JP2020004644A - Power storage device and manufacturing method thereof - Google Patents

Abstract

To provide a power storage device that can suppress a decrease in capacity and a manufacturing method thereof.SOLUTION: A secondary battery includes an electrode assembly 12, an insulating sheet 30 covering the electrode assembly 12, and a case accommodating the electrode assembly 12 covered with the insulating sheet 30. The secondary battery includes a first overlapping portion 35 in which a first portion A1 and a second portion A2 which are parts of the insulating sheet 30 are overlapped with each other along the electrode assembly 12, and a second overlapping portion 36 in which a first portion B1 and a second portion B2 which are parts of the insulating sheet 30 are overlapped with each other along the electrode assembly 12. The second portions A2 and B2 have a plurality of holes 37, and the thickness H2 of the second portions A2 and B2 is smaller than the thickness H1 of the first portions A1 and B1.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a power storage device including an insulating sheet that covers an electrode assembly, and a method for manufacturing the power storage device.

  2. Description of the Related Art Conventionally, vehicles such as an EV (Electric Vehicle) and a PHV (Plug in Hybrid Vehicle) are equipped with a lithium ion secondary battery, a nickel hydrogen secondary battery, or the like as a power storage device for storing power supplied to an electric motor or the like. . A secondary battery includes an electrode assembly, an insulating sheet that covers the electrode assembly, and a case that houses the electrode assembly covered with the insulating sheet. The insulating sheet is located between the electrode assembly and the inner surface of the case, and insulates the electrode assembly from the case. The secondary battery disclosed in Patent Literature 1 has an overlapping portion in which one end in the longitudinal direction and the other end in the longitudinal direction of the strip-shaped insulating sheet are overlapped. Due to the overlapping portion, a gap is not formed between one end and the other end in the longitudinal direction of the insulating sheet, and the insulation between the electrode assembly and the case can be ensured.

JP 2014-41724 A

  By the way, when the overlapping portion is provided, the dimension of the insulating sheet increases in a direction in which both end portions of the insulating sheet overlap, so that when the electrode assembly covered with the insulating sheet is inserted into the case, the overlapping portion interferes with the case. Sometimes. In order to suppress this interference, the dimension of the electrode assembly in the direction in which both ends of the insulating sheet overlap may be reduced in consideration of an increase in the size of the insulating sheet due to the overlapping portion. However, when the size of the electrode assembly is reduced, the capacity of the secondary battery is reduced.

  SUMMARY An advantage of some aspects of the invention is to provide a power storage device capable of suppressing a reduction in capacity, and a method for manufacturing the power storage device.

  A power storage device for solving the above problems includes an electrode assembly, an insulating sheet that covers the electrode assembly, and a case that houses the electrode assembly covered with the insulating sheet. A power storage device including an overlapping portion in which a first part that is a part of a sheet and a second part that is a part of the insulating sheet are overlapped with each other along the electrode assembly. One of the second portions has a plurality of holes, and the thickness of the one is smaller than the thickness of the other.

  According to this, in the insulating sheet covering the electrode assembly, the thickness of the overlapping portion is smaller than that in the case where the thickness of the first portion and the thickness of the second portion are the same. The dimension of the insulating sheet in the direction in which the insulating sheet and the second portion overlap is reduced. Therefore, without reducing the size of the electrode assembly, interference between the overlapping portion and the case when the electrode assembly covered with the insulating sheet is inserted into the case can be suppressed, and a decrease in the capacity of the power storage device can be suppressed. . Further, when inserting the electrode assembly covered with the insulating sheet into the case, the overlapping portion may be sandwiched and pressed between the electrode assembly and the inner surface of the case. At this time, in one portion constituting the overlapping portion, the portion where the hole is not formed is stretched so as to escape to the space of the hole, so that the thickness of the one portion is further reduced while the electrode assembly is Can be inserted into

In the above power storage device, the hole is a square hole.
A method for manufacturing a power storage device for solving the above problems includes an electrode assembly, an insulating sheet covering the electrode assembly, and a case for housing the electrode assembly covered with the insulating sheet. A method for manufacturing a power storage device, comprising: an overlapping portion in which a first portion that is a part of the insulating sheet and a second portion that is a part of the insulating sheet are overlapped along the electrode assembly. A slit forming step of forming a plurality of slits in a portion that can be the first portion or the second portion in the insulating sheet; and a covering step of covering the electrode assembly with the insulating sheet and forming the overlapping portion. And accommodating the electrode assembly covered with the insulating sheet in the case. In the covering step, the first part and the second part One of said plurality of slits are formed, together with the pulling direction of the area of the overlapping portion is increased, and the gist of maintaining a state where the area is increased.

  According to this, by pulling one part where a plurality of slits are formed in the coating step, the slit is expanded to become a hole, and one part is stretched, so that the thickness of one part becomes the other. Becomes thinner than the thickness of the part. As a result, the thickness of the overlapping portion is reduced as compared with the case where the thickness of the first portion and the thickness of the second portion are the same, so that the dimension of the insulating sheet in the direction in which the first portion and the second portion overlap is smaller. Become smaller. Therefore, without reducing the size of the electrode assembly, interference between the overlapping portion and the case when the electrode assembly covered with the insulating sheet is inserted into the case can be suppressed, and a decrease in the capacity of the power storage device can be suppressed. . In addition, when the electrode assembly covered with the insulating sheet is inserted into the case in the housing process, the overlapping portion may be sandwiched and pressed between the electrode assembly and the inner surface of the case. At this time, in one portion constituting the overlapping portion, the portion where the hole is not formed is stretched out so as to escape to the space of the hole, so that the electrode assembly is further reduced while the thickness of the one portion is further reduced. Can be inserted into the case.

  Furthermore, since the slit is expanded when the insulating sheet is pulled in the covering step, the portion where the slit is formed is more easily stretched than the portion where the slit is not formed. For this reason, in the slit forming step, by forming a plurality of slits in a part that can be the first part or the second part in the insulating sheet, one part where the slit is formed when the insulating sheet is pulled is focused on It is stretched and the thickness of one part can be reduced.

  According to the present invention, a decrease in the capacity of the power storage device can be suppressed.

FIG. 2 is an exploded perspective view of the secondary battery of the embodiment. FIG. 4 is a cross-sectional view of a secondary battery. The top view of an insulating sheet. (A) is a top view which shows a coating process, (b) is a side view which shows a coating process. (A) is a top view which shows a coating process, (b) is a side view which shows a coating process. The top view showing the comparative example of the electrode assembly covered with the insulating sheet. The top view which shows another example of an insulating sheet. The top view which shows another example of the electrode assembly covered with the insulating sheet. The top view showing the comparative example of the electrode assembly covered with the insulating sheet.

Hereinafter, an embodiment in which a power storage device and a method for manufacturing the power storage device are embodied as a secondary battery and a method for manufacturing a secondary battery will be described with reference to FIGS. 1 to 5.
As shown in FIG. 1, a secondary battery 10 as a power storage device includes a case 11 and an electrode assembly 12 housed in the case 11. The case 11 has a rectangular parallelepiped case body 13 and a rectangular flat lid 14 for closing the opening 13 a of the case body 13. The case main body 13 and the lid 14 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). The case body 13 is erected from a rectangular plate-shaped bottom wall 13b, a pair of long side walls 13c erected from a pair of long side edges of the bottom wall 13b, and a pair of short side edges of the bottom wall 13b. And a pair of short side walls 13d. The case 11 is filled with an electrolytic solution (not shown). 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. 2, the electrode assembly 12 includes a plurality of rectangular sheet-like positive electrodes 21, negative electrodes 22, and separators 23. The electrode assembly 12 has a layered structure in which a separator 23 is interposed between the positive electrode 21 and the negative electrode 22 and is insulated from each other. The direction in which the positive electrode 21 and the negative electrode 22 are stacked is referred to as a stacking direction. The positive electrode 21 has a rectangular sheet-like positive metal foil (for example, aluminum foil) 24 and positive electrode active material layers 25 present on both surfaces of the positive metal foil 24. As shown in FIG. 1, the positive electrode 21 has a positive electrode tab 26 protruding from a part of one side of the positive metal foil 24. The positive electrode tab 26 does not have the positive electrode active material layer 25 and is formed of the positive electrode metal foil 24 itself. The negative electrode 22 includes a rectangular sheet-shaped negative electrode metal foil (for example, copper foil) 27 and negative electrode active material layers 28 present on both surfaces of the negative electrode metal foil 27. As shown in FIG. 1, the negative electrode 22 has a negative electrode tab 29 having a shape protruding from a part of one side of the negative metal foil 27. The negative electrode tab 29 does not have the negative electrode active material layer 28 and is formed of the negative electrode metal foil 27 itself.

  As shown in FIG. 1, the electrode assembly 12 includes a positive electrode tab group 15 in which positive electrode tabs 26 of each positive electrode 21 are stacked, and a negative electrode tab group 16 in which negative electrode tabs 29 of each negative electrode 22 are stacked. The electrode assembly 12 includes a tab side end surface 12a on an end surface having the positive electrode tab group 15 and the negative electrode tab group 16, and a bottom end surface 12b (see FIG. 4B) on an end surface opposite to the tab side end surface 12a. Prepare. The direction in which the tab side end surface 12a and the bottom side end surface 12b make a pair is defined as the height direction, and the direction orthogonal to the stacking direction and the height direction is defined as the width direction. The electrode assembly 12 includes a first end face 12c and a second end face 12d at end faces orthogonal to the tab side end face 12a and the bottom end face 12b and forming a pair in the stacking direction. The tab side end face 12a and the bottom end face 12b A third end face 12e and a fourth end face 12f are provided on the end faces that are orthogonal to and along the stacking direction.

  As shown in FIG. 1, the secondary battery 10 includes a positive terminal 17 and a negative terminal 18 for extracting electricity from the electrode assembly 12. The positive electrode terminal 17 has a conductive member 17a joined to the positive electrode tab group 15, and a shaft portion 17b connected to the conductive member 17a. The negative electrode terminal 18 has a conductive member 18a joined to the negative electrode tab group 16, and a shaft 18b connected to the conductive member 18a. The positive electrode terminal 17 is electrically connected to the electrode assembly 12 via the positive electrode tab group 15, and the negative electrode terminal 18 is electrically connected to the electrode assembly 12 via the negative electrode tab group 16. The tip of each of the shaft portions 17b and 18b protrudes out of the case 11 through the through hole 14a of the lid 14. An insulating ring 19 for insulating the lid 14 is attached to each of the shaft portions 17b and 18b.

  As shown in FIGS. 1 and 2, the secondary battery 10 includes an insulating sheet 30 that covers the electrode assembly 12. The insulating sheet 30 of the present embodiment is a stretched polypropylene (e-PP) film formed by uniaxially stretching a polypropylene (PP) film. Therefore, although not shown, the insulating sheet 30 has a plurality of nodes which are aggregates of the PP resin and a plurality of fibrils connecting the plurality of nodes. There is a gap between the nodes and the fibrils. The insulating sheet 30 covers five surfaces of the electrode assembly 12 except for the tab-side end surface 12a. The electrode assembly 12 is housed in the case 11 while being covered with the insulating sheet 30.

  The insulating sheet 30 has a rectangular bottom covering portion 30b that covers the bottom end surface 12b of the electrode assembly 12. The bottom cover 30b is located between the bottom end surface 12b of the electrode assembly 12 and the bottom wall 13b of the case body 13, and insulates the electrode assembly 12 from the case body 13. The longitudinal direction of the bottom cover 30b matches the width direction, and the short direction of the bottom cover 30b matches the stacking direction. The insulating sheet 30 has a rectangular first covering portion 30c that covers the first end face 12c of the electrode assembly 12. The first covering portion 30c is located between the first end surface 12c of the electrode assembly 12 and one of the long side walls 13c of the case body 13, and insulates the electrode assembly 12 from the case body 13. The insulating sheet 30 has a rectangular second covering portion 30d that covers the second end face 12d of the electrode assembly 12. The second covering portion 30d is located between the second end surface 12d of the electrode assembly 12 and the other long side wall 13c of the case body 13, and insulates the electrode assembly 12 from the case body 13. The longitudinal directions of the first covering portion 30c and the second covering portion 30d respectively correspond to the width direction, and the short sides of the first covering portion 30c and the second covering portion 30d correspond to the height direction, respectively. One long side of the bottom covering portion 30b is continuous with one long side of the first covering portion 30c, and the other long side of the bottom covering portion 30b is continuous with one long side of the second covering portion 30d. are doing.

  The insulating sheet 30 has a rectangular first ear 31 continuous with one short side of the first covering portion 30c, and a rectangular second ear 32 continuous with the other short side of the first covering 30c. Having. The insulating sheet 30 has a rectangular third ear 33 continuous with one short side of the second covering portion 30d, and a rectangular fourth ear 34 continuous with the other short side of the second covering 30d. Having. The longitudinal directions of the first to fourth ear portions 31 to 34 respectively correspond to the height direction, and the short direction of the first to fourth ear portions 31 to 34 respectively correspond to the laminating direction. The first ear portion 31 and the third ear portion 33 constitute a rectangular third covering portion 30e that covers the third end surface 12e of the electrode assembly 12. The third covering portion 30e is located between the third end face 12e of the electrode assembly 12 and one of the short side walls 13d of the case body 13, and insulates the electrode assembly 12 from the case body 13. The second ear portion 32 and the fourth ear portion 34 constitute a rectangular fourth covering portion 30f that covers the fourth end surface 12f of the electrode assembly 12. The fourth covering portion 30f is located between the fourth end face 12f of the electrode assembly 12 and the other short side wall 13d of the case body 13, and insulates the electrode assembly 12 from the case body 13.

  As shown in FIG. 2, in the secondary battery 10, a first portion A1 which is a part of the insulating sheet 30 and a second portion A2 which is a part of the insulating sheet 30 are formed by a third end face of the electrode assembly 12. The first overlap portion 35 is provided so as to be overlapped along the state 12e. The first portion A1 and the second portion A2 overlap in the width direction. In the present embodiment, the first overlapping portion 35 forms a part of the third covering portion 30e, and has a range of about four fifths near the first end face 12c of the electrode assembly 12 in the stacking direction, and a height. Located in the whole direction. In the present embodiment, the first portion A1 constituting the first overlapping portion 35 is the entire first ear portion 31, and the second portion A2 is a portion of the third ear portion 33 overlapping the first ear portion 31. The first part A1 is located inside the second part A2. In other words, the second part A2 is located outside the first part A1. The first portion A1 is located between the third end surface 12e of the electrode assembly 12 and the second portion A2, and the second portion A2 is located between the first portion A1 and the inner surface of one of the short side walls 13d of the case body 13. Located between. The secondary battery 10 has a welded portion 35 a in which the end of the third ear 33 along the height direction is welded to the first ear 31.

  In the secondary battery 10, a first portion B <b> 1 which is a part of the insulating sheet 30 and a second portion B <b> 2 which is a part of the insulating sheet 30 are overlapped with each other along a fourth end face 12 f of the electrode assembly 12. A second overlapping portion 36. The first portion B1 and the second portion B2 overlap in the width direction. In the present embodiment, the second overlapping portion 36 constitutes a part of the fourth covering portion 30f, and has a range of about four fifths near the first end face 12c of the electrode assembly 12 in the stacking direction, and a height. Located in the whole direction. In this embodiment, the first portion B1 of the second overlapping portion 36 is the entire second ear portion 32, and the second portion B2 is a portion of the fourth ear portion 34 overlapping the second ear portion 32. The first part B1 is located inside the second part B2. In other words, the second part B2 is located outside the first part B1. The first portion B1 is located between the fourth end face 12f of the electrode assembly 12 and the second portion B2, and the second portion B2 is located between the first portion B1 and the inner surface of the other short side wall 13d of the case body 13. Located between. The secondary battery 10 has a welded portion 36 a in which the end of the fourth ear 34 along the height direction is welded to the second ear 32.

  As shown in FIG. 1, each of the second portions A2 and B2 has a plurality of rectangular holes 37 as square holes. A plurality of holes 37 are arranged at intervals on a straight line extending in the height direction, and a plurality of rows of holes 37 arranged on the straight line are arranged in the stacking direction. The holes 37 are arranged such that the holes 37 adjacent in the stacking direction are not at the same position in the height direction. That is, the plurality of holes 37 are arranged in a staggered manner at the second portions A2 and B2. Further, as shown in FIG. 2, the thickness H2 of the second portions A2 and B2 is smaller than the thickness of portions other than the second portions A2 and B2 in the insulating sheet 30. That is, the thickness H2 of the second portions A2, B2 is smaller than the thickness H1 of the first portions A1, B1.

Next, a method for manufacturing the secondary battery of the present embodiment will be described.
The method for manufacturing the secondary battery 10 includes a slit forming step of forming a plurality of slits S in a part that can be the second parts A2 and B2 in the insulating sheet 30, a covering step of covering the electrode assembly 12 with the insulating sheet 30, And housing the electrode assembly 12 covered with the insulating sheet 30 in the case 11.

  FIG. 3 shows the insulating sheet 30 before covering the electrode assembly 12. The insulating sheet 30 of the present embodiment has a rectangular base 40 and first to fourth protrusions 41 to 44 projecting from the long side of the base 40. The length of the base portion 40 in the longitudinal direction is determined by the size of the bottom end surface 12b of the electrode assembly 12 in the stacking direction, the height of the first end surface 12c, and the height of the second end surface 12d. Approximately equals the sum of the dimensions. Here, when the electrode assembly 12 is manufactured with a maximum dimensional error, the dimension of the base portion 40 is set to be equal to that of the electrode assembly 12 so that the electrode assembly 12 does not protrude from the insulating sheet 30 when the electrode assembly 12 is manufactured with a maximum dimensional error. This is a state slightly larger than the size. The dimension of the base portion 40 in the lateral direction matches the dimension of the electrode assembly 12 in the width direction. The thickness of the insulating sheet 30 is substantially uniform throughout the insulating sheet 30.

  The first protrusion 41 protrudes from one end of one long side of the base 40, and the second protrusion 42 protrudes from one end of the other long side of the base 40. The third protruding portion 43 protrudes from the other end of one long side of the base portion 40, and the fourth protruding portion 44 protrudes from the other end of the other long side of the base portion 40. The longitudinal directions of the first to fourth protruding portions 41 to 44 respectively correspond to the longitudinal directions of the base portion 40, and the transverse directions of the first to fourth protruding portions 41 to 44 are respectively the transverse directions of the base portion 40. Matches. The lengths of the first to fourth protrusions 41 to 44 in the longitudinal direction respectively correspond to the height dimensions of the electrode assembly 12. Each of the widths of the first to fourth protrusions 41 to 44 in the lateral direction is shorter than the dimension of the electrode assembly 12 in the laminating direction, and is longer than half of the dimension in the laminating direction.

  In the longitudinal direction of the base portion 40, the first projecting portion 41 and the third projecting portion 43 are separated from each other, and the second projecting portion 42 and the fourth projecting portion 44 are separated from each other. On one long side of the base portion 40, the length of the portion where the first protrusion 41 and the third protrusion 43 are not located matches the dimension of the electrode assembly 12 in the stacking direction. On the other long side of the base portion 40, the length of the portion where the second protrusion 42 and the fourth protrusion 44 are not located matches the dimension of the electrode assembly 12 in the stacking direction.

  In the slit forming step, a plurality of slits S are formed in portions of the insulating sheet 30 that can be the second portions A2 and B2. In the present embodiment, the portions that can be the second portions A2 and B2 are about two-thirds of the third protruding portion 43 and the fourth protruding portion 44 that are located on the side opposite to the base portion 40 in the lateral direction. Part. A plurality of linear slits S are formed in the third protrusion 43. A plurality of slits S are formed at intervals on a straight line extending in the longitudinal direction of the third protrusion 43, and a plurality of rows of slits S formed on the straight line are formed in a plurality of rows in the short direction of the third protrusion 43. It is formed. Each slit S is formed such that the slits S adjacent in the short direction of the third protrusion 43 are not at the same position in the long direction. That is, the plurality of slits S are arranged in a staggered manner in the third projecting portion 43. A plurality of slits S are formed in the fourth protrusion 44 as in the third protrusion 43.

  As shown in FIGS. 4A and 4B, in the covering step, first, the base portion 40 of the insulating sheet 30 causes the bottom end surface 12 b, the first end surface 12 c, and the second end surface of the electrode assembly 12. Cover 12d. Thereby, the central part in the longitudinal direction of the base part 40 becomes the bottom-side covering part 30b, the part on one end side in the longitudinal direction of the base part 40 becomes the first covering part 30c, and the other end part in the longitudinal direction of the base part 40. The portion becomes the second covering portion 30d. Next, the third end surface 12e of the electrode assembly 12 is covered with the first protrusion 41 of the insulating sheet 30. In addition, the second protruding portion 42 of the insulating sheet 30 covers the fourth end face 12f of the electrode assembly 12. Thereby, the first protrusion 41 becomes the first ear 31, and the second protrusion 42 becomes the second ear 32. Note that a part of the third end face 12 e of the electrode assembly 12 is not covered by the first ear 31. Similarly, a part of the fourth end face 12 f of the electrode assembly 12 is not covered by the second ear 32.

  Next, as shown in FIGS. 5A and 5B, the third end face 12 e of the electrode assembly 12 is covered with the third protrusion 43 of the insulating sheet 30. As a result, the third protruding portion 43 becomes the third ear portion 33, and the first ear portion 31 and the third ear portion 33 form the third covering portion 30e. In the third covering portion 30e, a first overlapping portion 35 in which the first ear portion 31 and a part of the third ear portion 33 are overlapped in the width direction is formed. The entire first ear 31 is the first part A1, and the part of the third ear 33 that overlaps the first ear 31 is the second part A2. When covering the third end face 12 e with the third protrusion 43, the third protrusion 43 is pulled in the stacking direction toward the first end face 12 c of the electrode assembly 12. As a result, the plurality of slits S are expanded in the stacking direction to become rhombic holes 37 which are square holes, and the second portion A2 is extended in the stacking direction. As a result, the thickness H2 of the second portion A2 is smaller than the thickness H1 of the first portion A1. In addition, the area of the first overlapping portion 35 is increased by extending the second portion A2, compared to the area when the second portion A2 is not extended. In the present embodiment, the second portion A2 extends until the edge along the height direction overlaps the edge of the third end surface 12e of the electrode assembly 12 on the first end surface 12c side.

  Similarly, the fourth end surface 12f of the electrode assembly 12 is covered with the fourth protrusion 44 of the insulating sheet 30. As a result, the fourth protrusion 44 becomes the fourth ear 34, and the second ear 32 and the fourth ear 34 form the fourth covering portion 30f. The second covering portion 36 in which the second ear portion 32 and a part of the fourth ear portion 34 overlap in the width direction is formed in the fourth covering portion 30f. The entire second ear 32 is a first portion B1, and the portion of the fourth ear 34 that overlaps the second ear 32 is a second portion B2. When covering the fourth end face 12 f with the fourth protrusion 44, the fourth protrusion 44 is pulled in the stacking direction toward the first end face 12 c of the electrode assembly 12. As a result, the plurality of slits S are expanded in the stacking direction to become rhombic holes 37 that are square holes, and the second portion B2 is extended in the stacking direction. As a result, the thickness H2 of the second portion B2 is smaller than the thickness H1 of the first portion A1. Further, the area of the second overlapping portion 36 is increased by extending the second portion B2, compared to the area when the second portion B2 is not extended. In the present embodiment, the second portion B2 extends until the edge along the height direction overlaps the edge of the fourth end surface 12f of the electrode assembly 12 on the first end surface 12c side.

  After covering the electrode assembly 12 with the insulating sheet 30, the end of the third ear 33 is welded to the first ear 31 to form a welded portion 35a. Thereby, the state where the area of the first overlapping portion 35 is increased is maintained. The end of the fourth ear 34 is welded to the second ear 32 to form a welded portion 36a. Thus, the state where the area of the second overlapping portion 36 is increased is maintained.

  Here, the dimensions of the insulating sheet 30 covering the electrode assembly 12 will be described together with a comparative example. FIG. 6 shows the electrode assembly 12 covered with the insulating sheet 30 of the comparative example. The dimensions of the electrode assembly 12 are the same as the dimensions of the electrode assembly 12 of the present embodiment. In the comparative example, the slit forming step is omitted. In the covering step, the third protruding portion 43 covers the third end surface 12 e of the electrode assembly 12 without being pulled, and the fourth protruding portion 44 is formed without being pulled. 12f is covered. Therefore, the thickness H1 of the first portions A1 and B1 and the thickness H2 of the second portions A2 and B2 are the same. The thickness of the first overlapping portion 35 is a thickness obtained by adding the thickness H1 of the first portion A1 and the thickness H2 of the second portion A2, and the thickness of the second overlapping portion 36 is the same as the thickness H1 of the first portion B1. This is a thickness obtained by adding the thickness H2 of the two portions B2. Therefore, the thickness of the first overlapping portion 35 of the present embodiment is smaller than the thickness of the first overlapping portion 35 of the comparative example, and the thickness of the second overlapping portion 36 of the present embodiment is smaller than the thickness of the second overlapping portion 36 of the comparative example. Thinner than. As a result, in the insulating sheet 30 covering the electrode assembly 12, the width W5 of the insulating sheet 30 of the present embodiment in the width direction is smaller than the width W6 of the insulating sheet 30 of the comparative example. .

  In the housing step, the electrode assembly 12 covered with the insulating sheet 30 is housed in the case body 13. The electrode assembly 12 is inserted into the case body 13 from the bottom end surface 12b side. At this time, the first overlapping portion 35 is sandwiched and pressed by the third end surface 12e of the electrode assembly 12 and the inner surface of one of the short side walls 13d of the case body 13, and the second overlapping portion 36 is pressed by the electrode assembly 12 Of the case body 13 and the inner surface of the other short side wall 13d of the case body 13. Then, in the second portions A2 and B2, the portion where the hole 37 is not formed is pushed out so as to escape to the space of the hole 37. Thereby, the thickness H2 of the second portions A2 and B2 is further reduced.

  When the electrode assembly 12 is inserted into the case main body 13, the bottom cover 30 b of the insulating sheet 30 faces the inner surface of the bottom wall 13 b of the case main body 13, and the first cover 30 c is connected to one side of the case main body 13. The second covering portion 30d faces the inner surface of the other long side wall 13c of the case body 13. The third ear 33 of the third cover 30e faces the inner surface of one short side wall 13d of the case body 13, and the fourth ear 34 of the fourth cover 30f is connected to the other short side of the case body 13. It faces the inner surface of the side wall 13d. The holes 37 are formed only in the second portions A2 and B2 among the first portions A1 and B1 and the second portions A2 and B2 constituting the overlapping portions 35 and 36. Therefore, the insulation between the electrode assembly 12 and the case body 13 is ensured also in the first overlapping portion 35 and the second overlapping portion 36. Thereafter, the opening 13a of the case body 13 in which the electrode assembly 12 is housed is closed by the cover 14, and the case body 13 and the cover 14 are welded to complete the housing of the electrode assembly 12 in the case 11. I do.

The operation and effect of the present embodiment will be described.
(1) In the method of manufacturing the secondary battery 10, a step of forming a plurality of slits S in the third protrusion 43 that can be the second portion A <b> 2 in the insulating sheet 30 and covering the electrode assembly 12 with the insulating sheet 30. And a covering step of forming the first overlapping portion 35. In the covering step, by pulling the third protruding portion 43 in a direction in which the area of the first overlapping portion 35 increases, the slit S is expanded to become the hole 37 and the second portion A2 is extended, The thickness H2 of the two portions A2 is smaller than the thickness H1 of the first portion A1. For this reason, the thickness of the first overlapping portion 35 is smaller than the case where the thickness H1 of the first portion A1 and the thickness H2 of the second portion A2 are the same, and the thickness of the insulating sheet 30 covering the electrode assembly 12 is reduced. The dimension becomes smaller in the width direction in which the first portion A1 and the second portion A2 overlap. Therefore, the interference between the first overlapping portion 35 and the case body 13 when the electrode assembly 12 covered with the insulating sheet 30 is inserted into the case body 13 can be suppressed without reducing the dimensions of the electrode assembly 12, A decrease in the capacity of the secondary battery 10 can be suppressed.

  When the electrode assembly 12 covered with the insulating sheet 30 is inserted into the case main body 13 in the housing step, the first overlapping portion 35 is sandwiched and pressed between the electrode assembly 12 and the inner surface of the case main body 13. Sometimes. At this time, in the second portion A2, the portion where the hole 37 is not formed is stretched out so as to escape to the space of the hole 37, so that the thickness H2 of the second portion A2 is further reduced while the electrode assembly 12 is formed. Can be inserted into the case body 13.

  Furthermore, since the slit S is expanded when the insulating sheet 30 is pulled, a portion where the slit S is formed is more easily stretched than a portion where the slit S is not formed. For this reason, in the slit forming step, by forming a plurality of slits S in a portion that can be the second portion A2 in the third projecting portion 43, the second portion A2 is focused when the insulating sheet 30 is pulled in the covering process. And the thickness H2 of the second portion A2 can be reduced.

Similar effects can be obtained for the second overlapping portion 36 of the insulating sheet 30.
(2) The plurality of holes 37 are portions of the first portion A1, B1 and the second portions A2, B2 constituting the first overlap portion 35 and the second overlap portion 36, on the side facing the inner surface of the case body 13. At the second portions A2 and B2. For this reason, compared with the case where the plurality of holes 37 are formed in the first portions A1 and B1, the contact area between the first overlapping portion 35 and the second overlapping portion 36 and the inner surface of the case body 13 is reduced, Friction is suppressed. Therefore, the insertability of the electrode assembly 12 into the case main body 13 can be improved.

(3) The insulating sheet 30 is a film made of stretched polypropylene, and has a gap between the node and the fibril. Therefore, the electrolyte can be stored in the gap of the insulating sheet 30.
This embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

  The electrode assembly 12 may be a wound electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound while being insulated from each other. In this case, for example, by winding a band-shaped insulating sheet 30 longer than the circumference of the electrode assembly 12 around the electrode assembly 12, the electrode assembly 12 is covered with the insulating sheet 30. The insulating sheet 30 has an overlapping portion in which one end in the longitudinal direction as the first portion of the insulating sheet 30 and the other end in the longitudinal direction as the second portion are overlapped. The overlapping portion is located between the electrode assembly 12 and the side wall of the case 11. The case 11 is not limited to a rectangular parallelepiped, and may be a case including a case body 13 having a bottomed cylindrical shape and a lid 14 having a disk shape.

  The method of manufacturing the secondary battery 10 including the wound electrode assembly 12 includes a slit forming step, a covering step, and a housing step, as in the above embodiment. In the slit forming step, a plurality of slits are formed at one end in the longitudinal direction that can be the first portion of the insulating sheet 30 or at the other end in the longitudinal direction that can be the second portion. In the covering step, the electrode assembly 12 is covered with the insulating sheet 30 while pulling one end in which the plurality of slits are formed in the winding direction. Thereby, one end in the longitudinal direction as the first portion of the insulating sheet 30 and the other end in the longitudinal direction as the second portion are overlapped to form an overlapping portion. In addition, the slit is expanded to form a hole, and one end where the slit is formed is extended, so that the thickness of one portion is smaller than the thickness of the other portion. That is, the dimension of the insulating sheet 30 in the direction in which the first portion and the second portion of the insulating sheet 30 overlap each other is reduced by the decrease in thickness of one portion. In the housing step, the electrode assembly 12 covered with the insulating sheet 30 is housed in the case 11 such that the overlapping portion is located between the electrode assembly 12 and the side wall of the case body 13.

  Also in this case, without reducing the dimensions of the electrode assembly 12, interference between the overlapping portion and the case body 13 when the electrode assembly 12 covered with the insulating sheet 30 is inserted into the case body 13 can be suppressed. A decrease in the capacity of the secondary battery 10 can be suppressed.

  The insulating sheet 30 may be a polypropylene (PP) film or a stretched polypropylene film formed by biaxially stretching a polypropylene film. Further, the material of the insulating sheet 30 is not limited to polypropylene, and may be another material such as polyethylene (PE).

  The shape of the insulating sheet 30 before covering the electrode assembly 12 can cover the bottom end surface 12b and the first to fourth end surfaces 12c to 12f of the electrode assembly 12 and form an overlapping portion. If so, it may be changed as appropriate. Further, in the covering step, the order of covering the bottom end face 12b and the first to fourth end faces 12c to 12f of the electrode assembly 12 may be appropriately changed according to the shape of the insulating sheet 30.

  The number of overlapping portions provided in the secondary battery 10 may be appropriately changed according to the shape of the insulating sheet 30. For example, when covering the first to fourth end surfaces 12c to 12f of the electrode assembly 12 with the strip-shaped insulating sheet 30, one end in the longitudinal direction as the first portion of the insulating sheet 30 and the longitudinal portion as the second portion are formed. And the other end in the direction. Therefore, the secondary battery 10 includes one overlapping portion. Further, for example, when the first to fourth end surfaces 12c to 12f of the electrode assembly 12 are covered with three insulating sheets 30, the ends of the insulating sheets 30 are overlapped. That is, one end of the first insulating sheet 30 as the first part and one end of the second insulating sheet 30 as the second part are overlapped, and the other part of the second insulating sheet 30 as the first part The end and the one end of the third insulating sheet 30 as the second part are overlapped, and the other end of the third insulating sheet 30 as the first part and the first insulating sheet as the second part 30 and the other end. Therefore, the secondary battery 10 includes three overlapping portions.

The slit S formed in the insulating sheet 30 in the slit forming step is not limited to a line shape, and may be, for example, a pore shape. In this case, the hole 37 has an elliptical shape.
The length and number of the slits S formed in the insulating sheet 30 may be appropriately changed according to the desired amount of extension of the second portions A2 and B2. The slits S are arranged so that the second portions A2 and B2 are uniformly stretched.

  In the slit forming step, a plurality of slits S may be formed in the first protruding portion 41, which is a portion that can be the first portion A1, instead of the third protruding portion 43. In this case, in the covering step, the first protruding portion 41 covers the third end surface 12e of the electrode assembly 12 while pulling the first protruding portion 41 toward the second end surface 12d in the stacking direction. Thereby, each slit S is expanded to become the hole 37, and the first portion A1 is extended, so that the thickness H1 of the first portion A1 is smaller than the thickness H2 of the second portion A2.

  Similarly, in the slit forming step, a plurality of slits S may be formed in the second protrusion 42, which is a part that can be the second part B2, instead of the fourth protrusion 44. In this case, in the covering step, the second protruding portion 42 covers the fourth end surface 12f of the electrode assembly 12 while pulling the second protruding portion 42 toward the second end surface 12d in the stacking direction. Thereby, each slit S is expanded to become the hole 37, and the first portion B1 is extended, so that the thickness H1 of the first portion B1 is smaller than the thickness H2 of the second portion B2. That is, the dimension in the width direction of the insulating sheet 30 in a state where the electrode assembly 12 is covered is reduced by the reduction in the thickness H2 of the second portions A2 and B2. Therefore, without reducing the size of the electrode assembly 12, interference between the overlapping portion and the case main body 13 when the electrode assembly 12 covered with the insulating sheet 30 is inserted into the case main body 13 can be suppressed, and the secondary battery can be suppressed. 10 can be suppressed from decreasing.

  The end face of the electrode assembly 12 where the overlapping portion is located is not limited to the third end face 12e and the fourth end face 12f, but may be the first end face 12c or the second end face 12d. That is, the end face where the overlapping portion is located in the electrode assembly 12 may be an end face facing the side wall of the case 11. Further, the overlapping portion may be located over a plurality of end faces of the electrode assembly 12.

  For example, as in the case of the insulating sheet 30 shown in FIG. 7, the size of the first protrusion 41 and the second protrusion 42 in the stacking direction may be longer than the size of the electrode assembly 12 in the stacking direction. In this case, as shown in FIG. 8, the first ear 31 (first protrusion 41) covers a part of the second end face 12d in addition to the third end face 12e of the electrode assembly 12, and The portion 32 (the second protrusion 42) covers a part of the second end surface 12d in addition to the fourth end surface 12f of the electrode assembly 12. The dimension of the third protruding portion 43 and the fourth protruding portion 44 in the laminating direction is shorter than the dimension of the electrode assembly 12 in the laminating direction.

  At this time, the first overlapping portion 51 is located over two surfaces of the second end surface 12d and the third end surface 12e of the electrode assembly 12. The first overlapping portion 51 is configured such that a part of the first ear 31 as the first part C1 and a part of the second covering part 30d as the second part C2 are overlapped in the stacking direction, and the first part D1 And a part of the first ear 31 as the second part D2 and the entire third ear 33 as the second part D2 are overlapped in the width direction. Similarly, the second overlapping portion 52 is located over two surfaces of the second end surface 12 d and the fourth end surface 12 f of the electrode assembly 12. In the second overlapping portion 52, a part of the second ear 32 as the first part E1 and a part of the second covering part 30d as the second part E2 are overlapped in the stacking direction, and the first part F1 is formed. And a part of the second ear part 32 as the second part F2 and the entire fourth ear part 34 as the second part F2 are overlapped in the width direction. The first portions C1 to F1 are located inside the second portions C2 to F2.

  In this case, in the slit forming step, a plurality of slits S are formed in the first protrusion 41 and the second protrusion 42 that can be the first portions C1 to F1 of the insulating sheet 30. In the coating step, the first protrusion 41 is pulled when the first protrusion 41 covers the third end face 12 e and the second end face 12 d of the electrode assembly 12 in this order. Similarly, the second protrusion 42 is pulled when the second protrusion 42 covers the fourth end face 12 f and the second end face 12 d of the electrode assembly 12 in this order. Thereby, each slit S is expanded and becomes the hole 37, and the thickness H3 of the first portions C1 to F1 is larger than the thickness H4 of the second portions C2 to F2 by extending the first portions C1 to F1. Also become thin.

  Here, the dimensions of the insulating sheet 30 covering the electrode assembly 12 will be described together with a comparative example. FIG. 9 shows the electrode assembly 12 covered with the insulating sheet 30 of the comparative example. In the comparative example, the slit forming step is omitted. In the covering step, the first portions C1 to F1 are covered with the electrode assembly 12 without being pulled. Therefore, the thickness H3 of the first portions C1 to F1 and the thickness H4 of the second portions C2 to F2 are the same.

  Therefore, the thickness of the first overlapping portion 51 of the above example is smaller than the thickness of the first overlapping portion 51 of the comparative example, and the thickness of the second overlapping portion 52 of the above example is the second overlapping portion 52 of the above comparative example. Thinner than. As a result, in the insulating sheet 30 covered with the electrode assembly 12, the dimension W81 in the stacking direction of the insulating sheet 30 of the above example is smaller than the dimension W91 of the comparative example in the stacking direction. . The width W82 of the insulating sheet 30 in the above example in the width direction is smaller than the width W92 of the insulating sheet 30 of the comparative example in the width direction.

  Also in this case, the first overlapping portion 51 and the second overlapping portion 52 when the electrode assembly 12 covered with the insulating sheet 30 is inserted into the case main body 13 without reducing the dimensions of the electrode assembly 12 and the case main body. 13 can be suppressed, and a decrease in the capacity of the secondary battery 10 can be suppressed.

  The method of fixing the end of the third ear 33 to the first ear 31 is not limited to welding and may be changed as appropriate. If the end of the third ear 33 is not turned up and the area of the first overlapping portion 35 is maintained after the increase, the third ear 33 is fixed to the first ear 31. It is not necessary. Similarly, the method of fixing the end of the fourth ear 34 to the second ear 32 is not limited to welding and may be changed as appropriate. If the end of the fourth ear 34 is not turned up and the area of the second overlapping portion 36 is maintained in a state after the increase, the fourth ear 34 is not fixed to the second ear 32. May be.

  The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. The point is that any material can be used as long as ions move between the positive electrode active material and the negative electrode active material and transfer charges.

The power storage device can be applied to a power storage device other than a secondary battery, such as a capacitor.
The technical idea that can be grasped from the above embodiment will be described.

(A) The power storage device according to claim 1 or 2, wherein one of the first portion and the second portion facing the case has the plurality of holes.
(B) in the covering step, covering the electrode assembly with the insulating sheet such that one of the first part and the second part, in which the plurality of slits are formed, is positioned outside the other. The method for manufacturing a power storage device according to claim 3.

DESCRIPTION OF SYMBOLS 10 ... Rechargeable battery as a power storage device, 11 ... Case, 12 ... Electrode assembly, 30 ... Insulating sheet, 35 ... First overlapping part as an overlapping part, 36 ... Second overlapping part as an overlapping part, 37 ... Hole 51, a first overlapping portion as an overlapping portion, 52, a second overlapping portion as an overlapping portion, A1 to F1, a first portion, A2 to F2, a second portion, and S, a slit.

Claims (3)

An electrode assembly;
An insulating sheet covering the electrode assembly;
A case accommodating the electrode assembly covered with the insulating sheet,
With
A power storage device including an overlapping portion in which a first part that is a part of the insulating sheet and a second part that is a part of the insulating sheet are overlapped with each other along the electrode assembly,
One of the first portion and the second portion has a plurality of holes, and the thickness of the one is smaller than the thickness of the other.   The power storage device according to claim 1, wherein the hole is a square hole. An electrode assembly;
An insulating sheet covering the electrode assembly;
A case accommodating the electrode assembly covered with the insulating sheet,
With
A method for manufacturing a power storage device including an overlapping portion in which a first part that is a part of the insulating sheet and a second part that is a part of the insulating sheet are overlapped with each other along the electrode assembly,
A slit forming step of forming a plurality of slits in a portion that can be the first portion or the second portion in the insulating sheet;
A coating step of forming the overlapping portion while covering the electrode assembly with the insulating sheet;
A housing step of housing the electrode assembly covered by the insulating sheet in the case;
With
In the covering step, one of the first and second portions, in which the plurality of slits are formed, is pulled in a direction in which the area of the overlapping portion increases, and the state in which the area is increased is maintained. A method for manufacturing a power storage device.