JP2019003725A - Manufacturing method of electrode - Google Patents

Abstract

To provide a manufacturing method of electrode capable of inhibiting adhesion of foreign matters in groove formation proces.SOLUTION: A manufacturing method of an electrode 1 has a coating step S1 of forming a coating film 30 by coating a metal foil 2 with slurry containing an active material and a binder, a groove formation step S2 of forming a groove sinking more than the surroundings in a part of the coating film 30 by blowing fluid thereto, and a dry step S3 of forming an active material layer 3 by drying the coating film 30 including a groove. In the groove formation step S2, the groove may be formed by blowing fluid to the coating film 30 while moving the metal foil 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode manufacturing method.

  Secondary batteries such as nickel metal hydride storage batteries and lithium ion secondary batteries are used in batteries of vehicles such as forklifts, hybrid cars, and electric cars. This type of secondary battery has an electrode winding body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, or an electrode assembly in which a plurality of positive electrodes and negative electrodes are stacked via a separator. In addition, as the positive electrode and the negative electrode, a foil electrode in which an active material layer is formed on a metal foil is used.

  The active material layer in the foil electrode is disposed in close contact with the separator in order to reduce the volume of the secondary battery and improve the energy density and power density. Therefore, there has been a problem that it takes a relatively long time to infiltrate the electrolytic solution from the gap between the electrode and the separator and supply the electrolytic solution to the entire active material layer. In addition, there is a problem that it takes a long time to discharge the gas generated inside the electrode assembly or the like due to the electrode reaction to the outside through the gap between the electrode and the separator.

  In view of this, a technique has been proposed in which a groove is provided on the surface of the active material layer to promote the supply of an electrolytic solution and the discharge of gas. For example, Patent Document 1 describes an electrode in which grooves are formed on the surface of an active material layer by machining, pressing, or laser processing.

JP 2004-207253 A

  However, when a groove is formed by machining or pressing, a processing tool such as a press die comes into contact with the active material layer, so that foreign matters derived from these processing tools may adhere to the active material layer. . Moreover, when forming a groove | channel by laser processing, there exists a possibility that foreign materials, such as dross generated by laser irradiation, may scatter and adhere to an active material layer. These foreign substances may cause a decrease in battery capacity or early deterioration of battery characteristics in the secondary battery.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an electrode manufacturing method capable of suppressing adhesion of foreign matters in the groove forming step.

One aspect of the present invention is an application process in which a slurry containing an active material and a binder is applied onto a metal foil to form a coating film,
A groove forming step of forming a groove depressed from the surrounding in a part of the coating film by spraying fluid on the coating film;
Drying step of drying the coating film provided with the groove to form an active material layer;
It is in the manufacturing method of an electrode which has.

  In the electrode manufacturing method, after forming a coating film containing an active material and a binder on a metal foil, a groove is formed by spraying a fluid onto the coating film before drying. Therefore, in the groove forming step, the groove can be formed without bringing a processing tool such as a press die into contact with the coating film. Therefore, it is possible to avoid adhesion of foreign matters derived from the processing tool.

  Moreover, the said manufacturing method can suppress scattering of the coating film by a fluid being sprayed by adjusting the pressure of a fluid, the direction to spray, etc. Even if a part of the coating film scatters in the groove forming step and a slurry splash is generated, the slurry splash adheres to the undried coating film, and thus the spray is applied to the coating film on the metal foil. Can be integrated. Therefore, according to the manufacturing method, it is possible to avoid the generation of foreign matters such as dross in laser processing.

  As described above, according to the above manufacturing method, generation of foreign matters in the groove forming step can be avoided. Therefore, it is possible to suppress adhesion of foreign matters in the groove forming step.

FIG. 3 is an explanatory diagram showing a method for manufacturing an electrode in Example 1. It is a perspective view of the groove | channel formation process in Example 1. FIG. 2 is a plan view of an electrode obtained by the manufacturing method of Example 1. FIG. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. It is explanatory drawing which shows the manufacturing method of the electrode provided with the active material layer on both surfaces of metal foil in Example 2. FIG.

  The metal foil used in the above manufacturing method may be preliminarily cut into the size of the electrode, or may be wound into a roll. When using the metal foil wound by roll shape, conveyance of the metal foil between processes can be performed more rapidly and the productivity of an electrode can be improved more.

  In the coating step, the slurry is applied on the metal foil to form a coating film. The slurry used in the coating process contains an active material and a binder. The slurry may further contain a solvent for dispersing a known conductive additive or active material for a secondary battery, a thickener that adjusts the viscosity of the slurry, and the like. When a thickener is contained in the slurry, the shape of the groove can be maintained for a longer time after the groove is formed in the groove forming step. Therefore, a narrow groove or a deep groove can be formed more easily.

  In the groove forming step, the fluid is sprayed on the undried coating film to form the groove. As the fluid, for example, a liquid that can be used in a slurry such as water and N-methylpyrrolidone, or a gas such as air, nitrogen, or argon can be used. A gas is preferably used as the fluid. In this case, the sprayed gas can be prevented from remaining in the coating film, and the groove can be formed without changing the composition of the coating film. Moreover, in the drying process performed later, a coating film can be dried in a short time compared with the case where a liquid is used as a fluid.

  The number of grooves formed in the coating film may be one, or two or more. Moreover, the width | variety of a groove | channel can be suitably set from the range of 0.1-2 mm, for example. By reducing the width of the groove, the volume of the active material layer formed on the metal foil can be increased, and thus the capacity of the electrode can be increased. From this viewpoint, the width of the groove is preferably 1.5 mm or less, and more preferably 1 mm or less.

  The depth of the groove can be set to 5 μm or more, for example. The coating film may remain at the bottom of the groove, or the coating film may be completely removed by the fluid, and the metal foil may be exposed at the bottom of the groove.

  In the groove forming step, for example, the groove may be formed by spraying fluid onto the coating film in a state where the position of the coating film and the position of the nozzle that blows out the fluid are fixed. In this case, a groove having a shape corresponding to the shape of the nozzle outlet can be formed in the coating film.

  Further, in the groove forming step, the groove may be formed by spraying the fluid on the coating film while moving the position of spraying the fluid relative to the coating film. In this case, for example, the nozzle that blows out the fluid with the position of the metal foil fixed may be moved, or the metal foil may be moved with the position of the nozzle fixed.

  From the viewpoint of improving the productivity of the electrode, in the groove forming step, it is preferable to form a groove by spraying a fluid on the coating film while moving the metal foil. In this case, since the groove can be formed in the groove forming step without stopping the conveyance of the metal foil, the productivity of the electrode can be further improved.

  In the groove forming step, it is preferable to extend the groove at least from the peripheral edge of the coating film in a plan view as viewed from the thickness direction of the coating film to the inside of the peripheral edge. In this case, when an electrode assembly or an electrode winding body is assembled using the electrode, the groove of the active material layer can be extended from the outer surface of the electrode assembly or the like to the inside. Therefore, it is possible to further promote the supply of the electrolytic solution from the outside to the inside of the electrode assembly or the like and the discharge of the gas from the inside to the outside.

  In the drying step, the active material layer is formed on the metal foil by drying the coating film provided with the grooves. As a method for drying the coating film, a known drying method such as warm air drying, infrared drying, hot plate drying, or the like can be employed.

  After the drying step, a pressing step of pressing the active material layer and compressing in the thickness direction may be performed as necessary. By performing the pressing step, the porosity of the active material layer can be adjusted and the electrode reaction can be further promoted.

  The electrode manufactured by the above manufacturing method may be a single-sided electrode in which an active material layer is provided on one side of a metal foil, or a double-sided electrode in which an active material layer is provided on both sides of a metal foil. May be. When producing a single-sided electrode, the coating step, the groove forming step, and the drying step described above may be sequentially performed on one side of the metal foil.

  When producing a double-sided electrode, for example, after a coating film is formed on both sides of a metal foil in the coating step, a method of sequentially performing a groove forming step and a drying step can be employed. In this case, the groove forming step may be performed on only one of the two coating films, or may be performed on both coating films.

  In addition, after performing the coating step, the groove forming step, and the drying step in order to produce the above-described single-sided electrode, the active material layer is formed on the back surface of the metal foil in the single-sided electrode, that is, the surface on which the active material layer is not provided. It is also possible to produce a double-sided electrode. In this case, the active material layer provided on the back surface may or may not have a groove. In the case of forming an active material layer having grooves on the back surface, the above-described coating process, groove forming process, and drying process may be sequentially performed.

  In the double-sided electrode, the active material layer provided on one surface of the metal foil and the active material layer provided on the other surface may be the same or different. For example, a bipolar electrode can be manufactured by forming a positive electrode active material layer containing a positive electrode active material on one surface and forming a negative electrode active material layer containing a negative electrode active material on the other surface.

  The electrode produced by the above manufacturing method may be configured as, for example, an electrode for a nickel metal hydride storage battery or an electrode for a lithium ion secondary battery. Nickel metal hydride storage batteries require water and hydroxide ions for electrode reactions both during charging and discharging. Therefore, if the supply of the electrolyte solution to the inside of the electrode assembly is delayed, the internal resistance may be increased. In addition, in the nickel metal hydride storage battery, gas is generated during overcharge, and gas tends to accumulate inside the electrode assembly.

  On the other hand, since the electrode produced by the above manufacturing method has a groove in the active material layer, the supply of the electrolytic solution and the discharge of the gas can be promoted. Therefore, by incorporating the electrode produced by the above manufacturing method into a nickel metal hydride storage battery, it is possible to effectively suppress an increase in internal resistance and suppress gas accumulation. Therefore, the electrode manufactured by the above manufacturing method is suitable for a nickel metal hydride storage battery.

Example 1
An embodiment of the electrode manufacturing method will be described with reference to FIGS. As shown in FIG. 1, the manufacturing method of the electrode 1 of this example includes a coating step S <b> 1 in which a slurry containing an active material and a binder is applied on a metal foil 2 to form a coating film 30, and a fluid is applied to the coating film 30. 2, the groove forming step S <b> 2 for forming a groove 31 that is recessed from the surroundings in part of the coating film 30 as shown in FIG. 2, and the coating film 30 provided with the groove 31 are dried to dry the active material layer 3. And a drying step S3 for forming. Hereinafter, each process is demonstrated in detail.

  In this example, as shown in FIG. 1, a nickel foil roll 20 having a thickness of 10 μm is prepared as the metal foil 2. The metal foil 2 is pulled out from the roll 20, and the coating process S <b> 1, the groove forming process S <b> 2 and the drying process S <b> 3 are sequentially performed while transporting in the transport direction 400.

  The metal foil 2 drawn out from the roll 20 is transported along the transport direction 400 and guided to the die coater 41. And the coating film 30 is formed on the single side | surface of the metal foil 2 by apply | coating a slurry using the die-coater 41 (application | coating process S1). The slurry of this example includes an active material and a binder that bonds the active materials to each other or the active material and the metal foil 2. Moreover, the coating film 30 is exhibiting the rectangular shape in the planar view seen from the thickness direction, as shown in FIG. In addition to the die coater 41, a known coating device such as a roll coater or a gravure printer can be employed as a device for applying the slurry in the coating step S1.

  As shown in FIGS. 1 and 2, the metal foil 2 on which the coating film 30 is formed is further transported along the transport direction 400 and guided to the blower 42. The blower 42 includes a nozzle 421 through which a gas G as a fluid is blown, and a gas supply unit (not shown) that supplies the gas G to the nozzle 421. In this example, as shown in FIG. 2, the gas foil B blown from the tip of the nozzle 421 is blown onto the coating film 30 while moving the metal foil 2 along the transport direction 400, thereby forming a groove 31 in the coating film 30. Is formed (groove forming step S2). Accordingly, the groove 31 extending over the entire length in the direction parallel to the transport direction 400 can be formed in the coating film 30. That is, in the groove forming step S <b> 2 of this example, the film 30 extends from one peripheral edge 301 of the coating film 30 to the other peripheral edge 302 through the inner side of the peripheral edge 301 in the direction parallel to the transport direction 400. A groove 31 can be formed.

  Specifically, the gas supply unit of the blower 42 in this example is a compressor that compresses air and supplies the compressed air to the nozzle 421. The nozzle 421 is arranged so that the gas G can be blown out in a direction parallel to the thickness direction of the metal foil 2. The nozzle 421 may be arranged so that the gas G can be blown out in a direction inclined with respect to the thickness direction of the metal foil 2. In this case, by disposing the nozzle 421 so that the gas G is blown obliquely rearward with respect to the transport direction 400, scattering of the slurry in the transport direction 400 can be reduced.

  As shown in FIG. 1, the metal foil 2 is further transported along the transport direction 400 after the groove forming step S <b> 2 and guided to the tunnel-type heating furnace 43. And while the shape of the groove | channel 31 is maintained, the metal foil 2 is heated within the heating furnace 43, and the coating film 30 is dried. Thereby, the active material layer 3 provided with the groove | channel 31 is formed on the metal foil 2 (drying process S3). Thereafter, the electrode 1 can be obtained by cutting the metal foil 2 into a desired shape.

  As shown in FIG. 3, the electrode 1 obtained by the manufacturing method of this example has an active material layer 3 that has a rectangular shape in plan view as viewed from the thickness direction of the metal foil 2. In the center of the active material layer 3, one groove 31 parallel to the long side direction of the active material layer 3 is extended. As shown in FIG. 4, the metal foil 2 is exposed at the bottom of the groove 31. Further, the side surface 311 of the groove 31 has an arc shape that expands away from the metal foil 2 in the cross section in the thickness direction of the metal foil 2.

  Next, the function and effect of this example will be described. In the manufacturing method of the electrode 1 of this example, after forming the coating film 30 containing an active material and a binder on the metal foil 2, the groove 31 is formed by spraying a gas G as a fluid on the coating film 30 before drying. Form. Therefore, in the groove forming step S2, the groove 31 can be formed without bringing a processing tool such as a press die into contact with the coating film 30. Therefore, it is possible to avoid adhesion of foreign matters derived from the processing tool.

  Moreover, the manufacturing method of this example can suppress scattering of the coating film 30 by the gas G being sprayed by adjusting the pressure of the gas G, the spraying direction, and the like. Even if a part of the coating film 30 is scattered in the groove forming step S <b> 2 and a splash of the slurry is generated, the splash of the slurry adheres to the coating film 30 in the undried state, so that the splash is deposited on the metal foil 2. The coating film 30 can be integrated. Therefore, according to the manufacturing method of this example, it is possible to avoid the generation of foreign matters such as dross in laser processing.

  As described above, according to the manufacturing method of this example, it is possible to avoid the generation of foreign matters in the groove forming step S2. Therefore, the groove 31 can be formed in the active material layer 3 without adhering foreign matter.

  In this example, the gas G is used as the fluid in the groove forming step S2. Therefore, it is possible to avoid the sprayed gas G from remaining in the coating film 30 and to form the groove 31 without changing the composition of the coating film 30. Moreover, in the drying step S3 performed later, the coating film 30 can be dried in a shorter time than when a liquid is used as the fluid.

  Moreover, in groove | channel formation process S2, the gas G is sprayed on the coating film 30, moving the metal foil 2, and the groove | channel 31 is formed. Thereby, in groove | channel formation process S2, formation of the groove | channel 31 can be performed, without stopping conveyance of the metal foil 2. FIG. Therefore, the productivity of the electrode 1 can be further improved.

  In the groove forming step S <b> 2, the groove 31 extends from the peripheral edge portions 301 and 302 of the coating film 30 in a plan view as viewed from the thickness direction of the coating film 30 to the inner side of the peripheral edge portions 301 and 302. Therefore, when the electrode assembly or the electrode winding body is assembled using the electrode 1 obtained by the above manufacturing method, the groove 31 of the active material layer 3 is extended from the outer surface of the electrode assembly or the like to the inside. Can do. Therefore, it is possible to further promote the supply of the electrolytic solution from the outside to the inside of the electrode assembly or the like and the discharge of the gas from the inside to the outside.

(Example 2)
This example is an example of a method for manufacturing the electrode 102 having the active material layer 3 having the grooves 31 on both surfaces of the metal foil 2. Of the reference numerals used in the present embodiment, the same reference numerals as those used in the above-described embodiments indicate the same constituent elements as those in the above-described embodiments unless otherwise specified.

  In the coating step S102 of this example, as shown in FIG. 5, die coaters 41 are arranged on the front side and the back side of the metal foil 2, respectively. The metal foil 2 conveyed along the conveyance direction 400 is guided to these die coaters 41, and the slurry is applied to both surfaces of the metal foil 2, thereby forming the coating films 30 (30a, 30b) on both surfaces of the metal foil 2. Is done.

  In the groove forming step S202 of this example, the nozzles 421 of the blowers 42 are arranged on the front side and the back side of the metal foil 2, respectively. After the coating step S102, the metal foil 2 transported along the transport direction 400 is guided to these nozzles 421, and each coating film is sprayed on each of the front-side coating film 30a and the back-side coating film 30b. A groove 31 (not shown) is formed in 30. Then, the electrode 102 can be obtained by guiding the metal foil 2 to the tunnel-type heating furnace 43 and drying the coating film 30 (drying step S3). The electrode 102 obtained by the above has the groove | channel 31 in both the active material layer 3a provided in the front side of the metal foil 2, and the active material layer 3b provided in the back side. Others are the same as in the first embodiment.

  In the double-sided electrode provided with the active material layer 3 on both sides of the metal foil 2, when providing grooves in both the front side active material layer 3a and the back side active material layer 3b of the metal foil 2, as in this example, What is necessary is just to dry these coating films 30 collectively in drying process S3, after forming the coating film 30 provided with the groove | channel 31 on both surfaces of the metal foil 2. FIG. Moreover, after performing the application | coating process S1, groove | channel formation process S2, and the drying process S3 in order on the surface of the metal foil 2 and forming the active material layer 3a provided with the groove | channel 31, it is again applied to the back surface of the metal foil 2 with application | coating process S1- The electrode 102 can also be produced by performing the drying step S3 to form the active material layer 3b. In any case, after performing the coating steps S1 and S102, and performing the groove forming steps S2 and S202 before the coating film 30 is dried, the same effects as those of the first embodiment can be obtained.

The method for producing an electrode according to the present invention is not limited to the above-described embodiments of Examples 1 and 2, and the configuration can be changed as appropriate without departing from the spirit of the present invention.
For example, in the first and second embodiments, the example in which the gas G is blown from the nozzle 421 fixed while moving the metal foil 2 in the groove forming steps S2 and S202 is shown. However, the fixing was performed while moving the nozzle 421. Gas G can also be sprayed onto the metal foil 2.

Moreover, the linear groove | channel 31 corresponding to the nozzle outlet is formed in the coating film 30 by using the nozzle which has an outlet extended in the direction parallel to the conveyance direction 400 of the metal foil 2 as a nozzle. It is also possible to do.
In Example 2, although the example which forms the active material layer 3 provided with the groove | channel 31 on both surfaces of the metal foil 2 was shown, the groove | channel 31 was formed in the active material layer 3a of the surface, and the active material layer 3b of the back surface was formed. May not form the groove 31.

DESCRIPTION OF SYMBOLS 1,102 Electrode 2 Metal foil 3 Active material layer 30 Coating film 31 Groove S1, S102 Application process S2, S202 Groove formation process S3 Drying process

Claims (4)

An application step of applying a slurry containing an active material and a binder onto a metal foil to form a coating film;
A groove forming step of forming a groove depressed from the surrounding in a part of the coating film by spraying fluid on the coating film;
Drying step of drying the coating film provided with the groove to form an active material layer;
A method for producing an electrode comprising:   The method for producing an electrode according to claim 1, wherein, in the groove forming step, the groove is formed by spraying the fluid onto the coating film while moving the metal foil.   The method for manufacturing an electrode according to claim 1, wherein the fluid is a gas.   4. The groove forming step according to claim 1, wherein the groove is extended from at least a peripheral portion of the coating film in a plan view viewed from a thickness direction of the coating film to an inner side of the peripheral edge portion. The manufacturing method of the electrode as described in claim | item.

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