SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery with a large capacity.SOLUTION: A lithium ion secondary battery comprises: a first electrode having a first electrode active material; and a second electrode having second and third electrode active materials. The second electrode active material is larger than the first electrode active material in charge-discharge efficiency. The third electrode active material is smaller than the second electrode active material in charge-discharge efficiency. The product of a difference in charge-discharge efficiency between the second and first electrode active materials, and a capacity of the second electrode active material is larger than the product of a difference in charge-discharge efficiency between the first and third electrode active materials, and a capacity of the third electrode active material. The mixing ratio of the second electrode active material to the total of the second and third electrode active materials is smaller than the mixing ratio of the third electrode active material to the total of the second and third electrode active materials.