WO2014027606A1

WO2014027606A1 - Electrical storage device

Info

Publication number: WO2014027606A1
Application number: PCT/JP2013/071550
Authority: WO
Inventors: 貴之弘瀬; 真也奥田; 高橋　英樹; 貴久杉本
Original assignee: 株式会社豊田自動織機
Priority date: 2012-08-14
Filing date: 2013-08-08
Publication date: 2014-02-20

Abstract

A storage cell, wherein all first tabs and/or all second tabs constitute a tab group brought together within the range of a first end to a second end of an electrode assembly in the stacking direction. The tab group includes reference tabs serving as a reference for tabs brought together in the stacking direction, and outside tabs positioned outward from the reference tabs in the stacking direction. In a first electrode or a second electrode, the length in the projecting direction from a first end part of the outside tabs is greater than the length in the projecting direction from a first end part of the reference tabs.

Description

Power storage device

The present invention provides a plurality of first electrodes each having at least one surface including an active material layer and having a first tab protruding from a part of the first end portion. A plurality of second electrodes, each having at least one surface provided with an active material layer and having a second tab protruding from a part of the first end portion. The present invention relates to a power storage device including two electrodes.

Vehicles such as EV (Elevtric Vehicle) and PHV (Plug in Hybrid Vehicle) are equipped with a secondary battery as a power storage device that stores power supplied to a traveling motor. For example, as described in Patent Document 1, a secondary battery includes, for example, a positive electrode and a negative electrode in which active material layers are formed on both surfaces. A positive electrode current collector tab protrudes from a part of one side of the positive electrode, and a negative electrode current collector tab protrudes from a part of one side of the negative electrode. And the secondary battery is equipped with the electrode assembly which laminated | stacked the positive electrode and the negative electrode through the separator. The positive electrode current collecting tab and the negative electrode current collecting tab are gathered together on one side in the stacking direction. A positive electrode lead terminal (positive electrode conductive member) is connected to the laminated positive electrode current collecting tab by welding, and a negative electrode lead terminal (negative electrode conductive member) is connected to the laminated negative electrode current collecting tab by welding.

JP 2007-234466 A

By the way, when connecting each lead terminal to each current collecting tab by welding, the closer the welded portion of the current collecting tab and lead terminal is to the electrode assembly, the more heat at welding propagates to the electrode assembly. This causes the problem that the separator melts.

An object of the present invention is to provide a power storage device that can prevent a problem from occurring in an electrode assembly due to welding of a tab and a conductive member.

In order to achieve the above object, one embodiment of the present invention is a plurality of first electrodes having a first polarity, each of which has at least one surface including an active material layer and one end of a first end. A plurality of first electrodes having a first tab protruding from the portion, and a plurality of second electrodes having a second polarity different from the first electrode, each comprising an active material layer A plurality of second electrodes having at least one surface and having a second tab protruding from a part of the first end, the active material layer of the first electrode, and the second electrode A separator disposed between an active material layer, an electrode assembly in which the first electrode, the separator and the second electrode are laminated, and a positive electrode terminal for transferring electricity between the electrode assembly, And the negative electrode terminal, both the electrode assembly, and the positive electrode terminal A negative electrode conductive member electrically connected to both the electrode assembly and the negative electrode terminal, the electrode assembly, the positive electrode terminal, the negative electrode terminal, the positive electrode conductive member, And a case in which the negative electrode conductive member is accommodated. At least one of all of the first tabs and all of the second tabs constitutes a group of tabs gathered within a range from the first end to the second end in the stacking direction of the electrode assembly. . The tab group includes a welded portion that welds all the tabs together with the positive electrode conductive member or the negative electrode conductive member. The tab group includes a reference tab serving as a reference for tabs gathered in the stacking direction, and an outer tab positioned outside the reference tab in the stacking direction. In the first electrode or the second electrode, the length of the outer tab in the protruding direction from the first end is longer than the length of the reference tab in the protruding direction from the first end.

According to this configuration, at least one of all the first tabs and all the second tabs, the outer side, that is, the tabs other than the reference tab are gathered together toward the reference tab. In this state, the outer tab is folded for gathering and the tip of the outer tab is in a lower position than before being folded. And since the welding part is formed in the position where all the tabs overlap in a lamination direction, the position of a welding part is decided according to the tab in the position where the front-end | tip is the lowest. In this embodiment, the length of the outer tab in the protruding direction is longer than the length of the reference tab in the protruding direction. For this reason, the position of the lowest tab among the outer tabs can be made higher than when all the tabs are set to the same length as the reference tab. Therefore, even if the welded portion is formed in accordance with the tab at the lowest position, the position of the welded portion can be increased, and the welded portion can be separated from the electrode assembly.

In the tab group, the height of the outer tab from the first end is preferably equal to or greater than the height of the reference tab from the first end.

According to this configuration, in the tab group, the tip of the outer tab can be positioned at the same height as or more than the tip of the reference tab, and the welded portion can be further separated from the electrode assembly.

Further, after the tab group is gathered on one side, the tab group is bent toward the side opposite to the one side, that is, the side opposite to the gathered side, and the tips of the tab group are formed on the inner surface of the case. It is preferably non-contact.

According to this configuration, it is possible to prevent the tips of the tab group from coming into contact with the inner surface of the case while adopting a configuration in which the position of the welded portion is separated from the electrode assembly.

Further, in the two outer tabs adjacent to each other in the stacking direction, the protruding direction length of the tab in a position close to the reference tab is the protruding direction of the tab in a position close to the reference tab. It is preferable that the length is shorter.

According to this configuration, the length in the protruding direction of the tab increases as it goes outward in the stacking direction, that is, away from the reference tab. The tabs on the outer side in the stacking direction have a longer bending length when gathered together, and the tip position tends to be lower than the tip of the reference tab, but by increasing the protruding direction length, The tip can be kept away from the tip of the reference tab.

Further, it is preferable that the outer tab is set so that the length in the protruding direction gradually increases from the reference tab toward the outer side in the stacking direction.

According to this configuration, the length in the protruding direction of the tab increases as it goes outward in the stacking direction, that is, away from the reference tab. Therefore, when the tab group is bent, the front end surface of the tab group can be made flat.

Further, the power storage device is preferably a secondary battery.

The perspective view which shows a secondary battery typically. The perspective view which shows typically the decomposed | disassembled electrode assembly. Sectional drawing which shows the electrode assembly inserted in the case. Sectional drawing which shows the connection state of a positive electrode current collection tab and a positive electrode electrically-conductive member. (A) is a figure which shows typically the positive electrode current collection tab in an electrode assembly, (b) is a figure which shows typically the positive electrode current collection tab in the electrode assembly of a comparative example. (A) is a figure which shows the state which gathered together the positive electrode current collection tab, and formed the positive electrode tab group, (b) is a figure which shows the state which gathered together the positive electrode current collection tab in the comparative example, and formed the positive electrode tab group. (A) is a figure which shows a negative electrode current collection tab typically, (b) is a figure which shows the state which gathered the negative electrode current collection tab and formed the negative electrode tab group. The figure which shows the manufacturing method of a positive electrode sheet typically. The figure which shows typically the other example of the manufacturing method of a positive electrode sheet. The figure which shows typically the other example of the manufacturing method of a positive electrode sheet.

Hereinafter, a power storage device according to an embodiment will be described with reference to FIGS.

As shown in FIG. 1, a secondary battery 10 as a power storage device includes a metal case 11 and an electrode assembly 20 accommodated in the case 11. The case 11 includes a rectangular box-shaped main body member 12 having a closed bottom portion and a rectangular flat plate-shaped lid member 13 that closes an opening 12 a of the main body member 12. Both the main body member 12 and the lid member 13 are made of metal, for example, stainless steel or aluminum. Further, the secondary battery 10 of the present embodiment is a square battery having a square outer shape. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

The positive electrode terminal 21 is electrically connected to the electrode assembly 20 via the positive electrode conductive member 21b. The positive electrode terminal 21 transmits and receives electricity to and from the electrode assembly 20, and the positive electrode conductive member 21 b is electrically connected to both the electrode assembly 20 and the positive electrode terminal 21. Moreover, the negative electrode terminal 22 is electrically connected to the electrode assembly 20 via the negative electrode conductive member 22b. The negative electrode terminal 22 transmits and receives electricity to and from the electrode assembly 20, and the negative electrode conductive member 22 b is electrically connected to both the electrode assembly 20 and the negative electrode terminal 22.

A part of the positive terminal 21 and a part of the negative terminal 22 are exposed to the outside of the case 11. The positive electrode terminal 21 and the negative electrode terminal 22 are respectively exposed to the outside of the case 11 through a pair of opening holes 13 a provided in parallel with the lid member 13 at a predetermined interval. In addition, a ring-shaped insulating ring 19 a for insulating from the case 11 is attached to the positive terminal 21 and the negative terminal 22, respectively.

As shown in FIG. 3, a metal main body member 12 and an insulating sheet 19 b for insulating the electrode assembly 20 are attached to the inner surface of the main body member 12 constituting the case 11. A metal lid member 13 and an insulating sheet 19 c for insulating the electrode assembly 20 are attached to the inner surface of the lid member 13 constituting the case 11. Thereby, when the electrode assembly 20 is accommodated in the case 11, the

insulating sheets

19 b and 19 c are interposed between the inner surface of the case 11 and the outer surface of the electrode assembly 20. Therefore, the case 11 and the electrode assembly 20 are electrically insulated from each other.

As shown in FIG. 2, the electrode assembly 20 includes a rectangular positive electrode sheet 30 as a first electrode and a rectangular negative electrode sheet 31 as a second electrode. The positive electrode sheet 30 includes a positive electrode metal foil 30a (in this embodiment, an aluminum foil) and a positive electrode active material layer 30b formed by applying a positive electrode active material on both surfaces thereof. That is, the positive electrode sheet 30 has two surfaces including the positive electrode active material layer 30b.

The negative electrode sheet 31 has a negative electrode metal foil 31a (copper foil in this embodiment) and a negative electrode active material layer 31b formed by applying a negative electrode active material on both surfaces thereof. That is, the negative electrode sheet 31 has two surfaces including the negative electrode active material layer 31b.

The electrode assembly 20 is a laminate in which a positive electrode sheet 30, a separator 32, and a negative electrode sheet 31 are laminated. Specifically, the electrode assembly 20 is configured by alternately laminating a plurality of positive electrode sheets 30 and a plurality of negative electrode sheets 31. Between the adjacent positive electrode sheet 30 and negative electrode sheet 31, a separator 32 that insulates both 30 and 31 from each other is interposed. That is, a set of sheet groups including the positive electrode sheet 30, the negative electrode sheet 31, and the separator 32 is formed, and the electrode assembly 20 is formed by laminating a plurality of sets of sheet groups. As shown in FIGS. 4 and 7, in the electrode assembly 20, one end portion of the positive electrode sheet 30 and the negative electrode sheet 31, that is, the end surface of the

upper end portions

30c and 31c, and the surface on which the tips of all the separators 32 are located. Is the tab side end face, that is, the upper end face 20a.

As shown in FIG. 2, the positive electrode sheet 30 is not coated with the positive electrode active material 30 d along the upper end portion 30 c of the positive electrode sheet 30, that is, along the longitudinal direction of the positive electrode sheet 30. Is formed. The positive side uncoated portion 30 d is formed with a width in the short direction of the positive electrode sheet 30. A positive electrode current collecting tab 34 as a first tab extending from the positive electrode metal foil 30 a is provided on a part of the upper end portion 30 c of the positive electrode sheet 30. The positive electrode current collecting tab 34 has a shape protruding from a part of the upper end portion 30 c of the positive electrode sheet 30.

Similarly to the positive electrode sheet 30, the negative electrode sheet 31 is not coated with the negative electrode active material along the upper end portion 31 c of the negative electrode sheet 31, that is, along the longitudinal direction of the negative electrode sheet 31. 31d is formed. The negative electrode side uncoated portion 31 d is formed with a width in the short direction of the negative electrode sheet 31. A negative electrode current collecting tab 35 as a second tab extending from the negative electrode metal foil 31a is provided on a part of the upper end portion 31c of the negative electrode sheet 31. The negative electrode current collecting tab 35 has a shape protruding from a part of the upper end portion 31 c of the negative electrode sheet 31.

In the following description, it is assumed that the positive electrode sheet 30 includes the positive electrode-side uncoated portion 30d and excludes the positive electrode current collecting tab 34. The same applies to the negative electrode sheet 31. When the sizes of the positive electrode sheet 30 (rectangular portion excluding the positive electrode current collecting tab 34) and the negative electrode sheet 31 (rectangular portion excluding the negative electrode current collecting tab 35) are compared, the positive electrode sheet 30 is more than the negative electrode sheet 31. Is also small. The lengths of the long side and the short side of the positive electrode sheet 30 (positive electrode metal foil 30a) are set shorter than the corresponding side length of the negative electrode sheet 31 (negative electrode metal foil 31a).

As shown in FIGS. 1, 4 and 7, the positive electrode sheet 30 and the negative electrode sheet 31 are laminated. The positive electrode current collecting tabs 34 are arranged in a line along the stacking direction, and the negative electrode current collecting tabs 35 are arranged in a line along the stacking direction at positions that do not overlap with the positive electrode current collecting tabs 34.

The positive electrode current collecting tab 34 is collected, that is, bundled, within one end of the electrode assembly 20 in the stacking direction, that is, within the range from the first end to the other end, that is, the second end. The positive electrode current collecting tab 34 (positive electrode tab group 40) is collected on one side and then bent toward the side opposite to the one side, that is, the side opposite to the collected side. Specifically, the positive electrode current collecting tab 34 (positive electrode tab group 40) is gathered toward one side in the stacking direction of the electrode assembly 20, and in the gathered state, on the side opposite to the one side. It is folded toward the other side in a certain stacking direction. Specifically, as illustrated in FIG. 4, the positive electrode tab group 40 is gathered near the left side in the stacking direction and folded back toward the right side.

As shown in FIG. 5A, the positive electrode current collecting tab 34 includes a single positive electrode current collecting tab 34 that protrudes in the protruding direction without being bent and deformed when gathered together. The positive electrode current collecting tab 34 is a positive electrode current collecting tab 34 that serves as a reference for collecting the plurality of positive electrode current collecting tabs 34, and is directed toward the positive electrode current collecting tab 34 from the other side in the stacking direction and the other side in the stacking direction. All the positive electrode current collecting tabs 34 are gathered together. Hereinafter, the positive electrode current collecting tab 34 serving as a reference for the gathering is referred to as a reference tab 341. Tabs other than the reference tab 341 in the positive electrode current collecting tab 34 correspond to outer tabs located outside the reference tab 341 in the stacking direction. That is, the positive electrode current collecting tab 34 includes a reference tab 341 and an outer tab located on the outer side in the stacking direction of the reference tab 341.

As shown in FIG. 6 (a), all the positive electrode current collecting tabs 34 are welded by the welded portion 38 at a position where all the positive electrode current collecting tabs 34 are overlapped in the stacking direction, and adjacent positive electrode current collecting tabs. 34 are electrically connected by a welded portion 38. Therefore, all the positive electrode current collecting tabs 34 are electrically connected in the stacking direction. Moreover, all the positive electrode current collection tabs 34 are welded with the positive electrode conductive member 21b, and all the positive electrode current collection tabs 34 are electrically connected with respect to the positive electrode conductive member 21b. And all the positive electrode current collection tabs 34 are united by welding, and the positive electrode tab group 40 is formed.

In the positive electrode tab group 40, all the positive electrode current collecting tabs 34 are brought into contact with each other by welding, and a portion formed in a plate shape without being bent and deformed is defined as an integrated portion 40b. This accumulation part 40 b is a part integrated by the weld part 41. Further, in the positive electrode tab group 40, a portion closer to the electrode assembly 20 than the accumulation portion 40b is defined as a root portion 40d.

As shown in FIG. 2, the direction in which the positive electrode current collecting tab 34 protrudes along the surface of the positive electrode sheet 30 is defined as the protruding direction of the positive electrode current collecting tab 34 and the positive electrode tab group 40, and the positive electrode current collecting along this protruding direction. The length of the tab 34 from the upper end portion 30 c (upper end surface 20 a) of the positive electrode sheet 30 is defined as the protruding length of the positive electrode current collecting tab 34. As shown in FIG. 6A, in the positive electrode tab group 40 before being bent in the stacking direction, the height from the upper end 30 c of the positive electrode current collecting tab 34 other than the reference tab 341 is the same as that at the reference tab 341. The height of the positive electrode sheet 30 is set to be the same as the height from the upper end 30c. That is, even if the positive electrode current collecting tab 34 other than the reference tab 341 is bent to form the positive electrode tab group 40, the height is set to be the same as the height of the reference tab 341.

As shown in FIG. 4, in the positive electrode tab group 40, the front end surface 40a in the protruding direction is formed into a flat surface. Therefore, the front end surface 40a of the positive electrode tab group 40 intersects perpendicularly to the surface of the positive electrode conductive member 21b opposite to the bonding surface of the positive electrode terminal 21. That is, the tips in the protruding direction of all the positive electrode current collecting tabs 34 are all aligned on the same tip surface 40a.

As shown in FIG. 6A, the welded portion 38 of the positive electrode tab group 40 is formed on the front end side including the front end surface 40 a of the positive electrode tab group 40, and the upper end portion 30 c of the positive electrode sheet 30 of the electrode assembly 20. It is formed in the position farthest from the. Furthermore, as shown in FIG. 4, in a state where the positive electrode tab group 40 is bent, the front end surface 40 a of the positive electrode tab group 40 is disposed at a position away from the insulating

sheets

19 b and 19 c of the case 11. The front end surface 40 a of the tab group 40 is not in contact with the case 11.

Similarly, the negative electrode current collecting tabs 35 are collected in a range from the first end to the second end in the stacking direction of the electrode assembly 20, that is, bundled. The negative electrode current collecting tab 35 (negative electrode tab group 42) is collected on one side and then bent toward the side opposite to the one side, that is, the side opposite to the collected side. Specifically, the negative electrode current collecting tab 35 (negative electrode tab group 42) is gathered toward one side in the stacking direction of the electrode assembly 20, and in the gathered state, on the side opposite to the one side. It is folded toward the other side in a certain stacking direction.

As shown in FIG. 7A, the negative electrode current collecting tab 35 includes a single negative electrode current collecting tab 35 that remains protruding in the protruding direction without being bent and deformed when gathered together. The negative electrode current collecting tab 35 is a negative electrode current collecting tab 35 that serves as a reference when gathering together the plurality of negative electrode current collecting tabs 35. From the one side in the stacking direction and the other side in the stacking direction toward the negative electrode current collecting tab 35. All other negative electrode current collecting tabs 35 are gathered together. Hereinafter, the negative electrode current collecting tab 35 serving as a reference for the gathering is referred to as a reference tab 351. Tabs other than the reference tab 351 among the negative electrode current collecting tabs 35 correspond to outer tabs located outside the reference tab 351 in the stacking direction. That is, the negative electrode current collecting tab 35 includes a reference tab 351 and an outer tab located on the outer side in the stacking direction of the reference tab 351.

As shown in FIG. 7B, all the negative electrode current collecting tabs 35 are welded by the welded portions 41 at positions where all the negative electrode current collecting tabs 35 are overlapped along the stacking direction, and adjacent negative electrode current collecting tabs. The 35 is electrically connected by a welded portion 41. Therefore, all the negative electrode current collection tabs 35 are electrically connected in the stacking direction. Moreover, all the negative electrode current collection tabs 35 are welded with the negative electrode conductive member 22b, and all the negative electrode current collection tabs 35 are electrically connected to the negative electrode conductive member 22b. And all the negative electrode current collection tabs 35 are united by welding, and the negative electrode tab group 42 is formed.

In the negative electrode tab group 42, a portion where all the negative electrode current collecting tabs 35 are brought into contact with each other by welding and formed in a plate shape without being bent and deformed is defined as an integrated portion 42b. The accumulation portion 42b is a portion integrated by the welded portion 41. Further, in the negative electrode tab group 42, a portion closer to the electrode assembly 20 than the accumulation portion 42b is defined as a root portion 42d.

As shown in FIG. 2, the direction in which the negative electrode current collecting tab 35 protrudes along the surface of the negative electrode sheet 31 is defined as the protruding direction of the negative electrode current collecting tab 35 and the negative electrode tab group 42, and the negative electrode current collecting along this protruding direction The length of the tab 35 from the upper end portion 31 c (upper end surface 20 a) of the negative electrode sheet 31 is defined as the protruding length of the negative electrode current collecting tab 35. As shown in FIG. 7B, in the negative electrode tab group 42 before being bent toward the other end side in the stacking direction, the height from the upper end portion 31c of the negative electrode current collecting tab 35 other than the reference tab 351 is the reference height. The height of the tab 351 from the upper end surface 20a is the same. That is, even if the negative electrode current collecting tab 35 other than the reference tab 351 is bent to form the negative electrode tab group 42, the height is the same as the height of the reference tab 351.

In the negative electrode tab group 42, the front end surface 42a in the protruding direction is formed into a flat surface. Therefore, the front end surface 42a of the negative electrode tab group 42 intersects perpendicularly to the surface of the negative electrode conductive member 22b opposite to the bonding surface of the negative electrode terminal 22. That is, all the negative electrode current collecting tabs 35 have their tips in the protruding direction aligned on the same tip surface 42a.

The welded portion 41 of the negative electrode tab group 42 is formed on the distal end side including the distal end surface 42 a of the negative electrode tab group 42, and is formed at a position farthest from the upper end surface 20 a of the electrode assembly 20. In a state where the negative electrode tab group 42 is bent in the stacking direction, the front end surface 42a of the negative electrode tab group 42 is disposed at a position away from the insulating

sheets

19b and 19c of the case 11, and the negative electrode tab group 42 The tip surface 42 a is not in contact with the case 11.

Next, the positive electrode current collecting tab 34 will be described. Since the negative electrode current collecting tab 35 is the same as the positive electrode current collecting tab 34, detailed description thereof is omitted.

As shown in FIG. 5A, the number of positive electrode current collecting tabs 34 located on one side in the stacking direction from the reference tab 341, that is, on the left side is the positive electrode positioned on the other side in the stacking direction from the reference tab 341, that is, on the right side. The number is less than the number of current collecting tabs 34. Further, the protruding lengths of the positive electrode current collecting tabs 34 before being gathered are all different along the stacking direction of the electrode assemblies 20. All the protruding lengths of the positive electrode current collecting tab 34 on the outer side in the stacking direction than the reference tab 341 are longer than the reference tab 341. Between the two positive electrode current collecting tabs 34 adjacent to each other in the stacking direction, the protruding length of the positive electrode current collector tab 34 located closer to the reference tab 341 is longer than the reference tab 341. The protruding length of the electric tab 34 is shorter. Therefore, the positive electrode current collecting tab 34 on the outer side in the stacking direction than the reference tab 341 gradually increases in protruding length from the reference tab 341 toward one side and the other side in the stacking direction.

As shown in FIGS. 5A and 6A, the protruding length of the reference tab 341 is defined as a reference length L1, and the protruding length of the positive electrode current collecting tab 34 other than the reference tab 341 is defined as a tab length L2. To do. In the present embodiment, since the protruding lengths of the positive electrode current collecting tabs 34 other than the reference tab 341 are all different, the tab lengths L2 are also all different. The tab length L2 is a length from the upper end portion 30c of the positive electrode sheet 30 (the upper end surface 20a of the electrode assembly 20) to the tip of the positive electrode current collecting tab 34 along the protruding direction. Moreover, in the positive electrode tab group 40, the protrusion length from the upper end part 30c (upper end surface 20a) in the positive electrode sheet 30 is represented by the tab group length L3. In the present embodiment, the reference length L1 of the reference tab 341 and the tab group length L3 of the positive electrode tab group 40 are set to be the same. Further, in the positive electrode current collecting tab 34 other than the reference tab 341, the length along the stacking direction from the second end of the electrode assembly 20 in the stacking direction to the outermost positive electrode current collecting tab 34 is defined as a stacking distance N.

Further, in the positive electrode current collecting tab 34 other than the reference tab 341, when the positive electrode current collecting tab 34 is bent at the base end portion (the upper end surface 20a of the electrode assembly 20) by gathering the positive electrode current collecting tabs 34, An angle formed between the positive electrode current collecting tab 34 and the upper end surface 20a is defined as a bending angle α. Further, a bending point P is a boundary between the accumulation portion 40b and the root portion 40d and a position where the positive electrode current collecting tab 34 is bent for forming the accumulation portion 40b. Then, the height from the upper end surface 20a along the protruding direction to the bending point P is defined as the root height H1, and the tip of the positive electrode current collecting tab 34 (the leading end surface of the positive electrode tab group 40) from the bending point P along the protruding direction. The height up to 40a) is defined as the height H2.

In the present embodiment, when the tab length L2 of the positive electrode current collecting tab 34 other than the reference tab 341 is set, the following formula is used.

First, the tab group length L3 of the positive electrode tab group 40 is represented by the following formula (1).

L3 = H1 + H2 ≧ L1 Formula (1)
The root height H1 is expressed by the following formula (2).

H1 = N × tan α (2)
Further, the accumulation portion height H2 is expressed by the following formula (3).

H2 = L2-N / cos α Formula (3)
When Expression (2) and Expression (3) are substituted into Expression (1), the following Expression (4) is obtained.

L2 ≧ L1 + N / cos α−N × tan α: Formula (4)
(However, in the case of α = π / 2, the reference tab 341 is shown and is excluded.)

Here, the positive electrode current collecting tabs 34 other than the reference tab 341 have different bending angles α when bent toward the positive electrode tab group 40 depending on the position in the stacking direction. Specifically, the bending angle α increases as it approaches the reference tab 341. Accordingly, the tab length L2 other than the reference tab 341 is set in accordance with the bending angle α.

When the positive electrode tab group 40 is formed by setting the bending angle α when the positive electrode current collector tab 34 is bent toward the reference tab 341 and setting the tab length L2 of the positive electrode current collector tab 34. The tips of all the other positive electrode current collecting tabs 34 are positioned on the same plane with respect to the tip of the reference tab 341. That is, the front end surface 40a of the positive electrode tab group 40 is formed in a flat surface shape. Therefore, since the tips of all the positive electrode current collecting tabs 34 are located on the front end surface 40a, all the positive electrode current collecting tabs 34 overlap in the stacking direction from the front end.

Next, the operation of the present embodiment will be described with reference to FIGS.

First, FIG. 5B and FIG. 6B illustrate a comparative example with respect to the present embodiment. As shown in FIG. 5B, in the comparative example, the protruding lengths of the positive electrode current collecting tabs 61 are all the same, and the thicknesses of the electrode assemblies 65 in the stacking direction are the same. That is, the thickness and number of the laminated positive electrode sheet, negative electrode sheet, and separator are the same as those in the embodiment. Further, the protruding length L5 of the positive electrode current collecting tab 61 of the comparative example is set to be the same as the reference length L1 of the reference tab 341 of the present embodiment. Similarly to the embodiment, the positive electrode current collecting tab 61 serving as a reference at the time of stacking is used as a reference tab 611, and the position of the reference tab 611 in the stacking direction is the same as the reference tab 341 of the embodiment.

As shown in FIG. 6B, when the positive electrode current collecting tabs 61 are gathered together with the reference tab 611 as a reference and the positive electrode tab group 60 is formed, one side (right side) and the other side of the reference tab 611 in the stacking direction. In the positive current collecting tab 61 on the (left side), the position of the tip is lower than before being bent, and is lower than the tip of the reference tab 611. For this reason, the position where all the positive electrode current collecting tabs 61 overlap in the stacking direction is located near the electrode assembly 65 from the front end of the positive electrode current collecting tab 61 on the rightmost side in the stacking direction. Therefore, when all the positive electrode current collecting tabs 61 are welded together with the conductive member 62, the welded portion 63 is formed from the rightmost positive electrode current collecting tab 61 in the stacking direction. It is positioned closer to the electrode assembly 20 than the tip of the tab 611.

In contrast, in the positive electrode tab group 40 of the present embodiment, as shown in FIG. 6A, the welded portion 38 of the positive electrode tab group 40 is formed from the tip of the reference tab 341. Therefore, as shown by the one-dot chain line in FIG. 6, in the present embodiment, the welded portion 38 is formed at a position farther from the electrode assembly 20 than the welded portion 63 of the comparative example. The negative electrode tab group 42 can also obtain the same action as the positive electrode tab group 40.

Next, a method for manufacturing the positive electrode current collecting tab 34 will be described.

As shown in FIG. 8, a positive electrode metal foil 30a formed in a long shape and a sheet shape is prepared. The length of the long side of the positive electrode metal foil 30a is longer than the length of the long side of the positive electrode sheet 30, and the length of the short side of the positive electrode metal foil 30a is set to be the same as the length of the short side of the positive electrode sheet 30. Has been. A positive electrode active material layer 30b is formed on both surfaces of the positive electrode metal foil 30a, and a positive electrode side uncoated portion 30d is formed on one long side of the positive electrode metal foil 30a.

When the positive electrode current collecting tab 34 is formed, the positive electrode side uncoated portion 30d is punched at equal intervals along the long side, and the positive electrode current collecting tab 34 is formed by the positive electrode side uncoated portion 30d remaining without being punched. It is formed. In the present embodiment, the protruding length of the positive electrode current collecting tab 34 is different in the stacking direction. Therefore, in order to make the protruding length of the positive electrode current collecting tab 34 different, before punching out the positive electrode side uncoated portion 30d, the positive electrode side uncoated portion 30d is cut along the cut line 39 shown by the one-dot chain line in FIG. Is cut stepwise along the longitudinal direction. Then, in the positive electrode side uncoated portion 30d, the length of the short side of the positive electrode metal foil 30a is gradually shortened along the longitudinal direction. Therefore, when the positive electrode side uncoated portion 30d is punched to form the positive electrode current collecting tab 34, a plurality of positive electrode sheets 30 having different lengths of the positive electrode current collecting tab 34 can be formed at a time.

According to the above embodiment, the following effects can be obtained.

(1) In all the positive electrode current collecting tabs 34 and all the negative electrode current collecting tabs 35, the protruding lengths of the

current collecting tabs

34, 35 outside the

reference tabs

341, 351 are the protrusions of the

reference tabs

341, 351. It is set longer than the length. For this reason, compared with the case where the protruding lengths of the

current collecting tabs

34 and 35 are all the same as the

reference tabs

341 and 351, the positions of the welded

portions

38 and 41 with the respective

conductive members

21b and 22b are set to the

current collecting tabs

34 and 35. The

welding portions

38 and 41 can be further separated from the electrode assembly 20. As a result, when the

conductive members

21b and 22b are welded, it is difficult for the heat to reach the electrode assembly 20, and the occurrence of a problem such that the separator 32 is melted can be prevented.

(2) In order to separate the

welds

38 and 41 from the electrode assembly 20, it is conceivable to lengthen the protruding lengths of all the

current collecting tabs

34 and 35 including the

reference tabs

341 and 351. In this case, when the formed

tab groups

40 and 42 are bent, the tip surfaces 40a and 42a may come into contact with the case 11. As in the present embodiment, the

reference tabs

341 and 351 are not lengthened, and the other

current collecting tabs

34 and 35 are extended to separate the welded

portions

38 and 41 from the electrode assembly 20 and Contact with the case 11 can be prevented.

(3) When the

tab groups

40 and 42 are formed, the heights of the

current collecting tabs

34 and 35 other than the

reference tabs

341 and 351 are set to be the same as the heights of the

reference tabs

341 and 351. For this reason, when each

tab group

40 and 42 is formed, the

welding parts

38 and 41 can be formed from the front-end | tip of the reference |

standard tabs

341 and 351. FIG. That is, the welded

portions

38 and 41 can be positioned at the tips of the

tab groups

40 and 42, and the welded

portions

38 and 41 can be most separated from the electrode assembly 20.

(4) The

current collecting tabs

34 and 35 other than the

reference tabs

341 and 351 are the

current collecting tabs

34 and 35 located closer to the

reference tabs

341 and 351 between the two

current collecting tabs

34 and 35 adjacent to each other in the stacking direction. Is shorter than the

current collecting tabs

34 and 35 located farther from the

reference tabs

341 and 351. For this reason, the protrusion length of the

current collection tabs

34 and 35 becomes long, so that it goes to the lamination direction outer side from the reference |

standard tabs

341 and 351. FIG. As the

current collecting tabs

34 and 35 on the outer side in the stacking direction are bent to form the

tab groups

40 and 42, the

current collecting tabs

34 and 35 tend to be separated from the front end surfaces 40 a and 42 a of the

tab groups

40 and 42. By making the protruding length longer, it is possible to prevent the tips of the

current collecting tabs

34 and 35 from being separated from the tip surfaces 40a and 42a.

(5) The

current collecting tabs

34 and 35 other than the

reference tabs

341 and 351 are gradually longer toward the outside in the stacking direction. For this reason, the front end surfaces 40a and 42a of the

tab groups

40 and 42 can be made flat.

(6) The reference length L1 of the

reference tabs

341 and 351, the tab length L2 of the

current collecting tabs

34 and 35, the tab group length L3 of the

tab groups

40 and 42, and the stacking distance to the tab groups 40 and 42 N, the bending angle α of each of the

current collecting tabs

34, 35, the root height H1 of each

tab group

40, 42, and the integrated portion height H2 of each

tab group

40, 42 are set, and equation (4) is set. Has been. And using this Formula (4), tab length L2 (projection length) of each

current collection tab

34 and 35 is set according to bending angle (alpha) so that it may become longer than the

reference tabs

341 and 351. FIG. be able to. Therefore, the projecting length of each of the plurality of

current collecting tabs

34 and 35 in the stacking direction can be easily set according to the stacking position, and the tabs separated from the electrode assembly 20 by the welded

portions

38 and 41. 40 and 42 can be easily manufactured.

Note that the above embodiment may be modified as follows.

○ In the

current collecting tabs

34 and 35 located outside the

reference tabs

341 and 351 in the stacking direction, the height from the

upper end portions

30c and 31c of the

sheets

30 and 31 is the same as the height in the

reference tabs

341 and 341. It may be the same or more.

○ The standard tab is not limited to one. For example, reference tabs that are adjacent to each other and have the same protruding length may be arranged at the same tip.

In the embodiment, the protruding lengths of the

current collecting tabs

34 and 35 are gradually increased from the

reference tabs

341 and 351 toward the outside in the stacking direction, but if the protruding length is longer than the

reference tabs

341 and 351, the stacking direction is increased. The lengths of the

current collecting tabs

34 and 35 adjacent to each other may be appropriately changed.

In the embodiment, the

tab groups

40 and 42 are bent, but the

tab groups

40 and 42 may not be bent.

In the embodiment, the

tab groups

40 and 42 are gathered together on the left side in the stacking direction in FIG. 4, but may be gathered together on the right side in the stacking direction in FIG.

In the embodiment, the protruding lengths of the

current collecting tabs

34 and 35 other than the

reference tabs

341 and 351 are set to the height at the tip of the

reference tabs

341 and 351 and the current collecting tab 34 when the

tab groups

40 and 42 are formed. , 35 is set to be the same as the height at the tip of 35, but is not limited thereto. The protruding length of each of the

current collecting tabs

34 and 35 other than the

reference tabs

341 and 351 is determined by the height of the

current collecting tabs

34 and 35 from the height at the tip of the

reference tabs

341 and 351 when the

tab groups

40 and 42 are formed. You may set so that the height in a front-end | tip may become high. Alternatively, if the projecting length is longer than the

reference tabs

341 and 351, the height of the

reference tabs

341 and 351 at the tip of the

reference tabs

341 and 351 when the

tab groups

40 and 42 are formed is increased. The height of may be lower.

In the embodiment, in order to make the protruding lengths of the

current collecting tabs

34 and 35 different, the positive electrode metal foil 30a and the negative electrode metal foil 31a are stepped along the longitudinal direction when the positive electrode sheet 30 and the negative electrode sheet 31 are manufactured. Although it cut, it is not restricted to this. As shown in FIG. 9, you may cut the positive electrode metal foil 30a and the negative electrode metal foil 31a diagonally along a longitudinal direction. Alternatively, as shown in FIG. 10, when the positive electrode active material is applied in the longitudinal direction of the positive electrode metal foil 30a, the positive electrode active material is intermittently applied to the positive electrode metal foil 30a, and the positive electrode metal foil 30a is extended in the longitudinal direction. Between the adjacent positive electrode active materials, a positive electrode-side uncoated portion 30d that is not coated with the positive electrode active material is formed. At this time, the positive electrode active material is applied with a certain length T in the longitudinal direction of the positive electrode metal foil 30a. Moreover, let the length of the positive electrode side uncoated part 30d along the longitudinal direction of the positive electrode metal foil 30a be S1, S2,. And the positive electrode current collection tab 34 is adjusted by adjusting the coating interval of a positive electrode active material, and adjusting the coating interval of a positive electrode active material so that length S1, S2, S3 of the positive electrode side uncoated part 30d may differ. You may make it adjust the protrusion length of.

In the embodiment, the lengths of the

current collecting tabs

34 and 35 are set in advance before the

tab groups

40 and 42 are formed. However, the lengths of the

current collecting tabs

34 and 35 are formed after the

tab groups

40 and 42 are formed. May be adjusted. For example, when the

current collecting tabs

34 and 35 having the same protruding length are gathered to one side, the heights of the upper end portions of the

current collecting tabs

34 and 35 are different from each other (see, for example, FIG. 6B). ). Then, the

tab groups

40 and 42 are cut into appropriate lengths so that the upper ends of the

current collecting tabs

34 and 35 are aligned. As a result, the protruding lengths of the

reference tabs

341 and 351 are shorter than the other

current collecting tabs

34 and 35.

According to this configuration, even if there is a manufacturing error in the protruding length of the

current collecting tabs

34 and 35, the manufacturing error can be easily absorbed by cutting the tip portion. In consideration of the cutting allowance, it is preferable that the protruding lengths of the

current collecting tabs

34 and 35 are longer than those in the above embodiment. For example, the lengths of all the

current collecting tabs

34 and 35 may be set to the same length as the longest current collecting

tabs

34 and 35 of the above embodiment.

○ Connection between the

current collecting tabs

34 and 35 and the

conductive members

21b and 22b is not limited to welding, but may be other joining forms such as riveting.

In the embodiment, the positive electrode sheet 30 has the positive electrode active material layer 30b on both sides, but the positive electrode sheet 30 may have the positive electrode active material layer 30b only on one side.

In the embodiment, the negative electrode sheet 31 has the negative electrode active material layer 31b on both sides, but the negative electrode sheet 31 may have the negative electrode active material layer 31b only on one side.

○ The number of the positive electrode sheet 30 and the negative electrode sheet 31 constituting the electrode assembly 20 may be appropriately changed.

○ The shape of the case 11 may be a columnar shape or an elliptical column shape that is flat in the left-right direction.

O The present invention may be embodied as a nickel hydride secondary battery as an electricity storage device or an electric double layer capacitor.

Claims

A power storage device,
A plurality of first electrodes having a first polarity, each having at least one surface provided with an active material layer and having a first tab protruding from a part of the first end A first electrode of
A plurality of second electrodes having a second polarity different from the first electrode, each having at least one surface provided with an active material layer and having a shape protruding from a part of the first end portion A plurality of second electrodes having a plurality of tabs;
A separator disposed between the active material layer of the first electrode and the active material layer of the second electrode;
An electrode assembly in which the first electrode, the separator and the second electrode are laminated;
A positive electrode terminal for transferring electricity to and from the electrode assembly, and a negative electrode terminal;
A positive electrode conductive member electrically connected to both the electrode assembly and the positive electrode terminal;
A negative electrode conductive member electrically connected to both the electrode assembly and the negative electrode terminal;
The electrode assembly, the positive electrode terminal, the negative electrode terminal, the positive electrode conductive member, and a case containing the negative electrode conductive member,
At least one of all of the first tabs and all of the second tabs constitutes a group of tabs gathered within a range from the first end to the second end in the stacking direction of the electrode assembly. ,
The tab group has a welded portion that welds all the tabs together with the positive electrode conductive member or the negative electrode conductive member,
The tab group includes a reference tab serving as a reference for tabs collected in the stacking direction, and an outer tab positioned on the outer side in the stacking direction than the reference tab,
In the first electrode or the second electrode, the length of the outer tab in the protruding direction from the first end is longer than the length of the reference tab in the protruding direction from the first end. apparatus.
The power storage device according to claim 1, wherein, in the tab group, a height of the outer tab from the first end is equal to or higher than a height of the reference tab from the first end.
The tab group is gathered on one side and then bent toward the opposite side of the one side, and the tips of the tab group are not in contact with the inner surface of the case. The power storage device described in 1.
In the two outer tabs adjacent to each other in the stacking direction, the length in the protruding direction of the tab that is close to the reference tab is the length in the protruding direction of the tab that is far from the reference tab. The power storage device according to any one of claims 1 to 3, wherein the power storage device is shorter.
5. The power storage device according to claim 4, wherein the outer tab is set so that a length in a protruding direction gradually increases from the reference tab toward the outer side in the stacking direction.
The power storage device according to any one of claims 1 to 5, wherein the power storage device is a secondary battery.