Patent ID: 11923512
Assignee: PRIME PLANET ENERGY & SOLUTIONS, INC.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 0:
1. A secondary battery comprising:
a wound electrode body in which an elongated positive electrode sheet, an elongated negative electrode sheet, and an elongated separator interposed between the positive electrode sheet and the negative electrode sheet are superimposed and wound around a winding axis; and
a rectangular battery case that houses the wound electrode body, wherein
the wound electrode body having a first flat surface, a second flat surface, a third flat surface, and a fourth flat surface positioned on outer peripheral surfaces around the winding axis,
the first flat surface and the second flat surface facing each other with the winding axis interposed therebetween,
the third flat surface and the fourth flat surface being disposed between the first flat surface and the second flat surface and facing each other with the winding axis interposed therebetween,
the wound electrode body has
a first rounded part disposed between the first flat surface and the third flat surface,
a second rounded part disposed between the first flat surface and the fourth flat surface,
a third rounded part disposed between the second flat surface and the third flat surface, and
a fourth rounded part disposed between the second flat surface and the fourth flat surface,

inner voids are formed at gaps in a portion, where the positive electrode sheet, the negative electrode sheet, and the separator are superimposed, inside each of the first rounded part, the second rounded part, the third rounded part, and the fourth rounded part,
at least the first flat surface and the third flat surface are in contact with inner peripheral surfaces of the battery case,
an exterior void is formed between the first rounded part and an inner peripheral surface of the battery case,
one or a plurality of the inner voids are formed inside the first rounded part, and
the exterior void is larger than one of the inner voids.