Electrode manufacturing method

Abstract

To provide a method of manufacturing an electrode capable of suppressing abrasion of a metal foil or rolls.SOLUTION: Provided is a method of manufacturing an electrode 70 that forms a first electrode layer 61 by pressing first wet powder P1 against a first surface S1 side of a metal foil 50 and forms a second electrode layer 62 by pressing second wet powder P2 against a second surface S2 side of the metal foil 50, using a first roll 11, a second roll 12, a third roll 13, and a fourth roll 14 that are made of a metal. The method includes: a first step Pr1 of forming a binding layer 63 on the second surface S2 of the metal foil 50; a second step Pr2 of forming the first electrode layer 61 on the first surface S1 of the metal foil 50 between the first roll 11 and the second roll 12; and a third step Pr3 of forming the second electrode layer 62 on the binding layer 63 between the third roll 13 and the fourth roll 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an electrode. [Background technology]

[0002] In the coating manufacturing apparatus described in Patent Document 1, the object passes between a first roll and a second roll that rotates in the opposite direction to the rotation of the first roll. The object is transported in a direction corresponding to the rotation of the second roll. A paint mix is ​​supplied from a paint supply hopper between the first roll and the second roll. The coating is manufactured by applying the paint mix to the object in the form of a coating film. Metal is used as the material for the first roll and the second roll. When a negative electrode plate is manufactured by the coating manufacturing apparatus described in Patent Document 1, a negative electrode mix paint containing a negative electrode active material, a binder, and a solvent is applied to a copper foil as the object in the form of a coating film to manufacture the negative electrode plate.

[0003] Patent Document 2 discloses a bipolar electrode in which a positive electrode active material layer and a negative electrode active material layer are formed on a metal foil. The negative electrode active material layer is formed on a first surface of the metal foil. The positive electrode active material layer is formed on a second surface of the metal foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-164717 A [Patent Document 2] JP 2012-234823 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, it has been considered to form bipolar electrodes using the same method as the coating manufacturing apparatus described above. However, when the coating object is a metal foil, the metal foil comes into contact with the roll when the composite coating is first applied to the metal foil. This may cause wear of the metal foil or the roll. [Means for solving the problem]

[0006] The method for manufacturing an electrode that solves the above-mentioned problems includes a first electrode layer formed by pressing a first wet powder containing an electrode active material, a binder, and a solvent onto a first surface of a strip-shaped metal foil using a first roll, a second roll, a third roll, and a fourth roll, and a second electrode layer formed by pressing a second wet powder containing an electrode active material, a binder, and a solvent onto a second surface of the metal foil, the method comprising the steps of: a first step of forming a binder layer containing a binder and a conductive assistant as main components onto the second surface; a second step of passing the metal foil between the first roll and the second roll by the rotation of the second roll in a state of contact with the first roll and the second roll, and forming the first electrode layer on the first surface side between the first roll and the second roll; and a third step of passing the metal foil and the first electrode layer between the third roll and the fourth roll by the rotation of the third roll in a state of the first electrode layer being in contact with the third roll after the second step, and forming the second electrode layer on the bonding layer between the third roll and the fourth roll. The electrode active material contained in the first wet powder is either a positive electrode active material or a negative electrode active material, and the electrode active material contained in the second wet powder is the other of a positive electrode active material and a negative electrode active material. .

[0007] According to this, when the first electrode layer is formed on the metal foil in the second step, the bonding layer formed in the first step contacts the second roll. Therefore, wear of the metal foil or the second roll can be suppressed. Similarly, when the second electrode layer is formed on the metal foil in the third step, the first electrode layer contacts the third roll, so wear of the metal foil or the third roll can be suppressed. Therefore, wear of the metal foil or the roll can be suppressed.

[0009] In the above-described method for producing an electrode, the third step may be performed in a state in which the first electrode layer formed on the metal foil transported by rotation of the second roll is in contact with the third roll.

[0010] According to this, the second and third steps can be performed on the continuously transported metal foil, so that the first and second electrode layers can be continuously formed on the metal foil. Compared to a case in which the metal foil after the second step is once wound up and transported, the wound up metal foil is transported again to perform the third step, the electrodes can be manufactured more efficiently.

[0011] In the above-mentioned method for manufacturing an electrode, the first roll, the second roll, the third roll, and the fourth roll may be made of metal. According to this, since the first roll, the second roll, the third roll, and the fourth roll are made of metal, which is harder than resin and the like, wear of the four rolls can be easily suppressed. Furthermore, since the four rolls are made of metal, the rigidity of the four rolls can be ensured. Therefore, deformation of the rolls when performing the second and third steps can be suppressed. Therefore, variation in thickness of the first electrode layer and the second electrode layer formed on the metal foil can be suppressed. Effect of the Invention

[0012] According to the present invention, wear of the metal foil or roll can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an electrode manufacturing apparatus. [Diagram 2] FIG. 4 is a cross-sectional perspective view showing the formation of a bonding layer on the second surface of the metal foil. [Diagram 3] FIG. 4 is a cross-sectional perspective view showing a state where a first electrode layer is formed on a first surface of the metal foil. [Figure 4] FIG. 4 is a cross-sectional perspective view showing a state where a second electrode layer is formed on the second surface side of the metal foil. [Diagram 5] Cross-sectional view taken along line 5-5 in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the electrode manufacturing method will now be described with reference to Figures 1 to 5. In describing the electrode manufacturing method, the configuration of an electrode manufacturing apparatus will also be described. 1, the electrode manufacturing apparatus 1 is an apparatus that presses a first moist powder P1 against a first surface S1 of a long strip-shaped metal foil 50 to form a first electrode layer 61, and presses a second moist powder P2 against a second surface S2 of the metal foil 50 to form a second electrode layer 62. The metal foil 50 is continuously transported in the electrode manufacturing apparatus 1. The electrode manufacturing apparatus 1 is an apparatus that continuously forms the first electrode layer 61 and the second electrode layer 62 on the metal foil 50 that is continuously transported.

[0015] <Electrode configuration> As shown in FIG. 1, the electrode 70 includes a metal foil 50, a first electrode layer 61, a second electrode layer 62, and a bonding layer 63.

[0016] The metal foil 50 is formed by bonding a long strip of copper foil 51 and a long strip of aluminum foil 52 together. The metal foil 50 has a thickness of 1 mm or less. The width and length of the metal foil 50 are greater than the thickness. The first surface S1 of the metal foil 50 is the opposite surface of the copper foil 51 that is bonded to the aluminum foil 52 among both surfaces in the thickness direction. The second surface S2 of the metal foil 50 is the opposite surface of the aluminum foil 52 that is bonded to the copper foil 51 among both surfaces in the thickness direction. The metal foil 50 may be one surface of the aluminum foil 52 that is copper plated. The metal foil 50 may be formed to be one sheet of one type of metal material. The thicknesses of the metal foil 50, the first electrode layer 61, the second electrode layer 62, and the bonding layer 63 shown in FIG. 1 are exaggerated.

[0017] The binder layer 63 is provided on the second surface S2 of the metal foil 50. The second electrode layer 62 is formed on the binder layer 63. The binder layer 63 bonds the second electrode layer 62 to the second surface S2 of the metal foil 50. The second electrode layer 62 is formed on the opposite side to the metal foil 50 with respect to the binder layer 63. Therefore, it can be said that the second electrode layer 62 is formed on the second surface S2 side of the metal foil 50. The binder layer 63 is mainly composed of a binder and a conductive assistant. The binder layer 63 may contain other materials as long as it is mainly composed of a binder and a conductive assistant.

[0018] The binder may be any type that has the function of binding the metal foil 50 and the second electrode layer 62. Examples of the binder include rubber such as styrene-butadiene rubber, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine-containing rubber, and thermoplastic resins such as polypropylene and polyethylene. Examples of the binder include imide-based resins such as polyimide and polyamide-imide, alkoxysilyl group-containing resins, and acrylic-based resins containing monomer units such as acrylic acid and methacrylic acid. A polymer having a hydrophilic group may be used as the binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group.

[0019] Specific examples of polymers having hydrophilic groups include polyacrylic acid and carboxymethyl cellulose. Specific examples of polymers having hydrophilic groups include polymers containing carboxyl groups in the molecule, such as polymethacrylic acid, or polymers containing sulfo groups, such as poly(p-styrenesulfonic acid). Specific examples of polymers having hydrophilic groups include polyvinylpyrrolidone and polyvinyl alcohol. Polymers containing many carboxyl groups and / or sulfo groups, such as polyacrylic acid or copolymers of acrylic acid and vinylsulfonic acid, are water-soluble.

[0020] The polymer having a hydrophilic group is preferably a water-soluble polymer, and in terms of chemical structure, is preferably a polymer containing multiple carboxyl groups and / or sulfo groups in one molecule. As the binder, the above-mentioned various binders may be used alone or in combination of two or more kinds.

[0021] The conductive assistant may be any chemically inactive electron conductor. Examples of the conductive assistant include carbon black, which is a carbonaceous fine particle, graphite, vapor-grown carbon fiber, carbon nanotubes, and various metal particles. Examples of carbon black include acetylene black, Ketjen Black (registered trademark), furnace black, and channel black. These conductive assistants can be added to the electrode material alone or in combination of two or more kinds.

[0022] <Configuration of the first moist powder and the second moist powder> The first wet powder P1 and the second wet powder P2 are materials with poor fluidity that contain an electrode active material, a binder, and a solvent. The first wet powder P1 and the second wet powder P2 are materials in which solid content is dispersed in a solvent in a range of 60% by mass to 90% by mass. The solid content is what remains after the solvent is separated from the first wet powder P1 and the second wet powder P2 by drying or the like. The solid content is an electrode material that contains an electrode active material and a binder.

[0023] The electrode active material contained in the first wet powder P1 is a negative electrode active material. As the negative electrode active material, a material capable of absorbing and releasing a charge carrier can be used. The negative electrode active material is not particularly limited as long as it is a simple substance, an alloy, or a compound capable of absorbing and releasing a charge carrier such as lithium ions. For example, as the negative electrode active material, lithium, carbon, silicon, germanium, tin, and other group 14 elements, and aluminum, indium, and other group 13 elements may be used alone. As the negative electrode active material, zinc, cadmium, and other group 12 elements, antimony, bismuth, and other group 15 elements, magnesium, calcium, and other alkaline earth metals, and silver, gold, and other group 11 elements may be used alone. Specific examples of alloys include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, and Co-Sn alloys. Specific examples of compounds include carbon-based materials such as various graphites, and silicon-based materials such as SiOx (0.3≦x≦1.6) that disproportionate to silicon simple substance and silicon dioxide. Specific examples of the compound include silicon alone or a composite of a silicon-based material and a carbon-based material. 12 Alternatively, oxides such as WO2, MoO2, and Fe2O3, or nitrides represented by Li3-xMxN (M=Co, Ni, and Cu) may be used. One or more of these may be used as the negative electrode active material.

[0024] The electrode active material contained in the second wet powder P2 is a positive electrode active material. The positive electrode active material is a layered rock salt structure represented by the general formula: Li a Ni b Co c Mn d D e O fExamples of the positive electrode active material include a lithium composite metal oxide represented by the formula: (0.2≦a≦2, b+c+d+e=1, 0≦e<1, 1.7≦f≦3, where D is at least one element selected from W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V), and Li2MnO3. Examples of the positive electrode active material include a metal oxide having a spinel structure such as LiMn2O4, a solid solution composed of a mixture of a metal oxide having a spinel structure and a layered compound, and a polyanion-based compound represented by LiMPO4, LiMVO4, or Li2MSiO4 (wherein M is selected from at least one of Co, Ni, Mn, and Fe). Examples of the positive electrode active material include taborite-based compounds represented by LiMPO4F (M is a transition metal) such as LiFePO4F, and borate-based compounds represented by LiMBO3 (M is a transition metal) such as LiFeBO3. Any metal oxide used as the positive electrode active material may have the above composition formula as the basic composition, and those in which the metal elements contained in the basic composition are replaced with other metal elements can also be used.

[0025] The binder contained in the first wet powder P1 and the second wet powder P2 may be one or more appropriately selected from those exemplified as the binder contained in the binder layer 63. The binder contained in the first wet powder P1 and the second wet powder P2 may be the same as or different from the binder contained in the binder layer 63. In this embodiment, it is preferable that the binder contained in the second wet powder P2 and the binder contained in the binder layer 63 are soluble in the same solvent.

[0026] The solvent for dispersing the solid content is not particularly limited, but water, N-methyl-2-pyrrolidone, alcohol, etc. are used. When the first wet powder P1 and the second wet powder P2 are pressed against the metal foil 50 by roll pressing as described below, it is preferable that the solvent contains N-methyl-2-pyrrolidone, which has excellent lubricity during compression on the pressing surface of the roll. Note that the solvent may be a material classified as an electrode material for part or all of the solvent. The solvent may also be one that can dissolve part or all of the solid content.

[0027] <Configuration of electrode manufacturing equipment> As shown in FIG. 1, the electrode manufacturing apparatus 1 includes a first roll 11, a second roll 12, a third roll 13, and a fourth roll 14. The first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 are made of metal. The first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 all have the same diameter. The axes of the first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 extend in the same direction so as to be parallel to each other. The roll surface of the first roll 11 and the roll surface of the fourth roll 14 are coated with a fluororesin. The first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 may be made of resin.

[0028] The second roll 12 is disposed at a position separated by a predetermined first distance from the first roll 11. The third roll 13 is disposed on the opposite side of the second roll 12 from the first roll 11. The third roll 13 is disposed at a position separated by a predetermined second distance from the second roll 12. The fourth roll 14 is disposed on the opposite side of the third roll 13 from the second roll 12. The fourth roll 14 is disposed at a position separated by a predetermined third distance from the third roll 13. The direction in which the axes of the four rolls 11, 12, 13, and 14 extend is defined as the axial direction. When the four rolls 11, 12, 13, and 14 are viewed from the outside in the axial direction, the four rolls 11, 12, 13, and 14 are disposed at the same height in the gravity direction A. Although not shown, when the four rolls 11, 12, 13, 14 are viewed from above in the direction of gravity A, first ends of the four rolls 11, 12, 13, 14 in the axial direction are arranged in a row in the horizontal direction B. Similarly, although not shown, when the four rolls 11, 12, 13, 14 are viewed from above in the direction of gravity A, second ends of the four rolls 11, 12, 13, 14 in the axial direction are arranged in a row in the horizontal direction B. Note that the second distance is sufficiently greater than the first distance and the third distance. The first distance is slightly smaller than the third distance.

[0029] The electrode manufacturing apparatus 1 includes a first guide roll 21, a second guide roll 22, a third guide roll 23, and a fourth guide roll 24. The first guide roll 21, the second guide roll 22, the third guide roll 23, and the fourth guide roll 24 are cylindrical. The first guide roll 21, the second guide roll 22, the third guide roll 23, and the fourth guide roll 24 all have the same diameter. The axes of the first guide roll 21, the second guide roll 22, the third guide roll 23, and the fourth guide roll 24 extend in the same direction so as to be parallel to each other. The direction in which the axes of the four guide rolls 21, 22, 23, and 24 extend is the same as the direction in which the axes of the four rolls 11, 12, 13, and 14 extend.

[0030] When the first guide roll 21 is viewed from the outside in the axial direction, the first guide roll 21 is disposed higher than the second roll 12 in the gravity direction A. When the first guide roll 21 is viewed from the outside in the axial direction, the first guide roll 21 is disposed closer to the second roll 12 than the third roll 13 in the horizontal direction B.

[0031] When the second guide roll 22 is viewed from the outside in the axial direction, the second guide roll 22 is disposed below the second roll 12 in the direction of gravity A. When the second guide roll 22 is viewed from the outside in the axial direction, the second guide roll 22 is disposed closer to the second roll 12 than the first roll 11 in the horizontal direction B. When the third guide roll 23 is viewed from the outside in the axial direction, the third guide roll 23 is disposed below the third roll 13 in the direction of gravity A. When the third guide roll 23 is viewed from the outside in the axial direction, the third guide roll 23 is disposed closer to the third roll 13 than the second roll 12 in the horizontal direction B. When the fourth guide roll 24 is viewed from the outside in the axial direction, the fourth guide roll 24 is disposed below the fourth roll 14 in the direction of gravity A. When the fourth guide roll 24 is viewed from the outside in the axial direction, the fourth guide roll 24 is disposed closer to the fourth roll 14 than the third roll 13 in the horizontal direction B.

[0032] The electrode manufacturing apparatus 1 includes a first power unit 31, a second power unit 32, and a control unit 33. The first power unit 31 rotates the second roll 12 around its axis. The second power unit 32 rotates the third roll 13 around its axis. The first power unit 31 and the second power unit 32 are, for example, electric motors. The control unit 33 includes a processor and a memory unit. The processor may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The memory unit includes a random access memory (RAM) and a read only memory (ROM). The memory unit stores program code or instructions configured to cause the processor to execute processing. The memory unit, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The control unit 33 may be configured by a hardware circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control unit 33, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as ASIC or FPGA, or a combination thereof. The control unit 33 controls the first power unit 31 and the second power unit 32 to control the rotation speed of the second roll 12 and the rotation speed of the third roll 13.

[0033] The first roll 11 and the second roll 12 are connected by a first power transmission mechanism (not shown). When the second roll 12 rotates, the first roll 11 is rotated in a direction opposite to the direction of rotation of the second roll 12 by the first power transmission mechanism. The first power transmission mechanism is a gear mechanism with a predetermined gear ratio. The gear ratio of the first power transmission mechanism is set so that the rotation speed of the first roll 11 is slightly slower than the rotation speed of the second roll 12. The third roll 13 and the fourth roll 14 are connected by a second power transmission mechanism (not shown). When the third roll 13 rotates, the second power transmission mechanism rotates the fourth roll 14 in a direction opposite to the direction of rotation of the third roll 13. The second power transmission mechanism is a gear mechanism with a predetermined gear ratio. The gear ratio of the second power transmission unit is set so that the rotation speed of the fourth roll 14 is slightly slower than the rotation speed of the third roll 13.

[0034] The metal foil 50 is wound around a supply roll (not shown). The supply roll is disposed above the first guide roll 21. The winding roll (not shown) is disposed to the side of the fourth guide roll 24. The metal foil 50 unwound from the supply roll passes through the electrode manufacturing apparatus 1 and is wound around the winding roll. Specifically, the metal foil 50 unwound downward from the supply roll is changed in orientation by the first guide roll 21 so as to face the second roll 12 and is transported in the horizontal direction B. The metal foil 50 whose orientation has been changed by the first guide roll 21 is wound around the second roll 12. After passing between the first roll 11 and the second roll 12, the metal foil 50 is changed in orientation by the second guide roll 22 so as to face the third guide roll 23 and is transported in the horizontal direction B. The metal foil 50 is changed in orientation by the third guide roll 23 so as to face upward in the gravity direction A and is transported in the gravity direction A. The metal foil 50, whose orientation has been changed by the third guide roll 23, is wound around the third roll 13. After passing between the third roll 13 and the fourth roll 14, the metal foil 50 is conveyed in the horizontal direction B with its orientation changed by the fourth guide roll 24 so as to face the winding roll. The metal foil 50 is then taken up on the winding roll. If the direction in which the metal foil 50 is conveyed is the conveying direction D, the power for conveying the metal foil 50 in the conveying direction D is the torque of the second roll 12 and the torque of the third roll 13. The conveying direction D coincides with the longitudinal direction of the long strip-shaped metal foil 50.

[0035] The electrode manufacturing apparatus 1 includes a first wet powder supplying device 41 and a second wet powder supplying device 42. The first wet powder supplying device 41 is filled with a first wet powder P1. The first wet powder supplying device 41 is disposed above the first roll 11 and the second roll 12. The lower portion of the first wet powder supplying device 41 is inserted between the first roll 11 and the second roll 12. The first wet powder supplying device 41 is disposed closer to the first roll 11 than the second roll 12. A supply port 41a of the first wet powder supplying device 41 is provided between the first roll 11 and the second roll 12, closer to the first roll 11 than the second roll 12.

[0036] The second wet powder supplying device 42 is filled with the second wet powder P2. The second wet powder supplying device 42 is disposed above the third roll 13 and the fourth roll 14. The lower part of the second wet powder supplying device 42 is inserted between the third roll 13 and the fourth roll 14. The second wet powder supplying device 42 is disposed closer to the fourth roll 14 than the third roll 13. The supply port 42a of the second wet powder supplying device 42 is provided between the third roll 13 and the fourth roll 14, closer to the fourth roll 14 than the third roll 13.

[0037] The electrode manufacturing apparatus 1 includes a drying device 80. Examples of the drying device 80 include a hot air drying oven, an IR drying oven, a hot plate, and a heat roll. The drying device 80 is disposed below the second roll 12.

[0038] In the above-mentioned electrode manufacturing apparatus 1, the flow of the metal foil 50 from upstream to downstream in the transport direction D and the manufacturing method of the electrode 70, including the order in which the first electrode layer 61 and the second electrode layer 62 are formed, will be described below.

[0039] <Electrode manufacturing method> The manufacturing method of the electrode 70 includes a first step Pr1, a second step Pr2, a third step Pr3, and a drying step Prd. The first step Pr1 is a step of forming the adhesive layer 63 on the second surface S2 of the metal foil 50.

[0040] As shown in FIG. 1 and FIG. 2, the first step Pr1 will be described in detail. In the first step Pr1, a paint mainly composed of a binder and a conductive assistant is pressed against the second surface S2 of the metal foil 50 to form the binder layer 63. In the first step Pr1 of this embodiment, the binder layer 63 is sufficiently dried by a drying device (not shown). A direction perpendicular to the longitudinal direction of the metal foil 50 and perpendicular to the thickness direction of the metal foil 50 is defined as the width direction C of the metal foil 50. The width direction C is perpendicular to the conveying direction D. In the first step Pr1, the coating width W3 of the binder layer 63 in the width direction C is set narrower than the width W1 of the width direction C of the metal foil 50. The binder layer 63 is pressed in the width direction C so as to form uncoated parts on both sides of the width direction C of the metal foil 50 where the binder layer 63 is not coated.

[0041] Next, the second step Pr2 will be described. The second step Pr2 is performed after the first step Pr1. The second step Pr2 is a step of forming the first electrode layer 61 on the first surface S1 between the first roll 11 and the second roll 12. In the second step Pr2, the metal foil 50 passes between the first roll 11 and the second roll 12 by the rotation of the second roll 12 with the binder layer 63 in contact with the second roll 12.

[0042] The second step Pr2 will be described in detail with reference to Fig. 1. The first surface S1 of the metal foil 50 passing through the electrode manufacturing apparatus 1 contacts the first guide roll 21. The metal foil 50 and the binder layer 63 pass between the first roll 11 and the second roll 12 due to the rotation of the second roll 12. The first surface S1 of the metal foil 50 and the first roll 11 are not in contact with each other.

[0043] With the metal foil 50 passing between the first roll 11 and the second roll 12, the first wet powder P1 is continuously supplied from the supply port 41a of the first wet powder supplying device 41. The first wet powder P1 is pressed against the first surface S1 of the metal foil 50 by the rotation of the first roll 11. The first wet powder P1 is pressed in the thickness direction of the metal foil 50 by the first roll 11 and the second roll 12. The first wet powder P1 is pressed against the first surface S1 of the metal foil 50, thereby forming a first electrode layer 61 on the first surface S1 of the metal foil 50. Here, the above-mentioned first distance is set so that the first electrode layer 61 formed on the first surface S1 of the metal foil 50 has a predetermined thickness. Note that the first electrode layer 61 immediately after passing between the first roll 11 and the second roll 12 has not had the solvent contained in the first wet powder P1 removed. The first electrode layer 61 immediately after passing between the first roll 11 and the second roll 12 is a precursor of the negative electrode active material layer.

[0044] 3, in the second step Pr2, a coating width W2 of the first wet powder P1 in the width direction C is set narrower than a width W1 of the metal foil 50 in the width direction C. The first wet powder P1 is pressed so as to form uncoated portions on both sides of the metal foil 50 in the width direction C where the first wet powder P1 is not pressed.

[0045] 2, 3, and 5, the application width W2 of the first wet powder P1 in the second step Pr2 is set to be wider than the application width W3 of the binder layer 63 in the first step Pr1. In the thickness direction of the metal foil 50, the binder layer 63 is located within the range in which the first electrode layer 61 is provided. In addition, in the thickness direction of the metal foil 50, the thickness of the binder layer 63 is set to be sufficiently thinner than the thickness of the first electrode layer 61 and the thickness of the second electrode layer 62 so as not to affect the second step Pr2.

[0046] Next, the drying step Prd will be described. The drying step Prd is a step in which the first electrode layer 61 is dried by a drying device 80. In the drying step Prd, the first electrode layer 61 is dried while being transported between the second roll 12 and the third roll 13.

[0047] 1, the metal foil 50 immediately after the first electrode layer 61 is formed is transported toward the drying device 80 with the binder layer 63 in contact with the second guide roll 22. The drying device 80 dries the first electrode layer 61. The first electrode layer 61 after drying is a negative electrode active material layer in which the solvent has been removed from the first wet powder P1.

[0048] Next, the third step Pr3 will be described. The third step Pr3 is performed after the second step Pr2. The third step Pr3 is a step of forming the second electrode layer 62 on the second surface S2 side of the metal foil 50 between the third roll 13 and the fourth roll 14. In the third step Pr3, with the first electrode layer 61 in contact with the third roll 13, the metal foil 50 and the first electrode layer 61 pass between the third roll 13 and the fourth roll 14 due to the rotation of the third roll 13.

[0049] More specifically, the binder layer 63 formed on the metal foil 50 that has passed through the drying device 80 contacts the third guide roll 23. As the third roll 13 rotates, the metal foil 50 on which the first electrode layer 61 has been formed passes between the third roll 13 and the fourth roll 14. The binder layer 63 formed on the metal foil 50 and the fourth roll 14 are not in contact with each other.

[0050] With the first electrode layer 61 and the metal foil 50 passing between the third roll 13 and the fourth roll 14, the second wet powder P2 is continuously supplied from the supply port 42a of the second wet powder supplying device 42. The second wet powder P2 is pressed against the binder layer 63 by the rotation of the fourth roll 14. The second wet powder P2 is pressed in the thickness direction of the metal foil 50 by the third roll 13 and the fourth roll 14. The second wet powder P2 is pressed against the binder layer 63 to form the second electrode layer 62 on the second surface S2 side of the metal foil 50. Here, the above-mentioned third distance is set so that the second electrode layer 62 formed on the second surface S2 side of the metal foil 50 has a predetermined thickness. Note that the second electrode layer 62 immediately after passing between the third roll 13 and the fourth roll 14 has not had the solvent contained in the second wet powder P2 removed. The second electrode layer 62 immediately after passing between the third roll 13 and the fourth roll 14 is a precursor of the positive electrode active material layer.

[0051] As shown in FIG. 4, in the third step Pr3, the coating width W3 of the second wet powder P2 in the width direction C is the same as the coating width W3 of the binder layer 63. 4 and 5, in the thickness direction of the metal foil 50, the second electrode layer 62 is formed at the same position as the position where the bonding layer 63 is provided. In the thickness direction of the metal foil 50, the second electrode layer 62 is located within the range where the first electrode layer 61 is provided.

[0052] As shown in FIG. 1, the metal foil 50 immediately after the second electrode layer 62 is formed is transported downstream in the transport direction D with the undried second electrode layer 62 in contact with the fourth guide roll 24. The second electrode layer 62 is appropriately dried in a drying device (not shown) arranged downstream of the fourth guide roll 24 in the transport direction D. When the drying of the second electrode layer 62 is completed, the electrode 70 is completed. The electrode 70 manufactured by the electrode manufacturing apparatus 1 is a pseudo bipolar electrode in which the copper foil 51 and the aluminum foil 52 are regarded as one metal foil 50. In the electrode 70, the first electrode layer 61 and the second electrode layer 62 are formed over the entire length of the metal foil 50 in the transport direction D. The manufacturing method of the electrode 70 is a manufacturing method in which a first electrode layer 61 and a second electrode layer 62 are formed on a strip-shaped metal foil 50 using four rolls 11, 12, 13, and 14, and has a first step Pr1, a second step Pr2, a third step Pr3, and a drying step Prd.

[0053] <Action of this embodiment> The operation of this embodiment will now be described. When the first electrode layer 61 is formed on the first surface S1 of the metal foil 50 in the second step Pr2, the bonding layer 63 formed on the second surface S2 of the metal foil 50 in the first step Pr1 comes into contact with the second roll 12. 1 Surface S 1and the first roll 11 do not come into contact with each other. Similarly, when the second electrode layer 62 is formed on the second surface S2 side of the metal foil 50 in the third step Pr3, the first electrode layer 61 formed on the first surface S1 of the metal foil 50 in the second step Pr2 comes into contact with the third roll 13. Furthermore, when the second electrode layer 62 is formed on the second surface S2 side of the metal foil 50 in the third step Pr3, the bonding layer 63 formed on the metal foil 50 does not come into contact with the fourth roll 14. That is, when the electrode 70 is manufactured, the two surfaces S1 and S2 of the metal foil 50 do not come into contact with the four rolls 11, 12, 13, and 14.

[0054] <Effects of this embodiment> The effects of this embodiment will be described. (1) Since the metal foil 50 does not come into contact with the second roll 12 and the third roll 13 that transport the metal foil 50 having a driving force, wear between the second roll 12 and the metal foil 50, and between the third roll 13 and the metal foil 50, can be suppressed. Furthermore, since both sides S1 and S2 of the metal foil 50 do not come into contact with the four rolls 11, 12, 13, and 14, wear between the metal foil 50 or the four rolls 11, 12, 13, and 14 can be suppressed. In addition, the intrusion of wear powder into the electrode 70 can be reduced.

[0055] (2) When the binder and solvent contained in the second moist powder P2 are, for example, aqueous, the second electrode layer 62 becomes an aqueous positive electrode active material layer. If the second electrode layer 62 is an aqueous positive electrode active material layer, there is a concern that the second electrode layer 62 may not adhere well to the metal foil 50. In this regard, in the present embodiment, the electrode active material contained in the second moist powder P2 is the positive electrode active material, and the second electrode layer 62 is formed on the binder layer 63. Therefore, even if the second electrode layer 62 is an aqueous positive electrode active material layer, the second electrode layer 62 can be adhered well to the metal foil 50 via the binder layer 63.

[0056] (3) Since the second step Pr2 and the third step Pr3 can be performed on the metal foil 50 that is continuously transported, the first electrode layer 61 and the second electrode layer 62 can be continuously formed on the metal foil 50. The electrode 70 can be manufactured more efficiently than when the metal foil 50 after the second step Pr2 is once wound up and transported, and then the wound up metal foil 50 is transported again to perform the third step Pr3.

[0057] (4) The first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 are made of metal, which is harder than resin and the like, and therefore it is easy to suppress wear of the four rolls 11, 12, 13, and 14. In addition, since the four rolls 11, 12, 13, and 14 are made of metal, the rigidity of the four rolls 11, 12, 13, and 14 can be ensured. Therefore, deformation of the four rolls 11, 12, 13, and 14 when the second step Pr2 and the third step Pr3 are performed can be suppressed. Therefore, it is possible to suppress the variation in thickness of the first electrode layer 61 and the second electrode layer 62 formed on the metal foil 50.

[0058] (5) The solvent of the first wet powder P1 constituting the first electrode layer 61 can be removed by the drying device 80. This makes it possible to make the first electrode layer 61 less likely to stick to the third roll 13 in the third step Pr3. (6) The roll surface of the first roll 11 and the roll surface of the fourth roll 14 are coated with a fluororesin. Therefore, when the first wet powder P1 is pressed against the first surface S1 of the metal foil 50 by the first roll 11, the first wet powder P1 can be easily released from the first roll 11. In addition, when the second wet powder P2 is pressed against the binder layer 63 by the fourth roll 14, the second wet powder P2 can be easily released from the fourth roll 14.

[0059] <Example of change> The present embodiment can be modified as follows: The present embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0060] The third step Pr3 is performed in a state in which the first electrode layer 61 formed on the metal foil 50 transported by the rotation of the second roll 12 is in contact with the third roll 13, but this is not limited to the above. For example, the metal foil 50 after the second step Pr2 may be wound up once, and then the third step Pr3 may be performed using the wound up metal foil 50.

[0061] The adhesive layer 63 may also be provided on the first surface S1 of the metal foil 50. In this case, the first electrode layer 61 is formed on the adhesive layer 63 formed on the first surface S1 of the metal foil 50. In other words, the first electrode layer 61 is formed on the first surface S1 side of the metal foil 50.

[0062] The electrode active material contained in the first wet powder P1 may be changed to a positive electrode active material, and the electrode active material contained in the second wet powder P2 may be changed to a negative electrode active material. In this case, the surface of the aluminum foil 52 of the metal foil 50 opposite to the copper foil 51 is defined as the first surface S1, and the surface of the copper foil 51 of the metal foil 50 opposite to the aluminum foil 52 is defined as the second surface S2. The coating width W3 of the second wet powder P2 is set to be wider than the coating width W2 of the first wet powder P1. Similarly, the coating width in the width direction C of the binder layer 63 is set to be the same as the coating width W2.

[0063] A surface treatment other than the fluororesin coating may be performed on the roll surface of the first roll 11 and the roll surface of the fourth roll 14. Any surface treatment other than the fluororesin coating may be performed as long as it can facilitate release of the first wet powder P1 from the first roll 11 and the second wet powder P2 from the fourth roll 14. The fluororesin coating on the roll surface of the first roll 11 and the roll surface of the fourth roll 14 may be omitted, and no surface treatment may be performed.

[0064] The first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 may have different diameters. The arrangement of the first roll 11, the second roll 12, the third roll 13, and the fourth roll 14 in the gravity direction A and the horizontal direction B may be changed as appropriate.

[0065] In the electrode manufacturing apparatus 1, the second guide roll 22 and the third guide roll 23 may be omitted. In this case, the metal foil 50 transported by the second roll 12 is directly transported to the third roll 13. In the electrode manufacturing apparatus 1, the first guide roll 21 and the fourth guide roll 24 may also be omitted.

[0066] The first roll 11 and the fourth roll 14 may be changed to rolls that rotate independently. In this case, a power unit that rotates each of the first roll 11 and the fourth roll 14 may be provided, and the power unit may be controlled by the control unit 33.

[0067] A drying device for drying the second electrode layer 62 may be provided upstream of the fourth guide roll 24 in the conveying direction D. The drying device 80 may be provided downstream of the third roll 13 and the fourth roll 14 in the transport direction D. In this case, the drying device 80 may dry the first electrode layer 61 and the second electrode layer 62 simultaneously.

[0068] In the first step Pr1, the binder layer 63 is sufficiently dried by a drying device (not shown), but it does not have to be dried. The binder layer 63 may be dried together with the first electrode layer 61 by a drying device 80. As in the above modification, the binder layer 63 may be dried together with the first electrode layer 61 and the second electrode layer 62.

[0069] The drying device 80 may be omitted. That is, the drying step Prd may be omitted from the method for producing the electrode 70. In such a modification, the solvent contained in the first wet powder P1 preferably contains N-methyl-2-pyrrolidone. [Explanation of symbols]

[0070] 1...electrode manufacturing apparatus, 11...first roll, 12...second roll, 13...third roll, 14...fourth roll, 21...first guide roll, 22...second guide roll, 23...third guide roll, 24...fourth guide roll, 31...first power section, 32...second power section, 33...control section, 41...first moist powder supply device, 41a...supply port, 42...second moist powder supply device, 42a...supply port, 50...metal foil, 51...copper foil, 52...aluminum foil, 61...first electrode layer, 62...second electrode layer, 63...binding layer, 70...electrode, 80...drying device, S1...first surface, S2...second surface, P1...first wet powder, P2...second wet powder, W2...coating width of first wet powder, W3...coating width of second wet powder, A...gravity direction, B...horizontal direction, C...width direction, D...conveying direction, Pr1...first process, Pr2...second process, Pr3...third process, Prd...drying process.

Claims

1. A method for manufacturing an electrode, comprising: pressing a first moist powder containing an electrode active material, a binder, and a solvent onto a first surface side of a strip-shaped metal foil using a first roll, a second roll, a third roll, and a fourth roll to form a first electrode layer; and pressing a second moist powder containing an electrode active material, a binder, and a solvent onto a second surface side of the metal foil to form a second electrode layer, a first step of forming an adhesive layer mainly composed of a binder and a conductive assistant on the second surface; a second step in which the metal foil passes between the first roll and the second roll by rotation of the second roll with the binder layer in contact with the second roll, and the first electrode layer is formed on the first surface side between the first roll and the second roll; a third step of passing the metal foil and the first electrode layer between the third roll and the fourth roll by rotation of the third roll with the first electrode layer in contact with the third roll after the second step, and forming the second electrode layer on the binder layer between the third roll and the fourth roll, the electrode active material contained in the first wet powder is either a positive electrode active material or a negative electrode active material, The method for manufacturing an electrode, wherein the electrode active material contained in the second wet powder is the other of a positive electrode active material and a negative electrode active material.

2. 2. The method for manufacturing an electrode according to claim 1, wherein the third step is performed in a state in which the first electrode layer formed on the metal foil transported by the rotation of the second roll is in contact with the third roll.

3. 3. The method for manufacturing an electrode according to claim 1, wherein the first roll, the second roll, the third roll, and the fourth roll are made of metal.

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