In one aspect, a battery comprises a battery main body, a protective jacket that surrounds the battery main body, and a cooling medium disposed between the protective jacket and the battery main body. In another aspect, a battery comprises a battery main body, a protective jacket that surrounds and connects to the battery main body, and a cooling medium disposed between the protective jacket and the battery main body. The cooling medium has a specific heat capacity of about 1-5 kJ kg−1K−1. In yet another aspect, a method for preparing a battery comprises providing a protective jacket, placing a battery main body in the protective jacket, and disposing a cooling medium between the protective jacket and the battery main body.