Electrode manufacturing apparatus and electrode manufacturing method

Abstract

To provide an electrode manufacturing method and an electrode manufacturing device capable of efficiently manufacturing an electrode with secured quality.SOLUTION: Provided is an electrode manufacturing device 1 and a method of manufacturing an electrode 70 that form a first electrode layer 61 by pressing first wet powder P1 against a first surface S1 of a current collector foil 50 and form a second electrode layer 62 by pressing second wet powder P2 against a second surface S2 side of the current collector foil 50, using a first drive roll 11, a second drive roll 12, a third drive roll 13, and a fourth drive roll 14. A speed Vc of the current collector foil 50 transported by the second drive roll 12 is faster than a rotation speed V2 of the second drive roll 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrode manufacturing apparatus and an electrode manufacturing method. [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 current collector foil. The negative electrode active material layer is formed on a first surface of the current collector foil. The positive electrode active material layer is formed on a second surface of the current collector 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, studies have been conducted on forming bipolar electrodes using techniques similar to those used in the manufacturing apparatus for the above-mentioned coating materials, and there is a demand for an electrode manufacturing method and electrode manufacturing apparatus that can efficiently manufacture electrodes with assured quality. [Means for solving the problem]

[0006] The method for manufacturing an electrode that solves the above-mentioned problems includes using a first drive roll, a second drive roll, a third drive roll, and a fourth drive roll to press a first wet powder containing an electrode active material, a binder, and a solvent against a first surface side of a long strip-shaped current collecting foil to form a first electrode layer, and pressing a second wet powder containing an electrode active material, a binder, and a solvent against a second surface side of the current collecting foil to form a second electrode layer, wherein the current collecting foil passes between the first drive roll and the second drive roll by rotation of the second drive roll while the current collecting foil is in contact with the second drive roll, and a second step of forming the second electrode layer on the second surface side between the third drive roll and the fourth drive roll, with the first electrode layer formed on the current collecting foil transported by the second drive roll after the first step being in contact with the third drive roll, causing the current collecting foil and the first electrode layer to pass between the third drive roll and the fourth drive roll by rotation of the third drive roll, and forming the second electrode layer on the second surface side between the third drive roll and the fourth drive roll, wherein a speed at which the current collecting foil is transported by the second drive roll is faster than a rotation speed of the second drive roll.

[0007] According to this, the first and second steps can be performed on the continuously transported current collecting foil, and the first and second electrode layers can be continuously formed on the current collecting foil. This allows electrodes to be manufactured more efficiently than when the current collecting foil after the first step is wound up once, transportation is stopped, and then the wound up current collecting foil is transported again to perform the second step.

[0008] The speed of the current collecting foil transported by the second drive roll is faster than the rotation speed of the second drive roll. Therefore, the current collecting foil slips against the second drive roll. The current collecting foil transported between the second drive roll and the third drive roll is pulled from the second drive roll toward the third drive roll by the rotation of the third drive roll. A kinetic frictional force that tries to keep the current collecting foil on the second drive roll acts on the current collecting foil on the second drive roll. Therefore, the current collecting foil transported between the second drive roll and the third drive roll is maintained in a pulled state. Since the current collecting foil transported between the second drive roll and the third drive roll is less likely to bend, when the second electrode layer is formed between the third drive roll and the fourth drive roll, the current collecting foil is less likely to wrinkle. Therefore, the quality of the manufactured electrodes is ensured. Therefore, electrodes with ensured quality can be efficiently manufactured.

[0009] In the above-described method for producing an electrode, the electrode active material contained in the first moist powder is a negative electrode active material, and the electrode active material contained in the second moist powder is a positive electrode active material, and when a direction perpendicular to a longitudinal direction of the current collecting foil and perpendicular to a thickness direction of the current collecting foil is defined as a width direction of the current collecting foil, a coating width of the first moist powder in the width direction is set wider than a coating width of the second moist powder in the width direction, Width direction In the above, the second electrode layer may be located within a range in which the first electrode layer is provided.

[0010] The electrodes manufactured by the above manufacturing method are elements that constitute the electricity storage device. To constitute the electricity storage device, a plurality of electrodes are stacked. The second electrode layer of one of the adjacent electrodes and the first electrode layer of the other of the adjacent electrodes are stacked via a separator. With the electrodes manufactured by the above manufacturing method, when the plurality of electrodes are stacked via the separator, the entire area of ​​the second electrode layer that constitutes the positive electrode always faces the first electrode layer that constitutes the negative electrode via the separator. Since the charge carriers generated in the second electrode layer can easily reach the first electrode layer via the separator, the performance of the electricity storage device can be ensured. Therefore, an electrode that can ensure the performance of the electricity storage device can be manufactured.

[0011] The above-described method for manufacturing an electrode may further include a drying step in which the first electrode layer formed on the current collector foil transported between the second drive roll and the third drive roll is dried by a drying device.

[0012] According to this, the solvent of the first wet powder constituting the first electrode layer can be removed by the drying device, and in the second step, the first electrode layer can be made less likely to stick to the third driving roll. The electrode manufacturing apparatus that solves the above problem is an electrode manufacturing apparatus that forms a first electrode layer by pressing a first wet powder containing an electrode active material, a binder, and a solvent against a first surface side of a strip-shaped current collecting foil, and forms a second electrode layer by pressing a second wet powder containing an electrode active material, a binder, and a solvent against a second surface side of the current collecting foil, the electrode manufacturing apparatus comprising a first drive roll, a second drive roll, a third drive roll, a fourth drive roll, a first power unit that rotates the second drive roll, a second power unit that rotates the third drive roll, and a control unit that controls the first power unit and the second power unit, and the current collecting foil is rotated by the rotation of the second drive roll with the current collecting foil in contact with the second drive roll. the current collecting foil passes between the first drive roll and the second drive roll, the first electrode layer is formed between the first drive roll and the second drive roll, and with the first electrode layer formed on the current collecting foil transported by the second drive roll in contact with the third drive roll, the current collecting foil and the first electrode layer pass between the third drive roll and the fourth drive roll due to rotation of the third drive roll, and the second electrode layer is formed between the third drive roll and the fourth drive roll, and the control unit makes the speed of the current collecting foil transported by the second drive roll faster than the rotation speed of the second drive roll by controlling the first power unit and the second power unit.

[0013] This allows the first and second electrode layers to be continuously formed on the continuously transported current collecting foil, and allows electrodes to be manufactured more efficiently than when the current collecting foil on which the first electrode layer has been formed is once wound up, transportation is stopped, and then the wound up current collecting foil is transported again to form the second electrode layer.

[0014] The control unit controls the first power unit and the second power unit to make the speed of the current collecting foil conveyed by the second drive roll faster than the rotation speed of the second drive roll. This allows the current collecting foil to slide on the second drive roll. In order to slide the current collecting foil on the second drive roll, the force with which the third drive roll pulls the current collecting foil needs to be greater than the static friction force acting on the second drive roll. The force with which the third drive roll pulls the current collecting foil is determined by the diameter of the third drive roll, the surface roughness of the third drive roll, the wrap angle of the current collecting foil with respect to the third drive roll, the rotation speed of the third drive roll, and the like. Similarly, the static friction force of the second drive roll is determined by the diameter of the second drive roll, the surface roughness of the second drive roll, the wrap angle of the current collecting foil with respect to the second drive roll, the rotation speed of the second drive roll, and the like. Information such as the diameter, surface roughness, and wrap angle of each of the second drive roll and the third drive roll is determined in advance when the electrode is manufactured. Therefore, the control unit controls the first power unit and the second power unit based on information determined in advance when the electrode is manufactured so that the force with which the third drive roll pulls the current collecting foil is greater than the static friction force acting on the second drive roll. In the electrode manufacturing device configured in this manner, the current collecting foil transported between the second drive roll and the third drive roll is pulled from the second drive roll toward the third drive roll by the rotation of the third drive roll. A kinetic friction force that tries to keep the current collecting foil on the second drive roll acts on the current collecting foil on the second drive roll. The current collecting foil transported between the second drive roll and the third drive roll is maintained in a pulled state. Since the current collecting foil transported between the second drive roll and the third drive roll is less likely to bend, when the second electrode layer is formed between the third drive roll and the fourth drive roll, the current collecting foil is less likely to wrinkle. This ensures the quality of the manufactured electrodes. This allows efficient manufacture of electrodes with ensured quality. Effect of the Invention

[0015] According to the present invention, electrodes with assured quality can be efficiently manufactured. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic diagram of an electrode manufacturing apparatus. [Diagram 2] FIG. 4 is a cross-sectional perspective view showing a state in which a first electrode layer is formed on a first surface of a current collecting foil. [Diagram 3] FIG. 4 is a cross-sectional perspective view showing the state in which the second electrode layer is formed on the second surface side of the current collecting foil. [Figure 4] Cross-sectional view taken along line 4-4 in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, one embodiment of an electrode manufacturing method and electrode manufacturing apparatus will be described with reference to Figs. 1 to 4. 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 current collecting foil 50 to form a first electrode layer 61, and presses a second moist powder P2 against a second surface S2 side of the current collecting foil 50 to form a second electrode layer 62. The current collecting 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 current collecting foil 50 that is continuously transported.

[0018] <Electrode configuration> As shown in FIG. 1, the electrode 70 includes a current collecting foil 50, a first electrode layer 61, a second electrode layer 62, and a bonding layer 63.

[0019] The current collecting foil 50 is formed by bonding a long strip of copper foil 51 and a long strip of aluminum foil 52 together. The current collecting foil 50 has a thickness of 1 mm or less. The width and length of the current collecting foil 50 are greater than the thickness. The first surface S1 of the current collecting foil 50 is the surface opposite to the surface bonded to the aluminum foil 52 among both surfaces of the copper foil 51 in the thickness direction. The second surface S2 of the current collecting foil 50 is the surface opposite to the surface bonded to the copper foil 51 among both surfaces of the aluminum foil 52 in the thickness direction. The current collecting foil 50 may be one surface of the aluminum foil 52 that has been copper-plated. The current collecting foil 50 may be formed as a single sheet of one type of metal material. The thicknesses of the current collecting foil 50, the first electrode layer 61, the second electrode layer 62, and the bonding layer 63 shown in FIG. 1 are exaggerated.

[0020] The binder layer 63 is provided on the second surface S2 of the current collector 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 current collector foil 50. The second electrode layer 62 is formed on the opposite side to the current collector foil 50 with respect to the binder layer 63. For this reason, it can be said that the second electrode layer 62 is formed on the second surface S2 side of the current collector foil 50. The binder layer 63 is mainly composed of a binder and a conductive assistant. The binder layer 63 only needs to be mainly composed of a binder and a conductive assistant, and may contain other materials.

[0021] The binder may be any type that has the function of binding the current collector foil 50 and the second electrode layer 62, and is not particularly limited. 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] <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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 current collector 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.

[0030] <Configuration of electrode manufacturing equipment> As shown in FIG. 1, the electrode manufacturing apparatus 1 includes a first driving roll 11, a second driving roll 12, a third driving roll 13, and a fourth driving roll 14. The first driving roll 11, the second driving roll 12, the third driving roll 13, and the fourth driving roll 14 are made of metal. The first driving roll 11, the second driving roll 12, the third driving roll 13, and the fourth driving roll 14 all have the same diameter. The axes of the first driving roll 11, the second driving roll 12, the third driving roll 13, and the fourth driving roll 14 extend in the same direction so as to be parallel to each other. The roll surface of the first driving roll 11 and the roll surface of the fourth driving roll 14 are coated with a fluororesin. The first driving roll 11, the second driving roll 12, the third driving roll 13, and the fourth driving roll 14 may be made of resin.

[0031] The second driving roll 12 is disposed at a position with a predetermined first distance from the first driving roll 11. The third driving roll 13 is disposed on the opposite side of the second driving roll 12 from the first driving roll 11. The third driving roll 13 is disposed at a position with a predetermined second distance from the second driving roll 12. The fourth driving roll 14 is disposed on the opposite side of the third driving roll 13 from the second driving roll 12. The fourth driving roll 14 is disposed at a position with a predetermined third distance from the third driving roll 13. The direction in which the axes of the four driving rolls 11, 12, 13, and 14 extend is defined as the axial direction. When the four driving rolls 11, 12, 13, and 14 are viewed from the outside in the axial direction, the four driving rolls 11, 12, 13, and 14 are disposed at the same height in the gravity direction A. Although not shown, when the four drive rolls 11, 12, 13, 14 are viewed from above in the direction of gravity A, first ends of the four drive 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 drive rolls 11, 12, 13, 14 are viewed from above in the direction of gravity A, second ends of the four drive 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 larger than the first distance and the third distance. The first distance is slightly smaller than the third distance.

[0032] 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 drive rolls 11, 12, 13, and 14 extend.

[0033] 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 driving 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 driving roll 12 than the third driving roll 13 in the horizontal direction B.

[0034] When the second guide roll 22 is viewed from the outside in the axial direction, the second guide roll 22 is disposed lower than the second driving 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 driving roll 12 than the first driving 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 lower than the third driving 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 driving roll 13 than the second driving 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 lower than the fourth driving 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 driving roll 14 than the third driving roll 13 in the horizontal direction B.

[0035] 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 driving roll 12 around its axis. The second power unit 32 rotates the third driving 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 codes or instructions configured to cause the processor to execute processes. The memory unit, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control unit 33 may be configured with a hardware circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). 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 an ASIC or an 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 V2 of the second driving roll 12 and the rotation speed V3 of the third driving roll 13.

[0036] The first driving roll 11 and the second driving roll 12 are connected by a first power transmission mechanism (not shown). When the second driving roll 12 rotates, the first driving roll 11 is rotated in a direction opposite to the direction of rotation of the second driving 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 V1 of the first driving roll 11 is slightly slower than the rotation speed V2 of the second driving roll 12. The third driving roll 13 and the fourth driving roll 14 are connected by a second power transmission mechanism (not shown). When the third driving roll 13 rotates, the second power transmission mechanism rotates the fourth driving roll 14 in a direction opposite to the direction of rotation of the third driving 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 V4 of the fourth drive roll 14 is slightly slower than the rotation speed V3 of the third drive roll 13.

[0037] The current collecting 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 current collecting foil 50 unwound from the supply roll passes through the electrode manufacturing apparatus 1 and is wound around the winding roll. Specifically, the current collecting foil 50 unwound downward from the supply roll is changed in orientation by the first guide roll 21 so as to face the second driving roll 12 and is transported in the horizontal direction B. The current collecting foil 50 whose orientation has been changed by the first guide roll 21 is wound around the second driving roll 12. After passing between the first driving roll 11 and the second driving roll 12, the current collecting 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 current collecting 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 current collecting foil 50, whose orientation has been changed by the third guide roll 23, is wound around the third drive roll 13. After passing between the third drive roll 13 and the fourth drive roll 14, the current collecting foil 50 has its orientation changed by the fourth guide roll 24 so as to face the winding roll, and is transported in the horizontal direction B. The current collecting foil 50 is then taken up on the winding roll. Note that if the direction in which the current collecting foil 50 is transported is defined as a transport direction D, the power that transports the current collecting foil 50 in the transport direction D is the torque of the second drive roll 12 and the torque of the third drive roll 13. Furthermore, the transport direction D coincides with the longitudinal direction of the long strip-shaped current collecting foil 50.

[0038] 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 driving roll 11 and the second driving roll 12. The lower part of the first wet powder supplying device 41 is inserted between the first driving roll 11 and the second driving roll 12. The first wet powder supplying device 41 is disposed closer to the first driving roll 11 than the second driving roll 12. The supply port 41a of the first wet powder supplying device 41 is provided between the first driving roll 11 and the second driving roll 12, closer to the first driving roll 11 than the second driving roll 12.

[0039] 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 driving roll 13 and the fourth driving roll 14. The lower part of the second wet powder supplying device 42 is inserted between the third driving roll 13 and the fourth driving roll 14. The second wet powder supplying device 42 is disposed closer to the fourth driving roll 14 than the third driving roll 13. The supply port 42a of the second wet powder supplying device 42 is provided between the third driving roll 13 and the fourth driving roll 14, closer to the fourth driving roll 14 than the third driving roll 13.

[0040] 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 driving roll 12.

[0041] In the above-described electrode manufacturing apparatus 1, a manufacturing method of the electrode 70 will be described below, including the flow of the current collecting foil 50 from upstream to downstream in the transport direction D and the order of forming the first electrode layer 61 and the second electrode layer 62. Note that it is assumed that a bonding layer 63 is formed in advance on the second surface S2 of the current collecting foil 50 over the entire length of the current collecting foil 50 in the longitudinal direction.

[0042] <Electrode manufacturing method> The manufacturing method of the electrode 70 includes a first step Pr1, a second step Pr2, and a drying step Prd. The first step Pr1 is a step of forming a first electrode layer 61 on a first surface S1 between a first driving roll 11 and a second driving roll 12. In the first step Pr1, the current collecting foil 50 is in contact with the second driving roll 12 via a binder layer 63, and the current collecting foil 50 passes between the first driving roll 11 and the second driving roll 12 due to the rotation of the second driving roll 12.

[0043] The first step Pr1 will be described in detail with reference to Fig. 1. The first surface S1 of the current collector foil 50 passing through the electrode manufacturing apparatus 1 contacts the first guide roll 21. The embrace angle α of the binder layer 63 with respect to the upper part of the second drive roll 12 is a preset value. The current collector foil 50 and the binder layer 63 pass between the first drive roll 11 and the second drive roll 12 due to the rotation of the second drive roll 12. The first surface S1 of the current collector foil 50 and the first drive roll 11 are not in contact with each other.

[0044] With the current collector foil 50 passing between the first driving roll 11 and the second driving 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 toward the first surface S1 of the current collector foil 50 by the rotation of the first driving roll 11. The first wet powder P1 is pressed in the thickness direction of the current collector foil 50 by the first driving roll 11 and the second driving roll 12. The first wet powder P1 is pressed against the first surface S1 of the current collector foil 50, thereby forming a first electrode layer 61 on the first surface S1 of the current collector 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 current collector foil 50 has a predetermined thickness. Note that the solvent contained in the first wet powder P1 is not removed from the first electrode layer 61 immediately after passing between the first driving roll 11 and the second driving roll 12. The first electrode layer 61 immediately after passing between the first driving roll 11 and the second driving roll 12 is a precursor of the negative electrode active material layer.

[0045] 2, a direction perpendicular to the longitudinal direction of current collecting foil 50 and perpendicular to the thickness direction of current collecting foil 50 is defined as width direction C of current collecting foil 50. Width direction C is perpendicular to conveyance direction D. In first step Pr1, coating width W2 of first wet powder P1 in width direction C is set narrower than width W1 of current collecting foil 50 in width direction C. First wet powder P1 is pressed so as to form uncoated portions on both sides of current collecting foil 50 in width direction C where first wet powder P1 is not pressed.

[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 driving roll 12 and the third driving roll 13.

[0047] 1, the current collector 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 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 second electrode layer 62 on the second surface S2 side of the current collector foil 50 between the third drive roll 13 and the fourth drive roll 14. In the second step Pr2, with the first electrode layer 61 in contact with the third drive roll 13, the current collector foil 50 and the first electrode layer 61 pass between the third drive roll 13 and the fourth drive roll 14 due to the rotation of the third drive roll 13.

[0049] More specifically, the binder layer 63 formed on the current collecting foil 50 that has passed through the drying device 80 is in contact with the third guide roll 23. The embrace angle β of the first electrode layer 61 after drying relative to the upper part of the third driving roll 13 is a preset value. The embrace angle β is larger than the embrace angle α. As the third driving roll 13 rotates, the current collecting foil 50 on which the first electrode layer 61 has been formed passes between the third driving roll 13 and the fourth driving roll 14. The binder layer 63 formed on the current collecting foil 50 is not in contact with the fourth driving roll 14.

[0050] With the first electrode layer 61 and the current collecting foil 50 passing between the third driving roll 13 and the fourth driving 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 driving roll 14. The second wet powder P2 is pressed in the thickness direction of the current collecting foil 50 by the third driving roll 13 and the fourth driving 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 current collecting foil 50. Here, the above-mentioned third distance is set so that the second electrode layer 62 formed on the second surface S2 of the current collecting foil 50 has a predetermined thickness. Note that the second electrode layer 62 immediately after passing between the third driving roll 13 and the fourth driving roll 14 has no solvent removed from the second wet powder P2. The second electrode layer 62 immediately after passing between the third drive roll 13 and the fourth drive roll 14 is a precursor of the positive electrode active material layer.

[0051] 3, in the second step Pr2, a coating width W3 in the width direction C of the second wet powder P2 is set narrower than a width W1 in the width direction C of the current collecting foil 50. The second wet powder P2 is pressed in the width direction C so as to form uncoated portions on both sides of the current collecting foil 50 in the width direction C where the second wet powder P2 is not pressed.

[0052] 2, 3, and 4, the application width W2 of the first wet powder P1 in the first step Pr1 is set to be wider than the application width W3 of the second wet powder P2 in the second step Pr2. In the thickness direction of the current collecting foil 50, the second electrode layer 62 is located within the range in which the first electrode layer 61 is provided. Note that, as shown in Fig. 4, the width of the binder layer 63 in the width direction C is the same as the application width W2 of the second wet powder P2.

[0053] As shown in FIG. 1, the current collector 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 current collector 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 current collector foil 50 in the transport direction D. The manufacturing method of the electrode 70 is a manufacturing method in which the first electrode layer 61 and the second electrode layer 62 are formed on the strip-shaped current collector foil 50 using four driving rolls 11, 12, 13, and 14, and has a first process Pr1, a second process Pr2, and a drying process Prd.

[0054] In the manufacturing method of electrode 70, when the first electrode layer 61 and the second electrode layer 62 are being formed, the speed Vc of the current collector foil 50 transported by the second drive roll 12 is faster than the rotation speed V2 of the second drive roll 12. This point will be described below.

[0055] <Control of the first power unit and the second power unit by the control device> The control unit 33 controls the first power unit 31 and the second power unit 32 so as to ensure the quality of the electrode 70 as follows.

[0056] As shown in FIG. 1, the control unit 33 controls the first power unit 31 and the second power unit 32 so that the speed Vc of the current collecting foil 50 conveyed by the second driving roll 12 is faster than the rotation speed V2 of the second driving roll 12. That is, the control unit 33 controls the first power unit 31 and the second power unit 32 so that the current collecting foil 50 on the second driving roll 12 slides on the second driving roll 12. In order to slide the current collecting foil 50 on the second driving roll 12, the force with which the third driving roll 13 pulls the current collecting foil 50 needs to be greater than the static friction force acting on the second driving roll 12. The force with which the third driving roll 13 pulls the current collecting foil 50 is determined by the diameter of the third driving roll 13, the surface roughness of the third driving roll 13, the embrace angle β of the current collecting foil 50 with respect to the third driving roll 13, the rotation speed V3 of the third driving roll 13, and the like. Similarly, the static friction force acting on the second drive roll 12 is determined by the diameter of the second drive roll 12, the surface roughness of the second drive roll 12, the embrace angle α of the current collector foil 50 with respect to the second drive roll 12, and the rotation speed V2 of the second drive roll 12, etc. Information on the diameter, surface roughness, and embrace angles α and β of the second drive roll 12 and the third drive roll 13, respectively, is determined in advance when the electrode 70 is manufactured.

[0057] The memory of the control unit 33 stores program codes or commands for controlling the first power unit 31 and the second power unit 32 based on information determined in advance when the electrode 70 is manufactured so that the force with which the third drive roll 13 pulls the current collector foil 50 becomes greater than the static friction force acting on the second drive roll 12. Thus, the control unit 33 controls the first power unit 31 and the second power unit 32 to control the speeds V2 and V3 so that the force with which the third drive roll 13 pulls the current collector foil 50 becomes greater than the static friction force acting on the second drive roll 12.

[0058] <Action of this embodiment> The operation of this embodiment will now be described. After the first electrode layer 61 is formed on the current collecting foil 50, the current collecting foil 50 slides against the second driving roll 12 while the second electrode layer 62 is continuously formed. The current collecting foil 50 transported between the second driving roll 12 and the third driving roll 13 is pulled from the second driving roll 12 toward the third driving roll 13 by the rotation of the third driving roll 13. A kinetic frictional force acts on the current collecting foil 50 on the second driving roll 12, tending to keep the current collecting foil 50 on the second driving roll 12. The current collecting foil 50 transported between the second driving roll 12 and the third driving roll 13 is maintained in a pulled state.

[0059] <Effects of this embodiment> The effects of this embodiment will be described. (1) Because the first step Pr1 and the second step Pr2 can be performed on the current collecting foil 50 that is continuously transported, the first electrode layer 61 and the second electrode layer 62 can be continuously formed on the current collecting foil 50. The electrode 70 can be manufactured more efficiently than in a case where the current collecting foil 50 after the first step Pr1 is once wound up and transportation is stopped, and then the wound up current collecting foil 50 is transported again to perform the second step Pr2.

[0060] Since the current collector foil 50 transported between the second drive roll 12 and the third drive roll 13 is less likely to bend, the current collector foil 50 is less likely to wrinkle when the second electrode layer 62 is formed between the third drive roll 13 and the fourth drive roll 14. This ensures the quality of the manufactured electrode 70. Therefore, the electrode 70 with ensured quality can be manufactured efficiently.

[0061] (2) The electrode 70 manufactured in this embodiment is an element constituting the electricity storage device. To constitute the electricity storage device, a plurality of electrodes 70 are stacked. The second electrode layer 62 in one of the adjacent electrodes 70 and the first electrode layer 61 in the other of the adjacent electrodes 70 are stacked via a separator. With the electrode 70 manufactured in this embodiment, when the plurality of electrodes 70 are stacked via a separator, the entire area of ​​the second electrode layer 62 constituting the positive electrode always faces the first electrode layer 61 constituting the negative electrode via the separator. Since the charge carriers generated in the second electrode layer 62 can easily reach the first electrode layer 61 via the separator, the performance of the electricity storage device can be ensured. Therefore, the electrode 70 capable of ensuring the performance of the electricity storage device can be manufactured.

[0062] (3) 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 driving roll 13 in the second process Pr2. (4) 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 current collector 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 current collector foil 50 via the binder layer 63.

[0063] (5) The roll surface of the first drive roll 11 and the roll surface of the fourth drive roll 14 are coated with a fluororesin. Therefore, when the first wet powder P1 is pressed against the first surface S1 of the current collector foil 50 by the first drive roll 11, the first wet powder P1 can be easily released from the first drive roll 11. In addition, when the second wet powder P2 is pressed against the binder layer 63 by the fourth drive roll 14, the second wet powder P2 can be easily released from the fourth drive roll 14.

[0064] <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.

[0065] 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 driving roll 13 and the fourth driving roll 14 in the transport direction D. In this case, the first electrode layer 61 and the second electrode layer 62 may be dried simultaneously by the drying device 80.

[0066] 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.

[0067] A binder layer 63 may also be provided on the first surface S1 of the current collecting foil 50. In this case, the first electrode layer 61 is formed on the binder layer 63 formed on the first surface S1 of the current collecting foil 50. In other words, the first electrode layer 61 is formed on the first surface S1 side of the current collecting foil 50.

[0068] The binder layer 63 formed on the second surface S2 of the current collecting foil 50 may be omitted, and the second electrode layer 62 may be formed on the second surface S2 of the current collecting foil 50. When making such a modification, it is preferable to change the binder and solvent contained in the second moist powder P2 to ones that are not aqueous, so that the second electrode layer 62 forming the positive electrode can be more easily bound to the second surface S2 of the current collecting foil 50.

[0069] 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 current collector 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 current collector 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 width of the binder layer 63 in the width direction C is set to be the same as the coating width W2.

[0070] The first drive roll 11, the second drive roll 12, the third drive roll 13, and the fourth drive roll 14 may have different diameters. The arrangement of the first driving roll 11, the second driving roll 12, the third driving roll 13, and the fourth driving roll 14 in the gravity direction A and the horizontal direction B may be changed as appropriate.

[0071] A surface treatment other than the fluororesin coating may be performed on the roll surface of the first drive roll 11 and the roll surface of the fourth drive roll 14. Any surface treatment other than the fluororesin coating may be performed as long as it can facilitate the release of the first wet powder P1 from the first drive roll 11 and the release of the second wet powder P2 from the fourth drive roll 14. The fluororesin coating on the roll surface of the first drive roll 11 and the roll surface of the fourth drive roll 14 may be omitted, and no surface treatment may be performed.

[0072] In the electrode manufacturing apparatus 1, the second guide roll 22 and the third guide roll 23 may be omitted. In this case, the current collecting foil 50 transported by the second drive roll 12 is directly transported to the third drive roll 13. In the electrode manufacturing apparatus 1, the first guide roll 21 and the fourth guide roll 24 may also be omitted.

[0073] In this embodiment, the embrace angle β may be smaller than the embrace angle α, or the embrace angles β and α may be the same size. The first driving roll 11 and the fourth driving roll 14 may be changed to rolls that rotate independently. In this case, a power unit that rotates each of the first driving roll 11 and the fourth driving roll 14 may be provided, and the power unit may be controlled by the control unit 33.

[0074] The control unit 33 may be configured to include a first control device that controls the first power unit 31 and a second control device that controls the second power unit 32 . [Explanation of symbols]

[0075] Reference Signs List 1...electrode manufacturing apparatus, 11...first driving roll, 12...second driving roll, 13...third driving roll, 14...fourth driving 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...current collecting foil, 51...copper foil, 52...aluminum foil, 61...first electrode layer, 62...second electrode layer, 63...bonding 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, Prd...drying process, V1...rotation speed of first drive roll, V2...rotation speed of second drive roll, V3...rotation speed of third drive roll, V4...rotation speed of fourth drive roll, Vc...speed of current collector transported to second drive roll.

Claims

1. A method for manufacturing an electrode, comprising: pressing a first wet powder containing an electrode active material, a binder, and a solvent onto a first surface side of a long strip-shaped current collector foil using a first drive roll, a second drive roll, a third drive roll, and a fourth drive roll to form a first electrode layer; and pressing a second wet powder containing an electrode active material, a binder, and a solvent onto a second surface side of the current collector foil to form a second electrode layer, a first step in which the current collecting foil passes between the first driving roll and the second driving roll by rotation of the second driving roll in a state in which the current collecting foil is in contact with the second driving roll, and the first electrode layer is formed on the first surface side between the first driving roll and the second driving roll; a second step of passing the current collecting foil and the first electrode layer between the third drive roll and the fourth drive roll by rotation of the third drive roll in a state in which the first electrode layer formed on the current collecting foil transported by the second drive roll after the first step is in contact with the third drive roll, and forming the second electrode layer on the second surface side between the third drive roll and the fourth drive roll, 4. The method for manufacturing an electrode, wherein the speed of the current collector foil transported by the second drive roll is faster than the rotation speed of the second drive roll.

2. the electrode active material contained in the first wet powder is a negative electrode active material, the electrode active material contained in the second wet powder is a positive electrode active material, If a direction perpendicular to the longitudinal direction of the current collecting foil and perpendicular to the thickness direction of the current collecting foil is defined as a width direction of the current collecting foil, A coating width of the first wet powder in the width direction is set wider than a coating width of the second wet powder in the width direction, The method for manufacturing an electrode according to claim 1 , wherein the second electrode layer is located within a range in the width direction where the first electrode layer is provided.

3. 3. The method for manufacturing an electrode according to claim 1, further comprising a drying step of drying the first electrode layer formed on the current collector foil transported between the second drive roll and the third drive roll by a drying device.

4. An electrode manufacturing apparatus for forming a first electrode layer by pressing a first moist powder containing an electrode active material, a binder, and a solvent against a first surface side of a long strip-shaped current collector foil, and for forming a second electrode layer by pressing a second moist powder containing an electrode active material, a binder, and a solvent against a second surface side of the current collector foil, comprising: A first driving roll; A second drive roll; A third drive roll; A fourth drive roll; A first power unit that rotates the second driving roll; A second power unit that rotates the third driving roll; a control unit that controls the first power unit and the second power unit, With the current collecting foil in contact with the second driving roll, the current collecting foil passes between the first driving roll and the second driving roll by rotation of the second driving roll, the first electrode layer is formed between the first drive roll and the second drive roll; the first electrode layer formed on the current collecting foil transported by the second drive roll is in contact with the third drive roll, and the current collecting foil and the first electrode layer pass between the third drive roll and the fourth drive roll by rotation of the third drive roll; the second electrode layer is formed between the third drive roll and the fourth drive roll; The control unit controls the first power unit and the second power unit to make the speed of the current collecting foil transported by the second drive roll faster than the rotation speed of the second drive roll.

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