JP4914673B2 - Method for coating battery or capacitor electrode strip - Google Patents

Description

The present invention relates to a method for coating a metal foil or plastic-made battery or capacitor electrode strip, and more particularly to a method for applying a coating solution to a battery or capacitor electrode strip.

  In recent years, as environmental issues have been raised, clean energy storage systems using solar power generation or wind power generation, distributed power sources for the purpose of load leveling of electric power, or electric vehicles or hybrid electric vehicles replacing gasoline vehicles Development of power supplies (main power supply and auxiliary power supply) has been actively conducted.

  In addition, the conventional lead batteries have been used as the power source for the electrical equipment of automobiles, but recently, the installation of power windows and IT-related equipment has been enhanced, and energy density, New power sources with high power density are being demanded.

  Further, there is a need for a drum machine for copiers that require a large current instantaneously, a vending machine, a heated toilet seat or hot water wash for a toilet, and a power supply for starting an idling stop of an automobile.

  Lithium ion secondary batteries or electric double layer capacitors have attracted attention as power storage devices including such drive power supplies.

  However, although a lithium ion battery has a high energy density, there are problems in output characteristics, safety, and cycle life. On the other hand, an electric double layer capacitor is an electronic component that is widely used as a power source for memory backup of IC or LSI. Although the discharge capacity per charge is smaller than that of a battery, it has excellent instantaneous charge / discharge characteristics, It has high output characteristics and maintenance-free characteristics that can withstand charging and discharging over tens of thousands of cycles. Such characteristics do not exist in lithium batteries or nickel metal hydride batteries.

  In this way, the electric double layer capacitor has advantages, but in general, the energy density is about 3 to 6 Wh / 1, which is about two orders of magnitude smaller than that of the lithium ion battery. However, as a drive power source that is required, the actual situation has not yet reached the practical level. When considering the use of electric vehicles, it is said that an energy density of 8 to 15 Wh / 1 is required for practical use, and 20 Wh / 1 is required for the diffusion level.

  In recent years, a power storage device called a hybrid capacitor has attracted attention as a power storage device corresponding to such applications requiring high energy density and high output characteristics. There are two types of electrodes: nonpolarizable electrodes that involve charge transfer at the electrode-electrolyte interface (Faraday reaction) and polarizable electrodes that do not involve charge transfer (non-Faraday reaction). Generally, a battery has a configuration using non-polarizable electrodes on both poles, but what is called a hybrid capacitor has a configuration using a polarizable electrode on one pole and a non-polarizable electrode on the other pole. Have. The development of a power storage device that combines the high energy density of a battery and the high output characteristics of an electric double layer capacitor has become active.

For high-energy type capacitors, capacitors using lithium ions occluded by chemical or electrochemical methods in advance for materials that can occlude and desorb lithium ions are used here as references. As disclosed in JP-A-3-233860 and JP-A-5-325965.
JP-A-3-233860 JP-A-5-325965

  In addition, when a large cell such as an automobile power source is targeted, as a method of supporting lithium on the negative electrode in advance, the positive electrode current collector and the negative electrode current collector are provided with holes penetrating the front and back, respectively, and the negative electrode active material is lithium. An organic electrolyte battery that can be reversibly supported and in which lithium derived from a negative electrode is supported by electrochemical contact with lithium disposed to face the negative electrode or the positive electrode has been proposed (for example, WO98133227). Here, by providing holes that penetrate the front and back surfaces of the electrode current collector, lithium ions can move between the front and back surfaces of the electrode current collector without being blocked by the electrode current collector. In the apparatus, lithium can be electrochemically supported not only on the negative electrode disposed in the vicinity of lithium but also on the negative electrode disposed away from lithium through the through hole. Further, since lithium ions can freely move between the electrodes through the through holes, charging and discharging proceed smoothly.

  What is important in these techniques is to form an electrode layer on a current collector having holes penetrating the front and back surfaces such as expanded metal and porous etching foil.

  Conventional electrode coating uses a die coater, a slide coater or a roll coater, a comma coater, a gravure coater, etc., for example, a strip-like body having no holes penetrating the front and back surfaces, such as aluminum foil, or a strip-like shape having holes. The body is first coated on one side and then subjected to a drying process, followed by a method of coating the other side in the same manner.

  In addition, a double-sided coating method has been proposed. For example, a pair of dies are arranged on both sides of a conveyance path of a base material that runs in a vertical direction, and a pair of blades are provided above the pair of dies. The coating thickness is controlled by scraping off the coating solution discharged from the blade with a blade, or the double-sided coating method in which the coating thickness is controlled by the pressure of the coating solution ejected from a die (for example, Kosho 55-46223, JP-A-3-72976).

  Furthermore, there are examples (JP-A-8-206567, JP-A-10-34050, and JP-A-10-216603) in which the double-sided coating accuracy is improved. In either method, two dies are opposed to each other on both sides of the substrate. Thus, double-sided coating is performed.

  When a coating solution is to be continuously applied to a metal foil or a plastic strip, the wettability is particularly poor when the coating solution is an aqueous coating solution, and it is difficult to increase the coating speed.

  Further, since both edge portions of the belt-like body are thickly coated due to contraction of the coating liquid, there is a problem that the uniformity of the thickness cannot be maintained. This is remarkable when an aqueous coating solution is applied on a porous metal foil or plastic film.

  These problems occur because there are oily components or oxide films that cannot be defatted on the metal foil, and the wettability is poor, so that the surface tension of the aqueous coating liquid increases. This problem becomes more conspicuous when a large number of holes penetrating the front and back surfaces are opened in the metal foil. In the case of the porous foil, the interfacial tension between the coating liquid and the foil does not occur in the hole portion, and thus it becomes more difficult to wet. The wettability between the porous substrate and the liquid is expressed by the following Cassie equation well known to those skilled in the art.

cosθ1 = Φ2cosθ2 + Φ3cosθ3
Here, θ1 represents the contact angle of the two-component support, θ2 and θ3 represent the contact angles of the respective components, and Φ2 and Φ3 represent the proportion of the surface of each component. In the case of a strip with many holes, components 2 and 3 correspond to the strip and the pores (air), respectively. In the case of air, the contact angle with water is 180 °. That is, −1 * surface ratio. In this case, the component 1 is subtracted by the cos of component 2 (air), and the value on the right side of the equation becomes small. Therefore, θ1 is increased (becomes difficult to wet).

  This effect is also significant when the strip of plastic material is not a metal foil but has a fluorine-based material, a material having a surface tension of about 40 dyn / cm or less, or a hole penetrating the front and back.

  Therefore, an object of the present invention is to increase the coating speed and improve the throughput by improving the wettability of the battery or capacitor electrode strip.

  Another object of the present invention is to improve the uniformity of the coating film on the front and back surfaces of the belt-like body.

In order to solve the above problems, in one embodiment of the present invention, a method of applying a coating solution to the front and back surfaces of a metal foil or plastic battery or capacitor electrode strip is performed while the strip is continuously running. A step of applying a liquid that is compatible with the liquid and having at least a lower viscosity than the coating liquid or a surface tension lower than the coating liquid to the front and back surfaces, and before the liquid is completely dried, It comprises a step of applying, and a step of drying while continuously running the strip, and the coating liquid is applied to the front and back surfaces of the strip at a high speed and uniformly.

  Specifically, the liquid is water, a liquid obtained by adding 0.01 wt% to 10 wt% of a surfactant to water, an organic solvent compatible with water, and water compatible. It is selected from the group consisting of liquids to which 5 wt% to 80 wt% of organic solvent is added. Alcohol is a typical organic solvent.

  Preferably, in the method according to the present invention, when the liquid is water or a liquid obtained by adding 0.01 wt% to 10 wt% of a surfactant to water, a copolymer poly (styrene-butadiene) is used. A step of adding a water-based resin selected from the group consisting of rubber-based binder resins, carboxymethyl cellulose-based resins, acrylic resins, polyamide resins, and polyethylene resins.

  In addition, the method according to the present invention further includes a method in which when the liquid is an organic solvent compatible with water or a liquid added with 5 wt% to 80 wt% of an organic solvent compatible with water, A step of adding a non-aqueous resin selected from the group consisting of a fluorine-containing resin composed of ethylene tetrafluoride and polyvinylidene fluoride, a polyimide resin, and a polyamide / imide copolymer resin can be included.

  Preferably, the liquid to be pre-coated has a viscosity of 100 cp or less and a surface tension of 60 dyn / cm or less.

Specifically, the strip has a number of holes through the table back.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present invention is not limited to these examples.

  The method of applying the coating liquid to the front and back surfaces of the metal foil or plastic strip according to the present invention is compatible with the coating liquid while continuously running the strip, and at least has a lower viscosity than the coating liquid or the surface of the coating liquid. A step of previously applying a liquid having a low tension on the front and back surfaces of the belt-like body;

  The application width of the liquid to be pre-applied can be appropriately set according to the expected effect. For example, it may be pre-applied almost over the entire width of the strip to which the desired coating liquid is applied, or slightly wider than the applied width. Or you may pre-apply only to a part of width | variety applied, for example, an ear | edge part (edge part). When pre-applying to the ears (ends), the pre-applied liquid is preferably applied in a width and position that protrudes slightly inside and slightly outside the outermost end where the desired coating liquid is applied. .

  The liquid to be pre-applied is preferably applied continuously on the surface of the belt-like body in the width direction and the length direction, but can also be applied intermittently. For example, the surface of the band-shaped body can be applied in the form of dots, or when the band-shaped body has holes, the liquid can be pre-applied to such an extent that the holes are filled. In this case, it is not necessary to fill all the holes with liquid, and it is sufficient that the holes are filled with 5% or more, preferably 30% or more, more preferably 50% or more of the whole holes. As can be seen from the Cassie equation described above, the wettability is improved as the hole area ratio is reduced. In addition, when the two components are a strip and a pre-coating liquid, there is an affinity between the pre-coating liquid and the desired coating liquid for the proportion of the surface of the pre-coating liquid, even if it is not continuously pre-coated. If present, the contact angle is expected to be low (plus).

  The liquid to be pre-coated is preferably a liquid having compatibility (affinity) with a desired coating liquid, a lower viscosity than the desired coating liquid, and a lower surface tension than the desired coating liquid.

  For example, when the desired coating liquid is aqueous, a liquid having a lower viscosity and lower surface tension than the coating liquid is preferable. Specifically, water, a liquid to which a surfactant is added in an amount of 0.01 wt% to 10 wt%, preferably 0.1 wt% to 3 wt%, and an organic solvent compatible with water (for example, alcohol). Or a liquid to which 5 wt% to 80 wt% of an organic solvent (typically alcohol) compatible with water is added is preferable.

  The alcohol used as a representative organic solvent can be selected from monohydric alcohols such as methanol, ethanol and propanol, dihydric alcohols such as ethylene glycol, and polyhydric alcohols such as trivalent glycerin. Among these, lower alcohols having 3 or less carbon atoms are particularly preferable because of their good compatibility with water.

  As the surfactant, any of anionic, cationic, amphoteric, and nonionic can be used. Examples of the anionic surfactant include alkylbenzene sulfonic acid sodium salt, polyoxyethylene alkyl ether sulfate sodium salt, alkyl sulfate sodium salt, and polycarboxylic acid type polymer surfactant. Examples of the cationic surfactant include alkyltrimethylammonium chloride and alkyldimethylbenzylammonium chloride. Examples of nonionic surfactants include polyoxyethylene alkyl ether and polyoxyethylene alkyl allyl ether. These are merely examples, and other surfactants can be used in the present invention.

  When the pre-coating liquid uses water as a dispersant, examples of additives include rubber-based binder resins such as poly (styrene-butadiene) (hereinafter referred to as “SBR”), carboxymethyl cellulose-based resins, and acrylics. A small amount of water-based resin such as resin, polyamide resin, or polyethylene resin can be added and used.

  In addition, when the pre-coating liquid uses an organic solvent such as alcohol or N-methylpyrrolidone as a dispersant or solvent, examples of additives include fluorine-containing resins such as polytetrafluoroethylene and polyvinylidene fluoride, and polyimide. A small amount of non-aqueous resin such as resin or polyamide / imide copolymer resin can be used.

  The additive is not limited to the above-described aqueous resin or non-aqueous resin, and may be any one that can be used as a single or mixed organic solvent liquid compatible with the coating liquid.

  As physical properties of the pre-coating liquid, the viscosity is 100 cp or less, preferably 50 cp or less, more preferably 10 cp or less, and the surface tension is 60 dyn / cm or less, preferably 50 dyn / cm or less, more preferably 15 to 40 dyn / cm. .

The coating amount may be any 1~2cc / m ² or more, in view of the drying time, 10 cc / m ² or less. About the dispersion | variation in application amount, about 30 to 50% is an allowable range both in the length direction and the width direction.

  As a material of the metal foil used in the method according to the present invention, various materials generally proposed for applications such as a battery or a capacitor can be used. For example, aluminum, stainless steel, or the like can be used as the positive electrode substrate, and stainless steel, copper, nickel, or the like can be used as the negative electrode substrate. Examples of the shape include a plain foil obtained by rolling a metal or heat-treated thereon, and an etching foil obtained by chemically or electrically etching the surface thereof. In addition, there are porous substrates provided with front and back through holes, for example, expanded metal, punching metal, metal net, foam, or perforated etching foil. Here, the expanded metal refers to a porous base material produced by making a cut in a rolled metal foil with a cutter and then stretching and rolling it.

  A current collector having a through hole can be produced by etching as follows. First, a conductive layer made of a conductive material having a large number of holes is formed on one surface of a non-porous metal foil such as aluminum or copper by, for example, gravure printing, and then the other surface of the non-porous metal foil is formed. A non-porous or perforated conductive layer is formed by a gravure printing method, the whole is formed into a three-layer structure, and finally an etching process is performed using an etching solution that can dissolve only the metal foil. Here, what mixed polyimide resin, polyamide resin, these mixtures, etc. with the electroconductive material can be used as a coating liquid. Such a coating liquid is preferable because it is easy to appropriately design the shape and distribution of the holes.

  The thickness of the metal foil used in the method according to the present invention is 5 to 100 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm, and still more preferably 10 to 30 μm. When using a metal foil as an electrode, if the electrode current collector is too thick, the thickness of the entire electrode increases and the amount of active material in the entire electrode decreases, resulting in the energy density per weight or volume of the power storage device or Since power density falls, it is not preferable. Moreover, it has the fault that workability | operativity at the time of electrode coating falls. On the other hand, if the electrode current collector is too thin, the electrode strength decreases, so that wrinkles occur during electrode coating and uniform application cannot be achieved, or the current collector is cut, resulting in the reliability of the electrode. Has the disadvantage that the properties are significantly reduced.

  The thickness of the positive and negative electrode current collectors may be the same, but if the materials of the two are different, the weight per cell volume can be reduced if the larger specific gravity is made thinner. preferable. The thickness of the electrode current collector can be appropriately set in consideration of the characteristics of the power storage device or the workability of the manufacturing process.

  The through hole of the electrode current collector is provided to move the front and back surfaces of the electrode without the lithium ions in the electrolyte being blocked by the electrode current collector. Therefore, its shape and number must be selected so as not to disturb its function. Moreover, it is necessary to select so that the coating liquid applied to the porous metal foil is retained. The aperture ratio of the electrode current collector is defined as a ratio obtained by converting the ratio of {1- (current collector weight / current collector true specific gravity) / (current collector apparent volume)} to a percentage. Is done. The aperture ratio of the electrode current collector used in the present invention is 1 to 79%, preferably 20 to 60%, and more preferably 30 to 50%.

  For example, in a lithium ion capacitor, when the aperture ratio of the electrode current collector is high, lithium ions easily move between the front and back surfaces of the electrode through the through hole, and the time required to support lithium on the negative electrode is shortened. The unevenness of the support is less likely to occur. However, since the strength of the current collector decreases, wrinkles and cuts are likely to occur. In addition, since it becomes difficult to hold the coating liquid in the through hole, there arises a problem that the yield is lowered due to dropping of the coating liquid, cutting of the electrode, or the like. On the other hand, when the aperture ratio of the electrode current collector is low, the movement speed of lithium moving between the front and back surfaces of the electrode through the through-hole decreases, and the time required to support lithium on the negative electrode becomes longer, resulting in lower throughput. In addition, the problem of increased variation in cell characteristics arises. However, on the other hand, the strength of the current collector is increased and the active material is unlikely to fall off. Therefore, in consideration of such circumstances, it is desirable that the aperture ratio and the hole diameter of the electrode current collector are appropriately selected within the above range according to the structure of the power storage device.

  On the other hand, in the coating method according to the present invention, for example, polyimide, nylon, polyester, polypropylene, or the like can be used as the plastic strip. The strip can have a porous structure. The thickness of these plastic strips is 5 to 100 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm, and still more preferably 10 to 30 μm. The opening ratio is 10 to 79%, preferably 20 to 60%, more preferably 30 to 50%.

  The porous substrate has a strip shape, and the width is not limited thereto, but is about 100 mm to 1000 mm, preferably about 200 mm to 500 mm.

The method of applying the coating liquid to the front and back surfaces of the metal foil or plastic strip for battery or capacitor electrode according to the present invention applies the coating liquid to the front and back surfaces of the strip before the pre-coating liquid is dried. The process of carrying out is included. The coating liquid consists of fine powder and a binder resin. The fine powder is not limited thereto, but in the case of a battery or a capacitor electrode, the fine powder includes an active material such as a carbon material or an oxide having a shape that is easy to mold, such as powder, granule, and short fiber. As the positive electrode active material, for example, various activated carbons or conductive polymers or polyacene-based materials activated using steam, carbon dioxide, potassium hydroxide, or the like, starting from plants such as coke, pitch, resin, coconut shell, sawdust, etc. Further, carbon materials such as mesopore carbon in which mesopores having a pore diameter of 2.0 nm to 50 nm are remarkably developed, or metal oxides such as LiCoO ₂ , LiNiO ₂ , and MnO ₂ can be used. As the negative electrode active material, for example, various carbon raw materials starting from graphite such as natural graphite and artificial graphite, coke, pitch, thermosetting resin, coconut shell and tree, carbon fiber, polyacene, tin oxide Silicon oxide or the like can be used.

  The coating liquid is produced by mixing the fine powder with a binder resin. The binder resin for the battery or capacitor electrode may be insoluble in the electrolyte used, and an aqueous resin using water as a dispersant or solvent, or an organic solvent such as alcohol or N-methylpyrrolidone is dispersed. It is a non-aqueous resin used as a medium or a solvent. For example, rubber-based binder resins such as SBR and carboxymethyl cellulose resins can be used as aqueous resins, and phenol resins and melamine resins can be used as aqueous resins or non-aqueous resins depending on the composition. Acrylic resins, polyamide resins, polyethylene resins, and the like can be used as water-based resins by emulsifying them. Fluorine-containing resins such as polytetrafluoroethylene and polyvinylidene fluoride, polyimide resins, and polyamide / imide copolymer resins can be used as typical non-aqueous resins. Of these, SBR resins, acrylic resins, and organic solvent fluorine resins are preferable. The mixing ratio of the binder resin is 1 wt% to 20 wt%, preferably 2 wt% to 10 wt%, more preferably 2 wt% to 5 wt%, with respect to the fine powder.

  In addition to the fine powder and binder resin, a conductive agent for improving the conductivity of the coating liquid, a dispersant for improving the dispersibility, and the like can be appropriately added to the coating liquid as additives.

  The solid content concentration of the active material or the like of the coating liquid is not limited to this, but is 10 wt% to 70 wt%, preferably 12 wt% to 60 wt%. It is preferable to use a uniform liquid coating solution without aggregates. Although the viscosity of a coating liquid is not limited to this, It is 10-5000 [mPa * s] at 20 degreeC, Preferably it is 50-2000 [mPa * s].

Next, the coating method according to the present invention will be described with reference to the drawings. FIG. 1 schematically shows one example of a coating apparatus capable of executing a coating method according to the present invention. The apparatus includes a coating head 1, a coating liquid tank 5, a pre-coating liquid tank 3, a drying zone (8, 9), a feeding roller section 4 for continuously running the strip 6 and a winding roller section. 10 and. The coating head 1 is composed of two extrusion dies (2, 2 ′) having a slot interval 11 of 250 μm ± 10 μm. The two extrusion dies (2, 2 ′) are arranged so as to face each other, and are configured such that the belt-like body 6 travels on the center line thereof. In this way, the coating liquid can be applied to both surfaces of the belt-like body 6. The belt-like body 6 delivered from the delivery roller unit 4 is first immersed in the pre-application liquid tank 3 in which the above-described pre-application liquid is accommodated. As a pre-coating method, a roll coating method, a gravure coating method, coating by an extrusion die, a slide coating method, a spray coating method, and coating by a brush can be used. The pre-coated strip 6 is squeezed by a squeezing roll 7. The ironing roll 7 is preferably composed of two rolls having cushioning properties such as rubber and sponge. By sandwiching the belt 6 from both sides, the pre-coated liquid is made uniform and the belt 6 is moistened. It has the function to do. Before the pre-applied liquid is completely dried, the coating liquid supplied from the coating liquid tank 5 is applied to the coating head 1 at the same time on both the front and back surfaces of the strip 6. As a coating method for the coating liquid, besides the die coating method, a coating method in which the extruded liquid does not circulate, such as a curtain coating method and a slide coating method, can be used. The coating method of the coating liquid may be any one in which the pre-coated liquid and the coating liquid do not cause mixing and stirring in the coating process. Besides the double-sided simultaneous application method, a method of applying one side at a time or a method of applying only one side can also be used. In that case, the pre-coating method may be changed accordingly. The thickness of the applied layer is 30 μm to 300 μm, preferably 40 μm to 200 μm, and more preferably 50 μm to 100 μm. The strip 6 after the coating process is completed is sent to the drying zone (8, 9) and completely dried. Finally, the belt-like body 6 for which the coating process has been completed is taken up by the take-up roller unit 10.

  Hereinafter, an experiment in which a coating solution is applied to a belt-like body according to the coating method according to the present invention will be described. As the coating apparatus, the apparatus shown in FIG. 1 was used unless otherwise specified. The experimental conditions are as follows.

(1) Comparative Example 1:
Strip: Aluminum expanded metal having a thickness of 40 μm, a wire diameter of 0.2 mm, an aperture ratio of 40%, and a width of 500 mm Pre-coating: None Coating solution: The composition of the coating solution used is as follows.
Carbon powder 95 parts Carboxymethylcellulose 5 parts Water Suitable amount Solid content concentration 30wt%
Viscosity 500mPa · s
The coating solution was applied at a wet coating amount of about 133 cc / m ² so that the film thickness after drying was 80 μm.

(2) Example 1
Strip: The same aluminum expanded metal as in Comparative Example 1 Pre-coating: Water was stored in the tank, and the entire strip was immersed. Coating solution: The same as in Comparative Example 1 was used.

(3) Example 2
Strip: The same aluminum expanded metal as in Comparative Example 1 Pre-coating: A solution prepared by mixing water and alcohol in a ratio of 9: 1 was stored in a tank, and the entire strip was immersed. Coating solution: The same as in Comparative Example 1 was used.

(4) Example 3
Strip: Aluminum expanded metal same as Comparative Example 1 Pre-coating: A solution of water and alcohol mixed 1: 1 is stored in a tank and the entire strip is immersed. Coating solution: The same as Comparative Example 1 is used.

(5) Example 4
Band: The same aluminum expanded metal as in Comparative Example 1 Pre-coating: A solution in which water and a surfactant were mixed was stored in a tank, and the entire band was immersed. The surface tension at this time was 32 dyn / cm. Coating solution: Use the same as in Comparative Example 1

(6) Example 5
Band-shaped body: Copper expanded metal having a thickness of 30 μm, a wire diameter of 0.25 mm, an aperture ratio of 45%, and a width of 500 mm. Pre-coating: A mixture of water and alcohol in a ratio of 9: 1 was pre-coated only on the ears of the band-shaped body. The pre-coating was performed by continuously dropping the pre-coating liquid onto a sponge-like roll having a diameter of 50 mm and a width of 20 mm to form a wet shape, and applying only the ears 20 mm of the belt-like body with the roll. The composition of the coating liquid is as follows.
Carbon powder 88 parts Carbon black 4 parts Carboxymethylcellulose 5 parts
SBR type binder 8 parts water appropriate amount solid content concentration 25wt%
Viscosity 1600mPa · s

(7) Example 6
Strip: The same aluminum expanded metal as in Comparative Example 1 Pre-application: A solution prepared by mixing water and alcohol in a ratio of 1: 1 was applied by a spray method in which the air pressure was 2 kg / cm ² to form a mist. As a spray device, a Killy tank (model number Yb1 / 8MFJT SUEA001B TEF) manufactured by Spraying Systems Japan Co., Ltd. is used. Coating liquid: The composition of the coating liquid used is as follows.
Carbon powder 93 parts Carboxymethylcellulose 5 parts
SBR type binder 8 parts water appropriate amount solid content concentration 25wt%
Viscosity 1600mPa · s

  Under the above experimental conditions, the limit coating speed and the coating thickness uniformity were compared. Table 1 shows the experimental results.

From Table 1, it can be seen that the pre-application on the belt-like body allows the application rate of the coating liquid to be higher and uniformly applied. Furthermore, it can be seen that the effect is further improved by using water + alcohol or water + surfactant as the pre-coating solution.

  Furthermore, as a result of the experiment, when the pre-coating was not performed, the strip was cut at a rate of about once every 5 minutes. However, when pre-coating was performed, the cutting was performed for 10 minutes or more at a traveling speed of 3 m / min. It turns out that it does not occur. This is presumably because the foreign matter adhering to the belt-like body was washed away by pre-coating and foreign matter was prevented from being caught between the nozzles. Therefore, it can be seen that the method according to the present invention is also effective in improving the reliability.

  Although the invention has been described with reference to specific embodiments, it is not limited thereto. For example, it is possible to appropriately select and use a pre-application liquid and application method other than those described above.

FIG. 1 schematically shows an example of a coating apparatus used in the coating method according to the present invention.

Claims (6)

A method of applying a coating solution to the front and back surfaces of a metal foil or plastic battery or capacitor electrode strip,
A step of applying a liquid that is compatible with the coating liquid and has a lower viscosity than the coating liquid or a surface tension lower than that of the coating liquid to the front and back surfaces while continuously running the belt-like body;
Before the liquid is completely dried, applying the coating liquid to the front and back surfaces of the strip,
A step of drying while continuously running the strip,
A method consisting of: The method according to claim 1, wherein the liquid is water, a liquid obtained by adding 0.01 wt% to 10 wt% of a surfactant to water, an organic solvent compatible with water, and water. Wherein the method is selected from the group consisting of liquids to which is added 5 wt% to 80 wt% of an organic solvent compatible with. 3. The method according to claim 2, wherein the liquid is water or a liquid obtained by adding 0.01 wt% to 10 wt% of a surfactant to water. A method comprising adding a water-based resin selected from the group consisting of rubber-based binder resins such as butadiene), carboxymethylcellulose-based resins, acrylic resins, polyamide resins and polyethylene resins. The method according to claim 2, wherein the liquid is an organic solvent compatible with water or a liquid obtained by adding 5 wt% to 80 wt% of an organic solvent compatible with water. A method comprising the step of adding a non-aqueous resin selected from the group consisting of a polytetrafluoroethylene, a fluorine-containing resin comprising polyvinylidene fluoride, a polyimide resin, and a polyamide-imide copolymer resin. The method according to any one of claims 1 to 4, wherein the liquid has a viscosity of 100 cp or less and a surface tension of 60 dyn / cm or less. The method according to any one of claims 1 to 5, wherein the strip has a number of holes through the front back, at the method.