JP2013254599A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device which can prevent a tab from being split.SOLUTION: An electrode assembly 14 comprises a positive electrode housing unit 60 which is obtained by uniting a positive electrode 21, a first separator 23 covering one surface of the positive electrode 21, and a second separator 24 covering the other surface of the positive electrode 21. At one side part 21c of the positive electrode 21, a positive electrode tab 31 formed so as to project from the one side part 21c is provided. Here, a first corner part 91 is formed by the one side part 21c and a peripheral part 80 of the positive tab 31, and a second corner part 92 is formed on a tip side in a projection direction T from a first weld 61.

Description

  The present invention relates to a power storage device.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery as a power storage device that stores power supplied to the traveling motor. The secondary battery includes, for example, an electrode assembly in which a sheet-like positive electrode and a negative electrode on which an active material layer is formed are layered with a separator interposed therebetween. In addition, a tab protruding from the separator is formed on each side of the positive electrode and one side of the negative electrode, and the electric power of the electrode assembly is removed from the case by electrically connecting the tab and the conductive member. It is possible to take it out. Further, for example, Patent Document 1 describes a configuration in which the first electrode (positive electrode or negative electrode) is sandwiched between two separators, and the first electrode and each separator are unitized by joining the two separators. Yes.

JP 2008-130360 A

  Here, due to the displacement of the first electrode with respect to each separator, the tab and the joining portion of each separator may come into contact, and stress may be applied to the base end portion of the tab. In addition, stress may be applied to the base end portion of the tab due to the displacement between the first electrode and the conductive member. Then, stress may concentrate on the base end part of a tab, and the situation where a tab tears from a base end part may generate | occur | produce.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a power storage device that can suppress tab tearing.

  In order to achieve the above object, the invention according to claim 1 includes a first electrode, a first separator portion covering one surface of the first electrode, and a second separator covering the other surface of the first electrode. And a second electrode having a polarity different from that of the first electrode, in a power storage device including a layered electrode assembly, a tab protruding from one side of the first electrode, and a tab A conductive member that is bonded; and a bonding portion that bonds the first separator portion and the second separator portion, wherein the bonding portion is more distal than the one side portion of the first electrode in the protruding direction of the tab. Side and adjacent to the tab in the direction along the one side, and formed by the one side and the peripheral edge of the tab, and at least a part of the joint in the protruding direction. First corner on the base end side in the protruding direction And, at the peripheral edge of the tab, on the tip end side in the protruding direction with respect to the joint portion, passes through the center in the direction along the one side portion of the tab and along the protruding direction with respect to the first corner portion. And a second corner portion located on the tab center line side.

  According to this invention, apart from the first corner portion, which is at least partially on the proximal end side in the protruding direction with respect to the joint portion, the second corner portion on the distal end side in the protruding direction with respect to the joint portion is provided. Therefore, the stress caused by the displacement of the first electrode with respect to each separator portion is easily applied to the first corner portion, and the stress caused by the displacement of the first electrode and the conductive member is applied to the second corner portion. It becomes easy. Thereby, it can avoid that stress concentrates on one place and it can avoid that a tab tears.

  The invention according to claim 2 is characterized in that the second corner portion is located between the joint portion and a peripheral portion of each separator portion in the protruding direction. Since the second corner portion is provided, the proximal end side of the second corner portion of the tab is wider than the distal end side. In this regard, according to the present invention, since the second corner portion does not protrude from the peripheral portion of each separator portion, the wide portion of the tab is accommodated in each separator portion. Thereby, the said wide part is hard to short-circuit with a 2nd electrode. Therefore, the short circuit of both can be suppressed.

  The invention according to claim 3 is characterized in that the second corner portion is on both sides of the tab along the one side portion. According to this invention, since the second corner portions are formed on both sides in the width direction of the tab along the one side portion of the first electrode, stress is applied from any direction in the width direction. Even so, the stress can be dispersed.

  The invention according to claim 4 is characterized in that the tab is one side portion of the one side portion of the rectangular first electrode with respect to the electrode center line passing through the center of the one side portion and along the protruding direction. The second corner portion is on the electrode center line side in the peripheral portion of the tab. According to this invention, since the tab is formed at a position biased to one side in one side portion of the rectangular first electrode, when the tab is gripped and lifted, stress is applied to the peripheral portion on the sheet center side in the tab. Is easily given. In this regard, according to the present invention, since the second corner portion is formed on the side of the peripheral portion of the tab where stress is likely to concentrate, the concentration of stress can be more suitably suppressed.

  The invention according to claim 5 is characterized in that the joining portion is a welded portion in which the separator portions are welded. According to this invention, since the welding is employed as a means for joining the separator parts, a joined part having a predetermined joining strength can be realized by a relatively simple process.

  The invention according to claim 6 is characterized in that the power storage device is a secondary battery.

  According to this invention, the tearing of the tab can be suppressed.

The perspective view of a secondary battery. The exploded perspective view of an electrode assembly. The schematic diagram which shows the cross-section of a secondary battery. (A) is an enlarged view which shows a positive electrode tab and its periphery, (b) is 1-1 sectional drawing. The enlarged view which shows the positive electrode tab of another example, and its periphery. The front view which shows the positive electrode tab of another example.

  Hereinafter, a power storage device according to the present invention will be described with reference to FIGS. This power storage device is mounted on vehicles (automobiles and industrial vehicles) and is used to drive a traveling motor (electric motor) mounted on the vehicle. 3, the case 11 is shown in cross section, and the internal structure of the electrode assembly 14 and the like is shown in a front view, and in FIGS. 2 and 4, a part of the first separator 23 is cut away.

  As shown in FIG. 1, a secondary battery 10 as a power storage device is a lithium ion secondary battery, and includes a metal case 11 that forms an outer shell of the lithium ion secondary battery. The case 11 includes a rectangular box-shaped container 12 and a rectangular flat lid 13 that closes the opening of the container 12. For this reason, the secondary battery 10 has a rectangular outer shape.

  The case 11 contains an electrode assembly 14 and an electrolytic solution (not shown) as an electrolyte. As shown in FIG. 2, in the electrode assembly 14, a positive electrode 21 as a first electrode and a negative electrode 22 as a second electrode are formed of a porous film through which ions (lithium ions) related to electrical conduction can pass. In addition, layered layers are alternately stacked via the separators 23 and 24. Each of the electrodes 21 and 22 and the pair of separators 23 and 24 has a rectangular (specifically rectangular) sheet shape, and are similar to each other.

  As shown in FIG. 2, the positive electrode 21 is a positive electrode metal foil (for example, aluminum foil) 21 a formed in a rectangular shape, and a positive electrode formed by applying a positive electrode active material to the sheet surface of the positive electrode metal foil 21 a. An active material layer 21b. The positive electrode active material layer 21b is a positive electrode uncoated portion 21d having a predetermined width along the one side portion 21c of the positive electrode 21 and perpendicular to the one side portion 21c in the sheet surface of the positive electrode 21 (positive metal foil 21a). It is formed in the part except.

  The negative electrode 22 is formed to be slightly larger than the positive electrode 21. Specifically, the length of two adjacent sides of the negative electrode 22, specifically the length of each direction X and Y orthogonal to the thickness direction, is positive electrode 21. Are set longer than the lengths of the two adjacent sides, specifically, the lengths of the directions X and Y orthogonal to the thickness direction. The negative electrode 22 is formed by applying a negative electrode active material on the sheet surface of the negative electrode metal foil 22a, and a rectangular negative electrode metal foil (for example, copper foil) 22a formed slightly larger than the positive electrode metal foil 21a. Negative electrode active material layer 22b. The negative electrode active material layer 22b is a negative electrode uncoated portion 22d having a predetermined width in a direction along the one side portion 22c of the negative electrode 22 and perpendicular to the one side portion 22c in the sheet surface of the negative electrode 22 (negative electrode metal foil 22a). It is formed in the part except. The negative electrode active material layer 22b is formed larger than the positive electrode active material layer 21b so as to be able to cover the entire positive electrode active material layer 21b.

  Each separator 23, 24 is formed to be slightly larger than the positive electrode 21 and the negative electrode 22, and in detail, the length of two adjacent sides of each separator 23, 24, specifically, each direction X orthogonal to the thickness direction. , Y are set to be longer than the lengths in the respective directions X, Y of the positive electrode 21 and the negative electrode 22. That is, each separator 23 and 24 is formed in a size that can cover the sheet surfaces of the electrodes 21 and 22 in an overlapping manner.

  In the state constituting the electrode assembly 14, the entire positive electrode active material layer 21 b is covered with the negative electrode active material layer 22 b, and the positive electrode 21 and the negative electrode 22 are covered with the separators 23 and 24. In this case, a region where the positive electrode active material layer 21b and the negative electrode active material layer 22b face each other is a region contributing to charge / discharge.

  A positive electrode tab 31 formed by projecting a part of the one side portion 21c is provided on one side portion 21c of the positive electrode 21. Here, when a line passing through the center of one side 21c of the positive electrode 21 and along the protruding direction T is a sheet center line J1 (electrode center line), the positive electrode tab 31 is the sheet center line of the one side 21c of the positive electrode 21. It is formed at a position biased to one side of the direction along the one side 21c (the direction perpendicular to the direction along the protruding direction T, the second direction X) with respect to J1. Specifically, the tab center line K1 passing through the center of the positive electrode tab 31 in the direction along the one side portion 21c and along the protruding direction T is biased to one side in the direction along the one side portion 21c from the sheet center line J1. Yes.

  In other words, the plane passing through the center of the positive electrode tab 31 in the second direction X and orthogonal to the second direction X is the plane passing through the center of the positive electrode 21 in the second direction X and orthogonal to the second direction X. It can also be said that they are arranged at shifted positions. If attention is paid to the fact that the sheet center line J1 is a line passing through the center of gravity of the positive electrode 21 (the center of gravity of the portion other than the positive electrode tab 31), the positive electrode tab 31 is in a direction along the one side portion 21c rather than the center of gravity of the positive electrode 21. It can also be said that they are arranged so as to be biased toward the end side.

  Similarly, on one side 22c of the negative electrode 22, a negative electrode tab 32 formed by projecting a part of the one side 22c is provided. Similarly to the positive electrode tab 31, the negative electrode tab 32 is also formed at a position where the tab center line K <b> 2 along the protruding direction T is offset from the sheet center line J <b> 2 that is the center line of the negative electrode 22.

  For the convenience of explanation, in the following explanation, the protruding direction T of the positive electrode tab 31 is one direction from the proximal end portion to the distal end portion of the positive electrode tab 31, and the first direction (short) is the direction along the protruding direction T. The “hand direction” Y is described as both the direction from the base end portion of the positive electrode tab 31 toward the tip end portion and the opposite direction.

Further, the lengths in the directions X and Y of the positive electrode 21 are the lengths excluding the positive electrode tab 31, and the lengths in the directions X and Y of the negative electrode 22 are the lengths excluding the negative electrode tab 32.
As shown in FIG. 2, the electrodes 21 and 22 are arranged so that the same polarities of the tabs 31 and 32 are arranged in a row in the layer direction, while different polarities are not aligned in the layer direction. Specifically, the electrode 21 and 22 have the sheet center lines J1 and J2 coincide with each other, and the positive electrode tab 31 is disposed on one side via the sheet center lines J1 and J2, and the negative electrode tab 32 is disposed on the other side. Overlapping to be placed. As shown in FIG. 1, each positive electrode tab 31 is gathered toward one end side in the layer direction of the electrode assembly 14, and in the gathered state, the positive electrode tab 31 is folded back toward the side opposite to the one end side. It is. And each positive electrode tab 31 is mutually connected electrically by welding the location where each positive electrode tab 31 has overlapped. Similarly, each of the negative electrode tabs 32 is folded and welded toward the other end side in a state of being collected on one end side in the layer direction of the electrode assembly 14. The electrode assembly 14 is accommodated in the case 11 so that the portion on the side where the tabs 31 and 32 are formed and the lid 13 face each other.

  However, the present invention is not limited to this, and if the active material layers 21b and 22b face each other and the electrodes 21 and 22 are covered with the separators 23 and 24, the sheet center lines J1 and J2 are shifted to form a layer. It may be a mode.

  As shown in FIG. 1, the secondary battery 10 is a conductive member that connects the positive polarity terminal 41 and the negative polarity terminal 42 that are accessible from outside the case 11, and the same polarity of the terminals 41 and 42 and the tabs 31 and 32. The positive electrode conductive member 51 and the negative electrode conductive member 52 are provided.

  The positive terminal 41 passes through the case 11 while being insulated by the insulating ring 53. A part of the positive electrode terminal 41 is exposed outside the case 11, while another part is inside the case 11. As shown in FIG. 3, the positive electrode conductive member 51 is formed of a metal plate, one plate surface is in contact with the positive electrode tab 31, and the other plate surface is in the case 11 in the positive electrode terminal 41. It arrange | positions in the aspect which contacts an edge part. These contact points are joined (welded).

  Similarly, on the negative electrode side, the negative electrode terminal 42 penetrates the case 11 while being insulated by the insulating ring 53, and the negative electrode conductive member 52 is arranged in contact with both the negative electrode terminal 42 and the negative electrode tab 32. Each contact point is joined (welded).

  Thereby, by accessing each of the terminals 41 and 42, the electric power of the electrode assembly 14 can be taken out of the case 11, and the electric power can be supplied to the electrode assembly 14.

  As shown in FIG. 2, the electrode assembly 14 has a layered structure in which the positive electrode housing 60 in which the positive electrode 21, the first separator 23, and the second separator 24 are unitized and the negative electrode 22 are alternately overlapped. . The positive electrode container 60 will be described in detail below.

  The positive electrode housing 60 is formed by sandwiching the positive electrode 21 between the separators 23 and 24. In this case, one sheet surface (the positive electrode active material layer 21 b and the positive electrode uncoated portion 21 d) of the positive electrode 21 is covered with the first separator 23, and the other sheet surface is covered with the second separator 24.

  Here, since each separator 23 and 24 is formed larger than the positive electrode 21, in the positive electrode housing 60, a part of each separator 23 and 24 is outside the peripheral surface 21 e of the positive electrode 21 in the sheet surface direction of the positive electrode 21. It sticks out. In other words, the separators 23 and 24 include the protruding portions 23 a and 24 a that protrude from the peripheral edge portion 21 e of the positive electrode 21. Each protrusion 23a, 24a is formed along the outer peripheral edge of each separator 23, 24. Specifically, both sides of the first direction (short direction) Y along the protruding direction T of the positive electrode tab 31 in the positive electrode 21. And is formed on both sides of a second direction (longitudinal direction) X perpendicular to the direction along the protruding direction T.

  The positive electrode housing 60 includes a first welded portion (joined portion or first joined portion) 61 and a second welded portion (second joined portion) 62 for joining the separators 23 and 24 together. The 1st welding part 61 is formed by heat-processing each protrusion part 23a, 24a. As shown in FIG.4 (b), in the 1st welding part 61, a part of each protrusion part 23a, 24a is integrated by heat welding.

  As shown in FIG. 2, each welded portion 61, 62 is formed so that the positive electrode 21 is sandwiched from the first direction Y along the protruding direction T of the positive electrode tab 31. In detail, the 1st welding part 61 is arrange | positioned in the site | part by the side of the positive electrode tab 31 in each protrusion part 23a, 24a. Specifically, the first welded portion 61 includes one side portion 21c where the positive electrode tab 31 of the positive electrode 21 is formed, and each separator 23 located on the front end side in the protruding direction T of the positive electrode tab 31 from the one side portion 21c. , 24 is disposed between one side 23b and 24b. The 2nd welding part 62 is arrange | positioned on the opposite side of the 1st direction Y from the positive electrode tab 31 side in each protrusion part 23a, 24a. Specifically, the second welded portion 62 includes one side 21f on the opposite side of the positive electrode 21 from the one side 21c, and one side of each separator 23, 24 in the direction opposite to the protruding direction T from the one side 21f. It arrange | positions between the parts 23c and 24c. Thereby, the movement to the 1st direction Y (direction along the protrusion direction T) of the positive electrode 21 with respect to each separator 23 and 24 is controlled.

  Moreover, the 2nd welding part 62 is intermittently formed at predetermined intervals along the one side parts 23c and 24c of each separator 23,24. On the other hand, the first welded portion 61 is disposed adjacent to the positive electrode tab 31 (specifically, both adjacent) in the second direction X orthogonal to the direction along the protruding direction T. The 1st welding part 61 is continuously formed along the one side parts 23b and 24b of each separator 23 and 24 except the location in which the positive electrode tab 31 is formed, and is adjoining to the positive electrode tab 31. . In this case, the positive electrode tab 31 is sandwiched by the first welded portion 61 from the second direction X (the direction along the one side portion 21c, the direction perpendicular to the direction along the protruding direction T). Thereby, when the positive electrode 21 tries to move in the second direction X, the positive electrode tab 31 and the end portion 71 on the positive electrode tab 31 side of the first welding portion 61 come into contact with each other, and the movement is restricted. Thereby, the movement to the 2nd direction X (direction orthogonal to the direction along the protrusion direction T) of the positive electrode 21 with respect to each separator 23 and 24 is controlled.

  Here, as described above, in the situation where the positional deviation of the positive electrode 21 is regulated by the welded portions 61 and 62, the first welded portion 61 and the positive electrode tab 31 are brought into contact with the positive electrode tab 31. Stress. In addition, stress is applied to the positive electrode tab 31 even when the electrode assembly 14 and the positive electrode conductive member 51 are displaced. For this reason, stress tends to concentrate on the positive electrode tab 31, and the positive electrode tab 31 is easy to tear.

On the other hand, the positive electrode tab 31 of the present embodiment has a configuration for relieving the stress. The configuration will be described in detail below.
As shown in FIG. 2, the positive electrode tab 31 is formed symmetrically about the tab center line K1. The peripheral edge 80 of the positive electrode tab 31 is divided into a first peripheral edge 81 that is closer to the sheet center line J1 than the tab center line K1 and a second peripheral edge 82 that is closer to the sheet center line J1 than the tab center line K1. Is done.

  As shown in FIG. 4A, since the positive electrode tab 31 protrudes from one side portion 21c of the positive electrode 21, the one side portion 21c and the peripheral edge portion 80 of the positive electrode tab 31 (specifically, each peripheral edge portion 81, 82). As a result, two first corner portions 91 (first corner portion, first bent portion) are formed. The first corner portion 91 is formed by one side portion 21 c and base end side peripheral edge portions 81 a and 82 a extending in the protruding direction T among the peripheral edge portions 81 and 82. The first corner portion 91 is disposed on the proximal end side in the protruding direction T with respect to the first welded portion 61.

  Further, the peripheral edge portion 80 of the positive electrode tab 31 is located on the tip side in the protruding direction T from the first welded portion 61, specifically, between the first welded portion 61 and the positive electrode conductive member 51 in the protruding direction T, And the 2nd corner part 92 (2nd corner part, 2nd bending part) arrange | positioned rather than the 1st corner part 91 at the tab centerline K1 side is formed. The second corner portion 92 is formed on each of the peripheral portions 81 and 82, and is formed at a symmetrical position in each of the peripheral portions 81 and 82 via the tab center line K1.

  Describing in detail about the first peripheral edge 81 side, the second corner 92 extends in the protruding direction T of the first peripheral edge 81 and is disposed closer to the tab center line K1 than the proximal edge 81a. The distal end side peripheral edge portion 81b and the intermediate peripheral edge portion 81c continuous to the distal end side peripheral edge portion 81b and the proximal end side peripheral edge portion 81a are formed. The intermediate peripheral edge portion 81 c extends in a direction orthogonal to the thickness direction of the positive electrode tab 31 and intersecting (orthogonal) with the protruding direction T, that is, in the second direction X.

  Similarly, on the second peripheral edge 82 side, the distal end side peripheral edge 82b that extends in the protruding direction T of the second peripheral edge 82 and is disposed closer to the tab center line K1 than the proximal end peripheral edge 82a. And the 2nd corner part 92 is formed by the intermediate | middle peripheral part 82c which continues to the front end side peripheral part 82b and the base end side peripheral part 82a.

  Further, a third corner portion 93 is formed on the peripheral edge portion 80 of the positive electrode tab 31 by the corresponding ones of the intermediate peripheral edge portions 81c and 82c and the proximal end peripheral edge portions 81a and 82a. The third corner portion 93 is formed on the distal end side in the protruding direction T with respect to the first welded portion 61. For this reason, each base end side peripheral edge part 81a, 82a and the 1st welding part 61 are facing the 2nd direction X. As shown in FIG. That is, when the positive electrode 21 moves in the second direction X with respect to the separators 23 and 24, the end portion 71 of the first welded portion 61 and the base end side peripheral edge portions 81a and 82a come into contact with each other.

  Incidentally, as shown in FIG. 4A, the end portion 71 of the first welded portion 61 has a convex shape toward the positive electrode tab 31, and when the positive electrode 21 moves in the second direction X, the convex portion The distal end of the end portion 71 is in contact with the base end side peripheral edge portions 81a and 82a.

  If attention is paid to the width of the positive electrode tab 31, the positive electrode tab 31 is provided on the base end side in the protruding direction T, and the wide portion 31 a defined by the respective base end side peripheral edge portions 81 a and 82 a and the protruding direction T It can be said that it includes a narrow portion 31b provided on the distal end side and defined by the distal end side peripheral edge portions 81b and 82b. And it can be said that the level | step-difference part 31c (each intermediate | middle peripheral part 81c, 82c) is formed between the wide part 31a and the narrow part 31b. In this case, the wide portion 31 a is sandwiched between the first welded portions 61.

  Each corner portion 91 to 93 has a chamfered curved shape, and the curvature thereof is set to be the same. However, the present invention is not limited to this, and the corner portions 91 to 93 may have different curvatures. For example, the curvature of the first corner portion 91 may be smaller than the curvature of the second corner portion 92.

  Here, as shown to Fig.4 (a), the 2nd corner part 92 is settled in each protrusion part 23a, 24a. Specifically, the second corner portion 92 is disposed closer to the base end side in the protruding direction T than the one side portions 23 b and 24 b of the separators 23 and 24. As a result, the wide portion 31a (the base end side peripheral edge portions 81a and 82a and the intermediate peripheral edge portions 81c and 82c) is located on the inner side in the surface direction from the separators 23 and 24, specifically, one side portion of the separators 23 and 24. It is arranged closer to the base end side in the protruding direction T than 23b and 24b.

Next, the operation of this embodiment will be described.
A positive electrode housing 60 comprising a positive electrode 21 and a pair of separators 23 and 24 is provided, and the positive electrode housing 60 and the negative electrode 22 are alternately overlapped (laminated) to form the electrode assembly 14. In this case, the separators 23 and 24 are naturally interposed between the electrodes 21 and 22 by stacking the positive electrode container 60. Thereby, compared with the structure which piles up the positive electrode 21, the negative electrode 22, and each separator 23 and 24, respectively, reduction of the process number of a lamination process can be aimed at.

  Further, the positive electrode 21 and the pair of separators 23 and 24 are unitized in a state where the positional deviation of the positive electrode 21 with respect to the separators 23 and 24 is regulated by the welded portions 61 and 62. Specifically, as shown in FIG. 2, since the positive electrode 21 is sandwiched from the first direction Y by the welded portions 61 and 62, the positive electrode 21 moves in the first direction Y with respect to the separators 23 and 24. In this case, the positive electrode 21 and the welded portions 61 and 62 come into contact with each other, and the movement thereof is restricted. 4A, since the positive electrode tab 31 is sandwiched from the second direction X by the first welding portion 61, the positive electrode 21 is in the second direction X with respect to the separators 23 and 24. When it moves, the 1st welding part 61 and each base end side peripheral part 81a, 82a contact | abut, and the movement is controlled. Thereby, in the lamination process, the lamination process is facilitated as much as it is not necessary to align them.

  Here, when the 1st welding part 61 and each base end side peripheral part 81a, 82a contact | abut, stress is provided with respect to the positive electrode tab 31 via a contact location. In this case, the stress is preferentially applied to the first corner portion 91 located on the proximal end side in the protruding direction T with respect to the first welded portion 61. In addition, as shown in FIG. 3, when a displacement between the positive electrode conductive member 51 and the electrode assembly 14 occurs, stress is applied to the positive electrode tab 31. The stress is preferentially applied to the second corner portion 92 located on the distal end side in the protruding direction T with respect to the first welded portion 61.

  Since the second corner portion 92 is disposed in each of the protruding portions 23a and 24a, the wide portion 31a is accommodated in each of the protruding portions 23a and 24a without protruding from the separators 23 and 24. Thereby, the wide part 31a becomes difficult to contact the negative electrode 22.

According to the embodiment described in detail above, the following excellent effects are obtained.
(1) Separately from the first corner portion 91 formed on the proximal end side in the protruding direction T with respect to the first welded portion 61, the distal end side (in the protruding direction T in the protruding direction T) with respect to the first welded portion 61. A second corner portion 92 is provided between the first welded portion 61 and the positive electrode conductive member 51) and on the tab center line K <b> 1 side of the positive electrode tab 31 with respect to the first corner portion 91. Thereby, the stress caused by the positional deviation of the positive electrode 21 with respect to each separator 23, 24 and the stress caused by the positional deviation between the electrode assembly 14 and the positive electrode conductive member 51 are dispersed in the respective corner portions 91, 92. Can do. Therefore, it is possible to avoid a situation where stress concentrates on the first corner portion 91 at the base end portion of the positive electrode tab 31 and the positive electrode tab 31 is torn.

  In particular, two stresses based on different events may be in different directions. When stress in two different directions is applied to one place, it is assumed that twisting occurs at the place and the positive electrode tab 31 is easily torn. On the other hand, according to the present embodiment, the torsion can be suitably suppressed by adopting a configuration in which two corners 91 and 92 receive two stresses based on different events.

  (2) The second corner portion 92 is disposed on the base end side in the protruding direction T (the direction opposite to the protruding direction T) with respect to the one side portions 23b and 24b of the separators 23 and 24. Thereby, since the wide part 31a does not protrude from each separator 23 and 24, the wide part 31a and the negative electrode 22 are hard to short-circuit. Therefore, the short circuit of both can be suppressed.

  For example, when the wide part 31a protrudes from each separator 23 and 24, the space | interval between the wide part 31a and the negative electrode tab 32 in the 2nd direction X is more than the minimum space | interval for suppressing the short circuit of each tab 31 and 32. Must be set to On the other hand, according to this embodiment, since the wide part 31a is contained in each protrusion part 23a, 24a, if the space | interval between the narrow part 31b and the negative electrode tab 32 is set more than the said minimum space | interval. The step size of the step portion 31c can be shortened. Thereby, the tabs 31 and 32 can be arranged close to each other, and the dead space between the tabs 31 and 32 can be reduced.

  (3) The second corner portion 92 is formed on each of the peripheral edge portions 81 and 82. Thereby, even if it is a case where stress is given from any direction (direction which goes to the negative electrode tab 32 side from the positive electrode tab 31 side, or the reverse direction) of the 2nd direction X, the said stress can be disperse | distributed. it can.

  (4) Each welding part 61, 62 was provided as what joins each separator 23,24. Here, welding is realized by a relatively simple heat treatment, and the welding portions 61 and 62 can be formed at desired locations by controlling the heat treatment locations. Thereby, the process for unitizing the positive electrode 21 and each separator 23 and 24 can be simplified.

  On the other hand, since each welding part 61 and 62 is hard to elastically deform compared with another location, the stress resulting from the position shift of the positive electrode 21 with respect to each separator 23 and 24 is not easily absorbed by the first welding part 61. . For this reason, the stress applied to the positive electrode tab 31 is not easily relaxed. In such a situation, when stress based on different events concentrates on the first corner portion 91, excessive stress is applied to the first corner portion 91, and the first corner portion 91 is easily torn.

  On the other hand, according to the present embodiment, by forming the second corner portion 92, the stress applied to the first corner portion 91 can be relieved through the ability to distribute the stress based on different events. can do. Thereby, in the structure which employ | adopted welding as what joins each separator 23 and 24, the tearing of the positive electrode tab 31 can be suppressed suitably.

In addition, you may change the said embodiment as follows.
In the embodiment, the base side peripheral edge portions 81a and 82a are configured to contact the first welded portion 61. However, the present invention is not limited to this, and the first corner portion is configured to contact the first welded portion 61. May be. For example, as shown in FIG. 5, a positive electrode tab 100 in which the corner portions 101 to 103 are continuously formed is provided. The first corner portion 101 has one end (continuous point with the one side portion 21c) 101a on the proximal end side in the protruding direction T from the first welded portion 61, and the other end (continuous point with the second corner portion 102). 101b is located on the front end side in the protruding direction T from the first welded portion 61. Even in such a configuration, it is possible to distribute two stresses based on different events. In short, at least a part of the first corner portion only needs to be closer to the base end side in the protruding direction T than the position of the first welding portion 61 in the protruding direction T.

  In embodiment, although the 2nd corner part 92 was formed in each peripheral part 81 and 82, respectively, it is not restricted to this. For example, as shown in FIG. 6, a positive electrode tab 110 in which the second corner portion 92 is formed only on the first peripheral portion 81 side and the second corner portion 92 is not formed on the second peripheral portion 82 side. Also good. Even in this case, the stress applied when the positive electrode tab 110 is gripped can be suitably dispersed. Specifically, in a configuration in which the tab center line K1 of the positive electrode tab 110 is deviated from the sheet center line J1 (center of gravity), when the positive electrode tab 110 is gripped and lifted, the positive electrode tab 110 is on the sheet center line J1 side. The stress tends to concentrate on the first peripheral edge 81 side. In this regard, according to this example, since the second corner portion 92 is formed on the first peripheral edge portion 81 side, on which stress is easily concentrated, it is possible to favorably distribute the stress.

  The tabs 31 and 32 may be close to the sheet center lines J1 and J2 of the electrodes 21 and 22, respectively. For example, when the electrodes 21 and 22 are stacked, the narrow portion 31b of the positive electrode tab 31 and the negative electrode tab 32 are separated from each other by an interval equal to or smaller than the step size of the step portion 31c (the length in the second direction X). The positions of the tabs 31 and 32 may be set. Even in this case, since the wide portion 31a is accommodated in the separators 23 and 24, the tabs 31 and 32 are not easily short-circuited. Thereby, the dead space between the tabs 31 and 32 can be reduced.

  In the embodiment, a pair of separators 23 and 24 formed separately are used as sandwiching the positive electrode 21, but the present invention is not limited to this, and the one that folds an integrated separator and accommodates the positive electrode 21 therein It may be adopted. In this case, the bent part of the integral separator functions as a joint part. In short, the first separator portion and the second separator portion may be integrated or separate.

  In the embodiment, the first welds 61 are formed on both sides of the positive electrode tab 31 in the second direction X so as to sandwich the positive electrode tab 31 from the second direction X orthogonal to the direction along the protruding direction T. It is not restricted to this, It is good also as a structure by which the 1st welding part 61 is formed next to either one side. In this case, it is preferable to separately provide a restricting portion for restricting movement to the other side.

  In the embodiment, the first welded portion 61 is continuously formed except for the portion where the positive electrode tab 31 is interposed, and the second welded portion 62 is formed intermittently. There may be. Further, not only in the first direction Y, but also on the both sides of the positive electrode 21 in the second direction X, welded portions as bonding portions may be provided.

  In the embodiment, welding is adopted as a means for joining the separators 23 and 24, but the joining mode is not limited to this and is arbitrary. For example, it may be configured to be affixed with a double-sided tape, may be configured to be filled with an adhesive, or may be configured to be joined by stitching.

  In embodiment, although the positive electrode 21 was employ | adopted as what is covered (wrapped) with each separator 23 and 24, it is not restricted to this, The negative electrode 22 may be employ | adopted. In this case, the shape of the negative electrode tab 32 may be the shape of the positive electrode tab 31.

  In embodiment, although the positive electrode 21, the negative electrode 22, and each separator 23 and 24 were formed in the rectangular shape, it is not restricted to this, You may form in square shape. Moreover, it is not restricted to rectangular shape, For example, you may form in polygonal shapes other than square shape, and may be formed in ellipse shape.

In the embodiment, the negative electrode 22 is formed slightly smaller than the separators 23 and 24. However, the present invention is not limited to this, and both may have the same shape.
In embodiment, although the secondary battery 10 was a lithium ion secondary battery, it is not restricted to this, Other secondary batteries, such as nickel hydride, may be sufficient. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge.

In the embodiment, the secondary battery 10 is mounted on the vehicle, but is not limited thereto, and may be mounted on another device.
In embodiment, although the 2nd welding part 62 as a 2nd junction part was provided, it is not restricted to this, You may abbreviate | omit the 2nd welding part 62. FIG. However, the point where the positional relationship between each of the corner portions 91 and 92 and the first welded portion 61 is defined, that is, the movement of the positive electrode 21 in the first direction Y is restricted by the welded portions 61 and 62. If it pays attention to, it is better to provide the 2nd welding part 62. FIG.

The present invention may be applied to other power storage devices such as electric double layer capacitors.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) The joint is a first joint, and is provided separately from the first joint. The first joint is on the opposite side of the tab along the protruding direction, and the first joint is the first joint. The power storage device according to claim 1, further comprising a second joint portion that sandwiches the first electrode in cooperation with the joint portion.

  (B) The power storage device according to any one of claims 1 to 6 and technical concept (a), wherein the joint portion sandwiches the tab from a direction along the one side portion.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery (power storage device), 14 ... Electrode assembly, 21 ... Positive electrode (first electrode), 22 ... Negative electrode (second electrode), 23 ... First separator, 24 ... Second separator, 23b, 24b ... One side part (peripheral part) of each separator, 31 ... positive electrode tab, 51 ... positive electrode conductive member, 61 ... first weld part (joint part or first joint part), 62 ... second weld part (second joint part), 80 ... peripheral edge of positive electrode tab, 91 ... first corner part, 92 ... second corner part, J1 ... sheet center line (electrode center line), K1 ... tab center line (center line of positive electrode tab).

Claims (6)

A first electrode;
A first separator portion covering one surface of the first electrode;
A second separator portion covering the other surface of the first electrode;
A second electrode having a polarity different from that of the first electrode;
In a power storage device including an electrode assembly in which are stacked in layers,
A tab protruding from one side of the first electrode;
A conductive member joined to the tab;
A joining part for joining the first separator part and the second separator part;
With
The joint is on the tip side in the protruding direction of the tab from the one side of the first electrode and next to the tab in the direction along the one side,
A first corner portion formed by the one side portion and a peripheral edge portion of the tab, and at least a part of the first corner portion being located on a proximal end side in the protruding direction with respect to a position of the bonding portion in the protruding direction;
The center of the tab in the peripheral edge of the tab, which is closer to the leading end in the protruding direction than the joint, passes through the center of the tab along the one side, and extends in the protruding direction than the first corner. A second corner located on the line side;
A power storage device comprising:   The power storage device according to claim 1, wherein the second corner portion is located between the joint portion and a peripheral portion of each separator portion in the protruding direction.   3. The power storage device according to claim 1, wherein the second corner portion is on both sides of the tab in a direction along the one side portion. 4. The tab is biased to one side in the direction along the one side with respect to the electrode center line passing through the center of the one side of the one side of the rectangular first electrode and along the protruding direction. In the position
3. The power storage device according to claim 1, wherein the second corner portion is on the electrode center line side in a peripheral portion of the tab.   The power storage device according to any one of claims 1 to 3, wherein the joining portion is a welded portion in which the separator portions are welded.   The power storage device according to claim 1, wherein the power storage device is a secondary battery.