NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

The purpose of the present invention is to impart an irreversible capacity to a negative electrode active material at a low charging voltage level. A nonaqueous electrolyte secondary battery of the present invention comprises a positive electrode containing a positive electrode active material, a negative electrode, and a nonaqueous electrolyte. The positive electrode active material includes: a first positive electrode active material having an initial charge capacity of 180 mAh/g or less and an initial charging and discharging efficiency of 70 % or more when a positive electrode voltage level is charged from 3.0 V (vs. Li/Li+) up to 4.3 V (vs. Li/Li+) using lithium metal as a negative electrode; and a second positive electrode active material having an initial charge capacity exceeding 180 mAh/g and an initial charging and discharging efficiency of less than 70 % when a positive electrode voltage level is charged from 3.0 V (vs. Li/Li+) up to 4.3 V (vs. Li/Li+) using lithium metal as the negative electrode.