LITHIUM ION SECONDARY BATTERY AND PRODUCTION METHOD FOR SAME

A lithium ion secondary battery (10) includes: an electrode assembly (30) including a positive electrode plate (14), a negative electrode plate (18), and a separator (15), and wound into a flat shape; and an elastic member (21) having porosity and incorporated inside the outermost of the electrode assembly (30) and into a corner portion (31) of the electrode assembly (30) in the winding direction. The elastic member (21) is formed of a foam of at least one material selected from the group consisting of polyethylene, polypropylene, and polyurethane, for example.