Design of highly capacitive and durable supercapacitors using activated carbons with different pore structures: Petroleum coke and oil palm

Abstract

Four types of supercapacitors (SCs), assembled by activated carbons (ACs) with different pore structures derived from petroleum coke (CK) and oil palm (OP), are analyzed to investigate the mechanism for improvement of cycle durability and capacitance of 3.0V SCs using 1.0M spiro-(1,10)-bipyrrolidinium tetrafluoroborate (SBPBF4) in acetonitrile. Although there have been many studies about activated carbons, few researches have investigated the relationship between the pore structure and the electrochemical properties using the commercially available activated carbon electrodes. The outstanding performances are determined from a combination of negative OP and positive CK AC electrodes. From analyses of surface area and porosity of ACs, potential and capacitance distributions of both electrodes, and impedance components, the effective idea for designing the superior SC is identified as higher mesopore portion of negative electrode and larger specific surface area of positive electrode than its counter electrode. SCs composed of negative OP AC electrode with higher mesopore portion show stable potential and capacitance of positive and negative electrodes during cycling. These results are derived from alleviation of crack or delamination of active materials and suppressed increments of charge transfer or diffusion resistance, unlike in SCs with negative CK AC electrode having higher micropore portion.