JP2020038803A - Power storage device and manufacturing method thereof - Google Patents

Abstract

To increase battery capacity.SOLUTION: An insulating sheet 40 that insulates an electrode assembly from a case has a first insulating portion 41, a pair of second insulating portions 42, and a pair of third insulating portions. The third insulating portion has a first part 44 and a pair of second parts 45 located across the first part 44. In the second part 45, a line extending obliquely from an intersection P1 of a boundary line L1 between the second insulating portion 42 and the second part 45 and a boundary line L2 between the first part 44 and the second part 45 is set as a virtual line L3. The second part 45 has a cutout 46 in a portion surrounded by the boundary line L2, the virtual line L3, and the edge 40f of the insulating sheet 40. The assembled insulating sheet 40 has an overlapping portion in which first surplus portions 50 of the second part 45 overlap each other. The first part 44 overlaps the second part 45. A second surplus portion 51 of the second part 45 is developed without overlapping other parts of the second part 45.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power storage device and a method for manufacturing the power storage device.

  2. Description of the Related Art A vehicle such as an EV (Electric Vehicle) and a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery as a power storage device that stores power supplied to a traveling motor. The secondary battery includes, for example, an electrode assembly having a layered structure including a plurality of electrodes, and a case for housing the electrode assembly. In some cases, an insulating sheet is provided between each end face of the electrode assembly and the case to insulate the electrode assembly from the case.

  For example, an insulating sheet provided in a secondary battery described in Patent Document 1 has a first insulating portion, a pair of second insulating portions, and a pair of third insulating portions. The first insulating portion is disposed between the first end surface of the electrode assembly and the case. The pair of second insulating portions are arranged between the pair of second end surfaces connected to the first end surface of the electrode assembly and the case. The pair of third insulating portions are disposed between the case and the pair of third end surfaces connected to the first and second end surfaces of the electrode assembly. Further, the pair of third insulating portions extend from the edge of the first insulating portion and the first part extending from the edge of the pair of second insulating portions and are located across the first part. And a pair of second parts. Then, in a state where the insulating sheet is assembled, the insulating sheet has an overlapping portion in which the pair of second parts overlap each other, and the first part overlaps the second part. In the insulating sheet, at the portion where the overlapping portion and the first part overlap, the insulating sheet has a maximum of five layers.

JP 2015-228359 A

  Incidentally, the size of the gap between the case and the electrode assembly is set in consideration of the maximum overlap of the insulating sheets. However, in order to increase the battery capacity of the secondary battery, it is desirable to increase the space for disposing the electrode assembly in the case. In that regard, there is room for improvement in the secondary battery described in Patent Document 1 in that respect. there were.

  An object of the present invention is to provide a power storage device capable of increasing battery capacity and a method for manufacturing the power storage device.

  A power storage device that solves the above problem includes a power storage device including: an electrode assembly having a layered structure including a plurality of electrodes; a case that houses the electrode assembly; and an insulating sheet that insulates the electrode assembly from the case. The device, wherein the insulating sheet comprises: a first insulating portion disposed between a first end surface of the electrode assembly and the case; and a pair of second end surfaces connected to the first end surface of the electrode assembly. A pair of second insulating portions disposed between the case and a pair of third end surfaces connected to the first end surface and the second end surface of the electrode assembly; In a state in which the insulating sheet is unfolded, the pair of second insulating portions extend from a pair of opposing first edges of the edges of the first insulating portion. A third pair of the third A third part extending from a second edge perpendicular to the pair of first edges of the edge of the first insulating part; And a pair of second parts extending from a third edge orthogonal to the pair of first edges among the edges of the second insulating part, and positioned with the first part interposed therebetween. The second part extends from an intersection of a boundary between the second insulating part and the second part and a boundary between the first part and the second part, and the second insulating part and the second part. When setting an imaginary line extending obliquely with respect to a boundary line with the second part, the second part of one of the pair of second parts is a boundary line between the first part and the second part. , The imaginary line and a fourth edge which is an edge of the insulating sheet facing the third edge. A cut portion formed by cutting the second part over the fourth edge and the imaginary line in the cut portion, wherein the insulating sheet includes the first edge, the second edge, and the third edge. In a state in which the insulating sheet is assembled by being bent along an edge, the insulating sheet is a part of the pair of second parts, the third edge, the virtual line, and the insulating member. A portion surrounded by an edge of the sheet has an overlapping portion where the first part overlaps a second part, and in the second part of one of a pair of the second parts, A portion surrounded by the imaginary line, the cut portion, and the fourth edge is developed without overlapping another portion of one of the second parts.

  A method for manufacturing a power storage device that solves the above problem includes an electrode assembly having a layered structure including a plurality of electrodes, a case that houses the electrode assembly, an insulating sheet that insulates the electrode assembly from the case, A method for manufacturing a power storage device comprising: a first insulating portion that can be disposed between a first end surface of the electrode assembly and the case; and the first insulating surface connected to the first end surface of the electrode assembly. A pair of second insulating portions that can be disposed between the pair of second end surfaces and the case, and a pair of the third end surfaces connected to the first and second end surfaces of the electrode assembly and the case; A pair of third insulating portions that can be arranged in a pair, and in a state where the insulating sheet is unfolded, the pair of second insulating portions are a pair of third insulating portions facing each other among the edges of the first insulating portion. From one edge The third insulating portion of one of the pair of third insulating portions extends from a second edge portion of the edge portions of the first insulating portion which is orthogonal to the pair of first edge portions. A first part to be provided, extending from a third edge orthogonal to the pair of first edges among the edges of the pair of second insulating parts, and positioned with the first part interposed therebetween; A pair of second parts, wherein the second parts extend from an intersection of a boundary between the second insulating part and the second part and a boundary between the first part and the second part. In addition, when setting an imaginary line extending obliquely to a boundary line between the second insulating portion and the second part, the second part is one of the pair of second parts, and the second part is the second part. A boundary line between one part and the second part, the imaginary line, and the gap facing the third edge; At a portion surrounded by a fourth edge, which is an edge of the sheet, a cut portion is formed by cutting the second part over the fourth edge and the imaginary line, and the insulating sheet is attached to the first edge. And bending the portion along the third edge so that, of the pair of second parts, portions surrounded by the third edge, the imaginary line, and the edge of the insulating sheet overlap each other to form an overlapping portion. Is formed, and the insulating sheet is folded along the second edge, so that the first part is overlapped with the second part, and in the second part of one of the pair of second parts, The insulating sheet is assembled such that a portion surrounded by the imaginary line, the cut portion, and the fourth edge is developed without overlapping with another portion of one of the second parts. .

  According to each of the above-described configurations, the second part is divided by the cut portion, so that the portion that was conventionally folded and overlapped with the overlapping portion is folded. First, the insulating sheet is unfolded on the second edge side of the first insulating portion. Since it can be bent, the number of overlapping insulating sheets can be reduced. In one second part of the pair of second parts, a part other than the overlapping part in the second part does not overlap with the overlapping part. Therefore, in the third insulating portion including the second part having the cutout, the insulating sheets overlap at a maximum of four layers. Therefore, the gap between the case and the electrode assembly can be set small as much as the maximum overlap of the insulating sheets is reduced, so that the battery capacity of the power storage device can be increased.

In the power storage device, it is preferable that both of the pair of second parts have the cut portion.
According to the above configuration, in both of the pair of second parts, portions other than the overlapping part of the second part do not overlap with the overlapping part. Therefore, in the third insulating portion including the second part having the cut portion, the insulating sheets overlap at a maximum of three layers. Therefore, the maximum overlap of the insulating sheets can be reduced, so that the battery capacity of the power storage device can be further increased.

  Regarding the power storage device, both of the pair of third insulating parts have the first part and the pair of second parts, and in each of the pair of third insulating parts, both of the pair of second parts are the same. It is preferable to have a notch.

  According to the above configuration, in the pair of second parts in both the pair of third insulating parts, portions other than the overlapping part in the second part do not overlap with the overlapping part. Therefore, in both of the pair of third insulating portions, the overlapping of the insulating sheets becomes a maximum of three layers. Therefore, the maximum overlap of the insulating sheets can be reduced, so that the battery capacity of the power storage device can be further increased.

It is preferable that the power storage device has a welded portion where the first part is welded to a portion of the second part where the first part overlaps.
As a method of fixing the assembled insulating sheet, for example, there is a method of attaching a folded insulating sheet with an adhesive tape. In such a case, it is necessary to set the gap between the case and the electrode assembly in consideration of the thickness of the adhesive tape in addition to the maximum overlap of the insulating sheets. According to the above configuration, since the insulating sheet is fixed by welding, it is not necessary to consider the thickness of the adhesive tape in the gap between the case and the electrode assembly, and the battery capacity of the power storage device can be increased accordingly.

  According to the present invention, the battery capacity can be increased.

FIG. 2 is an exploded perspective view of the secondary battery in the embodiment. FIG. 3 is a perspective view of a secondary battery. FIG. 3 is an exploded perspective view of the electrode assembly. FIG. 4 is a front view and a partially enlarged view showing a developed shape of the insulating sheet. FIG. 4 is a perspective view showing a bending mode of the insulating sheet. The front view which shows partially the 3rd insulating part in the insulating sheet of the assembled state. The figure which shows typically the shape of the cut part in other embodiment. The figure which shows typically the shape of the cut part in other embodiment.

Hereinafter, an embodiment in which a power storage device is embodied as a secondary battery will be described with reference to FIGS. 1 to 6.
As shown in FIGS. 1 and 2, a secondary battery 10 as a power storage device includes a rectangular box-shaped case 11 and an electrode assembly 30 housed in the case 11. The case 11 has a rectangular parallelepiped case body 20 and a rectangular flat lid 25 for closing the opening 20a of the case body 20. The case body 20 includes a rectangular plate-shaped bottom wall 21, a long side wall 22 erected from a pair of long side edges of the bottom wall 21, and a short side wall erected from a pair of short side edges of the bottom wall 21. And a side wall 23. The case main body 20 and the lid 25 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a prismatic battery having a rectangular appearance. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

  As shown in FIG. 3, the electrode assembly 30 includes a plurality of positive electrodes 31, negative electrodes 35, and separators 39. The electrode assembly 30 has a layered structure in which a separator 39 is interposed between the positive electrode 31 and the negative electrode 35, and the layers are stacked in a mutually insulated state. The direction in which the positive electrode 31 and the negative electrode 35 are stacked is referred to as a stacking direction X.

  The positive electrode 31 has a rectangular sheet-shaped positive metal foil (for example, aluminum foil) 32 and positive electrode active material layers 33 present on both surfaces of the positive metal foil 32. The positive electrode 31 includes a first edge 31a at one edge of the pair of edges along the long side, and includes a second edge 31b at the other edge opposite to the first edge 31a. . Further, the positive electrode 31 includes a third edge 31c at an edge along a pair of short sides connecting the first edge 31a and the second edge 31b. The positive electrode 31 has a rectangular positive tab 34 protruding from a part of the second edge 31b. The positive electrode tab 34 does not have the positive electrode active material layer 33 and is formed of the positive electrode metal foil 32 itself.

  The negative electrode 35 has a rectangular sheet-shaped negative electrode metal foil (for example, copper foil) 36 and negative electrode active material layers 37 present on both surfaces of the negative electrode metal foil 36. The negative electrode 35 includes a first edge 35a at one edge of the pair of edges along the long side, and includes a second edge 35b at the other edge opposite to the first edge 35a. . Further, the negative electrode 35 has a third edge 35c at an edge along a pair of short sides connecting the first edge 35a and the second edge 35b. The negative electrode 35 has a rectangular negative electrode tab 38 protruding from a part of the second edge 35b. The negative electrode tab 38 does not have the negative electrode active material layer 37 and is formed of the negative electrode metal foil 36 itself.

  The separator 39 is made of a rectangular sheet-shaped insulating material. The separator 39 insulates the positive electrode 31 and the negative electrode 35. The separator 39 includes a first edge 39a at one edge of a pair of long edges, and a second edge 39b at the other edge opposite to the first edge 39a. Further, the separator 39 includes a third edge 39c at an edge along a pair of short sides connecting the first edge 39a and the second edge 39b.

  The length of the first edge 35 a of the negative electrode 35 is longer than the length of the first edge 31 a of the positive electrode 31, and the length of the second edge 35 b of the negative electrode 35 is the second edge of the positive electrode 31. It is longer than the length of 31b. The length of the third edge 35c of the negative electrode 35 is longer than the length of the third edge 31c of the positive electrode 31. That is, the outer shape of the negative electrode 35 is slightly larger than the outer shape of the positive electrode 31. The length of the first edge 39 a of the separator 39 is equal to the length of the first edge 35 a of the negative electrode 35, and the length of the second edge 39 b of the separator 39 is the second edge of the negative electrode 35. It is equal to the length of 35b. The length of the third edge 39c of the separator 39 is equal to the length of the third edge 35c of the negative electrode 35. That is, the outer shape of the separator 39 is slightly larger than the outer shape of the positive electrode 31 and is equal to the outer shape of the negative electrode 35.

  As shown in FIG. 1, the respective positive electrode electrodes 31 are stacked such that the respective positive electrode tabs 34 are arranged in a row along the stacking direction X. Similarly, the respective negative electrode electrodes 35 are stacked such that the respective negative electrode tabs 38 are arranged in a row along the stacking direction X at positions not overlapping with the positive electrode tabs 34. The electrode assembly 30 includes a positive electrode tab group 34a in which each positive electrode tab 34 is stacked, and a negative electrode tab group 38a in which each negative electrode tab 38 is stacked.

  The electrode assembly 30 includes a tab-side end face 30t on the end face where the positive electrode tab group 34a and the negative electrode tab group 38a exist. The tab-side end surface 30t is configured by stacking a second edge 35b of the negative electrode 35 and a second edge 39b of the separator 39. Further, the electrode assembly 30 includes a first end surface 30a on an end surface opposite to the tab-side end surface 30t. The first end face 30a is configured by stacking a first edge 35a of the negative electrode 35 and a first edge 39a of the separator 39. The electrode assembly 30 includes a pair of second end surfaces 30b on the end surfaces in the stacking direction X. The second end face 30b is composed of electrodes located at both ends of the electrode assembly 30 in the stacking direction X, such as the negative electrode 35. Further, the electrode assembly 30 includes a pair of third end surfaces 30c on an end surface orthogonal to the first end surface 30a, the second end surface 30b, and the tub-side end surface 30t. The third end face 30c is connected to the first end face 30a, the second end face 30b, and the tab-side end face 30t, and is formed by stacking a third edge 35c of the negative electrode 35 and a third edge 39c of the separator 39. Have been. The direction in which the first end face 30a and the tab-side end face 30t make a pair is defined as the height direction Z, and the direction orthogonal to the stacking direction X and the height direction Z is defined as the width direction Y.

  The secondary battery 10 includes a positive terminal 26 and a negative terminal 27 for extracting electricity from the electrode assembly 30. The positive electrode terminal 26 and the negative electrode terminal 27 protrude outside the case 11 through the through hole 25h of the lid 25. Ring-shaped insulating rings 28 for insulating the lid 25 are attached to the positive electrode terminal 26 and the negative electrode terminal 27, respectively. The positive electrode tab group 34a is electrically connected to the positive electrode terminal 26, and the negative electrode tab group 38a is electrically connected to the negative electrode terminal 27.

  The secondary battery 10 includes an insulating sheet 40 that insulates the electrode assembly 30 from the case 11. The insulating sheet 40 is an insulating material and is made of, for example, polyethylene (PE), polypropylene (PP), polyphenylene sulfide (PPS), or the like. Further, the insulating sheet 40 covers five surfaces except the tab-side end surface 30t of the electrode assembly 30, that is, the first end surface 30a, the second end surface 30b, and the third end surface 30c.

  The insulating sheet 40 has a first insulating portion 41, a pair of second insulating portions 42, and a pair of third insulating portions 43. The first insulating part 41 is disposed between the first end face 30 a of the electrode assembly 30 and the bottom wall 21 of the case body 20. Thereby, the first end face 30a of the electrode assembly 30 and the bottom wall 21 of the case main body 20 are insulated. The pair of second insulating portions 42 is disposed between the pair of second end surfaces 30 b of the electrode assembly 30 and the long side wall 22 of the case body 20. Thereby, the second end face 30b of the electrode assembly 30 and the long side wall 22 of the case body 20 are insulated. The pair of third insulating portions 43 is disposed between the pair of third end surfaces 30 c of the electrode assembly 30 and the short side wall 23 of the case body 20. Thereby, the third end face 30c of the electrode assembly 30 and the short side wall 23 of the case body 20 are insulated.

  FIG. 4 is an exploded view showing the insulating sheet 40 in a state before being folded and covering the electrode assembly 30. For convenience of description, the upper, lower, left, and right in FIG. 4 are simply referred to as upper, lower, left, and right, respectively, below. As shown in FIG. 4, the first insulating part 41 has a rectangular shape, and the length in the left-right direction of the first insulating part 41 is substantially equal to the length in the width direction Y of the electrode assembly 30. The length of the first insulating portion 41 in the up-down direction is substantially equal to the length of the electrode assembly 30 in the stacking direction X. For this reason, the size of the first insulating portion 41 is substantially equal to the size of the first end face 30 a of the electrode assembly 30. In addition, as shown in FIG. 1, the length in the width direction Y of the electrode assembly 30 is a length between one third end surface 30c and the other third end surface 30c of the electrode assembly 30. The length of the electrode assembly 30 in the stacking direction X is the length between one second end surface 30b and the other second end surface 30b of the electrode assembly 30.

  As shown in FIG. 4, the pair of second insulating portions 42 are rectangular and extend from the pair of long edge portions 41 a of the first insulating portion 41. The pair of second insulating portions 42 are located vertically above and below the first insulating portion 41. The length of the pair of second insulating portions 42 in the left-right direction is substantially the same as the length of the electrode assembly 30 in the width direction Y, similarly to the length of the first insulating portions 41 in the left-right direction. The length in the vertical direction of the pair of second insulating portions 42 is substantially the same as the length in the height direction Z of the electrode assembly 30. For this reason, the size of the pair of second insulating portions 42 is substantially the same as the size of the second end surface 30 b of the electrode assembly 30. As shown in FIG. 1, the length of the electrode assembly 30 in the height direction Z is a length between the first end surface 30a and the tab-side end surface 30t of the electrode assembly 30.

  The pair of third insulating portions 43 has a rectangular shape, and is located with the first insulating portion 41 and the second insulating portion 42 interposed therebetween. In addition, both of the pair of third insulating portions 43 include a rectangular first part 44 and a pair of second parts 45. As shown in FIG. 4, the first part 44 extends from a pair of short edges 41 b orthogonal to a pair of long edges 41 a in the first insulating portion 41. One first part 44 extends from the short edge 41b on the right side of the first insulating portion 41, and the other first part 44 extends from the short edge 41b on the left side of the first insulating portion 41. Have been. The pair of second parts 45 are edges located on the short sides of the pair of second insulating portions 42, and extend from the short edges 42 a of the first insulating portion 41 that are orthogonal to the pair of long edges 41 a. ing. A pair of second parts 45 forming one third insulating portion 43 extend from the short edge portion 42 a on the right side of the second insulating portion 42, and a pair of second parts 45 forming the other third insulating portion 43. Two parts 45 extend from the short edge portion 42 a on the left side of the second insulating portion 42. Further, in each of the third insulating portions 43, the second part 45 located above the first part 44 of the pair of second parts 45 is formed of the first insulating portion 41 of the pair of second insulating portions 42. It extends from the short edge 42a of the second insulating portion 42 located on the upper side. The second part 45 located below the first part 44 of the pair of second parts 45 is the second insulating part located below the first insulating part 41 of the pair of second insulating parts 42. 42 extend from the short edge 42a. In the present embodiment, the long edge 41a corresponds to a first edge, the short edge 41b corresponds to a second edge, and the short edge 42a corresponds to a third edge.

  The vertical length of the first part 44 is the same as the length of the electrode assembly 30 in the stacking direction X, as in the vertical direction of the first insulating part 41. It is about. The length in the vertical direction of the pair of second parts 45 is substantially the same as the length in the height direction Z of the electrode assembly 30, similarly to the length in the vertical direction of the second insulating portion 42. The length of the pair of second parts 45 in the left-right direction is longer than half the length of the electrode assembly 30 in the stacking direction X and shorter than the length of the electrode assembly 30 in the stacking direction X. .

  In the insulating sheet 40, the pair of short edges 42a of the second insulating portion 42 are located at the boundary between the second insulating portion 42 and the second part 45. A straight line extending on the pair of short edges 42a in the second insulating portion 42 is a boundary line L1 between the second insulating portion 42 and the second part 45. The boundary lines L1 extend from the four corners of the first insulating portion 41 to a pair of edges 40e extending left and right among the edges of the insulating sheet 40. In the insulating sheet 40, of the pair of second insulating portions 42, two boundary lines L <b> 1 extending on the pair of short edges 42 a of the upper second insulating portion 42, and the lower second insulating portion 42. A total of four boundary lines L1 including two boundary lines L1 extending on the pair of short edge portions 42a in the portion 42 are located.

  A straight line extending in the direction in which the long edge portion 41a extends from the four corners of the first insulating portion 41 to a pair of edge portions 40f extending vertically among the edge portions of the insulating sheet 40 is formed by the first part 44 and the second part. A boundary line L2 with the part 45 is formed. In the insulating sheet 40, of the pair of long edges 41a of the first insulating portion 41, two boundary lines L2 extending left and right in a direction in which the upper edge 41a extends, and a long edge located below. A total of four boundary lines L2, which are two boundary lines L2 extending left and right in the direction in which the portion 41a extends, are located.

  Here, in the second part 45, while extending from the four corners of the first insulating portion 41, which is the intersection P1 between the boundary line L1 and the boundary line L2, the second part 45 is inclined at 45 ° to the boundary line L1 and the boundary line L2. Is assumed to be a virtual line L3. The imaginary lines L3 are lines extending from the four corners of the first insulating portion 41 to the edge 40f of the insulating sheet 40. Then, the second part 45 cuts the second part 45 into a portion surrounded by the boundary line L2, the virtual line L3, and the edge 40f of the insulating sheet 40 facing the short edge 42a of the second insulating portion 42. It has a notch 46. The cuts 46 are formed in all four second parts 45 in the insulating sheet 40.

  The notch 46 extends over the edge 40f of the insulating sheet 40 and the virtual line L3 in the second part 45. The notch 46 extends left and right in the direction in which the boundary line L2 extends. The notch 46 is located closer to the boundary line L2 than the intermediate position between the position where the edge 40f of the insulating sheet 40 intersects the virtual line L3 and the position of the boundary line L2 in the vertical direction of the insulating sheet 40. It is in. The end 46a of the cut 46 is located on the virtual line L3. The end 46a of the notch 46 has an angular shape. The edge 40f of the insulating sheet 40 corresponds to a fourth edge. Further, the distance between the cut portion 46 and the boundary line L2 is defined as a length W1, the length of the pair of second parts 45 in the left-right direction is defined as a length W2, and the length of the first parts 44 in the vertical direction is defined as a length W3. , The lengths W1, W2, and W3 satisfy the relationship shown in the following Expression 1.

W1 <W3-W2 Equation 1
Next, the method of assembling the insulating sheet 40 will be described together with the operation of the secondary battery 10 and the method of manufacturing the secondary battery 10.

  As shown in FIG. 1 or FIG. 4, the insulating sheet 40 is attached to the electrode assembly 30 so as to wrap from the first end face 30 a side of the electrode assembly 30. Specifically, first, the insulating sheet 40 is attached so that the first insulating portion 41 of the insulating sheet 40 and the first end face 30a of the electrode assembly 30 overlap. Then, the insulating sheet 40 is bent along the pair of long edge portions 41a of the first insulating portion 41. As a result, the second end faces 30 b on both sides of the electrode assembly 30 in the stacking direction X are covered by the respective second insulating portions 42 of the insulating sheet 40.

  Further, the insulating sheet 40 is bent along the short edge portions 42a of the pair of second insulating portions 42. At this time, of the pair of second parts 45, a portion surrounded by the short edge portion 42a of the second insulating portion 42, the imaginary line L3, and the edge portion 40e and the edge portion 40f of the insulating sheet 40. One surplus portion 50 (see FIG. 4) overlaps in the width direction Y of the electrode assembly 30. Further, among the pair of second parts 45, the second surplus portions 51 (see FIG. 4), which are portions surrounded by the cut portions 46, the imaginary lines L <b> 3, and the edge portions 40 f of the insulating sheet 40, are connected to each other by electrodes. The assemblies 30 overlap in the width direction Y. At both ends in the width direction Y of the electrode assembly 30, a part of the first surplus part 50 overlaps with each other, and a part of the second surplus part 51 overlaps with each other. A portion where the first surplus portions 50 overlap each other is referred to as an overlap portion 52 (illustrated in FIG. 1 by being surrounded by a chain line). Further, the second surplus portion 51 is not folded and remains deployed on the short edge portion 41b side of the first insulating portion 41. Therefore, in each second part 45, the second surplus portion 51 does not overlap with other portions such as a portion of the first surplus portion 50 forming the overlap portion 52.

  Then, as shown in FIGS. 4 and 5, the insulating sheet 40 is bent along the short edge portion 41 b of the first insulating portion 41. At this time, the first part 44 overlaps the second part 45 at both ends in the width direction Y of the electrode assembly 30. Further, in the second part 45, the boundary portion L2, the imaginary line L3, the cut portion 46, and the third surplus portion 53 (see FIG. 4) which is a portion surrounded by the edge portion 40f of the insulating sheet 40 are formed by the electrode assembly 30 overlap with both ends of the first part 44 in the stacking direction X. As shown in FIG. 6, in a state where the insulating sheet 40 is assembled, the third surplus portion 53 is located closer to the second insulating portion 42 than the overlapping portion 52. That is, the third surplus portion 53 does not overlap the overlapping portion 52 in the width direction Y of the electrode assembly 30 (the direction perpendicular to the paper surface in FIG. 6).

  As shown in FIG. 6, in the assembled insulating sheet 40, the length of the third surplus portion 53 in the stacking direction X is the above-described length W1, and each first surplus portion 50 in the stacking direction X. Is the length W2, and the length of the third insulating portion 43 in the stacking direction X is the length W3. Then, “W3-W2” in Equation 1 above corresponds to the length in the stacking direction X of a portion of the first surplus portion 50 adjacent to the overlapping portion 52 in the stacking direction X in the third insulating portion 43. When each of the lengths W1, W2, and W3 satisfies the relationship shown in the above equation 1, the length of the first surplus portion 50 adjacent to the overlapping portion 52 in the stacking direction X is compared with the length in the stacking direction X. Also, the length of the third surplus portion 53 is reduced. That is, the third surplus portion 53 overlaps the overlapping portion 52 in the stacking direction X and the portion of the first surplus portion 50 adjacent thereto, but does not overlap the overlapping portion 52.

  By assembling the insulating sheet 40 in this manner, the insulating sheet 40 has a maximum of three layers at both ends in the width direction Y of the electrode assembly 30. Specifically, the three layers include a portion where the overlapping portion 52 overlaps the first part 44, a portion other than the overlapping portion 52 in the first excess portion 50, and the third excess portion 53 and the first part 44. This is the amount of overlap at the overlapped part. By locating the first part 44 and the second part 45 in this manner, the third end surfaces 30 c on both sides in the width direction Y of the electrode assembly 30 are covered with the third insulating portion 43.

  The size of the gap between the case 11 and the electrode assembly 30 is set in advance in consideration of the maximum overlap of the insulating sheet 40 described above. In the present embodiment, since the maximum overlap is three layers, the gap between the third end face 30c of the electrode assembly 30 and the short side wall 23 of the case body 20 is determined in consideration of the thickness of the three layers of the insulating sheet 40. Is set.

  After the insulating sheet 40 is assembled, a portion of the second part 45 where the first part 44 overlaps and the first part 44 are fixed by welding at both ends in the width direction Y of the electrode assembly 30. . Thereby, as shown in FIG. 1, a welded portion 55 is formed on the surface of the first part 44.

In the above embodiment, the following effects can be obtained.
(1-1) By dividing the second part 45 by the cutout portion 46, the second surplus portion 51, which has been conventionally folded and overlapped with the overlapping portion 52, is folded. First, the short edge portion 41 b of the first insulating portion 41. By leaving the sheet unfolded on the side, the number of overlapping insulating sheets 40 can be reduced. In the second part 45, portions other than the overlapping part 52 in the second part 45 do not overlap with the overlapping part 52. Therefore, the gap between the third end face 30c of the electrode assembly 30 and the short side wall 23 of the case body 20 can be set to be small as the maximum overlap of the insulating sheet 40 is reduced. Therefore, the battery capacity of the secondary battery 10 can be increased by increasing the size of the positive electrode 31 and the size of the negative electrode 35 by that much.

  (1-2) In both of the pair of second parts 45, portions other than the overlapping part 52 of the second part 45 do not overlap with the overlapping part 52. Therefore, in the third insulating portion 43, the insulating sheet 40 has a maximum of three layers. Therefore, as compared with the case where only one of the pair of second parts 45 includes the cut portion 46, the maximum overlap of the insulating sheet 40 can be reduced, and the battery capacity of the secondary battery 10 can be further increased.

  (1-3) In the pair of second parts 45 in both of the pair of third insulating parts 43, portions other than the overlapping part 52 of the second part 45 do not overlap with the overlapping part 52. Therefore, in each of the pair of third insulating portions 43, the insulating sheets 40 overlap at a maximum of three layers. Therefore, as compared with the case where one second part 45 of the pair of third insulating portions 43 includes the cutout portion 46, the maximum overlap of the insulating sheet 40 can be further reduced, so that the battery capacity of the secondary battery 10 can be reduced. Can be further increased.

  (1-4) As a method of fixing the assembled insulating sheet 40, for example, a method of attaching the folded insulating sheet 40 with an adhesive tape can be used. In such a case, it is necessary to set the gap between the case 11 and the electrode assembly 30 in consideration of the thickness of the adhesive tape in addition to the maximum overlap of the insulating sheets 40. According to the above embodiment, since the insulating sheet 40 is fixed by welding, it is not necessary to consider the thickness of the adhesive tape in the gap between the third end face 30c of the electrode assembly 30 and the short side wall 23 of the case body 20. Accordingly, the battery capacity of the secondary battery 10 can be increased by that amount.

  The above embodiment can be implemented with the following modifications. The above embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

  The shape of the end 46a of the cut 46 may be changed. For example, as shown in FIG. 7, the end 146a of the cutout 146 may have a curved shape. In addition, as shown in FIG. 8, the end 246a of the cut portion 246 may be formed in a circular shape. In the secondary battery 10, there is a possibility that a force may be applied to the insulating sheet 40 such that the cut portion expands due to expansion and contraction of the electrode assembly 30 during use. When there is a corner in the cut portion, stress tends to concentrate on the corner portion, and the cut is likely to advance to the corner. In this modified example, even under such a situation that a force is applied to spread the cut portions 146 and 246, the cut does not easily advance beyond the end portions 146a and 246a.

  In the insulating sheet 40, the formation range of the cut portion 46 is made larger than in the above embodiment, and the end 46a of the cut portion 46 is located between the virtual line L3 and the short edge portion 42a of the second insulating portion 42. You may do so. Also in this embodiment, if the end 46a of the cutout 46 is located closer to the imaginary line L3 than the short edge 42a of the second insulating portion 42 in the left-right direction in FIG. Can be obtained.

  The direction in which the notch 46 extends does not have to be the direction in which the boundary line L2 extends. For example, the notch 46 may extend diagonally so as to be away from the boundary line L2 as it is closer to the end 46a, or may be diagonally extended so as to be closer to the boundary L2 as it is closer to the end 46a. Good.

  The formation position of the notch 46 may be an intermediate position between the position where the edge 40f of the insulating sheet 40 intersects the imaginary line L3 and the position of the boundary line L2, or the position of the insulating sheet 40 more than the intermediate position. The position may be close to the position where the edge 40f and the virtual line L3 intersect. However, in the case where the cut portion 46 is formed at a position closer to the position where the edge 40f of the insulating sheet 40 and the imaginary line L3 intersect with each other than the intermediate position, the third surplus portion 53 is assembled with the insulating sheet 40 assembled. Can be formed close to the position where the edge 40f of the insulating sheet 40 and the imaginary line L3 intersect within a range where does not overlap the overlapping portion 52. In this modified example, if the formation position of the cut portion 46 is set so as to satisfy the relationship shown in the above-described Expression 1, the third surplus portion 53 does not overlap the overlapping portion 52.

  The notch 46 may be formed by only one of the pair of third insulating portions 43. In this case, the third insulating portion 43 having no notch 46 is not divided into the first part 44 and the second part 45, and the folding method is changed to the third insulating portion 43 having the notch 46. Is also possible. Even in such a form, in the third insulating portion 43 having the cutout portion 46, the insulating sheets 40 overlap at a maximum of three layers.

  In one of the pair of third insulating portions 43, only one of the pair of second parts 45 may have the cut portion 46. In this embodiment, since the notch 46 is not formed in one of the pair of second parts 45 in the third insulating portion 43, the overlap of the insulating sheet 40 increases compared to the above-described embodiment, and the overlap of the insulating sheet 40 is 4 at the maximum. Layer.

  The second end surfaces 30b on both sides in the stacking direction X of the electrode assembly 30 may be covered by the third insulating portion 43 of the insulating sheet 40. In this embodiment, in the insulating sheet 40, the third end surfaces 30 c on both sides in the width direction Y of the electrode assembly 30 are covered by the second insulating portion 42. Further, according to the change of the location of the electrode assembly 30 covered by the insulating sheet 40, the area occupied by the first insulating portion 41, the second insulating portion 42, and the third insulating portion 43 of the insulating sheet 40 is changed. Also in such a form, the cut portion 46 is formed in the third insulating portion 43, so that the maximum overlap in the insulating sheet 40 covering the second end surface 30 b of the electrode assembly 30 is reduced. For this reason, the gap between the second end face 30b of the electrode assembly 30 and the long side wall 22 of the case body 20 can be set small, and the same effect as in the above embodiment can be obtained.

The assembled insulating sheet 40 may be fixed with an adhesive tape.
The positive electrode 31 and the negative electrode 35 may have a structure in which an active material layer exists on one surface of a metal foil.

The positive electrode 31, the negative electrode 35, and the separator 39 may have a shape other than a rectangular shape such as an elliptical shape.
The magnitude relationship between the positive electrode 31, the negative electrode 35, and the separator 39 can be appropriately changed.

The electrode assembly 30 may be of a wound type in which a long strip-shaped positive electrode and a long strip-shaped negative electrode are wound via a long strip-shaped separator.
O The power storage device may be applied to another power storage device such as an electric double layer capacitor instead of the secondary battery.

  The secondary battery is a lithium-ion battery, but is not limited thereto, and may be another secondary battery.

L1, L2 boundary line, L3 virtual line, P1 intersection point, 10 secondary battery, 11 case, 20 case body, 21 bottom wall, 22 long side wall, 23 short side wall, 25 lid Reference numeral 30: electrode assembly, 30a: first end face, 30b: second end face, 30c: third end face, 31: positive electrode, 35: negative electrode, 39: separator, 40: insulating sheet, 40e, 40f: edge, 41: first insulating portion, 41a: long edge portion, 41b: short edge portion, 42: second insulating portion, 42a: short edge portion, 43: third insulating portion, 44: first part, 45: second part , 46: cut portion, 50: first surplus portion, 51: second surplus portion, 52: overlapping portion, 53: third surplus portion, 55: welding portion.

Claims (5)

An energy storage device comprising: an electrode assembly having a layered structure with a plurality of electrodes; a case accommodating the electrode assembly; and an insulating sheet insulating the electrode assembly and the case.
A first insulating portion disposed between the first end surface of the electrode assembly and the case; and a pair of second end surfaces connected to the first end surface of the electrode assembly and the case. And a pair of third insulating portions disposed between the case and a pair of third end surfaces connected to the first end surface and the second end surface in the electrode assembly. Have
In a state where the insulating sheet is expanded,
The pair of second insulating portions extend from a pair of opposing first edges of the edges of the first insulating portion, respectively.
One third insulating portion of the pair of third insulating portions extends from a second edge portion of the edge portions of the first insulating portion that is orthogonal to the pair of first edge portions. One part and a pair of second parts extending from a third edge part orthogonal to the pair of first edge parts among the edge parts of the pair of second insulation parts and positioned with the first part interposed therebetween. And parts,
The second part extends from an intersection of a boundary between the second insulating part and the second part and a boundary between the first part and the second part, and the second insulating part and the second part. When setting an imaginary line that extends diagonally with respect to the boundary with the part,
One of the pair of second parts is a second part, a boundary line between the first part and the second part, the imaginary line, and an edge of the insulating sheet facing the third edge. In a portion surrounded by a fourth edge portion, a notch portion is formed by cutting the second part over the fourth edge portion and the imaginary line,
The insulating sheet is assembled by being bent along the first edge, the second edge, and the third edge,
In a state where the insulating sheet is assembled,
The insulating sheet has an overlapping portion in which a portion surrounded by the third edge, the imaginary line, and the edge of the insulating sheet among the pair of second parts overlaps each other,
The first part overlaps the second part,
In one second part of the pair of second parts, a portion surrounded by the imaginary line, the notch, and the fourth edge overlaps another portion of the one second part. A power storage device characterized by being deployed without any problem.   The power storage device according to claim 1, wherein both of the pair of second parts have the cut portion. Both of the pair of third insulating portions include the first part and the pair of second parts,
The power storage device according to claim 2, wherein in each of the pair of third insulating portions, both of the pair of second parts have the cut portions.   4. The power storage device according to claim 1, further comprising a welded portion in which a portion of the second part where the first part overlaps and the first part are welded. 5. A method for manufacturing a power storage device, comprising: an electrode assembly having a layered structure including a plurality of electrodes; a case accommodating the electrode assembly; and an insulating sheet insulating the electrode assembly and the case.
The insulating sheet is a first insulating portion that can be disposed between a first end surface of the electrode assembly and the case, between a pair of second end surfaces connected to the first end surface of the electrode assembly and the case. And a pair of third insulating portions that can be disposed between the case and a pair of third end surfaces connected to the first end surface and the second end surface in the electrode assembly. Have
In a state where the insulating sheet is expanded,
The pair of second insulating portions extend from a pair of opposing first edges of the edges of the first insulating portion, respectively.
One third insulating portion of the pair of third insulating portions extends from a second edge portion of the edge portions of the first insulating portion that is orthogonal to the pair of first edge portions. One part and a pair of second parts extending from a third edge part orthogonal to the pair of first edge parts among the edge parts of the pair of second insulation parts and positioned with the first part interposed therebetween. And parts,
The second part extends from an intersection of a boundary between the second insulating part and the second part and a boundary between the first part and the second part, and the second insulating part and the second part. When setting an imaginary line that extends diagonally with respect to the boundary with the part,
One of the pair of second parts, the second part being a boundary line between the first part and the second part, the imaginary line, and the insulating sheet facing the third edge. In a portion surrounded by a fourth edge which is an edge, a notch is formed by cutting the second part over the fourth edge and the imaginary line,
By bending the insulating sheet along the first edge portion and the third edge portion, the insulating sheet is surrounded by the third edge portion, the virtual line, and the edge portion of the insulating sheet among the pair of second parts. The overlapped parts are formed by overlapping the
By bending the insulating sheet along the second edge, the first part is superimposed on the second part, and the imaginary line is formed on the second part of one of the pair of second parts. Manufacturing the power storage device, wherein the insulating sheet is assembled so that a portion surrounded by the cut portion and the fourth edge is developed without overlapping with another portion of one of the second parts. Method.