Non-aqueous electrolyte secondary batteries are provided. In one embodiment, the non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, a polymeric layer disposed between the separator and at least one of the positive electrode and the negative electrode, and an exterior member housing the positive electrode, the negative electrode, the separator, and the polymeric layer. The separator has a thickness of 5 μm to 20 μm and includes at least 90% by mass of polyethylene. The polymeric layer holds therein a non-aqueous electrolytic solution including 13% by mass to 25% by mass of an electrolyte salt. The battery has a maximum attained temperature not higher than 100° C. using a nail piercing safety test at the time of conducting the safety test.