NOVELTY - A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator provided between the positive and negative electrodes, a polymeric layer arranged between the separator and positive electrode or negative electrode, and an exterior component (30) in which the positive electrode, the negative electrode, the separator and the polymeric layer are accommodated. The polymeric layer holds a non-aqueous electrolytic solution comprising 13-25 %mass electrolyte salt. The separator has thickness of 5-20 mu m, and comprises 90 %mass or more polyethylene.    USE - Nonaqueous electrolyte secondary battery is used for camcorder, cellular phone and portable computer.    ADVANTAGE - The nonaqueous electrolyte secondary battery has high energy density, and excellent heat resistance, liquid-holding property and cycle characteristics. Since the usage amount of nonaqueous electrolytic solution is small, the resistance to liquid leakage is improved. By making the mixing ratio of polyethylene and polypropylene fall within a preset range, the start temperature of heat shrinkage can be increased while keeping the shutdown function-revealing temperature low, thus preventing thermal runaway.    DETAILED DESCRIPTION - A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator provided between the positive and negative electrodes, a polymeric layer arranged between the separator and positive electrode or negative electrode, and an exterior component in which the positive electrode, the negative electrode, the separator and the polymeric layer are accommodated. The battery has maximum attained temperature of 100 degrees C or less using a nail piercing safety test, while conducting the safety test. The polymeric layer holds a non-aqueous electrolytic solution comprising 13-25 %mass electrolyte salt. The separator has thickness of 5-20 mu m, and comprises 90 %mass or more polyethylene.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of the nonaqueous electrolyte secondary battery.    Positive electrode terminal (11)    Negative electrode terminal (12)    Battery element (20)    Exterior component (30)    Adhesive film (31)