JP2016062659A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device, the junction of a battery case of which is not broken even if a battery assembly expands, by making a surface pressure act equally for an electrode assembly in the battery case.SOLUTION: A case body 35 of a battery case 11 has a cylindrical wall 40 including an opening side end, and a bottom wall 41 provided at an end on the opposite side of the opening side end. The cylindrical wall 40 includes a pair of first sidewalls 42 abutting against the end face of a battery assembly in the lamination direction, and arranged in parallel with each other, and a pair of second sidewalls perpendicular to the pair of first sidewalls 42, and arranged in parallel with each other. The first sidewalls 42 includes an opening side ramp 46 extending from the opening side toward the bottom wall 41, and inclining for the housing direction of the electrode assembly 12, a bottom side ramp 47 extending from the bottom wall 41 side toward the opening side, and an intermediate part 48 formed between opening side ramp 46 and bottom side ramp 47, and making the interval of the pair of first sidewalls 42 constant. The end face of the electrode assembly 12 in the lamination direction abuts against the intermediate part 48.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power storage device.

  In recent years, lithium ion secondary batteries have been adopted not only as power sources for electronic devices but also as power sources for hybrid vehicles and electric vehicles. Usually, a battery case of a lithium ion secondary battery contains an electrode assembly as a power generation element. The electrode assembly includes a positive electrode obtained by applying a positive electrode active material to a metal foil, and a negative electrode active material on the metal foil. It has a coated negative electrode and a separator interposed between the positive electrode and the negative electrode. As an electrode assembly, for example, there are a wound electrode assembly and a stacked electrode assembly. The wound electrode body is formed by winding an electrode sheet with a separator interposed between a long positive electrode and a negative electrode. On the other hand, a stacked electrode assembly has a structure in which a large number of positive electrodes, negative electrodes, and separators are alternately stacked.

  As a prior art of a power storage device, for example, a rectangular sealed battery disclosed in Patent Document 1 is known. In the rectangular sealed battery disclosed in Patent Document 1, a sealing plate is airtightly welded to an opening of a rectangular battery case into which an electrode plate group is inserted. 90% to 97% of the maximum thickness of the prismatic battery case at the position of 1/2 to 1/3 of the total battery height from the bottom surface on both side walls facing in the direction of stacking the electrode group of the prismatic battery case. A curved concave portion having a minimum thickness portion of% is provided. According to the square sealed battery disclosed in Patent Document 1, leakage due to the occurrence of tensile stress cracks in the weld seal due to expansion of the electrode plate group is prevented.

  Moreover, as another prior art, the nonaqueous electrolyte secondary battery disclosed by patent document 2 can be mentioned, for example. The non-aqueous electrolyte secondary battery disclosed in Patent Document 2 has an electrode element in which a positive electrode and a negative electrode 1 are insulated by a resin porous separator, and a non-aqueous electrolyte is injected with the non-aqueous electrolyte It is a secondary battery. In the nonaqueous electrolyte secondary battery disclosed in Patent Document 2, the battery case has a convex portion in the inner direction, and before the electrode element is inserted in a direction perpendicular to the surface having the convex portion. The thickness in the case is 0.3 times or more and less than 1.09 times the electrode element thickness. According to the non-aqueous electrolyte secondary battery disclosed in Patent Document 2, the electrodes are sufficiently in close contact with each other, and the expansion of the battery case can be suppressed even when exposed to high temperatures.

Japanese Patent Laid-Open No. 5-28973 JP-A-9-199089

  However, in the rectangular sealed battery disclosed in Patent Document 1 and the nonaqueous electrolyte secondary battery disclosed in Patent Document 2, there is a problem that the surface pressure does not act equally on the electrode assembly in the battery case. is there. If the surface pressure does not act evenly on the electrode assembly in the battery case, for example, the battery performance becomes unstable due to the occurrence of uneven expansion, and an internal short circuit is likely to occur when the electrode assembly expands. There is a risk of problems such as this.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a power storage device that can apply a surface pressure evenly to an electrode assembly in a battery case.

  In order to solve the above problems, the present invention provides a layered electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked or wound while maintaining an insulating state, and a battery case containing the electrode assembly And the battery case includes a bottomed cylindrical case main body having an opening, and a lid joined to an opening side end formed on the opening side of the case main body, and the case main body Comprises a cylindrical wall having a rectangular cross section provided with the opening side end, and a bottom wall provided at an end of the cylindrical wall opposite to the opening side end, and the cylindrical wall is A pair of first side walls that are in contact with end surfaces of the electrode assembly in the stacking direction and are arranged in parallel with each other; and a pair of second side walls that are arranged in parallel with each other so as to be orthogonal to the pair of first side walls. And the first side wall is formed on the opening side. An opening-side inclined portion, a bottom-side inclined portion formed on the bottom wall side, and an intermediate portion formed between the opening-side inclined portion and the bottom-side inclined portion, The bottom inclined portion is formed so as to be inclined with respect to the accommodation direction of the electrode assembly so as to narrow the gap between the pair of first side walls from the opening side toward the bottom wall side. The gap between the pair of first side walls is narrowed from the wall side toward the opening side, and is inclined with respect to the accommodation direction of the electrode assembly, and the intermediate portion is formed of the pair of first side walls. The electrode assembly is formed so as to have a constant interval, and an end face in the stacking direction of the electrode assembly is in contact with the intermediate portion.

  According to the present invention, the electrode assembly in the battery case is sandwiched between the pair of first side walls in the stacking direction. Since the opening-side inclined portion, the bottom-side inclined portion, and the intermediate portion are formed on the first side wall, the end surface in the stacking direction of the electrode assembly uniformly contacts the intermediate portion of the first side wall. For this reason, the end surface in the stacking direction of the electrode assembly can receive a more uniform surface pressure from the first side wall.

In the above power storage device, the length of the bottom inclined portion in the accommodation direction may be set smaller than the length of the opening side inclined portion in the accommodation direction.
In this case, the inclination of the opening-side inclined portion that is the bonding side between the case body and the lid is smaller than the inclination of the bottom-side inclined portion. For this reason, the stress which acts on the junction part of a case main body and a cover body at the time of expansion | swelling of an electrode assembly can be suppressed, and the fracture | rupture in the junction part at the time of expansion | swelling can be prevented. Even if the slope of the bottom slope portion is larger than the slope of the opening slope portion, there is no joint, so the vicinity of the bottom slope portion does not break during expansion.

Further, in the above power storage device, the electrode assembly is configured such that the plurality of positive electrodes and the plurality of negative electrodes are alternately stacked while maintaining an insulating state, and an end portion of the positive electrode on the opening side and the bottom wall side. And it is good also as a structure which is a laminated electrode assembly in which the edge part of the said negative electrode is each formed.
In this case, the end surface in the stacking direction of the stacked electrode assembly can receive a more uniform surface pressure from the first side wall. In addition, when the space portion on the opening side inclined portion side in the battery case is larger than the space portion on the bottom side inclined portion side, an electrode or an electrode attachment member is provided on the opening side. A suitable space can be realized.

In the above power storage device, the length of the opening-side inclined portion in the accommodation direction is set based on the position of the end of the electrode assembly housed in the case body on the opening side of the positive electrode. The length of the bottom inclined portion in the housing direction may be set based on the position of the end of the electrode assembly housed in the case body on the bottom wall side of the positive electrode. .
In this case, the bottom inclined portion is set based on the position of the end portion on the bottom wall side of the positive electrode of the stacked electrode assembly. For this reason, an intermediate part can be contact | abutted in the site | part which a positive electrode and a negative electrode mutually overlap in an electrode assembly, and it can be made not to contact | abut to the site | part which a positive electrode and a negative electrode do not mutually overlap. Therefore, a more uniform surface pressure can be applied to the portion that expands in the electrode assembly from the middle portion of the first side wall.

  According to the present invention, it is possible to provide a power storage device in which a surface pressure is uniformly applied to an electrode assembly in a battery case so that a joint portion of the battery case does not break even when the electrode assembly expands.

1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. It is a longitudinal cross-sectional view of the secondary battery which concerns on embodiment of this invention. It is a disassembled perspective view of a part of electrode assembly. It is an arrow view of the AA line in FIG. It is explanatory drawing explaining the manufacturing method of the case main body of a battery case. It is a longitudinal cross-sectional view which shows the secondary battery which concerns on a modification.

Hereinafter, a power storage device according to an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, a secondary battery as a power storage device is illustrated, and the secondary battery of the present embodiment is specifically a lithium ion secondary battery.

  As shown in FIGS. 1 and 2, the secondary battery 10 of the present embodiment is a rectangular secondary battery. An electrode assembly 12 is accommodated in the battery case 11 of the secondary battery 10. The longitudinal direction of the battery case 11 shown in FIG. 1 is shown as the left-right direction, the height direction of the battery case 11 is shown as the up-down direction, and the short direction of the battery case 11 is shown as the front-rear direction. The height direction of the battery case 11 coincides with the accommodation direction of the electrode assembly 12. The electrode assembly 12 is a power generation element that generates a battery function (charging / discharging, etc.).

  As shown in FIG. 3, the electrode assembly 12 includes a sheet-like positive electrode 13 and a sheet-like negative electrode 14. The positive electrode 13 includes a rectangular positive electrode main body 15 and a strip-shaped positive electrode current collector 16 formed at the edge of the positive electrode main body 15. The positive electrode body 15 includes a positive electrode metal foil 17 and a positive electrode active material layer 18 formed of a positive electrode active material coated on both surfaces of the positive electrode metal foil 17. The positive electrode current collector 16 is formed of a positive electrode metal foil 17, and the positive electrode current collector 16 is not coated with a positive electrode active material. In addition, the positive electrode metal foil 17 of this embodiment is an aluminum foil.

  The negative electrode 14 includes a rectangular negative electrode main body 19 and a strip-shaped negative electrode current collector 20 formed at the edge of the negative electrode main body 19. The negative electrode main body 19 has a negative electrode metal foil 21 and a negative electrode active material layer 22 formed of a negative electrode active material coated on both surfaces of the negative electrode metal foil 21. The negative electrode current collector 20 is formed of a negative electrode metal foil 21, and the negative electrode current collector 20 is not coated with a negative electrode active material. In addition, the negative electrode metal foil 21 of this embodiment is a copper foil. The left and right and top and bottom dimensions of the negative electrode body 19 are set slightly larger than the positive electrode body 15.

  The electrode assembly 12 has a separator 23 that insulates between the positive electrode 13 and the negative electrode 14, and has a layered structure in which the plurality of positive electrodes 13 and the plurality of negative electrodes 14 are alternately stacked while maintaining an insulating state. That is, the electrode assembly 12 of this embodiment is a stacked electrode assembly in which a plurality of positive electrodes 13 and a plurality of negative electrodes 14 are alternately stacked while maintaining an insulating state. The separator 23 is set to have substantially the same dimensions as the negative electrode body 19. For example, as shown in FIGS. 3 and 4, the electrode assembly 12 is configured by laminating a plurality of positive electrodes 13 and a plurality of negative electrodes 14. In this embodiment, both end surfaces of the electrode assembly 12 in the stacking direction are constituted by the negative electrodes 14.

  The positive electrode current collectors 16 are arranged in a row along the stacking direction of the electrode assemblies 12. Each of the negative electrode current collectors 20 is arranged in a row along the stacking direction like the positive electrode current collector 16 so as not to overlap with the positive electrode current collector 16. In the present embodiment, the positive electrode current collectors 16 are set to the same size, and the negative electrode current collectors 20 are also set to the same size. Each positive electrode current collector 16 is collected on the front side of the electrode assembly 12 to form a positive electrode current collection group 25. Each negative electrode current collector plate 28 is collected on the front side of the electrode assembly 12 in the same manner as the positive electrode current collector 16 to form a negative electrode current collector group 26.

  A positive electrode current collecting plate 27 is bonded to the positive electrode current collecting group 25, and a negative electrode current collecting plate 28 is bonded to the negative electrode current collecting group 26. As shown in FIG. 2, the positive electrode current collector plate 27 is provided with a positive electrode terminal 30 that is electrically connected via an overcurrent protection circuit 29. Further, the negative electrode current collector plate 28 is provided with a negative electrode terminal 31 that is electrically connected via an overcurrent protection circuit 29.

  Next, the battery case 11 will be described. The battery case 11 includes a bottomed cylindrical case body 35 and a rectangular flat plate-shaped lid body 37 that closes the opening 36 of the case body 35 (see FIGS. 1 and 4). The case main body 35 and the lid body 37 are made of a metal material (for example, aluminum). The lid 37 is fixed to the case body 35 by laser welding. As shown in FIG. 2, an insulating sheet 38 as an insulating member for insulating the electrode assembly 12 accommodated in the battery case 11 is attached to the inner surface of the case body 35. Further, an insulating sheet 39 as an insulating member is attached to the inner side surface of the lid 37 as an insulating member for insulation from the electrode assembly 12 housed in the battery case 11.

  As shown in FIG. 1, the case main body 35 includes a cylindrical wall 40 having a rectangular cross section, and a bottom wall 41 formed so as to close an end of the case main body 35 opposite to the opening 36. The cylindrical wall 40 includes a pair of first side walls 42 arranged in parallel to each other and a pair of second side walls 43 orthogonal to the pair of first side walls 42 and arranged in parallel to each other. The first side wall 42 of the present embodiment has the largest area in the battery case 11. The opening 36 of the cylindrical wall 40 is rectangular, and an opening side end 44 is formed on the opening 36 side of the cylindrical wall 40. The opening-side end portion 44 is a portion joined to the lid body 37 and has an end surface perpendicular to the inner surface of the cylindrical wall 40.

  In the present embodiment, as shown in FIG. 4, the first side wall 42 includes an opening-side inclined portion 46 on the opening 36 side. The opening-side inclined portion 46 extends while inclining with respect to the vertical direction (accommodating direction of the electrode assembly 12) so as to narrow the distance between the pair of first side walls 42 from the opening 36 side toward the bottom wall 41 side. Exists. Accordingly, the interval in the stacking direction of the first side walls 42 decreases from the opening 36 side toward the bottom wall 41 side. The size of the opening-side inclined portion 46 in the vertical direction is such that the battery case 11 in which the positive electrode current collecting group 25, the negative electrode current collecting group 26, the positive electrode current collecting plate 27, the negative electrode current collecting plate 28, and the like provided in the electrode assembly 12 are accommodated. Is defined corresponding to the space on the opening 36 side. The opening side inclined portion 46 constitutes a part of the end face 45. In the present embodiment, the end portion on the bottom wall 41 side of the opening-side inclined portion 46 is located at the end portion on the opening 36 side of the negative electrode 14 in the electrode assembly 12.

  As shown in FIG. 4, the first side wall 42 includes a bottom inclined portion 47 on the bottom wall 41 side. The bottom inclined portion 47 is inclined with respect to the vertical direction (accommodating direction of the electrode assembly 12) so as to narrow the interval in the stacking direction of the pair of first side walls 42 from the bottom wall 41 side toward the opening 36 side. And extend. The bottom inclined portion 47 is formed continuously with the bottom wall 41. Therefore, the distance between the first side walls 42 in the stacking direction decreases from the bottom wall 41 side toward the opening 36 side. The vertical dimension of the bottom inclined portion 47 is set based on the end of the positive electrode 13 on the bottom wall 41 side in the electrode assembly 12 accommodated in the battery case 11. Therefore, the length of the bottom side inclined portion 47 in the accommodation direction is set smaller than that of the opening side inclined portion 46. In the present embodiment, the bottom side so that the end on the opening 36 side of the bottom inclined portion 47 coincides with the end on the bottom wall 41 side of the positive electrode 13 in the electrode assembly 12 accommodated in the battery case 11. The vertical dimension of the inclined portion 47 is set. In the present embodiment, the area of the opening 36 and the area inside the bottom wall 41 are set to the same area. Accordingly, the inclination angle of the opening-side inclined portion 46 with respect to the vertical direction is set smaller than the inclination angle of the bottom-side inclined portion 47.

  An intermediate portion 48 is formed between the opening-side inclined portion 46 and the bottom-side inclined portion 47. The intermediate portion 48 is not inclined with respect to the vertical direction, and the interval between the pair of first side walls 42 in the stacking direction is constant. The interval between the intermediate portions 48 in the pair of first side walls 42 is set in consideration of the expansion of the electrode assembly 12. Accordingly, the case body 35 is formed with a recess in the stacking direction in anticipation of the expansion of the electrode assembly 12. The intermediate portion 48 uniformly abuts over both end surfaces of the electrode assembly 12 in the stacking direction when the electrode assembly 12 is accommodated in the battery case 11. That is, the electrode assembly 12 receives an equal surface pressure in the stacking direction from the intermediate portion 48. Even if the electrode assembly 12 expands within a certain range in the stacking direction due to charging or the like, the deformation of the intermediate portion 48 in the stacking direction is stopped. In FIG. 4, the inclination angles of the opening-side inclined portion 46 and the bottom-side inclined portion 47 are exaggerated, but the inclination angles of the opening-side inclined portion 46 and the bottom-side inclined portion 47 are actually from the appearance. The tilt angle cannot be discriminated by visual inspection. In FIG. 4, the illustration of the separator 23 is omitted.

  The case body 35 of the present embodiment is manufactured as shown in FIG. First, a preform P of the case body 35 is obtained from a metal plate as a material by plastic forming using a press die (not shown). In the preform P, the opening-side inclined portion 46 and the bottom-side inclined portion 47 are not formed, and the interval between the portions corresponding to the first side wall 42 in the preform P is constant. Next, the preform P is placed in a hydroforming mold M, and the preform P is filled with the high-pressure liquid L. By filling the preform P with the high-pressure liquid L, an opening-side inclined portion 46 and a bottom-side inclined portion 47 are formed on the wall portion corresponding to the first side wall 42, and as a result, the case body 35 is obtained.

  As shown in FIGS. 1 and 2, the lid body 37 is formed with a pair of through holes 49 through which the positive electrode terminal 30 and the negative electrode terminal 31 of the electrode assembly 12 are inserted. An insulating ring 50 is attached to the through hole 49, and the insulating ring 50 is intended to insulate the positive electrode terminal 30 and the negative electrode terminal 31 from the lid body 37. The lid 37 is provided with a liquid injection port (not shown) for injecting the electrolytic solution into the battery case 11, and the liquid injection port is sealed by a sealing member (illustration). A safety valve (not shown) is provided near the center of the lid 37 in the longitudinal direction. The safety valve has a function of opening when the pressure in the battery case 11 reaches a predetermined pressure due to the generation of gas in the battery case 11 and releasing the gas in the battery case 11 to the outside.

  In the secondary battery 10 of the present embodiment, the electrode assembly 12 is accommodated in the case body 35. In a state where the electrode assembly 12 is housed in the case body 35, the upper end of the positive electrode body 15 corresponds to the end of the case body 35 on the opening 36 side, and the lower end of the positive electrode body 15 is the bottom wall 41 of the case body 35. It corresponds to the end of the side. The upper end of the negative electrode main body 19 corresponds to the end of the case main body 35 on the opening 36 side, and the lower end of the negative electrode main body 19 corresponds to the end of the case main body 35 on the bottom wall 41 side. The intermediate portion 48 applies a uniform surface pressure in the stacking direction to the portion where the positive electrode 13 and the negative electrode 14 overlap in the electrode assembly 12. Thereafter, the lid body 37 is joined to the case body 35 by laser welding, and the electrolytic solution is injected into the case body 35 through the injection port. After pouring, the pouring port is sealed, and initial charging is performed in the conditioning process. Although the electrode assembly 12 expands in the stacking direction after the initial charging, the portion where the positive electrode 13 and the negative electrode 14 overlap in the electrode assembly 12 receives an equal surface pressure in the stacking direction from the intermediate portion 48, so that the performance as a battery is improved. Stable and difficult to cause internal short circuit during expansion. In the present embodiment, the case main body 35 that anticipates the expansion of the electrode assembly 12 is formed in advance. When the case main body 35 expands within the expected range, the laser between the case main body 35 and the lid 37 is caused by the expansion. The welded joint is not broken or cracked at this joint. Therefore, the pressure resistance performance of the battery case 11 does not deteriorate.

The secondary battery 10 of this embodiment has the following effects.
(1) The electrode assembly 12 in the battery case 11 is sandwiched between the pair of first side walls 42 in the stacking direction. Since the opening side inclined portion 46, the bottom side inclined portion 47, and the intermediate portion 48 are formed on the first side wall 42, the end surface in the stacking direction of the electrode assembly 12 contacts the intermediate portion 48 of the first side wall 42 uniformly. . For this reason, the end surface of the electrode assembly 12 in the stacking direction can receive a more uniform surface pressure from the first side wall 42. As a result, the performance as a battery is stabilized, and even if the electrode assembly 12 expands, an internal short circuit hardly occurs.

(2) The opening-side inclined portion 46 and the bottom-side inclined portion 47 of the first side wall 42 are formed in anticipation of the expansion of the electrode assembly 12, and the length of the bottom-side inclined portion 47 in the accommodation direction is an opening. It is set smaller than the length of the side inclined portion 46 in the accommodation direction. As a result, the inclination of the opening-side inclined portion 46 that becomes the joining side of the case main body 35 and the lid body 37 is smaller than the inclination of the bottom-side inclined portion 47. For this reason, the stress which acts on the junction part of the case main body 35 and the cover body 37 at the time of expansion | swelling of the electrode assembly 12 can be suppressed, and the fracture | rupture in the junction part at the time of expansion | swelling can be prevented. Even if the inclination of the bottom side inclined portion 47 is larger than the inclination of the opening side inclined portion 46, there is no joined portion, so that a stress larger than the stress acting on the joined portion acts on the vicinity of the bottom inclined portion 47 during expansion. However, the vicinity of the bottom inclined portion 47 does not break. In addition, since the space near the bottom inclined portion 47 in the battery case 11 can be reduced, an increase in excess space in the battery case 11 can be suppressed. Further, even when a storage space for the accessory parts of the electrode assembly 12 is required in the vicinity of the opening 36 side of the battery case 11, the space portion on the opening side inclined portion 46 side is on the bottom side inclined portion 47 side. It can be larger than the space. For this reason, an accommodation space can be provided in the space near the opening-side inclined portion 46.

(3) In the electrode assembly 12, a plurality of positive electrodes 13 and a plurality of negative electrodes 14 are alternately stacked while maintaining an insulating state, and the end of the positive electrode 13 and the negative electrode 14 are formed on the opening 36 side and the bottom wall 41 side. The laminated electrode assembly is formed with respective end portions. The space part on the opening side inclined part 46 side in the battery case 11 can be made larger than the space part on the bottom side inclined part 47 side, and an electrode (positive electrode 13 and negative electrode 14) or an electrode attachment member is provided on the opening 36 side. Space formation suitable for a laminated electrode assembly provided with (a current collector, a current collector plate, etc.) can be realized.

(4) The length of the opening-side inclined portion 46 in the accommodation direction is set based on the position of the end portion on the opening 36 side of the positive electrode 13 of the electrode assembly 12 accommodated in the case body 35. The length of the bottom inclined portion 47 in the accommodation direction is set based on the position of the end of the electrode assembly 12 on the bottom wall 41 side of the positive electrode 13. For this reason, on the end surface of the electrode assembly 12 in the stacking direction, the portion where the positive electrode 13 and the negative electrode 14 overlap each other and the intermediate portion 48 are brought into contact with each other, and the intermediate portion 48 is not brought into contact with the portion where the positive electrode 13 and the negative electrode 14 do not overlap each other. Can be. Thereby, a more uniform surface pressure can be applied from the intermediate portion 48 of the first side wall 42 to the expanding portion of the electrode assembly 12.

(5) The bottom inclined portion 47 is set based on the position of the end of the electrode assembly 12 on the bottom wall 41 side of the positive electrode 13. For this reason, when the electrode assembly 12 is accommodated in the case main body 35, the end of the negative electrode 14 of the electrode assembly 12 abuts against the bottom wall 41, so that the positive electrode 13 and the negative electrode 14 in the electrode assembly 12 overlap each other. The part can be reliably positioned at the intermediate part 48.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the invention. For example, the following modifications may be made.

In the above embodiment, the multilayer electrode assembly as the electrode assembly has been described as an example, but the electrode assembly is not limited to the multilayer electrode assembly. The electrode assembly may be a wound electrode assembly that is formed in layers by being wound while the plurality of positive electrodes and the plurality of negative electrodes are maintained in an insulating state. When the electrode assembly is a wound electrode assembly, the electrode assembly may be a flat wound electrode assembly so that an end surface in the stacking direction with which the middle portion of the case body can contact is formed on the electrode assembly. That's fine. In this case, similarly to the above-described embodiment, the intermediate portion of the first side wall can apply a uniform surface pressure to the end surface in the stacking direction of the wound electrode assembly.
In the above embodiment, the bottom inclined portion is set based on the position of the end of the electrode assembly on the bottom wall side of the positive electrode, but this is not restrictive. For example, the bottom-side inclined portion may be set without using the position of the end portion on the bottom wall side of the positive electrode as a reference, and at least the length of the bottom-side inclined portion in the accommodation direction is set smaller than the opening-side inclined portion. If so, it can be set freely. In this case, it is preferable to set so that the part where the positive electrode and the negative electrode overlap each other in the electrode assembly is easily subjected to uniform surface pressure from the intermediate part.
In the above embodiment, the preformed body of the case body of the battery case is molded, and hydroforming (bulge molding) is performed on the preformed body, whereby the opening side inclined portion and the bottom side are formed on the first side wall. Although the inclined part and the intermediate part are formed, this is not restrictive. The case body may be manufactured by a method other than hydroforming.
In the above embodiment, the opening-side inclined portion and the bottom-side inclined portion in the case main body are linearly inclined as viewed from the cross section, but this is not restrictive. For example, like the secondary battery according to the modification shown in FIG. 6, the opening-side inclined portion 51 and the bottom-side inclined portion 52 in the case main body 35 may have a shape inclined in a curve as viewed from the cross section. The secondary battery according to the modification has the same effects as the embodiment.
In the above embodiment, the lithium secondary battery is illustrated as an example of the power storage device, but this is not restrictive. The power storage device may be applied to a primary battery other than a secondary battery other than a lithium secondary battery.

DESCRIPTION OF SYMBOLS 10 Secondary battery 11 Battery case 12 Electrode assembly 13 Positive electrode 14 Negative electrode 23 Separator 30 Positive electrode terminal 31 Negative electrode terminal 35 Case main body 36 Opening 37 Cover body 40 Cylindrical wall 41 Bottom wall 42 First side wall 43 Second side wall 44 Opening side end Portions 46, 51 Opening side inclined portions 47, 52 Bottom side inclined portion 48 Intermediate portion 49 Through hole M Mold P Preliminary body

Claims (4)

A layered electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked or wound while maintaining an insulating state;
A battery case for housing the electrode assembly,
The battery case includes a bottomed cylindrical case main body having an opening, and a lid joined to an opening side end formed on the opening side of the case main body,
The case body includes a cylindrical wall having a rectangular cross section provided with the opening side end, and a bottom wall provided at an end opposite to the opening side end of the cylindrical wall,
The cylindrical walls are in contact with end faces in the stacking direction of the electrode assembly, and are arranged in parallel to each other so as to be orthogonal to the pair of first side walls and the pair of first side walls. A power storage device comprising a pair of second side walls,
The first sidewall is
An opening-side inclined portion formed on the opening side, a bottom-side inclined portion formed on the bottom wall side, and an intermediate portion formed between the opening-side inclined portion and the bottom-side inclined portion,
The opening-side inclined portion is formed so as to be inclined with respect to the accommodation direction of the electrode assembly so as to narrow the interval between the pair of first side walls from the opening side toward the bottom wall side.
The bottom-side inclined portion is formed to be inclined with respect to the accommodation direction of the electrode assembly so as to narrow the interval between the pair of first side walls from the bottom wall side toward the opening side.
The intermediate portion is formed so as to make the interval between the pair of first side walls constant,
An end face in the stacking direction of the electrode assembly is in contact with the intermediate portion.   The power storage device according to claim 1, wherein a length of the bottom inclined portion in the accommodation direction is set smaller than a length of the opening inclined portion in the accommodation direction. The electrode assembly includes:
The plurality of positive electrodes and the plurality of negative electrodes are alternately stacked while maintaining an insulating state,
3. The power storage device according to claim 1, wherein the power storage device is a multilayer electrode assembly in which an end portion of the positive electrode and an end portion of the negative electrode are formed on the opening side and the bottom wall side, respectively. The length in the accommodating direction of the opening-side inclined portion is set based on the position of the end portion on the opening side of the positive electrode of the electrode assembly accommodated in the case body,
The length in the accommodation direction of the bottom inclined portion is set based on the position of the end portion on the bottom wall side of the positive electrode of the electrode assembly accommodated in the case body. The power storage device according to claim 3.

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