Patent ID: 8318347

Claim:
A lithium ion secondary battery including a flat-plate electrode assembly in which a positive electrode, a separator, and a negative electrode are stacked in the thickness direction of the flat-plate electrode assembly; and a non-aqueous electrolyte, wherein: the positive electrode and the negative electrode each include an active material layer capable of absorbing and desorbing lithium and a current collector, said current collector includes: a substantially rectangular current collector body on the surface of which the active material layer is formed, and said current collector body being present in the flat-plate electrode assembly; a heat radiating portion that extends from a portion or all of two or three adjacent sides of the current collector body toward the outside of the flat-plate electrode assembly; and a lead portion, the heat radiating portion has an L-shape or an angular U-shape, and extends outwardly from the flat-plate electrode assembly, a plane of projection of the heat radiating portion of the positive electrode current collector does not overlap with a plane of projection of the heat radiating portion of the negative electrode current collector, the lead portion is joined to or formed integrally with the heat radiating portion along a periphery of the heat radiating portion, the lead portion extends from the periphery of the heat radiating portion, the lead portion is drawn out to the outside of the lithium ion secondary battery, and the lead portion has an L-shape or an angular U-shape.