Method for manufacturing secondary battery

Abstract

To suppress cracking of a wound electrode body during pressing.SOLUTION: The wound electrode body 10 has long sides, short sides, and curved portions between the long sides and the short sides. The long side is pressed by the long-side jig 30C in a state where the curved portion is held by the curved-portion-side jig 30A, the short side is then pressed by the short-side jig 30C in a state where the curved portion is held by the curved-portion-side jig 30C, and the curved-portion-side jig 30A moves in a direction opposite to a pressing direction so that a load does not become a predetermined value or more when the wound body is pressed by the long-side jig 30B or the short-side jig inner wall.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a secondary battery in which a wound electrode body is pressed from the outside to adjust its outer shape. [Background technology]

[0002] Wound electrode bodies, particularly flat wound electrode bodies with a cross section that is elongated in one direction rather than cylindrical, are known. This flat wound electrode body is formed by overlapping and winding a sheet-shaped positive electrode, a negative electrode, and a separator interposed therebetween into a flat shape. In this case, the end of the longitudinal cross section of the wound electrode body is approximately semicircular (a shape with a curvature radius, called an R-shape), which creates a large dead space between the end and the inner peripheral surface of a rectangular battery case.

[0003] In Patent Document 1, the end of this R-shape is pressed to reduce the radius of curvature of the R-shape, thereby reducing the dead space and improving the volumetric efficiency of the wound electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-50088 Summary of the Invention [Problem to be solved by the invention]

[0005] To reduce the radius of curvature, the wound electrode body is pressed from both the long and short sides. When pressed from two directions in this way, large local shear stresses are generated in the wound electrode body depending on the stress generated when pressing in one direction and the direction of the pressing in the other direction, which may cause cracks. [Means for solving the problem]

[0006] The method for manufacturing a secondary battery according to the present disclosure is a method for manufacturing a secondary battery in which a wound electrode body is pressed from the outside to adjust its external shape, the wound electrode body having long sides, short sides, and a curved portion between the long sides and the short sides, the long sides are pressed with a long side jig while the curved portion is held by a curved portion side jig, and then the short sides are pressed with a short side jig while the curved portion is held by the curved portion side jig, and when the wound electrode body is pressed by the long side side jig or the short side side jig, the curved portion side jig moves in the direction opposite to the pressing direction so that the load does not exceed a predetermined value.

[0007] In addition, the secondary battery manufacturing apparatus according to the present disclosure is a secondary battery manufacturing apparatus that presses a wound electrode body from the outside to shape the exterior, and includes a long side jig that presses the long sides of the wound electrode body, a short side jig that presses the short sides of the wound electrode body, and a curved portion side jig that is located between the long side jig and the short side jig and holds the curved portion of the wound electrode body, wherein the long side side jig presses the long sides while the curved portion side jig holds the curved portion, and the short side side jig presses the short sides while the curved portion side jig holds the curved portion, and when the wound electrode body is pressed by the long side side jig or the short side side jig, the curved portion side jig moves in the direction opposite to the pressing direction so that the load does not exceed a predetermined value. [Effects of the Invention]

[0008] According to the manufacturing method of the secondary battery of the present disclosure, the curved portion side jig can suppress the tension in the curved portion caused by pressing on the long side and reduce the shear stress caused by pressing on the short side, thereby preventing cracking of the wound electrode body. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams showing the configuration of a wound electrode body 10, in which (A) is a perspective view, (B) is a cross-sectional view, and (C) is an enlarged cross-sectional view of a main part. [Figure 2] 10A to 10C are diagrams illustrating a manufacturing process of a wound electrode body according to an embodiment. [Figure 3]FIG. 10 is a diagram showing the state of the wound electrode body 10 after pressing has been completed. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following embodiments do not limit the present disclosure, and configurations formed by selectively combining multiple examples are also included in the present disclosure.

[0011] "Wound electrode body" FIG. 1 shows the configuration of a wound electrode body 10, where (A) is a perspective view, (B) is a cross-sectional view, and (C) is an enlarged cross-sectional view of a main part.

[0012] As shown in (C), the wound electrode body 10 is formed by sandwiching a flat plate-shaped positive electrode 12 between flat plate-shaped separators 14, and then winding the resultant structure with a flat plate-shaped negative electrode 16 superimposed thereon.

[0013] As shown in (A), the cross section of the wound electrode body 10 is a rectangle with two short sides that are arcs (rounded rectangle), and has a flattened, columnar, three-dimensional shape. Electrode terminals 10a and 10b are provided on both ends of the columnar shape of the wound electrode body 10. For example, electrode terminal 10a is connected to the positive electrode 12 and serves as a positive electrode terminal, and electrode terminal 10b is connected to the negative electrode 16 and serves as a negative electrode terminal.

[0014] This wound electrode body 10 is then housed in a box-shaped case 20. (B) shows the side wall of the case 20. As such, the width of the case 20 corresponds to the width of the wound electrode body 10, and the wound electrode body 10 is housed within the case 20 along its side wall. Note that multiple wound electrode bodies 10 may be housed within the case 20.

[0015] As shown in (C), in this example, the separator 14 is on the outermost side, and moving inward from there, the order is positive electrode 12, separator 14, and negative electrode 16. At the corners of the rectangular case 20, gaps are formed between the corners and the outer periphery of the wound electrode body 10. If the gap is large, the volumetric energy efficiency will decrease accordingly, so there is a demand to make the gap as small as possible.

[0016] "Pressure shaping" 2 is a diagram illustrating a manufacturing process of a wound electrode body according to an embodiment, and shows pressing of the portion corresponding to FIG.

[0017] Thus, three types of jigs are provided for pressing the wound electrode body 10: long-side jig 30A corresponding to the long sides, short-side jig 30B corresponding to the short sides, and curved-portion jig 30C corresponding to the corner between them. The long-side jig 30A and short-side jig 30B have pressing directions that differ by 90 degrees, and curved-portion jig 30C is located midway between the two, i.e., its pressing direction differs by 45 degrees from the two.

[0018] Two long side jigs 30A are provided corresponding to the two long sides of the wound electrode body 10, two short side jigs 30B are provided corresponding to the two short sides, and four curved portion jigs 30C are provided corresponding to the four corners.

[0019] The process of press-forming using these three jigs is explained below. First, the three jigs are brought close to their corresponding parts. They can be in contact with each other as long as there is a slight pressure, or they can be slightly apart.

[0020] Next, the curved portion side jig 30C is moved toward the corner (curved portion) of the wound electrode body 10 ahead of the others and pressed with a predetermined pressure (1). The pressure at this time is set to a predetermined, relatively low pressure within a range that does not crush the wound electrode body 10, depending on the compression characteristics of the wound electrode body 10. The pressure can be set to the maximum pressure at which the wound electrode body 10 is not crushed, or a pressure slightly lower. In this state, the long side side jig 30A and the short side side jig 30B do not move and remain in their positions.

[0021] Next, the long side jig 30A is moved toward the long side of the wound electrode body 10 to press the long side (2). The pressure at this time is a pressure that presses the wound electrode body 10 to cause a predetermined deformation, and can be determined in advance by simulation, experiment, etc.

[0022] At this time, the curved portion side jig 30C moves in the opposite direction to the pressing direction while maintaining the pressing force so that the pressing force does not exceed a predetermined value (2). For example, the pressure may be set to the pressure necessary to finally achieve the desired shaping of the corresponding part, and the curved portion side jig 30C may move back while maintaining that pressure. Note that the pressure may be slightly smaller than the final pressure.

[0023] Next, the short side jig 30B is moved toward the short side of the wound electrode body 10 to press the short side (3). At this time, the curved portion side jig 30C moves in the opposite direction to the pressing direction while maintaining the pressing force so that the pressing force does not exceed a predetermined value (3).

[0024] Thus, in this embodiment, when the long-side jig 30A and the short-side jig 30B press the wound electrode body 10, a predetermined pressure is applied obliquely to the corners. This prevents tensile stress from occurring inside the wound electrode body 10 due to movement toward the corners, thereby preventing shearing of the internal laminate. In particular, when the long side is pressed by the long-side jig 30A without the pressing force of the curved portion jig 30C, inward tensile stress is generated at the corners when the pressing is completed. Pressing with the short-side jig 30B applies a shearing force across the tensile-stressed laminate, which is likely to cause shearing in the internal laminate. Pressing with the short-side jig 30B thereafter applies a shearing force to the tensile-stressed laminate, which is likely to cause shearing in the internal laminate.

[0025] In this embodiment, the corners (curved portions) of the wound electrode body 10 are pressed inward by the curved portion side jig 30C, thereby preventing the generation of shearing force.

[0026] 3 is a diagram showing the state of the wound electrode body 10 after pressing has been completed. As shown, the long side jig 30A, the short side jig 30B, and the curved portion jig 30C are in contact with the long sides, short sides, and corners (curved portions) of the wound electrode body 10. Even when these jigs are released, the wound electrode body 10 maintains substantially the same shape.

[0027] In this state, the corners of the wound electrode body 10 are flattened by the curved portion side jig 30C, and the roundness of the corners is corrected, resulting in a polygonal shape as a whole.

[0028] In this way, in this embodiment, by maintaining a predetermined pressure at the corners in the press-shaping process of the wound electrode body 10, it is possible to effectively prevent cracks from occurring in the wound electrode body 10. That is, the curved portion side jig suppresses the generation of tensile stress in the curved portion caused by pressing on the long side, and reduces shear stress caused by pressing on the short side, thereby preventing cracks in the wound electrode body 10. [Explanation of symbols]

[0029] 10 wound electrode body, 12 positive electrode, 14 separator, 16 negative electrode, 20 case, 30A long side jig, 30B short side jig, 30C curved portion side jig.

Claims

[Claim 1] A method for manufacturing a secondary battery in which a wound electrode body is pressed from the outside to adjust its outer shape, the wound electrode body has a long side, a short side, and a curved portion between the long side and the short side, pressing the long side with a long side jig while holding the curved portion with a curved portion side jig; Thereafter, the short side is pressed by the short side jig while the curved portion is held by the curved portion side jig, the curved portion side jig moves in a direction opposite to the pressing direction when the wound electrode body is pressed by the long side side jig or the short side side jig so that the load does not exceed a predetermined value. A method for manufacturing a secondary battery.

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