Asymmetric carbon supercapacitor with activated expanded graphite as cathode and Pinecone tree activated carbon as anode materials

This work presents low-cost production of carbon from KOH activation and carbonization of expanded graphite (EG) and Pinecone biomass (PC). A specific surface area (SSA) of 808 m(2) g(-1) and 457 m(2) g(-1) were measured for pinecone-based activated carbon (PAC) and activated expanded graphite (AEG) samples, respectively. The electrochemical characterization of the carbon materials as electrodes in asymmetric 2-electrode device exhibited a high specific capacitance of 277 F g(-1) at 0.5 A g(-1) with an energy density of 24.6 Wh kg(-1) for a corresponding power density of 400 W kg(-1). This asymmetric supercapacitor also demonstrated excellent stability after floating for 110 h in gel polymer electrolyte. These results suggest that asymmetric device based on different carbon materials has great potential for improved performance in energy storage applications.