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] The present disclosure's method for manufacturing a battery includes conveying a laminate, which has a substrate layer and an electrode active material layer, heated to a temperature of 120°C or higher, by roller conveying the laminate such that the conveying direction of the laminate is changed by 45° or more along a direction-changing roller. In the present disclosure's method, the direction-changing roller is composed of a plurality of small-diameter rollers.

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] Japanese Patent Publication No. 2017-228349 [Patent Document 3] Patent Publication No. 2016-103402 [Patent Document 4] Patent Publication No. 2008-147114 [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 composed of a plurality of small diameter rollers. How batteries are manufactured. <Aspect 2> The plurality of small diameter rollers are arranged to form the outer periphery of a virtual large diameter roller; or the curvature of a curve connecting the outer peripheries of the plurality of small diameter rollers at the shortest distance gradually increases toward the downstream side in the conveying direction; The method described in Embodiment 1. <Aspect 3> the plurality of small diameter rollers are equally spaced apart; or The plurality of small diameter rollers are arranged at non-equidistant intervals. 3. The method according to embodiment 1 or 2. <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. 3. 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. 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, such that the conveying direction of the laminate is changed by 45° or more along a direction-changing roller. In the disclosed method, the direction-changing roller is composed of a plurality of small-diameter rollers.

[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] The Disclosing Party has discovered that when manufacturing batteries, cracking of the heat-treated electrode active material layer is suppressed by conveying the laminate, which has a substrate layer and an electrode active material layer heated to a temperature of 120°C or higher, along a direction-changing roller composed of multiple small-diameter rollers, in a manner that changes the direction of conveyance of the laminate by 45° or more. The reason for this is presumed to be as follows, although this is not intended to be bound by any theory: For example, if a laminate at room temperature is turned by 45° or more along a direction-changing roller, it is thought that multiple electrode active materials bound to each other via a binder will be separated in the electrode active material layer of the laminate, resulting in cracking of the electrode active material layer. In contrast, in the electrode active material layer of a laminate heated to a temperature of 120°C or higher, the flexibility of the binder is thought to be improved. By turning the direction of the laminate containing the electrode active material layer by 45° or more along a direction-changing roller in such a state, an appropriate stress is applied to the electrode active material layer containing the highly flexible binder, and it is thought that this allows the binder to expand while keeping the electrode active materials bound to each other. Furthermore, because the direction-changing roller is composed of multiple small-diameter rollers, heat transfer from the laminate to the direction-changing roller is reduced compared to a single, larger-diameter direction-changing roller that can change direction by the same angle. Therefore, it is thought that the binder's flexibility can be effectively maintained. As a result, cracking of the electrode active material layer is thought to be suppressed.

[0013] 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.

[0014] Figure 1 is a schematic diagram illustrating how the electrode active material layer is wound onto the winding reel 42 from the unwinding reel 41, through heating and roller transport. Figures 2 and 3 are schematic diagrams showing an example of a direction-changing roller used in the method of this disclosure. In particular, Figure 2 is an enlarged view of the direction-changing roller in Figure 1.

[0015] <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.

[0016] 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.

[0017] 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.

[0018] In the method of this disclosure, the direction-changing roller 20 is composed of a plurality of small-diameter rollers 21. With this configuration, the temperature of the heated electrode active material layer can be maintained above a predetermined temperature, thereby effectively suppressing cracking of the electrode active material layer.

[0019] The diameter of the small diameter rollers is not particularly limited, but may be 10 mm or more, 15 mm or more, 20 mm or more, 25 mm or more, or 30 mm or more, and may be 50 mm or less, 45 mm or less, 40 mm or less, 35 mm or less, or 30 mm or less. When the diameter of the small diameter rollers is within the above range, cracking of the electrode active material layer can be effectively suppressed. The diameters of the small diameter rollers may be the same or different from each other.

[0020] The number of small-diameter rollers is not particularly limited, but may be 2 or more, 3 or more, 4 or more, or 5 or more, and may be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, or 4 or less.

[0021] In the method of this disclosure, as illustrated in Figures 1 and 2, a plurality of small-diameter rollers 21 may be arranged to constitute the outer circumference of a virtual large-diameter roller 22. With such a configuration, it is easier to apply the stress necessary to increase the flexibility of the binder in the heated electrode active material layer, thereby effectively suppressing cracking of the electrode active material layer.

[0022] The diameter of the virtual large-diameter roller is not particularly limited, but may be 50 mm or more, 60 mm or more, 70 mm or more, 80 mm or more, 90 mm or more, 100 mm or more, 120 mm or more, 130 mm or more, 140 mm or more, or 150 mm or more, and may be 300 mm or less, 250 mm or less, 200 mm or less, 180 mm or less, 170 mm or less, 160 mm or less, or 150 mm or less. When the diameter of the virtual large-diameter roller is within the above range, cracking of the electrode active material layer can be effectively suppressed.

[0023] In the method of this disclosure, as illustrated in Figure 3, the curvature of the curve connecting the outer circumferences of the multiple small-diameter rollers 21 by the shortest distance may gradually increase as it moves downstream in the conveying direction. With this configuration, it is easier to apply the stress necessary to increase the flexibility of the binder in the heated electrode active material layer, thereby effectively suppressing cracking of the electrode active material layer.

[0024] As illustrated in Figure 2, the multiple small-diameter rollers 21 may be arranged at equal intervals. Alternatively, as illustrated in Figure 3, the multiple small-diameter rollers 21 may be arranged at non-equal intervals. The distance between the multiple small-diameter rollers is not particularly limited and can be set appropriately considering viewpoints such as suppressing cracking of the electrode active material layer and ease of transport.

[0025] 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.

[0026] 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.

[0027] The peripheral speed of the direction-changing roller 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 conveyance, and the like.

[0028] In the method disclosed herein, multi-stage direction-changing rollers may be used in the direction of transport of the electrode active material layer. The number of stages of the direction-changing rollers is not particularly limited and can be set as appropriate from the viewpoint of suppressing cracking of the electrode active material layer and saving space.

[0029] 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.

[0030] <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.

[0031] 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.

[0032] Drying may be performed by a predetermined heating unit 10. Heating and roller conveying may be performed continuously or discontinuously. For example, in Figure 1, the laminate is conveyed by rollers even during heating, thus demonstrating that heating and roller conveying are performed continuously. In contrast, the laminate does not need to be conveyed by rollers during heating, thus allowing heating and roller conveying to be performed discontinuously.

[0033] <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.

[0034] 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.

[0035] The pressing method is not particularly limited, and a conventional method can be used.

[0036] 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.

[0037] <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.

[0038] "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.

[0039] The batteries of the present disclosure include an electrode stack and, optionally, an electrolyte layer.

[0040] 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.

[0041] 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.

[0042] The battery of the present disclosure may be a primary battery or a secondary battery, particularly a lithium ion secondary battery.

[0043] The battery of the present disclosure may be a monopolar battery or a bipolar battery.

[0044] 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.

[0045] 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.

[0046] <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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The shape of the current collector is not particularly limited, but may be, for example, a quadrilateral such as a rectangle.

[0051] <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."

[0052] The electrode active material layer can be formed from an electrode mixture slurry.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The shape of the electrode active material layer is not particularly limited, but may be, for example, a quadrangle such as a rectangle.

[0057] (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."

[0058] 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.

[0059] 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.

[0060] The negative electrode active material may be in the form of particles, for example.

[0061] 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 / 2 O2), lithium nickel cobalt manganese oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3Composite oxides such as O2, olivine-type lithium phosphate oxide (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfide-based positive electrode active materials such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, and Li-VS compounds; materials using sulfur as an active material, such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon; etc. These positive electrode active materials may be used individually or in combination of two or more.

[0062] 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.

[0063] The positive electrode active material may be in the form of particles, for example.

[0064] (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.

[0065] 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.

[0066] 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.

[0067] (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.

[0068] 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.

[0069] (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]

[0070] Example 1 and Comparative Example 1 Example 1 A laminate consisting of a substrate layer and an electrode active material layer was laser-heated to 200°C. The laminate was conveyed by rollers, changing its direction by 45° along a direction-changing roller composed of multiple small-diameter rollers arranged at equal intervals to form the outer circumference of a virtual large-diameter roller, as shown in Figures 1 and 2. The diameters of the multiple small-diameter rollers were all 30 mm, and the diameter of the virtual large-diameter roller was 150 mm. Subsequently, the laminate was wound onto winding rollers of different diameters to identify the diameter of the winding roller that caused cracking in the electrode active material layer. The diameter of the winding roller was decreased by 5 mm increments from 90 mm. Note that cracking of the electrode active material layer with a larger diameter winding roller indicates that the electrode active material layer is prone to cracking. As a result, cracking occurred in the electrode active material layer when a winding roller with a diameter of 35 mm was used. Note that when a similar evaluation was performed before laser heating, cracking occurred in the electrode active material layer when a winding roller with a diameter of 50 mm was used. This means that in Example 1, the electrode active material layer after heating was less susceptible to cracking than before heating.

[0071] Comparative Example 1 The electrode active material layer was transported by roller and evaluated in the same manner as in Example 1, except that a single direction-changing roller was used. As a result, cracks occurred in the electrode active material layer when a winding roller with a diameter of 90 mm was used. In other words, cracks occurred in the electrode active material layer when a winding roller with a larger diameter than that used in Example 1 was used. [Explanation of symbols]

[0072] 1. Laminate 10 Heating section 20 Direction change roller 21 Small diameter rollers 22 Virtual large diameter 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 composed of a plurality of small diameter rollers. How batteries are manufactured.

2. The plurality of small diameter rollers are arranged to form the outer periphery of a virtual large diameter roller; or the curvature of a curve connecting the outer peripheries of the plurality of small diameter rollers at the shortest distance gradually increases toward the downstream side in the conveying direction; The method of claim 1.

3. the plurality of small diameter rollers are equally spaced apart; or The plurality of small diameter rollers are arranged at non-equidistant intervals. 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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