Rolling device and rolling method for electrode sheet

Abstract

To reduce the difference in extension between a plurality of unformed parts on an electrode sheet.SOLUTION: A rolling device comprises: a conveying device that conveys an electrode sheet 1 in a longitudinal direction along a predetermined conveyance path; a pair of press rolls that are arranged on the conveyance path of the electrode sheet 1 and sandwiches the electrode sheet 1 to press an active material layer 3; and a correction roll 80 that is arranged on the upstream side or the downstream side of the pair of press rolls on the conveyance path and extends in a width direction of the electrode sheet 1. The correction roll 80 includes at least one small-diameter part 84 that is provided at a position corresponding to the active material layer 3 with respect to the width direction of the electrode sheet 1, and a plurality of large-diameter parts 85 that have an outer diameter larger than the small-diameter part 84, around which at least two unformed parts 4 are wound. The plurality of large-diameter parts 85 include a first large-diameter part 85R and a second large-diameter part 85L having an outer diameter larger than the first large-diameter part 85R.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a rolling device and a rolling method for an electrode sheet. [Background technology]

[0002] For example, Patent Document 1 discloses an apparatus for pressing a strip-shaped electrode plate (electrode sheet) having an active material-containing layer formed by applying an active material-containing slurry to a strip-shaped current collector and an exposed current collector portion where no active material-containing layer is present. The apparatus described in Patent Document 1 includes a press roll for pressing the active material-containing layer and a guide roller that also functions as a curvature correction device. According to Patent Document 1, the pressing pressure of the press roll is mainly applied to the active material-containing layer, and is hardly applied to the exposed current collector portion. Therefore, the elongation of the exposed current collector portion is smaller than that of the underlying current collector of the active material-containing layer. As a result, distortion and warping of the strip-shaped electrode plate are reportedly generated.

[0003] The guide roller described in Patent Document 1 has a step with which the exposed current collector portion comes into contact and a recess facing the active material-containing layer. According to Patent Document 1, this allows the tension applied to the strip-shaped electrode plate in the conveying direction to be concentrated on the exposed current collector portion. As a result, the exposed current collector portion can be stretched, and distortion and warping of the strip-shaped electrode plate can be corrected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6021508 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the findings of the present inventors, in an electrode sheet in which a plurality of unformed portions, where an active material layer is not formed, are arranged along the width direction, distortion of the electrode sheet may occur due to differences in elongation among the plurality of unformed portions, even when the unformed portions are stretched using a stepped roll as described in Patent Document 1. Therefore, an object of the present invention is to suppress differences in elongation among the plurality of unformed portions in an electrode sheet. [Means for solving the problem]

[0006] The electrode sheet rolling device disclosed herein is a rolling device that rolls an electrode sheet in which at least one active material layer and at least two unformed portions are alternately arranged along the width direction of a strip-shaped current collector, and the unformed portions are arranged at both ends in the width direction. The rolling device includes a conveying device that conveys the electrode sheet in the longitudinal direction along a predetermined conveying path, a pair of press rolls that are arranged on the conveying path of the electrode sheet conveyed by the conveying device and that sandwich the electrode sheet to press the active material layer, and a straightening roll that is arranged on the conveying path upstream or downstream of the pair of press rolls and extends in the width direction of the electrode sheet. The straightening roll includes at least one small diameter portion that is provided at a position corresponding to the active material layer in the width direction of the electrode sheet, and multiple large diameter portions that have an outer diameter larger than the small diameter portion and around which the at least two unformed portions are respectively wound. The multiple large diameter portions include a first large diameter portion and a second large diameter portion that has an outer diameter larger than the first large diameter portion.

[0007] According to the electrode sheet rolling device, the plurality of large diameter portions of the straightening roll include a first large diameter portion around which one unformed portion is wound, and a second large diameter portion around which another unformed portion is wound and which has an outer diameter larger than that of the first large diameter portion. The unformed portion wound around the second large diameter portion, which has an outer diameter larger than that of the first large diameter portion, elongates more than the unformed portion wound around the first large diameter portion. Due to the difference in elongation of the unformed portions caused by the difference in the outer diameters of the large diameter portions, it is possible to adjust and suppress the difference in the amount of elongation among the plurality of unformed portions.

[0008] Also disclosed herein is a rolling method for an electrode sheet, which includes conveying an electrode sheet having at least one active material layer and at least two unformed portions alternately arranged along the width direction of a strip-shaped current collector, with the unformed portions arranged at both ends in the width direction, while pressing the active material layer and stretching the unformed portions using a straightening roll. The straightening roll has at least one small diameter portion provided at a position corresponding to the active material layer in the width direction of the electrode sheet, and multiple large diameter portions, each having an outer diameter larger than that of the small diameter portion, provided at a position corresponding to the at least two unformed portions in the width direction of the electrode sheet. The multiple large diameter portions include a first large diameter portion and a second large diameter portion having an outer diameter larger than that of the first large diameter portion. The rolling method disclosed herein includes a step of winding the at least two unformed portions around each of the multiple large diameter portions and applying tension to the electrode sheet.

[0009] The electrode sheet rolling method described above can also achieve the same effects as the electrode sheet rolling device described above. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic side view of a rolling device for an electrode sheet. [Figure 2] FIG. 2 is a schematic front view of a guide roll. [Figure 3] FIG. 2 is a schematic front view of a straightening roll. [Figure 4] FIG. [Figure 5] 10 is a flowchart of an operation for determining the outer diameter of a left large diameter portion and an outer diameter of a right large diameter portion. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a rolling apparatus for electrode sheets of an electricity storage device will be described below. It should be noted that the embodiment described here is not intended to limit the scope of the present invention. Furthermore, the drawings are schematic diagrams and do not necessarily faithfully reflect actual products.

[0012] [Rolling equipment configuration] FIG. 1 is a schematic side view of an electrode sheet rolling apparatus 10 according to one embodiment. In this example, the rolling apparatus 10 rolls an electrode sheet 1 for a lithium-ion secondary battery. However, the electrode sheet 1 is not limited to an electrode sheet for a lithium-ion secondary battery, and may be an electrode sheet for various known electricity storage devices. The term "electricity storage device" refers generally to devices that can extract electrical energy, and includes so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as electric double layer capacitors.

[0013] The electrode sheet 1 includes a strip-shaped current collector foil 2 and an active material layer 3 formed on the current collector foil 2 (see FIG. 2). The portion of the current collector foil 2 where the active material layer 3 is not formed constitutes an unformed portion 4. The positive electrode sheet is a member in which a positive electrode active material layer 3 containing a positive electrode active material is formed on the surface of a strip-shaped current collector foil 2 (e.g., aluminum foil) of a predetermined width and thickness. In a lithium-ion secondary battery, the positive electrode active material is, for example, a material that can release lithium ions during charging and absorb lithium ions during discharging, such as a lithium-transition metal composite material. In the positive electrode sheet, the active material layer 3 and the unformed portion 4 are protected by a protective layer. The negative electrode sheet is a member in which a negative electrode active material layer 3 containing a negative electrode active material is formed on the surface of a strip-shaped current collector foil 2 (e.g., copper foil) of a predetermined width and thickness. In a lithium-ion secondary battery, the negative electrode active material is, for example, a material such as natural graphite that can absorb lithium ions during charging and release the absorbed lithium ions during discharging. Various positive electrode active materials and negative electrode active materials have been proposed other than those described above, and are not particularly limited.

[0014] The raw material for the active material layer 3 is formed into a slurry and applied to the current collector foil 2. The raw material for the active material layer 3 may be applied to one or both sides of the current collector foil 2. At least one active material layer 3 and at least two unformed portions 4 are alternately arranged on the electrode sheet 1 along the width direction of the strip-shaped current collector foil 2. An unformed portion 4 is arranged on each of both ends of the electrode sheet 1 in the width direction. Here, the electrode sheet 1 is assumed to be an electrode sheet having an active material layer 3 formed in the center of the current collector foil 2 in the width direction and having unformed portions 4 on both ends (hereinafter, the unformed portion 4 on the left side of FIG. 2 will be referred to as 4L, and the unformed portion 4 on the right side will be referred to as 4R, as appropriate). However, the active material layer 3 may be formed in multiple strips in the width direction of the electrode sheet 1. In this case, multiple unformed portions 4 are formed at both ends of the electrode sheet 1 and between the multiple active material layers 3. The rolling device 10 continuously presses the electrode sheet 1 while transporting it in the longitudinal direction, adjusting the thickness of the active material layer 3 to within a predetermined range and densifying the active material in the active material layer 3.

[0015] 1, the rolling apparatus 10 includes a conveying device 20 that conveys the electrode sheet 1, a roll press 30 that presses the electrode sheet 1, and a warpage correction device 40 that suppresses warpage or distortion of the electrode sheet 1 due to pressing. The rolling apparatus 10 may also include an inspection device or the like, but explanation and illustration thereof will be omitted here.

[0016] The conveying device 20 conveys the electrode sheet 1 in the longitudinal direction along a predetermined conveying path. In this example, the conveying device 20 is disposed at the most downstream side of the rolling device 10 and includes a winding device 21 that winds up the electrode sheet 1 after rolling. The strip-shaped electrode sheet 1 is transported in the longitudinal direction by being wound up by the winding device 21.

[0017] The roll press machine 30 includes a pair of press rolls 31U and 31D that sandwich and press the electrode sheet 1, and a drive device 32 that drives the pair of press rolls 31U and 31D. The pair of press rolls 31U and 31D are arranged on the transport path of the electrode sheet 1 transported by the transport device 20, and sandwich the electrode sheet 1 to press the active material layer 3.

[0018] The warpage correction device 40 is provided upstream of the roll press machine 30 in the transport path of the electrode sheet 1. However, the warpage correction device 40 may also be provided downstream of the roll press machine 30 in the transport path of the electrode sheet 1. As shown in FIG. 1 , the warpage correction device 40 includes upstream and downstream nip rolls 50U and 50D, upstream and downstream dancer rolls 60U and 60D, multiple guide rolls 70, a correction roll 80, and a wrap angle adjustment roll 90. When the active material layer 3 is pressed with the press rolls 31U and 31D, the current collector foil 2 stretches in the areas where the active material layer 3 is formed, while the unformed areas 4 stretch very little. This creates a difference in elongation between the areas where the active material layer 3 is formed and the unformed areas 4, causing distortion and warping in the electrode sheet 1. The warpage correction device 40 suppresses such warpage and distortion of the electrode sheet 1 by pre-stretching the unformed areas 4 before pressing.

[0019] The upstream and downstream nip rolls 50U and 50D define a section in which high tension is applied to the electrode sheet 1. High tension is applied to the electrode sheet 1 between the upstream nip roll 50U and the downstream nip roll 50D. The tension of the electrode sheet 1 can be adjusted to be weaker upstream of the upstream nip roll 50U and downstream of the downstream nip roll 50D than in the above sections. The tension in the section between the upstream nip roll 50U and the downstream nip roll 50D is applied by the upstream dancer roll 60U located in this section. The downstream dancer roll 60D adjusts the tension of the electrode sheet 1 downstream of the above section. The tension applied in the section between the upstream nip roll 50U and the downstream nip roll 50D stretches the unformed portion 4 of the electrode sheet 1.

[0020] The multiple guide rolls 70 are rolls that bend the conveying direction of the electrode sheet 1. The conveying path of the electrode sheet 1 is bent multiple times by being wound around the multiple guide rolls 70. FIG. 2 is a schematic front view of the guide roll 70. As shown in FIG. 2, the guide roll 70 includes a roll main body 71, a roll support member 72, and a support wall 73.

[0021] The roll body 71 is formed in a cylindrical shape and extends in the width direction of the electrode sheet 1. The electrode sheet 1 is wound around the outer peripheral surface of the roll body 71. The roll support member 72 rotatably supports the roll body 71. Here, the roll support member 72 is provided with a pair of bearing portions 72a that support both ends of the roll body 71. However, the configuration of the roll support member 72 is not limited to this. The roll support member 72 may be provided with, for example, a rotation shaft around which the roll body 71 rotates. In this embodiment, the roll support member 72 supports both ends of the roll body 71, but it may also support only one end.

[0022] The support wall 73 is disposed on one side of the roll body 71 and the roll support member 72 in the width direction of the electrode sheet 1 (here, the left side in FIG. 2 ), and supports the roll support member 72. The roll support member 72 is supported on one side only by the support wall 73. The support wall 73 is, for example, a wall portion extending vertically. However, the shape of the member supporting the roll support member 72 on one side is not particularly limited. Such a one-side support configuration is required to reduce the cost of the rolling device 10 and to simplify the work of passing the electrode sheet 1 through the conveying path. However, due to such a configuration, the roll support member 72 is likely to bend when high tension is applied to the electrode sheet 1. The effect of bending of the roll support member 72 will be described later.

[0023] The straightening roll 80 is a roll for adjusting the amount of stretch of the unformed portion 4 of the electrode sheet 1. In this embodiment, the straightening roll 80 is arranged upstream of the pair of press rolls 31U, 31D. The rolling device 10 according to this embodiment is configured to stretch the unformed portion 4 by the straightening roll 80 before pressing the active material layer 3. However, the straightening roll 80 may also be arranged downstream of the pair of press rolls 31U, 31D. In this case, the step of stretching the unformed portion 4 by the straightening roll 80 is performed after the step of pressing the active material layer 3.

[0024] FIG. 3 is a schematic front view of the straightening roll 80. The left and right sides of FIG. 3 correspond to the left and right sides of FIG. 2, respectively. As shown in FIG. 3, the straightening roll 80 includes a straightening roll body 81, a roll support member 82, and a support wall 83. The roll support member 82 rotatably supports the straightening roll body 81. The axial direction of the straightening roll body 81 coincides with the width direction of the electrode sheet 1.

[0025] The configuration of the roll support member 82 may be the same as or different from the roll support member 72 of the guide roll 70. Here, the roll support member 82 supports both the left and right ends of the straightening roll body 81. The support wall 83 is disposed on one side of the straightening roll body 81 and the roll support member 82 in the width direction of the electrode sheet 1 (here, the left side in FIG. 3 ) and supports the roll support member 82. The roll support member 82 is also supported on one side only by the support wall 83. The straightening roll body 81 of the straightening roll 80 is supported on the same side as the roll body 71 of the guide roll 70. Hereinafter, the supported end side (here, the left side) of the straightening roll 80 and the multiple guide rolls 70 will be referred to as the supported end side, and the unsupported end side (here, the right side) will be referred to as the free end side. The support wall 83 may be a common wall portion with the support wall 73 of the guide roll 70, or may be a different wall portion.

[0026] As shown in FIG. 3 , the correction roll body 81 includes at least one small diameter portion 84 provided at a position corresponding to the active material layer 3 in the width direction of the electrode sheet 1, and multiple large diameter portions 85 around which at least two unformed portions 4 are wound. The multiple large diameter portions 85 have a larger outer diameter than the small diameter portion 84. The multiple large diameter portions 85 are provided at positions corresponding to the multiple unformed portions 4 in the width direction of the electrode sheet 1. The multiple large diameter portions 85 serve to stretch the wound multiple unformed portions 4. The small diameter portion 84 is a portion that is retracted radially inward of the correction roll body 81 to avoid the active material layer 3. The small diameter portion 84 and the large diameter portion 85 enable the unformed portions 4 to be stretched without stretching the portions of the current collector foil 2 on which the active material layer 3 is formed.

[0027] As shown in FIG. 3 , in this embodiment, the small diameter portion 84 is provided in the center of the correction roll body 81 in the axial direction (width direction of the electrode sheet 1), at a position corresponding to the active material layer 3. Herein, there is one small diameter portion 84. Multiple large diameter portions 85 are arranged on the left and right sides of the small diameter portion 84. In this embodiment, there are two large diameter portions 85. However, the number of small diameter portions 84 and large diameter portions 85 varies depending on the number of active material layers 3 and unformed portions 4 arranged in the width direction of the electrode sheet 1. Hereinafter, when distinguishing between the two large diameter portions 85, the large diameter portion 85 on the left side (support end side) will also be referred to as the left large diameter portion 85L and the large diameter portion 85 on the right side (free end side) will also be referred to as the right large diameter portion 85R. The left large diameter portion 85L is connected to the left end of the small diameter portion 84. The right large diameter portion 85R is connected to the right end of the small diameter portion 84.

[0028] In a state in which the unformed portion 4 of the electrode sheet 1 is wrapped around the large diameter portion 85, the small diameter portion 84 faces the active material layer 3 but is spaced apart from the active material layer 3.

[0029] The left large diameter portion 85L and the right large diameter portion 85R are formed with diameters approximately 1 mm to 2 mm larger than the small diameter portion 84. The diameter DL of the left large diameter portion 85L is different from the diameter DR of the right large diameter portion 85R. In this embodiment, the diameter DL of the left large diameter portion 85L on the support end side is larger than the diameter DR of the right large diameter portion 85R on the free end side. The difference between the diameter DL of the left large diameter portion 85L and the diameter DR of the right large diameter portion 85R is, for example, approximately 0.05 mm to 0.1 mm. However, the difference between the diameter DL of the left large diameter portion 85L and the diameter DR of the right large diameter portion 85R is determined based on the actual measured values ​​of the elongation amounts of the left and right unformed portions 4L and 4R, as described below, and is not particularly limited. Furthermore, depending on the actual measured values ​​of the elongation amounts of the left and right unformed portions 4L and 4R, the diameter DR of the right large diameter portion 85R on the free end side may be larger than the diameter DL of the left large diameter portion 85L on the support end side.

[0030] The left large diameter portion 85L and the right large diameter portion 85R abut against the left and right unformed portions 4L, 4R, respectively, at a predetermined distance outward in the width direction from the left and right ends of the active material layer 3. For example, the left large diameter portion 85L and the right large diameter portion 85R are each provided so that their inner edges abut against the center portions of the unformed portions 4L, 4R in the left-right direction, or slightly inward from the center portions. This stretches the unformed portions 4L, 4R (and a protective layer in the case of a positive electrode sheet) while preventing the active material layer 3 from stretching together. However, the positions at which the left large diameter portion 85L and the right large diameter portion 85R abut against the unformed portions 4L, 4R are not limited to the above positions.

[0031] The straightening roll 80 according to this embodiment includes multiple types of left attachments 86L with different outer diameters, which form the outer periphery of the left large diameter portion 85L. The straightening roll 80 includes a left attachment receiving portion 87L to which one of the multiple types of left attachments 86L is attached. FIG. 4 is a perspective view of the left attachment 86L. As shown in FIG. 4, the left attachment 86L is configured in a cylindrical shape. The outer diameter DL1 of the left attachment 86L varies depending on the type of left attachment 86L. The outer diameter DL1 of the selected left attachment 86L becomes the outer diameter DL of the left large diameter portion 85L. The inner diameter DL2 of the left attachment 86L is the same regardless of the type of left attachment 86L and is equal to the outer diameter of the left attachment receiving portion 87L.

[0032] Similar to the left large diameter portion 85L, the straightening roll 80 is provided with multiple types of right attachments 86R with different outer diameters that form the outer periphery of the right large diameter portion 85R. The straightening roll 80 is provided with a right mounting portion 87R to which one of the multiple types of right attachments 86R is attached. The right attachment 86R and the right mounting portion 87R are configured similarly to the left attachment 86L and the left mounting portion 87L, respectively.

[0033] In this embodiment, the straightening roll 80 includes multiple types of left attachments 86L and multiple types of right attachments 86R, each of which has a different outer diameter and forms the outer periphery of the left large diameter portion 85L or the right large diameter portion 85R. However, the straightening roll 80 may include only multiple types of left attachments 86L or multiple types of right attachments 86R, each of which has a different outer diameter and forms the outer periphery of the left large diameter portion 85L or the right large diameter portion 85R. In this case, the right large diameter portion 85R or the left large diameter portion 85L may be configured so that the outer diameter cannot be changed. It is also possible to adjust the difference between the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R by changing the outer diameter of only one of the large diameter portions 85.

[0034] The wrap angle adjusting roll 90 adjusts the wrap angle when the electrode sheet 1 is wound around the correction roll 80. The wrap angle adjusting roll 90 is provided adjacent to the correction roll 80 so that the wrap angle of the correction roll 80 can be adjusted, and is configured to be movable in a direction perpendicular to the axis.

[0035] [Reason for making the diameters of the large diameter parts on the left and right different] The reason for making the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R different will be explained below. As described above, in the rolling device 10 according to this embodiment, the multiple guide rolls 70 are supported on one side. Therefore, when high tension is applied to the electrode sheet 1, the free end side of the guide roll 70 is deflected by the tension, while the deflection on the supported end side of the guide roll 70 is small. As a result, the conveyance path of the electrode sheet 1 becomes longer on the free end side, and the unformed portion 4R on the free end side stretches more than the unformed portion 4L on the supported end side. The straightening roll 80 makes the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R different from each other, thereby straightening the difference in the amount of elongation of the unformed portion 4 between the free end side and the supported end side.

[0036] In this embodiment, the diameter DL of the left large diameter portion 85L on the support end side is larger than the diameter DR of the right large diameter portion 85R on the free end side. Therefore, the unformed portion 4L on the support end side, which is wound around the left large diameter portion 85L, is stretched longer by the straightening roll 80 than the unformed portion 4R on the free end side, which is wound around the right large diameter portion 85R. This reduces the difference in the amount of stretch between the unformed portion 4R on the free end side and the unformed portion 4L on the support end side, which is caused by one-sided support by the guide roll 70.

[0037] Table 1 shows the difference in elongation rate between the left and right unformed portions 4L, 4R when the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R are different (Example), and the difference in elongation rate between the left and right unformed portions 4L, 4R when the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R are the same (Comparative Example). As shown in Table 1, the difference in elongation rate between the left and right unformed portions 4L, 4R is smaller in the Example than in the Comparative Example. [Table 1]

[0038] Note that differences in the elongation rates of the left and right unformed portions 4L, 4R may also occur depending on other factors, such as the state of the electrode sheet 1. For example, even if the guide roll 70, the straightening roll 80, and all other rolls are supported on both ends rather than on one side, differences in the elongation rates of the left and right unformed portions 4L, 4R may still occur. For example, if there is an original difference in thickness between the left and right current collector foils 2, differences in the elongation rates of the left and right unformed portions 4 may occur even if equal tension is applied to the left and right unformed portions 4. Therefore, which of the two (or three or more) large diameter portions 85 of the straightening roll 80 has a larger outer diameter and which has a smaller outer diameter may vary and is not limited.

[0039] [Unformed part stretching process] In this embodiment, the amount of stretch of a plurality of unformed portions 4 is measured in advance, and the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R are determined based on the measured amount of stretch. Then, the unformed portions 4 of the electrode sheet 1 are actually stretched under the determined conditions. An example of this procedure is described below.

[0040] 5 is a flowchart of a process for determining the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R and stretching the unformed portion 4. As shown in FIG. 5, the process for stretching the unformed portion 4 includes steps S01 to S05 for determining the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R. The process for stretching the unformed portion 4 further includes step S06 for winding at least two unformed portions 4 around each of the plurality of large diameter portions 85 and applying tension to the electrode sheet 1.

[0041] As shown in FIG. 5, in step S01 of the process for determining the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R, the left and right unformed portions 4L, 4R are actually stretched using the longitudinal ends of the electrode sheet 1. In step S01, the electrode sheet 1 is passed between a pair of upstream and downstream nip rolls 50U, 50D, and the electrode sheet 1 is wound around each roll of the warpage correction device 40. Thereafter, each roll of the warpage correction device 40 is driven, and tension is applied to the electrode sheet 1 by the dancer roll 60U. As a result, the electrode sheet 1 is transported along the transport path, and the left and right unformed portions 4L, 4R are stretched.

[0042] In the following step S02, the elongation of the unformed portion 4L stretched by the left large diameter portion 85L and the elongation of the unformed portion 4R stretched by the right large diameter portion 85R are measured. In step S03, the difference between the elongation rate of the unformed portion 4L and the elongation rate of the unformed portion 4R is calculated, and it is determined whether the calculated difference in elongation rate is equal to or less than a predetermined threshold. If the difference in elongation rate is equal to or less than the threshold (if the result of step S03 is YES), in step S05, it is determined that the left attachment 86L and the right attachment 86R are to be used as is without being changed. If the difference in elongation rate exceeds the threshold (if the result of step S03 is NO), in step S04, the outer diameter of at least one of the left large diameter portion 85L and the right large diameter portion 85R is adjusted based on the measured elongation of the unformed portions 4L and 4R. In step S04, at least one of the left attachment 86L and the right attachment 86R is replaced so as to eliminate the difference in elongation rate calculated in step S03. In step S04, one of the multiple types of left attachments 86L or one of the multiple types of right attachments 86R is selected and attached to the straightening roll 80.

[0043] After step S04, steps S01 to S03 are performed again. If the result of step S03 becomes YES after repeating steps S01 to S04, the left attachment 86L and the right attachment 86R to be used are determined in step S05. Step S06, which stretches the unformed portion 4 as a production process for the adjusted electrode sheet 1, is the same as step S01.

[0044] [Effects of the embodiment] The following describes the effects that can be achieved by the rolling device 10 for the electrode sheet 1 according to this embodiment and the process using the rolling device 10.

[0045] The rolling device 10 for the electrode sheet 1 according to this embodiment is a rolling device that rolls an electrode sheet 1 in which at least one active material layer 3 and at least two unformed portions 4 are alternately arranged along the width direction of a strip-shaped current collector foil 2. The unformed portions 4 are arranged at both ends of the electrode sheet 1 in the width direction. The rolling device 10 includes a conveying device 20 that conveys the electrode sheet 1 in the longitudinal direction along a predetermined conveying path, a pair of press rolls 31U, 31D that are arranged on the conveying path of the electrode sheet 1 conveyed by the conveying device 20 and that sandwich the electrode sheet 1 to press the active material layer 3, and a straightening roll 80 that is arranged upstream of the pair of press rolls 31U, 31D on the conveying path of the electrode sheet 1 and extends in the width direction of the electrode sheet 1. The straightening roll 80 includes at least one small diameter portion 84 that is provided at a position corresponding to the active material layer 3 in the width direction of the electrode sheet 1, and multiple large diameter portions 85 that have an outer diameter larger than that of the small diameter portion 84 and around which at least two unformed portions 4 are respectively wound. The plurality of large diameter portions 85 include a first large diameter portion and a second large diameter portion having an outer diameter larger than that of the first large diameter portion. In this embodiment, the first large diameter portion is the right large diameter portion 85R. The second large diameter portion is the left large diameter portion 85L.

[0046] According to this rolling device 10, the unformed portion 4L wound around the second large diameter portion (here, the left large diameter portion 85L), which has a larger outer diameter than the first large diameter portion (here, the right large diameter portion 85R), elongates more than the unformed portion 4R wound around the first large diameter portion. As described above, the amount of elongation of the multiple unformed portions 4 may vary depending on the configuration of the rolling device 10, the state of the electrode sheet 1, and the like. According to the rolling device 10 of this embodiment, the difference in the amount of elongation between the multiple unformed portions 4 described above can be adjusted by using the difference in the elongation of the unformed portions 4 caused by the difference in the outer diameter of the large diameter portion 85. As a result, the difference in the amount of elongation between the multiple unformed portions 4 can be suppressed.

[0047] In this embodiment, the straightening roll 80 is disposed upstream of the pair of press rolls 31U, 31D. This configuration reduces the risk of the electrode sheet 1 breaking during the pressing process of the active material layer 3. The straightening roll 80 can also be disposed downstream of the pair of press rolls 31U, 31D. However, stretching the unformed portions 4 before the pressing process of the active material layer 3 reduces the risk of the unformed portions 4 being unable to keep up with the stretching of the active material layer 3 during the pressing process, thereby reducing the risk of the electrode sheet 1 breaking. Note that the rolling device 10 may be provided with another straightening roll disposed downstream of the pair of press rolls 31U, 31D on the conveying path, and may be configured to straighten the warp of the electrode sheet 1 before and after pressing.

[0048] The rolling apparatus 10 according to this embodiment further includes a guide roll 70, which is disposed upstream or downstream of the straightening roll 80 in the conveyance path and around which the electrode sheet 1 is wound. The guide roll 70 includes a roll body 71 extending in the width direction of the electrode sheet 1, a roll support member 72 that rotatably supports the roll body 71, and a support wall 83 that is disposed on one side (here, the left) of the roll body 71 and the roll support member 72 in the width direction of the electrode sheet 1 and supports the roll support member 72. The roll support member 82 is supported on one side only by the support wall 83. A second large diameter portion having a larger outer diameter, here the left large diameter portion 85L, is disposed on the one side (i.e., the left support end side) in the width direction of the electrode sheet 1 relative to the first large diameter portion having a smaller outer diameter, here the right large diameter portion 85R.

[0049] As described above, by supporting the guide roll 70 on one side at the support end, the unformed portion 4R on the free end side is stretched longer by the guide roll 70 than the unformed portion 4L on the support end side. On the other hand, according to the configuration of the straightening roll 80 as described above, the unformed portion 4L on the support end side, which is wound around the left large diameter portion 85L having a larger outer diameter, is stretched longer by the straightening roll 80 than the unformed portion 4R on the free end side, which is wound around the right large diameter portion 85R. Therefore, by winding the unformed portion 4 on the straightening roll 80, the difference in the amount of elongation of the unformed portion 4 between the free end side and the support end side, which is caused by the one-side support of the guide roll 70, is reduced.

[0050] In this embodiment, the left large diameter portion 85L and the right large diameter portion 85R are each configured to have an adjustable outer diameter. With this configuration, the difference between the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R can be adjusted depending on the extent to which the left unformed portion 4L or the right unformed portion 4R is stretched more than the other. This further reduces the difference in stretch between the left unformed portion 4L and the right unformed portion 4R. Note that similar effects can be achieved if at least one of the left large diameter portion 85L and the right large diameter portion 85R is configured to have an adjustable outer diameter.

[0051] In this embodiment, the straightening roll 80 includes multiple types of left attachments 86L with different outer diameters that form the outer periphery of the left large diameter portion 85L, and multiple types of right attachments 86R with different outer diameters that form the outer periphery of the right large diameter portion 85R. The straightening roll 80 includes a left attachment portion 87L to which one of the multiple types of left attachments 86L is attached, and a right attachment portion 87R to which one of the multiple types of right attachments 86R is attached. With this configuration, the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R can be easily adjusted by replacing the attachments 86L and 86R.

[0052] The rolling method for the electrode sheet 1 according to this embodiment includes step S02 of measuring the elongation of the unformed portion 4L stretched by the left large diameter portion 85L and the elongation of the unformed portion 4R stretched by the right large diameter portion 85R, and step S04 of adjusting the outer diameter of at least one of the left large diameter portion 85L and the right large diameter portion 85R based on the measured elongation of the unformed portions 4L and 4R. This method makes it possible to determine in step S02 which of the left unformed portion 4L and the right unformed portion 4R is stretched more than the other, and to what extent. Furthermore, in step S04, the difference between the outer diameter DL of the left large diameter portion 85L and the outer diameter DR of the right large diameter portion 85R can be adjusted based on the result of step S02. This reduces the difference in elongation between the left unformed portion 4L and the right unformed portion 4R.

[0053] The rolling apparatus 10 according to this embodiment is particularly effective when rolling a positive electrode sheet in which the current collector foil 2 is made of aluminum foil and the active material layer 3 is a positive electrode active material layer. In a positive electrode sheet, it is desirable to strongly press the active material layer 3 to increase the density of the positive electrode active material, but this tends to increase the warping and distortion of the positive electrode sheet. Furthermore, because positive electrode active materials are generally harder than negative electrode active materials, high pressure is required to achieve the desired compression ratio, which increases the elongation of the active material layer 3. This increases the target value for the elongation of the unformed portion 4, which tends to increase the difference in elongation between the unformed portion 4L on the left side and the unformed portion 4R on the right side. Therefore, the rolling apparatus 10 according to this embodiment is particularly effective when rolling a positive electrode sheet in which the current collector foil 2 is made of aluminum foil and the active material layer 3 is a positive electrode active material layer.

[0054] [Other embodiments] The above describes one embodiment of the electrode sheet rolling device proposed herein. However, the above embodiment is merely an example, and other aspects may be employed. For example, in the above embodiment, large diameter portions are provided at both ends of the correction roll body, and the outer diameter of one large diameter portion is larger than the outer diameter of the other large diameter portion. However, a correction roll corresponding to an electrode sheet having three or more unformed portions may have three or more large diameter portions, and the large diameter portions having outer diameters larger or smaller than the other large diameter portions may be large diameter portions other than those at both ends. Furthermore, in a correction roll having three or more large diameter portions, the outer diameters of the multiple large diameter portions may be three or more different.

[0055] In the above-described embodiment, the outer diameter of the large diameter portion is changed by selecting an attachment. However, the method for adjusting the outer diameter of the large diameter portion is not limited to this. The outer diameter of the large diameter portion may be adjusted, for example, by wrapping something like tape around the outer periphery of the large diameter portion. As long as the rolling conditions are stable, the outer diameters of the multiple large diameter portions may be fixed and unadjustable.

[0056] The above-described embodiments do not limit the present invention unless otherwise specified. Furthermore, the technology disclosed herein can be modified in various ways, and the components and processes described herein can be omitted or combined as appropriate, provided that no particular problems arise.

[0057] This specification includes the disclosures set forth in the following sections:

[0058] Section 1: A rolling device that rolls an electrode sheet in which at least one active material layer and at least two unformed portions are alternately arranged along the width direction of a strip-shaped current collector and the unformed portions are arranged at both end portions in the width direction, a conveying device that conveys the electrode sheet in a longitudinal direction along a predetermined conveying path; a pair of press rolls that are arranged on a path along which the electrode sheet is conveyed by the conveying device and that press the active material layer by sandwiching the electrode sheet therebetween; a correction roll that is arranged on the upstream side or downstream side of the pair of press rolls in the conveying path and extends in the width direction of the electrode sheet, The straightening roll is at least one small diameter portion provided at a position corresponding to the active material layer in the width direction of the electrode sheet; a plurality of large diameter portions having an outer diameter larger than that of the small diameter portion, around which the at least two unformed portions are respectively wound; The plurality of large diameter portions are a first large diameter portion; a second large diameter portion having an outer diameter larger than that of the first large diameter portion, Electrode sheet rolling equipment.

[0059] Section 2: The straightening roll is disposed upstream of the pair of press rolls. Item 1. The rolling device according to item 1.

[0060] Section 3: a guide roll disposed upstream or downstream of the correction roll in the conveying path and around which the electrode sheet is wound, The guide roll is a roll body extending in the width direction of the electrode sheet; a first support member that rotatably supports the roll body; a second support member that is disposed on one side of the roll body and the first support member in the width direction and supports the first support member, the first support member is supported on one side only by the second support member, the second large diameter portion is disposed on the one side in the width direction relative to the first large diameter portion, Item 1 or 2. The rolling device according to item 1 or 2.

[0061] Section 4: At least one of the first large diameter portion and the second large diameter portion is configured to be adjustable in outer diameter. Item 4. The rolling device according to any one of Items 1 to 3.

[0062] Section 5: The straightening roll is a plurality of types of attachments having different outer diameters that configure an outer periphery of at least one of the first large diameter portion and the second large diameter portion; and a mounting portion to which any one of the plurality of types of attachments is mounted. Item 5. The rolling device according to item 4.

[0063] Item 6: The electrode sheet is a positive electrode sheet in which the current collector is made of aluminum foil and the active material layer is a positive electrode active material layer. Item 6. The rolling device according to any one of Items 1 to 5.

[0064] Section 7: A method for pressing an active material layer and stretching the unformed portions by a straightening roll while conveying an electrode sheet in which at least one active material layer and at least two unformed portions are alternately arranged along the width direction of a strip-shaped current collector and the unformed portions are arranged at both end portions in the width direction, the method comprising: The straightening roll is at least one small diameter portion provided at a position corresponding to the active material layer in the width direction of the electrode sheet; a plurality of large diameter portions each having an outer diameter larger than that of the small diameter portion, the large diameter portions being provided at positions corresponding to the at least two unformed portions in the width direction of the electrode sheet; the plurality of large diameter portions include a first large diameter portion and a second large diameter portion having an outer diameter larger than that of the first large diameter portion, a step of winding the at least two unformed portions around each of the plurality of large diameter portions and applying tension to the electrode sheet, Electrode sheet rolling method.

[0065] Section 8: Item 8. The rolling method according to Item 7, wherein the unformed portion is stretched by the straightening roll before pressing the active material layer.

[0066] Section 9: measuring an elongation of the unformed portion stretched by the first large diameter portion and an elongation of the unformed portion stretched by the second large diameter portion; and adjusting the outer diameter of at least one of the first large diameter portion and the second large diameter portion based on the measured elongation of the unformed portion. Item 7 or 8. The rolling method according to item 7 or 8.

[0067] Section 10: In the step of adjusting the outer diameter, any one of a plurality of types of attachments having different outer diameters that configure an outer periphery of at least one of the first large diameter portion and the second large diameter portion is attached to the straightening roll. Item 10. The rolling method according to item 9.

[0068] Section 11: The electrode sheet is a positive electrode sheet in which the current collector is made of aluminum foil and the active material layer is a positive electrode active material layer. Item 11. The rolling method according to any one of Items 7 to 10. [Explanation of symbols]

[0069] 1 Electrode sheet 2 Current collector foil (current collector) 3 Active material layer 4 Unformed area 10. Rolling equipment 20. Conveyor 21 Winding device 30 Roll press machine 31U, 31D Press Roll 32 Drive unit 40 Warping device 50U, 50D Nip Roll 60U, 60D Dancer Roll 70 Guide Roll 71 Roll body 72 Roll support member (first support member) 72a Bearing part 73 Support wall (second support member) 80 Straightening Roll 81 Correction roll body 82 Roll support member 83 Supporting wall 84 Small diameter section 85 Large diameter section 85L Left large diameter part (second large diameter part) 85R Right large diameter part (first large diameter part) 86L left attachment 86R right attachment 87L Left attachment part 87R Right attachment part 90 Wrap angle adjustment roll

Claims

1. A rolling device that rolls an electrode sheet in which at least one active material layer and at least two unformed portions are alternately arranged along a width direction of a strip-shaped current collector and the unformed portions are arranged at both end portions in the width direction, a conveying device that conveys the electrode sheet in a longitudinal direction along a predetermined conveying path; a pair of press rolls that are arranged on a path along which the electrode sheet is conveyed by the conveying device and that press the active material layer by sandwiching the electrode sheet therebetween; a correction roll that is arranged on the upstream side or downstream side of the pair of press rolls in the conveying path and extends in the width direction of the electrode sheet, The straightening roll is at least one small diameter portion provided at a position corresponding to the active material layer in the width direction of the electrode sheet; a plurality of large diameter portions having an outer diameter larger than that of the small diameter portion, around which the at least two unformed portions are respectively wound, The plurality of large diameter portions are A first large diameter portion; a second large diameter portion having an outer diameter larger than that of the first large diameter portion, Electrode sheet rolling equipment.

2. The straightening roll is disposed upstream of the pair of press rolls. The rolling mill according to claim 1 .

3. a guide roll disposed upstream or downstream of the correction roll in the conveying path and around which the electrode sheet is wound, The guide roll is a roll body extending in the width direction of the electrode sheet; a first support member that rotatably supports the roll body; a second support member that is disposed on one side of the roll body and the first support member in the width direction and supports the first support member, the first support member is supported on one side only by the second support member, the second large diameter portion is disposed on the one side in the width direction relative to the first large diameter portion, The rolling mill according to claim 1 .

4. At least one of the first large diameter portion and the second large diameter portion is configured to have an adjustable outer diameter. The rolling mill according to claim 1 .

5. The straightening roll is a plurality of types of attachments having different outer diameters that configure an outer periphery of at least one of the first large diameter portion and the second large diameter portion; and a mounting portion to which any one of the plurality of types of attachments is mounted.

5. The rolling mill according to claim 4.

6. A method for pressing an active material layer and stretching the unformed portions by a straightening roll while conveying an electrode sheet in which at least one active material layer and at least two unformed portions are alternately arranged along the width direction of a strip-shaped current collector and the unformed portions are arranged at both end portions in the width direction, the method comprising: The straightening roll is at least one small diameter portion provided at a position corresponding to the active material layer in the width direction of the electrode sheet; a plurality of large diameter portions each having an outer diameter larger than that of the small diameter portion, the large diameter portions being provided at positions corresponding to the at least two unformed portions in the width direction of the electrode sheet; the plurality of large diameter portions include a first large diameter portion and a second large diameter portion having an outer diameter larger than that of the first large diameter portion, a step of winding the at least two unformed portions around the plurality of large diameter portions, respectively, and applying tension to the electrode sheet; Electrode sheet rolling method.

7. The rolling method according to claim 6 , wherein the unformed portion is stretched by the straightening roll before the active material layer is pressed.

8. measuring an elongation of the unformed portion stretched by the first large diameter portion and an elongation of the unformed portion stretched by the second large diameter portion; and adjusting an outer diameter of at least one of the first large diameter portion and the second large diameter portion based on the measured elongation of the unformed portion. The rolling method according to claim 6.

9. In the step of adjusting the outer diameter, any one of a plurality of types of attachments having different outer diameters that configure an outer periphery of at least one of the first large diameter portion and the second large diameter portion is attached to the straightening roll. The rolling method according to claim 8.

10. The electrode sheet is a positive electrode sheet in which the current collector is made of aluminum foil and the active material layer is a positive electrode active material layer. The rolling method according to claim 6.

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