Electrode manufacturing method

Abstract

The present invention provides a method for manufacturing electrodes with a reduced number of steps. [Solution] The electrode manufacturing method involves coating one surface 210 of the current collector foil 200 with a negative electrode material to form a first negative electrode layer 310 on that surface 210, and a second negative electrode layer 320 on the first negative electrode layer 310 that is narrower than the first negative electrode layer 310, drying the first negative electrode layer 310 and the second negative electrode layer 320, coating the other surface 220 of the current collector foil 200 with a positive electrode material to form a positive electrode layer 400 on that surface 220, drying the positive electrode layer 400, and pressing the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400. When pressing the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400, the width of the second negative electrode layer 320 and the width of the positive electrode layer 400 are the same.

Description

Technical Field

[0006] , , , ,

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

Background Art

[0002] Patent Document 1 discloses a method for manufacturing an electrode, in which an electrode material is applied onto a current collector foil, the electrode material applied onto the current collector foil is dried, and the dried electrode material is pressed to produce an electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, due to the structure of the battery, the width of the negative electrode layer is wider than that of the positive electrode layer, so the width of the negative electrode material applied onto the current collector foil is larger than that of the positive electrode material. Therefore, when the negative electrode layer and the positive electrode layer formed on the current collector foil are pressed, the edges of the negative electrode layer are not pressed and become thicker compared to the pressed portion of the negative electrode layer, resulting in a step in the negative electrode layer. And when the manufactured electrodes are stacked and housed in the battery case, the metal foil connected to the edges of the negative electrode layer may be broken due to this step. Therefore, there has been a problem that a prepress process is required to pre-press the negative electrode layer formed on one side of the current collector foil over its entire width before applying the positive electrode material onto the other side after applying the negative electrode material onto one side of the current collector foil.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a method for manufacturing an electrode with a further reduced number of steps.

Means for Solving the Problems

[0006] A method for manufacturing an electrode according to a first aspect of the present invention is: By coating one side of the current collector foil with a negative electrode material, a first negative electrode layer is formed on the said one side, 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. By coating the other surface of the current collector foil with a positive electrode material, a positive electrode layer is formed on the other surface. The positive electrode layer is dried, The first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressed together. When pressing the first negative electrode layer, the second negative electrode layer, and the positive electrode layer, the width of the second negative electrode layer and the width of the positive electrode layer are the same. [Effects of the Invention]

[0007] 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 first negative electrode layer are formed on one side of a current collector foil, and a positive electrode layer is formed on the other side of the current collector foil. 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 and the width of the positive electrode layer are the same. Therefore, the edge of the first negative electrode layer is not pressed during the pressing process. However, the thickness of the first negative electrode layer before pressing is thinner than the combined thickness of the first negative electrode layer and the second negative electrode layer before pressing. Therefore, the thickness of the edge of the first negative electrode layer after the pressing process is thinner than or equal to the thickness of the pressed first and second negative electrode layers, even if it is not pressed during the pressing process. This prevents the edge of the negative electrode layer from becoming thicker than the pressed portion of the negative electrode layer due to the pressing process, and prevents the formation of a step at the edge of the negative electrode layer. Therefore, the pre-pressing process is eliminated, reducing the number of steps. Thus, a method for manufacturing electrodes with even fewer steps can be provided. [Brief explanation of the drawing]

[0008] [Figure 1]This figure illustrates an example of a method for manufacturing an electrode according to the first embodiment of the present invention. [Figure 2] This figure illustrates the coating process of the electrode manufacturing method according to the first embodiment of the present invention. [Figure 3] This figure illustrates the method for manufacturing electrodes according to the first embodiment and comparative example of the present invention. [Modes for carrying out the invention]

[0009] A first embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following first embodiment. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0010] (First embodiment) The method for manufacturing an electrode according to the first embodiment will be described below with reference to the 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 (direction perpendicular to the transport direction) of the transported current collector foil 200, and the Z-axis is parallel to the vertical direction of the current collector foil 200. The method for manufacturing an electrode according to the first embodiment comprises a coating step, a drying step, and a pressing step. Figure 1 is a diagram illustrating a part of the method for manufacturing an electrode according to the first embodiment. Figure 1 shows the coating step and the drying step. Figure 2 is a diagram illustrating the coating step of the method for manufacturing an electrode according to the first embodiment. Figure 3 is a diagram illustrating the method for manufacturing an electrode according to the first embodiment and a comparative example of the present invention. Note that the current collector foil is not shown in the diagram of the storage step shown in Figure 3.

[0011] As shown in Figure 1, in the coating process, the slurry supply device 110 supplies the negative electrode material or positive electrode material to the coating unit 120. The coating unit 120 is equipped with a die coater and coats the negative electrode material or positive electrode material onto the surface of the current collector foil 200, which is conveyed by the backup roll 130. As a result, a negative electrode layer 300 or a positive electrode layer 400 (see Figure 3) is formed on the surface of the current collector foil 200. Specifically, the negative electrode layer 300 is formed on one surface 210 of the current collector foil 200, and the positive electrode layer 400 is formed on the other surface 220 of the current collector foil 200.

[0012] In the drying process, the negative electrode layer 300 or positive electrode layer 400 coated on the surface of the current collector foil 200 is dried.

[0013] In the pressing process, the negative electrode layer 300 and positive electrode layer 400 formed on the current collector foil 200 are pressed. Specifically, a pair of press rolls (not shown) press the current collector foil 200, on which the negative electrode layer 300 and positive electrode layer 400 are formed, by sandwiching and pressing it.

[0014] More specifically, first, a negative electrode layer 300 is formed on one surface 210 of the current collector foil 200 in a coating process, and the negative electrode layer 300 formed on one surface 210 of the current collector foil 200 is dried in a drying process. Next, a positive electrode layer 400 is formed on the other surface 220 of the current collector foil 200 in a coating process, and the positive electrode layer 400 formed on the other surface 220 of the current collector foil 200 is dried in a drying process. Finally, in a pressing process, the negative electrode layer 300 and the positive electrode layer 400 formed on both sides of the current collector foil 200 are pressed.

[0015] In the first embodiment, as shown in Figures 2 and 3, 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. 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 top of the first negative electrode layer 310. More specifically, as shown in Figure 2, two die coaters 121 and 122 are used to coat one side 210 of the current collector foil 200 with a first negative electrode layer 310 and a second negative electrode layer 320. The first die coater 121 is positioned closer to the front of the second die coater 122 in the transport direction of the current collector foil 200. The first die coater 121 is supplied with the first negative electrode material that will become the first negative electrode layer 310, and the second die coater 122 is supplied with the second negative electrode material that will become the second negative electrode layer 320. The first die coater 121 coats the first negative electrode material onto one side 210 of the current collector foil 200, and the second die coater 122 coats the second negative electrode material on top of the first negative electrode layer 310. As a result, a first negative electrode layer 310 is formed on one surface 210 of the current collector foil 200, and a second negative electrode layer 320 is formed on the first negative electrode layer 310.

[0016] The composition of the first negative electrode material and the composition of the second negative electrode material may be different. Specifically, the amount (concentration) of binder contained in the first negative electrode material may be greater than the amount (concentration) of binder contained in the second negative electrode material. This makes it possible to reduce the amount (concentration) of binder that acts as resistance in the battery, contained throughout the negative electrode layer. Therefore, it is possible to optimize the amount of binder that acts as resistance in the battery.

[0017] In addition, since the negative electrode layer is composed of two layers, namely the first negative electrode layer 310 and the second negative electrode layer 320, it is possible to prevent the negative electrode layer from peeling off from the current collector foil 200 due to high-speed drying in the drying process. Specifically, when the negative electrode layer is dried at high speed, a phenomenon called migration occurs in which the binder contained in the negative electrode layer moves, making the negative electrode layer more likely to peel off from the current collector foil 200. Therefore, by making the amount of the binder contained in the first negative electrode material larger than normal, it is possible to make the negative electrode layer less likely to peel off from the current collector foil 200 due to high-speed drying. Further, by making the amount of the binder contained in the second negative electrode material less than normal, the amount of the binder as the entire negative electrode layer can be suppressed to an appropriate amount. In addition, since the negative electrode layer is composed of two layers, namely the first negative electrode layer 310 and the second negative electrode layer 320, the drying time in the drying process can be shortened, and the number of drying furnaces used in the drying process can be reduced, so that the manufacturing cost can be suppressed.

[0018] In addition, the first die coater 121 applies the first negative electrode material to one surface 210 of the current collector foil 200 such that the width of the first negative electrode layer 310 is narrower than the width (the length in the Y-axis direction) of the second negative electrode layer 320. Specifically, the first die coater 121 applies the first negative electrode material onto one surface 210 of the current collector foil 200 such that the first negative electrode layer 310 has a width required for the structure of the negative electrode layer.

[0019] In addition, the second die coater 122 applies the second negative electrode material such that the width of the second negative electrode layer 320 is narrower than the width (the length in the Y-axis direction) of the first negative electrode layer 310. In other words, the width of the current collector foil 200 to which the first negative electrode material is applied is wider than the width of the second negative electrode material applied onto the first negative electrode layer 310. In addition, the second die coater 122 applies the second negative electrode material onto the first negative electrode layer 310 such that the width of the second negative electrode layer 320 after drying is the same as the width of the positive electrode layer 400 after drying. When the change in the width of the second negative electrode layer 320 due to drying and the change in the width of the positive electrode layer 400 can be ignored, the positive electrode layer 400 is applied onto the other surface 220 of the current collector foil 200 with the same width as the second negative electrode layer 320.

[0020] Further, 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 when being pressed in the pressing process. Thereby, in the pressing process, pressing force is applied to the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 over the widths of the second negative electrode layer 320 and the positive electrode layer 400, and they are pressed. On the other hand, since there is no positive electrode layer 400 at the corresponding position on the edge of the first negative electrode layer 310, that is, the portion located outside the second negative electrode layer 320, no pressing force is applied in the pressing process and it is not pressed.

[0021] Further, the thickness of the first negative electrode layer 310 is thin enough that the metal foil connected to the edge of the first negative electrode layer 310 does not break when the stacked electrodes are stored in the battery case. Specifically, the thickness of the first negative electrode layer 310 before being pressed is not more than the thicknesses of the pressed first negative electrode layer 310 and second negative electrode layer 320. In other words, the thickness of the edge of the first negative electrode layer 310 after the pressing process is thinner than or equal to the thicknesses of the pressed first negative electrode layer 310 and second negative electrode layer 320. Further, the thickness of the first negative electrode layer 310 before being pressed is thinner than the gap between the negative electrode layer side pressing roll of the pair of pressing rolls 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 and the current collector foil 200 in the pressing process. Therefore, the edge of the first negative electrode layer 310 is not pressed in the pressing process.

[0022] While referring to FIG. 3, the differences between the manufacturing methods of the electrodes of Comparative Example 1 and Comparative Example 2 and the manufacturing method of the electrode of the first embodiment will be described. In the figure of the storage process in FIG. 3, the drawing of the separator and the current collector foil is omitted. In the electrode manufacturing method of Comparative Example 1, a negative electrode layer 300 is formed on one surface 210 of the current collector foil 200 and the negative electrode layer 300 is dried. Then, a positive electrode layer 400 is formed on the other surface 220 of the current collector foil 200 and the positive electrode layer 400 is dried. Next, in the pressing process, the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200 are pressed. Due to the structure of the battery, the width of the negative electrode layer 300 is wider than the width of the positive electrode layer 400. Therefore, in the pressing process, the negative electrode layer 300 and the positive electrode layer 400 are pressed across the width of the positive electrode layer 400. As a result, the edges of the negative electrode layer 300 are not pressed in the pressing process and become thicker than the pressed portion of the negative electrode layer 300. In other words, a step is formed in the negative electrode layer 300 (see the area enclosed by the dashed line in Figure 3). When electrodes manufactured in this manner are stacked and housed in a battery casing, the metal foil 500 connected to the edge of the negative electrode layer may tear due to the step. Specifically, as shown in Figure 3, when electrodes are stacked, the thicker portions of the edges of the negative electrode layer 300 overlap (see the area enclosed by the dashed line in Figure 3), creating a thickness difference between areas where the overlap of the thicker portions of the edges of the negative electrode layer 300 is greater and areas where the overlap of the thicker portions of the edges of the negative electrode layer 300 is less. The metal foil 500 may not be able to absorb this difference, and may tear.

[0023] In the electrode manufacturing method of Comparative Example 2, a negative electrode layer 300 is formed on one surface 210 of the current collector foil 200, and after the negative electrode layer 300 is dried, in the pre-press process, the negative electrode layer 300 formed on the current collector foil 200 is pressed over its entire width. Next, a positive electrode layer 400 is formed on the other surface 220 of the current collector foil 200, and the positive electrode layer 400 is dried. Next, in the main pressing process, the negative electrode layer 300 and the positive electrode layer 400 formed on the current collector foil 200 are pressed. In Comparative Example 2, the negative electrode layer 300 is already thinned over its entire width in the pre-press process. Therefore, even if the edges of the negative electrode layer 300 are not pressed in the main pressing process, it is possible to reduce the thickness of the edges of the negative electrode layer 300 compared to the pressed portion of the negative electrode layer 300. In other words, the step formed on the negative electrode layer 300 can be reduced. This prevents the metal foil 500 connected to the edge of the negative electrode layer from being torn by the step when the fabricated electrodes are stacked and housed in the battery housing.

[0024] In the electrode manufacturing method of the first embodiment, a first negative electrode layer 310 and a second negative electrode layer 320 are formed on one surface 210 of the current collector foil 200, and after the first and second negative electrode layers 310 and 320 are dried, a positive electrode layer 400 is formed on the other surface 220 of the current collector foil 200, and the positive electrode layer 400 is dried. Next, in the pressing process, 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 is the same as the width of the positive electrode layer 400. Also, the thickness of the first negative electrode layer 310 before pressing is less than or equal to the thickness of the pressed first and second negative electrode layers 310 and 320. Therefore, even if the edges of the first negative electrode layer 310 are not pressed during this pressing process, they will not become thicker than the pressed portions of the first and second negative electrode layers 320. In other words, it is possible to prevent the formation of a step at the edge of the first negative electrode layer 310. Furthermore, when the manufactured electrodes are stacked and housed in the battery housing, it is possible to prevent the metal foil 500 connected to the edge of the negative electrode layer 300 from tearing.

[0025] 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, which is narrower than 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. When the first negative electrode layer 310, the second negative electrode layer 320, and the positive electrode layer 400 are pressed, the width of the second negative electrode layer 320 and the width of the positive electrode layer 400 are the same. Therefore, the edges of the first negative electrode layer 310 are not pressed during the pressing process. However, the thickness of the first negative electrode layer 310 before pressing is thinner than the combined thickness of the first negative electrode layer 310 and the second negative electrode layer 320 before pressing. Therefore, the thickness of the edge of the first negative electrode layer 310 after the pressing process is thinner than or equal to the thickness of the pressed first negative electrode layer 310 and second negative electrode layer 320, even if they are not pressed during the pressing process. This prevents the edge of the negative electrode layer 300 from becoming thicker than the pressed portion of the negative electrode layer 300 due to the pressing process, and prevents the formation of a step at the edge of the negative electrode layer 300. As a result, the pre-pressing process can be eliminated, and the number of processes can be reduced. Thus, a method for manufacturing electrodes with a further reduction in the number of processes can be provided.

[0026] Furthermore, since the negative electrode layer is composed of two layers, a first negative electrode layer 310 and a second negative electrode layer 320, it is possible to prevent the negative electrode layer from peeling off from the current collector foil 200 due to high-speed drying in the drying process. In addition, since the negative electrode layer is composed of two 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, thereby lowering manufacturing costs.

[0027] Furthermore, the amount of binder contained in the first negative electrode material, which forms the first negative electrode layer 310, is less than the amount of binder contained in the second negative electrode material, which forms the second negative electrode layer 320. This reduces the total amount of binder in the negative electrode layer, which acts as resistance in the battery. Therefore, it is possible to optimize the amount of binder that acts as resistance in the battery.

[0028] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0029] 110 Slurry supply device 120 Coating Section 121 First die coater 122 Second die coater 130 Backup Roles 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. By coating one side of the current collector foil with a negative electrode material, a first negative electrode layer is formed on the said one side, 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. By coating the other surface of the current collector foil with a positive electrode material, a positive electrode layer is formed on the other surface. The positive electrode layer is dried, The first negative electrode layer, the second negative electrode layer, and the positive electrode layer are pressed together. When pressing the first negative electrode layer, the second negative electrode layer, and the positive electrode layer, the width of the second negative electrode layer and the width of the positive electrode layer are the same. A method for manufacturing electrodes.

2. The thickness of the first negative electrode layer before pressing is less than or equal to the thickness of the pressed first negative electrode layer and the second negative electrode layer. A method for manufacturing an electrode according to claim 1.

3. 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. A method for manufacturing an electrode according to claim 1 or 2.

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