ELECTROCHEMICAL SUPERCAPACITOR ELECTRODES FROM SPONGE LIKE GRAPHENE NANOARCHITECTURES WITH ULTRAHIGH POWER DENSITY

摘要

With increasing power requirements for electric/hybrid vehicles and power back up, supercapacitors have attracted much attention recently due to their ability to supply much higher power density as compared to batteries.Graphene and carbon nanotubes (CNTs) are considered as promising materials for the next generation supercapacitors due to their high specific surface area, excellent electrical conductivity and high chemical and thermal stability. Graphene-based electrode materials have been investigated for the application of supercapacitors in aqueous, organic and ionic liquid electrolyte.1'9'10 However due to the strong van der Waals force between neighboring layers, graphene readily packs and forms aggregated structures. This greatly limits electrolyte transfer and ion accessibility, especially in ionic liquids that are more viscious. This in turn severely limits the rate capability of the electrodes, forcing them to operate in effect as "mediocre batteries". New materials, such as laser-scribed graphene, curved graphene and solvated stacking-free graphene have been created to solve this problem. One of the promising solutions is to synthesize graphene with three-dimensional (3D) structure. Theoretical calculations show that a 3D graphene-CNT network is an ideal structure for high power applications due to the presence of fast electrolyte transfer channels. Following this theoretical work, graphene with 3D structure has been successfully synthesized via chemical vapor deposition, hydrothermal method, and a "breath-figure" technique.