A battery is provided. The battery includes a positive electrode; a negative electrode; a separator between the positive and negative electrodes; a polymeric layer between the separator and one or both of the positive electrode and the negative electrode, the polymeric layer including an electrolytic solution comprising 13% by mass to 25% by mass of an electrolyte salt; and an exterior member housing the positive electrode, the negative electrode, the separator, and the polymeric layer, wherein the battery has a maximum attained temperature not higher than 100° C. based on a nail piercing safety test.