Secondary battery manufacturing method and secondary battery

Abstract

To provide a manufacturing method for a secondary battery, in which a deviation in a stacking position between positive and negative electrodes and a separator in a laminate type electrode body is suppressed.SOLUTION: A manufacturing method for a secondary battery disclosed herein is a manufacturing method for a secondary battery including a laminate type electrode body 20 in which a positive electrode 50 and a negative electrode 60 are stacked through a band-shaped separator 70, and includes a stacking step of stacking the separator 70 in a zig-zag shape so that a planar part 71 and a bent part 72 are alternately provided in a longitudinal direction X of the band-shaped separator 70. The stacking step includes at least a first bending process of forming a first bent part 72a, a first cutting process of cutting at least a part of the formed first bent part 72a in a width direction Y that is orthogonal to the longitudinal direction X of the separator 70, and a second bending process of forming a second bent part 72b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a secondary battery and a secondary battery. [Background technology]

[0002] In recent years, secondary batteries (e.g., lithium ion secondary batteries) have been suitably used as portable power sources for personal computers, mobile terminals, and the like, and as driving power sources mounted on vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs).

[0003] Such a secondary battery is constructed by, for example, housing an electrode body, which is a power generating element, and a non-aqueous electrolyte inside a battery case. In such an electrode body, for example, a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material are alternately stacked with a separator interposed therebetween. Patent documents 1 to 3 disclose a zigzag-shaped stacked electrode body in which a plurality of positive electrode plates and a plurality of negative electrode plates are sandwiched between a separator folded back in a zigzag shape. Patent document 4 also discloses a manufacturing device for such a zigzag-shaped stacked electrode body, which includes a separator supply mechanism, a zigzag folding mechanism, a positive electrode plate stacking mechanism, and a negative electrode plate stacking mechanism. It is disclosed that in the manufacturing device, the separator is fixed to a stacking table using a fixing claw (jig). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2004-503055 [Patent Document 2] JP 2016-143550 A [Patent Document 3] Patent Publication No. 2021-048141 [Patent Document 4] JP 2017-016946 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the results of intensive research by the present inventors, it was found that when a zigzag-shaped laminated electrode body is manufactured using the jig described in Patent Document 4, friction occurs when the jig is pulled out from between the positive and negative electrodes and the separator, causing the laminated position to shift. When the laminated position shifts in the zigzag-shaped laminated electrode body, there is a risk that a short circuit or the like may occur in a secondary battery including the laminated electrode body.

[0006] The present invention has been made in view of the above points, and aims to provide a method for manufacturing a secondary battery that suppresses the deviation of the stacking positions of the positive and negative electrodes and the separator in a stacked electrode body. Another object of the present invention is to provide a secondary battery that has improved battery performance by suppressing the deviation of the stacking positions. [Means for solving the problem]

[0007] The method for manufacturing a secondary battery disclosed herein is a method for manufacturing a secondary battery including a laminated electrode body in which a positive electrode and a negative electrode are laminated via a strip-shaped separator, and includes a lamination step of laminating the separator in a zigzag manner so that flat portions and folded portions are alternately provided in the longitudinal direction of the strip-shaped separator. The lamination step includes at least a first folding process for forming a first folded portion starting from a first pressing member that presses a portion of the flat portion close to the folded portion, a first cutting process for cutting at least a portion of the width direction of the separator perpendicular to the longitudinal direction in the formed first folded portion, and a second folding process for forming a second folded portion starting from a second pressing member that presses a portion of the flat portion close to a next folded portion other than the first folded portion formed by the first folding process. According to this configuration, since a part of the separator in the width direction is cut, friction when the pressing member is pulled out is reduced. This prevents the positive and negative electrodes and the separator from shifting from the desired stacking positions due to the movement of the pressing member. Therefore, it is possible to suitably manufacture a secondary battery in which the stacking position shift is suppressed in the stacked electrode body.

[0008] In a preferred embodiment of the manufacturing method disclosed herein, the first cutting process is carried out so as to cut at least 10% of the separator when the widthwise length of the separator at the first folded portion is taken as 100%. According to this configuration, the pressing member can be moved appropriately, and deviation of the stacking position in the stacked electrode body can be suppressed.

[0009] In a preferred embodiment of the manufacturing method disclosed herein, the first cutting process is carried out so as to cut 95% or less of the separator when the widthwise length of the separator at the first folded portion is taken as 100%. According to this configuration, it is possible to more suitably suppress deviation of the stacking position in the stacked electrode body.

[0010] In a preferred embodiment of the manufacturing method disclosed herein, the first cutting process is performed after a part of the planar portion, which is adjacent to the next folding portion other than the first folding portion, is pressed by the second pressing member. According to this configuration, the first cutting process can be carried out more stably, and therefore deviation of the stacking position in the stacked electrode body can be suitably suppressed.

[0011] In a preferred embodiment of the manufacturing method disclosed herein, in the first folding process, the first pressing member is composed of a plurality of jigs, and the first cutting process is performed so as to cut the separator in at least two places in the width direction at the first folding portion. According to this configuration, the moving distance of the pressing member can be reduced, so that deviation of the stacking position in the stacked electrode body can be more suitably suppressed.

[0012] In a preferred embodiment of the manufacturing method disclosed herein, in the first folding process, the first pressing member is composed of a single jig, and the first cutting process is performed so as to cut the entire width of the separator at the folding portion. According to this configuration, it is possible to suitably suppress deviation of the stacking position in the stacked electrode body.

[0013] Also, from another aspect, a secondary battery disclosed herein is provided. The secondary battery disclosed herein is a secondary battery including a laminated electrode body in which a positive electrode and a negative electrode are laminated via a strip-shaped separator, and the laminated electrode body has the separator laminated in a zigzag shape in the longitudinal direction of the laminated electrode body so that a flat portion and a folded portion are provided at both ends of the flat portion. In the stacking direction of the separators stacked in the zigzag shape, the positive electrode and the negative electrode are alternately arranged between the separators. Here, at the folded portion, at least a part of the separator is cut in the width direction perpendicular to the longitudinal direction. In a preferred embodiment of the secondary battery disclosed herein, the separator is cut in the folded portion by 10% to 95% when the length of the separator in the width direction is taken as 100%. According to this configuration, the shift in the stacking position in the stacked electrode body is suitably suppressed, thereby preventing short circuits. Also, the area in which the positive electrode and the negative electrode face each other can be increased, and a secondary battery with improved battery performance can be provided. [Brief description of the drawings]

[0014] [Figure 1] 1A and 1B are diagrams illustrating a structure of a zigzag laminated electrode body according to one embodiment. [Diagram 2]FIG. 2 is a diagram illustrating an example of a manufacturing apparatus used in a lamination step of a manufacturing method for a secondary battery according to an embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of a manufacturing apparatus used in a lamination step of a manufacturing method for a secondary battery according to an embodiment. [Figure 4] 5A to 5C are diagrams illustrating a first folding process and a first cutting process according to the first embodiment. [Diagram 5] FIG. 1 is a diagram illustrating a schematic configuration of a secondary battery according to an embodiment. [Figure 6] 10A to 10C are diagrams illustrating a first folding process and a first cutting process according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of a battery that do not characterize the technology disclosed herein) can be understood as design matters of a person skilled in the art based on the conventional technology in the field. The technology disclosed here can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Note that the numerical range expressed as "A to B" in this specification includes A and B.

[0016] In this specification, the term "battery" refers to any power storage device capable of extracting electrical energy, and is a concept that includes primary batteries and secondary batteries. In addition, in this specification, the term "secondary battery" refers to any power storage device capable of repeated charging and discharging, and is a concept that 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.

[0017] 1. Manufacturing method of secondary batteries The manufacturing method of the secondary battery disclosed herein includes a lamination step of laminating strip-shaped separators in a zigzag shape in which flat portions and folded portions are alternately provided in the longitudinal direction of the separator. The lamination step includes at least a first folding process of forming a first folded portion from a first pressing member that presses a portion of the flat portion close to the folded portion as a starting point, a first cutting process of cutting at least a portion of the formed first folded portion in a width direction perpendicular to the longitudinal direction of the separator, and a second folding process of forming a second folded portion from a second pressing member that presses a portion of the flat portion close to a next folded portion other than the first folded portion formed by the first folding process as a starting point. The manufacturing method of the secondary battery disclosed herein may be the same as a conventionally known manufacturing method except for including the first folding process, the first cutting process, and the second folding process as described above. In addition, it may further include other processes at any stage.

[0018] FIG. 1 is a diagram showing a structure of a laminated electrode body 20 laminated in a zigzag shape. FIG. 2 and FIG. 3 are diagrams showing an example of a manufacturing apparatus 100 that embodies the lamination step of the manufacturing method of a secondary battery disclosed herein. FIG. 4 is a diagram showing a first folding process and a first cutting process. In the drawings, the symbols L, R, F, Rr, U, and D represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the longitudinal direction, width direction perpendicular to the longitudinal direction, and up-down direction of the laminated electrode body 20, respectively. However, these are merely directions for convenience of explanation and do not limit the installation form of the laminated electrode body 20 in any way. The longitudinal direction X of the laminated electrode body 20 coincides with the longitudinal direction of the separator 70, and the width direction Y of the laminated electrode body 20 coincides with the width direction of the separator 70.

[0019] The manufacturing apparatus 100 shown in Fig. 2 and Fig. 3 can be used in the manufacturing method of the secondary battery disclosed herein. The manufacturing apparatus 100 includes, for example, a separator supplying section 110, a stacking section 120, a positive electrode supplying section 130, and a negative electrode supplying section 140. The separator supplying section 110 supplies the separator sheet 70 to the stacking section 120 along a predetermined conveying path. The separator supplying section 110 typically conveys the separator sheet 70 along its longitudinal direction using a plurality of supply rollers 112 and a plurality of guide rollers 114. The arrow in the figure indicates the conveying direction.

[0020] First Embodiment In the first embodiment, a configuration in which the pressing member used in the lamination step is composed of a plurality of jigs will be described.

[0021] (1)Lamination process In the lamination process, a laminated electrode body 20 is produced in which positive electrodes 50 and negative electrodes 60 are alternately laminated in the lamination direction (Z direction in FIG. 1) with a long separator 70 interposed therebetween. The separator 70 (hereinafter also referred to as "separator sheet 70") is folded in a zigzag shape by repeating mountain folds and valley folds at predetermined intervals in the longitudinal direction X of the separator 70. Such mountain folds and valley folds form the folding portion 72 (first folding portion 72a and second folding portion 72b) shown in FIG. 1. As shown in FIG. 1, the laminated electrode body 20 has a planar portion 71, and a first folding portion 72a (right end side in FIG. 1) and a second folding portion 72b (left end side in FIG. 1) at both ends of the planar portion 71 in the longitudinal direction X of the laminated electrode body 20. Such a laminated electrode body 20 can be produced by alternately laminating a positive electrode 50 (hereinafter also referred to as a "positive electrode sheet 50") and a negative electrode 60 (hereinafter also referred to as a "negative electrode sheet 60") so that the positive electrode 50 (hereinafter also referred to as a "positive electrode sheet 50") and the negative electrode 60 (hereinafter also referred to as a "negative electrode sheet 60") are sandwiched between the separators 70 in the lamination direction, the separators 70 being folded in a zigzag shape. Such a lamination process includes at least the first folding process, the first cutting process, and the second folding process, as described above. The lamination process may further include the second cutting process. Each process will be described below.

[0022] (2) First folding process In the first folding process, a first folded portion 72a (see FIG. 1) is formed. In the first folding process, the first folded portion 72a is formed starting from a first pressing member 121 that presses a part of the flat portion 71 and a position close to the folded portion 72. For example, as shown in FIG. 2, first, a long separator sheet 70 is supplied from a separator supply unit 110 onto a stacking table 125. In the separator supply unit 110, a supply roller 112 supplies the separator sheet 70 while moving (reciprocating back and forth) along the X direction of the separator sheet 70. The supplied separator sheet 70 is guided by a guide roller 114 and supplied to the stacking table 125. As a result, the separator sheet 70 is supplied to the stacking table 125 so as to repeat mountain folds and valley folds at a predetermined interval. The stacking table 125 is not particularly limited, and may be rectangular in plan view, and may have a horizontal surface on which the separator sheet 70 is supplied. Next, the positive electrode sheet 50 is supplied from the positive electrode supply unit 130 onto the supplied separator sheet 70. The method of supplying the positive electrode sheet 50 is not particularly limited, and for example, the positive electrode sheet 50 may be adsorbed to the adsorption plate 132 and placed at a predetermined position. When the positive electrode sheet 50 is supplied, the separator supply unit 110 moves toward one side (left direction L in this case) of the longitudinal direction X of the laminated electrode body 20. The first pressing member 121 is inserted between the positive electrode sheet 50 and the separator sheet 70, and presses a part of the flat portion 71 at a position close to the bent portion 72. For example, as shown in FIG. 4, the first pressing member 121 presses the positive electrode sheet 50 and the separator sheet 70 in contact with the lower surface side of the positive electrode sheet 50 at a position close to the bent portion 72 to temporarily fix them. Then, as shown in FIG. 4, the separator sheet 70 is folded obliquely upward from the first pressing member 121 while tension is being applied thereto, thereby forming the first folded portion 72a.

[0023] In the first embodiment, the first pressing member 121 is composed of a plurality of jigs. The first pressing member 121 is preferably composed of two jigs (hereinafter, also referred to as "first pressing member 121a" and "first pressing member 121b") as shown in FIG. 4. The material of the first pressing members 121a and 121b is not particularly limited, but may be, for example, stainless steel, fluorine-processed (fluorine resin-processed) metal, diamond-like carbon (DLC)-coated metal, etc. Among them, from the viewpoint of reducing friction, it is preferable to be composed of DLC-coated metal. Although not particularly limited, the shape of the first pressing members 121a and 121b may be a rectangular column as shown in the figure, a cylindrical column, or a semi-cylindrical column. Preferably, the part that contacts the separator sheet 70 is curved (has an R part). This makes it possible to more suitably form the first folded portion 72a without damaging the separator sheet 70. Furthermore, the size of the first pressing members 121a and 121b is not particularly limited, and may be set appropriately depending on the desired size of the laminated electrode body 20 and other factors.

[0024] The first pressing members 121a, 121b move so as to be inserted between the positive electrode sheet 50 and the separator sheet 70 to be supplied as described above. The first pressing members 121a, 121b may be configured to move along either the longitudinal direction X or the width direction Y of the separator 70. This can reduce the number of actuators for driving the first pressing members 121a, 121b, and simplify the configuration of the drive mechanism. For example, the first pressing members 121a, 121b may be configured to move along the width direction Y of the separator sheet 70. In this case, the first pressing member 121a may be configured to move toward the rear direction Rr of FIG. 4 to be inserted between the positive electrode sheet 50 and the separator sheet 70 to be supplied, and to move toward the front direction F to be pulled out from between the positive electrode sheet 50 and the separator sheet 70. On the other hand, the first pressing member 121b can be configured to move in the forward direction F to be inserted onto the positive electrode sheet 50, and to move in the rear direction Rr to be pulled out from between the positive electrode sheet 50 and the separator sheet 70. This can shorten the movement distance of the first pressing members 121a and 121b, and can prevent the position of the positive electrode sheet 50 or the separator sheet 70 from shifting due to the movement of the first pressing member 121a.

[0025] The first pressing members 121a, 121b may be configured to move, for example, along the longitudinal direction X of the separator sheet 70. In this case, it is preferable that the first pressing members 121a, 121b are both configured to move in the right direction R in FIG. 4 to be inserted between the positive electrode sheet 50 and the separator sheet 70, and to move further in the right direction R after performing a first cutting process described below, to be pulled out from between the positive electrode sheet 50 and the separator sheet 70. This makes it possible to shorten the distance of insertion and pull-out of the first pressing members 121 compared to movement in the left direction L in FIG. 4, and thus prevents the stacking position from shifting.

[0026] (3) First cutting process As described above, even if the material and moving direction of the first pressing member 121 are adjusted, friction is likely to occur when the first pressing member 121 moves between the positive electrode 50 and the negative electrode 60 and the separator 70, and the stacking position may be shifted in the stacked electrode body 20. For this reason, in the manufacturing method of the secondary battery disclosed herein, a first cutting process is performed. In the first cutting process, at least a part of the separator 70 in the width direction Y is cut at the first folded portion 72a formed above. For example, as shown in FIG. 4, in the separator 70, a cutting line C1 is set roughly along the apex of the first folded portion 72a. In the first cutting process, at least a part of the separator 70 in the width direction Y is cut along the cutting line C1 using a cutting device (not shown). This reduces friction when the first pressing member 121 is pulled out from between the positive electrode sheet 50 and the separator sheet 70, and it is possible to suppress the stacking position from being shifted. Moreover, with this configuration, it is possible to prevent the stacking position from shifting without complicating the drive mechanism for moving the first pressing members 121a, 121b. Furthermore, in the stacked electrode body 20, the positive electrode 50 and the negative electrode 60 face each other more precisely, so that the battery performance of the secondary battery can be improved and short-circuiting of the secondary battery can be prevented. The cutting device is not particularly limited, and cutting can be performed by a conventionally known cutting device such as a rotary cutter or a laser cutter.

[0027] In a preferred aspect of the first embodiment, the first pressing member 121 is made up of a plurality of jigs, and cuts the separator 70 in at least two places in the width direction Y at the first folding portion 72a. For example, as shown in FIG. 4, the first pressing member 121 is made up of two jigs, and cuts the separator 70 in two places in the width direction Y along the cutting lines C1 and C2 at the first folding portion 72a. This allows the first pressing members 121a and 121b to be suitably pulled out from between the positive electrode sheet 50 and the separator sheet 70. Therefore, deviation of the stacking position in the stacked electrode body 20 is more suitably suppressed.

[0028] In a preferred embodiment, the first cutting process is performed so as to cut 10% or more of the separator 70 when the length of the separator 70 in the width direction Y at the first bent portion 72a is taken as 100%. This allows the first pressing member 121 to be suitably pulled out from between the positive electrode sheet 50 and the separator sheet 70 as described above, and therefore the shift in the stacking position in the stacked electrode body 20 can be more suitably suppressed. The first cutting process is more preferably performed so as to cut, for example, 12.4% or more of the separator when the length of the separator 70 in the width direction Y at the first bent portion 72a is taken as 100%, and may be performed so as to cut 20% or more of the separator, or may be performed so as to cut 30% or more of the separator.

[0029] The upper limit of the length to which the separator 70 is cut in the first cutting process is not particularly limited. For example, when the length of the separator 70 in the width direction Y at the first folding portion 72a is 100%, the cutting may be performed so as to cut 100% (i.e., the entire separator 70 in the width direction Y). In this case, after the first cutting process is performed, the first pressing member 121 moves in the R direction along the longitudinal direction X and is pulled out from between the positive electrode sheet 50 and the separator sheet 70. As described above, since the separator sheet 70 is in a state in which tension is applied by the separator supply unit 110, even if the first pressing member 121 is pulled out in the R direction, the stacking displacement is suppressed, and the stacked electrode body 20 can be suitably manufactured.

[0030] In another preferred embodiment, the first cutting process may be performed, for example, to cut 95% or less of the separator, 80% or less of the separator, or 70% or less of the separator, when the length of the separator 70 in the width direction Y at the first folded portion 72a is taken as 100%. With this configuration, it is possible to more suitably suppress deviation of the stacking positions of the positive electrode sheet 50 and the separator sheet 70. In this case, the first pressing members 121a and 121b may be configured to move along the width direction Y or along the longitudinal direction X.

[0031] In a preferred embodiment, the first cutting process is performed after a part of the flat portion 71, which is adjacent to the next folding portion other than the first folding portion 72a, is pressed by the second pressing member 122 (see FIG. 3). This allows the first cutting process to be performed in a state in which the longitudinal direction X of the separator sheet 70 is suitably fixed, and the shifting of the stacking position can be further suitably suppressed. Specifically, after the first folding process is performed, the separator supply unit 110 moves in the L direction of FIG. 3 to supply the separator sheet 70 onto the positive electrode sheet 50. Next, the negative electrode sheet 60 is supplied onto the separator sheet 70 from the negative electrode supply unit 140 here. Then, the negative electrode sheet 60 and the separator sheet 70 are pressed by the second pressing member 122 at a position adjacent to the next folding portion 72 other than the first folding portion 72a, and then the first cutting process is performed. Alternatively, after the first folding process is performed, the separator supply unit 110 moves in the L direction in Fig. 3 to supply the separator sheet 70 onto the positive electrode sheet 50. Then, after the separator 70 is pressed by the second pressing member 122, the first cutting process may be performed.

[0032] (4) Second folding process The second folding process forms the second folding portion 72b (see FIG. 1). In the second folding process, the second folding portion 72b is formed starting from the second pressing member 122 that presses a part of the flat portion 71 described above and a position adjacent to the next folding portion 72 other than the first folding portion 72a formed in the first folding process. The second folding process can be performed by performing a process similar to the first folding process. As an example, as shown in FIG. 3, first, the separator sheet 70 is supplied onto the positive electrode sheet 50 by the separator supply unit 110, and the negative electrode sheet 60 is supplied onto the separator 70 from the negative electrode supply unit 140. The method of supplying the negative electrode sheet 60 is not particularly limited, and may be the same as the method of supplying the positive electrode sheet 50. For example, the negative electrode sheet 60 may be adsorbed to the adsorption plate 142 and placed at a predetermined position. When the negative electrode sheet 60 is supplied, the separator supply unit 110 moves toward the R direction in FIG. 3. The second pressing member 122 presses a part of the flat portion 71 at a position adjacent to the next folding portion 72, not the first folding portion 72a. The second pressing member 122 presses, for example, the negative electrode sheet 60 and the separator sheet 70 in contact with the lower surface side of the negative electrode sheet 60 at a position adjacent to the folding portion 72, and temporarily fixes them. Then, the separator sheet 70 is folded obliquely upward from the second pressing member 122 while tension is applied, thereby forming the second folding portion 72b.

[0033] The configuration of the second pressing member 122 may be the same as that of the first pressing member 121, and therefore detailed description thereof will be omitted. The second pressing member 122 is preferably composed of, for example, two jigs. Similarly to the above-described first pressing member 121, the second pressing member 122 may be configured to move along one of the longitudinal direction X and the width direction Y of the separator 70. This allows the configuration of the drive mechanism of the second pressing member 122 to be simplified. The second pressing member 122 may be configured to move along the width direction Y of the separator sheet 70, or may be configured to move along the longitudinal direction X of the separator sheet 70. Preferably, the second pressing member 122 is configured to move along the width direction Y of the separator sheet 70 and to be inserted between the negative electrode sheet 60 and the separator sheet 70 to be supplied.

[0034] (5) Second cutting process In a preferred embodiment, the method for manufacturing a secondary battery disclosed herein further includes a second folding and cutting process. In the second cutting process, at least a part of the separator 70 in the width direction Y is cut at the second folded portion 72b formed in the second folding process. The second cutting process can be performed by performing a process similar to the first cutting process. For example, a cutting line is set in the separator 70 approximately along the apex of the second folded portion 72b. In the second cutting process, the second folded portion 72b is cut along the cutting line using a cutting device not shown. This makes it possible to prevent the stacking positions of the positive electrode sheet 50 and the separator sheet 70 from being shifted due to friction when the second pressing member 122 is pulled out from between the positive electrode sheet 50 and the separator sheet 70, and prevents a short circuit in the stacked electrode body 20. In addition, it is possible to prevent the stacking positions from being shifted without complicating the drive mechanism for moving the second pressing member 122. The cutting device is not particularly limited, and for example, a cutting device similar to the cutting device that can be used in the first cutting process can be used. The length along which the separator 70 is cut in the second cutting process may be approximately equal to or different from the length along which the separator 70 is cut in the first cutting process. Preferably, the length along which the separator 70 is cut in the first cutting process and the length along which the separator 70 is cut in the second cutting process are approximately equal to each other.

[0035] In a preferred embodiment in which the second pressing member 122 is composed of a plurality of (preferably two) jigs as described above, the separator 70 may be cut at least in two places in the width direction Y at the second bent portion 72b. This more suitably suppresses deviation of the stacking position in the stacked electrode body 20 at the second bent portion 72b as well.

[0036] The second cutting process is preferably performed so as to cut 10% or more of the separator 70 when the length of the separator 70 in the width direction Y at the second bent portion 72b is taken as 100%, and more preferably performed so as to cut 12.4% or more of the separator, and may be performed so as to cut 20% or more of the separator, or may be performed so as to cut 30% or more of the separator. The second cutting process may be performed so as to cut 100% (i.e., the entire separator 70 in the width direction Y) when the length of the separator 70 in the width direction Y at the second bent portion 72b is taken as 100%. In this case, the second pressing member 122 is configured to move along the longitudinal direction X after the second cutting process and be pulled out from between the negative electrode sheet 60 and the separator sheet 70.

[0037] Furthermore, when the length of the second bent portion 72b in the width direction Y is taken as 100%, the second cutting process may be performed, for example, to cut the separator by 95% or less, or may be performed to cut the separator by 80% or less, or may be performed to cut the separator by 70% or less. In this case, the second pressing member 122 may be configured to move along the width direction Y or may be configured to move along the longitudinal direction X. With this configuration, it is possible to more suitably suppress deviation of the stacking position in the stacked electrode body 20.

[0038] For example, by repeatedly carrying out the above-mentioned (2) first folding process to (5) second cutting process, it is possible to produce a zigzag-shaped stacked electrode body 20 in which a plurality of first folding portions 72a and second folding portions 72b are provided on both ends of a flat portion 71 in the longitudinal direction X of the separator sheet 70. Note that the cutting process may be carried out on either the first folding portion 72a or the second folding portion 72b.

[0039] The laminated electrode body 20 thus produced is housed inside a battery case and sealed to produce a secondary battery. The process of housing the laminated electrode body 20 and the process of sealing the battery case may be carried out by conventionally known means, and are not characteristic of the method of producing a secondary battery disclosed herein, so detailed explanations will be omitted.

[0040] As described above, a secondary battery can be manufactured using the manufacturing method disclosed herein. By performing the folding and cutting processes in the lamination step as described above, the positions of the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70 are prevented from shifting from the desired lamination positions due to friction when the pressing member moves. Therefore, in the laminated electrode body 20 manufactured by this manufacturing method, the lamination position shift is suppressed. Then, a secondary battery including the laminated electrode body 20 can preferably prevent short circuits and improve battery performance. Moreover, according to this configuration, it is possible to preferably suppress the lamination position shift without complicating the configuration of the device.

[0041] Hereinafter, one embodiment of a secondary battery obtained by the manufacturing method disclosed herein will be described with reference to the drawings.

[0042] FIG. 5 is a diagram showing a schematic structure of a secondary battery 1 disclosed herein. The secondary battery 1 is a lithium ion secondary battery. As shown in FIG. 5, the secondary battery 1 disclosed herein is a sealed battery constructed by accommodating a laminated electrode body 20 and a non-aqueous electrolyte (not shown) in a battery case 30. The shape, material, size, etc. of the battery case 30 are not particularly limited as long as the laminated electrode body 20 and the electrolyte can be accommodated therein. The battery case 30 may be, for example, a flat rectangular battery case having an opening as shown in FIG. 5. In this case, the material of the battery case 30 is a lightweight metal material with good thermal conductivity such as aluminum. Alternatively, the battery case 30 may be made of a laminate film having a multi-layer structure.

[0043] 5, the battery case 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection, and a thin-walled safety valve 36 that is set to release the internal pressure when the internal pressure of the battery case 30 rises to a predetermined level or higher. The battery case 30 is also provided with an injection port (not shown) for injecting an electrolyte. The positive terminal 42 is electrically connected to the positive current collector plate 42a. The negative terminal 44 is electrically connected to the negative current collector plate 44a.

[0044] The laminated electrode body 20 is a power generating element housed inside the battery case 30. The laminated electrode body 20 is housed in the battery case 30 in a state where it is covered with a resin insulating film 29. This makes it possible to prevent electrical conduction between the battery case 30 and the laminated electrode body 20. As described above, the laminated electrode body 20 has a flat portion 71 and a first folded portion 72a and a second folded portion 72b at both ends of the flat portion 71 in the longitudinal direction of the laminated electrode body 20. The first folded portion 72a and the second folded portion 72b are formed by folding the long separator 70 into a zigzag shape by repeatedly folding the separator 70 into mountain folds and valley folds at predetermined intervals. Then, the separator 70 is folded into a zigzag shape, and the positive electrode 50 and the negative electrode 60 are sandwiched between the separators 70 in the stacking direction (see FIG. 1). 1, the positive electrode sheet 50 is disposed so that both sides in the Z direction are in contact with the separator sheet 70. Similarly, the negative electrode sheet 60 is disposed so that both sides in the Z direction are in contact with the separator 70. This allows the positive electrode sheet 50 and the negative electrode sheet 60 to be stacked in a state in which they are insulated by the separator sheet 70.

[0045] In the secondary battery 1 disclosed herein, a portion of the separator 70 in the width direction (Y direction in FIG. 5) is cut at the bent portion 72 of the laminated electrode body 20. In the laminated electrode body 20, a portion of the separator 70 in the width direction may be cut at at least one of the first bent portion 72a and the second bent portion 72b. Preferably, in the laminated electrode body 20, a portion of the separator 70 in the width direction is cut at both the first bent portion 72a and the second bent portion 72b. In the laminated electrode body 20, the length of the separator 70 cut at the first bent portion 72a and the length of the separator 70 cut at the second bent portion 72b may be approximately equal to or different from each other. Preferably, the length of the separator 70 cut at the first bent portion 72a and the length of the separator 70 cut at the second bent portion 72b may be approximately equal to each other.

[0046] In a preferred embodiment, when the width direction length of the separator 70 at the folded portion 72 (either the first folded portion 72a or the second folded portion 72b) is taken as 100%, the separator 70 is cut by 10% or more. When the width direction length of the separator 70 at the folded portion 72 is taken as 100%, the separator 70 may be cut by, for example, 12.4% or more, 20% or more, or 30% or more. In addition, the upper limit of the cut length of the separator 70 is not particularly limited, but may be, for example, 95% or less, 80% or less, or 70% or less when the width direction length of the separator 70 at the folded portion 72 is taken as 100%.

[0047] The positive electrode 50 has a configuration in which a positive electrode active material layer containing a positive electrode active material is formed on one or both sides (both sides in this case) of a sheet-shaped positive electrode collector. In the positive electrode 50, a positive electrode collector exposed portion 52a that does not have a positive electrode active material layer is formed in a band shape near one edge in the width direction Y (the edge on the upper U side in this case). The negative electrode 60 has a configuration in which a negative electrode active material layer containing a negative electrode active material is formed on one or both sides (both sides in this case) of a sheet-shaped negative electrode collector. In the negative electrode 60, a negative electrode collector exposed portion 62a that does not have a negative electrode active material layer is formed in a band shape near one edge in the width direction Y (the edge on the upper U side in this case). As shown in FIG. 5, a part of the positive electrode collector exposed portion 52a and the negative electrode collector exposed portion 62a protrudes in the upward direction U from one edge in the width direction Y (the edge on the upper U side in this case) of the laminated electrode body 20. The positive current collector exposed portion 52a and the negative current collector exposed portion 62a are joined to the positive current collector plate 42a and the negative current collector plate 44a, respectively. The positive current collector exposed portion 52a and the positive current collector plate 42a are electrically connected to each other, thereby electrically connecting the stacked electrode body 20 and the positive electrode terminal 42. Similarly, the negative current collector exposed portion 62a and the negative current collector plate 44a are electrically connected to each other, thereby electrically connecting the stacked electrode body 20 and the negative electrode terminal 44.

[0048] The positive electrode current collector constituting the positive electrode 50 may be, for example, a sheet or foil made of a metal having good electrical conductivity, such as aluminum, an aluminum alloy, nickel, or stainless steel. Among them, aluminum foil is preferable as the positive electrode current collector. The positive electrode active material layer contains at least a positive electrode active material (for example, a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) capable of reversibly absorbing and releasing charge carriers. The positive electrode active material layer may contain any component other than the positive electrode active material, such as a conductive material, a binder, various additive components, and the like. As the conductive material, for example, a carbon material such as acetylene black (AB) may be used. As the binder, for example, polyvinylidene fluoride (PVdF) may be used.

[0049] The negative electrode current collector constituting the negative electrode 60 may be, for example, a sheet or foil made of a metal having good electrical conductivity, such as copper, nickel, titanium, or stainless steel. Among these, copper foil is preferable as the negative electrode current collector. The negative electrode active material layer contains at least a negative electrode active material (e.g., a carbon material such as graphite) capable of reversibly absorbing and releasing charge carriers. The negative electrode active material layer may contain any component other than the negative electrode active material, such as a binder, a dispersant, or various additive components. As the binder, for example, rubbers such as styrene butadiene rubber (SBR) may be used. As the dispersant, for example, celluloses such as carboxymethyl cellulose (CMC) may be used.

[0050] The separator 70 is made of, for example, a porous resin base material. Examples of the resin base material include sheets (films) made of resins such as polyolefins, such as polyethylene (PE) and polypropylene (PP), polyesters, polyamides, and cellulose. The separator 70 may have a single-layer structure, or may have a structure in which two or more types of porous resin sheets having different properties and characteristics (such as thickness and porosity) are laminated (for example, a three-layer structure in which a PP layer is laminated on both sides of a PE layer). The separator 70 may also have a heat-resistant layer (HRL) made of ceramic particles or the like on its surface. The HRL may be the same as a heat-resistant layer provided in a separator of a known non-aqueous electrolyte secondary battery, and may include, for example, ceramic particles, such as alumina, silica, boehmite, magnesia, and titania, and a binder, such as PVdF.

[0051] As described above, the secondary battery 1 includes an electrolyte. The electrolyte typically contains a non-aqueous solvent and an electrolyte salt (in other words, a supporting salt). As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones that are used in electrolytes of general secondary batteries can be used without any particular limitation. Among them, carbonates are preferable, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyl difluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC). Such non-aqueous solvents can be used alone or in appropriate combination of two or more. As the electrolyte salt, for example, lithium salts such as LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide (LiFSI) can be used, and among them, LiPF6 is preferable. The concentration of the electrolyte salt is not particularly limited, but is preferably 0.7 mol / L or more and 1.3 mol / L or less. The electrolyte may contain various additives other than the above-mentioned components, such as a film-forming agent such as an oxalato complex, a gas generating agent such as biphenyl (BP) or cyclohexylbenzene (CHB), a thickener, etc., as long as the effects of the present invention are not significantly impaired.

[0052] The secondary battery 1 obtained in the above manner has the advantage that short circuits are prevented and battery performance is improved. Such a secondary battery 1 can be used for various purposes. Suitable applications include a driving power source mounted on vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). The secondary battery 1 can also be used in the form of a battery pack in which a plurality of batteries 1 are connected in series and / or parallel.

[0053] <Second embodiment> In the second embodiment, a mode in which the pressing member used in the lamination step is composed of one jig will be described.

[0054] FIG. 6 is a diagram corresponding to FIG. 4 according to the second embodiment, and is a diagram showing the first bending process and the first cutting process according to the second embodiment. In the second embodiment, the first pressing member 221 is composed of one jig. The size of the first pressing member 221 is preferably slightly larger than the laminated electrode body to be produced. This allows a wider range to be supported when forming the folded portion in the separator sheet 70, so that the folded portion can be formed with high accuracy. The material, shape, etc. of the first pressing member 221 may be the same as those described in the first embodiment, so detailed description will be omitted.

[0055] In the first folding process, the first pressing member 221 moves so as to be inserted between the positive electrode sheet 50 and the separator sheet 70 being supplied. In the first folding process, as shown in FIG. 6, a first folded portion is formed. In the first folding process, the first folded portion is formed starting from the first pressing member 221, which is a part of the flat portion and presses a position close to the folded portion. Here, when the first pressing member 221 in the second embodiment moves along the width direction Y of the separator sheet 70, friction with the separator 70 occurs only in one direction due to being composed of one jig, so that the positive electrode sheet 50 or the negative electrode sheet is likely to be displaced from the stacking position. Therefore, when the first pressing member 221 is composed of one jig, it is configured to move along the longitudinal direction X of the separator sheet 70. 6 to be inserted between the positive electrode sheet 50 and the separator sheet 70, and after the first cutting process, the first pressing member 221 moves further in the right direction R to be pulled out from between the positive electrode sheet 50 and the separator sheet 70. This prevents deviation of the stacking position in the stacked electrode body 20 even when the first pressing member 221 is formed from a single jig. Also, by configuring the first pressing member 221 to move in one direction in the longitudinal direction X, for example, it is possible to simplify the configuration of the device (drive mechanism) and improve the efficiency of the manufacturing method.

[0056] Next, in the first cutting process, the separator 70 is cut over the entire length in the width direction Y at the first folded portion formed above. As shown in FIG. 6, in the separator 70, a cutting line C3 is set along approximately the apex of the first folded portion. In the first cutting process, the separator 70 is cut over the entire length in the width direction Y along the cutting line C3 using a cutting device (not shown). This allows the first pressing member 221 to move along the longitudinal direction X. As described above, the separator sheet 70 is in a state where tension is applied by the separator supply unit 110, so that even if the first pressing member 221 is pulled out in the R direction, stacking misalignment is suppressed, and the stacked electrode body 20 can be suitably manufactured.

[0057] In a preferred embodiment, the first cutting process is performed after a part of the planar portion, which is adjacent to the next folding portion and not the first folding portion, is pressed by the second pressing member. As described above, in the second embodiment, the first pressing member 221 moves along the longitudinal direction X, so that friction is likely to occur toward the right direction R in FIG. 6. For this reason, by performing the first cutting process in a state in which the other side of the longitudinal direction X (the left direction L side in FIG. 6) is pressed by the second pressing member, the shift of the stacking position in the stacked electrode body is more suitably suppressed. Specifically, after the first folding process is performed, the separator sheet 70 is supplied on the positive electrode sheet 50, and the negative electrode sheet is supplied on the separator sheet 70. Then, it is preferable to perform the first cutting process after the negative electrode sheet and the separator sheet 70 are pressed by the second pressing member at a position adjacent to the next folding portion and not the first folding portion. Alternatively, after the first folding process has been performed, the separator sheet 70 may be provided on the positive electrode sheet 50, and the separator 70 may be pressed by the second pressing member, after which the first cutting process may be performed. In the above second embodiment, the first pressing member 221 has been described as an example, but the same may be true for the second pressing member. For example, when the second pressing member is composed of one jig, it is configured to move along the longitudinal direction X.

[0058] Although the preferred embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the field. The technology described in the claims includes various modifications and changes of the above-exemplified embodiment. For example, it is possible to replace a part of the above-mentioned embodiment with another modification, and it is also possible to add another modification to the above-mentioned embodiment. Furthermore, if a technical feature is not described as essential, it can be appropriately deleted.

[0059] For example, the first pressing member may be composed of a plurality of jigs and the second pressing member may be composed of a single jig, or the first pressing member may be composed of a single jig and the second pressing member may be composed of a plurality of jigs.

[0060] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing a secondary battery including a laminated electrode body in which a positive electrode and a negative electrode are laminated with a strip-shaped separator therebetween, the method including a lamination step of laminating the separator in a zigzag manner so that flat portions and folded portions are alternately provided in the longitudinal direction of the strip-shaped separator, the lamination step including at least a first folding process of forming a first folded portion starting from a first pressing member that presses a portion of the flat portion in a position adjacent to the folded portion, a first cutting process of cutting at least a portion of the width direction of the separator perpendicular to the longitudinal direction in the first folded portion formed, and a second folding process of forming a second folded portion starting from a second pressing member that presses a portion of the flat portion in a position adjacent to a next folded portion other than the first folded portion formed by the first folding process. Item 2: The method for manufacturing a secondary battery described in item 1, wherein the first cutting process is carried out so as to cut 10% or more of the separator when the widthwise length of the separator at the first folding portion is taken as 100%. Item 3: The method for manufacturing a secondary battery according to item 1 or 2, wherein the first cutting process is carried out so as to cut 95% or less of the separator when the widthwise length of the separator at the first bent portion is taken as 100%. Item 4: The method for manufacturing a secondary battery described in any one of Items 1 to 3, wherein the first cutting process is performed after a part of the planar portion, which is adjacent to a next folding portion other than the first folding portion, is pressed by the second pressing member. Item 5: The method for manufacturing a secondary battery according to any one of items 1 to 4, wherein in the first folding process, the first pressing member is composed of a plurality of jigs, and the first cutting process is carried out so as to cut the separator at least at two locations in the width direction at the first folding portion. Item 6: The method for manufacturing a secondary battery described in item 4, wherein in the first folding process, the first pressing member is composed of a single jig, and the first cutting process is performed so as to cut the entire width of the separator at the folding portion. Item 7: A secondary battery including a laminated electrode body in which positive and negative electrodes are laminated with a strip-shaped separator therebetween, the laminated electrode body being configured such that the separator is laminated in a zigzag shape in the longitudinal direction of the laminated electrode body so as to have a flat portion and folded portions at both ends of the flat portion, the positive electrodes and the negative electrodes are alternately arranged between the separators in the stacking direction of the zigzag-stacked separators, and the separator is cut at least partially in the width direction perpendicular to the longitudinal direction at the folded portions. Item 8: The secondary battery according to item 7, wherein, at the bent portion, 10% to 95% of the separator is cut when the length of the separator in the width direction is taken as 100%. [Explanation of symbols]

[0061] 1 Secondary battery 20. Laminated electrode body 29 Insulating film 30 Battery case 36 Safety valve 42 Positive terminal 42a Positive current collector 44 Negative terminal 44a Negative current collector plate 50 Positive electrode (positive electrode sheet) 52a Exposed part of positive electrode current collector 60 Negative electrode (negative electrode sheet) 62a Exposed part of negative electrode current collector 70 Separator (separator sheet) 71 Plane part 72 Bending section 72a First bending part 72b Second bending part 100 Manufacturing equipment 110 Separator supply section 120 Laminated section 121 First holding member 122 Second holding member 130 Positive electrode supply unit 140 Negative electrode supply unit 221 First holding member

Claims

1. A method for manufacturing a secondary battery having a laminated electrode assembly in which a positive electrode and a negative electrode are laminated with a strip-shaped separator interposed therebetween, comprising the steps of: The method includes a lamination step of laminating the separator in a zigzag manner so that flat portions and folded portions are alternately provided in the longitudinal direction of the strip-shaped separator, The lamination step includes: a first folding process in which a part of the planar portion, the part being close to the bent portion, is pressed with a first pressing member along a width direction perpendicular to the longitudinal direction, and the sheet is folded from the first pressing member as a starting point to form a first bent portion along the width direction; a first cutting process for cutting at least a portion of the first folded portion in the width direction of the separator, the portion being adjacent to the first pressing member along the width direction; a second bending process for forming a second bent portion from a second pressing member that presses a portion of the planar portion close to a next bent portion other than the first bent portion formed by the first bending process; At least the first cutting process is performed so as to cut the separator by 95% or less when the length of the separator in the width direction at the first bent portion is taken as 100%. A method for manufacturing a secondary battery.

2. A method for manufacturing a secondary battery having a laminated electrode assembly in which a positive electrode and a negative electrode are laminated with a strip-shaped separator interposed therebetween, comprising the steps of: The method includes a lamination step of laminating the separator in a zigzag manner so that flat portions and folded portions are alternately provided in the longitudinal direction of the strip-shaped separator, The lamination step includes: a first folding process in which a part of the planar portion, the part being close to the bent portion, is pressed with a first pressing member along a width direction perpendicular to the longitudinal direction, and the sheet is folded from the first pressing member as a starting point to form a first bent portion along the width direction; a first cutting process for cutting at least a portion of the first folded portion in the width direction of the separator, the portion being adjacent to the first pressing member along the width direction; a second bending process for forming a second bent portion from a second pressing member that presses a portion of the planar portion close to a next bent portion other than the first bent portion formed by the first bending process; At least In the first bending process, the first pressing member is composed of a plurality of jigs, The first cutting process is performed so as to cut the separator at least at two positions in the width direction at the first folding portion. A method for manufacturing a secondary battery.

3. the first cutting process is performed so as to cut 10% or more of the separator when the length of the separator in the width direction at the first bent portion is taken as 100%. The method for producing the secondary battery according to claim 1 or 2.

4. the first cutting process is performed after a portion of the planar portion, which is adjacent to a next bent portion other than the first bent portion, is pressed by the second pressing member. The method for producing the secondary battery according to claim 1 or 2.

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