JP7639798B2 - Manufacturing method of the electrode body - Google Patents

Description

The present invention relates to a method for manufacturing an electrode body.

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, pressing the electrode material of the electrode material-coated portion is essential to increase the density of lithium in the electrode material of the electrode material-coated portion. However, when such pressing is performed, the electrode material-coated portion is stretched in the longitudinal direction by the pressing force, while the electrode material-uncoated portion is not stretched because no pressing 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 the battery, and therefore need to be removed. Therefore, in the electrode body manufacturing device described above, 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 to prevent wrinkles from occurring in the uncoated parts of the electrode material.

JP 2019-102172 A

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

In order to solve such problems, the present invention provides a method for producing a sheet-shaped electrode body having an electrode material coated portion of uniform width extending in the longitudinal direction of the metal foil on a band-shaped metal foil and electrode material uncoated portions extending in the longitudinal direction of the metal foil on both sides of the electrode material coated portion, 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 uniform the elongation rate of the entire sheet-shaped electrode body by stretching the electrode material uncoated portion in the longitudinal direction, and the elongation rate equalization operation is performed by passing the sheet-shaped electrode body between rotating rolls arranged in parallel and pressing the cylindrical elastic outer peripheral surface of each roll onto the sheet-shaped 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.

It is possible to stretch the uncoated portions of the electrode material without breaking them, thereby preventing wrinkles from forming in the uncoated portions of the electrode material.

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

Figure 1 shows a schematic of a part of an electrode body manufacturing apparatus. Referring to Figure 1, 1 indicates a sheet-shaped electrode body, 2 indicates a press device equipped with a pair of cylindrical metal press rolls 2a and 2b arranged in parallel and rotated in opposite directions, 3 indicates an elongation rate equalizing device for equalizing the elongation rate of the entire sheet-shaped electrode body 1, 4 indicates a tensioning device for applying tension to the sheet-shaped electrode body 1, and 5 indicates a winding roll for the sheet-shaped electrode body 1 before processing, which is wound in a roll shape. As shown in Figure 1, the sheet-shaped electrode body 1 wound around the winding roll 5 passes through the tensioning device 4, the elongation rate equalizing device 3, and the press device 2 in order, and is continuously transported in the direction of the arrow. In the example shown in Figure 1, tension is applied to the sheet-shaped electrode body 1 passing through the elongation rate equalizing device 3 by the tensioning device 4.

Figure 2(A) shows a plan view of a portion of the sheet electrode body 1, and Figure 2(B) shows a cross-sectional view of the sheet electrode body 1 taken along line X-X in Figure 2(A). The sheet electrode body 1 extends vertically in a strip shape in Figure 2(A) and is transported in the direction of the arrow in Figure 2(A). As shown in Figures 2(A) and 2(B), in the example shown in Figures 2(A) and 2(B), the sheet electrode body 1 is composed of a metal foil 6 extending in a strip shape and electrode material layers 7 and 8 applied to both sides of the metal foil 6.

In the following, in the embodiments of the present invention, the portion of the sheet electrode body 1 on which the electrode material is applied, i.e., the portion of the sheet electrode body 1 on which the electrode material layers 7 and 8 are formed, is referred to as the electrode material coated portion A or simply the coated portion A, and the portion of the sheet electrode body 1 on which the electrode material is not applied, i.e., the portion of the sheet electrode body 1 on which the electrode material layers 7 and 8 are not formed, is referred to as the electrode material uncoated portion B or simply the uncoated portion B. In this way, in the example shown in Figures 2(A) and 2(B), the sheet electrode body 1 has 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.

The sheet-shaped electrode body 1 may be, for example, a positive electrode sheet-shaped electrode body of a lithium ion secondary battery using an electrolyte, or may be a negative electrode sheet-shaped electrode body. Also, it may be a positive electrode sheet-shaped electrode body of an all-solid-state lithium ion secondary battery, or may be a negative electrode sheet-shaped electrode body. When the sheet-shaped electrode body 1 is a positive electrode sheet-shaped electrode body, 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 LiCoO ₂ or LiMnO ₂ 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 negative electrode sheet-shaped electrode body, 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.

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 causing damage to those members. This protective layer 9 is formed as necessary. The thickness of the metal foil 6 shown in FIG. 2A to FIG. 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, the thickness of the metal foil 6 is shown considerably exaggerated in FIG. 2B and FIG. 2C.

2A to 2C show an example in which the metal foil 6 has an electrode material coating section A on both sides, but the present invention can also be applied to a case in which the metal foil 6 has an electrode material coating section A on only one side, or to a case in which the metal foil 6 has a plurality of electrode material coating sections A formed at intervals on both sides or on one side. In FIG. 1, when the electrode material is applied to the metal foil 6 between the winding roll 5 and the elongation rate equalizing device 3, the winding roll 5 is wound with a metal foil 6 that does not have an electrode material coating section A. In FIG. 1, the elongation rate equalizing device 3 and the tensioning device 4 can also be arranged in this order downstream of the press device 2 when viewed from the conveying direction of the sheet-shaped electrode body 1.

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

Because 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 increases uniformly, and the longitudinal elongation rate of the uncoated portion B becomes almost zero.

On the other hand, the widthwise edge 10 of the coated portion A has a lower density of the electrode material than the center of the coated portion A, and is more easily deformed in the width direction, so it has lower rigidity than the center of the coated portion A. Therefore, when the sheet-shaped electrode body 1 is subjected to the pressing action of the cylindrical metal press rolls 2a, 2b, the force with which the widthwise edge 10 of the coated portion A presses against the metal foil 6 is weaker than the force with which the center of the coated portion A presses against the metal foil 6, and as a result, the longitudinal elongation rate of the widthwise edge 10 of the coated portion A becomes considerably smaller, as shown by the arrow in Figure 3.

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 the battery, it is necessary to prevent the occurrence of such wrinkles. 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.

To prevent wrinkles from occurring in the uncoated portion B, it is necessary to stretch the widthwise edge 10 of the uncoated portion B and the coated portion A so that the longitudinal elongation rate of the uncoated portion B and the longitudinal elongation rate of the widthwise edge 10 of the coated portion A are the same as the longitudinal elongation rate of the coated portion A. For this reason, 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 conveying direction of the sheet-like electrode body 1. In FIG. 3, the regions of the widthwise edge 10 of the uncoated portion B and the coated portion A that need to be stretched by the elongation rate equalizing device 3 are indicated by R.

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 the uncoated portion B breaking. 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 apply an extremely strong pressure force locally to the linear contact portion, and as a result, the problem of the uncoated portion B breaking when trying to stretch the uncoated portion B etc. occurs.

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

Referring to FIG. 4, the elongation rate equalizing device 3 in this elongation rate equalizing method uses a lower roll 20 and an upper roll 21 that rotate in parallel, with the lower roll 20 being formed from 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 from 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 spaced apart 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. Meanwhile, the upper roll 21 is supported by a rotating shaft 23.

In this elongation rate equalizing device 3, the lower roll 20 is rotated by a driving device (not shown), and the upper roll 21 is pressed toward the lower roll 20 by a pressure device (not shown). On the other hand, as shown in FIG. 4, the large-diameter cylindrical elastic outer peripheral surfaces 24a, 24b of the upper roll 21 are formed in the region R facing the widthwise edge portion 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 portion 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1 is 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 portion 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1 is stretched.

Figure 5 shows the stretching mechanism diagrammatically. Note that (A) of Figure 5 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 (B) and (C) of Figure 5 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, as shown in (A) of Figure 5. If the upper roll 21 and the lower roll 20 are made of an elastic material 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.

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 way 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 also causes the widthwise edge 10 of the coated portion A to be stretched in the longitudinal direction of the sheet-like electrode body 1.

The magnitude of the longitudinal elongation rate of the sheet-shaped electrode body 1 at this time is indicated by the arrow in FIG. 4, and it can be seen from FIG. 4 that the uncoated part B is stretched uniformly over the entirety. 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 shown 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.

Therefore, even if the elongation rate of the widthwise edge 10 of the coated part A by the press device 2 shown in FIG. 3 is added to the elongation rate of the widthwise 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 widthwise edge 10 of the coated part A, and for this purpose, in the elongation rate equalizing device 3, the stretching force acting on the widthwise edge 10 of the coated part A by the upper roll 21 and the lower roll 20 must be larger than the stretching force acting on the widthwise edge 10 of the uncoated part B.

In this case, if the upper roll 21 and 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 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 than that shown in FIG. 5B, as shown by the dashed lines Q1 and Q2 in FIG. 5C. As a result, the contact surface of the elastic body parts P1 and P2 with the metal foil 6 is greatly expanded compared to that 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.

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

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 the 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 parts 20a, 20b is bonded to both ends of the cylindrical elastic part 20c by baking, and these cylindrical elastic parts 20a, 20b and cylindrical elastic part 20c are supported by a rotating shaft 22.

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 width direction 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.

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 can also be an integral structure connected to each other by a small-diameter elastic body. In the example shown in FIG. 6, the cylindrical elastic body portion 20c arranged in a position facing the widthwise edge portion 10 of the coated portion A of the sheet-like electrode body 1 on the lower roll 20, and the cylindrical elastic body portion 21d and the 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 on the upper roll 21 are made of an elastic body having a lower Young's modulus than the cylindrical elastic body portion 21a and the cylindrical elastic body portion 21b arranged in a position facing the uncoated portion B of the sheet-like electrode body 1 on the lower roll 20, and the cylindrical elastic body portion 21c and the cylindrical elastic body portion 21e arranged to face the uncoated portion B of the sheet-like electrode body 1 on the upper roll 21.

In the example shown in Fig. 6, each of the cylindrical elastic parts 20a, 20b, 20c, 21c, 21d, 21e, and 20f is made of rubber. Of course, each of the cylindrical elastic parts 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 portion 20c arranged in 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 portion 21d and the cylindrical elastic portion 21f arranged in 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 made of rubber having a Young's modulus in the range of 12 MPa to 18 MPa when compressed, and the cylindrical elastic portion 20a and the cylindrical elastic portion 20b arranged in the lower roll 20 so as to face the uncoated portion B of the sheet-like electrode body 1, and the cylindrical elastic portion 21c and the cylindrical elastic portion 21e arranged in the upper roll 21 so as to face the uncoated portion B of the sheet-like electrode body 1 are made of rubber having a Young's modulus in the range of 20 MPa to 26 MPa when compressed.

Incidentally, in the example shown in FIG. 6, the cylindrical elastic body portion 20c arranged in 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 in 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 made of 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 in 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 in the upper roll 21 at a position facing the uncoated portion B of the sheet-like electrode body 1 are made of rubber having a Young's modulus of 23 MPa when compressed.

In the example shown in FIG. 6, the upper roll 21 is pressed toward the lower roll 20 by a pressure device (not shown), and 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 surface of the cylindrical elastic body portion 20a, 20b having a large Young's modulus of the lower roll 20 and the cylindrical elastic outer surface of the cylindrical elastic body portion 21c, 21e having a large Young's modulus of the upper roll 21, and 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 surface of the cylindrical elastic body portion 20c having a small Young's modulus of the lower roll 20 and the cylindrical elastic outer surface of the cylindrical elastic body portion 21d, 21f having a small Young's modulus of the upper roll 21, thereby stretching the widthwise edge portion 10 of the uncoated portion B and the coated portion A of the sheet-like electrode body 1.

Therefore, in the elongation rate equalization device 3, the widthwise edge 10 of the coated portion A of the sheet-like electrode body 1 is subjected to a greater 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 Figure 6, the elongation rate of the widthwise edge 10 of the coated portion A of the sheet-like electrode body 1 is greater than that shown in Figure 4.

Figure 7 shows the experimental results of the elongation rate 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 rate equalization operation is performed by the elongation rate equalization device 3. In FIG. 7, the dashed line shows the elongation rate when the elongation rate equalization operation is performed by the elongation rate equalization device 3, which is the premise of the present invention shown in FIG. 4, without tension being applied to the sheet-shaped electrode body 1 by the tensioning device 4. The chain line shows the elongation rate when the elongation rate equalization operation is performed by the elongation rate equalization device 3, which is the premise of the present invention shown in FIG. 4, with tension being applied to the sheet-shaped electrode body 1 by the tensioning device 4. The solid line shows the elongation rate when the elongation rate equalization operation is performed by the elongation rate equalization device 3 according to the present invention shown in FIG. 6, with tension being applied to the sheet-shaped electrode body 1 by the tensioning device 4.

As can be seen from FIG. 7, when the elongation rate equalization operation is performed using the elongation rate equalization 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 equalization operation is performed using the elongation rate equalization device 3, which is the premise of the present invention shown in FIG. 4. As a result, when the coated portion A of the sheet-shaped electrode body 1 is pressed by the press device 2 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.

Thus, in an embodiment of the present invention, in a method for manufacturing an electrode body for manufacturing a sheet-like electrode body 1 having an electrode material coated portion A of uniform width extending in the longitudinal direction of the metal foil 6 on a band-like extending 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 and pressing 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.

In this case, in the embodiment of the present invention, the elongation rate equalization operation is performed in a state where a longitudinal tension is applied to the sheet-shaped electrode body 1. In the 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 the embodiment of the present invention, the cylindrical elastic outer peripheral surface of one roll 21 is pressed against the sheet-shaped 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-shaped electrode body 1 in 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.

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 portion A, and during the stretch equalization operation, a portion of the cylindrical elastic outer peripheral surface of each roll 20, 21 is pressed against the widthwise edge portion 10 of the electrode material coated portion A and the protective layer 9, and another portion of the cylindrical elastic outer peripheral surface of each roll 20, 21 is pressed against the electrode material uncoated portion B. In this case, in this embodiment, the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge portion 10 of the electrode material coated portion A and the protective layer 9 during the stretch 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.

REFERENCE SIGNS LIST 1 Sheet-shaped electrode body 2 Pressing device 3 Elongation equalization device 4 Tensioning device 6 Metal foil 7, 8 Electrode material layer 10 Width direction edge 20 Lower roll 21 Upper roll A Electrode material coated portion B Electrode material uncoated portion

Claims (5)

A method for manufacturing an electrode body for manufacturing a sheet-shaped electrode body having an electrode material coated part of uniform width extending in the longitudinal direction of the metal foil on a band-shaped metal foil and electrode material uncoated parts extending in the longitudinal direction of the metal foil on both sides of the electrode material coated part, 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 part to uniform the elongation rate of the entire sheet-shaped electrode body by stretching the electrode material uncoated part in the longitudinal direction, and the elongation rate equalization operation is performed by passing the sheet-shaped electrode body between rotating rolls arranged in parallel and pressing the cylindrical elastic outer peripheral surface of each roll onto the sheet-shaped electrode body, and the cylindrical elastic outer peripheral surface portion pressed against the widthwise edge of the electrode material coated part 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 part. The method for manufacturing an electrode body according to claim 1, wherein the elongation uniformization process is performed while applying tension in the longitudinal direction to the sheet-shaped electrode body. The method for manufacturing an electrode assembly 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 pressed against the electrode material uncoated portion 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 pressed against the widthwise edge of the electrode material coated portion is within the range of 12 MPa to 18 MPa when compressed. The method for manufacturing an electrode assembly according to claim 1, wherein the cylindrical elastic outer peripheral surface of one roll is pressed against the sheet-shaped electrode assembly only at the widthwise 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 assembly over the entire electrode material coated portion, including the widthwise edges of the electrode material uncoated portion and the electrode material coated portion. A method for manufacturing an electrode assembly according to claim 1, in which 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 stretch equalization operation is made of 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 portion.

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