It is an object of this exemplary embodiment to provide a lithium ion battery using a lithium manganese complex oxide, in which the dissolution of manganese and resistance increase are inhibited, and which is excellent in life characteristics at high temperature. One aspect of this exemplary embodiment is a lithium ion battery comprising at least a positive electrode comprising a positive electrode active material, and an electrolytic solution, wherein the positive electrode active material is a lithium manganese complex oxide, the positive electrode comprises a bismuth oxide, and a metal compound attached to part of a surface of the lithium manganese complex oxide, and a dissolution rate of a metal of the metal compound in the electrolytic solution is lower than a dissolution rate of manganese of the lithium manganese complex oxide.