JP2014099371A - Manufacturing method of electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode capable of improving applicability of electrode paste to a surface of a metal foil by effectively removing an oil content of the metal foil.SOLUTION: The manufacturing method of an electrode implements, as a preprocess of an application process, defatting of a metal foil 11 by blowing hot air and defatting of the metal foil 11 by contacting a removal member 25. By combining the defatting processes of different techniques, an oil content on one side (applied side) 11a of the metal foil 11 is effectively removed, thereby solving the problem that an edge of electrode paste 12 applied to the metal foil 11 is projected by a surface tension. Therefore, applicability of the electrode paste 12 to the surface of the metal foil 11 can be improved.

Description

  The present invention relates to an electrode manufacturing method.

  Conventionally, a method for manufacturing an electrode used in a power storage device includes a step of applying an electrode paste to a surface of a metal foil made of aluminum, for example, and then drying it to form an active material layer on the surface of the metal foil. Yes. Mineral oil for suppressing the growth of an oxide film during rolling is applied to the surface of the metal foil used in the step. If this oil component remains on the surface of the metal foil in the step of applying the electrode paste, there may be a problem that the edge of the electrode paste applied to the metal foil rises due to surface tension. For such a problem, there is an electrode manufacturing method including a step of removing oil on the surface of the metal foil prior to the step of applying the electrode paste (see, for example, Patent Documents 1 to 3).

JP 2008-258010 A JP 2008-159297 A JP 2004-195399 A

  In order to avoid the problem of the swell of the electrode paste, a technique of obtaining a metal foil from which oil has been removed in advance is also conceivable. However, if the oil is removed in advance, an oxide film is formed on the surface of the metal foil when the electrode paste is applied, and a conductive path between the active material layer and the interface of the metal foil is not formed as designed. There is a fear. Therefore, a technique capable of removing oil more effectively than the conventional technique is desired as a pre-process of the process of applying the electrode paste.

  The present invention has been made to solve the above problems, and provides an electrode manufacturing method capable of improving the application property of an electrode paste on the surface of a metal foil by effectively removing the oil content of the metal foil. The purpose is to do.

  In order to solve the above problems, an electrode manufacturing method according to the present invention is an electrode manufacturing method used in a power storage device, and includes an application step of applying an electrode paste containing an active material to an application surface of a metal foil, As a pre-process of the coating process, a hot air spraying process for blowing hot air on the coated surface of the metal foil and a removing member contact process for contacting a removing member for removing oil on the coated surface of the metal foil are provided. .

  In this electrode manufacturing method, degreasing of the metal foil by blowing hot air and degreasing of the metal foil by contacting the removing member are performed as a pre-process of the coating process. By combining these different methods of degreasing, the oil content on the coated surface of the metal foil is effectively removed, and the applicability of the electrode paste to the surface of the metal foil can be improved.

  Moreover, it is preferable to implement a removal member contact process after implementing a hot air spraying process. In this case, since the removal member contact step is performed in a state where the oil component is warmed by the hot air spraying step, the oil component on the coated surface of the metal foil can be more reliably removed.

  Moreover, it is preferable to implement a hot air spraying process after implementing a removal member contact process. In this case, since the hot air spraying process is performed in a state where the oil component is removed at a predetermined ratio by the removing member contact process, the time required for the hot air spraying process can be shortened.

  In the hot air spraying step, it is preferable that the temperature of the hot air is lower than the annealing temperature of the metal foil. In this case, it can suppress that distortion arises in metal foil in a hot air spraying process.

  In the removing member contact step, it is preferable that the roller around which the removing member is wound is brought into contact with the application surface of the metal foil. Thereby, a removal member contact process can be implemented suitably.

  Further, it is preferable that the metal foil is conveyed in a predetermined direction by the conveying means, and the roller is rotated in a direction opposite to the conveying direction of the metal foil in the removing member contact step. In this case, oil removal by the removing member can be more efficiently performed.

  According to the method for producing an electrode according to the present invention, the oil content of the metal foil is effectively removed, and the applicability of the electrode paste to the surface of the metal foil can be improved.

It is a schematic diagram which shows one Embodiment of the manufacturing method of the electrode which concerns on this invention. It is a perspective view which shows the mode of a hot air spraying process. It is a schematic diagram which shows the modification of the manufacturing method of the electrode which concerns on this invention.

  Hereinafter, a preferred embodiment of an electrode manufacturing method according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view showing an embodiment of a method for producing an electrode according to the present invention. Each step of the electrode manufacturing method shown in the figure includes a transport unit (transport means) 2 that transports the metal foil 11 in a predetermined direction, a removal unit 3 that removes oil from the surface of the metal foil 11, and the metal foil 11. This is realized by a manufacturing apparatus 1 that includes a coating unit 4 that coats the coating surface of the electrode paste 12 and a drying unit 5 that dries the electrode paste 12 coated on the metal foil 11. In the present embodiment, the one surface 11 a of the metal foil 11 is an application surface of the electrode paste 12.

  The conveyance unit 2 includes a feeding roller 21 that feeds the metal foil 11 wound in a roll shape, a winding roller 22 that winds the metal foil 11 that has undergone each process into a roll shape, and a gap between the feeding roller 21 and the winding roller 22. The plurality of auxiliary rollers 23 are arranged. The conveyance speed of the metal foil 11 by the conveyance unit 2 is, for example, 10 m / min.

  The metal foil 11 conveyed by the conveyance unit 2 is an aluminum foil rolled to a thickness of, for example, about several tens of μm. During rolling, mineral oil is applied to the surface of the metal foil 11 in order to suppress the formation of an oxide film, and the formation of an oxide film is suppressed on the surface of the metal foil 11 set on the feeding roller 21. A sufficient amount of mineral oil is attached.

  The removal unit 3 is disposed on the upstream side of the application unit 4. More specifically, the removing unit 3 contacts the hot air spraying unit 6 that performs a hot air spraying process for spraying hot air on the one surface 11 a of the metal foil 11 and the removing member that removes oil on the one surface 11 a of the metal foil 11. It is comprised by the removal member contact part 7 which implements the removal member contact process to be performed. For example, as shown in FIG. 2, the hot air blowing unit 6 has a plurality of jet nozzles 8 arranged in a direction substantially perpendicular to the conveying direction of the metal foil 11 (width direction of the metal foil 11).

  Each jet nozzle 8 is disposed substantially perpendicular to the metal foil 11, and blows hot air having a temperature lower than the annealing temperature of the metal foil 11 toward the metal foil 11 passing immediately below. The annealing temperature of the metal foil 11 is a temperature at which distortion such as recrystallization or phase transition occurs in the metal forming the metal foil 11. In this embodiment, since aluminum is used as the metal foil 11, the annealing temperature is about 120 ° C. On the other hand, when the temperature of the hot air is too low, it is difficult to obtain an oil removal effect.

  Therefore, the temperature of the hot air is preferably 40 ° C. or higher and lower than 120 ° C., for example, and more preferably 40 ° C. or higher and lower than 100 ° C. The hot air blown by each jet nozzle 8 may use air, but may use an inert gas such as nitrogen. In this case, it can suppress that an oxide film is formed on the surface of the metal foil 11 after blowing hot air. Moreover, a heater etc. may be provided in the front | former stage of the hot air spraying part 6, and the preheat may be given to the metal foil 11 which goes to the hot air spraying part 6. FIG. The time for blowing the hot air is preferably about 0.5 to 1.5 minutes, for example.

  For example, as shown in FIG. 1, the removal member contact portion 7 includes a contact roller 24 around which the removal member 25 is wound. As the removing member 25, for example, an oil wiping sheet made of pulp, polypropylene, nonwoven fabric, or the like is used. The contact roller 24 rotates in a direction opposite to the conveying direction of the metal foil 11, and the removal member 25 on the surface of the contact roller 24 comes into contact with the one surface 11 a of the metal foil 11, thereby removing oil on the surface of the metal foil 11. It is supposed to be. For example, the rotation speed of the contact roller 24 is set so that the rotation speed of the removing member 25 substantially matches the conveyance speed of the metal foil 11.

  Note that the contact roller 24 is not necessarily rotatable. Further, the contact roller 24 may be slidable at a predetermined cycle in a direction substantially perpendicular to the conveying direction of the metal foil 11 (width direction of the metal foil 11). Further, the removing member 25 may be impregnated with an alkaline solution such as sodium hydroxide. In this case, the one surface 11a of the metal foil 11 is etched by the alkaline solution together with the oil removal, and the surface of the one surface 11a can be roughened. Therefore, it is possible to improve the adhesion when the electrode paste 12 is applied to the one surface 11a of the metal foil 11 at the application portion 4.

  The application unit 4 is a part that performs an application process of applying the electrode paste 12, and includes a tank 26 that stores the electrode paste 12, a supply pipe 27 that supplies the electrode paste 12 toward the metal foil 11, and a pump 28. Have. The electrode paste 12 supplied from the supply pipe 27 is applied to one surface 11 a of the metal foil 11 guided by the coating roll 29 and the comma roll 30. The metal foil 11 coated with the electrode paste 12 is sent to the drying unit 5 by the auxiliary roller 23.

  The electrode paste 12 is a paste containing, for example, an active material, a binder, and a solvent. The electrode paste 12 may further contain a conductive additive such as acetylene black. The active material may be either a positive electrode active material or a negative electrode active material. Examples of the positive electrode active material include composite oxide, metallic lithium, and sulfur. The composite oxide includes at least one of manganese, nickel, cobalt, and aluminum and lithium.

  Examples of the negative electrode active material include carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, alkali metals such as lithium and sodium, metal compounds, SiOx (0.5 ≦ x ≦ 1.5 ) And the like, and boron-added carbon.

  The binder may be a thermoplastic resin such as polyamideimide or polyimide, or may be a polymer resin having an imide bond in the main chain. The solvent may be an organic solvent such as NMP (N-methylpyrrolidone), methanol, methyl isobutyl ketone, or water.

  The drying unit 5 is a drying furnace having a temperature adjustment function, for example. In the drying unit 5, the electrode paste 12 applied to the one surface 11 a of the metal foil 11 is dried at 100 ° C. for 2 minutes, for example. Thereby, the solvent in the electrode paste 12 is removed, and an electrode is manufactured. The electrode is used in a power storage device such as a secondary battery or an electric double layer capacitor. Examples of the secondary battery include a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery. The metal foil 11 functions as a current collector for these batteries.

  As described above, in this electrode manufacturing method, degreasing of the metal foil 11 by blowing hot air and degreasing of the metal foil 11 by contact with the removing member 25 are performed as pre-processes of the coating process. By combining these different methods of degreasing, the oil content of the one surface 11a of the metal foil 11 is effectively removed, and the edge of the electrode paste 12 applied to the metal foil 11 is raised by the surface tension. The problem can be avoided. Therefore, the applicability of the electrode paste 12 to the surface of the metal foil 11 can be improved.

  Moreover, in this electrode manufacturing method, the removal member contact step is performed after the hot air spraying step. In this method, since the removal member contact step is performed in a state where the oil component is warmed by the hot air spraying step, the oil component on the one surface 11a of the metal foil 11 can be more reliably removed.

  Further, in this electrode manufacturing method, the metal foil 11 is conveyed in a predetermined direction by the conveyance unit 2, and the contact roller 24 is rotated in the direction opposite to the conveyance direction of the metal foil 11 in the removal member contact process. . Thereby, oil removal by the removal member 25 can be implemented more efficiently.

  The present invention is not limited to the above embodiment. For example, in the embodiment described above, the removal member contact process is performed after the hot air spraying process is performed. However, as shown in FIG. 3, the hot air spraying process may be performed after the removal member contact process. In this case, since the hot air spraying process is performed in a state where the oil component is removed at a predetermined ratio by the removing member contact process, the time required for the hot air spraying process can be shortened.

  In the above-described embodiment, the contact roller 24 is rotated in the direction opposite to the conveyance direction of the metal foil 11 in the removal member contact process, but the contact roller 24 is rotated in the same direction as the conveyance direction of the metal foil 11. You may let them. The rotation speed of the contact roller 24 may be different from the rotation speed of the feeding roller 21 and the winding roller 22.

  Further, in the above-described embodiment, the electrode paste 12 is applied only to the one surface 11a of the metal foil 11, but the electrode paste 12 may be applied to both surfaces of the metal foil 11 in the application process. In this case, if the jet nozzle 8 in the hot air blowing part 6 and the contact roller 24 with the removal member 25 in the removal member contact part 7 are arranged on both sides of the metal foil 11, the same effect as the above embodiment is obtained. It is done.

  DESCRIPTION OF SYMBOLS 2 ... Conveying part (conveying means), 4 ... Application | coating part, 6 ... Hot air spraying part, 7 ... Removal member contact part, 11 ... Metal foil, 11a ... One side (application surface), 12 ... Electrode paste, 24 ... Contact roller (Roller), 25... Removal member.

Claims (6)

A method of manufacturing an electrode used in a power storage device,
Including an application step of applying an electrode paste containing an active material to the application surface of the metal foil,
As a pre-process of the coating process,
A hot air blowing step of blowing hot air on the coated surface of the metal foil;
A removing member contact step of bringing a removing member that removes oil into contact with the coated surface of the metal foil.   The method for manufacturing an electrode according to claim 1, wherein the removing member contact step is performed after the hot air spraying step.   The method for manufacturing an electrode according to claim 1, wherein the hot air spraying step is performed after the removing member contacting step.   The method for producing an electrode according to any one of claims 1 to 3, wherein, in the hot air blowing step, the temperature of the hot air is set to be lower than the annealing temperature of the metal foil.   5. The method for manufacturing an electrode according to claim 1, wherein, in the removing member contact step, a roller around which the removing member is wound is brought into contact with the application surface of the metal foil. The metal foil is conveyed in a predetermined direction by a conveying means,
6. The method of manufacturing an electrode according to claim 5, wherein, in the removing member contact step, the roller is rotated in a direction opposite to a conveying direction of the metal foil.

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