NOVELTY - A nonaqueous electrolyte secondary battery has positive electrode containing lithium-manganese oxyfluoride compound (I) as positive electrode active material, negative electrode, and nonaqueous electrolyte. The nonaqueous electrolyte contains base electrolyte solution and sulfonic acid compound (II). The base electrolyte solution contains compound (a) chosen from cyclic carbonate compound, linear carbonate compound, cyclic ester compound and linear ester compound, and lithium salt chosen from lithium hexafluorophosphate, lithium perchlorate and lithium tetrafluoroborate.    USE - Nonaqueous electrolyte secondary battery for motor vehicle, electric vehicle, mobile telephone and notebook personal computer.    ADVANTAGE - The nonaqueous electrolyte secondary battery has high capacity and excellent cycling characteristics.    DETAILED DESCRIPTION - A nonaqueous electrolyte secondary battery has positive electrode containing lithium-manganese oxyfluoride compound of formula: Li(LixMnyMe'z)OpFq (I) as positive electrode active material, negative electrode, and nonaqueous electrolyte. The nonaqueous electrolyte contains base electrolyte solution and sulfonic acid compound (II). The base electrolyte solution contains compound (a) chosen from cyclic carbonate compound, linear carbonate compound, cyclic ester compound and linear ester compound, and lithium salt chosen from lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, cyclic lithium compound of formula (A), lithium boron compound of formula (B), lithium trifluoromethenesulfonate, lithium 2,2,3,3,4,4,5,5,5-nonafluoro-pentanoate, lithium tris(trifluoromethenesulfonyl)methene and lithium bis(trifluoromethylsulfonyl)imide.    Me'=Co, Ni, Cr, Fe, Al, Ti, Zr or Mg;    x=more than 0.09 to less than 0.3;    y,z=more than 0;    p=more than 1.9 to less than 2.1;    q=0-0.1;    y/(y+z)=0.4-0.8;    x+y+z=1;    (1+x)/(y+z)=more than 1.2;    k=1-5;    R1-R4=1-4C alkyl optionally having ether oxygen or fluorine-containing alkyl;    Z=alkali metal or alkaline-earth metal;and    Y'=1-4C alkylene optionally having ether oxygen or fluorine-containing alkylene.