TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The negative electrode has negative electrode active material layer formed on a collector. Preferred Composition: The content of carboxylate ion, halogen and sulfate ion in lithium fluorosulfonate is more than 1x 10-7 mol/L and less than 4x 10-3 mol/L, 1.5x 10-3 mol/kg and less than 2.5x 10-1 mol/kg, respectively. The content of sulfate ion in the nonaqueous electrolyte solution is more than 1x 10-7 mol/L and less than 1x 10-2 mol/L. The content of lithium fluorosulfonate is nonaqueous electrolyte solution is 0.0005-0.5 mol/L. The lithium salt other than lithium fluorosulfonate is hexafluorolithium phosphate and/or tetrafluorolithium borate. The negative electrode active material layer comprises negative electrode active material containing silicon, tin, and/or their alloy, carbonaceous material, and lithium-titanium complex oxide. The positive electrode active material layer comprises lithium-cobalt complex oxide, lithium-cobalt-nickel complex oxide, lithium-manganese complex oxide, lithium-cobalt-manganese complex oxide, lithium-nickel complex oxide, lithium-nickel-manganese complex oxide, and/or lithium-nickel-cobalt-manganese complex oxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The lithium salt is lithium halide or lithium carboxylate. The nonaqueous solvent is aprotic polar organic solvent other than carboxylic acid, preferably linear carbonate ester. The nonaqueous electrolyte solution further contains lithium salt other than lithium fluorosulfonate, nonaqueous solvent, fluorine-containing cyclic carbonate (0.001-85 %mass), carbon-carbon unsaturated bond-containing cyclic carbonate (0.001-10 %mass), cyclic sulfonate ester (0.001-10 %mass), cyano group-containing compound (0.001-10 %mass), diisocyanate compound (0.001-5 %mass) and lithium oxalate salt. Preferred Process: Carboxylic acid produced as byproduct, is removed after manufacture of lithium fluorosulfonate by distillation. Carboxylic acid is removed in presence of a solution containing nonaqueous solvent having boiling point higher than the boiling point of byproduced carboxylic acid. After removing carboxylic acid, the nonaqueous solvent is mixed with solution containing crude fluorosulfonic acid, and solid-liquid-separation process is performed.