A lithium secondary battery having high capacity and good charge-discharge cycle performance is provided. The lithium secondary battery includes a negative electrode (2) containing silicon as a negative electrode active material, a positive electrode (1) containing a positive electrode active material, and a non-aqueous electrolyte. The positive electrode active material is a lithium-transition metal composite oxide including a layered structure represented by the chemical formula Li.sub.aNi.sub.xMn.sub.yCo.sub.zO.sub.2, where a, x, y, and z satisfy the expressions: 0.ltoreq.a.ltoreq.1.3, x+y+z=1, 0