Micro-supercapacitors might be the answer. Power density in some experimental graphene super-capacitor devices is several times that of standard thin-film lithium batteries but volume is a problem: graphene is only one atom thick. A Chinese team, working in China, Singapore and the USA, may have come up with the solution: creating a mesh of carbon nanotubes with interposed doped graphene sheets. They claim more than twice the power density of ordinary batteries and “a long cycle life”. Ah – how long, that is the question.
Nature Nanotechnology, July 2014