Graphene boosts supercapacitor energy density

The material – called a holey graphene framework – is a 3D perforated structure characterised by tiny holes. This not only increases energy density, say the researchers, but also allows electrochemical capacitors to maintain their high power density. "The 'holey' graphene EC bridges the energy density gap between traditional capacitors and batteries, yet with vastly higher power density," said Professor Xiangfeng Duan, who led the research. "It creates exciting opportunities for mobile power supplies for many applications from cell phones to electric vehicles." Electrochemical capacitors, or supercapacitors, have been limited by low energy density. Whilst they typically have superior power density and cycle life to batteries, their energy density has been at least an order of magnitude less. Leading ECs generally use porous activated carbon electrodes, with energy densities of 4 to 5Whr/kg. However, the CNSI researchers say they have achieved gravimetric energy densities of 127Whr/kg and volumetric energy densities of 90Whr/litre. When fully packaged, the prototype ECs are said to boast energy densities of 35Whr/kg.