Self-supporting carbon electrode

A self-supporting supercapacitor electrode adapted for attachment to an electrical circuit comprising a rigid or mechanically resilient, electrically-conductive sheet with the weight being 75 to 90% activated carbon, 5 to 25% conductive carbon and 5 to 15% polymer binder, in which the active and conductive carbon is uniformly dispersed. The surface area of the activated carbon may be in the range from 1500 to 2500m2g-1. The conductive carbon may comprise graphene, single-walled carbon nanotubes or multi-walled carbon nanotubes. The polymer binder may be fluorinated e.g. PTFE and may be conductive. The electrode may comprise a metallised tab for providing electrical connection to an external circuit and have a specific capacitance of greater than 100 Farads per gram. The electrode may be manufactured by mixing the binder with an aqueous solution under conditions of low shear; adding the activated carbon and conductive carbons under conditions of high shear until a dough or slurry is produced; and rolling or calendaring the dough into sheets having a thickness in the range 100 to 350 microns.