Supercapacitors with Composite Fibrous Electrodes

We present an investigation to develop innovative composite fibrous electrodes optimized for a supercapacitor with a “green” low-cost aqueous electrolyte, superconcentrated potassium formate, which raises the maximum energy storage device voltage beyond the water electrolysis limit. Three types of electrospun nanofiber mats are investigated for optimum pseudocapacitance with this electrolyte: polyaniline (PANI)/polyacrylonitrile (PAN) fibers, without or with 1 wt% or 10 wt% graphene nanoplatelets (GNP). These nanofiber mats are considered as standalone electrodes or in bilayer formations with a phenolic-derived activated carbon fabric. Supercapacitor cells with these electrodes are tested electrochemically via electrical impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge at different current densities. The supercapacitor with hybrid electrode bilayers of activated carbon fabric and electrospun fiber mat consisting of PANI:PAN at 50:50 w/w with 10 wt% GNP exhibited the best performance with an energy and a power density of 39 Wh/kg and 6057 W/kg of electrodes, respectively.