Method for manufacturing an electrode

Abstract

The present application provides a method for manufacturing an electrode with a further reduced number of steps. In the method for manufacturing an electrode, a negative electrode material is applied to one surface of a current collector foil, a first negative electrode layer is formed on the one surface and a second negative electrode layer, which is narrower than the first negative electrode layer, is formed on the first negative electrode layer, the first negative electrode layer and the second negative electrode layer are dried, a positive electrode material is applied to the other surface of the current collector foil, a positive electrode layer is formed on the other surface, the positive electrode layer is dried, and the first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressed. When the first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressed, the width of the second negative electrode layer is the same as the width of the positive electrode layer.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an electrode. Background Technology

[0002] Patent document 1 discloses a method for manufacturing an electrode, which involves coating an electrode material onto a current collector foil, drying the electrode material coated on the current collector foil, and applying pressure to the dried electrode material to manufacture the electrode.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-071827 Summary of the Invention

[0004] However, in the battery structure, the width of the negative electrode layer is wider than the width of the positive electrode layer, therefore the width of the negative electrode material coated on the current collector foil is larger than the width of the positive electrode material. Consequently, if pressure is applied to the negative and positive electrode layers formed on the current collector foil, the edges of the negative electrode layer are not pressurized, becoming thicker compared to the pressurized portion, thus creating a step difference in the negative electrode layer. Furthermore, when the fabricated electrode layers are stacked and housed in the battery casing, the metal foil connecting to the edges of the negative electrode layer sometimes breaks due to this step difference. Therefore, a pre-pressurization process is required to pre-pressurize the negative electrode layer formed on one side of the current collector foil across its entire width after coating the negative electrode material on one side and before coating the positive electrode material on the other side.

[0005] This invention was made to solve this problem, and its object is to provide a method for manufacturing an electrode with a further reduction in the number of steps.

[0006] In the electrode manufacturing method according to the first aspect of the present invention,

[0007] By coating a negative electrode material onto one side of the current collector foil, a first negative electrode layer is formed on said side, and a second negative electrode layer, narrower than the first negative electrode layer, is formed on said first negative electrode layer.

[0008] The first negative electrode layer and the second negative electrode layer are dried.

[0009] A positive electrode layer is formed on the other side by coating the positive electrode material onto the other side of the current collector foil.

[0010] The positive electrode layer is dried.

[0011] Pressure is applied to the first negative electrode layer, the second negative electrode layer, and the positive electrode layer.

[0012] When the first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressurized, the width of the second negative electrode layer is the same as the width of the positive electrode layer.

[0013] Invention Effects

[0014] According to the electrode manufacturing method of the first aspect of the present invention, a first negative electrode layer and a second negative electrode layer narrower than the width of the first negative electrode layer are formed on one side of the current collector foil, and a positive electrode layer is formed on the other side of the current collector foil. Furthermore, when the first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressurized, the width of the second negative electrode layer is the same as the width of the positive electrode layer. Therefore, the edge portion of the first negative electrode layer is not pressurized during the pressing process. However, the thickness of the first negative electrode layer before pressing is thinner than the sum of the thicknesses of the first negative electrode layer and the second negative electrode layer before pressing. Therefore, even if the edge portion of the first negative electrode layer is not pressurized during the pressing process, the thickness is thinner than or equal to the thickness of the pressurized first and second negative electrode layers. Thus, by avoiding the edge portion of the negative electrode layer being thicker than the portion of the pressurized negative electrode layer through the pressing process, a step difference at the edge portion of the negative electrode layer can be prevented. Therefore, a pre-pressurization process is unnecessary, reducing the number of processes. Therefore, it is possible to provide a method for manufacturing electrodes with a further reduction in the number of steps. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating an example of a method for manufacturing an electrode according to the first embodiment of the present invention.

[0016] Figure 2 This is a diagram illustrating the coating process of the electrode manufacturing method according to the first embodiment of the present invention.

[0017] Figure 3 This is a diagram illustrating the method for manufacturing the electrode according to the first embodiment and comparative example of the present invention. Detailed Implementation

[0018] Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following first embodiment. Furthermore, for the sake of clarity, the following description and drawings are appropriately simplified.

[0019] (First Embodiment)

[0020] Hereinafter, the manufacturing method of the electrode according to the first embodiment will be described with reference to the accompanying drawings. In the drawings of this specification, the X-axis is parallel to the transport direction of the current collector foil 200, the Y-axis is parallel to the width direction of the transported current collector foil 200 (the direction orthogonal to the transport direction), and the Z-axis is parallel to the vertical direction of the current collector foil 200. The manufacturing method of the electrode according to the first embodiment includes a coating process, a drying process, and a pressurizing process. Figure 1 This is a diagram illustrating a part of the method for manufacturing the electrode according to the first embodiment. Figure 1 This indicates the coating and drying processes. Furthermore, Figure 2This diagram illustrates the coating process of the electrode manufacturing method according to the first embodiment. Furthermore, Figure 3 This is a diagram illustrating the electrode manufacturing method according to the first embodiment and comparative example of the present invention. Additionally, in Figure 3 The diagram of the storage process shown omits the illustration of the current collector foil.

[0021] like Figure 1 As shown, in the coating process, the slurry supply device 110 supplies negative electrode material or positive electrode material to the coating section 120. The coating section 120 is equipped with a coating machine, and the coating section 120 coats the negative electrode material or positive electrode material onto the surface of the current collector foil 200 conveyed by the support roller 130. Thus, a negative electrode layer 300 or a positive electrode layer 400 (see reference) is formed on the surface of the current collector foil 200. Figure 3 Specifically, a negative electrode layer 300 is formed on one side 210 of the current collector foil 200, and a positive electrode layer 400 is formed on the other side 220 of the current collector foil 200.

[0022] In the drying process, the negative electrode layer 300 or the positive electrode layer 400 coated on the surface of the current collector foil 200 is dried.

[0023] In the pressing process, the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200 are pressed. Specifically, a pair of pressure rollers (not shown) clamp the current collector foil 200 on which the negative electrode layer 300 and the positive electrode layer 400 are formed and press it, thereby pressing the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200.

[0024] More specifically, firstly, in the coating process, a negative electrode layer 300 is formed on one side 210 of the current collector foil 200, and in the drying process, the negative electrode layer 300 formed on one side 210 of the current collector foil 200 is dried. Next, in the coating process, a positive electrode layer 400 is formed on the other side 220 of the current collector foil 200, and in the drying process, the positive electrode layer 400 formed on the other side 220 of the current collector foil 200 is dried. Finally, in the pressurizing process, pressure is applied to the negative electrode layer 300 and the positive electrode layer 400 formed on both sides of the current collector foil 200.

[0025] In the first embodiment, such as Figure 2 and Figure 3 As shown, two negative electrode layers 310 and 320 are formed on one surface 210 of the current collector foil 200. Specifically, a first negative electrode layer 310 and a second negative electrode layer 320, which is narrower than the first negative electrode layer 310, are formed on one surface 210 of the current collector foil 200. Furthermore, the first negative electrode layer 310 is formed on one surface 210 of the current collector foil 200, and the second negative electrode layer 320 is formed on the first negative electrode layer 310.

[0026] More specifically, such as Figure 2 As shown, two coating machines 121 and 122 are used to coat a first negative electrode layer 310 and a second negative electrode layer 320 on one surface 210 of the current collector foil 200. The first coating machine 121 is positioned further forward than the second coating machine 122 in the transport direction of the current collector foil 200. A first negative electrode material to form the first negative electrode layer 310 is supplied to the first coating machine 121, and a second negative electrode material to form the second negative electrode layer 320 is supplied to the second coating machine 122. Then, the first coating machine 121 coats the first negative electrode material on one surface 210 of the current collector foil 200, and the second coating machine 122 coats the second negative electrode material on the first negative electrode layer 310. Thus, the first negative electrode layer 310 is formed on one surface 210 of the current collector foil 200, and the second negative electrode layer 320 is formed on the first negative electrode layer 310.

[0027] The compositions of the first negative electrode material and the second negative electrode material can be different. Specifically, the amount (concentration) of binder contained in the first negative electrode material can be greater than the amount (concentration) of binder contained in the second negative electrode material. This reduces the amount (concentration) of binder, which acts as a resistor in the battery, contained in the overall negative electrode layer. Therefore, the amount of binder acting as a resistor can be optimized in the battery.

[0028] Furthermore, by comprising two negative electrode layers, a first negative electrode layer 310 and a second negative electrode layer 320, the negative electrode layer can be prevented from peeling off from the current collector foil 200 due to high-speed drying during the drying process. Specifically, if the negative electrode layer is dried at high speed, a migration phenomenon occurs where the adhesive contained in the negative electrode layer moves, making it easy for the negative electrode layer to peel off from the current collector foil 200. Therefore, by including a larger amount of adhesive in the first negative electrode material than usual, the negative electrode layer is less likely to peel off from the current collector foil 200 due to high-speed drying. Furthermore, by including a smaller amount of adhesive in the second negative electrode material than usual, the amount of adhesive can be controlled to an appropriate level throughout the negative electrode layer. Moreover, by comprising two negative electrode layers, a first negative electrode layer 310 and a second negative electrode layer 320, the drying time in the drying process can be shortened, the number of drying ovens used in the drying process can be reduced, and thus manufacturing costs can be suppressed.

[0029] Furthermore, the first coating machine 121 coats the first negative electrode material onto one surface 210 of the current collector foil 200 in such a way that the width of the first negative electrode layer 310 is narrower than the width (length in the Y-axis direction) of the second negative electrode layer 320. Specifically, the first coating machine 121 coats the first negative electrode material onto one surface 210 of the current collector foil 200 in such a way that the first negative electrode layer 310 has the width required for the structure of the negative electrode layer.

[0030] Furthermore, the second coating machine 122 coats the second negative electrode material in such a way that the width of the second negative electrode layer 320 is narrower than the width (length in the Y-axis direction) of the first negative electrode layer 310. In other words, the width of the first negative electrode material coated on the current collector foil 200 is wider than the width of the second negative electrode material coated on the first negative electrode layer 310.

[0031] Furthermore, the second coating machine 122 coats the second negative electrode material onto the first negative electrode layer 310 in such a way that the width of the dried second negative electrode layer 320 is the same as the width of the dried positive electrode layer 400. While ignoring the changes in the width of the second negative electrode layer 320 and the positive electrode layer 400 caused by drying, the positive electrode layer 400 is coated onto the other side 220 of the current collector foil 200 with the same width as the second negative electrode layer 320.

[0032] Furthermore, the width of the second negative electrode layer 320 formed on the first negative electrode layer 310 is the same as the width of the positive electrode layer 400 during the pressing process. Therefore, during the pressing process, pressure is applied to the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 across the entire width of the second negative electrode layer 320 and the positive electrode layer 400. On the other hand, there is no positive electrode layer 400 at the edge of the first negative electrode layer 310, i.e., at a position further outward than the second negative electrode layer 320; therefore, no pressure is applied during the pressing process, and no pressing occurs.

[0033] Furthermore, the thickness of the first negative electrode layer 310 is so thin that the metal foil connected to the edge of the first negative electrode layer 310 will not break when the electrodes are stacked in the battery casing. Specifically, the thickness of the first negative electrode layer 310 before pressurization is less than or equal to the sum of the thicknesses of the first negative electrode layer 310 and the second negative electrode layer 320 before pressurization. In other words, the thickness of the edge of the first negative electrode layer 310 after the pressurization process is thinner than or equal to the thickness of the first negative electrode layer 310 and the second negative electrode layer 320 before pressurization.

[0034] Furthermore, the thickness of the first negative electrode layer 310 before pressurization is thinner than the gap between the pressure rollers on the negative electrode layer side of the pair of pressure rollers that press the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 formed on the current collector foil 200 during the pressurization process and the current collector foil 200. Therefore, the edge portion of the first negative electrode layer 310 is not pressurized during the pressurization process.

[0035] refer to Figure 3 The differences between the electrode manufacturing methods of Comparative Examples 1 and 2 and the electrode manufacturing method of the first embodiment will be explained. Furthermore, in Figure 3 The diagram of the storage process omits the depiction of the diaphragm and current-collecting foil.

[0036] In the electrode manufacturing method of Comparative Example 1, after a negative electrode layer 300 is formed on one side 210 of the current collector foil 200 and dried, a positive electrode layer 400 is formed on the other side 220 of the current collector foil 200 and dried. Next, in this pressing step, the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200 are pressed. Since the width of the negative electrode layer 300 is wider than the width of the positive electrode layer 400 in the battery structure, in this pressing step, the negative electrode layer 300 and the positive electrode layer 400 are pressed over the entire width of the positive electrode layer 400. Therefore, the edge portion of the negative electrode layer 300 is not pressed in this pressing step, and becomes thicker compared to the pressed portion of the negative electrode layer 300. That is, a step difference (see reference) is formed on the negative electrode layer 300. Figure 3 (The portion enclosed by the dotted line). Furthermore, when electrodes thus fabricated are stacked and housed in the battery casing, the metal foil 500 connected to the edge of the negative electrode layer sometimes breaks due to this step difference. Specifically, as... Figure 3 As shown, if the electrodes are stacked, the thicker portions at the edges of the negative electrode layer 300 overlap (refer to...). Figure 3 The thickness difference arises between the thicker portion of the negative electrode layer 300 at its edge (enclosed by a dashed line) and the thinner portion of the thicker portion of the negative electrode layer 300 at its edge. Furthermore, sometimes the metal foil 500 cannot fully absorb this difference, causing it to break.

[0037] In the electrode manufacturing method of Comparative Example 2, after a negative electrode layer 300 is formed on one side 210 of the current collector foil 200 and dried, the negative electrode layer 300 formed on the current collector foil 200 is pressurized over its entire width in a pre-pressurization step. Next, a positive electrode layer 400 is formed on the other side 220 of the current collector foil 200 and dried. Then, in this pressing step, both the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200 are pressurized. In Comparative Example 2, the negative electrode layer 300 has already been thinned over its entire width in the pre-pressurization step. Therefore, in this pressing step, even if the edge of the negative electrode layer 300 is not pressurized, the thickness difference between the edge of the negative electrode layer 300 and the pressurized portion can be reduced. That is, the step difference formed on the negative electrode layer 300 can be reduced. Therefore, when the electrodes, which are made by stacking, are housed in the battery casing, it is possible to prevent the metal foil 500, which is connected to the edge of the negative electrode layer, from breaking due to the step difference.

[0038] In the electrode manufacturing method of the first embodiment, after forming a first negative electrode layer 310 and a second negative electrode layer 320 on one side 210 of the current collector foil 200 and drying the first negative electrode layer 310 and the second negative electrode layer 320, a positive electrode layer 400 is formed on the other side 220 of the current collector foil 200 and dried. Next, in this pressing step, the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 formed on the current collector foil 200 are pressed. The width of the second negative electrode layer 320 is narrower than the width of the first negative electrode layer 310 and the same as the width of the positive electrode layer 400. Furthermore, the thickness of the first negative electrode layer 310 before pressing is less than or equal to the sum of the thicknesses of the first negative electrode layer 310 and the second negative electrode layer 320 before pressing. Therefore, in this pressurization process, even if the edge of the first negative electrode layer 310 is not pressurized, it does not need to be thicker compared to the pressurized portions of the first negative electrode layer 310 and the second negative electrode layer 320. That is, it is possible to prevent the formation of a step difference at the edge of the first negative electrode layer 310. Furthermore, when the laminated electrodes are housed in the battery casing, it is possible to prevent the metal foil 500 connected to the edge of the negative electrode layer 300 from breaking.

[0039] According to the electrode manufacturing method of the first embodiment of the present invention, a first negative electrode layer 310 and a second negative electrode layer 320 narrower than the width of the first negative electrode layer 310 are formed on one surface 210 of the current collector foil 200, and a positive electrode layer 400 is formed on the other surface of the current collector foil 200. Furthermore, when the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 are pressurized, the width of the second negative electrode layer 320 is the same as the width of the positive electrode layer 400. Therefore, during the pressing process, the edge portion of the first negative electrode layer 310 is not pressurized. However, the thickness of the first negative electrode layer 310 before pressing is thinner than the sum of the thicknesses of the first negative electrode layer 310 and the second negative electrode layer 320 before pressing. Therefore, even if the first negative electrode layer 310 is not pressurized during the pressurization process, the thickness of its edge portion after the pressurization process is thinner or equal to the thickness of the first negative electrode layer 310 and the second negative electrode layer 320 after the pressurization process. Thus, by avoiding the edge portion of the negative electrode layer 300 becoming thicker than the portion of the negative electrode layer 300 under pressurization through the pressurization process, it is possible to prevent the formation of a step difference at the edge portion of the negative electrode layer 300. Therefore, a pre-pressurization process is unnecessary, reducing the number of processes. Therefore, a method for manufacturing an electrode with a further reduced number of processes can be provided.

[0040] Furthermore, by comprising two negative electrode layers, a first negative electrode layer 310 and a second negative electrode layer 320, the negative electrode layer can be prevented from peeling off from the current collector foil 200 due to high-speed drying during the drying process. Moreover, by using two negative electrode layers, the drying time in the drying process can be shortened, and the number of drying ovens used in the drying process can be reduced, thus suppressing manufacturing costs.

[0041] Furthermore, the amount of binder contained in the first negative electrode material that forms the first negative electrode layer 310 is less than the amount of binder contained in the second negative electrode material that forms the second negative electrode layer 320. This reduces the amount of binder, which acts as a resistor in the battery, contained throughout the negative electrode layer. Therefore, the amount of binder acting as a resistor in the battery can be optimized.

[0042] Furthermore, the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the invention.

[0043] Symbol Explanation

[0044] 110 - Slurry supply device, 120 - Coating section, 121 - First coating machine, 122 - Second coating machine, 130 - Support roller, 200 - Current collector foil, 210 - One side, 220 - The other side, 300 - Negative electrode layer, 310 - First negative electrode layer, 320 - Second negative electrode layer, 400 - Positive electrode layer, 500 - Metal foil.

Claims

1. A method for manufacturing an electrode, characterized in that, By coating a negative electrode material onto one side of the current collector foil, a first negative electrode layer is formed on said side, and a second negative electrode layer, narrower than the first negative electrode layer, is formed on said first negative electrode layer. The first negative electrode layer and the second negative electrode layer are dried. A positive electrode layer is formed on the other side by coating the positive electrode material onto the other side of the current collector foil. The positive electrode layer is dried. Pressure is applied to the first negative electrode layer, the second negative electrode layer, and the positive electrode layer. When the first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressurized, the width of the second negative electrode layer is the same as the width of the positive electrode layer.

2. The method for manufacturing the electrode according to claim 1, characterized in that, The thickness of the first negative electrode layer before pressurization is less than or equal to the sum of the thicknesses of the first negative electrode layer and the second negative electrode layer after pressurization.

3. The method for manufacturing the electrode according to claim 1 or 2, characterized in that, The amount of binder contained in the first negative electrode material that forms the first negative electrode layer is less than the amount of binder contained in the second negative electrode material that forms the second negative electrode layer.

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