Lithium Ion Battery

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 X of the battery being 30 Ah or more and less than 100 Ah,

• wherein the positive electrode has a current collector and a positive electrode composite applied to both surfaces of the current collector,
• 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 an application quantity of the positive electrode composite is 175 g/m2 or more and 250 g/m2 or less, and
• the discharge capacity X and a weight ratio Y (NMC/sp-Mn) between the layered lithium nickel manganese cobalt composite oxide (NMC) and the spinel lithium manganese oxide (sp-Mn) satisfy a following relational expression 1:
• Y<−0.0062X+1.05(30≦X<100) (relational expression 1).