Nonaqueous electrolyte secondary battery, nonaqueous electrolyte, and charging method therefor

Abstract

A nonaqueous electrolyte secondary battery of the invention has a positive electrode having a positive electrode active material, a negative electrode, and a nonaqueous electrolyte having electrolyte salt in a nonaqueous solvent. The electric potential of the positive electrode active material is 4.4 to 4.6 V relative to lithium, and the nonaqueous electrolyte contains a compound expressed by structural formula (I) below. The quantity of compound added is preferably 0.1% to 2% by mass. Also, the positive electrode active material preferably comprises a mixture of a lithium-cobalt composite oxide which is LiCoO2 containing at least both zirconium and magnesium and a lithium-manganese-nickel composite oxide that has a layer structure and contains at least both manganese and nickel. Thanks to such structure, a nonaqueous electrolyte secondary battery can be provided that is charged to charging termination potential of 4.4 to 4.6 V relative to lithium and that has enhanced overcharging safety. [Chemical Formula 1]

Dependencies are inferred from the claim text.