LITHIUM SECONDARY BATTERY

摘要

PURPOSE: To provide a lithium secondary battery in which a positive electrode active material hardly decomposes even if high voltage continuous charging is erroneously performed and internal resistance of the battery hardly increases and which has extremely high reliability. CONSTITUTION: A lithium secondary battery is provided with a negative electrode using lithium as an active material, a positive electrode using a baron containing lithium-manganese composite oxide as an active material and nonaqueous electrolyte composed of salute and solvent. In the boron containing lithium-manganese composite oxide, the atomic ratio (B/Mn) of B to Mn is 0.01 to 0.20, and an average valence of manganese before charge-discharge is not less than 3.80. The solvent is a mixed solvent containing a butylene carbonate by 5 to 50 volume %.