To provide a flat nonaqueous electrolyte secondary battery having a square external shape, of which internal short-circuit when falling down is reduced.
The flat nonaqueous electrolyte secondary battery is composed of: an outer can 1 having a flange part 2 of a square-bottomed cylinder shape projecting outward at an open end thereof, shaped into a folded shape by caulking; a sealing can 3 having a flange part 4 of a square-bottomed cylinder shape projecting outward from an open end thereof, arranged at the open end of the outer can 1 so as to be surrounded by the flange part 2 of the outer can 1; an insulation gasket 5 arranged between the flange part 2 of the outer can 1 and the flange part 4 of the sealing can 3; and an electrode group 6 containing cathodes and anodes, arranged between a bottom inner face of the outer can 1 and a bottom inner face of the sealing can 3. An internal length L2 of the flange part 2 of the outer can 1 is smaller than an internal length L1 of the flange part 4 of the sealing can 3, and a height of the flange part 2 of the outer can 1 is 15% or more and 50% or less of a thickness of the electrode group.
OHASHI HIROBUMI
NAKAJIMA MASAYOSHI
Satoshi Kono
Makoto Nakamura
Kurata Masatoshi
Sadao Muramatsu
Ryo Hashimoto