Atomic batteries use energy given off by radioactive decay or controlled tightly fission reactions to provide energy. Typically, these devices use advanced metamaterials to directly convert charged particles and thermal energy into electrical current. The drawback to atomic batteries is that they cannot be turned off and will radiate considerably more heat of the excess electrical energy is not utilized. In the case of atomic batteries utilizing controlled fission reactions, those reactions can often be accelerated to provide more energy as needed and retarded when the energy is not needed, but will still produce some energy when not in use that must be accounted for.
A common form of atomic battery are betavoltaic cells.