| abstract |
[PROBLEMS] To improve charge / discharge cycle characteristics in a lithium secondary battery using a boron-containing lithium-manganese composite oxide as a positive electrode active material of a positive electrode. SOLUTION: In a lithium secondary battery including a positive electrode 1 using a boron-containing lithium-manganese composite oxide as a positive electrode active material, a negative electrode 2, and a nonaqueous electrolyte containing a solute and a solvent, a lithium-containing lithium-manganese composite oxide is used. The atomic ratio of B to Mn in the manganese composite oxide is 0.01 to In the range of 0.20, the average valence of Mn before charging is 3.80 or more, and the solute of the nonaqueous electrolyte is selected from lithium trifluoromethanesulfonimide, lithium pentafluoroethanesulfonimide, and lithium trifluoromethanesulfonate methide At least one solvent is a solvent, at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone and sulfolane, and 1,2-dimethoxyethane, 1,2-diethoxyethane, A mixed solvent containing at least one selected from 2-ethoxymethoxyethane, tetrahydrofuran, dioxolan, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate was used. |