NOVELTY - A nonaqueous electrolytic secondary battery comprises a flat-shaped electrode assembly (4) having positive electrode plate including lithium transition metal complex oxide as a positive electrode active material, and a negative electrode plate including a negative electrode active material to and from which lithium ions may be introduced and extracted, a nonaqueous electrolyte, a rectangular outer housing (12) provided on electrode assembly and the nonaqueous electrolyte and having tubular shape with a bottom and opening and a sealing plate which seals the opening.    USE - Nonaqueous electrolytic secondary battery is used for driving power supply for plug-in hybrid electric vehicle, hybrid electric vehicle and electric vehicle.    ADVANTAGE - The nonaqueous electrolytic secondary battery has low resistance and excellent high-temperature storage characteristics and power characteristics. The nonaqueous electrolyte has high capacity maintenance ratio after high-temperature storage.    DETAILED DESCRIPTION - A nonaqueous electrolytic secondary battery comprises a flat-shaped electrode assembly having positive electrode plate including lithium transition metal complex oxide as a positive electrode active material, and a negative electrode plate including a negative electrode active material to and from which lithium ions may be introduced and extracted, a nonaqueous electrolyte, a rectangular outer housing provided on electrode assembly and the nonaqueous electrolyte and having tubular shape with a bottom and opening and a sealing plate which seals the opening. The nonaqueous electrolyte includes lithium fluorosulfonic acid. The rectangular outer housing comprises a pair of large-area side walls (12a) and a pair of small-area side walls (12b) having area smaller than the large-area side wall. The value of a number of layers of the positive electrode plate in the electrode assembly placed between the pair of the large-area side walls with respect to a distance between the pair of the large-area side walls is 5 layers/mm or more.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the nonaqueous electrolytic secondary battery.    Flat-shaped electrode assembly (4)    Positive electrode electricity collector (5)    Rectangular outer housing (12)    Large-area side walls (12a)    Small-area side walls (12b)