JP7630462B2 - Secondary battery manufacturing method and secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery and a secondary battery.

In recent years, secondary batteries (e.g., lithium-ion secondary batteries) have been used favorably as portable power sources for personal computers, mobile terminals, etc., and as driving power sources installed in vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs).

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, positive electrodes containing a positive electrode active material and negative electrodes 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 multiple positive electrode plates and multiple negative electrode plates are sandwiched between a separator folded back in a zigzag shape. Patent document 4 discloses a manufacturing device for such zigzag-shaped stacked electrode bodies, which includes a separator supply mechanism, a zigzag mechanism, a positive electrode plate stacking mechanism, and a negative electrode plate stacking mechanism. It is disclosed that the manufacturing device uses a fixing claw (jig) to fix the separator to the stacking table.

Special Publication No. 2004-503055 JP 2016-143550 A JP 2021-048141 A JP 2017-016946 A

However, according to the results of intensive research by the present inventors, when a zigzag-shaped laminated electrode body is manufactured using a jig as 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 stacking position to shift. If the stacking 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 equipped with the laminated electrode body.

The present invention has been made in consideration of these points, and aims to provide a method for manufacturing a secondary battery that prevents the stacking positions of the positive and negative electrodes and the separator from shifting in a stacked electrode body. Another objective is to provide a secondary battery with improved battery performance by preventing the stacking positions from shifting.

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 formed first folded portion in a width direction perpendicular to the longitudinal direction of the separator, 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.

In a preferred aspect 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.

In a preferred aspect 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.

In a preferred aspect 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.

In a preferred aspect 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 at least at two locations 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.

In one preferred aspect 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 widthwise length 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.

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 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.

1A and 1B are diagrams illustrating a structure of a zigzag laminated electrode body according to one embodiment. 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. 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. 5A to 5C are diagrams illustrating a first bending process and a first cutting process according to the first embodiment. FIG. 1 is a diagram illustrating a schematic configuration of a secondary battery according to an embodiment. 10A to 10C are diagrams illustrating a first bending process and a first cutting process according to a second embodiment.

Below, embodiments of the technology disclosed herein are described with reference to the drawings. Note that matters other than those specifically mentioned in this specification that are 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 for a person skilled in the art based on the prior art in the field. The technology disclosed here can be implemented based on the contents disclosed in this specification and common technical knowledge in the field. Note that the numerical range expressed as "A to B" in this specification includes A and B.

In this specification, the term "battery" refers to any power storage device capable of extracting electrical energy, and is a concept that encompasses primary 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 encompasses 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.

1. Manufacturing method of secondary battery The manufacturing method of secondary battery disclosed herein includes a lamination process 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 process includes 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 and close to the folded portion, 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 starting from a second pressing member that presses a portion of the flat portion and close to a next folded portion other than the first folded portion formed by the first folding process. The manufacturing method of 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.

1 is a diagram showing a structure of a stacked electrode body 20 stacked in a zigzag shape. FIG. 2 and FIG. 3 are diagrams showing an example of a manufacturing apparatus 100 that embodies the stacking process 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 represent the longitudinal direction, width direction perpendicular to the longitudinal direction, and up-down direction of the stacked electrode body 20, respectively. However, these are merely directions for convenience of explanation and do not limit the installation form of the stacked electrode body 20 in any way. The longitudinal direction X of the stacked electrode body 20 coincides with the longitudinal direction of the separator 70, and the width direction Y of the stacked electrode body 20 coincides with the width direction of the separator 70.

The manufacturing apparatus 100 shown in Figures 2 and 3 can be used in the manufacturing method of the secondary battery disclosed herein. The manufacturing apparatus 100 includes, for example, a separator supply unit 110, a stacking unit 120, a positive electrode supply unit 130, and a negative electrode supply unit 140. The separator supply unit 110 supplies the separator sheet 70 to the stacking unit 120 along a predetermined transport path. The separator supply unit 110 typically transports the separator sheet 70 along its longitudinal direction using multiple supply rollers 112 and multiple guide rollers 114. The arrows in the figures indicate the transport direction.

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

(1) Stacking process In the stacking process, a stacked electrode body 20 is produced in which the positive electrodes 50 and the negative electrodes 60 are alternately stacked in the stacking direction (Z direction in FIG. 1) via a long separator 70. 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 stacked 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 stacked 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 they are sandwiched between separators 70 folded in a zigzag manner in the lamination direction of the separator sheets 70. As described above, such a lamination process includes at least a first folding process, a first cutting process, and a second folding process. The lamination process may further include a second cutting process. Each process will be described below.

(2) First folding process In the first folding process, the first folding portion 72a (see FIG. 1) is formed. In the first folding process, the first folding portion 72a is formed starting from the first pressing member 121 that presses a part of the flat portion 71 and a position close to the folding portion 72. For example, as shown in FIG. 2, first, a long separator sheet 70 is supplied from the separator supply unit 110 onto the stacking table 125. In the separator supply unit 110, the supply roller 112 supplies the separator sheet 70 while moving along the X direction of the separator sheet 70 (while reciprocating back and forth). The supplied separator sheet 70 is guided by the 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 (here, the left direction L) 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 folded 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 folded portion 72, and temporarily fixes them. 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.

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 in contact with 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, etc.

As described above, the first pressing members 121a and 121b move so as to be inserted between the positive electrode sheet 50 and the separator sheet 70 to be supplied. The first pressing members 121a and 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 and 121b, and simplify the configuration of the drive mechanism. For example, the first pressing members 121a and 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 rearward 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 121.

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 toward the right direction R in FIG. 4 to be inserted between the positive electrode sheet 50 and the separator sheet 70, and to be pulled out from between the positive electrode sheet 50 and the separator sheet 70 by moving further toward the right direction R after performing the first cutting process described below. This makes it possible to shorten the distance of insertion and removal of the first pressing members 121 compared to moving in the left direction L in FIG. 4, and suppresses deviation of the stacking position.

(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, the 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.

In a preferred aspect of the first embodiment, the first pressing member 121 is composed of multiple jigs, and at the first bent portion 72a, the separator 70 is cut in the width direction Y at least in two places. For example, as shown in FIG. 4, the first pressing member 121 is composed of two jigs, and at the first bent portion 72a, the separator 70 is cut in the width direction Y at two places along the cutting lines C1 and C2. 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, the shift in the stacking position in the stacked electrode body 20 is more suitably suppressed.

In a preferred embodiment, the first cutting process is performed so that the separator 70 is cut by 10% or more 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, so that 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 that the separator 70 is cut by, for example, 12.4% or more 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 that the separator is cut by 20% or more, or may be performed so that the separator is cut by 30% or more.

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 process may be performed so that 100% (i.e., the entire width direction Y of the separator 70) is cut. In this case, after the first cutting process is performed, the first pressing member 121 is moved 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 produced.

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

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 with the longitudinal direction X of the separator sheet 70 appropriately fixed, and the stacking position can be further preferably prevented from shifting. 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 can be performed.

(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 in the direction R 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, which is 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 under tension, whereby the second folding portion 72b can be formed.

The configuration of the second pressing member 122 may be the same as that of the first pressing member 121, so detailed description will be omitted. The second pressing member 122 is preferably composed of, for example, two jigs. In addition, 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, similar to the above-mentioned first pressing member 121. 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, it is configured to move along the width direction Y of the separator sheet 70 and be inserted between the negative electrode sheet 60 and the separator sheet 70 to be supplied.

(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, in the separator 70, a cutting line is set along approximately 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 suppress the stacking position of the positive electrode sheet 50 and the separator sheet 70 from shifting 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 suppress the stacking position from shifting 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.

In a preferred embodiment in which the second pressing member 122 is composed of multiple (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 effectively prevents the stacking position of the stacked electrode body 20 from shifting at the second bent portion 72b.

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

The second 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 second folded portion 72b in the width direction Y is taken as 100%. In this case, the second pressing member 122 may be configured to move along the width direction Y or along the longitudinal direction X. With this configuration, it is possible to more effectively suppress the shifting of the stacking position in the stacked electrode body 20.

For example, by repeatedly carrying out the above-mentioned (2) first folding process to (5) second cutting process, a zigzag-shaped laminated electrode body 20 can be produced in which a plurality of first folding sections 72a and second folding sections 72b are provided on both ends of the flat section 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 section 72a or the second folding section 72b.

The laminated electrode body 20 thus produced is placed inside a battery case and sealed to produce a secondary battery. The process of placing 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 are omitted.

As described above, a secondary battery can be manufactured using the manufacturing method disclosed herein. By performing the folding and cutting processes in the stacking process 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 stacking positions due to friction when the pressing member moves. Therefore, in the stacked electrode body 20 manufactured by this manufacturing method, the shifting of the stacking positions is prevented. And, a secondary battery equipped with the stacked electrode body 20 can effectively prevent short circuits and improve battery performance. Furthermore, with this configuration, the shifting of the stacking positions can be effectively prevented without complicating the configuration of the device.

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

Figure 5 is a diagram showing a schematic structure of the secondary battery 1 disclosed herein. The secondary battery 1 is a lithium ion secondary battery here. As shown in Figure 5, the secondary battery 1 disclosed herein is a sealed battery constructed by housing a stacked 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 stacked electrode body 20 and the electrolyte can be housed inside. The battery case 30 may be, for example, a flat rectangular battery case having an opening as shown in Figure 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.

As shown in FIG. 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 of the battery case 30 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 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.

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 planar portion 71 in the longitudinal direction of the laminated electrode body 20, and a first folded portion 72a and a second folded portion 72b at both ends of the planar portion 71. 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). As shown in FIG. 1, the positive electrode sheet 50 is arranged so that both sides in the Z direction are in contact with the separator sheet 70. Similarly, the negative electrode sheet 60 is arranged 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 insulated by the separator sheet 70.

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 stacked electrode body 20. In the stacked 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 stacked 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 stacked 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 or different. 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 are approximately equal.

In a preferred embodiment, when the width of the separator 70 at the bent portion 72 (either the first bent portion 72a or the second bent portion 72b) is taken as 100%, the separator 70 is cut by 10% or more. When the width of the separator 70 at the bent 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 of the separator 70 at the bent portion 72 is taken as 100%.

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 (here, the edge on the upper U side) in the width direction Y. 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 (here, both sides) 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 (here, the edge on the upper U side) in the width direction Y. 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 (here, the edge on the upper U side) in the width direction Y of the laminated electrode body 20. The positive electrode collector exposed portion 52a and the negative electrode collector exposed portion 62a are joined to the positive electrode collector plate 42a and the negative electrode collector plate 44a, respectively. The positive electrode collector exposed portion 52a and the positive electrode 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 electrode collector exposed portion 62a and the negative electrode collector plate 44a are electrically connected to each other, thereby electrically connecting the stacked electrode body 20 and the negative electrode terminal 44.

The positive electrode current collector constituting the positive electrode 50 may be, for example, a sheet or foil made of a metal with good conductivity, such as aluminum, an aluminum alloy, nickel, or stainless steel. Among these, 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) that can reversibly store and release 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, etc. As the conductive material, for example, a carbon material such as acetylene black (AB) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) can be used.

The negative electrode current collector constituting the negative electrode 60 may be, for example, a sheet or foil made of a metal with good electrical conductivity, such as copper, nickel, titanium, or stainless steel. Of these, copper foil is preferred 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) that can reversibly store and release charge carriers. The negative electrode active material layer may contain optional components other than the negative electrode active material, such as a binder, a dispersant, and 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.

The separator 70 is made of, for example, a porous resin substrate. Examples of the resin substrate 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 with 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 layer) made of ceramic particles or the like on its surface. The HRL may be the same as the heat-resistant layer provided in the 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.

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 used in the electrolyte of a general secondary battery 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 LiPF ₆ , LiBF ₄ , and lithium bis(fluorosulfonyl)imide (LiFSI) can be used, and among them, LiPF ₆ 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.

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 electric vehicles (BEVs). The secondary battery 1 can also be used in the form of a battery pack in which multiple batteries are connected in series and/or parallel.

Second Embodiment
In the second embodiment, a configuration in which the pressing member used in the lamination step is configured from one jig will be described.

Figure 6 is a diagram equivalent to Figure 4 according to the second embodiment, and is a diagram showing a schematic diagram of 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. It is preferable that the size of the first pressing member 221 is 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 a detailed description will be omitted.

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, the first folding portion is formed as shown in FIG. 6. In the first folding process, the first folding 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 folding 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. That is, the first pressing member 221 moves in the right direction R in FIG. 6 to be inserted between the positive electrode sheet 50 and the separator sheet 70, and after the first cutting process, it 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 the stacking position of the stacked electrode body 20 from shifting even when the first pressing member 221 is composed of a single jig. In addition, by configuring the first pressing member 221 to move in one direction in the longitudinal direction X, for example, the configuration of the device (drive mechanism) can be simplified, and the manufacturing method can be made more efficient.

Next, in the first cutting process, the separator 70 is cut in the first folded portion formed above, over the entire length in the width direction Y. As shown in FIG. 6, a cutting line C3 is set in the separator 70 roughly along the apex of the first folded portion. In the first cutting process, a cutting device (not shown) is used to cut the separator 70 over the entire length in the width direction Y along the cutting line C3. 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 produced.

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 while 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, 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, and then the first cutting process is performed. Alternatively, after the first folding process is performed, the separator sheet 70 is supplied onto the positive electrode sheet 50, and the separator 70 is pressed by the second pressing member, after which the first cutting process is performed.
In the above-mentioned second embodiment, the first pressing member 221 is taken as an example, but the same may be applied to the second pressing member. For example, when the second pressing member is constituted by one jig, the second pressing member is configured to move along the longitudinal direction X.

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 relevant field. The technology described in the claims includes various modifications and changes to the above-exemplified embodiment. For example, it is possible to replace part of the above-mentioned embodiment with other modifications, and it is also possible to add other modifications to the above-mentioned embodiment. Furthermore, if a technical feature is not described as essential, it can also be deleted as appropriate.

For example, the first pressing member may be composed of multiple jigs, and the second pressing member may be composed of one jig. Alternatively, the first pressing member may be composed of one jig, and the second pressing member may be composed of multiple jigs.

As described above, specific aspects of the technology disclosed herein include those described in the following sections.
Item 1: A manufacturing method for a secondary battery including a laminated electrode body in which a positive electrode and a negative electrode are laminated with a strip-shaped separator interposed therebetween, the manufacturing method for a secondary battery including a lamination process for 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 process including 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 in a position adjacent 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 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 width direction length of the separator at the first folded portion is 100%.
Item 3: The method for manufacturing a secondary battery described in item 1 or 2, wherein the first cutting process is carried out so as to cut 95% or less of the separator when the width direction length of the separator at the first folding portion is 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: A method for manufacturing a secondary battery described in 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 performed so as to cut the separator at least in two places in the width direction at the first folding portion.
Item 6: A 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 separators stacked in the zigzag shape, 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%.

1 Secondary battery 20 Laminated electrode body 29 Insulating film 30 Battery case 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector 44 Negative electrode terminal 44a Negative electrode current collector 50 Positive electrode (positive electrode sheet)
52a Positive electrode current collector exposed portion 60 Negative electrode (negative electrode sheet)
62a: negative electrode current collector exposed portion 70: separator (separator sheet)
71 Planar portion 72 Folding portion 72a First folding portion 72b Second folding portion 100 Manufacturing device 110 Separator supplying portion 120 Laminating portion 121 First pressing member 122 Second pressing member 130 Positive electrode supplying portion 140 Negative electrode supplying portion 221 First pressing member

Claims (4)

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 separator,
The lamination step includes:
a first bending 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. 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. 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 . 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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