Asymmetric supercapacitor based on activated expanded graphite and pinecone tree activated carbon with excellent stability

This work presents results obtained from the production of low-cost carbons from expanded graphite (EG) and pinecone (PC) biomass, activated in potassium hydroxide (KOH) and finally carbonized in argon and hydrogen atmosphere. A specific surface area of 808 m2 g−1 and 457 m2 g−1 were measured for activated pinecone carbon (APC) and activated expanded graphite (AEG), respectively. The electrochemical characterization of the novel materials in a 2-electrode configuration as supercapacitor electrode shows a specific capacitance of 69 F g−1 at 0.5 A g−1, high energy density of 24.6 W h kg−1 at a power density of 400 W kg−1. This asymmetric supercapacitor also exhibits outstanding stability after voltage holding at the maximum voltage for 110 h, suggesting that the asymmetric device based on different carbon materials has a huge capacity for a high-performance electrode in electrochemical applications.