NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

Provided is a nonaqueous electrolyte secondary battery with excellent low-temperature performance. The nonaqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes, as a positive electrode active material, a lithium transition metal composite oxide including at least lithium, nickel, manganese, cobalt, and tungsten. The nonaqueous electrolytic solution includes lithium fluorosulfonate and LiPF 6 . The concentration of LiPF 6 in the nonaqueous electrolytic solution is 1.11 mol/L or more. The viscosity of the nonaqueous electrolytic solution at 25°C is 3.1 cP or more. The separator includes a resin layer and an inorganic layer formed on a surface of the resin layer that faces the positive electrode. Where a porosity of the inorganic layer is denoted by ±, a porosity of the resin layer is denoted by ², and a porosity of the positive electrode active material layer is denoted by ³, relationships of 0.6 ‰¤ (²/±) ‰¤ 0.9 and 0.6 ‰¤ (³/±) ‰¤ 0.9 are fulfilled.