LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having a structure which allows the elution of a metal element from a positive electrode active material to be suppressed further reliably.SOLUTION: A lithium ion secondary battery 100 comprises: a flat wound electrode body 80 arranged by laminating a positive electrode 10 of a long length, and a negative electrode 20 having a length longer than the positive electrode with a separator 40 interposed therebetween, and winding them in their longitudinal direction; and a nonaqueous electrolyte 60; and a rectangular parallelepiped case 50 in which the flat wound electrode body and the nonaqueous electrolyte are enclosed. The wound electrode body 80 has an excess part 22 of the negative electrode in a starting end portion 81 of a winding direction located on the side of the center of the winding; the excess part protrudes closer to the center of the winding along the winding direction with respect to the positive electrode. In addition, an excess amount of the nonaqueous electrolyte 60 is present in a gap between the wound electrode body 80 and the rectangular parallelepiped case 50. The excess part 22 of the negative electrode on the side of the starting end portion is disposed in a region where an excess amount of the nonaqueous electrolyte 60 is present on condition that the battery is disposed at a predetermined location in a predetermined posture.