APPLICATION OR FILM FORMATION METHOD FOR PARTICULATE MATTER

Abstract

[Problem] Upon application or film formation of a particulate matter to/on an object, the particulate matter moving with a speed is heated in a time duration from a suction port for particulate matter to the object, thereby softening or melting at least some of the particulate matter when the particulate matter is applied to the object.

[Solution] A particulate matter is heated by means of induction heating or laser in a time duration from a suction port for particulate matter to an object, so that at least some of the particulate matter is softened or melted at a relatively low temperature on the object in synergy with the collision energy of the particulate matter with the object, thereby enabling the application or film formation of the particulate matter.

Claims

1. An application or film formation method for a particulate matter by pumping a particulate matter or sucking the particulate matter from a suction port, transferring the particulate matter, ejecting the particulate matter from an ejection port toward an object, and softening at least some of the particulate matter to enable the application or film formation on the object, comprising: a step of providing a pumping means or a suction port for the particulate matter and an ejection port for the particulate matter, the ejection port communicating with the pumping means or the suction port, a step of transferring the particulate matter by differential pressure between the pumping means or the suction port and the ejection port to eject the particulate matter from the ejection port toward the object, a step of keeping ejection weight per second of the particulate matter within ±5% of a set value, a step of setting the object downstream of the ejection port, and a step of providing a heating means for the particulate matter between the pumping means or the suction port and the object, wherein: at least some of the particulate matter colliding with the object is at least softened or melted.

2. The method according to claim 1, wherein at least the ejection port for particulate matter and the object are arranged under vacuum, so that the differential pressure is generated between the ejection port and the suction port or the pumping means for particulate matter.

3. The method according to claim 1, wherein the particulate matter is transferred or ejected in a pulsed manner.

4. The method according to claim 1, wherein the particulate matter to be transferred is at least one selected from: those fluidized as a gas-powder mixture; those for which a slurry comprising the particulate matter and at least a solvent is formed, and finely dropletized or micronized by a fine particle generator; those applied on a substrate in advance; and those filled in a body provided with a recess or a through hole in advance.

5. The method according to claim 1, wherein a branching means provided with a branch port is installed upstream of the ejection port for particulate matter, and surplus gas is discharged from the branch port while the particulate matter is ejected from the ejection port toward the object.

6. The method according to claim 1, wherein the suction port or the pumping means for particulate matter is installed in a first vacuum chamber, at least the object and the ejection port are installed in a second vacuum chamber, and degree of vacuum in the second vacuum chamber is high.

7. The method according to claim 4, wherein the particulate matter on the substrate or the particulate matter filled in the body is mixed by adding at least a solvent to the particulate matter to form a slurry, then applied or filled and dried.

8. The method according to claim 1, wherein the heating means for particulate matter is at least one selected from laser, electron beam, microwave, induction heating, plasma, flame, far infrared ray and a heater.

9. The method according to claim 1, wherein the object is heated at least when the particulate matter is ejected.

10. The method according to claim 5, wherein the branch port and the ejection port are installed under vacuum, the particulate matter between the ejection port for particulate matter and the object is heated with the heating means for particulate matter, or only the surface of the particulate matter applied to the object is heated with the heating means, and at least the particulate matter being laminated is softened or melted.

11. The method according to claim 1, wherein the particulate matter contains short fibers, and is composed of a mixture of multiple kinds of particulate matter.

12. The method according to claim 1, wherein the particulate matter contains short fibers, and multiple kinds of particulate matter are prepared, each of which is provided with an independent pumping means or suction port and an independent ejection port for particulate matter, and each of the particulate matter is mixed downstream of the ejection port, or ejected to the object with a time difference, or ejected so as to laminate at different positions, and laminated.

13. The method according to claim 1, wherein the object is selected from a collector for a secondary battery, a positive electrode or negative electrode layer, a separator, and a polymer electrolyte layer.

14. The method according to claim 12, wherein the object is selected from a collector for an all-solid-state battery, a positive electrode or negative electrode layer, and an electrolyte layer, and the plurality of particulate matter also contain short fibers and are selected from active material particles for a positive electrode or a negative electrode, electrolyte particles, conductive assistants, and binders.

15. The method according to claim 1, wherein a layer composed of a binder or a mixture of a binder and the particulate matter is formed on the object in advance.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0054] FIG. 1 is a schematic cross-sectional view illustrating the present invention.

[0055] FIG. 2 is a schematic cross-sectional view according to an embodiment of the present invention.

[0056] FIG. 3 is a schematic cross-sectional view according to an embodiment of the present invention.

[0057] FIG. 4 is a schematic cross-sectional view according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0058] In the following, preferred embodiments of the present invention will be described with reference to the drawings. The following embodiments are given only for the illustrative purpose to facilitate the understanding of the invention, and not intended to exclude feasible additions, replacements, modifications made thereto by persons skilled in the art without departing from the technical scope of the present invention.

[0059] The drawings schematically show preferred embodiments of the present invention.

[0060] In FIG. 1, the substrate 7 is applied with the particulate matter 18 controlled at a constant weight per unit area. A guide for a constant weight is within ±5%, preferably within ±1.5% of the set value per square centimeter. For example, in the case of 0.6 mg per square centimeter, it is within ±0.03 mg or ±0.009 mg. The particulate matter can be easily sucked by bringing the suction port 12 close to or in contact with the surface of the particulate matter. The particulate matter is transferred from the suction port 12 to the ejection port 5 communicating with the suction port 12 by differential pressure and applied to the object 1 to form a coating layer or a film layer 2. The ejection port 5 may be a nozzle, and the shape may be round, square, slit groove, or the like, the shape and size are not limited, but it is preferable to select the ejection port 5 according to the shape of the object 1. As a means for making the weight per unit area on the substrate constant, the particle size distribution of the particulate matter can be uniformized and the weight per unit area can be made more stable and constant by coating multiple layers as many as possible, for example, in 100 layers. Alternatively, it is also possible to prepare a plurality of substrates applied with one layer or a plurality of layers and similarly prepare a plurality of suction ports and ejection ports to pursue the averaging per unit area. In addition, when it is ejected from the ejection port 5 to the object 1 and applied, the uniformity of the coating film weight per unit area of the particulate matter on the object 1 can be improved by coating not only one layer but also a plurality of layers, for example, 10 or more layers and reducing the weight per unit area as much as possible as in the example on the substrate 7. When it is coated to/on the substrate 7 or the object 1 in multiple layers, it is preferable to relatively move the application means and the substrate, further the suction port 12 and the substrate 7, or the ejection port 5 and the object 1. The differential pressure may be an ejector method, but the chamber 3 in which the object 1 is installed can be set to a negative pressure (vacuum), thereby the particulate matter can be sucked from the suction port 12 and applied to the object 1. The differential pressure is set to 50 kPa or more, and the ejection speed of the particulate matter is set to 150 m/sec or more to enable the collision and application on the object. Even if the ejection speed is not as high as 150 m/sec, and even if the fine powder is not preferably submicron or less, the particulate matter can be heated halfway with the heating means 3, and even if the particulate matter has a particle size of about 0.08 to 2 microns or more, at least some of the particulate matter can also be softened to enable the application or the film formation. Note that 50 kPa or more means a higher vacuum side. The differential pressure is not particularly limited. In addition, the atmosphere of the substrate 7 and the suction port 12 may also be set to a vacuum atmosphere if there is a differential pressure such as a differential pressure of 50 kPa or more, between them and the object 1.

[0061] In FIG. 2, the particulate matter flows as the gas-powder mixture 11 with the gas ejected from the porous tank 9 provided in the flow tank. The inactive gas such as argon is supplied from the gas line 10. The fluidized gas-powder mixture 11 is sucked from the suction port 12, moves to the vacuum chamber 3, and is ejected from the ejection port 5 to the object 1.

[0062] The heating means 4 is installed between the ejection port 5 and the object to support the softening and melting of the particulate matter due to collision on the object 1. As the heating means, the flow path 15 such as a metal pipe having good heat conduction can also be heated by far infrared ray, induction heating, hot air, steam, a heat element, or the like to heat the moving particulate matter. It is important to prevent the particulate matter from melting in the flow path 15 and from adhering to the inner surface of the flow path 15. In addition, it is important to keep the heating temperature as low as possible so as not to impair the performance so that the components of the active material for electrodes of the battery do not deteriorate at high temperatures. When installing the heating means between the ejection port 5 and the object, it may be laser or electron beam, and the type of the laser is not limited, but when heating only the surface of the particulate matter, a femtosecond laser or a picosecond laser or the like is preferable. In addition, at the stage when the particulate matter is laminated and applied on the object 1, it can be irradiated with a femtosecond laser or the like to form a film by at least partially softening or melting for each lamination so as not to affect the components of the active material. In addition, the heating means can be selected and installed both in the flow path and downstream of the ejection port.

[0063] In FIG. 3, the particulate matter is sent to the thermal spraying gun 25 in a pulsed manner to stabilize the moving amount and to easily adjust the injecting amount per unit time from a very small amount to a large flow rate. Therefore, the particles are melted by the flame from the fuel gas 30 while being injected in a pulsed manner Melted particles adhere to the object (not shown) to form a film. The pumping or suction of the particulate matter is not particularly limited. The supply means for the particulate matter may be an ejector method or a supply form as shown in FIG. 1. The through holes of the substrate and the openings of the screen can be filled with particulate matter, which can be sucked and transferred.

[0064] In FIG. 4, the particulate matter is made into a slurry with a solvent and discharged or sprayed from the applicator 35 toward the suction port 12 with fine droplets 36. The suction port 12 communicates with the ejection port 5, the injection port 5 and the object 1 are installed in the vacuum chamber 3, and the solvent of the slurry discharged or sprayed evaporates by the atmosphere of the vacuum chamber 3 or the heating means 40, diffuses in the vacuum chamber and is sucked by a vacuum pump. Only the particulate matter that does not contain a solvent, or the particulate matter that contains a small amount of solvent and has directionality, adheres to the object. Whether the solvent is contained or not can be adjusted by the heating means and the degree of vacuum. In addition, in this method, it is possible to select whether the particulate matter is softened or melted to form a film on the object or the particle is maintained as it is. When guiding slurry droplets of about 0.5 millimeters or less, spray fine particles with an average particle size of about 0.1 or less, or slurry fine particles generated by another fine particle generator to a vacuum chamber using a solvent for slurry having a low boiling point of about 100° C. or less, good results can be obtained even without using the heating means.

[0065] For example, the solvent used includes ketone-based acetone, MEK (methyl ethyl ketone), MPK (methyl propyl ketone), etc., alcohol-based ethanol, methanol, IPA (2-propanol), 1-propanol, etc., or hydrocarbon-based heptane (n-heptane), etc., and products that do not belong to PRTR method or Ordinance on Prevention of Organic Solvent Poisoning are preferable. Water can also be used.

[0066] In addition, by applying this method to a high boiling point solvent such as NMP (N-methyl-2-pyrrolidone), which is often used as a solvent for polymer binders in the field of secondary batteries, the solvent evaporation can be expected in a short time or instantaneously by azeotropic action with the low boiling point solvent. It is particularly suitable for NMP or the like having a boiling point of more than 200° C. as described above, regardless of whether it is heated or not. Especially when no heating means is used, the capacity of the vacuum pump for the vacuum chamber is required to be a capacity to maintain the vacuum degree of the vacuum chamber, for example, at 1 Torr, and to instantaneously discharge the compressed gas for spray flowing into the vacuum chamber and the outside air flowing in from the suction port. A capacity of at least 2 times or more, ideally 10 times or more for the suction amount is preferable. Commercial vacuum pumps such as FT4-65LE and FT4-150LE manufactured by ANLET, Co., Ltd can be used, which have a discharge speed of about 1 Torr and 0.2 M.sup.3/min or 1 m.sup.3/min even if the flow rate of the two-fluid spray gas is about 20 to 200 NL (normal liter) per minute.

[0067] This method is effective for the evaporation or solvent recovery of the high boiling point NMP and highly toxic DMF, which are solvents that dissolve binders such as vinylidene fluoride (PVDF) for the formation of electrodes in lithium ion secondary batteries or the like. A binder that does not adhere to the flow path and affect the application weight or the like may be added to the slurry.

[0068] In this method, the object can also be heated, and it can be laminated while colliding with impact by relatively moving the ejection port and the object, so that a uniform particulate matter layer with extremely few voids can be formed.

[0069] In addition, with the prior art, it has been impossible to microscopically and uniformly apply the particulate matter with a wide base of particle size distribution. It is extremely difficult to apply a thin film at one time with a variation of ±5% or less, preferably ±1.5% or less per unit area of at least per square centimeters or less, and even per square millimeters or less. Even with a sharp particle size distribution, when observed microscopically, parts of large particles and small particles naturally exist, and the shape cannot be said to be constant.

[0070] In the present invention, the weight per unit area of the particulate matter in the pre-step of application or film formation on the object is made constant. In order to make it constant, when applying the particulate matter in the pre-step to the substrate, the applicator, which is a part of the applying device for the particulate matter, and the substrate are relatively moved to perform application a plurality of times. Specifically, the first layer is applied while the substrate is moved pitch by pitch and the applicator is traversed. Next, the phases of the pitches are shifted, and the second layer, the third layer, and so on are overlaying applied. The applicator may be moved pitch by pitch and the substrate may be traversed, or they may be alternated to pursue a more uniform application weight. In addition, regardless of whether the coating material is a particulate matter or a mixture with a solvent, the application method and means are not limited, but pulsed spray is preferable because the application efficiency can be increased. Furthermore, if at least the application portion of the substrate is grounded and static electricity or the like is applied to the particulate matter or the slurry to charge and perform application, even fine powder can be adhered, so that the uniformity is further increased. It is effective to attach a solvent or the like that is easily charged to the particulate matter that is difficult to be charged.

[0071] By doing so, it is possible to make the weight per unit area and even per micro unit area uniform also from the viewpoint of probability.

[0072] In addition, the present invention is not limited to applying a mixture composed of a plurality of kinds of particulate matter and short fibers or a slurry thereof on a substrate in multiple layers by using a single applicator, it is also possible to laminate and apply a plurality of particulate matter and slurries in multiple layers by using a plurality of applicators.

[0073] In addition, according to the present invention, a plurality of particulate matter and slurries can be applied to a plurality of substrates by using a plurality of applicators, and if necessary, the gradient application that changes the desired mixing ratio of particulate matter in the thickness direction of the coating film is performed, and the particulate matter on each substrate can be applied to/on the object in a desired order in multiple layers. The suction port and the ejection port may be provided one for each, or may be provided for each type of particulate matter.

[0074] When the object is an object for a secondary battery, for example, a collector and the particulate matter are active material particles, conductive assistant particles or fibers, the plurality of particulate matter or fibers can be laminated on the collector. It may be laminated by different application means, or it may be mixed in advance and laminated. A binder such as PVDF or rubber, or an organic electrolyte resin for a polymer battery, or the like can be extremely thinly encapsulated or partially adhered to active material particles, conductive assistant particles, or fibers. At least the binder or the like can be softened by a heating means in the state of particulate matter or fiber to form a film together on the collector. Even if the heating means up to the object is not used, the object may be heated above the softening point of the binder to form a film. As the application means, an electrostatic coating method such as corona discharge, triboelectric charging, or combination thereof can be used. The binder or the like may be made into particles or fibers, mixed with the active material particles and applied, and can be independently laminated. In the case of independent laminating after film formation, the laminating order may be started from any of them, and in the laminating step, the ratio of the conductive assistant or the like can be changed in order from the collector so that the ratio changes in a gradient manner.

[0075] In addition, by keeping the weight per unit area as low as possible and freely combining them and laminating them as thinly as possible in multiple layers, uniform and ideal mixing of multiple kinds of materials can be achieved. In the present invention, the particulate matter or fiber can be directly applied to the substrate or the object. In addition, each of them can be made into a slurry and laminated independently. Further, they also can be mixed and laminated.

[0076] In addition, when applying a particulate matter or a slurry to/on a substrate or an object with an applicator, the substrate and the applicator are relatively moved, one of them is fed at a desired pitch, and the other is traversed to enable the application on the substrate or the object, the second and subsequent layers are offset and two or more layers (for example, 10 layers) are applied at a dense pitch (for example, a pitch of 1/10 of the desired pitch), so that the application distribution of the particulate matter is more uniformized. In addition, the substrate or the object may be a cylinder or a film or foil wound around the cylinder, and the cylinder can be rotated. In addition, the film may be a porous film such as a secondary battery separator, and the foil as a collector has an electrode formed on it and the electrolyte polymer is melted on the electrode, or is made into a solution or an emulsion with an organic solvent or the like, or is made into particulate matter or fibers, and further, the particulate matter or the like is made into a slurry and applied, thereby an electrolyte layer can be formed. The substrate or the object can be moved intermittently or continuously by a roll-to-roll method.

[0077] Similarly, in the present invention, the positive electrode of the all-solid-state battery can be formed on the collector and the negative electrode can be formed on another collector by the above method, and at least the solid electrolyte particles are softened on either or both of them, applied and crimped to form an all-solid-state battery cell, further, an all-solid-state battery can be manufactured. The binder may or may not be used.

[0078] According to the present invention, it can be applied not only to lithium-ion secondary batteries or next-generation secondary batteries such as all-solid-state batteries or all-solid-state air batteries, but also to fuel cells, especially SOFCs, or supercapacitors and other storage batteries. It can be applied to the thermal spraying fields, semiconductors, electronic parts, biotechnology, and pharmaceutical fields that require powder coating, micro-distribution and application of particulate matter, and if applied to the aerosol deposition process, the adhesion amount can be expected to approach 100% as much as possible with respect to the conventional adhesion amount of about 10%, and it can be performed with high quality and low cost.

DESCRIPTION OF THE REFERENCE NUMERAL

[0079] 1 substrate [0080] 2 coating film [0081] 3 vacuum chamber [0082] 4 heating means [0083] 5 ejection port [0084] 6 branch port [0085] 7 substrate [0086] 9 fluidization hopper [0087] 10 gas supply line [0088] 11 gas-powder mixture [0089] 12 suction port [0090] 18 particulate matter [0091] 20 ejector [0092] 25 thermal spraying gun [0093] 26 thermal spraying injection pattern [0094] 35 applicator [0095] 36 droplets or spray particles [0096] 40 flow path heating means