Nuclear energy is an almost entirely clean source of energy production, but the University of Bristol has developed a battery to efficiently make use of even the small amount of waste that nuclear reactors produce.
Though nuclear energy simply heats water into steam to power turbines, current nuclear fission reactors produce small amounts of radioactive waste in the form of carbon-14. This waste is small in terms of volume (especially when compared to the total energy output,) however it is also highly radioactive and thus very dangerous.
The University of Bristol's battery can make use of this radioactivity in order to generate energy. It uses a diamond -- which is a carbon structure -- to absorb the radioactivity from carbon-14 and turn it into energy.