JP2021028896A - Manufacturing method of power storage device - Google Patents

Abstract

To provide a manufacturing method of a power storage device, capable of manufacturing an electrode with a tab having a different width with high efficiency.SOLUTION: In a manufacturing method of this power storage device, a tab 23 in which a width W2 of the tab 23 becomes gradually wider from one end side of a long direction of a metal foil 21 to the other end side is formed by forming the tab 23 by cutting one marginal part 21a of the metal foil 21 with a die roll 32 having a pair of cutting blades 35 having a different cutting width while transferring the metal foil 21 in a formation process that forms the tab 23, setting a rotational speed of the die roll 32 to an equivalent speed of a transference speed of the metal foil 21 in a period corresponding to the one marginal part 21a of each cutting blade 35, and gradually reducing the rotational speed of the die roll 32 with respect to the transference speed of the metal foil 21 at each timing of achievement of the period when each cutting blade 35 is not contacted to the one marginal part 21a of the metal foil 21.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to a method for manufacturing a power storage device.

As a power storage device, there is a device provided with an electrode body formed by winding electrodes having different polarities with a separator interposed therebetween. For example, in the power storage device described in Patent Document 1, the electrode body is arranged in the housing, and the uncoated portion of the electrode (the portion where the active material layer is not coated) is located at the central portion of the winding shaft of the electrode body. Alternatively, a portion formed by winding or folding the separator is formed. Further, in the power storage device, the laminated body is wound so that the positions of the tabs of the electrodes having the same polarity are aligned, and the tab group is formed by aligning the positions of the tabs. For example, in the square secondary battery described in Patent Document 2, the width of the tab gradually increases from the inner peripheral side to the outer peripheral side of the laminated body.

Japanese Unexamined Patent Publication No. 2013-143224 Japanese Unexamined Patent Publication No. 2018-10713

In the manufacture of the power storage device as described above, a tab corresponding to the active material layer is formed at one edge in the lateral direction of the strip-shaped metal foil in which the active material layer is intermittently coated along the longitudinal direction. The process is included. When the width of the tab is gradually widened from the inner peripheral side to the outer peripheral side of the laminated body in the electrode body, it is necessary to gradually widen the cut width at one edge of the metal foil. In Patent Document 2, a notch is formed by pressing a circular cutter against the exposed part of the current collector of the electrode at a predetermined time interval, and a tab is formed in the exposed part of the current collector, but the manufacturing efficiency is higher. A method of forming high tabs is desired.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a method for manufacturing a power storage device capable of efficiently manufacturing electrodes having tabs having different widths.

The method for manufacturing a power storage device according to one aspect of the present disclosure is a method for manufacturing a power storage device including an electrode body formed by winding electrodes having different polarities with a separator interposed therebetween, along the longitudinal direction. A forming step of forming a tab corresponding to the active material layer is provided at one edge in the lateral direction of the strip-shaped metal foil in which the active material layer is intermittently applied. In the forming step, the metal foil is cut while being conveyed. A tab is formed by cutting the one edge portion of the metal foil with a die roll having a pair of cutting blades having different widths, and the rotation speed of the die roll is equal to the transport speed of the metal foil during the period when the cutting blade hits the one edge portion. During the period when the cutting blade does not hit one edge of the metal foil, the width of the tab is made of the metal foil by gradually lowering the rotation speed of the die roll than the transport speed of the metal foil each time the period is reached. The tab is formed so as to gradually widen from one end side to the other end side in the longitudinal direction of the metal.

In this method of manufacturing a power storage device, the width of the tab is gradually increased each time the die roll cuts the edge of the metal leaf by adjusting the rotation speed of the die roll during the period when the cutting blade does not hit the edge of the metal foil. Can be expanded to. As a result, cutting by die roll can be continuously performed while conveying the metal foil, so that electrodes having tabs having different widths can be efficiently manufactured.

The method for manufacturing a power storage device according to one aspect of the present disclosure is a method for manufacturing a power storage device including an electrode body formed by winding electrodes having different polarities with a separator interposed therebetween, along the longitudinal direction. A forming step of forming a tab corresponding to the active material layer is provided at one edge in the lateral direction of the strip-shaped metal foil in which the active material layer is intermittently applied. In the forming process, a pair of press dies having different processing areas are provided. A tab is formed by cutting one edge of the metal foil with a mold, an accumulator is placed between the pair of press dies, and the length of the metal foil between the pair of press dies is adjusted by the accumulator at each press working. By gradually increasing the length, the tab is formed so that the width of the tab gradually increases from one end side to the other end side in the longitudinal direction of the metal foil.

In this method of manufacturing a power storage device, the length of the metal foil existing between a pair of press dies is adjusted by an accumulator, so that the width of the tab is gradually increased each time one edge of the metal foil is cut by press working. It can be expanded. Further, by arranging the accumulator, it is possible to continuously perform cutting by press working while transferring the metal foil between the press dies, so that it is possible to efficiently manufacture electrodes having tabs having different widths.

The accumulator may be further arranged on at least one of the front side and the rear side of the metal leaf in the transport direction of the pair of press dies. In this case, cutting by press working can be continuously performed while transporting the metal foil on the front side or the rear side in the transport direction of the metal foil as compared with the press die, so that electrodes having tabs having different widths can be more efficiently used. It becomes possible to manufacture.

According to the present disclosure, electrodes having tabs having different widths can be efficiently manufactured.

It is sectional drawing which shows the structure of the power storage device which concerns on this embodiment. It is a perspective view which shows the structure of an electrode body. It is sectional drawing which shows the layer structure of the laminated body which constitutes an electrode body. It is a top view which shows the developed shape of an electrode. It is the schematic which shows an example of the forming process. It is a figure which shows the pattern of the cutting blade in a die roll. It is the schematic which shows another example of the forming process.

Hereinafter, preferred embodiments of the method for manufacturing a power storage device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a configuration of a power storage device according to the present embodiment. The power storage device 1 is a secondary battery mounted on, for example, an industrial vehicle such as a forklift or a plug-in hybrid vehicle. The power storage device 1 is used to drive a traveling motor in the mounted vehicle. As shown in FIG. 1, the power storage device 1 includes a case 2 and an electrode body 3 housed in the case 2.

The case 2 is made of a metal such as aluminum and has a hollow rectangular parallelepiped shape. The case 2 has a bottomed rectangular box-shaped main body 4 having an opening on one side, and a rectangular plate-shaped lid 5 that closes the opening of the main body 4. An electrolytic solution is injected into the case 2. The lid portion 5 is provided with electrode terminals 6 (positive electrode terminal 6A and negative electrode terminal 6B) via an insulating member.

As shown in FIGS. 2 and 3, the electrode body 3 is composed of a sheet-like laminated body 11 having a four-layer structure in which a separator 13 is interposed between electrodes 12 (positive electrode 14 and negative electrode 15) having different polarities. ing. The sheet-shaped laminated body 11 is wound so as to be folded back at positions corresponding to both ends in the longitudinal direction of the case 2. The electrode body 3 is formed by winding the electrode 12 around the core in a spiral shape to form a wound body, then pulling out the core and compressing the spiral wound body from both sides in the radial direction. To. As a result, the electrode body 3 has an oval shape having a flat portion 11a and bent portions 11b located at both ends of the flat portion 11a when viewed from the axial direction of winding (see FIG. 3).

Next, the electrode 12 will be described. FIG. 4 is a plan view showing the developed shape of the electrode. As shown in FIG. 4, the electrode 12 has a strip-shaped metal foil 21, an active material layer 22 intermittently coated along the longitudinal direction of the metal foil 21, and a short metal foil corresponding to the active material layer 22. It has a tab 23 provided on one edge portion 21a in the hand direction. The metal foil 21 is, for example, an aluminum foil at the positive electrode 14 and a copper foil at the negative electrode 15.

The active material layer 22 is formed in a rectangular shape on both the front and back surfaces of the metal foil 21, for example. Examples of the material of the active material layer 22 forming the positive electrode 14 include composite oxides, metallic lithium, sulfur and the like. The composite oxide may include, for example, at least one of manganese, nickel, cobalt and aluminum, and lithium. Examples of the material of the active material layer 22 forming the negative electrode 15 include graphite, highly oriented graphite, mesocarbon microbeads, carbon such as hard carbon and soft carbon, alkali metals such as lithium and sodium, metal compounds, SiOx and the like. Examples include metal oxide and boron-added carbon.

In the metal foil 21, an uncoated portion 24 in which the active material is not applied is formed between the active material layer 22 adjacent to the one edge portion 21a side of the active material layer 22 in the longitudinal direction. The width (width in the longitudinal direction of the metal foil 21) W1 of the uncoated portion 24 between the active material layers 22 gradually widens toward one of the longitudinal directions of the electrode 12. The width W1 of the uncoated portion 24 between the active material layers 22 corresponds to the length of the bent portion 11b in the electrode body 3. The length of the bent portion 11b gradually increases from the inner peripheral side to the outer peripheral side of the electrode body 3, and correspondingly, the width W1 of the uncoated portion 24 between the active material layers 22 is the electrode body. It gradually widens from the inner peripheral side to the outer peripheral side of No. 3. In the electrode body 3, the laminated body 11 is wound so that the uncoated portion 24 between the active material layers 22 and the bent portion 11b coincide with each other. As a result, in the electrode body 3, the active material layer 22 is located at the flat portion 11a, and the uncoated portion 24 is located at the bent portion 11b.

The tab 23 is provided in a rectangular shape so as to project from one edge portion 21a of the metal foil 21 in the lateral direction of the metal foil 21. The tab 23 is formed by cutting one edge portion 21a of the metal foil 21 with a predetermined mold. The formation positions of the tabs 23 are unevenly distributed on one side in the longitudinal direction with respect to one active material layer 22 adjacent in the longitudinal direction of the metal foil 21, and the other adjacent in the longitudinal direction of the metal foil 21. The active material layer 22 is unevenly distributed on the other side in the longitudinal direction. The relationship between the formation positions of the tabs 23 is reversed between the positive electrode 14 and the negative electrode 15.

In the electrode body 3, as shown in FIG. 2, the positions of the tabs 23 of the electrodes 12 having the same polarity are aligned, and the tabs 25 are formed by overlapping the tabs 23. The tab group 25 of the positive electrode 14 and the tab group 25 of the negative electrode 15 are separated from each other and project in the same direction from the wound portion of the electrode body 3. The tab group 25 of the positive electrode 14 is unevenly distributed toward one bent portion 11b, and the tab group 25 of the negative electrode 15 is unevenly distributed toward the other bent portion 11b. The tab group 25 is joined to the current collecting terminal 7 by, for example, laser welding or resistance welding. The current collecting terminal 7 is electrically connected to the electrode terminal 6.

Further, the width W2 of the tab 23 (the width in the longitudinal direction of the metal foil 21) W2 gradually widens toward one of the longitudinal directions of the electrode 12, as shown in FIG. Therefore, in the spirally wound electrode body 3, as shown in FIG. 2, the width W2 of the tab 23 gradually widens from the inner peripheral side to the outer peripheral side of the laminated body 11. In the example of FIG. 1, the tabs 23 overlap each other with the centers of the tabs 23 in the width direction aligned. Therefore, the shape of the tab group 25 is a shape in which two isosceles trapezoids having the innermost circumference as the upper base and the outermost outer circumference as the lower base are butted when viewed from the axial direction of the winding.

Subsequently, the method for manufacturing the above-mentioned power storage device will be described. In the manufacturing process of the power storage device 1, a tab 23 is provided on one edge 21a of the strip-shaped metal foil 21 in which the active material layer 22 is intermittently coated along the longitudinal direction in the lateral direction corresponding to the active material layer 22. The forming step of forming is included.

FIG. 5 is a schematic view showing an example of the forming process. In the example of FIG. 5, the forming step is carried out using the rotary die-cutting device 31. As shown in FIG. 5, the rotary die-cutting device 31 includes a die roll 32, an anvil roll 33, and a pair of upper and lower nip rolls 34 arranged in front of and behind the die roll 32. The metal leaf 21 was unwound from the feeding roll with the active material layer 22 already intermittently coated, and was conveyed at a constant speed in the longitudinal direction of the metal foil 21 (here, from the right side of the paper surface to the left side of the paper surface in FIG. 5). After that, it is wound by a winding roll.

As shown in FIG. 6, a cutting blade 35 having a predetermined pattern is provided on the peripheral surface of the die roll 32. Here, the first cutting blade 35A having a short cut width and the second cutting blade 35B having a long cut width are provided on the peripheral surface of the die roll 32 in a state of being separated from each other. In the rotary die cutting device 31, the first cutting blade 35A and the second cutting blade 35B alternately hit the one edge portion 21a of the metal foil 21 conveyed at a constant speed by the rotation of the die roll 32. The tab 23 is intermittently formed by cutting the one edge portion 21a of the metal foil 21 into a rectangular shape at the portion where the first cutting blade 35A and the second cutting blade 35B hit. A cushioning material such as a sponge may be arranged around the cutting blade 35 on the peripheral surface of the die roll 32. In this case, it is possible to suppress the warp of the metal foil 21 when the metal foil 21 is sandwiched between the die roll 32 and the anvil roll 33.

The rotation speed of the die roll 32 is controlled by a control unit (not shown). The control unit sets the rotation speed of the die roll 32 to be equal to the transfer speed of the metal foil 21 during the period when the cutting blade 35 hits the edge portion 21a. On the other hand, in the period when the cutting blade 35 does not hit the one edge portion 21a of the metal leaf 21, the control unit gradually lowers the rotation speed of the die roll 32 than the transport speed of the metal leaf 21 each time the period comes. By such control, the transport distance of the metal leaf 21 from the cutting by the first cutting blade 35A to the cutting by the second cutting blade 35B can be gradually increased each time the tab 23 is formed. Therefore, the width W2 of the tab 23 can be gradually widened from one end side to the other end side in the longitudinal direction of the metal foil 21.

As described above, in the power storage device 1, in the electrode body 3 formed by winding the laminate 11 in which the separator 13 is interposed between the electrodes 12 having different polarities, the positions of the tabs 23 of the electrodes 12 having the same polarity are located. The laminated body 11 is wound so as to overlap each other. When the laminated body 11 is wound to form the electrode body 3, the diameter of the laminated body 11 increases from the inner peripheral side to the outer peripheral side. On the other hand, in the power storage device 1, the width W2 of the tab 23 gradually widens from the inner peripheral side to the outer peripheral side of the laminated body 11. Due to the dimensional tolerance of the tab 23 and the winding accuracy of the laminated body 11, the position of the tab 23 on the outer peripheral side deviates from the position of the tab 23 on the inner peripheral side when the laminated body 11 is wound. Even so, the positions of the tabs 23 can be easily aligned with each other.

In the power storage device 1, the electrode body 3 has a flat portion 11a and bent portions 11b located at both ends of the flat portion 11a when viewed from the axial direction of winding. Further, in the electrode 12, the width W1 of the uncoated portion 24 between the active material layers 22 gradually widens from the inner peripheral side to the outer peripheral side of the electrode body 3, and the active material layer 22 becomes a flat portion 11a. The uncoated portion 24 is located at the bent portion 11b. According to this configuration, since the active material layer 22 is not located at the bent portion 11b of the electrode body 3, it is possible to prevent damage due to bending from reaching the active material layer 22.

Further, in the method for manufacturing a power storage device, in the forming step, the tab 23 is formed by cutting one edge portion 21a of the metal foil 21 with a die roll 32 having a cutting blade 35 having a predetermined pattern while conveying the metal foil 21. .. At this time, during the period when the cutting blade 35 hits the one edge portion 21a, the rotation speed of the die roll 32 is equal to the transport speed of the metal leaf 21, and during the period when the cutting blade 35 does not hit the one edge portion 21a of the metal leaf 21, Each time the period is reached, the rotation speed of the die roll 32 is gradually reduced below the transfer speed of the metal foil 21. In this way, by adjusting the rotation speed of the die roll 32 during the period when the cutting blade 35 does not hit the edge portion 21a of the metal foil 21, the tab 23 is cut each time the edge portion 21a of the metal foil 21 is cut by the die roll 32. The width W2 of can be gradually widened. In this method, since the metal foil 21 can be continuously cut by the die roll 32, the electrode 12 having the tabs 23 having different widths W2 can be efficiently manufactured.

In the above embodiment, the positive electrode 14, the negative electrode 15, and the two separators 13 are laminated in advance to form the laminated body 11, and the laminated body 11 is wound while being supplied from one direction to form the electrode body 3. However, the method for manufacturing the electrode body 3 is not limited to this. For example, the positive electrode 14 and the negative electrode 15 may be supplied from different directions and wound.

FIG. 7 is a schematic view showing another example of the forming process. In the example of FIG. 7, the forming step is carried out by using the press working device 41 instead of the rotary die cutting device 31. As shown in FIG. 7, the press working apparatus 41 includes a press die 42 and an accumulator 43. Similar to the case where the rotary die-cutting device 31 is used, the metal foil 21 is fed out from the feeding roll with the active material layer 22 already intermittently coated, and is fed out from the feeding roll at a constant speed in the longitudinal direction of the metal foil 21 (here, FIG. 7). After being conveyed from the right side of the paper to the left side of the paper), it is wound by a take-up roll.

The press die 42 is composed of a first press die 42A having a short cut width and a second press die 42B having a long cut width. The first press die 42A and the second press die 42B are arranged apart from each other on the transport path of the metal foil 21. At the press position of the first press die 42A and the press position of the second press die 42B, the transfer of the metal foil 21 is temporarily stopped, and the one edge portion 21a of the metal foil 21 is cut into a rectangular shape. Tabs 23 are formed intermittently.

The accumulator 43 is used on the transport path of the metal foil 21 between the feeding roll and the first press die 42A, between the first press die 42A and the second press die 42B, and the second press die 42B. It is arranged between the press die 42B and the take-up roll, respectively. The accumulator 43 is configured to include a plurality of rollers 43a that can move up and down in the thickness direction of the metal foil 21. By moving the roller 43a of the accumulator 43A arranged between the first press die 42A and the second press die 42B up and down, the press position by the first press die 42A and the second press The length of the metal foil 21 existing between the press position of the die 42B and the press position can be gradually increased each time the tab 23 is formed. Therefore, the width W2 of the tab 23 can be gradually widened from one end side to the other end side in the longitudinal direction of the metal foil 21. Further, by arranging the accumulator 43A, the metal foil 21 can be continuously transferred between the first press die 42A and the second press die 42B while cutting by press working can be continuously performed, so that the width W2 is different. The electrode 12 having the tab 23 can be efficiently manufactured.

The accumulator 43B arranged between the feeding roll and the first press die 42A and the accumulator 43C arranged between the second press die 42B and the take-up roll are the metal leaf 21 to be conveyed. Acts as a buffer for. By arranging the accumulator 43B, it is possible to continue feeding the metal leaf 21 from the feeding roller even during a period in which the transfer of the metal leaf 21 is stopped at the pressing position of the first press die 42A. Similarly, by arranging the accumulator 43C, it is possible to continue feeding the metal foil 21 from the feeding roller even during a period in which the transfer of the metal leaf 21 is stopped at the pressing position of the second press die 42B. Therefore, the electrode 12 having the tabs 23 having different widths W2 can be manufactured more efficiently.

The present disclosure is not limited to the above embodiment. For example, in the above embodiment, in the electrode 12, the width W1 of the uncoated portion 24 between the active material layers 22 gradually widens from the inner peripheral side to the outer peripheral side of the laminated body 11, but between the active material layers 22. The width W1 of the uncoated portion 24 may be equal to each other. Further, in the above embodiment, the width W2 of the tab 23 is widened for each layer from the inner peripheral side to the outer peripheral side of the laminated body 11, but the width of the tab 23 is gradually widened for each of the plurality of layers. May be good. Further, in the above embodiment, in the tab group 25, the tabs 23 overlap each other in a state where the centers of the tabs 23 in the width direction are aligned, but the tabs are in a state where one end of the tab 23 in the width direction is aligned. 23 may overlap each other.

1 ... Power storage device, 3 ... Electrode body, 11 ... Laminated body, 12 ... Electrode, 13 ... Separator, 21 ... Metal leaf, 21a ... One edge, 22 ... Active material layer, 23 ... Tab, 32 ... Die roll, 35 ... Cutting blade, 42 ... press die, 43 ... accumulator, W1 ... width of uncoated part, W2 ... width of tab.

Claims (3)

A method for manufacturing a power storage device including an electrode body in which electrodes having different polarities are wound with a separator interposed therebetween.
A forming step of forming a tab corresponding to the active material layer is provided at one edge in the lateral direction of the strip-shaped metal foil in which the active material layer is intermittently coated along the longitudinal direction.
In the forming step,
While transporting the metal foil, the tab is formed by cutting the one edge portion of the metal foil with a die roll having a pair of cutting blades having different cutting widths.
In the period when the cutting blade hits the one edge portion, the rotation speed of the die roll is set to the same speed as the transport speed of the metal foil, and in the period when the cutting blade does not hit the one edge portion of the metal foil, the rotation speed of the period By gradually lowering the rotation speed of the die roll than the transport speed of the metal foil each time it arrives, the width of the tab gradually increases from one end side to the other end side in the longitudinal direction of the metal foil. A method for manufacturing a power storage device that forms the tab. It is a method for manufacturing a power storage device provided with an electrode body formed by winding electrodes having different polarities with a separator interposed therebetween.
A forming step of forming a tab corresponding to the active material layer is provided at one edge in the lateral direction of the strip-shaped metal foil in which the active material layer is intermittently coated along the longitudinal direction.
In the forming step,
The tab is formed by cutting the one edge portion of the metal foil with a pair of press dies having different processing areas.
By arranging an accumulator between the pair of press dies and gradually increasing the length of the metal leaf between the pair of press dies with each press working, the width of the tab becomes the metal. A method for manufacturing a power storage device in which the tab is formed so as to gradually widen from one end side to the other end side in the longitudinal direction of the foil. The method for manufacturing a power storage device according to claim 2, wherein the accumulator is further arranged on at least one of the front side and the rear side in the transport direction of the metal foil from the pair of press dies.

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