B, and tube 308B by controlling pump 310B and valves 311B and 312B.

The liquid ejection device 300A' is also provided with an external tank 313A, and when the first liquid composition 12A in the tank 307A decreases, the pump 310A and the valves 311A, 312A, and 314A can be controlled to supply the first liquid composition 12A from the external tank 313A to the tank 307A. Similarly, the liquid ejection device 300B' is also provided with an external tank 313B, and when the second liquid composition 12B in the tank 307B decreases, the pump 310B and the valves 311B, 312B, and 314B can be controlled to supply the second liquid composition 12B from the external tank 313B to the tank 307B.

By using a liquid ejection device, the first liquid composition 12A and the second liquid composition 12B can be ejected onto the targeted area of the negative electrode substrate 11 (the area of the negative electrode substrate 11 where the negative electrode composite layer 12 is to be formed). In addition, by using a liquid ejection device, the contacting surfaces of the negative electrode substrate 11 and the negative electrode composite layer 12 can be bonded together. Furthermore, by using a liquid ejection device, the thickness of the negative electrode composite layer 12 can be made uniform.

<Positive electrode>
FIG. 7 shows an example of the positive electrode of this embodiment.

The positive electrode 20 has a positive electrode composite layer 22 formed on one side of the positive electrode substrate 21.

The positive electrode composite layer 22 may be formed on both sides of the positive electrode substrate 21.

The shape of the positive electrode 20 is not particularly limited, and may be, for example, flat.

Examples of materials that can be used to form the positive electrode substrate 21 include stainless steel, aluminum, titanium, and tantalum.

<Method of manufacturing positive electrode>
The method of manufacturing the positive electrode 20 is the same as the method of manufacturing the negative electrode 10 , except that the positive electrode mixture layer 22 is formed on the positive electrode substrate 21 .

Here, the liquid composition contains a positive electrode material, and the positive electrode material contains a positive electrode active material, a conductive assistant, and a binder or a binder precursor.

<Electrode element>
FIG. 8 shows an example of an electrode element used in the electrochemical device of this embodiment.

The electrode element 40 is formed by stacking a negative electrode 15 and a positive electrode 25 with a separator 30 in between. Here, the positive electrode 25 is stacked on both sides of the negative electrode 15. In addition, a lead wire 41 is connected to the negative electrode substrate 11, and a lead wire 42 is connected to the positive electrode substrate 21.

The negative electrode 15 is similar to the negative electrode 10, except that a negative electrode composite layer 12 is formed on both sides of the negative electrode substrate 11.

The positive electrode 25 is similar to the positive electrode 20, except that a positive electrode composite layer 22 is formed on both sides of the positive electrode substrate 21.

There is no particular limit to the number of layers of the negative electrodes 15 and positive electrodes 25 of the electrode element 40.

In addition, the number of negative electrodes 15 and the number of positive electrodes 25 in the electrode element 40 may be the same or different.

<Separator>
The separator 30 is provided between the negative electrode 15 and the positive electrode 25 as necessary to prevent a short circuit between the negative electrode 15 and the positive electrode 25 .

Examples of the separator 30 include paper such as kraft paper, vinylon-mixed paper, and synthetic pulp-mixed paper, cellophane, polyethylene graft membrane, polyolefin nonwoven fabric such as polypropylene melt-blown nonwoven fabric, polyamide nonwoven fabric, glass fiber nonwoven fabric, and micropore membrane.

There are no particular limitations on the size of the separator 30, as long as it can be used in an electrochemical element.

The separator 30 may be a single-layer structure or a laminated structure.

If a solid electrolyte is used, the separator 30 can be omitted.

<Electrochemical element>
FIG. 9 shows an example of the electrochemical device of this embodiment.

The electrochemical element 1 has an electrolyte layer 51 formed by injecting an aqueous electrolyte solution or a non-aqueous electrolyte into the electrode element 40 shown in FIG. 8, and is sealed with an exterior 52. In the electrochemical element 1, the leads 41 and 42 are drawn out to the outside of the exterior 52.

The electrochemical element 1 may have other components as necessary.

The electrochemical element 1 is not particularly limited, and examples include an aqueous storage element and a non-aqueous storage element.

The shape of the electrochemical element 1 is not particularly limited, and examples include a laminate type, a cylinder type in which a sheet electrode and a separator are spirally wound, a cylinder type with an inside-out structure that combines a pellet electrode and a separator, and a coin type in which a pellet electrode and a separator are stacked.

<Electrolyte aqueous solution>
Examples of electrolyte salts constituting the aqueous electrolyte solution include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, ammonium chloride, zinc chloride, zinc acetate, zinc bromide, zinc iodide, zinc tartrate, and zinc perchlorate.

<Non-aqueous electrolyte>
As the non-aqueous electrolyte, a solid electrolyte or a non-aqueous electrolyte solution can be used.

Here, a non-aqueous electrolyte is an electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent.

<Non-aqueous solvent>
The non-aqueous solvent is not particularly limited, and it is preferable to use, for example, an aprotic organic solvent.

As the aprotic organic solvent, a carbonate-based organic solvent such as a chain carbonate or a cyclic carbonate can be used. Among these, a chain carbonate is preferred because of its high dissolving power for electrolyte salts.

In addition, it is preferable that the aprotic organic solvent has a low viscosity.

Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

The content of the chain carbonate in the non-aqueous solvent is preferably 50% by mass or more. When the content of the chain carbonate in the non-aqueous solvent is 50% by mass or more, the content of the cyclic substance is low even if the non-aqueous solvent other than the chain carbonate is a cyclic substance with a high dielectric constant (e.g., a cyclic carbonate or a cyclic ester). Therefore, even if a non-aqueous electrolyte solution with a high concentration of 2M or more is prepared, the viscosity of the non-aqueous electrolyte solution is low, and the non-aqueous electrolyte solution penetrates the electrodes and the ions diffuse well.

Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), etc.

As non-aqueous solvents other than carbonate-based organic solvents, for example, ester-based organic solvents such as cyclic esters and chain esters, and ether-based organic solvents such as cyclic ethers and chain ethers can be used.

Examples of cyclic esters include γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.

Examples of chain esters include alkyl propionates, dialkyl malonates, alkyl acetates (e.g., methyl acetate (MA), ethyl acetate), and alkyl formates (e.g., methyl formate (MF), ethyl formate).

Examples of cyclic ethers include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, and 1,4-dioxolane.

Examples of chain ethers include 1,2-dimethoxyethane (DME), diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.

<Electrolyte Salt>
There are no particular limitations on the electrolyte salt, so long as it has high ionic conductivity and is soluble in a non-aqueous solvent.

The electrolyte salt preferably contains a halogen atom.

Examples of cations that make up the electrolyte salt include lithium ions.

Examples of anions constituting the electrolyte salt include BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ^{− ,} and the like.

The lithium salt is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethasulfonate (LiCF ₃ SO ₃ ), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF ₃ SO ₂ ) ₂ ), lithium bis(pentafluoroethylsulfonyl)imide (LiN(C ₂ F ₅ SO ₂ ) ₂ ), etc. Among these, LiPF ₆ is preferred from the viewpoint of ionic conductivity, and LiBF ₄ is preferred from the viewpoint of stability.

The electrolyte salts may be used alone or in combination of two or more.

The concentration of the electrolyte salt in the non-aqueous electrolyte can be selected appropriately depending on the purpose, but if the non-aqueous storage element is a swing type, it is preferably 1 mol/L to 2 mol/L, and if the non-aqueous storage element is a reserve type, it is preferably 2 mol/L to 4 mol/L.

<Applications of electrochemical elements>
Applications of electrochemical elements are not particularly limited, and examples thereof include notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video movie machines, liquid crystal televisions, handheld cleaners, portable CDs, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power sources, motors, lighting equipment, toys, game devices, clocks, strobes, cameras, and the like.

Below, examples of the present invention are described, but the present invention is not limited to these examples. Note that in the examples of the present invention, applications in which the electrode material is a positive electrode active material or a negative electrode active material are described, but the same applies to applications in which the electrode material is an electrode material other than a positive electrode active material or a negative electrode active material.

[Particle size distribution of liquid composition]
The liquid composition was dispersed in water or an organic solvent, and the particle size distribution of the liquid composition was measured at 25° C. using a laser diffraction particle size distribution analyzer Mastersizer 3000 (manufactured by Malvern Instruments).

[Viscosity of liquid composition]
The viscosity of the liquid composition at 100 rpm was measured at 25° C. using a Brookfield viscometer (cone-plate viscometer) equipped with a No. CPA-40Z rotor.

[Peel strength of electrode mixture layer]
The peel strength of the electrode mixture layer was measured using an adhesive/film peeling analyzer VPA-3 (manufactured by Kyowa Interface Science Co., Ltd.) (peel strength test method). Specifically, the electrode was cut into a width of 1.8 cm x length of 10 cm, and cellophane tape was attached to the surface of the electrode mixture layer side of the test piece. The cellophane tape was then peeled off 100 mm from one end of the test piece under the conditions of a peel speed of 30 mm/min and a peel angle of 90°, and the stress at that time was measured. Such stress measurement was performed 10 times, and the weighted average of the stress was calculated to be the peel strength of the electrode mixture layer.

[Capacity of positive electrodes A to F, A']
The positive electrode was punched out into a round shape with a diameter of 16 mm, and then the positive electrode, a 100 μm-thick glass separator (manufactured by Advantec Corporation), nonaqueous electrolyte 1, and a 200 μm-thick lithium counter electrode (manufactured by Honjo Metals Co., Ltd.) were placed in a coin can to obtain a nonaqueous storage element.

The nonaqueous storage element was subjected to initial charge and discharge at room temperature (25° C.) by constant current charging at 0.1 mA/cm ² to a charge cut-off voltage of 4.2 V, and then constant current discharging at 0.1 mA/cm ² to 2.5 V. Next, the nonaqueous storage element was subjected to two charge-discharge cycles of constant current charging at 0.1 mA/cm ² to 4.2 V, and then constant current discharging at 0.1 mA/cm ² to 3.0 V, and the capacity per unit area of the positive electrode was measured.

The capacity per unit area of the electrode was measured using a charge/discharge measuring device TOSCAT3001 (manufactured by Toyo Systems Co., Ltd.).

[Capacity of Negative Electrode A]
The negative electrode was punched out into a round shape with a diameter of 16 mm, and then the negative electrode, a 100 μm-thick glass separator (manufactured by Advantec Corporation), nonaqueous electrolyte 1, and a 200 μm-thick lithium counter electrode (manufactured by Honjo Metals Co., Ltd.) were placed in a coin can to prepare a nonaqueous storage element.

The nonaqueous storage element was subjected to initial charge and discharge at room temperature (25° C.) by constant current charging at 0.1 mA/cm ² to a charge cut-off voltage of 1.0 V, followed by constant current discharging at 0.1 mA/cm ² to 2.0 V. Next, the nonaqueous storage element was subjected to two constant current discharge cycles of constant current charging at 0.1 mA/cm ² to 1.0 V, followed by constant current discharging at 0.1 mA/cm ² to 2.0 V, and the capacity per unit area of the negative electrode was measured.

[Capacity of Negative Electrode B]
The negative electrode was punched out into a round shape with a diameter of 16 mm, and then the negative electrode, a 100 μm-thick glass separator (manufactured by Advantec Corporation), nonaqueous electrolyte 1, and a 200 μm-thick lithium counter electrode (manufactured by Honjo Metals Co., Ltd.) were placed in a coin can to prepare a nonaqueous storage element.

The nonaqueous storage element was initially charged and discharged at a constant current of 0.4 mA/ ^cm2 at room temperature (25°C) up to a charge cut-off voltage of 0.2 V, and then discharged at a constant current of 0.4 mA/ ^cm2 down to 2.0 V. Next, the nonaqueous storage element was subjected to two constant current discharge cycles of constant current charging at 0.1 mA/ ^cm2 up to 0.2 V, and then constant current discharging at 0.4 mA/ ^cm2 down to 2.0 V, and the capacity per unit area of the negative electrode was measured.

[Positive electrode active material 1]
Vanadium pentoxide, lithium hydroxide, phosphoric acid, sucrose, and water were mixed to generate a precipitate, which was then pulverized to obtain a precursor of vanadium phosphate particles. Next, the precursor of vanadium phosphate was fired at 900° C. under a nitrogen atmosphere to obtain lithium vanadium phosphate (LVP) having a carbon content of 3% by mass. The LVP had a mode diameter of 10 μm. Furthermore, the LVP was crushed using a jet mill to obtain a positive electrode active material 1. The positive electrode active material 1 had a mode diameter of 0.7 μm and a capacity per unit area of 0.26 mAh/cm ² .

[Positive electrode active material 2]
A nickel-based positive electrode active material (NCA) (manufactured by JFE Mineral Co., Ltd.) was crushed using a jet mill to obtain a positive electrode active material 2. The positive electrode active material 2 had a mode diameter of 1.5 μm and a capacity per unit area of 0.35 mAh/cm ² .

[Positive electrode active material 3]
Lithium cobalt oxide (LCO) (manufactured by Toshima Manufacturing Co., Ltd.) was crushed using a bead mill to obtain a positive electrode active material 3. The positive electrode active material 3 had a mode diameter of 1.3 μm and a capacity per unit area of 0.23 mAh/cm ² .

[Positive electrode active material 4]
Lithium manganese oxide (LMO) (manufactured by Toshima Manufacturing Co., Ltd.) was crushed using a bead mill to obtain a positive electrode active material 4. The positive electrode active material 4 had a mode diameter of 1.3 μm and a capacity per unit area of 0.31 mAh/cm ² .

[Positive electrode active material 5]
Lithium iron phosphate (LFP) (manufactured by TATUNG FINE CHEMICALS) was crushed using a bead mill to obtain a positive electrode active material 5. The positive electrode active material 5 had a mode diameter of 1.0 μm and a capacity per unit area of 0.33 mAh/cm ² .

[Positive electrode active material 6]
A nickel-based positive electrode active material (NCA) (manufactured by JFE Mineral Co., Ltd.) was crushed using a bead mill to obtain a positive electrode active material 6. The positive electrode active material 6 had a mode diameter of 9.6 μm and a capacity per unit area of 0.35 mAh/cm ² .

[Negative electrode active material 1]
Lithium titanate (LTO) (manufactured by Ishihara Sangyo Kaisha) was crushed using a bead mill to obtain a negative electrode active material 1. The negative electrode active material 1 had a mode diameter of 2.0 μm and a capacity per unit area of 0.31 mAh/cm ² .

[Negative electrode active material 2]
Silicon monoxide (SiO) (manufactured by Osaka Titanium Co., Ltd.) was crushed using a bead mill to obtain a negative electrode active material 2. The negative electrode active material 2 had a mode diameter of 1.0 μm and a capacity per unit area of 2.0 mAh/cm ² .

Table 1 shows the evaluation results of the mode diameter (μm) of the active material and the capacity per unit area.

[Non-aqueous electrolyte 1]
LiPF ₆ was dissolved in a mixed solvent of propylene ethylene carbonate (PC) / diethyl carbonate (DEC) / ethyl methyl carbonate (EMC) in a mass ratio of 1:1:1 so as to have a concentration of 1.0 mol/L, to prepare nonaqueous electrolyte solution 1 (20 mL).

Example 1
Positive electrode active material 1 (30 mass%) as a positive electrode active material, carbon black (3 mass%) as a conductive assistant, and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67 mass%) were mixed to prepare a first liquid composition, Liquid Composition A. Liquid Composition A had a viscosity of 10.3 mPa·s and a mode diameter of 1.58 μm.

Polyamideimide (3% by mass) as a binder and N-methylpyrrolidone (NMP) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (97% by mass) were mixed to prepare liquid composition B as a second liquid composition. Liquid composition B had polyamideimide dissolved in N-methylpyrrolidone (NMP) and had a viscosity of 9.6 mPa·s.

When polyamideimide (3% by mass) and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (97%) were mixed to prepare a liquid composition, the liquid composition became cloudy and precipitates were formed. In other words, polyamideimide, which is the second electrode material, is more easily dissolved in N-methylpyrrolidone, which is the second liquid, than ethyl lactate, which is the first liquid.

Using a liquid ejection device EV2500, the liquid compositions A and B were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode A. At this time, the aluminum foil was fixed on a hot plate and heated to 130° C. The liquid compositions A and B had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.0 mg/cm ² could be formed, and the liquid compositions A and B had good ejection efficiency.

Positive electrode A had a peel strength of the positive electrode mixture of 1.05 N and a capacity per unit area of 0.26 mAh/cm ² .

Example 2
A positive electrode A was obtained in the same manner as in Example 1, except that the liquid compositions A and B were discharged onto an aluminum foil as shown in FIG. 3 using a liquid discharger EV2500. The liquid compositions A and B had good discharge stability and no discharge failure occurred. As a result, a positive electrode composite layer with an active material amount per unit area of 1.9 mg/ ^cm2 could be formed, and the liquid compositions A and B had good discharge efficiency.

Positive electrode A had a peel strength of the positive electrode mixture of 1.09 N and a capacity per unit area of 0.25 mAh/cm ² .

Example 3
A positive electrode A was obtained in the same manner as in Example 1, except that the liquid compositions A and B were discharged onto an aluminum foil as shown in FIG. 4 using a liquid discharger EV2500. The liquid compositions A and B had good discharge stability and no discharge failure occurred. As a result, a positive electrode composite layer with an active material amount per unit area of 1.9 mg/ ^cm2 could be formed, and the liquid compositions A and B had good discharge efficiency.

Positive electrode A had a peel strength of the positive electrode mixture of 1.11 N and a capacity per unit area of 0.25 mAh/cm ² .

Example 4
A positive electrode A was obtained in the same manner as in Example 1, except that the liquid compositions A and B were discharged onto an aluminum foil using a liquid discharger EV2500 as shown in FIG. The liquid compositions A and B had good discharge stability and no discharge failure occurred. As a result, a positive electrode composite layer with an active material amount per unit area of 2.1 mg/ ^cm2 could be formed, and the liquid compositions A and B had good discharge efficiency.

The positive electrode A had a peel strength of the positive electrode mixture of 1.08 N and a capacity per unit area of 0.27 mAh/cm ² .

Example 5
Positive electrode active material 2 (30% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67% by mass) were mixed to prepare a first liquid composition, Liquid Composition C. Liquid Composition C had a viscosity of 10.3 mPa·s and a mode diameter of 2.52 μm.

Polyamideimide (3% by mass) and N,N-dimethylacetamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (97% by mass) were mixed to prepare liquid composition D as the second liquid composition. In liquid composition D, polyamideimide was dissolved in N,N-dimethylacetamide, and the viscosity was 9.6 mPa·s.

When polyamideimide (3% by mass) and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (97%) were mixed to prepare a liquid composition, the liquid composition became cloudy and precipitates were formed. In other words, polyamideimide, which is the second electrode material, is more easily dissolved in N,N-dimethylacetamide, which is the second liquid, than ethyl lactate, which is the first liquid.

Using a liquid ejection device EV2500, the liquid compositions C and D were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode B. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid compositions C and D had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.2 mg/cm ² could be formed, and the liquid compositions C and D had good ejection efficiency.

Positive electrode B had a peel strength of the positive electrode mixture of 1.14 N and a capacity per unit area of 0.36 mAh/cm ² .

Example 6
Positive electrode active material 3 (30% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67% by mass) were mixed to prepare a first liquid composition, Liquid Composition E. Liquid Composition E had a viscosity of 10.7 mPa·s and a mode diameter of 1.22 μm.

Using a liquid ejection device EV2500, the liquid compositions E and D were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode C. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid compositions E and D had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.0 mg/cm ² could be formed, and the liquid compositions E and D had good ejection efficiency.

For positive electrode C, the peel strength of the positive electrode mixture was 1.05 N and the capacity per unit area was 0.23 mAh/cm ² .

(Example 7)
Positive electrode active material 4 (30% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67% by mass) were mixed to prepare a first liquid composition, Liquid Composition F. Liquid Composition F had a viscosity of 11.1 mPa·s and a mode diameter of 1.48 μm.

Using a liquid ejection device EV2500, the liquid compositions F and D were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode D. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid compositions F and D had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.0 mg/cm ² could be formed, and the liquid compositions F and D had good ejection efficiency.

Positive electrode D had a peel strength of the positive electrode mixture of 1.08 N and a capacity per unit area of 0.25 mAh/cm ² .

(Example 8)
Positive electrode active material 5 (30% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67% by mass) were mixed to prepare a first liquid composition, Liquid Composition G. Liquid Composition G had a viscosity of 10.9 mPa·s and a mode diameter of 2.11 μm.

Using a liquid ejection device EV2500, the liquid compositions G and D were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode E. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid compositions G and D had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.1 mg/cm ² could be formed, and the liquid compositions G and D had good ejection efficiency.

Positive electrode E had a peel strength of the positive electrode mixture of 1.09 N and a capacity per unit area of 0.30 mAh/cm ² .

(Example 9)
Negative electrode active material 1 (30% by mass), carbon black (1% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (69% by mass) were mixed to prepare a first liquid composition, Liquid Composition H. Liquid Composition H had a viscosity of 10.1 mPa·s and a mode diameter of 1.05 μm.

Using a liquid ejection device EV2500, the liquid compositions H and B were ejected onto an aluminum foil as shown in FIG. 2 to obtain a negative electrode A. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid compositions H and B had good ejection stability and did not cause ejection defects. As a result, a negative electrode composite layer with an active material amount per unit area of 2.1 mg/cm ² could be formed, and the liquid compositions H and B had good ejection efficiency.

Negative electrode A had a peel strength of the negative electrode mixture of 1.05 N and a capacity per unit area of 0.32 mAh/cm ² .

(Example 10)
Negative electrode active material 2 (30% by mass), carbon black (1% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (69% by mass) were mixed to prepare a first liquid composition, Liquid Composition I. Liquid Composition I had a viscosity of 13.1 mPa·s and a mode diameter of 2.15 μm.

Using a liquid ejection device EV2500, the liquid compositions I and B were ejected onto a copper foil as shown in FIG. 2 to obtain a negative electrode B. At this time, the copper foil was fixed on a hot plate and heated to 120° C. The liquid compositions I and B had good ejection stability and did not cause ejection defects. As a result, a negative electrode composite layer with an active material amount per unit area of 1.9 mg/cm ² could be formed, and the liquid compositions I and B had good ejection efficiency.

Negative electrode B had a peel strength of the negative electrode mixture of 1.08 N and a capacity per unit area of 2.0 mAh/cm ² .

Example 11
Polyamideimide (6% by mass) and N-methylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (94% by mass) were mixed to prepare Liquid Composition B' as a second liquid composition. In Liquid Composition B', polyamideimide was dissolved in N-methylpyrrolidone and had a viscosity of 9.6 mPa·s.

When polyamideimide (6% by mass) and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (94%) were mixed to prepare a liquid composition, the liquid composition became cloudy and precipitates were formed. In other words, polyamideimide, which is the second electrode material, is more easily dissolved in N-methylpyrrolidone, which is the second liquid, than ethyl lactate, which is the first liquid.

Using a liquid ejection device EV2500, the liquid compositions A and B' were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode A. At this time, the aluminum foil was fixed on a hot plate and heated to 130° C. The liquid compositions A and B' had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 2.2 mg/cm ² could be formed, and the liquid compositions A and B' had good ejection efficiency.

Positive electrode A had a peel strength of the positive electrode mixture of 2.17 N and a capacity per unit area of 0.26 mAh/cm ² .

Example 12
Positive electrode active material 6 (40% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (57% by mass) were mixed to prepare a first liquid composition, Liquid Composition J. Liquid Composition J had a viscosity of 11.9 mPa·s and a mode diameter of 9.11 μm.

Using a liquid ejection device EV2500, liquid compositions J and B were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode F. At this time, the aluminum foil was fixed onto a hot plate and heated to 120°C. Liquid compositions J and B had good ejection stability and no ejection failure occurred. As a result, a positive electrode composite layer with an active material amount per unit area of 2.1 mg/cm2 could be formed, and liquid compositions J and B had good ejection efficiency.

Positive electrode F had a peel strength of 1.13 N and a capacity per unit area of 0.34 mAh/cm2.

Example 13
Positive electrode active material 6 (50% by mass), carbon black (3% by mass), and ethyl lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (47% by mass) were mixed to prepare a first liquid composition, Liquid Composition K. Liquid Composition K had a viscosity of 13.9 mPa·s and a mode diameter of 9.41 μm.

Using a liquid ejection device EV2500, liquid compositions K and B were ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode F. At this time, the aluminum foil was fixed onto a hot plate and heated to 120°C. Liquid compositions K and B had good ejection stability and no ejection failure occurred. As a result, a positive electrode composite layer with an active material amount per unit area of 2.2 mg/cm2 could be formed, and liquid compositions K and B had good ejection efficiency.

Positive electrode F has a peel strength of 1.09 N and a capacity per unit area of 0.36
The capacitance was mAh/cm2.

(Comparative Example 1)
Positive electrode active material 1 (30% by mass), carbon black (3% by mass), polyamideimide (3% by mass), and ethyl lactate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) (64% by mass) were mixed to prepare liquid composition L. However, liquid composition L gelled and could not be discharged.

(Comparative Example 2)
Negative electrode active material 2 (30% by mass), carbon black (10% by mass), polyamideimide (3% by mass), and N-methylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (57% by mass) were mixed to prepare liquid composition M, but the viscosity of liquid composition M increased. Liquid composition M had a mode diameter of 11.5 μm and could not be discharged.

(Comparative Example 3)
Positive electrode active material 1 (30% by mass), carbon black (3% by mass), polyamideimide (3% by mass), and N-methylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (64% by mass) were mixed to prepare liquid composition N. Liquid composition N had a viscosity of 13.5 mPa·s and a mode diameter of 1.71 μm.

Using a liquid ejection device EV2500, the liquid composition N was ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode A. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid composition N had good ejection stability and did not cause ejection failure. As a result, a positive electrode composite layer with an active material amount per unit area of 1.9 mg/cm ² could be formed, and the liquid composition N had good ejection efficiency.

Positive electrode A had a peel strength of the positive electrode mixture of 1.01 N and a capacity per unit area of 0.24 mAh/cm ² .

(Comparative Example 4)
Positive electrode active material 1 (30% by mass), carbon black (3% by mass), and N-methylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (67% by mass) were mixed to prepare liquid composition N'. Liquid composition N' had a viscosity of 10.2 mPa·s and a mode diameter of 1.71 μm.

Using a liquid ejection device EV2500, the liquid composition N' was ejected onto an aluminum foil as shown in FIG. 2 to obtain a positive electrode A'. At this time, the aluminum foil was fixed on a hot plate and heated to 120° C. The liquid composition N' had good ejection stability and did not cause ejection defects. As a result, a positive electrode composite layer with an active material amount per unit area of 1.9 mg/cm ² could be formed, and the liquid composition N' had good ejection efficiency.

Because the peel strength of the positive electrode composite material for positive electrode A' was 0.002 N, the capacity per unit area could not be measured.

Table 2 shows the evaluation results for the amount of active material per unit area, the peel strength of the electrode composite layer, and the capacity of the electrode.

The abbreviations for the liquids are as follows:
NMP: N-methylpyrrolidone DMA: N,N-dimethylacetamide

From Table 2, it can be seen that the electrodes of Examples 1 to 13 have good active material amount per unit area, peel strength of the electrode mixture layer, and electrode capacity, and have a high degree of design freedom. For example, the electrode of Example 11 has a high peel strength of the electrode mixture layer due to the increased amount of binder added.

In contrast, in Comparative Example 1, when preparing the positive electrode A, a single liquid composition L containing ethyl lactate, which is used in the liquid composition A of Examples 1 to 4 and 11, was prepared, and gelation occurred.

In Comparative Example 2, when preparing negative electrode B, a single liquid composition M containing NMP, which is used in liquid composition B in Example 10, was prepared, resulting in an increase in viscosity.

In Comparative Example 3, the amount of active material per unit area of the electrode, the peel strength of the electrode mixture layer, and the capacity of the electrode are good, but the design freedom of the liquid composition N is low.

In Comparative Example 4, the peel strength of the electrode mixture layer is low because the liquid composition N' does not contain a binder.

REFERENCE SIGNS LIST 1 Electrochemical element 10, 15 Negative electrode 11 Negative electrode substrate 12 Negative electrode mixture layer 12A First liquid composition 12B Second liquid composition 20, 25 Positive electrode 21 Positive electrode substrate 22 Positive electrode mixture layer 30 Separator 40 Electrode element 41, 42 Lead wire 51 Electrolyte layer 52 Sheathing

Patent No. 5571304 Patent No. 5913780

Claims (11)

A liquid composition set for forming a positive electrode mixture layer or a negative electrode mixture layer using a liquid ejection device ,
a first liquid composition in which a first electrode material is dissolved or dispersed in a first liquid;
a second liquid composition in which a second electrode material different from the first electrode material is dissolved or dispersed in a second liquid different from the first liquid;
the first liquid composition and the second liquid composition each have a viscosity of 200 mPa·s or less at 25° C.;
The second electrode material is more easily dissolved or dispersed in the second liquid than in the first liquid. The liquid composition set according to claim 1, comprising at least one of the first liquid composition and the second liquid composition. The liquid composition set according to claim 1 , wherein the first liquid composition and the second liquid composition each have a viscosity that enables the first liquid composition to be ejected from a liquid ejection head of the liquid ejection device . The liquid composition set according to any one of claims 1 to 3, wherein the first electrode material includes a conductive assistant. At least one of the first electrode material and the second electrode material contains an active material,
The liquid composition set according to claim 1 , wherein the active material is a material capable of absorbing or releasing alkali metal ions. At least one of the first electrode material and the second electrode material contains an active material,
The liquid composition set according to claim 1 , wherein the liquid composition containing the active material has a content of the active material of 20 mass % or more. The liquid composition set according to claim 1 , wherein the first electrode material and the second electrode material have a maximum particle size smaller than a nozzle diameter of a liquid ejection head of the liquid ejection device . The liquid composition set according to any one of claims 1 to 7, wherein the first electrode material and the second electrode material have a mode diameter of 3 μm or less. The liquid composition set according to claim 1 , wherein the first liquid composition comprises ethyl lactate. The liquid composition set according to claim 1 , wherein the second liquid composition contains N-methylpyrrolidone or N,N-dimethylacetamide. A method for producing an electrochemical element, comprising the step of applying the liquid composition set according to claim 1 onto an electrode substrate to form an electrode mixture layer.

Images