Method for manufacturing an electricity storage device

Abstract

To achieve an improvement in quality of a power storage device.SOLUTION: There is provided a manufacturing method of a power storage device that includes a flat wound electrode body including a positive electrode, a negative electrode and a separator. The manufacturing method includes a wound body manufacturing step, a first pressing step, and a second pressing step. In the wound body manufacturing step, a wound body including the positive electrode, the negative electrode and the separator is manufactured. In the first pressing step, the wound body is pressed along a first direction that is perpendicular to the winding axis of the wound body. In the second pressing step, the wound body is pressed along a second direction that is perpendicular to the winding axis and that is different from the first direction to the wound body after the first pressing step. The flat wound electrode body is formed in the second pressing step. The flat wound electrode body includes a flat part and a curved part disposed on both end sides of the flat part. In the first pressing step, an area forming the curved part is pressed after the second pressing step.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] International Publication No. 2021 / 060010 discloses a secondary battery containing an electrode assembly. In the secondary battery disclosed in this publication, the electrode assembly has a positive electrode tab group at one end and a negative electrode tab group at the other end. The electrode assembly has a first main surface and a second main surface that are arranged facing each other. The positive electrode tab group is connected to the current collector in a folded state. Tape is attached to the electrode assembly as a fixing means, spanning the first main surface, the current collector, and the second main surface. This configuration is said to increase the power generation section of the electrode assembly, thereby increasing the volumetric energy density of the secondary battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 060010 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors wish to improve the quality of power storage devices. [Means for solving the problem]

[0005] The method for manufacturing an energy storage device disclosed herein is a method for manufacturing an energy storage device including a flat wound electrode body including a positive electrode, a negative electrode, and a separator. The manufacturing method includes a wound body manufacturing process, a first pressing process, and a second pressing process. In the wound body manufacturing process, a wound body including a positive electrode, a negative electrode, and a separator is manufactured. In the first pressing process, the wound body is pressed along a first direction perpendicular to the winding axis of the wound body. In the second pressing process, after the first pressing process, the wound body is pressed along a second direction perpendicular to the winding axis and different from the first direction relative to the wound body. The second pressing process forms a flat wound electrode body. The flat wound electrode body includes a flat portion and curved portions located on both ends of the flat portion. In the first pressing process, the regions that will become the curved portions are pressed after the second pressing process. This manufacturing method enables the manufacture of a high-quality energy storage device. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing the wound body manufacturing process. [Figure 2] FIG. 2 is a schematic diagram showing the wound body manufacturing process. [Figure 3] FIG. 3 is a schematic diagram showing the first pressing step. [Figure 4] FIG. 4 is a schematic diagram showing the deformation process. [Figure 5] FIG. 5 is a schematic diagram showing the second pressing step. [Figure 6] FIG. 6 is a cross-sectional view of the wound electrode body 40. [Figure 7] FIG. 7 is a perspective view schematically showing the electricity storage device 100. As shown in FIG. [Figure 8] FIG. 8 is a schematic vertical cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 9 is a perspective view schematically showing the wound electrode body 40. As shown in FIG. [Figure 10] FIG. 10 is a perspective view showing the wound electrode body 40. As shown in FIG. [Figure 11] FIG. 11 is a perspective view showing the wound electrode body 40 attached to the sealing plate 54. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the technology disclosed herein will be described below with reference to the drawings. The embodiment described herein is, of course, not intended to limit the present invention. The drawings are schematic and do not necessarily reflect the actual product. Furthermore, identical reference numerals are used to designate components and parts that perform the same function, and redundant descriptions will be omitted where appropriate. In the following description, the reference numerals L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the reference numerals X, Y, and Z in the drawings represent the short-side direction, long-side direction, and height direction of the power storage device, respectively. However, these directions are merely used for convenience of description and do not in any way limit the installation form of the power storage device.

[0008] In this specification, the term "electricity storage device" refers to a general electricity storage device capable of extracting electrical energy. Electricity storage devices include secondary batteries that can be repeatedly charged and discharged by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte, as well as capacitors such as electric double layer capacitors. Hereinafter, an embodiment of a method for manufacturing an electricity storage device will be described in which a lithium ion secondary battery is used.

[0009] The method for manufacturing an electricity storage device disclosed herein includes a wound body manufacturing step, a first press step, and a second press step. In this embodiment, a deformation step for deforming the wound body 41 is provided between the first press step and the second press step. FIGS. 1 and 2 are schematic diagrams showing the wound body manufacturing step. FIG. 3 is a schematic diagram showing the first press step. FIG. 4 is a schematic diagram showing the deformation step. FIG. 5 is a schematic diagram showing the second press step. FIG. 6 is a cross-sectional view of the wound electrode body 40. FIG. 6 shows a cross section along a direction perpendicular to the winding axis WL of the wound electrode body 40.

[0010] Here, the electricity storage device is manufactured using an electrode assembly manufacturing apparatus 200. The electrode assembly manufacturing apparatus 200 includes a winding core 210 (see FIGS. 1 and 2), a chuck 220 (see FIG. 2), a first pressing apparatus 230 (see FIG. 3), a deformation jig 240 (see FIG. 4), and a second pressing apparatus 250 (see FIG. 5).

[0011] <Wound body manufacturing process> In the wound body manufacturing process, a wound body 41 including a positive electrode 10, a negative electrode 20, and a separator 30 is manufactured. As shown in FIG. 1, the positive electrode 10, the negative electrode 20, and the separator 30 are wound around a winding core 210. In this embodiment, a strip-shaped positive electrode 10 and a strip-shaped negative electrode 20 are wound with two strip-shaped separators 30a and 30b interposed therebetween. The positive electrode 10, the negative electrode 20, and the separators 30a and 30b are wound on the winding core 210. The positive electrode 10 and the negative electrode 20 are each provided with a tab (positive electrode tab 12t and negative electrode tab 22t in FIG. 11) protruding in the width direction.

[0012] The winding core 210 is a member having a substantially cylindrical shaft shape. The shape of the winding core 210 is not particularly limited, and the cross section may be a perfect circle or a flat shape. The winding core 210 is connected to a driving device (e.g., a motor) not shown, and is driven to rotate. A slit 211 is formed in the winding core 210. The slit 211 is formed in the axial direction and radial direction so as to pass through the central axis of the winding core 210. The position of the slit 211 is not particularly limited.

[0013] In the wound body manufacturing process, first, the leading ends of two separators 30a and 30b are fixed in slits 211 of winding core 210. Separators 30a and 30b are supplied to winding core 210. Separators 30a and 30b may be supplied toward winding core 210 from an unwinding roll (not shown).

[0014] The method for fixing the separators 30a, 30b is not particularly limited, and they may be fixed using a fixing jig such as a clamp, or may be fixed using an electrostatic chuck or the like. The winding core 210 rotates a predetermined angle (for example, about half a revolution) with the two separators 30a, 30b fixed thereto. As a result, the two separators 30a, 30b are wound around the winding core 210 so as to cover the winding core 210 in the circumferential direction. The winding core 210 may have suction holes formed therein for suctioning the separators 30a, 30b.

[0015] Next, the positive electrode 10 and the negative electrode 20 are supplied to the winding core 210. The positive electrode 10 and the negative electrode 20 may be supplied toward the winding core 210 from an unwinding roll (not shown). The positive electrode 10 is sandwiched between a separator 30a supplied toward the winding core 210 and a separator 30b on the winding core 210. The negative electrode 20 is sandwiched between a separator 30b supplied toward the winding core 210 and a separator 30a on the winding core 210. In this state, the winding core 210 is rotated a predetermined number of times. This produces a wound body 41 (see FIG. 2 ) in which the positive electrodes 10 and the negative electrodes 20 are alternately stacked and wound with the separators 30a and 30b interposed therebetween. Note that guide rollers may be provided around the winding core 210 to guide the positive electrode 10, the negative electrode 20, and the separators 30a and 30b. A pressure roller may be provided around the winding core 210 to press the positive electrode 10, the negative electrode 20, and the separators 30a and 30b against the winding core 210.

[0016] The positive electrode 10, the negative electrode 20, and the separators 30a and 30b are wound to form a wound body 41 having a substantially circular cross section (see FIG. 2). As shown in FIG. 2, the shape of the wound body 41 is formed according to the shape of the winding core 210. The shape of the wound body 41 is not particularly limited and may be flat, for example. A tab group T is formed on the side surface (end surface in the winding axis direction) of the wound body 41. The tab group T is a portion where the positive electrode tabs 12t of the positive electrode 10 described above are stacked along the radial direction of the wound body. The tab group T, on which the positive electrode tabs 12t (see FIG. 11) are stacked, protrudes from one side surface of the wound body 41. The tab group T is provided in two locations at the top of the one side surface of the wound body 41. Note that, on the other side surface of the wound body 41, a tab group is formed at a position corresponding to the tab group T, on which the negative electrode tabs 22t (see FIG. 11) are stacked.

[0017] The wound body 41 includes a first region 41a and a second region 41b. The first region 41a is a region that becomes the curved portion 40R (see FIG. 5) of the wound electrode body 40 (see FIG. 5). The second region 41b is a region that becomes the flat portion 40F (see FIG. 5) of the wound electrode body 40. The first region 41a and the second region 41b are provided alternately in two locations in the circumferential direction of the wound body 41. The first region 41a and the second region 41b are set so as to sandwich the winding axis WL of the wound body 41. Here, the first region 41a is set above and below the wound body 41. The positions of the first region 41a and the second region 41b can be set depending on the positions at which the positive electrode 10 and the negative electrode 20 are fixed to the winding core 210 when rotation of the winding core 210 begins. The two tab groups T are arranged above the left and right second regions 41b, with the upper first region 41a sandwiched between them.

[0018] Once the wound body 41 is formed on the winding core 210, the positive electrode 10, the negative electrode 20, and the separators 30a, 30b are cut by a cutter (not shown) and separated from the unwinding roll. Next, the winding core 210 is removed from the wound body 41. When the winding core 210 is removed, the wound body 41 is held by a chuck 220. In this embodiment, the wound body 41 is held by a pair of chucks 220.

[0019] In this embodiment, the chuck 220 clamps the wound body 41 from the inner peripheral surface 41i and the outer peripheral surface 41o of the wound body 41. The chuck 220 has a first portion 221 that contacts the inner peripheral surface 41i of the wound body 41 and a second portion 222 that contacts the outer peripheral surface 41o of the wound body 41. The first portion 221 is a member that is approximately cylindrical in shape. The second portion 222 is a member that presses the outer peripheral surface 41o of the wound body 41. A pair of chucks 220 are provided on the left and right of the wound body 41. The chucks 220 are configured to be movable in the left-right direction.

[0020] When the winding core 210 is removed, a gap may be formed between the inner circumferential surface 41i of the wound body 41 and the outer circumferential surface 212 of the winding core 210. For example, by narrowing the spacing of the slits 211, a gap may be formed between the inner circumferential surface 41i of the wound body 41 and the outer circumferential surface 212 of the winding core 210. The first part 221 of the chuck 220 may be inserted into the gap, and the winding core 210 may be removed while the wound body 41 is being held.

[0021] After the winding core 210 is removed, the pair of chucks 220 then move in the left-right direction. The wound body 41 is deformed into a flat shape. At this time, the first regions 41a can be arranged above and below. The first regions 41a can be arranged between the pair of first portions 221 in the left-right direction. The wound body 41, which has been deformed into a flat shape, is transferred to a first press device 230 (see FIG. 3).

[0022] <First press process> In the first pressing step, as shown in FIG. 3 , the wound body 41 is pressed along a first direction D1 perpendicular to the winding axis WL of the wound body 41. Here, the first direction D1 refers to the direction in which a press pressure is applied to the wound body 41 in the first pressing step. Here, the first direction D1 is set to the vertical direction. The first pressing device 230 includes a lower press plate 231, an upper press plate 232, and a drive device (not shown). The first pressing device 230 may also include a pressure gauge that detects the press pressure and a control device that controls the press pressure. The wound body 41 is placed on the lower press plate 231. The upper press plate 232 is positioned above the lower press plate 231 so as to face the lower press plate 231. The drive device presses the wound body 41 by driving at least one of the lower press plate 231 and the upper press plate 232.

[0023] In the first pressing step, the dimensions of the wound body 41 are reduced in the first direction D1 of the wound body 41. The wound body 41 is sandwiched and pressed between the lower press plate 231 and the upper press plate 232 of the first press device 230. In the first pressing step, the region that will become the curved portion 40R (see FIG. 5) after the second pressing step described below is pressed. When the wound body 41 is pressed, the first region 41a that will become the curved portion 40R of the wound electrode body 40 may be positioned so as to contact, for example, one of the lower press plate 231 and the upper press plate 232. From the viewpoint of stabilizing the shape of the wound body 41 to be manufactured, it is preferable that the first region 41a of the wound body 41 be positioned approximately in the center of the wound body 41 in the left-right direction. In this case, the first regions 41a may face each other in the first direction during pressing. The position of the first region 41a can be adjusted by controlling the winding positions of the positive electrode 10, the negative electrode 20, and the separator 30 relative to the winding core 210 during the wound body manufacturing process, or by controlling the movement of the chuck 220 when deforming the wound body 41.

[0024] The pressing pressure in the first pressing step is not particularly limited. The pressing pressure is preferably set to a level at which a gap O is formed on the inner circumferential surface 41i of the wound body 41 after pressing due to so-called springback. In this case, when the press in the first pressing step is released after the first pressing step, a gap O is formed at the winding center (inner circumferential surface 41i) of the wound body 41. The cross section (plane perpendicular to the winding axis WL) of the gap O may be, for example, elliptical. A gap O having a height (length in the first direction D1) of 4 mm or more is preferably formed on the inner circumferential surface 41i of the wound body 41 after pressing, and a gap O of 8 mm or more is more preferably formed. Forming the gap O on the inner circumferential surface 41i of the wound body 41 can improve workability, such as making it easier to insert a jig in a later step or to expand the gap O so that a jig 240 (see FIG. 4) can be inserted.

[0025] The pressing pressure is not particularly limited and can be set appropriately depending on the configuration of the wound body 41. For example, when adhesive layers are provided at the interfaces between the positive electrode 10, the negative electrode 20, and the separator 30, the pressing pressure can be set lower than when adhesive layers are provided. The pressing pressure can also be set appropriately depending on, for example, the number of turns, dimensions, material, etc. of the wound body 41.

[0026] The pressing pressure in the first pressing step is preferably smaller than the pressing pressure in the second pressing step described below. This allows the load on the positive electrode 10 and the negative electrode 20 to be kept low. Furthermore, deformation of the wound body 41 is kept relatively small, which can improve workability. The pressing pressure in the first pressing step is preferably 1 / 100 times or more, and more preferably 1 / 10 times or more, of the pressing pressure in the second pressing step. The pressing pressure in the first pressing step is preferably 1 / 2 times or less, and more preferably 1 / 3 times or less, of the pressing pressure in the second pressing step.

[0027] In the first press step, the wound body 41 may be pressed while being heated. Heating the wound body 41 makes the wound body 41 more likely to deform. This allows the press pressure when pressing the wound body 41 to be reduced. Furthermore, if an adhesive layer is provided at the interface of the separator 30, the heat may change the adhesive layer, improving adhesion. When the wound body 41 is heated, the press pressure in the first press step may be set lower than when the wound body 41 is not heated. The wound body 41 may be heated by heating the lower press plate 231 and the upper press plate 232.

[0028] In this embodiment, the wound body 41 pressed in the first press step is deformed in the deformation step. The wound body 41 pressed in the first press step may be deformed by a deformation jig (hereinafter also simply referred to as a "jig") 240.

[0029] <Transformation process> In the deformation process, the wound body 41 after the first press process is deformed. In the deformation process, the flattening direction of the wound body 41 is changed. For example, the wound body 41 may be deformed so that the portion that was the major axis after the first press process becomes the minor axis, and the portion that was the minor axis becomes the major axis. The deformation method is not particularly limited, but as shown in FIG. 4, it is preferable to insert a pair of jigs 240 into the gap O of the wound body 41 to deform the wound body 41. In this embodiment, the pair of jigs 240 may be elongated, axial members. Each of the pair of jigs 240 may have a length approximately equal to the length of the wound body 41 along the winding axis WL (the long positive electrode 10, negative electrode 20, and separator 30). Having the pair of jigs 240 approximately equal to the length of the wound body 41 along the winding axis WL makes it easier to uniformly deform the wound body 41. The pair of jigs 240 may be disposed between the first regions 41a of the wound body 41. The pair of jigs 240 may be arranged above and below the gap O.

[0030] In the deformation process, the wound body 41 may be rotated by a rotation device (not shown) with the jig 240 inserted therethrough. In this embodiment, the wound body 41 is rotated 90 degrees by the rotation device. Accordingly, the first direction D1 of the wound body 41 is oriented in the left-right direction. The first regions 41a of the wound body 41 are arranged on the left and right. The position of the jig 240 may move in conjunction with the rotation of the wound body 41. In this embodiment, the pair of jigs 240 are arranged side by side on the left and right (first direction D1), similar to the first regions 41a.

[0031] Next, the gap between a pair of jigs 240 arranged at the center of the winding of the wound body 41 is widened to spread the wound body 41 and deform the wound body 41. At this time, it is preferable that the cross-sectional shape of the elliptical gap O has a major axis and a minor axis, and the minor axis portion is spread by the pair of jigs 240. In this embodiment, the pair of jigs 240 move in the left-right direction (first direction D1 of the wound body 41), and the wound body 41 is spread left and right. The wound body 41 is deformed and deformed into a flat shape such that the first direction D1 of the wound body 41 becomes the major axis. By arranging the first region 41a, which becomes the curved portion 40R of the wound electrode body 40 (see FIG. 5), at both ends on the major axis, the positional accuracy of the wound body 41 when pressed in the second pressing step can be improved. As a result, the quality of the wound electrode body 40 can be improved.

[0032] At this time, the first regions 41a move outward following the deformation of the wound body 41, and are separated from each other. The second regions 41b are stretched, and the pair of second regions 41b approach each other. Accordingly, the two tab groups T are positioned so that they overlap in the vertical direction. This can improve the positional accuracy of the positive electrode tab 12t and the negative electrode tab 22t (see FIG. 11).

[0033] The wound body 41 deformed after the first press step is transferred to a second press device 250 (see FIG. 5). Here, by providing a deformation step for deforming the wound body 41 between the first press step and the second press step, the positional accuracy of the portion of the wound body 41 that is pressed during the second press can be improved.

[0034] <Second pressing process> The second pressing step is performed after the first pressing step. As shown in FIG. 5 , in the second pressing step, the wound body 41 is pressed along a second direction D2 that is perpendicular to the winding axis WL and is a direction different from the first direction D1 relative to the wound body 41. Here, the second direction D2 refers to the direction in which a press pressure is applied to the wound body 41 in the second pressing step. The first direction D1 and the second direction D2 refer to directions set around the winding axis WL of the wound body 41. The second direction D2 may be set in a different direction around the winding axis WL of the wound body 41, based on the direction in which the wound body 41 was pressed in the first pressing step. For example, if the orientation of the wound body 41 is rotated around the winding axis WL after the first pressing step, the first direction D1 also rotates in conjunction with the rotation of the wound body 41. In this embodiment, since the wound body 41 is rotated 90 degrees with respect to the winding axis WL after the first press process, the first direction D1, which was set to the up-down direction in the first press process, is set to the left-right direction in the second press process.

[0035] Here, the second direction D2 is set to a vertical direction different from the first direction D1 (left-right direction). The second press device 250 includes a lower press plate 251, an upper press plate 252, and a drive device (not shown). The second press device 250 may also include a pressure gauge that detects the press pressure and a control device that controls the press pressure. The wound body 41 is placed on the lower press plate 251. The upper press plate 252 is disposed above the lower press plate 251 so as to face the lower press plate 251. The drive device presses the wound body 41 by driving at least one of the lower press plate 251 and the upper press plate 252.

[0036] The wound body 41 is sandwiched and pressed between the lower press plate 251 and the upper press plate 252 of the second press device 250, with the first region 41a, which will become the curved portion 40R of the wound electrode body 40, positioned on the outside in the left-right direction. In the second press process, the second region 41b, which will become the flat portion 40F of the wound electrode body 40, is sandwiched and pressed between the lower press plate 251 and the upper press plate 252. At this time, pressure is applied to the second region 41b. As described above, the first direction D1 of the wound body 41 after the deformation process is set to the left-right direction. In the second press process, the dimension of the wound body 41 is reduced in the second direction D2 of the wound body 41. A flat wound electrode body 40 is formed by the second press process. In this case, the second region 41b that becomes the curved portion 40R is preferably located between the surface where the wound body 41 and the lower press plate 251 contact and the surface where the wound body 41 and the upper press plate 252 contact.

[0037] The pressing pressure is preferably set to a level that crushes and forms the gap O (see FIG. 4) on the inner circumferential surface 41i of the wound body 41. The pressing pressure in the second pressing step is not particularly limited. For example, when an adhesive layer is provided at the interface between the positive electrode 10, the negative electrode 20, and the separator 30 (see FIG. 1), the pressing pressure in the second pressing step can be set to a lower pressing pressure than when no adhesive layer is provided. The pressing pressure can be set appropriately depending on, for example, the number of turns, dimensions, material, etc. of the wound body 41.

[0038] In the second press step, the wound body 41 may be pressed while being heated, as in the first press step. Heating the wound body 41 makes the wound body 41 more likely to deform. This allows the press pressure when pressing the wound body 41 to be reduced. Furthermore, if an adhesive layer is provided at the interface of the separator 30, the heat may change the adhesive layer, improving adhesion. When the wound body 41 is heated, the press pressure in the second press step may be set lower than when the wound body 41 is not heated. The wound body 41 may be heated by heating the lower press plate 251 and the upper press plate 252.

[0039] The first press step and the second press step may be performed by different press devices (in this embodiment, the first press device 230 and the second press device 250), or may be performed by the same press device.

[0040] As described above, a flat wound electrode body 40 is manufactured. As shown in FIG. 6, the flat wound electrode body 40 includes a flat portion 40F and a curved portion 40R. In this embodiment, the portion pressed by the upper press plate 252 and the lower press plate 251 becomes the flat portion 40F. The portion not pressed by the upper press plate 252 and the lower press plate 251 becomes the curved portion 40R. The curved portions 40R are located on both end sides of the flat portion 40F.

[0041] The flat portion 40F connects the pair of curved portions 40R. The flat portion 40F is a portion where the outer peripheral surface of the wound electrode body 40 is formed to be approximately flat. The flat portion 40F is formed by stacking the positive electrode 10 and the negative electrode 20 in the thickness direction with the separator 30 interposed therebetween. In the flat portion 40F, the positive electrode 10 and the negative electrode 20 contact the separator 30 adjacent in the thickness direction. Note that slight steps or irregularities may be formed on the outer surface of the flat portion 40F.

[0042] The curved portion 40R is a portion where the outer peripheral surface of the wound electrode body 40 is curved. In the curved portion 40R, curved positive electrodes 10 and negative electrodes 20 are alternately arranged with separators 30 interposed between them, from the inside to the outside of the wound electrode body 40. The positive electrodes 10 and negative electrodes 20 may be in contact with the separators 30. A gap d may be formed between the separators 30 and the positive electrodes 10 and negative electrodes 20.

[0043] After the wound electrode body 40 is manufactured, it is then housed in a case, sealed, and an electrolyte is poured into it using a known method to prepare an assembly. The assembly is subjected to an initial charging process and an aging process using a known method, and the electricity storage device 100 (see FIGS. 7 and 8) can be manufactured.

[0044] The flat and curved portions of the electrode assembly are formed by pressing the wound assembly in a predetermined direction. When the wound assembly is pressed, flat portions are formed in the pressed portions along the thickness direction. Curved portions are formed in portions of the wound assembly other than the pressed portions. In the flat portions, the positive electrode and negative electrode are in contact with the separator adjacent to them in the thickness direction. However, when the wound assembly is pressed, the positive electrode, negative electrode, and separator are bent more significantly as the flat portions are pressed, forming curved portions. In other words, when the wound assembly is pressed, the curvatures of the positive electrode, negative electrode, and separator increase, forming curved portions. According to the inventor's findings, the degree of bending of the positive electrode, negative electrode, and separator during pressing can vary depending on the position. Therefore, in the curved portions, the distance between the positive electrode and negative electrode can vary depending on the position of the curved portion. For example, the distance between the positive electrode and negative electrode can vary depending on the distance from the center of the electrode assembly. Furthermore, according to the inventors' findings, in the process of manufacturing an energy storage device after manufacturing an electrode assembly, when the electrode assembly is subjected to treatments such as drying and high-temperature aging, the variation in the distance between adjacent positive and negative electrodes separated by a separator may increase. When an electrode assembly having a large variation in the distance between adjacent positive and negative electrodes separated by a separator is used in an energy storage device, the quality of the energy storage device may be easily degraded. For example, as the energy storage device is charged and discharged, lithium may be locally deposited on the negative electrode, which may easily reduce the capacity.

[0045] In the embodiment described above, the region that will become the curved portion 40R after the second press process (in this embodiment, the second region 41b) is pressed in the first press process. In other words, before the shape of the wound electrode body 40 is determined in the second press process, the second region 41b is pressed in advance in the first press process. The positive electrode 10 and the negative electrode 20 in the second region 41b come into contact once with the separator 30 adjacent to them in the press direction. This makes it easier to align the flatness of the positive electrode 10, the negative electrode 20, and the separator 30 in the second region 41b. Furthermore, even if the electrode plate is partially wavy in the second region 41b or has partially different flatness, the flatness of the positive electrode 10, the negative electrode 20, and the separator 30 is easily aligned. Therefore, when the curved portion 40R is formed in the second press process, the distance (gap d) between the adjacent positive electrode 10 and negative electrode 20 separated by the separator 30 is less likely to vary. This can prevent localized absorption and release of lithium, which in turn makes it easier to maintain the quality of the electricity storage device 100 (see FIGS. 7 and 8) that uses the wound electrode body 40, for example, by making it easier to prevent localized deposition of lithium in the wound electrode body 40.

[0046] The manufacturing method of the energy storage device disclosed herein can be modified in various ways. For example, the first pressing step is not limited to the above-described embodiment. In the first pressing step, the wound body 41 may be pressed with a pressure that does not create a gap O. Pressure may be applied to the pressed wound body 41 so that a gap O is formed on the inner circumferential surface of the wound body 41, and then the jig 240 may be inserted into the gap O. Alternatively, the first pressing step may be performed with the jig 240 (see FIG. 4) inserted into the gap of the wound body 41 (FIG. 2) after winding in advance. In this case, the pressing position or the shape of the pressing plate may be appropriately adjusted, for example, by providing a groove in the pressing plate, so that strong pressure is not applied to the position where the jig 240 is inserted.

[0047] In the above-described embodiment, pressing is performed in the same direction (vertical direction) in the first pressing step and the second pressing step. This is not a limitation, and the pressing directions may be set such that the wound body 41 is pressed in different directions in the first pressing step and the second pressing step. For example, in the first pressing step, a first pressing device capable of pressing in the horizontal direction is used to press the wound body 41 in the horizontal direction so that the vertical direction is the long axis. Thereafter, in the first pressing step, the wound body 41 may be pressed in the vertical direction without rotating the wound body 41. In this embodiment, rotation of the wound body 41 in the deformation step is not necessary.

[0048] The method for manufacturing an electricity storage device disclosed herein produces an electricity storage device 100 (see FIGS. 7 and 8) that includes a flat wound electrode body 40 that includes a positive electrode 10, a negative electrode 20, and a separator 30. An example of an electricity storage device manufactured according to the method for manufacturing an electricity storage device disclosed herein will now be described.

[0049] Fig. 7 is a perspective view schematically showing the energy storage device 100. Fig. 8 is a schematic longitudinal cross-sectional view taken along line VIII-VIII in Fig. 7. Fig. 9 is a perspective view schematically showing the wound electrode body 40. Fig. 10 is a perspective view showing the wound electrode body 40. Fig. 11 is a perspective view showing the wound electrode body 40 attached to a sealing plate 54.

[0050] <Electricity storage device 100> As shown in FIG. 8, the electricity storage device 100 includes a wound electrode body 40 and a case 50 that houses the wound electrode body 40.

[0051] Case 50 The case 50 (see FIGS. 7 and 8 ) houses the wound electrode body 40. Any conventionally known material can be used for the case 50 without any particular restrictions. The case 50 may be made of, for example, a metal. Examples of materials for the case 50 include aluminum, aluminum alloys, iron, and iron alloys. While not particularly limited, the case 50 is preferably made of aluminum or an aluminum alloy. The case 50 includes an exterior body 52 and a sealing plate 54. The exterior body 52 includes a bottom wall 52a that is substantially rectangular in plan view, a pair of first side walls 52b extending upward in the height direction Z from the long sides of the bottom wall 52a, and a pair of second side walls 52c extending upward in the height direction Z from the short sides of the bottom wall 52a (see FIG. 7 ). An opening 52h is formed in the upper part of the exterior body 52.

[0052] The sealing plate 54 is a plate-like member that is substantially rectangular in plan view. The sealing plate 54 is a member that closes the opening 52h of the exterior body 52. ​​The sealing plate 54 is provided with a liquid inlet 55 and a gas exhaust valve 57. The liquid inlet 55 is a through-hole provided for injecting an electrolyte (not shown) into the inside of the case 50. Once the injection of the electrolyte is complete, the liquid inlet 55 is sealed with a sealing member 56. The gas exhaust valve 57 is a thin-walled portion designed to rupture (open) when a large amount of gas is generated inside the case 50 and to exhaust the gas. The sealing plate 54 is formed with terminal insertion holes 58 and 59 to which a positive electrode terminal 60 and a negative electrode terminal 65 are respectively attached. The terminal insertion holes 58 and 59 are each formed at an end of the sealing plate 54 in the width direction Y.

[0053] The positive electrode terminal 60 and the negative electrode terminal 65 are attached to the ends of the sealing plate 54 in the width direction Y of the electricity storage device 100. The positive electrode terminal 60 is connected to a plate-shaped positive electrode external conductive member 62 on the outside of the case 50. The negative electrode terminal 65 is connected to a plate-shaped negative electrode external conductive member 67 on the outside of the case 50. The positive electrode external conductive member 62 and the negative electrode external conductive member 67 are connected to other electricity storage devices or external devices via external connection members (such as bus bars).

[0054] A positive electrode first current collecting portion 71 and a negative electrode first current collecting portion 76 are attached to the inner surface of the sealing plate 54. The positive electrode first current collecting portion 71 and the negative electrode first current collecting portion 76 are each a plate-shaped conductive member extending along the inner surface of the sealing plate 54. A lower end portion 60c of the positive electrode terminal 60 is connected to the positive electrode first current collecting portion 71. A lower end portion 65c of the negative electrode terminal 65 is connected to the negative electrode first current collecting portion 76.

[0055] The sealing plate 54 is provided with various insulating members that prevent electrical conduction between the case 50 (exterior body 52, sealing plate 54) and the electrode terminals (positive electrode terminal 60, negative electrode terminal 65). Gaskets 90 that prevent electrical conduction between the electrode terminals and the sealing plate 54 are attached to the terminal insertion holes 58, 59 of the sealing plate 54. An external insulating member 92 is disposed between the positive electrode external conductive member 62 (or the negative electrode external conductive member 67) and the outer surface of the sealing plate 54. An internal insulating member 94 is disposed between the positive electrode first current collecting portion 71 (or the negative electrode first current collecting portion 76) and the inner surface of the sealing plate 54. The internal insulating member 94 has a plate-shaped base portion 94a attached to the inner surface of the sealing plate 54. The internal insulating member 94 has a protrusion portion 94b that protrudes from the base portion 94a toward the wound electrode body 40. The protrusion 94b restricts the vertical movement of the wound electrode body 40 and prevents direct contact between the wound electrode body 40 and the sealing plate 54. The material of the insulating member described above is not particularly limited as long as it has a predetermined insulating property. Synthetic resin materials such as polyolefin resins and fluorine-based resins can be used as the insulating member.

[0056] <Wound electrode body 40> As shown in FIG. 9, the wound electrode body 40 is a flat electrode body in which a strip-shaped positive electrode 10 and a strip-shaped negative electrode 20 are wound with a strip-shaped separator 30 interposed therebetween.

[0057] <Positive electrode 10> The positive electrode 10 is a long, strip-shaped member. The positive electrode 10 includes a positive electrode core 12, which is a foil-shaped metal member, and a positive electrode active material layer 14 formed on the surface of the positive electrode core 12. From the viewpoint of battery performance, the positive electrode active material layer 14 is preferably formed on both sides of the positive electrode core 12. One side edge of the positive electrode 10 is provided with a positive electrode tab 12t that protrudes outward in the Y direction (to the left in FIG. 9 ). A plurality of positive electrode tabs 12t are provided at predetermined intervals in the longitudinal direction of the positive electrode 10. The positive electrode tabs 12t are regions where the positive electrode active material layer 14 and protective layer 16 are not formed, and the positive electrode core 12 is exposed. A metal material having a predetermined conductivity is preferably used as the positive electrode core 12. The positive electrode core 12 is preferably made of, for example, aluminum or an aluminum alloy.

[0058] The positive electrode active material layer 14 is a layer containing a positive electrode active material. The positive electrode active material is a material that can reversibly absorb and release charge carriers in relation to the negative electrode active material described below. The positive electrode active material is not particularly limited. For example, a lithium transition metal composite oxide is preferably used as the positive electrode active material.

[0059] The positive electrode active material layer 14 may contain additives other than the positive electrode active material. The positive electrode active material layer 14 may contain a binder. A resin binder is preferably used as the binder. For example, polyvinylidene fluoride (PVDF) or the like is preferably used as the resin binder. The positive electrode active material layer 14 preferably contains a conductive material. A carbon material such as acetylene black (AB) is preferably used as the conductive material.

[0060] The density of the positive electrode active material layer 14 is not particularly limited, but the effects of the present invention are more pronounced when the density of the positive electrode active material layer 14 is high (for example, 3.0 g / cm 3 This effect can also be favorably exhibited in cases where the density of the positive electrode active material layer 14 is high or more. When the density of the positive electrode active material layer 14 is high, the positive electrode 10 as a whole is strongly compressed. In this case, high stress is likely to be applied to the positive electrode 10, which may cause the positive electrode 10 to deform. Even in such a case, deformation of the positive electrode 10 is likely to be suppressed in the first pressing step, and the gap between the electrode plates is likely to be stabilized.

[0061] A protective layer 16 may be provided on one side edge of the positive electrode 10, if necessary. The protective layer 16 is a layer configured to have lower electrical conductivity than the positive electrode active material layer 14. The protective layer 16 is provided on the positive electrode core 12 at a position facing the negative electrode active material layer 24 with the separator 30 interposed therebetween. The configuration of the protective layer 16 is not particularly limited, and may be, for example, a layer coated with a resin or a layer containing inorganic particles or a binder.

[0062] <Negative electrode 20> The negative electrode 20 is a long, strip-shaped member. The negative electrode 20 includes a negative electrode core 22, which is a foil-shaped metal member, and a negative electrode active material layer 24 formed on the surface of the negative electrode core 22. From the viewpoint of battery performance, the negative electrode active material layer 24 is preferably formed on both sides of the negative electrode core 22. A negative electrode tab 22t protruding outward in the Y direction (to the right in FIG. 9 ) is provided on one side edge of the negative electrode 20. The negative electrode tab 22t protrudes toward the opposite side from the positive electrode tab 12t. A plurality of negative electrode tabs 22t are provided at predetermined intervals in the longitudinal direction of the negative electrode 20. The negative electrode tabs 22t are regions where the negative electrode active material layer 24 is not formed and where the negative electrode core 22 is exposed. A metal material having a predetermined conductivity is preferably used as the negative electrode core 22. The negative electrode core 22 is preferably made of, for example, copper or a copper alloy.

[0063] The negative electrode active material layer 24 is a layer containing a negative electrode active material. The negative electrode active material is a material that can reversibly absorb and release charge carriers in relation to the positive electrode active material. The negative electrode active material is not particularly limited. For example, carbon materials, silicon-based materials, and mixed oxides thereof are preferably used as the negative electrode active material. For example, graphite, hard carbon, soft carbon, amorphous carbon, etc. can be used as the carbon material. For example, silicon, silicon oxide (silica), etc. can be used as the silicon-based material.

[0064] The negative electrode active material layer 24 may contain an additive other than the negative electrode active material. The negative electrode active material layer 24 may contain a binder as an additive. A resin binder is preferably used as the binder. The resin binder may contain, for example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), or the like. The negative electrode active material layer 24 preferably contains a conductive material. Carbon materials such as acetylene black (AB) and carbon nanotubes can be preferably used as the conductive material.

[0065] The density of the negative electrode active material layer 24 is not particularly limited. However, similar to the positive electrode active material layer 14, the effect of the present invention is more pronounced when the density of the negative electrode active material layer 24 is high (for example, 1.45 g / cm 3 The effect can be favorably exhibited even when the above condition is met.

[0066] Although not particularly limited, the effects of the present invention can be favorably exhibited even when the electrode plates (positive electrode 10 and negative electrode 20) constituting the wound electrode body 40 are large in width (for example, the width of the electrode plates may be 200 mm or more, or may be 250 mm or more). A compressed active material layer is formed on the surface of the electrode plate. The compressed active material layer applies stress to the electrode plate, which may cause the electrode plate to deform. The larger the width of the electrode plate, the greater the likelihood of deformation of the electrode plate. Also, for the same reason, when the wound electrode body 40 is wide (for example, when the ratio (aspect ratio) of the dimension in the direction of the winding axis WL (see FIG. 9) to the dimension in the height direction is 2 or more), the electrode plate is likely to deform significantly. By preparing the wound electrode body 40 using the method disclosed herein, the spacing between the electrode plates is likely to be stable.

[0067] <Separator 30> The separator 30 is a long, strip-shaped member that prevents contact between the positive electrode 10 and the negative electrode 20 and allows charge carriers to pass through. The width of the separator 30 can be set to a dimension that can cover the positive electrode active material layer 14 of the positive electrode 10 and the negative electrode active material layer 24 of the negative electrode 20.

[0068] A porous resin film having a plurality of fine pores through which charge carriers can pass is preferably used as the separator 30. Examples of the separator 30 include porous sheets (films) made of resins such as polyolefins, such as polyethylene (PE) and polypropylene (PP), and polyamides. Such porous sheets may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer).

[0069] A heat-resistant layer may be formed on the resin sheet that constitutes the separator 30. The heat-resistant layer is a layer that has excellent heat resistance. The heat-resistant layer preferably contains ceramic particles and a binder. The ceramic particles may be, for example, alumina.

[0070] The separator 30 may include an adhesive layer. The adhesive layer is a layer that has excellent adhesive properties with the electrode plates (positive electrode 10, negative electrode 20). The adhesive layer bonds the positive electrode 10 to the separator 30, and bonds the negative electrode 20 to the separator 30. It is preferable that the adhesive layer bonds at least one of the positive electrode 10 to the separator 30 and the negative electrode 20 to the separator 30. This configuration makes it easier to bond the positive electrode 10 and the negative electrode 20 to the separator 30 with a small force. As a result, the distance d (see FIG. 6) between the positive electrode 10 and the negative electrode 20 via the separator 30 becomes more stable, which makes it easier to suppress localized deterioration of the wound electrode body 40 described above. The separator 30 does not necessarily have to include an adhesive layer.

[0071] Known materials can be used for the adhesive layer. A resin material may be used for the adhesive layer. The adhesive layer may contain a binder such as polyvinylidene fluoride. The adhesive layer may contain ceramic particles. For example, an adhesive layer that generates adhesive strength through pressure, heat, or the like may be used. The adhesive layer is preferably formed on the surface of the resin sheet that constitutes the separator 30. However, the adhesive layer is not limited to this form, and may be formed on the surfaces of the positive electrode 10 and the negative electrode 20.

[0072] The separator 30 may have a laminated structure with an adhesive layer. The separator 30 may be configured, for example, by laminating substrates made of multiple layers (for example, two layers) of polyolefin porous films with adhesive layers interposed therebetween. At least one surface of the separator 30 may include a heat-resistant layer containing a filler and a binder, and an adhesive layer formed on the surface of the heat-resistant layer.

[0073] A positive electrode tab group 42 and a negative electrode tab group 44 protrude from the wound electrode body 40 along the winding axis WL. The positive electrode tab group 42 and the negative electrode tab group 44 protrude in opposite directions from different sides. As shown in FIG. 10 , a positive electrode second current collecting portion 72 and a negative electrode second current collecting portion 77 are connected to the positive electrode tab group 42 and the negative electrode tab group 44, respectively. As shown in FIG. 11 , the positive electrode tab group 42 is bent and connected to the sealing plate 54 via the positive electrode first current collecting portion 71 and the positive electrode second current collecting portion 72. Similarly, the negative electrode tab group 44 is bent and connected to the sealing plate 54 via the negative electrode first current collecting portion 76 and the negative electrode second current collecting portion 77. The positive electrode first current collecting portion 71 and the positive electrode second current collecting portion 72 constitute a positive electrode current collecting portion 70 , and the negative electrode first current collecting portion 76 and the negative electrode second current collecting portion 77 constitute a negative electrode current collecting portion 75 .

[0074] In this embodiment, three wound electrode bodies 40 are housed in a case 50 (see FIG. 8) in a state where they are attached to a sealing plate 54. The number of wound electrode bodies 40 housed in the case 50 is not particularly limited.

[0075] The technology disclosed herein has been described in various ways. Unless otherwise specified, the embodiments and the like described herein do not limit the present invention. Furthermore, the technology disclosed herein can be modified in various ways, and as long as no particular problems arise, each component and each process described herein can be omitted or combined as appropriate. Furthermore, this specification includes the disclosures described in the following sections.

[0076] Section 1: A method for manufacturing an electricity storage device including a flat wound electrode body including a positive electrode, a negative electrode, and a separator, comprising: a wound body manufacturing step of manufacturing a wound body including the positive electrode, the negative electrode, and the separator; a first pressing step of pressing the wound body along a first direction perpendicular to the winding axis of the wound body; a second pressing step of pressing the wound body in a second direction perpendicular to the winding axis and different from the first direction with respect to the wound body after the first pressing step; Equipped with The flat wound electrode body is formed by the second pressing step, the flat wound electrode body includes a flat portion and curved portions disposed on both end sides of the flat portion, A region that will become the curved portion after the second press process is pressed in the first press process. A method for manufacturing an electricity storage device.

[0077] Section 2: Item 2. The method for producing an electricity storage device according to Item 1, wherein at least one of the positive electrode and the separator and the negative electrode and the separator is bonded by an adhesive layer.

[0078] Section 3: Item 3. The method for manufacturing an electricity storage device according to item 1 or 2, further comprising a deformation step of deforming the wound body between the first pressing step and the second pressing step.

[0079] Section 4: Item 4. The method for manufacturing an energy storage device according to Item 3, wherein in the deformation step, the wound body is deformed by expanding the gap between a pair of jigs arranged at the winding center of the wound body to push the wound body apart.

[0080] Section 5: 5. The method for manufacturing an electricity storage device according to any one of items 1 to 4, wherein, after the first pressing step, when the press in the first pressing step is released, a gap is generated at the center of the winding of the wound body.

[0081] Item 6: 6. The method for manufacturing an electricity storage device according to any one of items 1 to 5, wherein the pressing pressure in the first pressing step is lower than the pressing pressure in the second pressing step. [Explanation of symbols]

[0082] 10 positive electrode 12 Positive electrode core 12t positive electrode tab 14 Cathode active material layer 16 Protective layer 20 negative electrode 22 Negative electrode core 22t negative electrode tab 24 Negative electrode active material layer 30, 30a, 30b Separator 40 Wound electrode body 40F flat area 40R curved section 41 Winding body 41i Inner surface 41o Outer surface 42 Positive electrode tab group 44 Negative electrode tab group 50 cases 52 Exterior body 54 Sealing plate 70 Positive electrode current collector 75 Negative electrode current collector 100 Electricity storage device 200 Electrode body manufacturing equipment 210 Core 211 Slit 212 Outer surface 220 Chuck 221 Part 1 222 Part 2 230 First Pressing Device 231 Lower press plate 232 Upper press plate 240 Deformation jig (jig) 250 Second press device 251 Lower press plate 252 Upper press plate d-spacing D1 1st direction D2 2nd direction O Gap T Tabs WL winding shaft

Claims

1. A method for manufacturing an electricity storage device including a flat wound electrode body including a positive electrode, a negative electrode, and a separator, comprising: a wound body manufacturing step of manufacturing a wound body including the positive electrode, the negative electrode, and the separator; a first pressing step of pressing the wound body along a first direction perpendicular to a winding axis of the wound body; a second pressing step of pressing the wound body in a second direction perpendicular to the winding axis and different from the first direction with respect to the wound body after the first pressing step; Equipped with The flat wound electrode body is formed by the second pressing step, the flat wound electrode body includes a flat portion and curved portions disposed on both end sides of the flat portion, A region that will become the curved portion after the second press process is pressed in the first press process. A method for manufacturing an electricity storage device.

2. The method for manufacturing an electricity storage device according to claim 1 , wherein at least one of the positive electrode and the separator and the negative electrode and the separator is bonded by an adhesive layer.

3. The method for manufacturing an electricity storage device according to claim 1 , further comprising a deformation step of deforming the wound body between the first press step and the second press step.

4. The method for manufacturing an energy storage device according to claim 3 , wherein in the deformation step, the wound body is deformed by expanding a gap between a pair of jigs arranged at a winding center of the wound body to push the wound body apart.

5. The method for manufacturing an electricity storage device according to claim 1 or 2, wherein a gap is generated at the center of the wound body when the press in the first press step is released after the first press step.

6. The method for manufacturing an electricity storage device according to claim 1 , wherein a pressing pressure in the first pressing step is lower than a pressing pressure in the second pressing step.

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