Non-aqueous electrolyte secondary battery

A non-aqueous electrolyte secondary battery obtained by encasing, inside an outer casing formed of a laminate film, a power generating element comprising:

• a positive electrode obtained by forming, on the surface of a positive electrode current collector, a positive electrode active substance layer containing a positive electrode active substance;
• a negative electrode obtained by forming, on the surface of a negative electrode current collector, a negative electrode active substance layer containing a negative electrode active substance;
• and
• a separator, wherein
• the positive electrode active substance contains LiMn2O4 and a lithium-nickel-manganese-cobalt composite oxide, the mixing ratio of the lithium-nickel-manganese-cobalt composite oxide is 30 to 70% by weight relative to the total 100% by weight of LiMn2O4 and the lithium-nickel-manganese-cobalt composite oxide, the ratio of the total amount of LiMn2O4 and the lithium-nickel-manganese-cobalt composite oxide in 100% by weight of whole amount of the positive electrode active substance contained in the positive electrode active substance layer is 50% by weight or more, and the weight per unit area (single surface coating amount) of the negative electrode active substance layer is 7.4 to 9.2 mg/cm2 and the thickness of the positive electrode active substance layer is 2 to 100 μm.