A nonaqueous electrolyte secondary battery wherein a material capable of
occluding/discharging lithium is used as a negative electrode material
and a lithium-transition metal composite oxide which contains Ni and Mn
as the transition metal and has a layered structure is used as a positive
electrode material is characterized in that a lithium-transition metal
composite oxide having a BET specific surface area less than 3 m.sup.2/g
and a pH of 11.0 or less when 5 g of the lithium-transition metal
composite oxide is immersed in 50 ml of purified water is used as the
positive electrode active material.