A high-input and high-output battery having a large capacity while guaranteeing safety is provided. In a lithium ion battery having an electrode wound group in which a positive electrode, a negative electrode, and a separator are wound and an electrolytic solution provided in a battery container, a discharge capacity of the battery being 30 Ah or more, the positive electrode has a current collector and a positive electrode composite applied to both surfaces of the current collector, and the positive electrode composite has following configuration. The positive electrode composite contains a mixed active material of layered lithium nickel manganese cobalt composite oxide (NMC) and spinel lithium manganese oxide (sp-Mn), a density of the positive electrode composite is 2.4 g/cm3 or more and 2.7 g/cm3 or less, and a porosity of the active electrode composite is 29.5% or more and 40.0% or less. Furthermore, a weight ratio (NMC/sp-Mn) of the mixed active materials is set to 10/90 or more and 60/40 or less.