WO2024075484A1

WO2024075484A1 - Method for applying powder, method for producing secondary battery, method for producing all-solid-state battery, secondary battery and all-solid-state battery

Info

Publication number: WO2024075484A1
Application number: PCT/JP2023/033496
Authority: WO
Inventors: 正文松永
Original assignee: エムテックスマート株式会社
Priority date: 2022-10-05
Filing date: 2023-09-14
Publication date: 2024-04-11
Also published as: JP2024054597A

Abstract

[Problem] An electrode of a secondary battery such as LIB and an electrode of an all-solid-state battery have been formed by: preparing a slurry using an active material, a binder, an electrolyte polymer, inorganic electrolyte particles, inorganic electrolyte fibers, a conductive assistant and a solvent that dissolves the binder and the like; applying the slurry to an object such as a collector; and drying and pressing the slurry thereon. Particularly, since the polymer for the positive electrode is a fluorine-based binder such as vinylidene fluoride, an organic solvent that dissolves the polymer has a high boiling point, and a drying furnace therefor is a large device of more than 100 m and requires a large installation area. Consequently, a device for recovering the solvent is large in size and consumes a large amount of energy, and even a battery for battery cars has involved a big problem in terms of CO2 emissions based on LCA. [Solution] By instantaneously changing a slurry, which is obtained by uniformly mixing electrode mixture materials, into a powder by a dedicated device, the powder particles have the same proportions of the materials regardless of the diameters of the particles. By applying the powder directly to an object, or by applying a powder slurry mainly composed of the powder and a solvent having a low boiling point to an object and volatilizing and recovering the solvent within a short period of time, a denser powder layer is formed. According to the present invention, an electrode can be formed by only performing roll pressing.

Description

Powder coating method, secondary battery manufacturing method, all-solid-state battery manufacturing method, secondary battery, all-solid-state battery

The present invention relates to a powder coating method, a method for manufacturing a secondary battery, a method for manufacturing an all-solid-state battery, a secondary battery, and an all-solid-state battery.
Conventionally, electrodes for secondary batteries such as lithium-ion batteries (LIBs) have often used resin-based binders with a solid content of less than a few percent by weight. Fluorine-based binders such as polyvinylidene fluoride (PVDF) have been widely used, especially for the positive electrode, due to their heat resistance, solvent resistance, and durability.
For LIB electrodes, a composite slurry is made from active material particles, conductive additives, binders, and solvents, which is then applied to a current collector such as aluminum foil, copper foil, or stainless steel foil and dried to form the electrode.For all-solid-state battery electrodes, a composite slurry is made from active material particles, electrolyte particles or fibers, conductive additives, binders, and solvents, which is then applied to a current collector and dried to form the electrode.

However, it is difficult to dissolve fluorine-based and polymeric binders such as PVDF, and only a limited number of special solvents such as normal methylpyrrolidone (NMP) and DMF are available, so the industry has tended to use NMP.
However, these solvents have high boiling points, and the drying equipment on the production line to evaporate the solvent and dry the slurry required an extra-large oven 100 meters long. In addition, the equipment to recover the evaporated solvent required high initial and running costs. As a result, a lot of energy was wasted, so although electric vehicles (EVs) are said to be environmentally friendly, the EV manufacturing process did not contribute much to carbon neutrality.

As mentioned above, conventionally, electrodes for secondary batteries such as LIBs were formed by creating a slurry from active material, binder, conductive additive, and a solvent to dissolve the binder, which was then coated on a moving current collector using a die head and dried. Increasing the coating speed led to huge drying ovens, sometimes reaching a total length of over 100 m. The general power and heat sources for drying ovens are sources of carbon dioxide emissions, and while this can contribute to carbon neutrality (CN) in electric vehicles, it is counterproductive from the perspective of life cycle assessment (LCA).

Patent Publication 2016-100067 WO2014/171535

The objective of the present invention is to contribute to carbon neutrality by converting the manufacturing method of electrodes and batteries, particularly slurry-type, for existing secondary batteries and next-generation secondary batteries in general, particularly all-solid-state batteries, into a dry method or a method equivalent thereto. Another important goal is to reduce the cost per unit watt-hour in terms of manufacturing costs. To achieve this, it is necessary to further pursue resource conservation, energy conservation, and space conservation. It is also necessary to make the total productivity of the products, such as electrode formation and battery cells, at least equivalent to that of conventional methods.
To achieve this, the solvents required for electrode and electrolyte materials must be handled in a small, sealed or nearly sealed space in the limited space of the upstream process, the process must be completed, and the solvent must be recovered.
To solve these problems, research institutes such as universities in the United States are conducting test-scale trials to form electrodes by forming the electrode mixture into a dry (powder) electrode mixture and applying it to the current collector, instead of the wet method of applying the electrode slurry to the current collector and drying it.
Meanwhile, Tesla has disclosed information on a method that is geared towards production lines. Tesla has challenged itself to form electrodes from powder instead of the existing electrode slurry for secondary batteries, and has disclosed information on a groundbreaking dry process for secondary batteries that significantly reduces the total cost.
By applying a powder made of electrode composite particles to a current collector and pressing it with a press roll, the conventional large drying oven is no longer necessary, and since there is no need for a solvent recovery device, the equipment's ground surface area is said to be 1/10 or less.

The dry electrode formation method using powders that does not use solvents when forming electrodes can be ideal because it requires only pressing with a press and can form electrodes with short heating and pressing as necessary, and the installation area is small, and especially when the binder is a thermoplastic resin such as a polymeric fluorine-based resin, there is no need for heating time for crosslinking reaction. The inventor has already proposed a powder coating method and film formation method that are also suitable for LIB electrode formation prior to this information. However, when applying electrode powders or electrode composite materials in powder form on a high-speed production line, the following major challenges are unavoidable and high hurdles. It is common knowledge in the powder particle handling industry (for example, the powder coating industry) that the finer the powder, the fluffier it becomes like cotton candy, and the more severe the agglomeration is, and the more unstable the bulk density is, so it is difficult to supply it stably even with a volumetric supply method. In addition, the binder, which is the resin content of LIB electrode powder, is less than a few percent of the total solids by weight, and especially recently, due to performance improvements, it is less than 1%, which is too large a gap compared to powders for powder coating. Therefore, it was almost impossible to manufacture powders that are close to the ideal spherical shape. For this reason, it was difficult to make the particle size distribution of powder particles uniform for each lot. Therefore, a general volumetric feeder could not be applied to the formation of LIB electrodes, which requires coating weight per unit centimeter area and coating film uniformity. Also, if the resin content is small, it was not possible to apply data for conventional production lines in which the powder is electrostatically charged and electrostatically coated on an earthed object. Even if such powder was transported using a method for adjusting the thickness of the powder supplied by a doctor blade, such as an electric screw-type auger feeder or a volumetric feeder using an electric table, it was not possible to make the coating weight per unit area constant, for example, the electrode weight per unit area equivalent to a film thickness of 60 to 100 ± 2.5 micrometers. Also, when powder particles become an air-powder mixture with a large amount of gas, as typified by cedar pollen and PM2.5 of about 30 micrometers, they behave like aerosols, floating in the air and being affected by the flow of gas. Even if the powder particles of general electrostatic powder coating, which have an average particle size of about 20 to 80 micrometers and are rich in resin, were electrostatically charged, they could not be electrostatically attached to the target object in a high-speed airflow. Even if powder is electrostatically charged and sprayed on an object moving at a speed of several tens of meters per minute or more, for example, 60 meters per minute or more, it is not possible to adhere more than 50% of the powder. This is because the powder flow rides on the air current generated by the object moving at high speed and scatters to places other than the object. Even powder that is forcibly charged with static electricity as described above is overwhelmed by the energy of the high speed wind and large volume of air, so the amount of powder that adheres to the object is extremely small. And the powder is scattered around the area other than the object. General powder coating powder is made of a resin amount that is easily charged with static electricity. On the other hand, binders such as active material particles for forming secondary battery electrodes are insulators, so it was considered that a small amount of less than a few percent of the total solid content, or even less than 1%, is good.
As a result, the electrode composite particles for LIBs and solid-state batteries, which have a low binder content, become unstable in charging, making it even more difficult to apply them to the target object.
Furthermore, as mentioned above, the line speed for slurry coating to form LIB electrodes is high, at over 60 meters per minute, so high-speed powder coating formation using powder instead of slurry was far removed from industry common sense.

Cited Document 1 proposes a method for producing an electrode for a lithium ion battery using a pair of press rolls, the method including a step of applying a binder coating liquid to a substrate, a step of supplying powder containing an electrode active material from a hopper and adjusting it with a squeegee to control the basis weight of the powder and removing the powder supplied outside the electrode width.
The cited document 2 discloses a powder coating method invented by the present inventor and discloses its industrial applicability in the formation of electrodes for secondary batteries such as LIBs.
In both of the methods described in the above documents, there are many difficult factors to apply a fixed amount of powder, unlike liquids. For liquids and molten materials, the coating weight per unit time can be made constant simply by keeping the viscosity, pressure, and nozzle diameter constant. If the temperature of the liquid can be kept constant and the density can be kept constant, the coating weight can be made constant by pumping with a volumetric pump, making it easy to manage. For solutions and emulsions, the coating weight per short period of time, for example, per millisecond, can be made constant by keeping the temperature constant and the above measures constant. However, the electrode slurry is made up of active material particles, conductive additives, binders or binder solutions and solvents, and in the case of solid-state batteries, electrolytes. Since it is a mixture of three or more non-volatile materials with different specific gravities, if the dispersion state is different at the time of discharge, it will cause a fatal defect. Therefore, the longer the distance and time from stable mixing and dispersion to application, the higher the risk. This is because at the manufacturing speed of LIBs at 60 meters per minute, it takes only one second to travel one meter. In other words, if poorly dispersed electrode slurry is applied in just one millisecond, one millimeter will be defective. Therefore, in the present invention, the electrode composite powder is produced in advance with a compact device in which the mixing and dispersion is adequately controlled in milliseconds. The mixing and dispersion device may be a static mixer or the like, and although not particularly limited, an OHR mixer that utilizes centrifugal force and centripetal force to finely disperse, or a dynamic mixer that rotates at high speed to mix and disperse, etc., are even better because they can mix and disperse uniformly and instantly in milliseconds. The average particle diameter of the composite powder should be larger than the particle diameter of the active material. In other words, it should be about 5 micrometers or more. If you want to increase the powder particle diameter, in the present invention, you can create a slurry of small-diameter powder and at least a solvent to create large-diameter powder particles in which multiple powders are aggregated. In the present invention, even if the particle diameter is different, the ratio of each material in the composite is the same, so regardless of the particle diameter of the electrode composite powder, the electrode can be formed by applying it to an object such as a current collector with a powder coating device and pressing it. Therefore, even if it is a powder slurry, the composite ratio is stable regardless of the composite powder particle diameter, so a powder slurry consisting of a poor solvent for the binder of the composite powder, especially a low-boiling point solvent, or a solvent containing a poor solvent, can be created. The poor solvent may be liquefied carbon dioxide gas obtained by liquefying the recovered carbon dioxide gas or a supercritical fluid thereof. The powder slurry is applied to the target object using a die coater or spray coating device, and the poor solvent is evaporated in a short time of seconds to form an electrode powder layer, which is then pressed to form an electrode. The evaporated solvent can be recovered using a small recovery device. If necessary, a small amount of binder solution, binder nanoparticles, or short fibers limited to a few percent or less of the solid content of the electrode may be added to the powder slurry.
In the case of powder slurry, the solvent can be evaporated in a short time of seconds, so the solvent recovery device can be made small, and electrodes can be formed using only a roll press, which has a much greater advantage than the conventional slurry method. However, in battery production lines, it is ideal to form electrodes using only powder slurry or ultimate powder made of a solvent that does not contain organic solvents derived from petroleum. Therefore, in this invention, we propose that the electrode composite slurry is first granulated into powder while recovering the solvent in a compact device upstream of the electrode production line. The upstream includes the process of producing electrode active materials, electrolytes, etc., and is because the composite powder can be produced by consolidating electrode powder for several or several tens of electrode production lines in a relatively small facility.
In the case of all-solid-state batteries, electrolyte materials can be added and mixed. To make a composite for all-solid-state batteries, active material particles and electrolyte core-shell particles can be created, and conductive additives, binders, and solvents can be added to make a composite slurry, which can then be granulated. The dispersed composite slurry can be granulated using centrifugal granulation methods such as high-speed rotating disks and bells, which are in the category of spray dryers, and the granulation process can be performed while causing electrostatic repulsion to prevent blocking between particles during granulation.

Powder particles with little binder tend to crumble during the handling process, and each part of the mixture is likely to fall off. If the particles are not charged, as in Reference 1, the powder will partially crumble with a slight mechanical impact and become fine powder, which will fly away and float, and will be affected by wind currents with typical aerosol fluid behavior. Such fine powder is difficult to attach and fix to the target object. The effect of the binder applied to the target object at the beginning cannot be expected for such fine powder.
Due to the nature of special powders for secondary batteries, it is difficult to keep the powder coating weight per unit area constant. In anticipation of this, Reference 2 devise a method for stabilizing the coating weight per unit area of the final substrate.
In particular, for powders with only a small amount of binder, the bulk density changes not only with the lot but also over time, depending on the physical conditions, such as the weight of the powder itself in the hopper or the dispersion state. In the first place, with such powders, a general volumetric feeder cannot detect the change in bulk density during feeding, and cannot follow it, so the coating weight per unit area cannot be kept constant. Therefore, the coating weight per unit area applied to the substrate changes. Reference 2 proposes a method to solve the problems on the supply side of such powder and granular materials, and as a result, to solve the problems of coating the substrate. However, it does not explain the means to accommodate high-speed line speeds.

If the charging effect is low, the powder will be affected by the flow speed and volume of the gas flow (e.g. compressed gas) that transports it, and the powder that collides with the target object will bounce back along with the gas, resulting in extremely poor coating efficiency. Furthermore, if the air-powder mixture is not uniformly fluidized and dispersed, the agglomerated powder transported by a fixed-volume feeder or the like will be applied as is. Furthermore, as mentioned above, even small mechanical vibrations can cause part of the powder layer to fall off and scatter, and become suspended in the high-speed moving gas flow, making it impossible to solve problems with workability and quality.

In the present invention, for all-solid-state batteries, active material particles and electrolyte particles may be mixed in advance in a dry state to form a core-shell structure, or the mixture may be thin-film laminated in a single device. The conductive assistant and binder solution may be thin-film laminated in separate devices, or the composite may be made into a slurry and a small amount may be thin-film laminated between the core-shell layers to form a uniformly mixed electrode layer. The core-shell particles may be mixed with the conductive assistant and binder to form a composite powder. The composite powder for electrodes may be made into a slurry with a solvent as described above. Alternatively, if necessary, the small particle size granulated powder may be made into a slurry and granulated multiple times to gradually increase the granulated particle size and granulate to the desired particle size to form a powder. In addition, whether it is a LIB electrode composite powder, an all-solid-state battery electrode composite powder, or an all-solid-state battery composite powder consisting of a core shell, even if the binder of the powder is charged, each material other than the binder has a low electrical resistance and is difficult to charge. In addition, if there are conductive assistant protrusions such as carbon fibers present on the surface of the powder particles, they act as antennas for the charged powder particles, and tend to be more prone to discharge.

The present invention has been made to solve the above-mentioned problems, and is as follows: 1. To stabilize the supply amount even for powder whose flow (fuldize) in the air-powder mixture is unstable.
2. Shorten the process from powder supply to coating and eliminate piping and other flow paths as much as possible.
3. Even powders with low electrostatic charging efficiency can be easily attached to objects after charging.
4. Even if the object is moving at high speed, for example 60 meters per minute or more, the structure should be designed to be less susceptible to wind when applying powder.
5. The next process, pressing or hot pressing, allows for high-performance pressing to form electrodes.
To solve the above problems.
Therefore, in the present invention, we have focused on the following:
1. Stabilize the amount of powder sucked or sprayed.
2. The powder is applied to the object by adsorbing, transferring, and releasing it using a porous hollow roll or porous belt.
3. When the direction of powder movement in the gas-powder mixture has stabilized, the excess gas is discharged.
4. The structure must be designed to prevent disturbances when the powder is applied to the target object (especially the coating part of the coating device).
5. To provide a coating method that enables the formation of multiple rows of electrodes using multiple rolls with short face lengths to achieve high precision with a line pressure of up to about 50 kN/cm.

Therefore, in the present invention, 1. The bulk density per square centimeter is made constant in order to make the coating weight per unit area of the powder constant before supply. As an example, the powder on the porous object is sucked from the opposite side of the porous object, the powder layer is leveled to the desired thickness with a squeegee or the like to make the bulk density constant, and then it is configured to be transported. Or, the ejector pump is operated at high pressure in a pulsed manner in milliseconds, and even powder that is difficult to flow on a porous plate is forcibly adsorbed with pulse negative pressure and pushed downstream with a high pressure pulse flow, for example 0.3 MPa or more. The powder is adsorbed to a porous hollow roll or porous belt with negative pressure, moved with a constant bulk density, and the powder is released at the desired location and applied to the target object.
2. The structure is designed so that the wind flow generated by the object moving at high speed does not affect the coating device and the object. When the powder transport is of the powder adsorption roll type or adsorption belt type, the roll or belt is also partially enclosed at the coating position, making the whole of it the coating device, and the structure of the coating device is not affected by external factors.
3. The coating device has an exhaust port for excess gas at least downstream of the coating device, and is designed to exhaust excess gas that affects powder adhesion. The small amount of powder discharged together with the excess gas in the coating device is always the same under the same conditions, so it adheres to the target at approximately the same ratio. Therefore, the amount of powder per unit area on the target adheres at the same ratio as the amount of powder supplied.
4. The electrode is designed to be compatible with wide-width objects, and an electrode powder layer with multiple electrode patterns is formed around the periphery of the uncoated area, allowing the electrode to be pressed with a roll with high press accuracy and a short face length in a later process.
In an all-solid-state battery, the linear pressure of the press roll is required to be as high as about 10 kN/cm to 50 kN/cm depending on the lamination process. Therefore, if a high density thickness of about 100 micrometers is desired after pressing high specific gravity electrode powder onto a thin current collector, for example, about 10 micrometers, the thickness at the time of powder application will be about several hundred micrometers. It is not easy to handle an electrode powder layer that is not fixed at a high speed, for example, 60 m/min. or higher. Therefore, the present invention is not limited to one application and one pressing, but multiple powder applications and multiple pressings or temporary pressings can be performed. Of the multiple pressings, only the final pressing needs to be performed with a high linear pressure. In addition, multiple pressings may be performed by temporarily pressing the entire electrode powder layer of a wide current collector with a single roll with a long face length.

In the present invention, the electrodes on the pre-pressed current collector are slit, and then heated as necessary with a high-performance roll having a short surface length and pressed at high linear pressure for each electrode width. Therefore, it is possible to form multiple stripe electrodes with narrow electrode widths.

The method for producing a secondary battery such as a LIB according to the present invention can be used to form electrodes for secondary batteries in general, electrodes for next-generation secondary batteries such as all-solid-state batteries and air batteries, electrodes for capacitors including electric double-layer capacitors, and further, by combining a dry method and a wet method, electrodes for fuel cells and water electrolysis, and microporous layers for gas diffusion layers can be formed. Furthermore, the method can be suitably applied to the fields of powder coating and powder adhesion for general metal flat plates, long plates, nonwoven fabrics, films, etc. Furthermore, each layer of a next-generation solar cell power generation layer can be formed by applying nano-sized or submicron fine powder that does not require a binder directly or in powder slurry form.
Therefore, the present invention is as follows.

The present invention provides a method for applying powder to a moving grounded object, comprising the steps of: filling a porous object with powder; stabilizing the weight of powder sucked in per second when sucking the powder and moving it downstream; sucking the powder through a suction port and transporting it as an air-powder mixture to a nozzle that communicates with a flow path by a pressure difference; discharging excess gas from the air-powder mixture to the outside midway through the flow path to increase the powder density per volume in the downstream flow path; connecting the nozzle to a powder application device, the inside of which is an opening facing the moving object and which is made of a structure with a space through which the powder flow moves; electrostatically charging the powder from the time of suction until it adheres to the object; and applying the powder to a moving object that is in contact with or close to the opening of the powder application device, which is grounded.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, which includes the steps of: filling a porous body with electrode powder; stabilizing the weight of the powder sucked in per second when sucking the powder and moving it downstream; sucking the powder through a suction port and transporting it as an air-powder mixture to a nozzle that communicates with a flow path by a pressure difference; discharging excess gas from the air-powder mixture to the outside midway through the flow path to increase the powder density per volume in the downstream flow path; connecting the nozzle to a powder coating device, which has an opening on the side facing the moving object, and has a structure with a space through which the powder flow moves inside the powder coating device, and electrostatically charging the powder between the time of suction and the time of attachment to the object; attaching the powder to an earthed object that is in contact with or in close proximity to the opening of the powder coating device to form a powder electrode layer; and pressing the powder electrode layer with a roll to form an electrode.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the method for stabilizing the suction weight of powder per second during suction of the powder is performed by operating an ejector pump with a compressed gas of 0.3 MPa or more and a pulse opening and closing of 10 cycles or more per second when sucking and pumping the powder on the porous body with the ejector pump.

The method of the present invention for stabilizing the suction weight of powder per second during suction of the powder provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that when sucking powder with a constant bulk density into a recess of a porous object, negative pressure is applied to the porous surface opposite the recess, and the powder is volumetrically filled into the recess to make the bulk density of the powder in the recess constant, thereby stabilizing the bulk density of the powder in the recess per volume.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the position of the flow path for discharging excess gas from the gas-powder mixture is upstream of the point where the cross-sectional area of the flow path is reduced to 1/4 or less, and the powder density of the downstream flow path with the smaller cross-sectional area is increased to move the powder.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that at least one corona electrode or elongated electrode is arranged in a shape corresponding to a wide area in the space inside the powder coating device of the present invention, the powder is charged, at least both sides and the wall of the upstream part of the space are made of a material that electrostatically repels the charged powder, and the wall is structured to block the flow of external wind with the object moving in contact with or close to the object side end of the wall, at least the walls on both sides in the moving direction of the object regulate the flow of the powder flow to cause the powder to adhere to the object, the space is extended downstream, the powder that does not adhere to the object is electrostatically repelled or recharged by the corona electrode located downstream, increasing the chance of it adhering to the object as it moves downstream, and at least the excess gas inside the coating device is discharged from the most downstream exhaust port of the powder device.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that a plurality of partitions are provided on the inside of both side walls of the coating device, and a single or multiple nozzles are provided between the partitions, and the partitions form a plurality of stripe-shaped powder electrode layers and uncoated areas in the width direction perpendicular to the target object.

The present invention provides a method for manufacturing a secondary battery, which is characterized by a step of vacuum-sucking the powder scattered in the electrode uncoated area between the powder layer electrodes in the moving direction of the object along the width of the electrodes and discharging it to the outside, and further vacuum-sucking the powder other than the electrode pattern on the object perpendicular to the electrodes in the moving direction of the object to form the electrode uncoated area, thereby forming the powder uncoated area and the powder electrode pattern layer.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the electrode is formed by stacking powder on an object and pressing with a roll multiple times, and at least in the final press, the object and the powder layer are heated to a temperature equal to or higher than the softening point of the binder contained in the electrode powder, and pressed with a linear pressure of 10 kN/cm or more to form an electrode.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that in the roll press process for laminating the current collector, negative electrode layer, electrolyte layer, positive electrode layer, and current collector, which is a subsequent process for forming the electrodes, the roll temperature or powder temperature is heated to a temperature equal to or higher than the softening point of the binder or electrolyte polymer contained in the electrode powder, and pressed with a linear pressure of 10 kN/cm to 50 kN/cm.

The present invention provides a method for producing a secondary battery or an all-solid-state battery, characterized in that the electrode powder is a powder granulated from at least one selected from among active material particles for electrodes, electrolyte particles or fibers, binders, electrolyte polymers, conductive assistants, and core-shell particles obtained by dry granulation of active material particles and electrolytes.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, which is characterized in that, before applying electrode powder to the current collector of the object of the present invention, a dispersant is added to a conductive assistant consisting of carbon nanotubes or carbon nanofibers, and then a binder solution or a slurry consisting of binder fine particles having an average particle size of 0.1 micrometers or less and a poor solvent is selected and added to the current collector, and the liquid having a solid content of 1.5% or less is applied to a wet thickness of 15 micrometers or less.

The present invention provides a method for applying powder to an object by sucking in the powder supply position of a porous hollow roll rotating in the moving direction of the object, depositing and stacking the powder on the outer periphery of the roll, and releasing the powder at the application position to the object, by creating a negative pressure inside the roll at the powder loading position to suck in the powder and deposit the powder on the surface of the roll to form a powder layer and stabilize the bulk density of the powder layer, providing an electrostatic charging means between the roll and the object to charge the powder, releasing the powder from inside the roll at least at the closest position to the roll of the object by compressed gas, earthing the powder on the surface of the roll and depositing it on the moving object, and providing an enclosure means with an exhaust port for excess gas between the roll and the object to prevent the influence of wind from the outside and the outflow of the powder to the outside of the application device.

The present invention provides a powder application method characterized in that a hollow roll into which the powder is filled has at least one porous recessed shape, the powder is filled into the recessed portion while being sucked from the hollow side of the roll, and in an application device located close to the object, the powder in the recessed portion is sprayed from the hollow side by positive pressure gas to apply it to the object.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the powder is applied to an object by sucking the powder at a supply position of the electrode powder of a porous hollow roll rotating in the moving direction of the object, depositing and stacking the powder on the outer periphery of the roll, and releasing the powder at a coating position for the object, by applying the powder to the object by applying a negative pressure inside the roll at the powder loading position to suck the powder and deposit the powder on the surface of the roll to form a powder layer and stabilizing the bulk density of the powder layer, providing an electrostatic charging means between the roll and the object to charge the powder, at least at the closest position of the object to the roll, releasing the powder from inside the roll with compressed gas, and depositing the powder on the surface of the roll to the moving object while being grounded, and applying the powder to the object, and providing an enclosure means with an exhaust port for excess gas between the roll and the object as a coating device to prevent the influence of wind from the outside and the outflow of the powder to the outside of the coating device.

The present invention provides a method for applying powder to an object by applying a powder on a porous belt that rotates in the direction of movement of the object, comprising the steps of: applying negative pressure to the opposite side of the belt at a powder supply position to suck in the powder and deposit the powder on at least the belt surface; charging the powder between the belt and the object with an electrostatic charging means; detaching and earthing the powder on the belt at an application position for the object to deposit the powder on the moving object; and providing an enclosure with an exhaust port for excess gas between the belt and the object at the application position to prevent the effect of wind from outside and the outflow of powder to the outside as an application device, thereby applying powder to the object.

The present invention provides a method for manufacturing a secondary battery or an all-solid-state battery by applying an electrode powder on a porous belt that rotates in the moving direction of the object to the object to form an electrode, comprising the steps of: applying a negative pressure to the opposite side of the belt at the powder supply position to suck in the powder and attach it to at least the belt surface; charging the powder between the belt and the object with an electrostatic charging means; removing and earthing the powder on the belt at the application position to the object to attach the powder to the moving object; and providing an enclosure with an outlet for excess gas between the belt and the object at the application position as an application device to prevent the influence of wind from the outside and the outflow of the powder to the outside, thereby applying the electrode powder to the object to form an electrode.

The composite material for electrodes of secondary batteries and all-solid-state batteries of the present invention can be made into particles by mixing at least active material particles for electrodes, inorganic electrolyte particles, inorganic electrolyte fibers, inorganic fine particles, binders, electrolyte polymers, and conductive assistants. The particles can be made into particles by mixing multiple materials and granulating them, or by coating the core particles with a liquid such as a slurry or solution containing a single or different materials to encapsulate them. Alternatively, the active material particles can be dry-coated with electrolyte particles to make particles with the active material particles as the core and the electrolyte as the shell. A milling method or mechanochemical method in which multiple fine particles, such as nanoparticles, are mixed and made into particles can also be used. In the present invention, regardless of the means of making the particles, these particles will be referred to as composite particles or mixed particles hereinafter.

Normally, polyvinylidene fluoride (PVDF) is often used as an electrode binder for lithium-ion batteries, and only limited high-boiling solvents such as normal methylpyrrolidone (NMP) and DMF can dissolve it. Therefore, problems such as cracks occurring when a thick film is formed due to the long drying time after application of electrode slurry, etc. have occurred. In the present invention, the binder is foamed with gas in advance to increase its volume and expand the bonding area. Therefore, a binder with elasticity has the effect of filling the voids between active material particles together with fine active material particles and conductive assistant. For this reason, polyethylene oxide (PEO), which is used as an electrolyte polymer, can be mixed with PTFE or PVDF to lower the melting point and mix gas to obtain a foamed binder. The active material and electrolyte particles granulated by this method can be handled and applied as powder. In addition to the above method, application can be performed with high precision by using Patent No. 6328104 and Patent No. 6481154, which the inventor invented and holds the rights to.

When applying as a powder, a film can be formed by pressing after application, or by heating to a temperature above the softening point of the binder and pressing after laminating the electrolyte layer and counter electrode.
The powder can be made more fluid by using a matrix of high molecular weight PVDF, PTFE and PEO or by mixing them together, and further mixing them with ceramic fine particles. Oxide-based electrolyte particles and sulfide-based electrolyte particles can be used alone or mixed with the binder or electrolyte polymer. In the present invention, a poor solvent, recovered liquefied carbon dioxide gas or its supercritical fluid is added to make a slurry, which is then sprayed onto a heated object, allowing instantaneous dry coating that is denser than powder coating, and the desired coating film can be obtained.

On the other hand, sulfide-based electrolytes, such as argyrodite-based electrolytes, have good ionic conductivity, but require a dehumidified atmosphere with a dew point of -50°C or even -70°C or lower, or the filling of an inert gas such as argon gas, which tends to increase the size of the equipment.
Therefore, in this invention, not only can the compact device apply powder and press or heat press, but also the DRY on WET method, which enhances the adhesion of the powder, can be used. A conductive assistant such as carbon nanotubes, a dispersant that has an anchoring effect on the target object, binder fine particles or short fibers with a low solid content, and a slurry made of a solvent mainly composed of a poor solvent for the binder are applied, and then the powder is applied and heat pressed to create a dry electrode layer with high adhesion to the interface with the target object.

As described above, conventional electrodes for secondary batteries and all-solid-state batteries were formed by mixing a mixture of materials selected from at least electrode active material particles, inorganic electrolyte particles, inorganic electrolyte fibers, inorganic fine particles, fluorine-based binders, polymeric ion-conductive electrolyte polymers, and conductive assistants with a high-boiling point solvent such as NMP that can dissolve PVDF, etc., to form a slurry, which was then applied to objects such as current collectors. For this reason, high-speed secondary battery production lines required long drying ovens of around 100 m.
This required a huge amount of space for the factory, as well as energy for powering and drying the process.
In the present invention, a selected mixed material from the above-mentioned electrode materials for secondary batteries, etc., is handled as a particulate powder, which is applied to an object such as a current collector, and then heated to above the softening point of the thermoplastic or electrolyte polymer, or above the melting point if possible, and pressed to form an electrode.
However, powders that are not smooth and suitable for powder fluidity, such as binders and electrolyte polymers, for example polymers such as PEO, can be mixed with other hard polymers, such as PTFE or inorganic fine particles, and handled as polymer particles. The inorganic fine particles can be oxide-based electrolyte particles, sulfide-based particles, or fibers. A mixture of these is also acceptable. In particular, they can be added to the outside of polymer particles to increase fluidity. Therefore, the contact between the active material particles and the electrolyte can be resolved by the stretching of the polymer by pressing, which also solves the problem of voids. In the case of composite particles, it is even better to foam the polymer.

1-2 is a schematic cross-sectional side view of a powder coating unit for coating an object with electrode powder according to an embodiment of the present invention. 2-1: A schematic cross-sectional plan view of multiple powder nozzles, an electrostatic electrode, and a gas or powder flow outlet according to an embodiment of the present invention. 2-2: A schematic cross-sectional plan view of an embodiment of the present invention in which multiple partition sections are provided in parallel in the direction of movement of the target object in the application section. 2-3: A schematic cross-sectional side view of a powder application section according to a practical embodiment of the present invention. 1 is a schematic cross-sectional side view of a powder coating unit according to an embodiment of the present invention, showing how powder is applied to an object moving below the powder coating unit. FIG. 2 is a schematic cross-sectional side view of a target object, a powder layer, and a press roller according to an embodiment of the present invention. 1 is a schematic cross-sectional side view of an embodiment of the present invention in which an electrode liquid, for example a slurry, is applied to an object and then powder coating is performed thereon. The bottom surface of the powder coating unit according to the embodiment of the present invention is a rotating body. The rotating body can have a porous surface, and compressed gas can be added to the coating unit to fill the powder. The bottom surface of the powder coating unit according to the embodiment of the present invention is a circulating belt, and the belt is porous so that compressed gas can be added to fluodize the powder. 1 is a schematic cross-sectional view showing the supply of powder to a porous roll and the application of the powder to an object by separation of the powder within a coating device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the supply of powder to a porous belt, the separation of the powder within a coating device, and the coating of the powder onto an object in an embodiment of the present invention. FIG.

The following describes a preferred embodiment of the present invention with reference to the drawings. Note that the following embodiment is merely an example to facilitate understanding of the invention, and does not exclude additions, substitutions, modifications, etc. that can be implemented by a person skilled in the art within the scope of the technical concept of the present invention.

The drawings show a schematic representation of a preferred embodiment of the present invention.

In FIG. 1, powder is applied onto an object 1 through a suction port 3 of a powder pump 4 such as an ejector pump.
The gas is sucked in through the flow passage 5 and is forced out into the flow passage 5. The flow passage 5 may be a pipe or tube with an inner diameter of about 6 mm to 12 mm, such as a metal pipe, rubber, ceramics, or plastic. The flow passage 7 beyond the flow passage 5 can be narrowed to enrich the powder density of the powder fluid. By enriching the powder ratio and smoothly moving the powder into the narrow tube, mainly excess gas can be discharged to the outside from the outlets 6, 6'. The outlets 6, 6' are connected to a mini cyclone (not shown) or the like, and the powder mixed in the surplus gas can be collected and reused. The tube with a narrow inner diameter can also be a tube made of PTFE or PFA with an inner diameter of about 4 mm to 2 mm. It can be 1 mm or 5 mm. In order to facilitate frictional charging of the powder, the tube can be made of a material that is easily charged with binders, electrolyte polymers, etc. For example, if the powder is a polyamide-based powder such as nylon, the inner surface of the tube should be PTFE, and efficient frictional charging can be achieved by earthing the outer surface of the tube. Generally, from the viewpoint of heat and chemical resistance, the positive electrode binder of a secondary battery is fortunately mostly fluorine-based, and the active material is hard and easy to scrape the inner surface of the tube, but in order to ignore contamination due to wear on the inner surface of the tube, a fluorine-based tube with good slipperiness of powder such as PTFE or PFA is selected, and the powder can be ionized by ionizing the gas in the atmosphere with a corona electrode and ionizing the powder that comes into contact with it. When charging, the negative electrode is good for ionizing air (mainly oxygen), and the positive electrode is good for charging nitrogen. In addition, regardless of whether the inner diameter of the flow path is narrowed in the middle, the present invention provides exhaust ports 6, 6' that allow excess gas to escape from the middle of the flow path, and the powder from the nozzle 8 can be made powder-rich. The exhaust can be evenly released around the entire circumference outside the tube, and the excess gas can also be released from one or more exhaust ports 6, 6'. If an exhaust means is provided immediately before narrowing the inner diameter of the flow path tube, the exhaust of excess gas becomes more effective. If the inner diameter of the tube suddenly changes from a large diameter to a small diameter, the powder fluid containing a large amount of compressed gas cannot flow into the small diameter tube and flows back to the ejector pump side. Therefore, it is important to make a powder-rich fluid while discharging the excess gas to the outside from the exhaust port 6, etc., and send it into the thin tube. The excess gas can be discharged by natural exhaust, and the powder mixed in the gas can be collected and reused using a small cyclone device (not shown). When changing from a large diameter to a small diameter, the tube should be gradually tapered to ensure a smooth flow.
The powder is ejected from the nozzle 8, charged by electrostatic electrodes 11, 11', 11'' arranged in the powder coating section 16, flows out from the end 15 of the powder coating section 16, and adheres to the object 12 moving close to the end 15. The nozzle 8 may be angled toward the object 12 so that the powder collides with it and adheres to it. The electrostatic charge may already be charged in the flow path upstream of the nozzle or on the object 1 upstream of that. The object 12 may be placed via a conductive object such as a metal roll, and the end 15 and the object may be at a level where they are almost in contact, which may be about 0.5 to 3 mm. Therefore, even if the object moves at high speed, the wind flow that affects the adhesion of the powder can be prevented by a wall or the like and can be ignored. Furthermore, the powder is charged, and therefore the powder can be efficiently attached to the object in the powder coating section 16. The unattached powder and air flow move downstream, including the bottom 14, so the excess air flow and the powder that did not adhere to the object 12 are discharged by suction from the discharge port 10, and the powder is recovered and reused.

In FIG. 1-2, the powder is ejected from the nozzle 8, moves along the walls 9, 9' on both sides, and is charged by the electrostatic discharge section, and the excess gas and powder that does not adhere to the object are sucked in and discharged from the discharge port 10. There is no limit to the number of nozzles. It can be one or more. There is no limit to the distance between the walls, but if you want to form the electrodes in a narrow stripe shape, it is better to set it to about 5 to 30 mm per nozzle. If you want to have electrodes with a wide width, you can install the desired number of powder coating sections in parallel. Also, if you want to coat an object such as a collector that moves at high speed, it is better to make the powder coating section longer in the direction of movement of the object and keep the contact time of the powder longer, so that the powder can be attached more efficiently. If the moving speed of the object is 60 m per minute, a length of 0.5 to 1 m or more is good. In this way, the contact time between the object and the powder will be 0.5 to 1 second or more. If the particle size of the powder is large and the specific gravity is heavy, the bottom can be made porous and gas can be added to move it while it flows. The discharged powder can be sucked up and collected using a cyclone device (not shown) and reused.

In FIG. 2, powder is ejected from the nozzles 28, 28', 28'', and moves while being restricted in the lateral direction by the walls 29, 29', becomes charged at the electrostatic discharge parts 21, 21', and adheres to the object moving above it (not shown). Static electricity is generated by an electrostatic generator (not shown) and is connected to an electrostatic cable 22 made of a conductor with resistance covered with an insulating material. In the case of a metal wire with low resistance, sparks may occur when the metal foil of the object comes into contact with it, so a material with resistance that does not allow the current to flow suddenly and does not spark should be selected. In addition, a thin corona pin is suitable for the discharge point, and the discharge current is at the microampere level, for example, 50 microamperes, and the voltage is adjusted to a range of about 20,000 to 700,000 volts. In addition, polypropylene or other materials to which charged powder does not easily adhere due to electrostatic repulsion should be selected for the walls 29, 29' and the bottom 26 of the powder coating part. The desired number of nozzles can be selected from, for example, 1 to 100. In addition, the nozzles can enter the powder coating part, and the walls can be processed to make them into nozzles.

In Figure 2-2, partitions 25, 25' can be provided between walls 29, 29' for the desired number of nozzles. The main purpose of the partitions is to regulate the widthwise flow of powder downstream between the wide walls and move it into a laminar flow. There may be one or more nozzles between partitions 25, 25' and the walls. The partitions can regulate the flow of powder in the direction of movement of the object. On the other hand, the tip in particular should be as thin as possible so that the partitions do not become a shadow and inhibit the powder from adhering to the object (not shown).

In Figure 2-3, the end of the partition 25 is located away from the wall end 209 so as not to interfere with adhesion to the target object. The bottom 24 is made porous and can be made into a powder fluidized bed by introducing compressed gas from the outside. Therefore, the powder that is sprayed out from the nozzle 28 and settles at the bottom can be moved while being fluidized. Excess gas and powder that does not adhere to the target object (not shown) can be sucked in from the discharge port 20 and transported to a cyclone (not shown) for recovery and reuse.

In Figure 3, powder is sprayed from the nozzle 38 of the powder application section located above the moving object 32, charged by the electrostatic discharge section 31, and falls or adheres to the object 32 in a directional manner to form a powder layer 102. Excess gas from the sprayed air-powder mixture and powder that does not adhere to the object are sucked in from the discharge port 30, allowing the powder to be collected. The position of the discharge port 30 is not limited. With this positional relationship, there is also no need to provide a special compressed gas-based filling function at the bottom 34 for powder fluidization.

In Fig. 4, the powder layer 202 applied to the object 42 is moved to the pressing means 45, 45' and pressed. The pressing means may be heated, for example, a roll-type pressing means having an induction heating function. The roll pressing means may be a line press in the roll width direction. Since the pressing only needs to fix the powder until the next process, heating and pre-pressing to raise the binder above its softening point are sufficient.
Therefore, when there is a small amount of binder, etc., the powder surface before pressing can be prevented from moving by evaporating it at 200°C or less or in a vacuum until the final heating and pressing process, or the object can be temporarily fixed by applying a viscous monomer or liquid plasticizer that is not a problem if it remains.

5, a liquid is applied to a moving object 52 by a liquid application device to form a liquid coating layer 350. In the next step, electrode powder is applied by a powder application device 310 to form a powder coating layer 302.
The liquid may be a slurry for electrodes. It is desirable that the liquid easily penetrates into the gaps of the powder layer to be applied in the next process, is easily wetted, and evaporates instantly by heat or vacuum. In addition, in order to form a dense interface with the target object, it is desirable that the particle size of the electrode composite particles is smaller than the particle size of the powder. In the present invention, a liquid can be applied on the powder coating layer in the form of a thin film of a slurry or the like having a smaller average composite particle size or made of electrolyte particles using a liquid application device (not shown). The purpose is to improve the smoothness of the electrode or to form fine irregularities to improve the surface area. Therefore, a more uniform surface can be formed by applying the slurry or the like on the powder layer after hot pressing.

In Figure 6, the air-powder mixture is ejected from an ejection port 68, charged by an electrostatic discharge section 61, and adheres to an object 62. Excess air and powder that does not adhere to the object are sucked through an exhaust port 60, and the collected powder can be reused. This method uses a roll 64 instead of the bottom of the powder coating device. The roll 64 can be rotated.

7 is a diagram showing the configuration of a powder coating device for coating a moving object 72 with powder. Powder is ejected from a powder ejection port 78 and adheres to the object. Excess gas and powder that has not adhered to the object are sucked from an exhaust port, and the collected powder can be reused. The bottom of the powder coating device is a belt 74 that moves in the direction of movement of the object.
The belt may be porous, for example a screen belt with fine openings, and pressurized gas may be applied to the belt 74 outside the coating device to form a full die structure at the bottom of the powder coating device to prevent the powder from accumulating at the bottom. Excess gas used in full die can be sucked out from the exhaust port.

In FIG. 8, the roll is a hollow roll 84, and the hollow roll 84 is made porous, so that the inside 830 of the porous part of the hollow roll 84 can be made negative pressure at the position of the powder supplying device 802, and the powder can be attached to the surface of the roll. In addition, the gap between the rolls can be adjusted with a squeegee 801 to obtain a desired powder layer thickness with a stable bulk density. If the thickness of the lithium iron phosphate electrode powder after pressing is about 150 micrometers and the true specific gravity is about 2.3, the bulk density of the powder before supply is 0.8 to 0.9, so the powder layer thickness is about three times as thick, 450 micrometers. Such low bulk density powder falls when moved by a rotating body or the like, so it is necessary to further increase the bulk density by sucking it with a vacuum from the other side on a porous body. The powder layer with increased bulk density is moved to powder coating device 810, and since the roll can be structured so that compressed gas is fed from inside the roll at least closest to the object 82 or at a desired position, a positive pressure 820 is created inside the hollow space, causing the powder on the roll to be released and coated from below onto the object 82 moving above coating device 810. The powder is charged and earthed by static electricity generator 81, and adheres to the moving object to form a powder layer.
If the gas used to spray the powder can be given directionality, it becomes surplus gas after coating and can be discharged from the exhaust port 80. Discharge may also be by suction. The coating device 810 can also prevent the flow of gas generated by the movement of the target object 82 outside the device. Therefore, the coating device 810 and the target object 82 can be close to each other by a few millimeters or less. At least the upstream side of the coating device can be in contact with each other.
The small amount of powder discharged together with the excess gas during suction can be recovered and reused. The powder flow inside the coating device 810 is not affected by the wind flow outside the device, so a powder layer can be efficiently formed on the object 82 moving at high speed. A desired number of combinations of powder coating device 810, roll 84, and powder supply device 802 can be installed in the direction of movement of the object and stacked. Powder of the same type can be stacked, or different types of powder can be stacked. For example, in the case of an all-solid-state battery, the charge/discharge performance can be improved by increasing the amount of electrolyte as the ratio of active material to electrolyte increases with distance from the current collector and applying at an angle.
If it is desired to increase the amount of powder supply, for example, a groove of the electrode width can be formed around the porous hollow roll, and a recess can be formed on the cross section of the roll. Therefore, since the desired number of recesses can be formed and the powder can be adsorbed and filled in the porous parts in the same way, it is also possible to fill a large amount of powder depending on the shape of the recesses and apply the powder to the object in a thick film. The hollow roll 84 and the application device 802 can be reversed to move the object 82 moving under the application device with the opening facing downward, with the powder adsorbed to the porous roll or grooves at the top of the roll, and the powder can be released at the bottom and applied to the object. The powder can be released and applied to the object in either direction. The speed of the object and the rotation speed of the outer periphery of the hollow roll can be made constant, and the coating weight per unit area can be made constant by following the speed of the object moving roll-to-roll.

In FIG. 9, a powder layer with a stable bulk density can be formed on the surface of a porous belt 94 that rotates in synchronization with the moving direction of the object by supplying powder 900 by a powder supplying device 902 at a desired position and applying negative pressure to the opposite side of the belt. A powder layer of a desired thickness can be formed on the belt by adjusting the gap with a squeegee 910. The powder supplying device 902 may be an auger feeder or the like, and the powder may be fluidized in a fluidized bed to adhere to the belt, or the powder may be sprayed to adhere. Therefore, the means of supply and adhesion are not limited. The powder layer moves together with the belt 94 and enters the powder coating device 901. At a desired position facing the object 92, compressed gas is discharged from the opposite side of the belt, and the powder on the belt 94 is separated, and the charged powder is grounded by static electricity generating devices 91, 91' and applied to the moving object to form a powder layer. A plurality of compressed gas ejection devices 920, 920' may be arranged in the belt moving direction to separate the powder on the belt and make it adhere to the object, or the powder may be ejected in a pulsed manner to coat the object with multiple layers of powder.
If the compressed gas used to eject the powder can be given directionality, it becomes surplus gas and can be discharged from the exhaust port 90. Discharge can also be achieved by creating negative pressure and sucking. The coating device 910 also serves to prevent wind currents caused by the movement of the target object 92 outside the device. For this reason, this can be achieved by coating the target object with at least contact between the upstream part of the coating device 910 and the target object or by keeping the distance between the upstream part and the target object within a few millimeters.
A desired number of combinations of powder coating devices 910, belts 94, and powder supply devices 902 can be installed in the direction of movement of the object and stacked. The powder can be the same type, or different types of powder can be stacked. For example, in the case of an all-solid-state battery, the ratio of active material to electrolyte can be increased as the amount of electrolyte increases with distance from the current collector, and gradient coating can be used to improve charge/discharge performance. At least temporary pressing can be repeated for each layer.
In the present invention, the surface opposite to the porous belt on the powder supply side is subjected to negative pressure and suction, so that the bulk density of the powder layer can be made constant. In the present invention, the side of the target object 92 is open, and an excess gas exhaust port 90 is provided downstream of the coating device 910 that encloses the powder layer moving on the belt 94, and the excess gas is exhausted through the exhaust port 90, so that the powder can be prevented from scattering to places other than the desired place on the target object.
The small amount of powder discharged from the exhaust port can be sucked up and collected using a mini cyclone or similar device for reuse.

As described above, the gist of the present invention is to make a powder of composite particles of a composite material for secondary battery electrodes, which includes an all-solid-state battery electrode, and apply the mixture to an object such as a current collector while preventing the powder from agglomerating into a desired ratio, and then heat it as necessary in a short press to form an electrode. In order to increase the adhesion of the powder to the object and to increase the adhesion of the interface with the object, which is the current collector, a surfactant, a dispersant, etc. can be selected and mixed with a resin such as a binder with a small amount of anchor effect dissolved or dispersed in a solvent that evaporates in a later process and applied. In addition, in order to improve the density with the object such as the current collector, a powder of fine particles smaller than the average particle size of the powder of the active material, etc. can be mixed. Furthermore, a slurry of the electrode material in which the binder has been dissolved or swollen can be applied. After the electrode powder layer is formed, the solvent or a plasticizer that can evaporate in a later process can be applied in a small amount to the surface of the powder layer to fix the powder layer until the pressing process. The powder-coated surface that comes into contact with the electrolyte layer can be provided with a micron-level fine uneven surface to increase the surface area and improve adhesion with the electrolyte layer, so fine powder can be applied to at least one side of the electrode layer and electrolyte layer.

As described above, the present invention allows the formation of electrodes for secondary batteries. It is even possible to form electrodes for all-solid-state batteries and semi-solid-state batteries. As described above, the manufacturing method for secondary batteries such as LIBs can be used to form electrodes for secondary batteries in general, electrodes for next-generation secondary batteries such as all-solid-state batteries and air batteries, for example, electrodes for capacitors including electric double-layer capacitors, and further, by using the dry method and the wet method alone or in combination, to form electrodes for fuel cells and water electrolysis, and microporous layers for gas diffusion layers. Furthermore, it can be suitably applied to the coating and adhesion of powder to general metal flat plates, long plates, nonwoven fabrics, films, etc. Furthermore, the use of nano-sized or submicron fine powders can further expand the field of application, and it can be used to form each layer of next-generation solar cells, for example.

1 Object 2 Powder 3 Suction port
4 Pump 5

Flow path

6, 6 Excess gas exhaust port 7

Second flow path

8, 28, 28', 28'', 38, 58, 68, 78

Spout

15, 209

Wall end

9, 9', 19, 19', 29, 29'

Wall

10, 20, 20', 20'', 30, 50, 60 Excess

gas exhaust port

70, 80, 90 Excess gas exhaust port 64 Roll (bottom of powder coating device)
74, 94 Belt (bottom of powder coating section)
11, 11', 11'', 21, 21', 21',

electrostatic generator

31, 61, 61', 81, 81', 91, 91'

electrostatic generator

12, 32, 42, 52, 62, 72, 82, 92 target object (current collector)
13, 33, 33' Roll (ground)
14, 24, 34 Powder coating section bottom 22 Electrostatic cable 25, 25' Partition section 45, 45' Pressing means 101

Powder flow

102, 202, 302 Powder coating layer 110, 310 Powder coating section 320 Liquid (slurry) coating device 350 Liquid coating layer 302 Slurry/powder coating layer (DRY ON WET)
800, 900

Powder

801, 901

Squeegee

802, 902 Powder supply device

Claims

A method for applying powder to a moving grounded object, comprising the steps of: filling a porous object with powder; stabilizing the weight of powder sucked in per second when sucking the powder and moving it downstream; sucking the powder through a suction port and transporting it as an air-powder mixture to a nozzle that communicates with a flow path by a pressure difference; discharging excess gas from the air-powder mixture to the outside midway through the flow path to increase the powder density per volume in the downstream flow path; a powder coating device with an opening facing the moving object has a structure with a space through which the powder flow moves, and communicating the nozzle to the coating device; electrostatically charging the powder from the time of suction until it adheres to the object; and applying the powder to a moving object that is in contact with or close to the opening of the powder coating device.
A method for manufacturing a secondary battery or an all-solid-state battery, comprising the steps of: filling a porous body with electrode powder; stabilizing the weight of powder sucked in per second when sucking the powder and moving it downstream; sucking the powder through a suction port and transporting it as an air-powder mixture to a nozzle connected to a flow path by a pressure difference; discharging excess gas from the air-powder mixture to the outside midway through the flow path to increase the powder density per volume in the downstream flow path; connecting the nozzle to a powder coating device, the inside of which is a structure with a space through which the powder flow moves, and the surface facing the moving object is open, and the inside of the powder coating device is open, and the structure has an opening through which the powder flow moves; electrostatically charging the powder between the time of suction and the time of attachment to the object; attaching the powder to an earthed object that is in contact with or in close proximity to the opening of the powder coating device to form a powder electrode layer; and pressing the powder electrode layer with a roll to form an electrode.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that the method for stabilizing the suction weight of the powder per second during suction of the powder is performed by operating the ejector pump with a compressed gas of 0.3 MPa or more and a pulse opening and closing of 10 cycles or more per second when sucking and pumping the powder on the porous body with the ejector pump.
The method for stabilizing the suction weight of powder per second during suction of the powder is characterized in that, when sucking powder with a constant bulk density in a recess of a porous object, the porous surface opposite the recess is subjected to negative pressure, the powder is volumetrically filled in the recess, and the bulk density of the powder in the recess is made constant, thereby stabilizing the bulk density of the powder in the recess per volume, according to the method for manufacturing a secondary battery or an all-solid-state battery of claim 2.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that the position of the flow path for discharging the excess gas from the gas-powder mixture is upstream of the point where the cross-sectional area of the flow path is reduced to 1/4 or less, and the powder is moved by increasing the powder density in the downstream flow path with the smaller cross-sectional area.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that at least one corona electrode or an elongated electrode is arranged in a shape corresponding to a wide area in the space inside the powder coating device to charge the powder, at least both sides and the wall of the upstream part of the space are made of a material that electrostatically repels the charged powder, and the wall is structured to block the flow of external wind with the object moving in contact with or close to the end of the wall on the object side, at least the walls on both sides in the moving direction of the object regulate the flow of the powder flow to cause the powder to adhere to the object, the space is extended downstream, the powder that has not adhered to the object is electrostatically repelled or recharged by the corona electrode located downstream to increase the chance of it adhering to the object as it moves downstream, and at least the excess gas inside the coating device is discharged from the most downstream exhaust port of the powder device.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that a plurality of partitions are provided on the inside of both side walls of the coating device, and a single or multiple nozzles are provided between the partitions, and a plurality of stripe-shaped powder electrode layers and uncoated areas are formed in the width direction perpendicular to the object by the partitions.
The method for manufacturing a secondary battery according to claim 2, further comprising the steps of: sucking the powder scattered in the electrode uncoated area between the powder layer electrodes in the direction of movement of the object by vacuum along the width of the electrodes and discharging it to the outside; and further sucking the powder on the object other than the electrode pattern by vacuum perpendicular to the electrodes in the direction of movement of the object to form the electrode uncoated area, thereby forming the powder uncoated area and the powder electrode pattern layer.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that the electrode is formed by stacking powder on the object and pressing with a roll multiple times, and in at least the final press, the object and the powder layer are heated to a temperature equal to or higher than the softening point of the binder contained in the electrode powder, and pressed with a linear pressure of 10 kN/cm or more to form the electrode.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that in the roll press process for laminating the current collector, the negative electrode layer, the electrolyte layer, the positive electrode layer, and the current collector, which is a process subsequent to the electrode formation, the roll temperature or the powder temperature is heated to a temperature equal to or higher than the softening point of the binder or the electrolyte polymer contained in the electrode powder, and pressing is performed with a linear pressure of 10 kN/cm to 50 kN/cm.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that the electrode powder is a granulated powder selected from at least electrode active material particles, electrolyte particles or fibers, binders, electrolyte polymers, conductive assistants, and core-shell particles obtained by dry granulation of active material particles and electrolytes.
The method for manufacturing a secondary battery or an all-solid-state battery according to claim 2, characterized in that a dispersant is added to a conductive assistant consisting of carbon nanotubes or carbon nanofibers before the electrode powder is applied to the current collector of the object, and a binder solution or a slurry consisting of binder fine particles having an average particle size of 0.1 micrometers or less and a poor solvent is further selected and added to the current collector to adjust the solid content to 1.5% or less, and the liquid is applied to a wet thickness of 15 micrometers or less.
A method for applying powder to an object by sucking in powder at a powder supply position of a porous hollow roll rotating in the moving direction of the object, depositing and stacking the powder on the outer circumference of the roll, and detaching the powder at a coating position for the object by stabilizing the bulk density of the powder layer by creating a negative pressure inside the roll at the powder loading position to suck in the powder and deposit the powder on the surface of the roll to form a powder layer; providing an electrostatic charging means between the roll and the object to charge the powder; at least at the closest position of the object to the roll, using compressed gas to detach the powder from inside the roll, earthing the powder on the surface of the roll and depositing it on the moving object; and providing an enclosure with an exhaust port for excess gas between the roll and the object to prevent the effect of wind from the outside and the outflow of the powder outside the coating device.
The powder application method of claim 13, characterized in that the hollow roll into which the powder is filled has at least one porous recessed shape, the powder is filled into the recessed portion while being sucked from the hollow side of the roll, and in an application device located close to the object, the powder in the recessed portion is sprayed from the hollow side with positive pressure gas to apply it to the object.
A method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the powder is applied to an object by sucking the powder at a supply position of the electrode powder of a porous hollow roll rotating in the moving direction of the object, depositing and stacking the powder on the outer circumference of the roll, and releasing the powder at a coating position for the object, by applying the powder to the object by applying a negative pressure inside the roll at the powder loading position to suck the powder and deposit the powder on the surface of the roll to form a powder layer and stabilizing the bulk density of the powder layer, providing an electrostatic charging means between the roll and the object to charge the powder, at least at the closest position of the object to the roll, releasing the powder from inside the roll with compressed gas, and depositing the powder on the surface of the roll on the moving object while being grounded, and applying the powder to the object, and providing an enclosure means with an outlet for surplus gas between the roll and the object as a coating device to prevent the influence of wind from the outside and the outflow of the powder to the outside of the coating device.
A method for applying powder to an object by applying a powder on a porous belt that rotates in the direction of movement of the object, comprising the steps of: applying negative pressure to the opposite side of the belt at a powder supply position to suck in the powder and deposit the powder on at least the belt surface; charging the powder between the belt and the object with an electrostatic charging means; detaching and earthing the powder on the belt at a coating position for the object to deposit the powder on the moving object; and providing an enclosure with an exhaust port for excess gas between the belt and the object at the coating position to prevent the effect of wind from outside and the outflow of powder to the outside as a coating device, thereby applying powder to the object.
A method for manufacturing a secondary battery or an all-solid-state battery by applying an electrode powder on a porous belt that rotates in the moving direction of the object to the object to form an electrode, comprising the steps of: applying negative pressure to the opposite side of the belt at the powder supply position to suck in the powder and attach the powder to at least the belt surface; charging the powder between the belt and the object with an electrostatic charging means; detaching and earthing the powder on the belt at the application position to the object to attach the powder to the moving object; and providing an enclosure with an outlet for excess gas between the belt and the object at the application position as an application device to prevent the influence of wind from outside and the outflow of the powder to the outside, thereby applying the electrode powder to the object to form an electrode. A method for manufacturing a secondary battery or an all-solid-state battery, characterized in that the electrode powder is applied to the object to form an electrode by the steps of: applying negative pressure to the opposite side of the belt at the powder supply position to suck in the powder and attach the powder to at least the belt surface; charging the powder between the belt and the object with an electrostatic charging means;