Secondary battery with improved joining between wound electrode body and electrode terminal
Better joining between a wound electrode body and an electrode terminal is implemented. In a cross section orthogonal to a winding axis of a wound electrode body of the secondary battery herein disclosed, two separators respectively extend more inward of the wound electrode body than electrode sheets. A portion of one separator forming an innermost circumference of the wound electrode body is bound in a first curved part. An inner circumferential side end of the one separator is between a junction part of an electrode sheet and an electrode terminal, and a first top around the winding axis. A portion of the other separator forming the innermost circumference is bent in a second curved part, and the inner circumferential side end of the other separator is between the junction part and a second top around the winding axis.
1 . A secondary battery, comprising:
a battery case in which an accommodation space in a flat rectangular parallelepiped shape is formed;
a wound electrode body accommodated in the battery case; and
a first electrode terminal and a second electrode terminal connected with the battery case and the wound electrode body,
wherein
the wound electrode body has a band-shaped first separator, a band-shaped first electrode sheet, a band-shaped second separator, and a band-shaped second electrode sheet, and is accommodated in the accommodation space of the battery case in such a manner that,
the first separator, the first electrode sheet, the second separator, and the second electrode sheet are made uniform in length direction, are sequentially stacked one on another, and are wound around a winding axis set in a width direction of the first electrode sheet, and
a cross section orthogonal to the winding axis is formed into a shape having a rectangular part, and a first curved part and a second curved part sandwiching the rectangular part,
the first electrode sheet partially protrudes from the first separator and the second separator on a first side along the winding axis, and is bound along a direction orthogonal to the winding axis to be joined with the first electrode terminal,
the second electrode sheet partially protrudes from the first separator and the second separator on a second side along the winding axis, and is bound along the direction orthogonal to the winding axis to be joined with the second electrode terminal,
in the cross section orthogonal to the winding axis,
in an inner circumferential region of the wound electrode body, the first separator and the second separator extend more inward of the wound electrode body than the first electrode sheet and the second electrode sheet, respectively,
a portion of the first separator forming an innermost circumference of the wound electrode body is bent in the first curved part, and an inner circumferential side end of the first separator is arranged between a first junction part at which the first electrode sheet and the first electrode terminal are joined with each other, and a first top of the first curved part around the winding axis of the wound electrode body, and
a portion of the second separator forming the innermost circumference of the wound electrode body is bent in the second curved part, and an inner circumferential side end of the second separator is arranged between a second junction part at which the second electrode sheet and the second electrode terminal are joined with each other, and a second top of the second curved part around the winding axis of the wound electrode body,
the battery case includes a bottom surface, and an opposite surface to the bottom surface,
the first curved part is arranged between a center of the wound electrode body and the opposite surface,
the second curved part is arranged between the center of the wound electrode body and the bottom surface of the battery case,
the first junction part and the second junction part are arranged in the rectangular part,
the inner circumferential side end of the first separator is arranged between the opposite surface and the first junction part, and
the inner circumferential side end of the second separator is arranged between the bottom surface of the battery case and the second junction part.
2 . The secondary battery according to claim 1 , wherein
the inner circumferential side end of the first separator and the inner circumferential side end of the second separator are not attached to each other.
3 . The secondary battery according to claim 1 , wherein
the inner circumferential side end of the first separator and the inner circumferential side end of the second separator are arranged in the rectangular part.
4 . The secondary battery according to claim 1 , wherein
the inner circumferential side end of the first separator is arranged in the first curved part.
5 . The secondary battery according to claim 2 , wherein
in the inner circumferential region, the inner circumferential side end of the first separator and the inner circumferential side end of the second separator are arranged at positions point symmetrical with respect to the center of the wound electrode body, and
the center of the wound electrode body is a middle point of a line segment connecting the first top of the first curved part and the second top of the second curved part.
6 . The secondary battery according to claim 4 , wherein
in the inner circumferential region, the inner circumferential side end of the first separator and the inner circumferential side end of the second separator are arranged at positions point symmetrical with respect to the center of the wound electrode body, and
the center of the wound electrode body is a middle point of a line segment connecting the first top of the first curved part and the second top of the second curved part.
7 . The secondary battery according to claim 1 , wherein
the battery case includes
a case main body having the bottom surface and an opening opposite to the bottom surface, and
a lid mounted at the opening of the case main body, wherein the lid configures the opposite surface.