CN115968323A

CN115968323A - Coating method, method for manufacturing fuel cell, method for manufacturing secondary cell, method for manufacturing all-solid-state battery, or all-solid-state battery

Info

Publication number: CN115968323A
Application number: CN202180051435.7A
Authority: CN
Inventors: 松永正文
Original assignee: Mtek Smart Corp
Current assignee: Mtek Smart Corp
Priority date: 2020-09-01
Filing date: 2021-08-04
Publication date: 2023-04-14
Also published as: WO2022049974A1; JP2022041420A

Abstract

When solid particles are made into a slurry and the slurry is formed into fine particles and laminated as a thin film, the slurry needs to have a low viscosity and a low cohesive force. However, there is a problem that solid particles contained in a slurry particularly having a high particle specific gravity or a low viscosity precipitate in a slurry treatment system or an application apparatus. The present invention provides a method for removing bubbles from a slurry of a gas, particularly a gas heavier than air or low-cost dehumidified compressed air, by selecting the gas and mixing the gas into the slurry, finely dividing the gas and mixing the finely divided gas into bubbles, circulating the bubble slurry mixture at a high speed by a circulation device or the like, preventing the precipitation of solid particles even in a slurry of low viscosity, applying the slurry to an object by a slit nozzle, a compressed gas-assisted slit nozzle, a slit spray nozzle, a two-fluid spray nozzle or the like, heating the object as necessary, and crushing the bubbles by the compressed gas spray to apply the slurry to the object, or applying the slurry while removing the bubbles by a compressed auxiliary flow of the compressed gas-assisted slit nozzle, and removing the bubbles from the bubble slurry mixture on the object or removing 80% or more of the foamed gas as necessary.

Description

Coating method, method for manufacturing fuel cell, method for manufacturing secondary cell, method for manufacturing all-solid-state battery, or all-solid-state battery

Technical Field

The present invention relates to a coating method, a fuel cell and a method for manufacturing the same, a secondary cell and a method for manufacturing the same, and an all-solid-state battery and a method for manufacturing the same.

In particular, the material to be coated in the present invention is a liquid, and the liquid contains particles and short fibers, and is usually expressed as a slurry or a dispersion. The slurry may or may not contain a binder or a thickener. Further, it is preferable that the coating composition contains no surfactant or dispersant which adversely affects the coating film performance as much as possible.

In particular, in a liquid containing particles having a median diameter D50 of more than 10 μm, the higher the specific gravity of the particles or the more aggregated the particles, the more likely the particles are to settle. Short fibers having a diameter of the order of nanometers and particularly being thin, for example, single-layer carbon nanotubes, carbon nanofibers having a generally longer fiber length, and the like are effective in the film thickness direction, that is, the longitudinal direction, but graphene or a composite material thereof, which spreads in the transverse direction and contributes to the electrical conductivity thereof, causes different problems such as easy aggregation even if a solvent or the like is added to prepare a dispersion liquid or slurry and the dispersion liquid or the slurry is uniformly dispersed, and further mixed with another liquid, for example, an active material slurry, and the like, and therefore, it is necessary to solve the problems.

In the former, the content of a binder or a thickener such as a resin component is small, and when the viscosity is, for example, 3000 mPas or less, 2000 mPas or less, or even 1000 mPas or less, the solid particles are significantly precipitated, and the quality is deteriorated with time during coating.

The present invention is effective in a method of treating and applying a liquid such as a slurry or a dispersion, and can be characterized in a fuel cell and a method for producing the same, a secondary cell or production thereof, or an all-solid-state cell or production thereof.

In an electrode for a fuel cell, it is important to form desired macropores, mesopores, and optionally micropores, and to leave micropores, mesopores, macropores, and the like.

In contrast, in the formation of the electrode and the electrolyte layer of the all-solid-state battery, it is preferable that no pores are present. In order to improve the performance of an electrode active material of a lithium ion secondary battery during charge and discharge, it is required to form an electrode in which the density distribution in contact with an electrolyte liquid is inclined as the electrode is separated from a current collector, but pores (bubble spaces) need to be formed at a desired density in succession or in stages from a fine high density.

The present invention is not limited to the electrode forming process, the electrolyte forming process of an all-solid battery or the like, or the method of applying a liquid such as a slurry.

The coating to be carried out in the present invention is not particularly limited, and includes a method of directly or indirectly applying particles and fibers to an object by suction or the like, such as roll coating, slit nozzle (slit die) coating, slit nozzle coating in which a slurry or the like is made into particles and discharged from an elongated slit groove, screen printing, curtain coating, dispenser (dispenser) coating, ink jet, atomization (including fiberization) including atomization by a spray nozzle, rotary atomization in which a bell or a disk is rotated at a high speed to form mist by centrifugal force, electrostatic charging and adhesion (including fiberization) of atomized particles by static electricity, and the like, and also includes micro-curtain (micro-curtain) coating. The object may be a powder or granule of a chemical, chemical production, or the like, may be an object, may be a film of a long WEB, or the like, and includes, but is not limited to, the material, shape, weight, number, or the like of the object.

The micro-curtain coating is a method invented by the present inventors, and is a method of spraying a liquid or the like at a low pressure of about 0.05 to 0.7MPa by using an airless spray nozzle (for example, a cross cut nozzle manufactured by noch corporation, usa) having a wide-angle spray pattern, and coating by using a micro liquid film (micro curtain) portion before the spraying and relatively moving an object and the spray nozzle, and it is expected that the liquid coating efficiency is 100% without generating overspray particles. The liquid is drawn by the liquid film gradually expanding from the nozzle tip and finally becomes unstable longer liquid flow or large liquid drops from the two ends of the bottom edge of the triangular or bell-shaped liquid film. When the pressure is a hydraulic pressure of, for example, about 3.5MPa · s or more, the triangular liquid film of the liquid film becomes small, the liquid droplets downstream of the liquid film gradually become small by collision with the atmospheric pressure, and in the case of a small-flow wide-angle spray nozzle, the spray particle diameter may be, for example, about 20 μm when the distance is about 250 mm. On the other hand, in the case of coating with a liquid film, it is preferable to coat the liquid film (curtain) upstream of the maximum bottom width of the liquid film before the liquid droplet is formed at the lower pressure, and since the maximum bottom width varies depending on the kind of nozzle (flow rate, pattern width, etc.), hydraulic pressure, viscosity, etc., the liquid film is generally coated with a desired flow rate of about 5 to 20 mm in width. In the case of a solution containing no particles, the relative movement between the object and the airless nozzle can be performed at an intermediate speed of about 30m/min, and even when the object and the airless nozzle are relatively moved at a speed of about 60m/min or higher, for example, 100m/min or higher, and when the solvent is a high boiling point solvent and evaporation of the solvent is slow, the solution can follow the movement because the solution is merely leveled while forming a thin film. However, streaks at both ends of a liquid film such as a triangle, which have a flow rate 10 times or more as large as the flow rate at the center, and streaks in which the flow rate of a resin solution or the like is large when an object is at room temperature, level on the object due to the surface tension of the solution or wetting of the object, and form a wet coating film having a uniform thickness. On the other hand, in a liquid containing slurry solid particles, since solid particles and the like are concentrated in streaks and contain many particles, and the liquid becomes a thixotropic fluid after being applied to an object, leveling is difficult, and streaks at both ends of the triangular liquid film portion accumulate and coating film streaking lines where 2 sides of particles flow out remain.

The atomization (fiberization) is performed by atomizing a liquid containing fine solid particles by ultrasonic waves or the like while vibrating the liquid surface, or by spinning such as electrostatic spinning, or by granulating or fiberizing by centrifugal force of a rotating body, in addition to granulation by spraying. Further, fine particles generated by atomization or other methods, for example, by breaking a liquid film of bubbling or the like, or by collision with another object or the like, may be carried by a carrier gas and directly applied. The particles and the like may be charged and coated. Or a method of applying a fine pattern by drawing and fluidizing a particle group at a high speed with different compressed gases, a method of applying a melt blowing method applied as a two-fluid spray to a liquid, and the like to produce particles and fibers corresponding to an object having a wide range of high line speeds. In the ultrasonic atomization and centrifugal atomization, since the atomized particles have unstable directionality, a process of attaching or applying the particles to an object by the force (air assist) of a compressed gas such as argon gas, nitrogen gas, or the like, which is a passive gas, or a compressed gas which is dried as necessary, is also included in the present invention. In the present invention, they will be described below collectively as a spray.

Background

The coating of functional material objects is mainly a thin film.

Among organic solar cells, perovskite solar cells are most promising, and attempts have been made to apply a perovskite chemical solution as a thin film over a large area of 300mm × 300mm by an ink jet method. In addition, development of reducing the amount of catalyst in a fuel cell is in progress, and for example, the amount of a metal catalyst such as a platinum catalyst or a platinum-cobalt catalyst is required to be 0.3 mg or less per square centimeter at a cathode, and is required to be very small, such as 0.05 mg, at an anode. Since platinum has a specific gravity of 20 or more, although it is as small as several nanometers, carbon particles supporting platinum also become primary particles of several tens of nanometers, the solid content of an electrolyte solution of a ionomer such as a Nafion solution is 5 to 10%, and the total content of nonvolatile components is also very small. Or typically 5 to 15% solids, needs to be reduced to 1 to 3% or less. In this case, since the amount of the solvent is large, the electrolyte membrane is generally easily swelled by the solvent, particularly moisture, and the like, and even if the particle size of the solid component is small, the specific gravity is heavy, and therefore, the carbon and the aggregate generated in the electrolyte solution are affected, and it is necessary to prevent the precipitation.

Further, when active material particles of a secondary battery, active material particles of an all-solid battery, electrolyte particles, fine particles of carbon or the like as a conductive aid, carbon nanotubes, particularly single-layer carbon nanotubes (SWCNTs), carbon Nanofibers (CNTs), and a slurry composed of a binder such as vinylidene fluoride (PVDF) or a solvent thereof, for example, n-methylpyrrolidone (NMP) or the like are mixed, aggregation tends to occur, or uniform dispersion tends to be impossible.

Patent document 1 is an invention of the present inventors, and is mainly used for preventing sedimentation of phosphor slurry in the LED field and moving two containers. A method of mixing bubbles into a slurry to prevent settling is disclosed.

In patent document 2 and the like, a gas such as nitrogen is mixed as bubbles into a thermoplastic adhesive which is heated and melted, and the mixture is pressurized, and sufficiently mixed into fine bubbles which are invisible in a pressurized state, and the mixture is applied to an object by a discharge device and returned to the atmospheric pressure to foam the object, and at least the surface of the applied mixture is rapidly brought to the softening point or less by cooling the surface in the atmospheric air, whereby a foam can be formed. Therefore, even if the interior is completely returned to normal temperature, air bubbles are mixed in to make the interior elastic, and therefore, the gasket is often used for the purpose of a gasket.

In patent document 1, since the apparatus is small in size in application, and air bubbles are mixed into the slurry in the lower part of the vessel moving between two small vessels, and the pressure in the vessel is low, the mixing efficiency of air bubbles is particularly poor when the liquid surface in the vessel where the air bubbles move is easily defoamed and the slurry has a low viscosity, and the mixing ratio of air bubbles and slurry may vary because a density sensor or the like is not used in the air bubble slurry mixture system and is simplified.

The method of patent document 2 mainly aims at: for example, a foam is produced by mixing bubbles into a hot melt adhesive which is heated and melted at about 120 to 200 ℃, spraying the mixture to an object in the form of the hot melt adhesive mixed with the bubbles by a spray device, and cooling the mixture while enlarging the bubbles for the purpose of, for example, a gasket.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-107355

Patent document 2: japanese unexamined patent publication No. 53-017645

Disclosure of Invention

(problems to be solved by the invention)

In the present invention, the slurry is prepared by mixing bubbles into the slurry and circulating the slurry at a high speed as a bubble slurry mixture, preventing the precipitation of solid particles and short fibers in the slurry by the force of the bubbles to improve the dispersion state, and moving the slurry composed of the particles in the slurry, a binder or a thickener, and a solvent, which are added as necessary, and the bubbles to a discharge device or a coating device in a uniform mixing state, thereby eliminating unnecessary bubbles after the discharge device or the coating device, or intentionally leaving a small amount of bubbles, for example, 20% or less, as necessary.

(means for solving the problems)

The present invention has been made to solve the above problems, and an object of the present invention is to provide a high value-added coating method, a method for manufacturing a fuel cell or a fuel cell that forms an electrode of a fuel cell, a method for manufacturing a secondary cell or a secondary cell that forms an electrode of a secondary cell, particularly an all-solid-state cell or an all-solid-state air cell, or a method for manufacturing a secondary cell or a secondary cell that forms an electrode or a solid electrolyte of a secondary cell.

In the present invention, for example, in the case of an all-solid battery, active material particles for a positive electrode or a negative electrode and particles for an electrolyte or short fibers are made into slurry separately, and the slurry is laminated and coated in a desired order by respective apparatuses. When a film is formed and a plurality of layers are formed as many as possible, a desired mixed coating can be performed, and thus it is effective. Or all the particles and the like may be mixed as necessary or some of them may be selected and mixed as necessary to prepare a slurry, and the slurry may be laminated as a thin film. The mixing or mixing of the bubbles in the slurry may be performed until the most forward end of the discharge device or the application device, or more preferably, the slurry bubble mixture is circulated at a high speed by a pump or the like to form a uniform mixture, and the uniform mixture is applied to the object by the discharge device or the application device. The high speed in the present invention may be 0.3m/s or more, for example 1.5m/s or more. Further, it is more preferable to provide a static mixer, a dynamic mixer, or an impingement mixing device or the like, which has been proposed by the present inventors in the past, in the middle of the circulation circuit to promote mixing of the slurry and the gas, because a desired bubble slurry mixture can be obtained in a short time. In the present invention, the air bubbles are mixed into the slurry having a high viscosity or a high solid content to form a state in which the particles and the like are not easily precipitated, and the mixture is mixed with the solvent before the coating apparatus or in the coating apparatus, or even outside the coating apparatus, thereby making it possible to quickly coat the mixture to the object at a low viscosity. Therefore, the problem of precipitation, which is a weak point of the low viscosity slurry, can be solved, and thus the method is particularly suitable for thin film coating in which fine particles are formed by spraying or the like.

In the method of the present invention, in addition to the two-fluid spray, the carbon dioxide can be easily atomized by rotary atomization, selecting carbon dioxide as a gas, and forming a supercritical fluid. By selecting at least 1 of the two-fluid sprays, i.e., the melt blowing method using compressed gas, the air-assisted slit nozzle, the slit spray nozzle capable of spraying from a narrow elongated groove in a wide range, and the like, it is possible to coat even a wide and long object by forming particles at a high speed. In the present invention, the coating can be performed while preventing the particles from settling by the bubbles and easily eliminating the bubbles downstream of the coating apparatus.

In the present invention, the flow rate detection can be performed by using a flow meter capable of detecting the flow rate of the bubble slurry mixture moving in the pipe outside the pipe, and the quality control is performed by controlling the flow rate detection and the flow rate measurement in combination with the method of WO2013108669 invented by the present inventors, that is, the method of applying the bubble slurry mixture to the object before applying the bubble slurry mixture to the object and measuring the bubble slurry mixture. A densitometer may also be provided in place of the flow meter described previously. By using a positive displacement pump, the quality of the mixed amount of bubbles per unit volume can be controlled in relation to the density of the densitometer if the circulating hydraulic pressure is constant. Therefore, the coating weight per unit area is accurately controlled. When it is desired to perform the control as needed, the control can be performed by using a commercially available flow meter device or the like capable of controlling the flow rate of each slurry or the flow rate change of the circulation line before, after, or both of the discharge devices from the outside of the flow path such as a pipe. In particular, in the case of pulse-type spraying, it is effective to easily manage the waveform of the hydraulic pressure, to increase the decrease in the hydraulic pressure, and to easily check the change in the flow rate. Further, it is possible to confirm the consistency with the data in the coating weight measuring apparatus at a desired timing. Therefore, for example, the coating weight of each material can be constantly or instantaneously controlled at a fine portion of the electrode, and a high-performance and high-quality electrode or the like can be formed.

The present invention provides a method for applying a liquid containing at least particles or particles and short fibers to an object, the method comprising:

mixing a nonvolatile component containing at least particles or at least particles and short fibers and at least a solvent to make a slurry;

mixing air bubbles into the slurry to prepare an air bubble slurry mixture, and circulating the air bubble slurry mixture at a high speed in a slurry circulation flow path to prevent at least the particles from settling; and

the bubble slurry mixture is applied to an object by an application device communicating with the slurry circulation passage while eliminating at least a part of the bubbles.

The coating method is characterized in that the ratio of the nonvolatile components of the slurry is 65 wt% or less, the weight ratio of the solid particles or particles to the short fibers is 55 wt% or less, the binder is 10 wt% or less, the volatile components are 35% or more, and the viscosity of the slurry is 3000 mPas or less.

The coating method of the present invention is characterized in that the viscosity of the slurry is 1000 mPas or less,

the gas for bubbling is selected from at least 1 of dehumidified compressed air, argon gas, nitrogen gas, and carbon dioxide, and the gas for bubbling is finely divided and supplied in a pulse form so as to be mixed into the slurry, thereby heating the object.

The coating method of the present invention is characterized in that the slurry contains a binder, and the solvent is composed of at least 2 or more solvents, wherein at least 1 solvent is a precursor solvent of the binder, and the remaining at least 1 solvent is a solvent having a boiling point lower than that of the precursor solvent and having an azeotropic effect and a boiling point of 120 degrees or less.

The coating method according to the present invention is characterized in that 80% or more of gas contained in the bubbles mixed in the slurry is removed between the coating device and the object or on the object.

The coating method according to the present invention is characterized in that the coating device is a spraying device, and a solvent is added between the upstream and downstream of the spraying device to reduce the viscosity of the slurry and coat the slurry on the object.

The coating method according to the present invention is characterized in that the object is a long substrate to be treated by roll-to-roll, and the coating device selects at least 1 kind from a slit nozzle, a compressed gas-assisted slit nozzle, a slit spray nozzle, or a spray head having at least a plurality of two-fluid spray nozzles, which are provided perpendicularly or substantially perpendicularly to the substrate.

The present invention provides a method for producing a fuel cell or a fuel cell, wherein the object is an electrolyte membrane or a gas diffusion layer for a fuel cell, and a slurry is an electrode ink containing platinum catalyst nanoparticles in an amount of 0.5 to 15 wt% as a solid content, thereby forming a membrane-electrode assembly.

The present invention provides a method for producing a fuel cell or a fuel cell, wherein the object is an electrolyte membrane or a gas diffusion layer for a fuel cell, and the slurry is an electrode ink containing platinum catalyst nanoparticles in an amount of 0.5 to 15 wt% as a solid content, thereby forming a membrane-electrode assembly.

The present invention provides a method for manufacturing an all-solid battery or an all-solid battery, wherein the object is selected from a current collector, an electrode layer, and a solid electrolyte layer, and the slurry is an electrode slurry or a solid electrolyte slurry.

In the present invention, the number, shape, kind and specific gravity of the particles and short fibers are not limited.

In the present invention, the kind of the binder and the solvent is not limited. An electrolyte solution such as an ionomer of a fuel cell, for example, a Nafion solution of dupont, a binder such as vinylidene fluoride (PVDF) for a positive electrode of a secondary battery, or Styrene Butadiene Rubber (SBR) for a negative electrode, may be used, and in addition thereto, for example, glycerin used as a high boiling point thickener, or the like may be used. It is expected that glycerin exerts an azeotropic effect with a low-boiling solvent such as ethanol or 2-propanol. In the present invention, the evaporation of the solvent or thickener can be promoted by heating the object, applying the slurry under vacuum, or moving the object to vacuum after coating.

In the present invention, the kind of the secondary battery is not limited. The battery may be a lithium ion secondary battery or a sodium ion secondary battery.

The secondary battery of the present invention may be an all-solid-state battery, which is a secondary battery of a next generation, or an all-solid-state air battery.

In the present invention, the kind of the sulfide-based or oxide-based solid electrolyte particles is not limited, and the kind and shape of the active material particles for the positive electrode or the negative electrode are not limited.

In the present invention, the porous carbon supporting platinum particles of several nanometers on the surface of the fuel cell supports platinum in mesopores and macropores on the surface, so that poisoning due to contact with an ionic polymer with time can be reduced, and micropores, mesopores, and macropores can be formed in an electrode by stacking the carbon particles by pulse spraying or the like. But also the contact area of the interface can be increased, so that the battery performance can be improved.

In the present invention, if a slit nozzle is used and a low solid content, for example, a 7 wt% solid content ink is added to a target such as an electrolyte membrane (PEM) at the outlet of the slit nozzle with glycerin having a boiling point of about 400 ℃ added to increase the viscosity, the WET coating thickness is covered with air bubbles, and the ink viscosity can be instantaneously reduced by heating or adsorption heating from the opposite side to the PEM coating after coating. If no air bubbles exist, the coating can be only coated on rough and porous surfaces.

In the present invention, the application of the bubble slurry mixture may also be performed under vacuum.

In the present invention, the cavity such as the inside of the nozzle downstream of the on-off valve of the coating apparatus can be reduced to the limit. In general, the bubble slurry mixture in the cavity section downstream of the open/close valve is drawn to the outside of the nozzle or the like by the pressure difference when the valve is closed, and large droplets of the slurry component are discharged by the explosive foaming of the bubbles. In particular, in the present invention, a separate gas ejection device is provided outside the nozzle in the cavity as needed, and the gas ejection device collides with the ejection flow, thereby allowing high-speed intermittent application, that is, pulse spraying. In addition, the object may be heated during coating. In the present invention, the slurry binder or thickener of the bubble slurry mixture is heated on the object at the time of coating, the viscosity is rapidly reduced, and the cohesive force of the binder is reduced, so that defoaming and bubble collapse are promoted, and the solvent is rapidly volatilized, so that the volatilization of the solvent by azeotropic boiling of 2 or more solvents is further promoted, and a desired coating film can be formed by appropriate solvent balance or the like. For example, the surface of the coating film can be formed into a dried coating film having irregularities due to the deposition of particles. On the other hand, a desired amount of the high-boiling solvent may be left, and the binder on the surface of the coating film may be leveled in post-drying in an oven or the like to obtain a desired smooth surface state. For example, it also helps to level the small particles with the binder to level the surface. In addition, by applying the bubble slurry mixture to an object under vacuum, a coating film in a dry state can be obtained and a desired speed can be satisfied.

According to the method for producing a secondary battery of the present invention, for example, the method for producing a positive electrode can be, for example, a method for producing a positive electrode in which a ternary system (NCM) active material, a conductive assistant, PVDF, and NMP as a matrix solvent are mixed to prepare a slurry, and air bubbles are further mixed in, and the slurry is applied to an aluminum foil as a current collector. The conductive aid dispersion liquid may contain a small amount of a binder and/or air bubbles. In the present invention, in order to promote volatilization even in a high boiling point solvent, the current collector is adsorbed by the heating roller, the heating table, the heating adsorption roller, and the heating adsorption table to prevent the reduction of vaporization heat due to solvent evaporation, and the solvent can be instantaneously volatilized by applying the slurry or the like since the heat is applied from the inside of the roller or the like. In addition, in the present invention, an oblique coating may be performed in which the density of the electrode close to the current collector is changed stepwise or continuously as the distance from the current collector increases to eliminate the aforementioned bubbles and leave a desired amount of bubbles. In this case, a plurality of types of coating apparatuses such as a slit nozzle, a compressed gas-assisted slit nozzle, and a spray nozzle apparatus can be selected, and the presence or absence of air bubbles mixed in each slurry can be selected in consideration of the internal structure of each desired electrode film.

In the present invention, instead of the electrode formation of the secondary battery, in the electrode formation of the all-solid-state battery to which the electrolyte particles are added and the electrolyte layer formation, the slurry for the electrolyte layer may be similarly mixed with air bubbles to prevent precipitation.

In the present invention, for example, a single or a plurality of kinds of particles such as active material particles, single slurry in which short fibers such as single-layer carbon nanotubes (SWCNT), carbon Nanofibers (CNF), and graphene or fine carbon particles are mixed as a conductive additive, may be used for layer coating, but the present invention is not limited thereto, and a plurality of slurries of different kinds, a dispersion of a plurality of conductive additives, and the like may be prepared, and electrodes having a desired distribution may be formed using a plurality of coating apparatuses corresponding thereto. And further, bubble mixing can be selectively performed among them.

In addition, short fibers such as SWCNT and CNF, which are particularly effective as a conductive aid, stand upright like bristles in the film thickness direction of the electrode (stand upright in the vertical direction and support the movement of electrons and the like in the vertical direction), and therefore, the object can be achieved by making a slurry or dispersion alone and using static electricity such as bristles, or using an apparatus such as electrospinning, regardless of the presence or absence of the bubbles of the present invention. Graphene alone or in combination with SWCNT or the like is effective for lateral spreading of the electrode film. Particularly, it is important that the present inventors propose that separate slurries, dispersions, and the like of different kinds are alternately laminated in a thin film form or in a slight amount in a plurality of layers by separate means. In the present invention, even if the solvent is a high boiling point solvent such as NMP, the ratio of the gas to the sprayed particles is made rich by pulse spraying or the like, and the coating can be performed in a directional manner while increasing the contact between the fine particles, short fibers and the gas. The solvent vapor may be volatilized by heating the dispersion liquid, slurry, or the like, or by heating a carrier gas for moving the sprayed fine particles or the like. Therefore, in the present invention, appropriate treatment can be performed under the condition that the solid component of the dispersion liquid of the conductive assistant or the like is 0.5% or less, even 0.05% or less, and the movement of electrons or the like in the electrode can be effectively supported by additional pulse-like spraying, static electricity.

In the present invention, in order to prevent the performance degradation due to the expansion and contraction of the metal silicon particles or the silicon oxide (SiOx) particles effective for the negative electrode, a binder or the like having a strong adhesion effect is used, and it is preferable that the silicon particles or the like are partially covered with a spider-nest structure of fine fibers so as to be firmly attached to the inside of the porous portion of the porous carbon, the SWCNT, or the carbon nanocup. That is, even if the silicon particles expand and contract, they are supported by the carbon structure or the macropores of the macroporous carbon, and are further held by a strong adhesive, a binder fiber having a large surface area, or the like. Particles of the above-mentioned substances are formed by each spray head and laminated, and particles or fibers of nonwoven fabric (spider web shape) are partially formed on the silicon surface, and the particles and fibers are adhered to the carbon structure, silicon, or SiOx, and an electrode layer is formed at the same time. In particular, the pulsed method with impact forces is most suitable for making the adhesive into a spray, or particles, which are moved and partially attached to the silicon surface. Carbon particles or the like as a negative electrode active material may be added to the binder solution or the binder emulsion to prepare a slurry, and the slurry may be applied.

In the present invention, as described above, the metal silicon or silicon oxide of several tens to several hundreds nanometers, and if necessary, several nanometers is supported in the pores of the macroporous carbon or on the carbon structure, and further supported by, for example, a binder or the like which forms a network of fine carbon, a similarly fine spider web, or short fibers, the dropping of silicon due to expansion and contraction during charging and discharging of the secondary battery can be suppressed.

In the present invention, the object may be heated. The heating temperature is preferably 30 to 200 ℃, more preferably 50 to 150 ℃ because the viscosity of the binder can be drastically reduced to expand and collapse the bubbles. Further, since the adsorption target can heat and heat the adsorption drum from inside, for example, the temperature drop due to the vaporization heat of the solvent can be prevented, and the evaporation of the solvent can be promoted. In particular, the solvent component of the slurry that has been micronized by spraying or the like can be evaporated while contacting and wetting the object. The time until 95% or more of the solvent is evaporated may be 5 seconds or less, and more preferably 2 seconds or less.

In the present invention, when bubbles of the slurry are crushed by the gas pressure and velocity of the two fluids to be made into particles and attached to the object, the impact force of the spray particles can be increased by performing the pulse-like process and by reducing the distance between the tip of the coating head and the object to, for example, 50 mm or less, and thus high-density solid particles can be stacked.

(effect of the invention)

As described above, according to the present invention, a high-performance coating method, a method for manufacturing a fuel cell, a method for manufacturing a secondary cell, a method for manufacturing an all-solid-state battery, or an all-solid-state battery can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view of an embodiment of the present invention in which slurry in a vessel is moved downstream by a 1 st pump, mixed with gas similarly moved downstream of a gas cylinder, and the gas-slurry mixture is pumped by the pump and circulated in a circulation circuit, and a coating head is disposed in a circulation flow path.

Fig. 2 is a schematic cross-sectional view of the embodiment of the present invention in which the slurry in the vessel is pressurized with the pressurized gas and moved to the downstream, and the slurry is mixed with the gas similarly moved to the downstream of the gas cylinder, and the gas-slurry mixture is pumped by the pump and circulated in the circulation circuit, and the coating head is disposed in the circulation flow path.

Fig. 3 is a schematic cross-sectional view of a circulation system of a slurry mixture of bubbles in each slurry in a tank, in which a gas is bubbled into the slurry in a tank from below to form a structure in which bubbles are less likely to rise to the surface of the slurry, a mixture of bubbles and the slurry is stirred and collected, the mixture is circulated by pumping the mixture, a coater is provided in the middle of the circulation, and the mixture of bubbles and the slurry flows into an outlet of the circulation to form a bubble-slurry mixture of each slurry in the tank.

Fig. 4 is a schematic cross-sectional view of a circulation movement system of a bubble slurry mixture in which bubbles of gas are mixed into a slurry in a pressurized 1 st vessel, a rough mixture of the bubble slurry is prepared by a stirring device, the rough mixture is moved into a 2 nd vessel that is not pressurized or has a pressure lower than the pressure in the 1 st vessel by a coating device, and the bubble slurry mixture in the 2 nd vessel is moved into the 1 st vessel by a pump at a pressure higher than the pressure in the 1 st vessel to form a more dense mixture of the bubble slurry mixture according to an embodiment of the present invention.

Fig. 5 is a schematic cross-sectional view of the embodiment of the present invention in which, when a slit nozzle (a type of coating device) is used to coat a bubble slurry mixture, the slurry is applied to an object while a compressed gas is discharged or jetted from the slit nozzle on the side of the moving direction of the object to break the bubbles.

Fig. 6 is a schematic cross-sectional view of the embodiment of the present invention in which, when applying a bubble slurry mixture to an object by a slit nozzle (a type of application device), the slurry is applied to the object while flowing out or jetting compressed gas from both sides of the slit nozzle to break the bubbles.

Fig. 7 is a schematic sectional view of a main liquid film spray pattern in which the bubble-free slurry mixture is sprayed from the airless nozzle, and a plan view and a schematic sectional view in the case of applying the bubble-free slurry mixture to an object as a liquid film according to the embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The following embodiments are merely examples for facilitating understanding of the present invention.

The drawings show schematically preferred embodiments of the invention.

In fig. 1, the slurry 2 in the container 1 is pumped by the 1 st pump 3 downstream and sent to the subsequent step through the pipe 110. The slurry 2 may be stirred by a stirring device (not shown). In particular, when the specific gravity of the particles is high, stirring by a stirring device or the like is preferable. The compressed gas is supplied from a gas cylinder 4 and is regulated to a desired pressure by a regulator 5 as a pressure regulating means. The slurry and the gas are merged via check valves 6, 7 and the like as a backflow prevention valve. The slurry is mixed in the mixing device 8 after being merged to be a bubble slurry mixture, and is sucked by the 2 nd pump 9 again through the pipe 10, the coating devices 101 and 102, and the pipe 103 returning from the coating device by the 2 nd pump 9 via the circulation valve 104 to form a circulation circuit. The consumed amounts of the coating devices 101 and 102 are automatically fed from the mixing device 8, and an automatic circulation system is configured. In the case of a simple system, the 2 nd pump is preferably a plunger pump of a balanced feed type which automatically sucks and pressurizes a consumed material.

But may of course also be a positive displacement pump.

On the other hand, the 1 st pump is preferably a volumetric pump such as a rotary electric spur gear because the volumetric ratio to the gas can be easily adjusted.

As for the feeding of the gas, it is preferable to intermittently feed fine bubbles at a high speed by an ultra-precise automatic opening and closing valve (not shown) that is opened and closed in units of milliseconds or microseconds.

In fig. 2, the slurry 22 in the vessel 21 is pressure regulated and pressurized by a regulator 23 of compressed air or a passive gas source (not shown). Is sucked by the 1 st pump 3 downstream and sent to the subsequent step through the pipe 110.

The slurry 22 may be agitated using an agitation device (not shown). In particular, when the specific gravity of the particles is high, it is preferable to stir the particles by a stirrer or the like. From the gas cylinder 25, the compressed gas is regulated to a desired pressure by a regulator 24 as a pressure regulating means. The slurry and the gas are merged via automatic opening and closing

valves

26, 27, and the like. The slurry is mixed in the mixing device 28 after being merged to form a bubble slurry mixture, and is pumped by the pump 29 again through the pipe 200, the

coating devices

201 and 202, and the pipe 203 returning from the coating devices by the pump 29 and the circulation valve 204 to form a circulation circuit. The amounts consumed by the

coating devices

201 and 202 are automatically fed from the mixing device 28 side, and an automatic circulation system is configured. In the circulation circuit, a mixing device or a dispersing device such as a static mixer, a dynamic mixer, or a collision mixing method invented by the present inventors can be used to densely disperse the bubbles and the slurry. When a simple system is configured, the pump 29 is preferably a plunger pump of a balanced feed type that automatically sucks and pressurizes a consumed material.

But may of course also be a positive displacement pump. Since bubbles in the circulation circuit become smaller as the liquid level increases, and the bubbles are in a state close to being dissolved, it is difficult to visually confirm the bubbles even if the confirmation is performed through the transparent pressure-resistant glass.

In the gas feeding, a large amount of fine bubbles can be intermittently fed at a high speed by opening and closing the automatic opening and closing valve 27 in units of milliseconds or microseconds.

In fig. 3, the slurry 32 in the container 31 can be stirred by the stirring device 34 to maintain a desired dispersion state. The gas moves from the gas container 36 to below the container 31 through the regulator 35 for regulating the gas pressure, and moves through the automatic opening/closing valve 37 connected to the inside of the container 31 through the flow path to enter the container. The gas is subdivided by the automatic on-off valve 37 to form the desired bubble slurry mixture with the slurry 32. A mask 305 as a three-dimensional shielding plate is provided so that air bubbles are not easily moved to the upper portion of the container.

The gas may be a heavier specific gravity gas depending on the specific gravity of the slurry. For example, argon gas and carbon dioxide are preferably heavier in specific gravity than nitrogen gas, and it takes time to reach the upper surface of the slurry in the container 31.

The gases may be independently discharged, for example, into the slurry 32 in the vessel 31, mixed and used.

The bubble slurry mixture is pumped and pressurized by the pump 38, and is moved to the lower side of the shielding plate 305 in the container 31 via the pipe 39, further via the coating device 301, further via the return pipe 302, and the circulation valve 303 for adjusting the circulation amount, and is mixed by the stirring device 34. Downstream of the recirculation valve may also be returned to near the suction of the pump 38. A mixing device, a dispersing device (not shown) may be provided in the circulation circuit, so that the bubble slurry mixture can be formed into a dense mixed state and coated by the coating device 301.

In fig. 4, the slurry 42 in the 1 st vessel 41 is pressurized by a regulator 400 of compressed gas that sets the vessel 41 to a desired pressure. The slurry in the container 41 is stirred by the stirring device 44. As previously mentioned, a variety of heavier specific gravity gases may be selected.

The pressurized slurry 42 flows into the 2 nd vessel 401 through the coating device 48 via a pipe for a flow path 47 communicating with the lower part of the vessel. The slurry 402 in the 2 nd vessel is pumped by a pump 405 through a pipe 403 and discharged to the lower part of the 1 st vessel through a pipe 406.

An automatic opening/closing valve 420 for supplying bubbles (gas) is provided in the middle of the pipe 403 for sucking the slurry 402 by the pump 405. The gas of cylinder 46 is regulated to a desired pressure by regulator 45. The 2 nd vessel 401 may be pressurized to a lower pressure than the 1 st vessel. The slurry in the 2 nd vessel 401 can be stirred by the stirring device 403.

Further, when a lower limit is detected by a level sensor (not shown) of the slurry 402 in the 2 nd container 401, the operation of the pump 405 can be automatically stopped. On the other hand, when the level of the slurry in the 1 st vessel decreases, a level sensor (not shown) is used for detection to stop the circulation system and the coating, and the slurry is filled. The slurry may be automatically supplied by a separate automatic slurry supply system, or may be manually supplied by removing an upper cover of the 1 st container 41. Further, the 2 nd flow path 430 having a small internal resistance different from the

flow paths

47 and 49 of the coating device 48 may be provided for the movement of the slurry or the bubble slurry mixture from the 1 st tank 41 to the 2 nd tank 401. The resistance of the 2 nd flow path 430 may be reduced by increasing the cross-sectional area of the flow path, shortening the flow path, and both. For example, when a PFA tube having a flow path inner diameter of 4 mm is used in a moving coating apparatus, the inner diameter of the 2 nd flow path may be, for example, 6 mm or 8 mm or more. Mixing

devices

460 and 470 such as static mixers and dynamic mixers using motive power can be provided upstream of the coating

device flow paths

47 and 49 and the 2 nd flow path 430, for example. The bubble slurry mixture pumped and pressurized by the pump 405 with the passage of time is mixed in a mixing device provided in the pressurizing pipe 406, discharged at a pressure higher than the 1 st vessel pressure, flowed into the 2 nd vessel 401 via the

flow paths

47 and 49 and, if necessary, via the 2 nd flow path 430, and further pumped to form a circulation circuit, and the bubble slurry mixture forms a denser bubble slurry mixture with the passage of time, and can be applied by the application device 48. The upper surface of the slurry 42 in the 1 st vessel 41 may be provided with a plunger to isolate it from the compressed gas.

FIG. 5 is a cross-sectional view of the tip of a compressed gas (air) assisted slit nozzle. A slit nozzle 52 downstream of an automatic on-off valve of a coating device (not shown) is shown. Since the bubble slurry mixture is narrow in gap and pressurized in the slit nozzle 52, the bubbles of the bubble slurry mixture do not expand. However, at the instant of exit from the nozzle, the bubble expands. The compressed gas is discharged from the tip nozzle through the flow path 53 toward the tip of the slit nozzle 52 or toward the bubble slurry film 56 at the moment of application to the object, and the bubbles are appropriately crushed and the coating film 56 is formed. When the object is heated, the viscosity of the applied bubble slurry mixture, particularly the viscosity of the binder or thickener, is lowered, the bubbles expand, the bubbles are easily crushed by the compressed gas, and evaporation is promoted even if the solvent is a high boiling point solvent such as NMP.

Fig. 6 shows a tip portion of a slit nozzle 62 of a modification of the compressed gas (air) -assisted slit nozzle. Compressed gas is ejected from the compression flow path from both sides of the ejection flow of the bubble slurry mixture from the slit nozzle. Therefore, the slurry can be applied to the object while breaking up the bubbles, and the slurry can be sprayed to form spray particles.

The slit nozzle length may be 100 mm, 500 mm, 1000 mm, 2000 mm or longer. The slurry can be applied to the object with a width approximately equal to the length of the slit nozzle. When the slurry is granulated and coated, the gasket opening, which determines the width of the slit flow, is formed as a strip, and the length of the openings (which may be elongated strips) may be 50 microns, 200 microns, 500 microns, or 1 mm, for example, while the length of the non-opening portion may be 5 mm, 10 mm, etc. The thickness of the gasket may also be, for example, 100 microns, 150 microns, 200 microns, or more.

The gas ejection ports on both sides of the slurry are processed in the same manner as the liquid opening, and when the liquid opening length is 200 μm, the amount of the compressed gas used can be significantly reduced by making the liquid opening length slightly longer, for example, 100 μm in the front and rear directions.

For example, a plurality of openings of 200 μm square can be formed at a desired pitch (for example, 15 mm) within a pitch of 5 to 50 mm so that the discharge patterns of the slurry from the respective openings, which are formed into particles, do not interfere with each other.

Even in a wide and long object, for example, a copper foil, an aluminum foil, or a stainless steel foil, which is a secondary battery current collector having a width of 1 m or more, the discharge portion is limited, but the slit nozzle can be moved vertically to the object in a short distance at a high speed (for example, 7.5 mm under the above-mentioned conditions). This method can be applied to the field of the present invention even if bubbles are not mixed in the slurry, and can also be applied to many other fields such as spraying of a solution, fiberization of a thermoplastic binder, that is, melt blowing, and the like.

In fig. 7-a of fig. 7, a bubble slurry mixture having a relatively low viscosity is discharged from the airless spray nozzle 71 at a relatively low hydraulic pressure (about 0.15 to 0.6 MPa).

The liquid film 72 becomes triangular from the tip of the airless spray nozzle 71, and then breaks, producing streaks 74 of unstable liquid lumps at both ends, and large droplets 75 downstream of the liquid film. Generally, the coating liquid is applied to an object or the like in the vicinity of the production line 73. The flow distribution of the liquid film in the production line 73 is the

flow

76, 78 having a larger flow at both ends and the flow 77 having a smaller flow at the center. The flow rate distribution of the flow can be measured by instantaneously applying a slurry composed of a solvent having a relatively high boiling point as a liquid film to a corrugated cardboard vertically arranged. The same results were also obtained by applying bubble-free slurries of higher boiling solvents under the same conditions.

Fig. 7-b of fig. 7 is a plan view showing that the object 700 and the liquid film at the position of the production line 73 are relatively moved, and the liquid film of the bubble slurry mixture is applied to the object 700. At the moment of application, the

portions

76 and 78 where the flow rate is high and the portion 77 where the flow rate is low appear on the object.

In fig. 7-c of fig. 7, the liquid film of the airless spray nozzle 71' moves relative to the object 700, and a coating film of the bubble slurry mixture is formed on the object. When the object 700 is heated or is a low boiling point solvent or both, the application flow rate distribution becomes a dry film having a large flow rate at both ends, similarly to the flow rate distribution of the liquid film of the nozzle. When the boiling point of the solvent in the slurry is high and the object 700 is at room temperature or lower, the portions 76' and 78' having a large flow distribution (thick films) flow to the portions 77' having a small flow distribution (thin films) in the central portion due to surface tension and are transferred by wetting of both ends of the liquid film, thereby forming a relatively flat film.

Further, the nozzle 71' is fed from above the film, which is distributed at both ends thereof by heating the object or rapidly fixing the object under vacuum or the like, for example, and the thick film portions can be overlapped and coated in a staggered manner. By repeating the coating so as to shift the distribution 76', 78', 77', and by reducing the liquid pressure, the triangular angle of the liquid film can be reduced, and the thin portion of each pattern can be reduced, thereby forming a fine uneven coating pattern. This method is also effective for a slurry without mixing bubbles. The fuel cell electrode can be formed at a speed 10 times or more that of one two-fluid spray, and the production speed is similarly increased. The coating efficiency is almost 100%, and thus is particularly effective for the formation of electrodes of fuel cells of expensive platinum catalysts. In addition, in the formation of an electrode of a secondary battery, the surface area of the electrode can be improved as compared with a slit nozzle, and therefore, it is effective. The solid content of the fuel cell electrode forming slurry may be 3% or less and the anode may be 1% or less to reduce the amount of platinum per unit area. Of course, if the electrode ink has a low solid content and a low viscosity, it is effective to circulate the bubble slurry mixture at a high speed to prevent the catalyst from settling.

In addition, the invention can also add air auxiliary function in the micro-curtain coating to reduce the flow at the two ends of the coating distribution and increase the flow at the center.

In the present invention, in order to improve productivity, the object can be coated by a slit nozzle having a width of 200 to 2000 mm, for example, in accordance with a high line speed. It is desirable to leave air bubbles, and only the slit nozzle coating is performed. The back roller for supporting the object can be heated. The object moving relative to the slit nozzle may be heated by, for example, heating the back roller to 30 to 200 ℃ and utilizing heat conduction from the back roller, or may be heated while adsorbing the object by the heating adsorption roller, thereby accelerating deaeration of the bubble slurry mixture and evaporation of the solvent. Further, when coating is performed while breaking up bubbles at a constant speed, it is desirable to perform coating while blowing compressed gas from one side or both sides by using a compressed gas assist slit nozzle. By heating the object as described above, the viscosity of the adhesive, the thickener, or the like is reduced, whereby defoaming and evaporation of the solvent can be promoted. In particular, when a solvent having a boiling point of more than 200 ℃ such as NMP is contained, the drying of the coating film surface of the slurry is not promoted, and thus a desired film can be produced. The microbubble-containing state can also be selected by adding a pressure roller immediately thereafter or manually or automatically adjusting the pressure.

In the present invention, the bubble slurry mixture is prepared in advance in a container as a bubble slurry mixture, and the bubble slurry mixture is pumped by a circulation device, returned to a tank through an application device, and applied to an object to form a circulation system.

When the bubble slurry mixture in the container is reduced, the bubble slurry in another spare container can be automatically introduced into the circulation loop, so that the production line does not need to be stopped.

(Industrial Applicability)

According to the present invention, even a slurry which is easy to settle can be made into a bubble slurry mixture to prevent settling of particles and the like, and even a slurry with a low viscosity can be coated in a thin film form because the flow rate of the bubbles is reduced by the same coating amount as the slurry to prevent settling of particles.

(symbol description)

1. 21, 31, 41 container

2. 22, 32, 42 slurries

3. 9, 29, 38, 405 pump

4. 25, 36, 46 compressed gas

5. 23, 24, 35, 45 regulator

6. 26 liquid switch valve

7. 27, 37, 420 gas switch valve

8. 28, 450, 460, 470 mixing device

10. 39, 200, 406 liquid piping (from pump)

33. 43 bubbles

34. 44, 403 stirring device

47. Pipe (lead to the coating device)

48. 101, 102, 201, 202, 301 coating device

49. Piping (from coating device)

51. 61 bubble slurry mixture

52. 62 slit nozzle tip

53. 63, 63' compressed gas flow path

54. 64 bubble expansion

55. 65, 700 objects

56. 66 coating film

71. 71' airless spray nozzle

72. Liquid film (micro screen)

73. Production line

74. Liquid streak

75. Large droplets

76. 76', 78' both ends flow distribution

77. 77' central flow distribution (little)

103. 203, 302 piping (return pump)

104. 204, 303 circulating valves

305. Shade cover

404. Piping (slurry)

407. Piping (gas).

Claims

1. A coating method for applying a liquid containing at least particles or particles and short fibers to an object, the coating method comprising the steps of:

a step of mixing a nonvolatile component containing at least particles or at least particles with short fibers and at least a solvent to make a slurry;

and applying the bubble slurry mixture to an object while eliminating at least a part of the bubbles by an application device communicating with the slurry circulation channel.

2. Coating method according to claim 1,

the slurry has a non-volatile content of 65 wt% or less, a solid particle or particle/short fiber weight ratio of 55 wt% or less, a binder of 10 wt% or less, a volatile content of 35 wt% or more, and a viscosity of 3000 mPas or less.

3. Coating method according to any one of claims 1 to 3,

the slurry has a viscosity of 1000 mPas or less,

4. Coating method according to any one of claims 1 to 3,

the slurry contains a binder, the solvent is composed of at least 2 solvents, at least 1 solvent is a parent solvent of the binder, and the rest at least 1 solvent is a solvent which has a boiling point lower than that of the parent solvent and has an azeotropic effect and a boiling point of 120 ℃ or lower.

5. Coating method according to any one of claims 1 to 4,

at least 80% of gas contained in the bubbles mixed in the slurry is eliminated between the coating device and the object or on the object.

6. Coating method according to claim 5,

the coating device is a spraying device, and a solvent is added from the upstream to the downstream of the spraying device to reduce the viscosity of the slurry and coat the slurry on an object.

7. Coating method according to any one of claims 1 to 6,

the object is a long substrate to be treated by roll-to-roll, and the coating device selects at least 1 kind from a slit nozzle, a compressed gas-assisted slit nozzle, a slot spray nozzle, or a spray head having at least a plurality of two-fluid spray nozzles, which are provided perpendicularly or substantially perpendicularly to the substrate.

8. Coating method according to any one of claims 1 to 6,

9. The secondary battery manufacturing method or the secondary battery according to any one of claims 1 to 7,

the object is a current collector for a secondary battery, and the slurry is a slurry for a secondary battery electrode, thereby forming an electrode of the secondary battery.

10. The all-solid battery manufacturing method or the all-solid battery according to any one of claims 1 to 6,

the object is selected from a current collector, an electrode layer, and a solid electrolyte layer,

the slurry is slurry for electrodes or solid electrolyte slurry.