Electrode manufacturing method

Abstract

The objective is to improve the curability of the resin material at the edges of the active material layer. [Solution] A method for manufacturing a battery, comprising the steps of covering the edge of the active material layer on the current collector foil with a photocurable and thermocurable resin material, curing the resin material with light, and further curing the resin material with heat, in this order.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrode.

Background Art

[0002] Patent Document 1 describes a method for manufacturing an electrode for a lithium-ion secondary battery including an active material layer, which includes applying an adhesive to the edge of the active material in order to suppress peeling at the edge of the active material and slipping of the active material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When curing the resin material applied to the end of the active material layer, the resin material may not be sufficiently cured. An example of the problem to be solved by the present invention is to improve the curability of the resin material at the end of the active material layer.

Means for Solving the Problems

[0005] According to the present invention, there is provided a method for manufacturing an electrode described below. [1] A step of covering an end of an active material layer on a current collector foil with a resin material having photocurability and thermocurability, A step of curing the resin material by light, And a step of advancing the curing of the resin material by heat, A method for manufacturing an electrode, which performs the steps in this order. [2] After the step of curing the resin material with light, the step of winding the current collector foil once is performed, and then the step of curing the resin material with heat is performed. A method for manufacturing electrodes as described in [1]. [3] In the process of curing the resin material by heat, the process includes heating the resin material. A method for manufacturing an electrode as described in [1] or [2]. [Effects of the Invention]

[0006] According to the present invention, the curability of the resin material can be improved at the edges of the active material layer. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of an electrode for a lithium-ion secondary battery. [Figure 2] This is a schematic diagram of the first manufacturing apparatus. [Figure 3] This is a schematic diagram of the second manufacturing apparatus. [Figure 4] This is a diagram showing the ends of the electrodes. [Figure 5] This is a flowchart illustrating the method for manufacturing electrodes according to this embodiment. [Figure 6] This is a top view of the electrode according to this embodiment. [Figure 7] This figure shows the first example of the fifth step. [Figure 8] This figure shows a second example of the fifth step. [Figure 9] This is a first example of a flowchart diagram of the fourth step according to this embodiment. [Figure 10] This is a second example of a flowchart diagram of the fourth step according to this embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0009] As an example of the electrode according to the present embodiment, an electrode 10 for a lithium ion secondary battery is shown in FIG. 1. As shown in FIG. 1, the electrode 10 for a lithium ion secondary battery includes a current collector foil 11 as an example of a base material, an active material layer 12a is formed on one surface of the current collector foil 11, and an active material layer 12b is formed on the other surface. And an adhesive layer 13a is formed between the current collector foil 11 and the active material layer 12a, and an adhesive layer 13b is formed between the current collector foil 11 and the active material layer 12b. Note that only one of the active material layer 12a and the adhesive layer 13a, and the active material layer 12b and the adhesive layer 13b may be formed on the current collector foil 11. When the electrode 10 for a lithium ion secondary battery is a negative electrode plate, the active material layer 12a and the active material layer 12b are formed of a negative electrode active material. When the electrode 10 for a lithium ion secondary battery is a positive electrode plate, the active material layer 12a and the active material layer 12b are formed of a positive electrode active material. Further, the electrode 10 for a lithium ion secondary battery may be an electrode for a bipolar in which one of the active material layer 12a and the active material layer 12b is a negative electrode active material layer and the other is a positive electrode active material layer. The details of the materials will be described later.

[0010] And, as shown in FIG. 1, at least one end portion, preferably both end portions of the active material layer 12a and the active material layer 12b are covered with a resin portion 14. Thereby, it is possible to suppress the active material from being exfoliated.

[0011] For example, the thickness of the active material layer 12a increases over a predetermined range from the end, and then hardly changes. The resin portion 14 covers, for example, the entire region of at least the portion where the thickness of the active material layer 12a increases. The same applies when the resin portion 14 covers the active material layer 12b.

[0012] FIG. 2 is a schematic view of a first manufacturing apparatus 100 for an electrode according to the present embodiment. FIG. 3 is a schematic view of a second manufacturing apparatus 200 for an electrode according to the present embodiment.

[0013] As shown in FIG. 2, as an example, the first manufacturing apparatus 100 includes an adhesive layer forming unit 110, an active material supply unit 120, a first press roll 130, a resin part forming unit 140, an unwinding roll 150a, and a winding roll 150b. Further, the second manufacturing apparatus 200 includes a second press roll 210, an unwinding roll 220a, and a winding roll 220b. Hereinafter, the details of each configuration will be described.

[0014] [Adhesive layer forming unit 110] The adhesive layer forming unit 110 applies an adhesive to at least one surface of the current collector foil 11 to form an adhesive layer. The type of the current collector foil is not particularly limited, and examples thereof include aluminum and copper. The adhesive applied to at least one surface of the current collector foil 11 preferably contains a conductive material, but is not limited thereto. The adhesive layer is formed entirely or partially, for example, by applying and drying the adhesive. Further, the adhesive layer may be formed uniformly or in a pattern. The type of the adhesive is not particularly limited, and examples thereof include fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinyl fluoride (PVF), conductive polymers such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles, synthetic rubbers such as styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), isoprene rubber (IR), and acrylonitrile-butadiene rubber (NBR), water-soluble resins such as polyvinylpyrrolidone, or polysaccharides such as carboxymethyl cellulose (CMC), xanthan gum, guar gum, and pectin, and acrylic resins such as acrylates and methacrylates. Further, the type of the conductive material is not particularly limited, and examples thereof include carbon blacks such as acetylene black and ketjen black, activated carbon, graphite, mesoporous carbon, fullerenes, carbon fibers such as carbon nanotubes, carbon nanofibers, and carbon nanobrushes. Furthermore, the adhesive layer may include two or more layers. For example, the adhesive layer may include a first adhesive layer formed to contact one side of the current collector foil 11, and a second adhesive layer formed to contact the side of the first adhesive layer opposite to the current collector foil 11. Furthermore, if the second adhesive layer does not contain a conductive material, or if the conductivity of the conductive material in the second adhesive layer is lower than that of the conductive material in the first adhesive layer, it is preferable that the second adhesive layer be formed to partially or patternably overlap the first adhesive layer. This ensures that at least a portion of the first adhesive layer does not overlap the second adhesive layer, thereby contacting the active material layer 12 and ensuring sufficient electrical conductivity between the current collector foil 11 and the active material layer 12. The pattern shape may be dot-like, or for example, striped, grid-like, etc. The shape of the dots may be a fixed shape such as a circle, ellipse, polygon (triangle, square, pentagon, hexagon, etc.), or it may be an irregular shape. The arrangement of the dots, the spacing between adjacent dots, the spacing of the stripes, and the spacing of the intersections of the grid lines may be regular or random. The adhesive layer forming section 110 includes, as an example, an adhesive application section 111 and an adhesive drying section 112.

[0015] As the unwinding roll 150a and the winding roll 150b rotate and the current collector foil 11 is transported, adhesive is continuously applied to one surface of the current collector foil 11 by the adhesive application unit 111. Methods for applying the adhesive include, but are not limited to, die application, comma application, lip application, transfer application, inkjet application, doctor blade application, and screen printing. Subsequently, the adhesive drying unit 112 dries the adhesive, forming an adhesive layer. The drying temperature is, for example, 80°C to 150°C. The drying time is, for example, 1 second to 30 seconds. The thickness of the adhesive layer is, for example, 0.01 μm to 2 μm.

[0016] [Active material supply section 120] Next, the active material supply unit 120 supplies the active material onto the adhesive layer described above. The active material supplied by the active material supply unit 120 is, for example, a powder material with an average particle size D50 of 5 μm or more and 110 μm or less. More specifically, it may be a granulated material obtained by mixing and dispersing the active material powder with a binder and a conductive additive in a solvent, and then removing the solvent by drying to form an aggregate of active material powder. In the following description, the active material supply unit 120 will be assumed to supply a granulated material.

[0017] Furthermore, a squeegee section 121 may be provided downstream of the active material supply section 120. The squeegee section 121 levels the granules supplied onto the adhesive layer by the active material supply section 120. The squeegee section 121 is positioned at a predetermined distance from the current collector foil 11, and the granules are leveled as the current collector foil 11 is transported beneath the squeegee section 121. The shape of the squeegee section 121 is not particularly limited, but as an example, it may be a roller that rotates in accordance with the transport of the current collector foil 11, or it may be plate-shaped. The predetermined distance is, as an example, 50 μm to 300 μm.

[0018] [First press roll 130] The first press roll 130 temporarily presses the layer of granulated material supplied by the active material supply unit 120 (hereinafter referred to as the granular layer) to fix the granulated material. The linear pressure when the first press roll 130 presses is, for example, 0.1 ton / cm or more and 1 ton / cm or less.

[0019] [Resin part forming part 140] The resin forming section 140 forms a resin section 14 at the edge of the granular layer. Details of the edge will be described later. The resin forming section 140 includes, as an example, a resin coating section 141 and a resin curing section 142.

[0020] The resin coating section 141 applies resin material to the edges of the granular layer. For example, the resin coating section 141 applies resin material to an area of ​​1 mm or less inward from the edge of the granular layer. Then, the resin curing section 142 hardens the applied resin material, thereby forming the resin section 14. The specific method by which the resin curing section 142 hardens the resin material will be described later.

[0021] Next, the current collector foil 11 is removed from the winding roll 150b and attached to the second manufacturing device 200.

[0022] [Second press roll 210] Next, the current collector foil 11 is conveyed by the rotation of the unwinding roll 220a and the winding roll 220b of the second manufacturing apparatus 200. The second press roll 210 forms the active material layer by performing a final press on the pre-pressed granular layer. The linear pressure when the second press roll 210 presses is, for example, between 0.3 ton / cm and 6.5 ton / cm.

[0023] Figure 4 shows details of the end of the active material layer 12 formed by the above process. As shown in the figure, the end of the active material layer 12 includes an inclined portion 21. The angle of inclination of the inclined portion 21 is determined by the angle of repose of the granulated material, etc. The inclined portion 21 is a part where the granulated material was not supplied sufficiently, and where insufficient linear pressure was not applied in the first pressing process by the first press roll 130 and the second pressing process by the second press roll 220, potentially resulting in a lower density of the granulated material. The end of the active material layer 12 also includes a flat portion 22 inside the inclined portion 21. The flat portion 22 is a part where more granulated material is supplied than in the inclined portion 21, and where the density of the granulated material may be lower because the granulated material is pushed towards the inclined portion 21 when pressed. As an example, the inclined portion 21 is the part with a thickness of 95% or less of the average thickness D of the active material layer 12, and the flat portion 22 is the part within 2 mm of the inclined portion 21.

[0024] [Method for manufacturing electrodes] Figure 5 illustrates the method for manufacturing an electrode according to this embodiment. As shown in the figure, the following steps are performed in order: a first step (step S10) of coating the current collector foil 11 with an undercoat layer; a second step (step S20) of arranging granules that will become the active material layer 12 on the undercoat layer to form a granular layer; a third step (step S30) of pressing the granular layer; and a fourth step (step S40) of covering the edges of the granular layer with a resin material and curing this resin material to form a resin part 14. The method for manufacturing an electrode may also include a fifth step (step S50) of cutting the current collector foil 11 and the active material layer 12.

[0025] The first step is carried out by forming an adhesive layer using the adhesive layer forming unit 110, as described above. The second step is carried out by supplying granules (granulated material) that will become the active material layer using the active material supply unit 120.

[0026] Furthermore, the third step is carried out by pressing the material against at least one of the first press roll 130 and the second press roll 210.

[0027] Furthermore, the fourth step is carried out by forming the resin part 14 with the resin part forming part 140. In the fourth step, at least a portion of the side and top surfaces of the granular layer may be covered with the resin part 14. Specifically, it is preferable that the top surface of the granular layer is covered with the resin part 14 in a range of 1 mm or less from the edge of the granular layer. This further suppresses the detachment of granules. However, in the fourth step, only the side surfaces of the resin part 14 may be covered with the resin part 14.

[0028] Figure 6 shows a top view of the current collector foil 11, active material layer 12, and resin portion 14 after the first to fourth processes. As shown in the figure, the resin portion 14 is formed at the end of the active material layer 12 in the width direction, which is perpendicular to the transport direction. The width W of the resin portion 14 in the width direction is, for example, 1 mm to 10 mm.

[0029] The fifth step will be explained using Figures 7 and 8. In the fifth step, the current collector foil 11 and the active material layer 12 shown in Figure 6 are cut along the dashed line shown in Figure 7 or Figure 8. This yields the electrode shown in Figure 1. In other words, Figure 1 shows the A-A' cross section in Figure 7 or Figure 8.

[0030] In the case of the cutting pattern shown in Figure 8, one end of the active material layer 12 is cut off. Therefore, when cutting using the cutting pattern shown in Figure 8 in the fifth step, it is sufficient to form the resin portion 14 only on one end of the active material layer 12 in the fourth step.

[0031] [4th step] The fourth step will be explained in more detail below. Figure 9 is a flowchart of the fourth step. First, it is preferable that the resin material applied in the fourth step has both photocurability and thermocurability. Then, as shown in Figure 9, in the fourth step, it is preferable to perform a photocuring step (step S410) in which the resin material is photocured, followed by a thermocuring step (step S420) in which the resin material is thermocured. An example of photocuring is ultraviolet curing. As an example, in the photocuring step, the material is cured to a stage where the curing rate is 60% to 90%, and in the thermocuring step, it is cured to a stage where the curing rate is 98% to 100%. The curing rate is calculated from the degree of disappearance of peaks originating from polymerizable functional groups, which is measured by Fourier transform infrared (FTIR) spectroscopy or the like.

[0032] Specifically, resin materials that are photocurable and thermocurable include those with multiple polymerizable functional groups, combinations of acrylic and epoxy groups, multiple polymerization initiators, and combinations of photopolymerization initiators and thermal polymerization initiators. As a commercially available product, MX-80 manufactured by SunYurec Co., Ltd. can be used as an example.

[0033] This allows parts of the resin material that were not sufficiently cured by light (for example, resin material that has penetrated into the interior of the granules) to be sufficiently cured by heat curing.

[0034] For example, in the resin curing section 142 of the first manufacturing apparatus 100 shown in Figure 2, both a photocuring process and a thermocuring process may be performed. In this case, the resin curing section 142 includes, for example, a part that irradiates the resin material with light and a part that heats the resin material. The heating of the resin material is, for example, performed at a temperature of 100°C to 180°C for a time of 1 minute to 5 minutes.

[0035] Alternatively, the photocuring process and the thermocuring process may be carried out by different devices. Figure 10 is a flowchart of a modified example of the fourth process. For example, in the resin curing section 142 of the first manufacturing apparatus 100 shown in Figure 2, only the photocuring process is performed (step S410), and after the photocuring process, the current collector foil 11 is wound up once (step S411). Then, the current collector foil 11 is attached to another device that performs the thermocuring process, and the thermocuring process is carried out (step S420).

[0036] Furthermore, the thermosetting process may be carried out at room temperature. For example, after winding up the current collector foil 11 that has only undergone the photocuring process, the thermosetting process may be carried out by leaving the current collector foil 11 at room temperature. Specifically, it may be carried out by leaving it at a temperature of 20°C to 30°C for a period of 1 hour to 24 hours.

[0037] As described above, according to this embodiment, since the resin material is cured by both light curing and heat curing, the curability of the resin material is improved at the edges of the active material layer. Furthermore, the light curing process and the heat curing process can be freely designed. Therefore, the manufacturing process can be designed to suit the manufacturing conditions of the product.

[0038] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted.

[0039] Furthermore, although the flowchart used in the above description shows multiple steps (processes) in order, the execution order of the steps performed in each embodiment is not limited to the order in which they are described. In each embodiment, the order of the illustrated steps can be changed to the extent that it does not impede the content. Also, the above embodiments can be combined to the extent that their contents do not conflict. [Explanation of symbols]

[0040] 10 electrodes 110 Adhesive layer forming part 120 Active material supply section 130 First press roll 140 Resin part forming part 210 Second press roll

Claims

1. A process of covering the edges of the active material layer on the current collector foil with a resin material that is photocurable and thermocurable, A step of curing the aforementioned resin material with light, and a step of curing the resin material by heat, A method for manufacturing electrodes, which involves performing the following steps in this order.

2. After the step of curing the resin material with light, the step of winding the current collector foil once is performed, and then the step of curing the resin material with heat is performed. The method for manufacturing an electrode according to claim 1.

3. In the process of curing the resin material by heat, the process includes heating the resin material. A method for manufacturing an electrode according to claim 1 or 2.

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