Manufacturing method of the electrode body

Abstract

To provide a manufacturing method of an electrode body capable of preventing wrinkles from forming on uncoated areas of the electrode material.SOLUTION: In a manufacturing method of an electrode body, before or after press work for pressing an electrode material in an electrode material coating area (A), work to equalize an elongation rate is performed in order to equalize an elongation rate of an entire sheet-like electrode body (1) to stretch a pair of electrode material uncoated areas (B) in the longitudinal direction. The work to equalize the elongation rate is carried out by causing the electrode body sheet (1) to pass through rotating rolls (20, 21) arranged in parallel therebetween for pressing the cylindrical elastic outer peripheral surfaces of the rolls (20, 21) against the sheet-shaped electrode body (1), a cylindrical elastic outer peripheral surface portion that is pressed against a width direction edge (10) of the electrode material coating unit (A) during elongation rate uniformization work is formed of an elastic body with a low Young's modulus compared to the cylindrical elastic outer peripheral surface that is pressed against the electrode material uncoated area (B).SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] An electrode body manufacturing apparatus for manufacturing a sheet-shaped electrode body for a lithium ion battery is known, which has, on a strip-shaped metal foil, an electrode material-coated portion of uniform width extending in the longitudinal direction of the metal foil and an electrode material-uncoated portion extending in the longitudinal direction of the metal foil on both sides of the electrode material-coated portion (see, for example, Patent Document 1). When manufacturing such a sheet-shaped electrode body, a press operation is indispensable for the electrode material of the electrode material-coated portion in order to increase the density of lithium in the electrode material of the electrode material-coated portion. However, when such a press operation is performed, the electrode material-coated portion is stretched in the longitudinal direction by the press force, while the electrode material-uncoated portion is not stretched because no press force acts on it. As a result, wrinkles are generated in the electrode material-uncoated portion due to the difference in elongation rate. These wrinkles are an obstacle to the manufacture of batteries, and therefore need to be removed. Therefore, in the above-mentioned electrode body manufacturing apparatus, the sheet-shaped electrode body is inserted between a pair of hard rolls, and the uncoated parts of the electrode material are compressed and stretched by these hard rolls, thereby preventing the occurrence of wrinkles in the uncoated parts of the electrode material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-102172 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the electrode material uncoated portion is compressed by the hard roll in this manner to stretch the electrode material uncoated portion, the electrode material uncoated portion breaks. That is, in this case, the hard roll and the electrode material uncoated portion are in contact with each other at a linear contact portion, and the thickness of the electrode material uncoated portion is reduced by a pressure force applied in the thickness direction of the electrode material uncoated portion at this linear contact portion, and the electrode material uncoated portion is stretched by an expansion action in the longitudinal direction of the sheet-like electrode body due to the reduced thickness. However, in order to stretch the electrode material uncoated portion by this method, it is necessary to locally apply an extremely strong pressure force to the linear contact portion, and as a result, when the electrode material uncoated portion is stretched, the electrode material uncoated portion breaks. [Means for solving the problem]

[0005] In order to solve such problems, the present invention provides a method for producing an electrode body for producing a sheet-like electrode body having, on a band-like extending metal foil, an electrode material-coated portion of uniform width extending in the longitudinal direction of the metal foil and electrode material-uncoated portions on both sides of the electrode material-coated portion extending in the longitudinal direction of the metal foil, in which an elongation rate equalization operation is performed before or after a pressing operation for pressing the electrode material in the electrode material-coated portion to stretch the electrode material-uncoated portion in the longitudinal direction to equalize the elongation rate of the entire sheet-like electrode body, the elongation rate equalization operation is performed by passing the sheet-like electrode body between rotating rolls arranged in parallel to press the cylindrical elastic outer peripheral surface of each roll onto the sheet-like electrode body, and the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge of the electrode material-coated portion during the elongation rate equalization operation is formed from an elastic body having a lower Young's modulus than the cylindrical elastic outer peripheral surface portion pressed against the electrode material-uncoated portion. Effect of the Invention

[0006] It is possible to stretch the uncoated portion of the electrode material without breaking the uncoated portion of the electrode material, thereby preventing the occurrence of wrinkles in the uncoated portion of the electrode material. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a part of an electrode assembly manufacturing apparatus. [Diagram 2] FIG. 2 is a diagram for explaining an example of a sheet-shaped electrode body. [Diagram 3] FIG. 3 is a diagram for explaining the elongation rate of the sheet-shaped electrode body due to a pressing operation. [Figure 4] FIG. 4 is a diagram for explaining the elongation equalization operation by the elongation equalization method which is the premise of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining the stretching action of the sheet electrode. [Figure 6] FIG. 6 is a diagram for explaining the elongation equalization operation by the elongation equalization method according to the present invention. [Figure 7] FIG. 7 is a diagram showing the elongation rate of the sheet-shaped electrode body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] FIG. 1 is a schematic diagram of a part of an electrode assembly manufacturing apparatus. Referring to FIG. 1, 1 denotes a sheet-shaped electrode assembly, 2 denotes a press device having a pair of cylindrical metal press rolls 2a and 2b arranged in parallel and rotated in opposite directions, 3 denotes an elongation rate equalizing device for equalizing the elongation rate of the entire sheet-shaped electrode assembly 1, 4 denotes a tensioning device for applying tension to the sheet-shaped electrode assembly 1, and 5 denotes a winding roll for the sheet-shaped electrode assembly 1 before processing that is wound in a roll shape. As shown in FIG. 1, the sheet-shaped electrode assembly 1 wound around the winding roll 5 passes through a tensioning device 4, an elongation rate equalizing device 3, and a press device 2 in this order, and is continuously transported in the direction of the arrow. In the example shown in FIG. 1, tension is applied by the tensioning device 4 to the sheet-shaped electrode assembly 1 passing through the elongation rate equalizing device 3.

[0009] Fig. 2(A) shows a plan view of a portion of the sheet-type electrode body 1, and Fig. 2(B) shows a cross-sectional view of the sheet-type electrode body 1 taken along line XX in Fig. 2(A). The sheet-type electrode body 1 extends vertically in a strip shape in Fig. 2(A) and is conveyed in the direction of the arrow in Fig. 2(A). As shown in Fig. 2(A) and Fig. 2(B), in the example shown in Fig. 2(A) and Fig. 2(B), the sheet-type electrode body 1 is composed of a metal foil 6 extending in a strip shape and electrode material layers 7 and 8 applied on both sides of the metal foil 6.

[0010] In the following, in the embodiments of the present invention, a portion of the sheet-like electrode body 1 on which the electrode material is applied, i.e., a portion of the sheet-like electrode body 1 on which the electrode material layers 7, 8 are formed, will be referred to as an electrode material coated portion A or simply as a coated portion A, and a portion of the sheet-like electrode body 1 on which the electrode material is not applied, i.e., a portion of the sheet-like electrode body 1 on which the electrode material layers 7, 8 are not formed, will be referred to as an electrode material uncoated portion B or simply as an uncoated portion B. With these designations, in the example shown in Figures 2(A) and 2(B), the sheet-like electrode body 1 has an electrode material coated portion A of uniform width extending in the longitudinal direction of the metal foil 6, and electrode material uncoated portions B extending in the longitudinal direction of the metal foil 6 on both sides of the electrode material coated portion A.

[0011] The sheet-shaped electrode body 1 may be, for example, a sheet-shaped electrode body for a positive electrode of a lithium ion secondary battery using an electrolyte solution, or may be a sheet-shaped electrode body for a negative electrode. Also, it may be a sheet-shaped electrode body for a positive electrode of an all-solid-state lithium ion secondary battery, or may be a sheet-shaped electrode body for a negative electrode. When the sheet-shaped electrode body 1 is a sheet-shaped electrode body for a positive electrode, the metal foil 6 is formed, for example, from an aluminum foil extending in a strip shape, and the electrode material layers 7 and 8 are formed from a positive electrode active material such as LiCoO2 or LiMnO2 that can absorb lithium ions during discharge and release them during charging. On the other hand, when the sheet-shaped electrode body 1 is a sheet-shaped electrode body for a negative electrode, the metal foil 6 is formed, for example, from a copper foil extending in a strip shape, and the electrode material layers 7 and 8 are formed from a negative electrode active material such as carbon that can release lithium ions during discharge and absorb them during charging.

[0012] On the other hand, FIG. 2C shows an example in which the widthwise end faces of the electrode material-coated portion A are covered with a protective layer 9. This protective layer 9 is made of, for example, alumina, and serves to prevent the widthwise end faces of the electrode material-coated portion A from contacting other surrounding members and damaging them. This protective layer 9 is formed as necessary. The thickness of the metal foil 6 shown in FIGS. 2A to 2C is about 10 μm to 100 μm, and the thickness of the electrode material layers 7 and 8, i.e., the thickness of the electrode material-coated portion A, is about 0.5 mm to 1.5 mm. Therefore, in FIGS. 2B and 2C, the thickness of the metal foil 6 is particularly shown significantly exaggerated.

[0013] 2A to 2C show an example in which the metal foil 6 has an electrode material coated portion A on both sides thereof, but the present invention is also applicable to a case in which the metal foil 6 has an electrode material coated portion A on only one side thereof, and also to a case in which the metal foil 6 has a plurality of electrode material coated portions A formed at intervals on both sides or on one side thereof. In FIG. 1, when the electrode material is applied to the metal foil 6 between the winding roll 5 and the elongation equalizing device 3, the metal foil 6 that does not have the electrode material coated portion A is wound around the winding roll 5. In FIG. 1, the elongation equalizing device 3 and the tension applying device 4 can also be arranged in this order downstream of the press device 2 as viewed in the conveying direction of the sheet-like electrode body 1.

[0014] Now, when manufacturing the sheet-shaped electrode body 1, it is essential to perform a strong pressing operation on the electrode material of the electrode material-coated part A in order to increase the density of lithium in the electrode material of the electrode material-coated part A and to make the thickness of the electrode material-coated part A a predetermined thickness. FIG. 3 shows diagrammatically the pressing operation on the electrode material of the electrode material-coated part A performed by the pressing device 2 and the longitudinal elongation rate of the sheet-shaped electrode body 1 stretched by this pressing operation. Also, in FIG. 3, the magnitude of the longitudinal elongation rate of the sheet-shaped electrode body 1 is indicated by an arrow. Note that FIG. 3 shows a case where the sheet-shaped electrode body 1 having the cross-sectional shape shown in FIG. 2(B) is pressed by cylindrical metal press rolls 2a and 2b of the pressing device 2.

[0015] Since the uncoated portion B of the sheet-shaped electrode body 1 is thinner than the coated portion A, when the sheet-shaped electrode body 1 is pressed by the press device 2 as shown in FIG. 3, the uncoated portion B is not pressed by the cylindrical metal press rolls 2a and 2b, and only the coated portion A is pressed by the cylindrical metal press rolls 2a and 2b. Therefore, at this time, the coated portion A is stretched by the pressing action of the cylindrical metal press rolls 2a and 2b. On the other hand, no external force acts on the uncoated portion B to stretch it. As a result, when the sheet-shaped electrode body 1 is pressed by the press device 2, as shown in FIG. 3, the longitudinal elongation rate of the coated portion A is uniformly large, and the longitudinal elongation rate of the uncoated portion B is almost zero.

[0016] On the other hand, the widthwise edge portions 10 of the coated portion A have a lower density of the electrode material than the central portion of the coated portion A, and are more easily deformed in the width direction, and therefore have lower rigidity than the central portion of the coated portion A. Therefore, when the sheet-like electrode body 1 is subjected to the pressing action of the cylindrical metal press rolls 2a, 2b, the force with which the widthwise edge portions 10 of the coated portion A press against the metal foil 6 is weaker than the force with which the central portion of the coated portion A presses against the metal foil 6, and as a result, the longitudinal elongation rate of the widthwise edge portions 10 of the coated portion A becomes considerably smaller, as shown by the arrows in FIG.

[0017] When the longitudinal elongation rate of the coated portion A becomes large and the longitudinal elongation rate of the uncoated portion B becomes almost zero, only the coated portion A side of the uncoated portion B is forcibly stretched, resulting in the occurrence of wrinkles in the uncoated portion B. Since these wrinkles are an obstacle to the manufacture of batteries, it is necessary to prevent the occurrence of such wrinkles. In order to prevent the occurrence of such wrinkles, it is sufficient to stretch the uncoated portion B so that the longitudinal elongation rate of the uncoated portion B becomes the same as the longitudinal elongation rate of the coated portion A. In this case, in order to prevent the occurrence of wrinkles in the uncoated portion B, it is also necessary to stretch the widthwise edge portion 10 of the coated portion A so that the longitudinal elongation rate of the widthwise edge portion 10 of the coated portion A becomes the same as the longitudinal elongation rate of the coated portion A.

[0018] In order to prevent wrinkles from occurring in the uncoated portion B, it is necessary to stretch the uncoated portion B and the widthwise edge portion 10 of the coated portion A so that the longitudinal elongation rate of the uncoated portion B and the longitudinal elongation rate of the widthwise edge portion 10 of the coated portion A are the same as the longitudinal elongation rate of the coated portion A. For this purpose, in an embodiment of the present invention, an elongation rate equalizing device 3 is disposed upstream of the press device 2 as viewed from the conveyance direction of the sheet-like electrode body 1. In FIG. 3, the regions of the uncoated portion B and the widthwise edge portion 10 of the coated portion A that need to be stretched by the elongation rate equalizing device 3 are indicated by R.

[0019] In this case, a method of stretching the uncoated portion B etc. can be considered by compressing the uncoated portion B etc. with a cylindrical metal roll to stretch the uncoated portion B etc. However, this method has the problem of breaking the uncoated portion B. That is, in this method, the cylindrical metal roll and the uncoated portion B etc. are brought into contact at a linear contact portion, and the thickness of the uncoated portion B etc. is reduced by the pressure applied in the thickness direction of the uncoated portion B etc. at this linear contact portion, and the uncoated portion B etc. is stretched by the expansion action in the longitudinal direction of the sheet-like electrode body due to the reduction in thickness. However, in order to stretch the uncoated portion B etc. by this method, it is necessary to locally apply an extremely strong pressure force to the linear contact portion, and as a result, a problem occurs in that the uncoated portion B etc. breaks when an attempt is made to stretch the uncoated portion B etc.

[0020] Therefore, the inventors of the present invention have begun to develop a new method for equalizing elongation percentage, in which a roll made of an elastic material is used instead of the cylindrical metal roll, and the widthwise edge portion 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1 is stretched by the roll. The present invention is based on this method for equalizing elongation percentage, and therefore, the method for equalizing elongation percentage, which is the premise of the present invention, will be described first. FIG. 4 shows diagrammatically the operation for equalizing elongation percentage by the method for equalizing elongation percentage and the longitudinal elongation percentage of the sheet-like electrode body 1 stretched by the operation for equalizing elongation percentage. Also, in FIG. 4, the magnitude of the longitudinal elongation percentage of the sheet-like electrode body 1 is indicated by an arrow.

[0021] 4, the elongation rate equalizing device 3 in this elongation rate equalizing method uses a lower roll 20 and an upper roll 21 that are arranged in parallel and rotate, the lower roll 20 being formed of a cylindrical elastic body having a cylindrical elastic outer peripheral surface of the same diameter over its entire length, and the upper roll 21 being formed of an integrally molded elastic body having large-diameter cylindrical elastic outer peripheral surfaces 24a, 24b and a small-diameter cylindrical elastic outer peripheral surface 25 that are arranged at a distance from each other. The lower roll 20 is supported by a rotating shaft 22, and the cylindrical elastic outer peripheral surface of the lower roll 20 extends outward beyond both ends of the sheet-like electrode body 1 in the width direction. On the other hand, the upper roll 21 is supported by a rotating shaft 23.

[0022] In this elongation rate equalizing device 3, the lower roll 20 is rotationally driven by a driving device (not shown), and the upper roll 21 is pressed toward the lower roll 20 by a pressure device (not shown). Meanwhile, as shown in FIG. 4, the large-diameter cylindrical elastic outer peripheral surfaces 24a, 24b of the upper roll 21 are formed in a region R facing the widthwise edge portions 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1. Therefore, when the sheet-like electrode body 1 is transported between the upper roll 21 and the lower roll 20, the widthwise edge portions 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1 are subjected to a pressure action between the large-diameter cylindrical elastic outer peripheral surfaces 24a, 24b of the upper roll 21 and the cylindrical elastic outer peripheral surface of the lower roll 20, and at this time, the widthwise edge portions 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1 are stretched.

[0023] Fig. 5 shows the stretching mechanism diagrammatically. Fig. 5(A) shows an enlarged view of the contact area between the upper roll 21 and the lower roll 20 and the uncoated part B of the sheet-like electrode body 1, i.e., the metal foil 6, and the parts P1 and P2 surrounded by dashed lines in Fig. 5(B) and (C) show enlarged views of the elastic part P1 of the upper roll 21 pressed onto the metal foil 6 and the elastic part P2 of the lower roll 20 pressed onto the metal foil 6, respectively, shown in Fig. 5(A). If the upper roll 21 and the lower roll 20 are made of an elastic body such as rubber, when the upper roll 21 and the lower roll 20 are pressed onto the metal foil 6, the elastic part P1 and the elastic part P2 expand in the longitudinal direction of the sheet-like electrode body 1 as shown by the dashed lines Q1 and Q2.

[0024] As a result, the contact surface of the elastic portion P1 with the metal foil 6 and the contact surface of the elastic portion P2 with the metal foil 6 expand to the positions indicated by the dashed lines Q1 and Q2, and a stretching force that stretches the metal foil 6 in the longitudinal direction is applied to the metal foil 6 by the upper roll 21 and the lower roll 20. At this time, the metal foil 6 is stretched in the longitudinal direction of the sheet-like electrode body 1 by this stretching force acting on the metal foil 6. When the metal foil 6 is stretched in this manner by the stretching force acting on the metal foil 6, it is not necessary to locally apply an extremely strong pressure force to the linear contact portion with the metal foil 6 as in the case of using a cylindrical metal roll, and therefore it is possible to stretch the metal foil 6 in the longitudinal direction of the sheet-like electrode body 1 without breaking the metal foil 6. At this time, a similar stretching force is applied to the widthwise edge 10 of the coated portion A by the upper roll 21 and the lower roll 20, and this stretching force causes the widthwise edge 10 of the coated portion A to be stretched in the longitudinal direction of the sheet-like electrode body 1.

[0025] The magnitude of the longitudinal elongation rate of the sheet-like electrode body 1 at this time is indicated by an arrow in Fig. 4, and it can be seen from Fig. 4 that the uncoated part B is stretched uniformly over the entirety at this time. The pressure applied by the upper roll 21 to the lower roll 20 by the pressurizing device at this time is set so that the elongation rate of the uncoated part B at this time is equal to the elongation rate of the coated part A by the press device 2 shown in Fig. 3. On the other hand, since the electrode material is applied to the widthwise edge 10 of the coated part A, the rigidity of the widthwise edge 10 of the coated part A is considerably higher than the rigidity of the uncoated part B. Therefore, as indicated by the arrow in Fig. 4, although the widthwise edge 10 of the coated part A is stretched, the elongation rate of the widthwise edge 10 of the coated part A is considerably smaller than the elongation rate of the uncoated part B.

[0026] Therefore, even if the elongation rate of the width direction edge 10 of the coated part A by the press device 2 shown in Fig. 3 is added to the elongation rate of the width direction edge 10 of the coated part A by the elongation rate equalizing device 3 shown in Fig. 4, it does not become large enough to be the same as the elongation rate of the coated part A by the press device 2 shown in Fig. 3 and the elongation rate of the uncoated part B by the elongation rate equalizing device 3 shown in Fig. 4, and therefore the longitudinal elongation rate of the entire sheet-like electrode body 1 cannot be sufficiently uniformed. In this case, in order to uniform the longitudinal elongation rate of the entire sheet-like electrode body 1, it is necessary to increase the elongation rate of the width direction edge 10 of the coated part A, and for this purpose, in the elongation rate equalizing device 3, the stretching force acting on the width direction edge 10 of the coated part A by the upper roll 21 and the lower roll 20 needs to be larger than the stretching force acting on the width direction edge 10 of the uncoated part B.

[0027] In this case, if the upper roll 21 and the lower roll 20 portions pressed against the widthwise edge 10 of the coated part A are made of an elastic body with a low Young's modulus, i.e., an elastic body with low rigidity, the stretching force acting on the widthwise edge 10 of the coated part A can be increased. That is, if the upper roll 21 and the lower roll 20 portions pressed against the widthwise edge 10 of the coated part A are made of an elastic body with a low Young's modulus, the amount of expansion of the elastic body parts P1 and P2 when the upper roll 21 and the lower roll 20 are pressed against the metal foil 6 becomes larger as shown by the chain lines Q1 and Q2 in Fig. 5C compared to the case shown in Fig. 5B. As a result, the contact surface of the elastic body parts P1 and P2 with the metal foil 6 is greatly expanded compared to the case shown in Fig. 5B, so that the stretching force acting on the metal foil 6 to stretch the metal foil 6 in the longitudinal direction increases.

[0028] Therefore, in an embodiment of the present invention, the upper roll 21 and lower roll 20 portions that are pressed against the widthwise edge 10 of the coated portion A are made of an elastic material with a low Young's modulus, and one example of this embodiment of the present invention is shown in Figure 6. Note that Figure 6 diagrammatically shows the elongation equalization operation by an elongation equalization device 3, which illustrates one embodiment of the present invention, and the longitudinal elongation of the sheet-like electrode body 1 stretched by this elongation equalization operation. Also in Figure 6, the magnitude of the longitudinal elongation of the sheet-like electrode body 1 is indicated by an arrow.

[0029] As can be seen from Fig. 6, the elongation rate equalizing device 3 showing one embodiment of the present invention has an overall configuration similar to that of the elongation rate equalizing device 3 shown in Fig. 4, and in Fig. 6, components similar to those shown in Fig. 4 are given the same reference numerals. Referring to Fig. 6, the elongation rate equalizing device 3 showing one embodiment of the present invention also uses a lower roll 20 and an upper roll 21 arranged in parallel to each other, as in Fig. 4. As shown in Fig. 6, the lower roll 20 is formed of a cylindrical elastic body having a cylindrical elastic outer circumferential surface of the same diameter over its entire length, and the lower roll 20 is composed of a pair of cylindrical elastic body parts 20a, 20b located in a region R facing the uncoated portion B and the width direction edge portion 10 of the coated portion A of the sheet-like electrode body 1, and a cylindrical elastic body part 20c located between the pair of cylindrical elastic body parts 20a, 20b. Each of the cylindrical elastic portions 20a, 20b is bonded to both ends of the cylindrical elastic portion 20c by baking, and these cylindrical elastic portions 20a, 20b and the cylindrical elastic portion 20c are supported by a rotating shaft 22.

[0030] On the other hand, the upper roll 21 has a cylindrical elastic outer peripheral surface and is composed of a pair of cylindrical elastic bodies 21a, 21b arranged at a distance from each other so as to be located in a region R facing the uncoated portion B and the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1. One of the cylindrical elastic bodies 21a is composed of a cylindrical elastic body portion 21c arranged at a position facing the uncoated portion B of the sheet-like electrode body 1 and a cylindrical elastic body portion 21d arranged at a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1, and these cylindrical elastic body portions 21c and 21d are bonded together by baking. The other cylindrical elastic body 21b also consists of a cylindrical elastic body portion 21e arranged in a position facing the uncoated portion B of the sheet-like electrode body 1, and a cylindrical elastic body portion 21f arranged in a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1, and these cylindrical elastic body portions 21e and 21f are bonded together by baking.

[0031] As shown in Fig. 6, cylindrical elastic body 21a and cylindrical elastic body 21b are supported by a rotating shaft 23. In the example shown in Fig. 6, no elastic body is provided between cylindrical elastic body 21a and cylindrical elastic body 21b, but cylindrical elastic body portion 21d and cylindrical elastic body portion 21f may be integrally structured in such a way that they are connected to each other by a small-diameter elastic body. In the example shown in Figure 6, cylindrical elastic body portion 20c arranged on the lower roll 20 at a position facing the widthwise edge portion 10 of coated portion A of the sheet-like electrode body 1, and cylindrical elastic body portion 21d and cylindrical elastic body portion 21f arranged on the upper roll 21 at a position facing the widthwise edge portion 10 of coated portion A of the sheet-like electrode body 1 are formed from an elastic body having a lower Young's modulus than cylindrical elastic body portion 21a and cylindrical elastic body portion 21b arranged on the lower roll 20 at a position facing uncoated portion B of the sheet-like electrode body 1, and cylindrical elastic body portion 21c and cylindrical elastic body portion 21e arranged on the upper roll 21 so as to face uncoated portion B of the sheet-like electrode body 1.

[0032] 6, the cylindrical elastic portions 20a, 20b, 20c, 21c, 21d, 21e, and 20f are made of rubber. Of course, the cylindrical elastic portions 20a, 20b, 20c, 21c, 21d, 21e, and 20f can also be made of a resin material such as urethane. In one embodiment of the present invention, the cylindrical elastic body portion 20c arranged on the lower roll 20 at a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1, and the cylindrical elastic body portion 21d and the cylindrical elastic body portion 21f arranged on the upper roll 21 so as to face the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1 are formed from rubber having a Young's modulus when compressed in the range of 12 MPa to 18 MPa, and the cylindrical elastic body portion 20a and the cylindrical elastic body portion 20b arranged on the lower roll 20 at a position facing the uncoated portion B of the sheet-like electrode body 1, and the cylindrical elastic body portion 21c and the cylindrical elastic body portion 21e arranged on the upper roll 21 so as to face the uncoated portion B of the sheet-like electrode body 1 are formed from rubber having a Young's modulus when compressed in the range of 20 MPa to 26 MPa.

[0033] Incidentally, in the example shown in FIG. 6, the cylindrical elastic body portion 20c arranged on the lower roll 20 at a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1, and the cylindrical elastic body portion 21d and the cylindrical elastic body portion 21f arranged on the upper roll 21 at a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1 are formed from rubber having a Young's modulus of 15 MPa when compressed, and the cylindrical elastic body portion 20a and the cylindrical elastic body portion 20b arranged on the lower roll 20 at a position facing the uncoated portion B of the sheet-like electrode body 1, and the cylindrical elastic body portion 21c and the cylindrical elastic body portion 21e arranged on the upper roll 21 at a position facing the uncoated portion B of the sheet-like electrode body 1 are formed from rubber having a Young's modulus of 23 MPa when compressed.

[0034] 6, the upper roll 21 is also pressed toward the lower roll 20 by a pressure device (not shown). When the sheet-like electrode body 1 is transported between the upper roll 21 and the lower roll 20, on the one hand, the uncoated portion B of the sheet-like electrode body 1 is subjected to a pressure action between the cylindrical elastic outer peripheral surface of the cylindrical elastic body portions 20a, 20b, which have a large Young's modulus, of the lower roll 20, and the cylindrical elastic outer peripheral surface of the cylindrical elastic body portions 21c, 21e, which have a large Young's modulus, of the upper roll 21. On the other hand, the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1 is subjected to a pressure action between the cylindrical elastic outer peripheral surface of the cylindrical elastic body portion 20c, which has a small Young's modulus, of the lower roll 20, and the cylindrical elastic outer peripheral surface of the cylindrical elastic body portions 21d, 21f, which have a small Young's modulus, of the upper roll 21. As a result, the uncoated portion B and the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1 are stretched.

[0035] Therefore, in the elongation equalizing device 3, the widthwise edge 10 of the coated portion A of the sheet-like electrode body 1 is subjected to a larger elongation force by the upper roll 21 and the lower roll 20 than the uncoated portion B of the sheet-like electrode body 1. As a result, as shown in Fig. 6, the elongation of the widthwise edge 10 of the coated portion A of the sheet-like electrode body 1 is larger than that shown in Fig. 4.

[0036] 7 shows experimental results of the elongation in the coated portion A, the widthwise edge portion 10 of the coated portion A, and the uncoated portion B of the sheet-shaped electrode body 1 when the elongation equalization operation is performed by the elongation equalization device 3. In FIG. 7, the dashed line shows the elongation when the elongation equalization operation is performed by the elongation equalization device 3, which is the premise of the present invention shown in FIG. 4, in a state where the sheet-shaped electrode body 1 is not tensioned by the tensioning device 4, the chain line shows the elongation when the elongation equalization operation is performed by the elongation equalization device 3, which is the premise of the present invention shown in FIG. 4, in a state where the sheet-shaped electrode body 1 is tensioned by the tensioning device 4, and the solid line shows the elongation when the elongation equalization operation is performed by the elongation equalization device 3 according to the present invention shown in FIG. 6, in a state where the sheet-shaped electrode body 1 is tensioned by the tensioning device 4.

[0037] As can be seen from Fig. 7, when the elongation rate equalizing operation is performed by the elongation rate equalizing device 3 according to the present invention shown in Fig. 6, the elongation rate of the widthwise edge portion 10 of the coated portion A of the sheet-shaped electrode body 1 can be significantly increased compared to when the elongation rate equalizing operation is performed by the elongation rate equalizing device 3 which is the premise of the present invention shown in Fig. 4. As a result, when the press device 2 presses the coated portion A of the sheet-shaped electrode body 1, and the coated portion A of the sheet-shaped electrode body 1 is stretched in the longitudinal direction of the sheet-shaped electrode body 1, the longitudinal elongation rate of the sheet-shaped electrode body 1 becomes uniform over the entire width of the sheet-shaped electrode body 1. As a result, it is possible to prevent wrinkles from occurring in the uncoated portion B.

[0038] Thus, in an embodiment of the present invention, in a method for producing an electrode body for producing a sheet-like electrode body 1 having, on a band-like extending metal foil 6, an electrode material-coated portion A of uniform width extending in the longitudinal direction of the metal foil 6 and an electrode material-uncoated portion B extending in the longitudinal direction of the metal foil 6 on both sides of the electrode material-coated portion A, an elongation rate equalization operation is performed before or after a pressing operation for pressing the electrode material of the electrode material-coated portion A, in which the electrode material-uncoated portion B is stretched in the longitudinal direction to equalize the elongation rate of the entire sheet-like electrode body 1. This elongation rate equalization operation is performed by passing the sheet-like electrode body 1 between rotating rolls 20, 21 arranged in parallel to each other to press the cylindrical elastic outer peripheral surface of each roll 20, 21 onto the sheet-like electrode body 1, and the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge portion 10 of the electrode material-coated portion A during this elongation rate equalization operation is formed from an elastic body having a lower Young's modulus than the cylindrical elastic outer peripheral surface portion pressed against the electrode material-uncoated portion B.

[0039] In this case, in an embodiment of the present invention, the elongation rate equalization operation is performed in a state where a tension in the longitudinal direction is applied to the sheet-like electrode body 1. In an embodiment of the present invention, the elastic body is made of rubber, and the Young's modulus of the rubber forming the cylindrical elastic outer peripheral surface portion pressed against the electrode material uncoated portion B is within a range of 20 MPa to 26 MPa when compressed, and the Young's modulus of the rubber forming the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge portion 10 of the electrode material coated portion A is within a range of 12 MPa to 18 MPa when compressed. In an embodiment of the present invention, the cylindrical elastic outer peripheral surface of one roll 21 is pressed against the sheet-like electrode body 1 only at the electrode material uncoated portion B and the widthwise edge portion 10 of the electrode material coated portion A, and the cylindrical elastic outer peripheral surface of the other roll 20 is pressed against the sheet-like electrode body 1 over the entire electrode material coated portion A including the electrode material uncoated portion B and the widthwise edge portion 10 of the electrode material coated portion A.

[0040] In one embodiment of the present invention, a protective layer 9 is formed on the metal foil 6 to cover the widthwise end faces of the electrode material-coated portions A, and during the elongation equalization operation, a portion of the cylindrical elastic outer peripheral surface of each of the rolls 20, 21 is pressed against the widthwise edge portions 10 and the protective layer 9 of the electrode material-coated portions A, and another portion of the cylindrical elastic outer peripheral surface of each of the rolls 20, 21 is pressed against the electrode material-uncoated portions B. In this case, in this embodiment, the cylindrical elastic outer peripheral surface portion that is pressed against the widthwise edge portions 10 and the protective layer 9 of the electrode material-coated portions A during the elongation equalization operation is formed from an elastic body having a lower Young's modulus than the cylindrical elastic outer peripheral surface portion that is pressed against the electrode material-uncoated portions B. [Explanation of symbols]

[0041] 1. Sheet-shaped electrode body 2 Press equipment 3. Elongation equalization device 4 Tensioning device 6 Metal foil 7,8 Electrode material layer 10 Widthwise edge 20 Downward Roll 21 Upper Roll A Electrode Material Coating Department B Electrode material uncoated area

Claims

1. A manufacturing method for an electrode body for manufacturing a sheet-like electrode body having, on a band-like extending metal foil, an electrode material-coated portion of uniform width extending in the longitudinal direction of the metal foil, and electrode material-uncoated portions on both sides of the electrode material-coated portion extending in the longitudinal direction of the metal foil, wherein an elongation rate equalization operation is performed before or after a pressing operation for pressing the electrode material in the electrode material-coated portion to stretch the electrode material-uncoated portions in the longitudinal direction to equalize the elongation rate of the entire sheet-like electrode body, the elongation rate equalization operation being performed by passing the sheet-like electrode body between rotating rolls arranged in parallel to press the cylindrical elastic outer peripheral surface of each roll onto the sheet-like electrode body, and the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge of the electrode material-coated portion during the elongation rate equalization operation is formed from an elastic body having a lower Young's modulus than the cylindrical elastic outer peripheral surface portion pressed against the electrode material-uncoated portions.

2. The method for manufacturing an electrode assembly according to claim 1 , wherein the elongation uniforming step is performed while applying tension in the longitudinal direction to the sheet-like electrode assembly.

3. 2. The method for manufacturing an electrode body according to claim 1, wherein the elastic body is made of rubber, the Young's modulus of the rubber forming the cylindrical elastic outer peripheral surface portion that is pressed against the uncoated portion of the electrode material is within the range of 20 MPa to 26 MPa when compressed, and the Young's modulus of the rubber forming the cylindrical elastic outer peripheral surface portion that is pressed against the width-wise edge portion of the coated portion of the electrode material is within the range of 12 MPa to 18 MPa when compressed.

4. 2. A method for manufacturing an electrode body as described in claim 1, wherein the cylindrical elastic outer peripheral surface of one roll is pressed against the sheet-shaped electrode body only at the width-wise edges of the electrode material uncoated portion and the electrode material coated portion, and the cylindrical elastic outer peripheral surface of the other roll is pressed against the sheet-shaped electrode body over the entire electrode material coated portion including the electrode material uncoated portion and the width-wise edges of the electrode material coated portion.

5. A method for manufacturing an electrode body as described in claim 1, wherein a protective layer is formed on the metal foil to cover the widthwise end faces of the electrode material coated portion, and the cylindrical elastic outer peripheral surface portion that is pressed against the widthwise edge portion of the electrode material coated portion and the protective layer during the elongation equalization operation is formed from an elastic material having a lower Young's modulus than the cylindrical elastic outer peripheral surface portion that is pressed against the electrode material uncoated portion.

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