LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which can reduce generation of a short circuit between a cathode and an anode due to deposition of metal on an anode active material layer under high temperature aging environment.SOLUTION: A lithium ion secondary battery comprises a wound electrode body. An anode plate comprises an anode foil and an anode active material layer having respective edges on one side aligned to each other in an axial direction, and an anode peripheral part covering a cathode outermost peripheral part from outside through a separator. The separator has an intervening portion interposed between a cathode active material layer and its counter part; an extension part facing a cathode lead part; and a separator peripheral part interposed between the cathode outermost peripheral part and the anode peripheral part. The intervening portion of the separator includes an adjacent part near along the extension part, and the separator has a less permeable part provided at least at the separator peripheral part in a longitudinal direction of the separator at the extension part and the adjacent part on only one side of the separator.