Non-aqueous electrolyte secondary battery

A lithium ion secondary battery, which comprises a positive electrode comprising a positive electrode active material, a negative electrode, and a non-aqueous electrolyte solution, wherein

• the non-aqueous electrolyte solution comprises LiPF6 and a lithium imide salt as an electrolyte, and comprises a carbonate-based solvent as a solvent,
• the lithium ion second battery comprises or does not comprise a surplus electrolyte solution,
• the ratio of the positive electrode capacity to the negative electrode capacity is less than 1,
• the nominal voltage is less than 3.6 V, and
• the total content of LiPF6 and lithium imide salt comprised in the non-aqueous electrolyte solution per unit battery capacity and the ratio of the positive electrode capacity to the negative electrode capacity satisfies the following formula:
• Total
• ⁢
• content
• ⁢
• of
• ⁢
• LiPF
• 6
• ⁢
• and
• ⁢
• lithium
• ⁢
• imide
• ⁢
• salt
• ⁢
• per
• ⁢
• unit
• ⁢
• battery
• ⁢
• capacity
• ≧
• 16.5
• ×
• Ratio
• ⁢
• of
• ⁢
• the
• ⁢
• positive
• ⁢
• electrode
• ⁢
• capacity
• ⁢
• to
• ⁢
• the
• ⁢
• negative
• ⁢
• electrode
• ⁢
• capacity
• -
• 9.2
• .