JP2014072008A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain reduction of a battery output due to lamination deviation of an electrode.SOLUTION: Bent portions 30 bent in a bending direction X are provided at four corners of a positive electrode 19. Also, bent portions 31 bent in the bending direction X are provided at four corners of a negative electrode 20. Then, the bent portions 30, 31 are provided so that they are overlaid on each other in a lamination direction when the positive electrode 19 and the negative electrode 20 are laminated. Thereby, when the positive electrode 19 and the negative electrode 20 are laminated, the bent portions 30 of the positive electrode 19 and the bent portions 31 of the negative electrode 20 are overlaid on each other, and therefore, movement of the electrodes can be restrained to restrain lamination deviation. Also, even when an electrode assembly constituted by the positive and negative electrodes 19, 20 having the bent portions 30, 31 is housed in a case, the bent portions 30, 31 are overlaid on each other, and therefore, the movement of the electrodes can be restrained to restrain lamination deviation.

Description

  The present invention relates to a power storage device in which an electrode assembly is accommodated in a case.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores power supplied to an electric motor serving as a prime mover. This type of secondary battery is disclosed in Patent Document 1, for example. The secondary battery has an electrode assembly in which a negative electrode in which a negative electrode active material is applied to a metal foil and a positive electrode in which a positive electrode active material is applied to a metal foil are insulated and laminated. And the electrode assembly is accommodated in the case of a secondary battery.

Japanese Patent Laid-Open No. 9-120836

In the secondary battery, if the stacking misalignment between the positive electrode and the negative electrode occurs when the electrode assembly is housed in the case, the battery output is reduced.
This invention was made paying attention to the problem which exists in such a prior art, and the objective is to provide the electrical storage apparatus which can suppress the fall of the battery output by the lamination | stacking deviation of an electrode. .

  In order to solve the above problems, the invention according to claim 1 is an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, and a case in which the electrode assembly is accommodated. The positive electrode and the negative electrode each have a bent portion bent in the stacking direction of the electrode assembly on each surface, and the electrode assembly includes the bent portions Each of which has a bent laminated portion that is overlapped in the stacking direction of the electrode assembly, and each of the bent portions takes the electrode assembly out of the case in a restrained state in which the electrode assembly is accommodated in the case. The gist is that the curvature or the bending angle is smaller than that in the released state.

  According to this, the bending part provided in the positive electrode and the negative electrode overlaps with each other in the stacking direction, so that the stacking deviation between the positive electrode and the negative electrode is suppressed when the electrode assembly is accommodated in the case. That is, when the electrode assembly is accommodated in the case, the bending portion is reduced in curvature or bending angle, and stress is generated to return to the bending direction. Thereby, the bending part of a positive electrode and the bending part of a negative electrode maintain the state which overlapped even after the electrode assembly was accommodated. And even if one electrode tries to move relative to the other electrode, the movement is restricted because the bent portions overlap each other. Therefore, a decrease in battery output due to electrode stacking deviation can be suppressed.

  The invention according to claim 2 is characterized in that, in the power storage device according to claim 1, the electrode assembly includes a plurality of the bent laminated portions, and the bent laminated portions do not overlap each other. According to this, since it has provided so that several bending lamination | stacking parts may not overlap, the movement of an electrode can be controlled reliably and lamination | stacking shift | offset | difference can be suppressed.

  According to a third aspect of the present invention, in the power storage device according to the second aspect, the extending direction of the bent portion constituting the one bent laminated portion, and the bent portion constituting the other bent laminated portion, The gist of this is that the extending direction is different. According to this, the movement of the electrode can be reliably controlled, and the stacking deviation can be suppressed.

  The invention according to claim 4 is the power storage device according to claim 3, characterized in that the bent portion has at least four passing through two adjacent sides of the positive electrode and the negative electrode. . According to this, with a simple configuration, it is possible to regulate the movement of the electrodes and suppress the stacking deviation. Moreover, it becomes easy to perform the process of laminating | stacking a positive electrode and a negative electrode.

  According to a fifth aspect of the present invention, in the power storage device according to the second or third aspect, the bent portion is bent in a first bent portion bent in one of the stacking directions and in the other of the stacked directions. 2 bending parts, and the bending lamination part includes a first bending lamination part constituted by the first bending parts and a second bending lamination part constituted by the second bending parts. The gist. According to this, with a simple configuration, it is possible to regulate the movement of the electrodes and suppress the stacking deviation. Moreover, it becomes easy to perform the process of laminating | stacking a positive electrode and a negative electrode.

  A sixth aspect of the present invention is summarized as the power storage device according to any one of the first to fifth aspects, wherein the power storage device is a secondary battery.

  According to the present invention, it is possible to suppress a decrease in battery output due to electrode stacking deviation.

The exploded perspective view of a secondary battery. The perspective view which shows the external appearance of a secondary battery. The disassembled perspective view which shows the component of an electrode assembly. FIG. 3 is a perspective view showing a positive electrode, a negative electrode, and a separator in the first embodiment. The end view which shows the lamination | stacking state of the positive electrode in 1st Embodiment, a negative electrode, and a separator. Explanatory drawing explaining the manufacturing process of an electrode. The perspective view which shows the positive electrode in 2nd Embodiment. The end elevation which shows the lamination | stacking state of the positive electrode in 2nd Embodiment, a negative electrode, and a separator. The perspective view which shows the positive electrode in 3rd Embodiment. The end elevation which shows the lamination | stacking state of the positive electrode in 3rd Embodiment, a negative electrode, and a separator. Explanatory drawing explaining another example.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, an electrode assembly 12 is accommodated in a case 11 in a secondary battery 10 as a power storage device. The case 11 includes a bottomed square cylindrical case body 13 and a rectangular flat plate-like lid body 14. The lid body 14 closes the insertion port for inserting the electrode assembly 12 into the case main body 13. Both the case main body 13 and the lid body 14 are made of metal (for example, stainless steel or aluminum). Further, the inner surface of each side wall erected from the bottom wall of the case body 13 is a flat surface. Further, the secondary battery 10 of the present embodiment is a prismatic battery whose appearance is square. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

  Each of the positive electrode terminal 15 and the negative electrode terminal 16 that exchange electricity with the electrode assembly 12 is electrically connected to the electrode assembly 12. A part of each of the positive electrode terminal 15 and the negative electrode terminal 16 is exposed to the outside of the case 11 through a pair of opening holes 17 arranged in parallel with the lid body 14 at a predetermined interval. Further, a ring-shaped insulating ring 18 for insulating from the case 11 is attached to each of the positive terminal 15 and the negative terminal 16.

  As shown in FIG. 3, the electrode assembly 12 includes a sheet-like positive electrode 19, a sheet-like negative electrode 20, and a separator 21 that insulates between the positive electrode 19 and the negative electrode 20. The electrode assembly 12 is configured by alternately laminating separators 21 between a plurality of positive electrodes 19 and a plurality of negative electrodes 20. That is, the electrode assembly 12 is provided with a plurality of sets each including the positive electrode 19, the negative electrode 20, and the separator 21.

  The positive electrode 19 has a positive metal foil (aluminum foil in this embodiment) 22 and a positive electrode active material layer 23 on both surfaces thereof. A positive electrode current collecting tab 24 made of a positive electrode metal foil 22 is provided so as to protrude from an edge portion 19 a as one end of the positive electrode 19. The positive electrode current collecting tab 24 constitutes an uncoated portion where no positive electrode active material is applied. In addition, the positive electrode current collecting tab 24 is formed in the same position and in the same shape in each positive electrode 19 constituting the electrode assembly 12.

  The negative electrode 20 has a negative electrode metal foil (copper foil in this embodiment) 25 and a negative electrode active material layer 26 on both surfaces thereof. Further, a negative electrode current collecting tab 27 made of a negative electrode metal foil 25 is provided so as to protrude from an edge portion 20 a as one end of the negative electrode 20. The negative electrode current collecting tab 27 constitutes an uncoated portion where no negative electrode active material is applied. Further, the negative electrode current collecting tab 27 is formed in the same shape at the same position in each negative electrode 20 constituting the electrode assembly 12. Further, the negative electrode current collecting tab 27 is provided at a position where the positive electrode current collecting tab 24 does not overlap with the positive electrode current collecting tab 24 when the positive electrode 19 and the negative electrode 20 are laminated.

  The positive electrodes 19 constituting the electrode assembly 12 are stacked such that the respective positive electrode current collecting tabs 24 are arranged in a row along the stacking direction. Similarly, each negative electrode 20 constituting the electrode assembly 12 is laminated such that the respective negative electrode current collecting tabs 27 are arranged in a row along the laminating direction so as not to overlap the positive electrode current collecting tabs 24. The And the positive electrode current collection tab 24 of each positive electrode 19 is electrically connected with the positive electrode terminal 15, as shown in FIG. Similarly, the negative electrode current collecting tab 27 of each negative electrode 20 is electrically connected to the negative electrode terminal 16 as shown in FIG.

  As shown in FIG. 3, the positive electrode 19 has a quadrangular region excluding the positive current collecting tab 24. Then, bending lines L1 extending obliquely toward two adjacent sides are located at the four corners of the positive electrode 19. Further, as shown in FIG. 3, the negative electrode 20 has a quadrangular region excluding the negative current collecting tab 27. Then, bending lines L2 extending obliquely toward two adjacent sides are located at the four corners of the negative electrode 20. The bending lines L1 and L2 are lines indicating folds.

  As shown in FIG. 4, when the positive electrode 19 is laminated in the manufacturing process of the electrode assembly 12, the triangular bent portions 30 are provided at the four corners 19 b to 19 e serving as the four corners. A bending line L <b> 1 is positioned on the surface of the positive electrode 19 by the bending portion 30. The positive electrode 19 passes through two adjacent sides and has four bent portions 30. And each bending part 30 is bent in the same direction (bending direction X in a figure) in the lamination direction of an electrode. In addition, the bent portions 30 are provided on the surface of the positive electrode 19 so that the bent portions 30 do not overlap each other.

  Further, each bending portion 30 is provided so that each bending line L1 does not intersect on the surface of the positive electrode 19. And each bending line L1 of each bending part 30 differs in the extending direction. For this reason, the bending lines L1 do not intersect on the surface of the positive electrode 19, but when they extend outside the surface of the positive electrode 19 as shown by the alternate long and short dash line in the figure, they intersect outside the surface. And each bending line L1 is extended so that two adjacent orthogonal | vertical sides of the positive electrode 19 may be straddled, and the bending part 30 bent by making the bending line L1 into a crease | fold is orthogonally adjacent to the positive electrode 19. You will pass through two sides. Each bending portion 30 is bent at a bending angle α so as to be gently bent. The bending angle α indicates the amount of bending when the four corners of the positive electrode 19 are bent in the bending direction X.

  Further, as shown in FIG. 4, when the negative electrode 20 is laminated in the manufacturing process of the electrode assembly 12, like the positive electrode 19, the four corners 20b to 20e serving as the four corners are bent in a triangular shape. A part 31 is provided. A bending line L <b> 2 is positioned on the surface of the negative electrode 20 by the bending portion 31. The negative electrode 20 passes through two adjacent sides and has four bent portions 31. And each bending part 31 is bent in the same direction (bending direction X in a figure) in the lamination direction of an electrode. The bent portions 31 are provided on the surface of the negative electrode 20 so that the bent portions 31 do not overlap each other.

  In addition, each bending portion 31 is provided so that each bending line L <b> 2 does not intersect on the surface of the negative electrode 20. And each bending line L2 of each bending part 31 differs in the extending direction. For this reason, each bend line L2 does not intersect on the surface of the negative electrode 20, like each bend line L1 of the positive electrode 19, but when it extends outside the surface of the negative electrode 20, Intersect. Each bend line L2 extends so as to straddle two adjacent orthogonal sides of the negative electrode 20, so that the bent portion 31 bent with the bend line L2 as a crease is adjacent to the negative electrode 20. You will pass through two sides. Each bending portion 31 is bent so as to be gently bent at a bending angle α.

  The bend line L1 of the positive electrode 19 and the bend line L2 of the negative electrode 20 overlap in the stacking direction when the positive electrode 19 and the negative electrode 20 are stacked. That is, when the positive electrode 19 and the negative electrode 20 are stacked, the bending lines L1 and L2 positioned at the corners overlapping in the stacking direction have the same extending direction.

  As shown in FIG. 5, the positive electrode 19 and the negative electrode 20 provided with the bent portions 30 and 31 are sequentially stacked with the bending directions of the bent portions 30 and 31 being the same direction. Thereby, the bending part 30 of each positive electrode 19 and the bending part 31 of each negative electrode 20 overlap in the lamination direction. In the present embodiment, the separator 21 is not provided with a bent portion like the positive electrode 19 and the negative electrode 20. The separator 21 is thinner than the positive electrode 19 and the negative electrode 20. Therefore, when the separator 21 is laminated between the positive electrode 19 and the negative electrode 20, the separator 21 is bent so as to follow the bent portions 30 and 31 of the positive electrode 19 and the negative electrode 20. Then, the electrode assembly 12 in which the required number of positive electrodes 19 and negative electrodes 20 are stacked is in a state in which a bent stacked portion H1 in which the bent portions 30 and 31 overlap with each other in the stacking direction is provided. In the electrode assembly 12, the positive electrode 19 and the negative electrode 20 have a plurality of bent portions 30 and 31, whereby a plurality of bent laminated portions H1 are provided. In the electrode assembly 12, the plurality of bending laminated portions H1 are not overlapped with each other. Moreover, the extending direction of the bending parts 30 and 31 which comprise the one bending laminated part H1 differs from the extending direction of the bending parts 30 and 31 which comprise the other bending laminated part H1.

  The electrode assembly 12 laminated in this way is accommodated in the case main body 13 as shown in FIG. 1 with the bending laminated portion H1 provided. That is, each corner of the electrode assembly 12 is bent by the bending lines L1 and L2 before being housed in the case 11 (case body 13).

Hereinafter, the operation of the present embodiment will be described.
The bent portions 30 and 31 of the positive electrode 19 and the negative electrode 20 function as means for suppressing the stacking deviation between the positive electrode 19 and the negative electrode 20 in the process of stacking the positive electrode 19 and the negative electrode 20. In other words, the bent portions 30 and 31 are provided at the four corners of the positive electrode 19 and the negative electrode 20 with the extending directions of the bending lines L1 and L2 being different. When the positive electrode 19 and the negative electrode 20 are stacked, the bent portion 30 of the positive electrode 19 and the bent portion 31 of the negative electrode 20 overlap in the stacking direction. Therefore, for example, when the positive electrode 19 is laminated on the negative electrode 20, the positive electrode 19 has its bent portion 30 overlapped with the bent portion 31 of the negative electrode 20, so that movement of the electrode itself in the vertical and horizontal directions is restricted. . For example, when the positive electrode 19 is about to move in the lateral direction Y1 shown in FIG. 4, the bent portion 30 of the positive electrode 19 overlaps with the bent portion 30 and is caught by the bent portion 31 of the negative electrode 20 located in the moving direction. . For example, when the positive electrode 19 is about to move in the longitudinal direction Y2 shown in FIG. 4, the bent portion 30 of the positive electrode 19 overlaps the bent portion 30 and bends 31 of the negative electrode 20 located in the moving direction. Get caught in. Thereby, the movement of the positive electrode 19 in the horizontal direction Y1 and the vertical direction Y2 is restricted by the overlapping of the bent portions 30 and 31.

  On the other hand, when the electrode assembly 12 in which the bending laminated portion H1 in which the bending portions 30 and 31 overlap in the lamination direction is provided is inserted into the case 11, the electrode assembly 12 receives a load from the lamination direction of the electrode assembly 12 at the time of insertion. . For this reason, each bending part 30 and 31 which comprises the bending lamination | stacking part H1 returns to the direction opposite to the bending direction X by the effect | action of the load received when the electrode assembly 12 is accommodated. Thereby, the bending state of each bending part 30 and 31 is eased. That is, the bending angle α of each of the bent portions 30 and 31 is smaller in the restrained state where the electrode assembly 12 is accommodated in the case 11 than in the released state where the electrode assembly 12 is moved out of the case 11. Specifically, the bending angle returns to a state close to “0 degree”. In addition, the state where the bending angle is “0 degree” means that the bent portions 30 and 31 return to a state where they form a flat surface and an unbent electrode surface.

  In addition, the thickness in the stacking direction of the electrode assembly 12 in the released state and the electrode assembly 12 in the constrained state changes when the bent portions 30 and 31 return to their original state after being accommodated in the case 11. That is, the thickness of the electrode assembly 12 in the restrained state is smaller than the thickness of the electrode assembly 12 in the released state.

  And in the electrode assembly 12 accommodated in the case 11, the stress which tries to return to the state in which each bending part 30 and 31 which comprises the bending lamination | stacking part H1 is bent is acting. For this reason, the bending part 30 of the positive electrode 19 and the bending part 31 of the negative electrode 20 at the time of lamination | stacking are maintained. Therefore, even after the electrode assembly 12 is accommodated, for example, when the positive electrode 19 is about to move with respect to the negative electrode 20, the bent portion 30 of the positive electrode 19 is caught by the bent portion 31 of the negative electrode 20, and the movement is Be regulated.

  In addition, as shown in FIG. 6, the bending part 30 of the positive electrode 19 and the bending part 31 of the negative electrode 20 are provided together when shape | molding these electrodes. The positive electrode 19 and the negative electrode 20 are produced by applying a paste-like electrode material 33 containing an active material or the like to the metal foil 32 and drying it, and then punching it to a desired electrode size. And each bending part 30 and 31 is provided by press-molding simultaneously with punching, when punching out the electrode 34 shown with a dashed-two dotted line from the metal foil 32, as shown in FIG.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) The bending portions 30 and 31 provided in the positive electrode 19 and the negative electrode 20 overlap each other in the stacking direction, so that the stacking displacement between the positive electrode 19 and the negative electrode 20 is reduced when the electrode assembly 12 is accommodated in the case 11. Can be suppressed. That is, even if one electrode tries to move with respect to the other electrode, the movement can be regulated by the overlapping of the bent portions 30 and 31. Accordingly, it is possible to suppress a decrease in battery output due to electrode stacking deviation.

  (2) Further, not only when the electrode assembly 12 is accommodated in the case 11, but also in the manufacturing process of laminating the positive electrode 19 and the negative electrode 20, stacking deviation can be suppressed by the overlapping of the bent portions 30 and 31. . Therefore, the workability of the process of laminating the positive electrode 19 and the negative electrode 20 can be improved.

(3) Since there are a plurality of bending portions 30 and 31 and the bending portions 30 and 31 are provided at positions where they do not overlap on the surface of the electrode, the movement of the electrode can be reliably restricted and the stacking deviation can be suppressed.
(4) By changing the extending direction of the bending line L1 of the bending part 30 provided in the positive electrode 19 and by changing the extending direction of the bending line L2 of the bending part 31 provided in the negative electrode 20, The movement of the electrodes in the vertical and horizontal directions can be restricted.

  (5) Moreover, since the bending parts 30 and 31 are provided in each of the four corners of the positive electrode 19 and the negative electrode 20, the movement of the electrodes can be restricted and the stacking deviation can be suppressed with a simple configuration. In addition, the step of laminating the positive electrode 19 and the negative electrode 20 is facilitated.

(Second Embodiment)
Hereinafter, a second embodiment will be described with reference to FIGS. Note that, in the embodiments described below, the same components as those in the embodiments described above are denoted by the same reference numerals, and redundant descriptions thereof are omitted or simplified.

  As shown in FIGS. 7 and 8, the surface of the positive electrode 19 of this embodiment is formed into a corrugated shape. That is, the positive electrode 19 has a plurality of arc-shaped bent portions 35 arranged in parallel in the horizontal direction Y1 shown in the drawing. Further, these bent portions 35 are all extended in the vertical direction Y2 shown in the drawing. In addition, the negative electrode 20 is provided with a plurality of bent portions 36, similarly to the positive electrode 19. Each bending part 35 and 36 is provided with the same curvature. Further, the bent portions 35 and 36 are provided on the electrode surface so that the bent portions 35 and the bent portions 36 do not intersect each other. The bent portions 35 and 36 are gently curved.

  Then, the electrode assembly 12 in which the required number of positive electrodes 19 and negative electrodes 20 are stacked is in a state in which a bent stacked portion H1 in which the bent portions 35 and 36 are overlapped in the stacking direction is provided. In the electrode assembly 12, the positive electrode 19 and the negative electrode 20 have a plurality of bent portions 35 and 36, whereby a plurality of bent laminated portions H1 are provided. In the electrode assembly 12, the plurality of bending laminated portions H1 are not overlapped with each other. Moreover, the extending direction of the bending parts 35 and 36 which comprise the one bending laminated part H1 differs from the extending direction of the bending parts 35 and 36 which comprise the other bending laminated part H1.

Hereinafter, the operation of the present embodiment will be described.
As shown in FIG. 8, when the positive electrode 19 and the negative electrode 20 are stacked, the bent portion 35 of the positive electrode 19 and the bent portion 36 of the negative electrode 20 overlap in the stacking direction. Therefore, for example, when the positive electrode 19 is stacked on the negative electrode 20, the positive electrode 19 has its bent portion 35 overlapped with the bent portion 36 of the negative electrode 20, so that movement of the electrode itself in the lateral direction is restricted. . For example, when the positive electrode 19 is about to move in the lateral direction Y <b> 1, the bent portion 35 of the positive electrode 19 is caught by the bent portion 36 of the negative electrode 20 that overlaps the bent portion 35. Accordingly, the movement of the positive electrode 19 in the lateral direction Y1 is restricted by the overlapping of the bent portions 35 and 36.

  On the other hand, when the electrode assembly 12 provided with the bending laminated portion H1 in which the bending portions 35 and 36 overlap in the laminating direction is inserted into the case 11, the electrode assembly 12 receives a load from the laminating direction of the electrode assembly 12 at the time of insertion. . For this reason, each bending part 35 and 36 which comprises the bending lamination | stacking part H1 returns to the direction opposite to a bending direction by the effect | action of the load received when the electrode assembly 12 is accommodated. Thereby, the bending state of each bending part 35 and 36 is relieved. That is, the bending portions 35 and 36 have a smaller curvature in the restrained state in which the electrode assembly 12 is accommodated in the case 11 than in the released state in which the electrode assembly 12 is moved out of the case 11. More specifically, the bending state of the arc-shaped bent portions 35 and 36 is relaxed, and the electrode surface returns to a flat surface.

  And in the electrode assembly 12 accommodated in the case 11, the stress which tries to return each bent part 35 and 36 which comprises the bending lamination | stacking part H1 to the bent state is acting. For this reason, the bending part 35 of the positive electrode 19 and the bending part 36 of the negative electrode 20 at the time of lamination | stacking are maintained. Therefore, even after the electrode assembly 12 is accommodated, for example, when the positive electrode 19 is about to move with respect to the negative electrode 20, the bent portion 35 of the positive electrode 19 is caught by the bent portion 36 of the negative electrode 20, and the movement is prevented. Be regulated. In addition, each bending part 35 and 36 is provided by press-molding simultaneously with stamping, when punching out the electrode 34 from the metal foil 32, as demonstrated in 1st Embodiment.

  Therefore, according to the present embodiment, the same effects as the effects (1) to (3) of the first embodiment are obtained. In the present embodiment, the effects (1) to (3) can be produced by providing the positive electrode 19 and the negative electrode 20 with the bent portions 35 and 36.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to FIGS. 9 and 10.
As shown in FIGS. 9 and 10, the positive electrode 19 of this embodiment is bent in directions opposite to each other in the stacking direction of the positive electrode 19 and the negative electrode 20 (bending direction X1 and bending direction X2 in the drawing). Two bent portions 37 and 38 are provided. Bending lines L3 and L4 serving as folds are located on the surface of the positive electrode 19 by the bent portions 37 and 38. The bent portions 37 and 38 are provided on the surface of the positive electrode 19 so that the bent portions 37 and 38 do not overlap each other. In the present embodiment, the bent portion 37 is a first bent portion that is bent in one of the stacking directions, and the bent portion 38 is a second bent portion that is bent in the other of the stacking directions.

  The bending portions 37 and 38 are provided so that the bending line L3 and the bending line L4 do not intersect on the surface of the positive electrode 19. And each bending line L3, L4 differs in the extending direction. For this reason, the bending lines L3 and L4 do not intersect on the surface of the positive electrode 19, but when they extend outside the surface of the positive electrode 19 as shown by a dashed line in the figure, they intersect outside the surface. . Further, the bending portions 37 and 38 are provided so that the bending lines L3 and L4 straddle two sides facing each other in the positive electrode 19. Each of the bent portions 37 and 38 is bent so as to be gently bent at a bending angle β. The bending angle β indicates the amount of bending when the positive electrode 19 is bent in the bending directions X1 and X2.

  Similarly to the positive electrode 19, the negative electrode 20 is provided with two bent portions 39 and 40 that are bent in opposite directions in the stacking direction of the positive electrode 19 and the negative electrode 20. A bend line serving as a crease is positioned on the surface of the negative electrode 20 by the bent portions 39 and 40. Similar to the bent portions 37 and 38 of the positive electrode 19, these bent portions 39 and 40 are provided so that the bent portions 39 and 40 do not overlap each other on the surface of the negative electrode 20. In the present embodiment, the bent portion 39 is a first bent portion that is bent in one of the stacking directions, and the bent portion 40 is a second bent portion that is bent in the other of the stacking directions. The bending portions 39 and 40 are provided so that the bending lines do not intersect on the surface of the negative electrode 20, and the bending directions of the bending lines are different. The bending portions 39 and 40 are provided so that the bending lines overlap the bending lines L3 and L4 of the bending portions 37 and 38 of the positive electrode 19 when the positive electrode 19 is laminated.

  In the electrode assembly 12 in which the required number of positive electrodes 19 and negative electrodes 20 are laminated, the bent portions 37 and 39 are overlapped with each other in the stacking direction because the bent portions 37 and 39 are overlapped. The first bent laminated portion H2. Moreover, the electrode assembly 12 has the 2nd bending laminated part H3 where the bending parts 38 and 40 used as a 2nd bending part overlap in the lamination direction because the bending parts 38 and 40 used as a 2nd bending part overlap. . In the electrode assembly 12, the first and second bent laminated portions H2 and H3 do not overlap each other. Moreover, the extending direction of the bending parts 37 and 39 which comprise the 1st bending laminated part H2 and the extending direction of the bending parts 38 and 40 which comprise the 2nd bending laminated part H3 differ.

Hereinafter, the operation of the present embodiment will be described.
As shown in FIG. 10, when the positive electrode 19 and the negative electrode 20 are stacked, the bent portions 37 and 38 of the positive electrode 19 and the bent portions 39 and 40 of the negative electrode 20 overlap in the stacking direction. Therefore, for example, when the positive electrode 19 is laminated on the negative electrode 20, the positive electrode 19 has its bent portions 37 and 38 overlapped with the bent portions 39 and 40 of the negative electrode 20, respectively. Movement is restricted. For example, when the positive electrode 19 attempts to move in the lateral direction Y1, the bent portion 37 of the positive electrode 19 is caught by the bent portion 39 of the negative electrode 20 overlapping the bent portion 37, while the bent portion 38 of the positive electrode 19 is Then, it is caught by the bent portion 40 of the negative electrode 20 overlapping the bent portion 38. Further, for example, when the positive electrode 19 is about to move in the longitudinal direction Y2, the bent portion 37 of the positive electrode 19 is caught by the bent portion 39 of the negative electrode 20 overlapping the bent portion 37, while the bent portion of the positive electrode 19 is 38 is caught by the bent portion 40 of the negative electrode 20 overlapping the bent portion 38. Accordingly, the movement of the positive electrode 19 in the horizontal direction Y1 and the vertical direction Y2 is restricted by the overlapping of the bent portions 37 and 38 and the bent portions 39 and 40 of the negative electrode 20.

  On the other hand, the electrode assembly 12 in a state where the first bent laminated portion H2 in which the bent portions 37 and 39 overlap in the stacking direction and the second bent stacked portion H3 in which the bent portions 38 and 40 overlap in the stacking direction are provided. When inserted into the case 11, a load is applied from the stacking direction of the electrode assembly 12 at the time of insertion. Therefore, the bending portions 37 and 39 constituting the first bending laminated portion H2 and the bending portions 38 and 40 constituting the second bending laminated portion H3 are bent in the bending direction by the action of the load received when the electrode assembly 12 is accommodated. It returns in the opposite direction to X1 and X2. Thereby, the bending state of each bending part 37-40 is relieve | moderated. In other words, each of the bent portions 37 to 40 has a smaller bending angle β in a restrained state where the electrode assembly 12 is accommodated in the case 11 than in a released state where the electrode assembly 12 is moved out of the case 11. Specifically, the bending angle β returns to a state close to “0 degree”. The state where the bending angle is “0 degree” means that the bending portions 37 to 40 return to a state where they form an unbent electrode surface and a flat surface.

  And in the electrode assembly 12 accommodated in the case 11, the stress which is going to return to the state by which each bending part 37-40 which comprises the 1st bending laminated part H2 and the 2nd bending laminated part H3 was bent. is working. For this reason, the state where the bent portions 37 and 38 of the positive electrode 19 and the bent portions 39 and 40 of the negative electrode 20 overlap each other during the lamination is maintained. Therefore, even after the electrode assembly 12 is accommodated, for example, when the positive electrode 19 is about to move with respect to the negative electrode 20, the bent portions 37 and 38 of the positive electrode 19 become bent portions 39 and 40 of the negative electrode 20. Catch and movement are restricted. In addition, each bending part 37-40 is provided by press-molding simultaneously with punching, when punching out the electrode 34 from the metal foil 32, as demonstrated in 1st Embodiment.

  Therefore, according to this embodiment, in addition to the effects (1) to (4) of the first embodiment, the following effects can be obtained. In the present embodiment, the effects (1) to (4) can be obtained by providing the positive electrode 19 and the negative electrode 20 with the bent portions 37 to 40.

  (6) By providing the bending portions 37 to 40 that are bent in the direction opposite to the stacking direction, the movement of the electrodes can be restricted and the stacking deviation can be suppressed with a simple configuration. In addition, the step of laminating the positive electrode 19 and the negative electrode 20 is facilitated.

In addition, you may change the said embodiment as follows.
As shown in FIG. 11, when the sizes of the positive electrode 19 and the negative electrode 20 are different, the bent portions 30 and 31 are provided in the positive electrode 19 and the negative electrode 20, respectively, as described below. That is, when the positive electrode 19 and the negative electrode 20 are stacked, the bending line L2 that becomes the fold of the bending portion 31 of the negative electrode 20 and the bending line L1 that becomes the fold of the bending portion 30 of the positive electrode 19 overlap in the stacking direction. Bending portions 30 and 31 are provided. In this case, as shown in FIG. 11, the area of the bent portion 30 of the positive electrode 19 and the area of the bent portion 31 of the negative electrode 20 are different.

O The bending angle of each bending part 30,31,37-40 and the curvature of the bending parts 35 and 36 can be changed suitably.
O Each bending part 30, 31, 35-40 may be provided in a separate process after punching out the electrodes.

  O About the separator 21 interposed between the positive electrode 19 and the negative electrode 20, the bending parts 30, 31, 35-40 may be provided, and it is not necessary to provide. More specifically, depending on the material of the separator 21 and the pressure at which the electrode assembly 12 is restrained, there may be a case where a bent portion is formed on the separator 21 and a case where a bent portion is not formed. Also, when the bent state is returned from the constrained state, the bent portion is relaxed, but there may be both a case where the bent portion is formed and a case where the bent portion is completely extinguished.

The positive electrode 19 and the negative electrode 20 may be rectangular or square.
(Circle) the secondary battery 10 may be mounted in a motor vehicle as a vehicle, and may be mounted in an industrial vehicle. Further, the present invention may be applied to a stationary power storage device.

The configuration of the present embodiment may be applied to other power storage devices such as electric double layer capacitors.
The secondary battery 10 is not limited to a lithium ion secondary battery, and may be another secondary battery. 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.

When the electrode assembly 12 is accommodated in the case 11, the bent portions 30, 31, 35 to 40 may be returned to a flat state by pressing the electrode assembly 12 or the like.
In the second embodiment, a part of the electrode surface may be formed into a corrugated shape, and the bent portions 35 and 36 may be provided in a part thereof. Further, the bent portions 35 and 36 may be juxtaposed in the vertical direction Y2. Moreover, you may mix the bending parts 35 and 36 juxtaposed in the horizontal direction Y1, and the bending parts 35 and 36 juxtaposed in the vertical direction Y2. By doing so, the movement of the electrodes in the vertical and horizontal directions can be restricted.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 12 ... Electrode assembly, 19 ... Positive electrode, 20 ... Negative electrode, 21 ... Separator, 30, 31, 35-40 ... Bending part, L1-L4 ... Bending line, (alpha), β: bending angle, H1: bending laminated portion, H2: first bending laminated portion, H3: second bending laminated portion.

Claims (6)

In a power storage device comprising: an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, and a case housing the electrode assembly;
The positive electrode and the negative electrode each have a bent portion bent in the stacking direction of the electrode assembly on each surface;
The electrode assembly has a bent laminated portion in which the bent portions overlap each other in the lamination direction of the electrode assembly,
Each of the bent portions has a smaller curvature or bending angle in a restrained state in which the electrode assembly is accommodated in the case as compared with a released state in which the electrode assembly is taken out of the case. Power storage device.   The power storage device according to claim 1, wherein the electrode assembly includes a plurality of the bent laminated portions, and the bent laminated portions do not overlap each other.   The power storage device according to claim 2, wherein an extending direction of the bent portion constituting one bent laminated portion is different from an extending direction of the bent portion constituting another bent laminated portion.   4. The power storage device according to claim 3, wherein the bent portion passes through two adjacent sides of the positive electrode and the negative electrode and has at least four. 5. The bent portion includes a first bent portion bent in one of the stacking directions and a second bent portion bent in the other of the stacking directions,
The said bending lamination | stacking part contains the 1st bending lamination | stacking part comprised by said 1st bending parts, and the 2nd bending lamination | stacking part comprised by said 2nd bending parts. Power storage device.   The power storage device according to any one of claims 1 to 5, wherein the power storage device is a secondary battery.