This application relates to the field of energy storage technologies, and provides a battery, an apparatus, a preparation method of battery, and a preparation apparatus of battery. The battery includes a first battery cell and a second battery cell. The first battery cell includes a first pressure relief mechanism, the second battery cell includes a second pressure relief mechanism, an energy density of the first battery cell is greater than an energy density of the second battery cell, and an area of the first pressure relief mechanism is greater than an area of the second pressure relief mechanism. The apparatus includes the foregoing battery.