Battery manufacturing method

Abstract

The present disclosure provides a method for manufacturing a battery that can suppress cracking of a heat-treated electrode active material layer. [Solution] A method for manufacturing a battery disclosed herein includes conveying a laminate, heated to a temperature of 120° C. or higher, through a roller such that the conveying direction of a substrate layer and an electrode active material layer is changed by 45° or more along a direction-changing roller. In the method disclosed herein, the direction-changing roller also expands the width of the laminate.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a battery. [Background technology]

[0002] As disclosed in Patent Documents 1 to 5, techniques have been developed for drying electrode active material layers that constitute electrode laminates for batteries. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2017-183214 [Patent Document 2] Patent Publication No. 2017-228349 [Patent Document 3] Patent Publication No. 2008-147114 [Patent Document 4] Patent Publication No. 2016-103402 [Patent Document 5] Patent Publication No. 2017-191678 Summary of the Invention [Problem to be solved by the invention]

[0004] In manufacturing a battery, it is desirable to prevent cracks in the electrode active material layer that has been heat-treated for drying or the like.

[0005] An object of the present disclosure is to provide a method for manufacturing a battery that can suppress cracking of a heat-treated electrode active material layer. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> conveying the laminate, which has been heated to a temperature of 120°C or higher and includes a base material layer and an electrode active material layer, by a roller such that the conveying direction of the laminate is changed by 45° or more along a direction-changing roller; and The direction-changing roller is configured to widen the laminate. How batteries are manufactured. <Aspect 2> 2. The method of claim 1, wherein the deflecting roller has a center portion and opposite ends, and the peripheral speed at the opposite ends is faster than the peripheral speed at the center portion. <Aspect 3> The direction-changing roller is composed of two rollers at both ends, a conveying roller is further provided upstream of the direction-changing roller in the conveying direction; and The peripheral speed of the direction-changing roller is faster than the peripheral speed of the conveying roller. 2. The method of embodiment 1. <Aspect 4> Further comprising drying the electrode active material layer before the roller conveyance; and In the drying step, the laminate is heated to a temperature of 120°C or higher. The method according to any one of aspects 1 to 3. <Aspect 5> 5. The method of claim 4, wherein the drying step involves laser heating the laminate. [Effects of the Invention]

[0007] According to the disclosed method for manufacturing a battery, cracking of the heat-treated electrode active material layer can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the disclosed method for manufacturing a battery. [Figure 2] FIG. 2 is a schematic diagram showing an example of a direction-changing roller. [Figure 3] FIG. 3 is a schematic diagram showing an example of a direction-changing roller. [Figure 4]FIG. 4 is a schematic diagram showing an example of a direction-changing roller. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0010] <Battery manufacturing method> The disclosed method for manufacturing a battery includes conveying a laminate having a base material layer and an electrode active material layer heated to a temperature of 120° C. or higher by a roller, while changing the conveying direction of the laminate by 45° or more along a direction-changing roller. In the disclosed method, the direction-changing roller also expands the width of the laminate.

[0011] The present inventors have considered that one of the reasons why an electrode active material layer heated to a predetermined temperature of 120°C or higher is prone to cracking is that the moisture content in the electrode active material layer is reduced, thereby reducing the flexibility of the electrode active material layer.

[0012] In this regard, the present inventors have discovered that, in manufacturing a battery, cracking of the heat-treated electrode active material layer can be suppressed by conveying a laminate having a base layer and an electrode active material layer heated to a temperature of 120°C or higher while changing the conveying direction of the laminate by 45° or more along a direction-changing roller that widens the laminate. The reason for this is presumed to be as follows, without intending to be bound by any theory. Specifically, for example, when a laminate at room temperature is changed in direction by 45° or more along a direction-changing roller, the electrode active material layers of the laminate are broken apart, resulting in cracks in the electrode active material layer. In contrast, the flexibility of the binder in the electrode active material layer of a laminate heated to a temperature of 120°C or higher is thought to be improved. In this state, by turning the direction of the laminate including the electrode active material layer by 45° or more along the direction-changing roller, it is believed that an appropriate amount of stress is applied to the electrode active material layer containing the highly flexible binder, which allows the binder to stretch and expand while still binding the electrode active material together. Furthermore, since the direction-changing roller is configured to expand the width of the laminate, stress is applied to the electrode active material layer from multiple directions, which is believed to further reduce the likelihood of the electrode active material being separated. As a result, it is believed that cracking of the electrode active material layer is suppressed.

[0013] In the present disclosure, the width direction associated with the term "widening" means the direction perpendicular to the conveying direction within the plane of the laminate.

[0014] The method of manufacturing an electrode according to the present disclosure will be described below with reference to the drawings, in which the dimensional relationships do not reflect the actual dimensional relationships.

[0015] 1 is a schematic diagram illustrating an example of an electrode active material layer being wound from a winding reel 41 onto a winding reel 42 after being heated and conveyed by rollers. Also, FIGS. 2 to 4 are schematic diagrams showing examples of direction-changing rollers used in the method of the present disclosure.

[0016] <Roller conveying process> 1 , the method of the present disclosure includes conveying the laminate 1, which has been heated to a temperature of 120° C. or higher and includes a base material layer and an electrode active material layer, by changing the conveying direction of the laminate 1 by 45° or more along a direction-changing roller 20. When the angle at which the conveying direction of the laminate is changed is within the above range, cracking of the electrode active material layer can be effectively suppressed.

[0017] The heating temperature may be 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, 190°C or higher, or 200°C or higher, and may be 300°C or lower, 290°C or lower, 280°C or lower, 270°C or lower, 260°C or lower, or 250°C or lower. It is believed that a heating temperature within the above range is likely to result in a decrease in moisture content in the electrode active material layer, a decrease in flexibility due to binder degradation, and the like. Based on this assumption, applying the method of the present disclosure to an electrode active material layer that has undergone heat treatment at a temperature within the above range is particularly effective.

[0018] The angle at which the conveying direction of the laminate is changed may be 60° or more, 70° or more, 80° or more, 85° or more, or 90° or more, and may be 180° or less, 150° or less, 130° or less, 120° or less, 110° or less, 100° or less, 95° or less, or 90° or less.

[0019] In the method of the present disclosure, the direction-changing roller 20 is configured to widen the laminate 1. With this configuration, stress can be applied to the electrode active material layer from multiple directions, and therefore cracking of the electrode active material layer can be effectively suppressed.

[0020] In the method of the present disclosure, the direction-changing roller 20 has a center portion 21 and both end portions 22, and the peripheral speed of the both end portions 22 may be faster than the peripheral speed of the center portion 21. An example of such a direction-changing roller is one composed of three rollers, as exemplified in FIG. 2, in which the peripheral speed of the both end rollers (both end portions) is faster than the peripheral speed of the center roller (center portion). Another example is a roller having a so-called inverted crown shape, as exemplified in FIG. 3. Furthermore, although not shown, an example of a direction-changing roller is one composed of three rollers, in which the diameter of the both end rollers (both end portions) is larger than the diameter of the center roller (center portion), and consequently the peripheral speed of the both end portions is faster than the peripheral speed of the center portion.

[0021] In the method of the present disclosure, the direction-changing roller 20 may be composed of two rollers at both ends, and a transport roller 30 may be further provided upstream or downstream of the direction-changing roller 20 in the transport direction, and the peripheral speed of the direction-changing roller 20 may be faster than the peripheral speed of the transport roller 30. In particular, as illustrated in FIG. 4, the transport roller 30 may be provided upstream of the direction-changing roller 20 in the transport direction.

[0022] By configuring the direction-changing roller as described above, the laminate can be easily expanded in width, and therefore cracks in the electrode active material layer can be effectively suppressed.

[0023] The direction-changing rollers adapted to widen the laminate are not limited to the above-described embodiment, and other examples include expander rollers.

[0024] The peripheral speed of the direction-changing roller is not particularly limited. That is, for example, in the case of a direction-changing roller 20 as illustrated in FIG. 2, it is sufficient that the peripheral speed of both end portions 22 is faster than the peripheral speed of the center portion 21. Furthermore, for example, in the case of a direction-changing roller 20 as illustrated in FIG. 4, it is sufficient that the peripheral speed of the direction-changing roller 20 is faster than the peripheral speed of the conveying roller 30. Note that the arrow in FIG. 4 indicates the conveying direction of the laminate 1. The peripheral speed of the direction-changing roller can be set appropriately taking into consideration, for example, the viewpoint of suppressing cracking of the electrode active material layer and the viewpoint of ease of conveyance.

[0025] The diameter of the direction-changing roller is not particularly limited, but may be 35 mm or more, 40 mm or more, 45 mm or more, 50 mm or more, or 55 mm or more, and may be 300 mm or less, 250 mm or less, 200 mm or less, 150 mm or less, 130 mm or less, 120 mm or less, 110 mm or less, or 100 mm or less. When the diameter of the direction-changing roller is within the above range, cracking of the electrode active material layer can be effectively suppressed. Note that, in the case of a so-called inverted crown-shaped direction-changing roller, the diameter of the direction-changing roller may refer to the diameter of the largest diameter portion at both ends of the roller.

[0026] In the method of the present disclosure, the temperature of the laminate during the change of direction is not particularly limited, but may be 40°C or higher. When this temperature is within the above range, cracking of the electrode active material layer can be effectively suppressed. This temperature may be 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, or 100°C or higher, and may be 150°C or lower, 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. This temperature can be appropriately set taking into consideration the softening temperature of the binder, etc. Note that this temperature may particularly refer to the temperature of the electrode active material layer of the laminate.

[0027] The temperature of the stack may be monitored by a thermometer, such as a temperature sensor, which may in particular be a non-contact radiation thermometer.

[0028] The transport speed of the electrode active material layer is not particularly limited, and can be set appropriately taking into consideration the viewpoints of suppressing cracking of the electrode active material layer, ease of transport, and the like.

[0029] In the method of the present disclosure, direction-changing rollers may be used in multiple stages in the conveying direction of the electrode active material layer. The number of stages of direction-changing rollers is not particularly limited and can be set appropriately from the viewpoints of suppressing cracks in the electrode active material layer and saving space.

[0030] The substrate layer in the method of the present disclosure is not particularly limited, but examples thereof include a current collector and a release sheet. For example, when the substrate layer is a current collector, the laminate subjected to the method of the present disclosure can be used as is for manufacturing a battery. Furthermore, when the substrate layer is a release sheet, the electrode active material layer of the laminate subjected to the method of the present disclosure can be peeled from the substrate layer, which is the release sheet, and transferred to a current collector, which can be used for manufacturing a battery.

[0031] <Drying process> The method of the present disclosure may further include drying the electrode active material layer before conveying with rollers, and in the drying step, the laminate 1 may be heated to a temperature of 120° C. or higher.

[0032] In the drying step, for example, the laminate 1 may be heated by laser or infrared. From the viewpoint of efficiently heating the laminate 1, the laminate 1 may be heated by laser, particularly in the drying step. In addition, air blowing may be used in combination in the drying step. The air blowing may be hot air.

[0033] Drying may be performed by a predetermined heating unit 10. Heating and roller conveying may be performed continuously or discontinuously. For example, in FIG. 1, the laminate is conveyed by rollers even during heating, and thus heating and roller conveying are performed continuously. In contrast, the laminate does not need to be conveyed by rollers during heating, and thus heating and roller conveying may be performed discontinuously.

[0034] <Pressing process> Although not shown, the method of the present disclosure may further include pressing the laminate 1 before the roller conveyance. In particular, the pressing step may be performed before the drying step described above.

[0035] It is believed that the binder in the electrode active material layer that has undergone the pressing process is compressed, and therefore the flexibility of the electrode active material layer is reduced. Based on this assumption, it is particularly effective to apply the method of the present disclosure to the electrode active material layer that has undergone the pressing process.

[0036] The pressing method is not particularly limited, and a conventional method can be used.

[0037] The pressure of the press is not particularly limited, and can be appropriately set so that the density of the electrode active material layer has a desired value.

[0038] <Low temperature drying process> The method of the present disclosure may further include drying the electrode active material layer at a temperature lower than that in the drying step described above, prior to the pressing step. The drying temperature in this step may be 80° C. or higher, 90° C. or higher, or 100° C. or higher, and may be 140° C. or lower, 130° C. or lower, or 120° C. or lower.

[0039] "battery" The battery of the present disclosure is manufactured by the method of manufacturing a battery of the present disclosure. In the battery of the present disclosure, cracking of the heat-treated electrode active material layer is suppressed.

[0040] The batteries of the present disclosure include an electrode stack and, optionally, an electrolyte layer.

[0041] In the context of the present disclosure, the term "electrode laminate" refers to a component that is a laminate of an electrode active material layer and a current collector and that can pass an electric current. That is, when the substrate layer in the method of the present disclosure is a current collector, the term "laminate" refers to an electrode laminate.

[0042] The bipolar battery of the present disclosure may be a liquid-based battery or a solid-state battery. In the context of the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as an electrolyte. Therefore, a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as an electrolyte. Alternatively, the solid-state battery of the present disclosure may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as an electrolyte.

[0043] The battery of the present disclosure may be a primary battery or a secondary battery, particularly a lithium ion secondary battery.

[0044] The battery of the present disclosure may be a monopolar battery or a bipolar battery.

[0045] When the battery of the present disclosure is a monopolar battery, the "electrode laminate" may be a negative electrode laminate or a positive electrode laminate. For example, when the electrode laminate refers to a negative electrode laminate, the negative electrode laminate is a laminate of a negative electrode active material layer and a negative electrode current collector. When the electrode laminate refers to a positive electrode laminate, the positive electrode laminate is a laminate of a positive electrode active material layer and a positive electrode current collector. From the viewpoint of more effectively suppressing cracking of the electrode active material layer, the electrode laminate may particularly be a negative electrode laminate.

[0046] When the battery of the present disclosure is a bipolar battery, the "electrode laminate" may be a bipolar electrode laminate. The bipolar electrode laminate may have a negative electrode active material layer, a current collector, and a positive electrode active material layer, in this order. When the electrode laminate is a bipolar electrode laminate and laser heating is performed in the drying step, the positive electrode active material layer may be heated by irradiating it with a laser. Furthermore, in this case, the negative electrode active material layer may be arranged radially outward of the direction-changing roller. That is, the negative electrode active material layer, which has been heated by preheating from the laser-heated positive electrode active material layer, may be stretched by the direction-changing roller.

[0047] <Current collector> The current collector may be any known current collector for batteries, such as copper foil, copper alloy foil, nickel foil, aluminum foil, aluminum alloy foil, stainless steel foil, or carbon sheet.

[0048] When the battery of the present disclosure is a bipolar battery, the current collectors may include two different types of current collectors. In this case, the current collectors may be bonded to each other via a conductive adhesive layer or may be joined by pressing or the like. For example, the current collector on the negative electrode active material layer side may be copper foil, and the current collector on the positive electrode active material layer side may be aluminum foil.

[0049] The thickness of the current collector is not particularly limited, but may be 1 μm to 300 μm, 5 μm to 200 μm, or 10 μm to 100 μm. When the current collector has two types of current collectors bonded to each other via a conductive adhesive layer, the total thickness of the layers may be in the above range.

[0050] The size of the current collector is not particularly limited, and can be set appropriately taking into consideration, for example, the desired capacity of the battery.

[0051] The shape of the current collector is not particularly limited, but may be, for example, a quadrilateral such as a rectangle.

[0052] <Electrode active material layer> The electrode active material layer includes an electrode active material and a binder, and may optionally include a conductive additive and other components. In the present disclosure, the "electrode active material layer" may be a "negative electrode active material layer" or a "positive electrode active material layer."

[0053] The electrode active material layer can be formed from an electrode mixture slurry.

[0054] In the present disclosure, the term "composite" refers to a composition that can constitute an electrode active material layer, etc., either as it is or by further containing other components. In the present disclosure, the term "composite slurry" refers to a slurry that contains a dispersion medium in addition to the "composite" and that can be applied and dried to form an electrode active material layer, etc.

[0055] The thickness of the electrode active material layer is not particularly limited and may be 10 μm or more and 500 μm or less, 100 μm or more and 450 μm or less, or 200 μm or more and 400 μm or less.

[0056] The size of the electrode active material layer is not particularly limited, and can be set appropriately taking into consideration, for example, the desired capacity of the battery.

[0057] The shape of the electrode active material layer is not particularly limited, but may be, for example, a quadrangle such as a rectangle.

[0058] (electrode active material) The electrode active material is not particularly limited. In the present disclosure, the "electrode active material" can be used as both a "negative electrode active material" and a "positive electrode active material."

[0059] The negative electrode active material is not particularly limited as long as it has a lower potential than the positive electrode active material. When the electrode laminate of the present disclosure is an electrode laminate for a lithium ion secondary battery, examples of the negative electrode active material include carbonaceous materials such as graphite (artificial graphite, natural graphite), resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; metal-based materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; and Li4Ti5O 12 and lithium alloys such as Li-Si alloys, Li-Sn alloys, Li-Al alloys, Li-Ga alloys, Li-Mg alloys, and Li-In alloys. These negative electrode active materials may be used singly or in combination of two or more.

[0060] The content of the negative electrode active material in the negative electrode mixture as the electrode mixture is not particularly limited, but may be 50 mass % or more, 70 mass % or more, 90 mass % or more, or 95 mass % or more.

[0061] The negative electrode active material may be in the form of particles, for example.

[0062] The positive electrode active material is not particularly limited as long as it has a more noble potential than the negative electrode active material. When the electrode laminate of the present disclosure is an electrode laminate for a lithium ion secondary battery, examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), solid solution oxide (LiMnO-LiMO (M=Co, Ni, etc.)), lithium nickel manganese oxide (LiNi 1 / 2 Mn 1 / 2O2), lithium nickel cobalt manganese oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples of the cathode active materials that can be used include composite oxides such as lithium phosphate oxide (LiFePO4), olivine-type lithium phosphate oxide (LiFePO4), and conductive polymers such as polyaniline and polypyrrole; sulfide-based cathode active materials such as LiS, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, and Li-VS compounds; and sulfur-based active materials such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon. These cathode active materials may be used alone or in combination of two or more.

[0063] The content of the positive electrode active material in the positive electrode mixture as the electrode mixture is not particularly limited, but may be 50 mass % or more, 70 mass % or more, 90 mass % or more, or 95 mass % or more.

[0064] The positive electrode active material may be in the form of particles, for example.

[0065] (binder) In the present disclosure, the binder can be stretched and spread in a flexible state, thereby suppressing cracking of the electrode active material layer.

[0066] The binder is not particularly limited, but when the battery of the present disclosure is a lithium ion secondary battery, examples of the binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, etc. These binders may be used alone or in combination of two or more.

[0067] The content of the binder in the electrode mixture is not particularly limited, and can be set appropriately depending on the desired binding properties, etc.

[0068] (Conductive additive) The conductive additive is not particularly limited, but when the bipolar battery of the present disclosure is a lithium ion secondary battery, examples include graphites such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; carbon fibers such as carbon nanotubes, conductive fibers such as metal fibers; metal powders such as aluminum powder; conductive whiskers such as zinc oxide whiskers and conductive potassium titanate whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as phenylene derivatives; etc. These conductive additives may be used alone or in combination of two or more.

[0069] The content of the conductive auxiliary agent in the electrode mixture is not particularly limited and can be set appropriately depending on the desired conductivity, etc.

[0070] (Other ingredients) The electrode mixture may contain components other than those described above. Examples of such components include dispersants. Examples of dispersants include carboxymethyl cellulose. [Example]

[0071] Examples 1 and 2, and Comparative Examples 1 and 2 Example 1 A laminate consisting of a substrate layer and an electrode active material layer was laser-heated to 200°C. As shown in Figure 2, the laminate was conveyed by a three-roller system, with the direction of the laminate being changed by 45° along a direction-changing roller, in which the peripheral speed of the end rollers (ends) was faster than that of the central roller (center). The laminate was then wound around winding rollers of different diameters to determine the diameter of the winding roller at which cracks occurred in the electrode active material layer. The diameter of the winding roller was reduced in 5 mm increments starting from 90 mm. Note that cracks in the electrode active material layer on winding rollers with larger diameters indicate that the electrode active material layer is prone to cracking. As a result, cracks occurred in the electrode active material layer when a winding roller with a diameter of 35 mm was used. When a similar evaluation was performed before laser heating, cracks occurred in the electrode active material layer when a winding roller with a diameter of 50 mm was used. This indicates that in Example 1, cracks were less likely to occur in the electrode active material layer after heating than before heating.

[0072] Example 2 3, the electrode active material layer was conveyed by roller conveyance and evaluated in the same manner as in Example 1, except that a direction-changing roller was used, which was composed of two rollers at both ends, had a further conveying roller upstream of the direction-changing roller in the conveying direction, and the peripheral speed of the direction-changing roller was faster than that of the conveying roller. As a result, when a take-up roller with a diameter of 35 mm was used, cracks occurred in the electrode active material layer.

[0073] Comparative Example 1 The electrode active material layer was transported by rollers and evaluated in the same manner as in Example 1, except that the peripheral speed at both ends was the same as that at the center. As a result, when a take-up roller with a diameter of 90 mm was used, cracks occurred in the electrode active material layer. That is, when a take-up roller with a diameter larger than those in Examples 1 and 2 was used, cracks occurred in the electrode active material layer.

[0074] Comparative Example 2 The electrode active material layer was transported and evaluated in the same manner as in Example 2, except that the peripheral speed of the direction-changing roller and the peripheral speed of the transport roller were the same. As a result, when a take-up roller with a diameter of 90 mm was used, cracks occurred in the electrode active material layer. That is, when a take-up roller with a diameter larger than those in Examples 1 and 2 was used, cracks occurred in the electrode active material layer. [Explanation of symbols]

[0075] 1. Laminate 10 Heating section 20 Direction change roller 21 Central part 22 Both ends 30 Conveyor roller

Claims

1. conveying the laminate, which has been heated to a temperature of 120° C. or higher and includes a base material layer and an electrode active material layer, by a roller such that the conveying direction of the laminate is changed by 45° or more along a direction-changing roller; and The direction-changing roller is configured to widen the laminate. How batteries are manufactured.

2. The method of claim 1 , wherein the deflecting roller has a center portion and opposite ends, and the peripheral speed of the opposite ends is faster than the peripheral speed of the center portion.

3. The direction-changing roller is composed of two rollers at both ends, a conveying roller is further provided upstream of the direction-changing roller in the conveying direction; and The peripheral speed of the direction-changing roller is faster than the peripheral speed of the conveying roller. The method of claim 1.

4. Further comprising drying the electrode active material layer before the roller conveyance; and In the drying step, the laminate is heated to a temperature of 120°C or higher. The method according to any one of claims 1 to 3.

5. The method according to claim 4 , wherein the laminate is heated by a laser in the drying step.

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