Capacitance limits of high surface area activated carbons for double layer capacitors

A large specific surface area (SSA) of carbon materials used for electrochemical double layer capacitors (EDLC) is the most important parameter leading to a large gravimetric capacitance (Cg). However, for a SSA determined with the differential functional theory (DFT) model above a value of 1200 m2/g the plot of Cg versus SDFT exhibits a plateau. We suggest that this limitation of Cg can be ascribed to a space constriction for charge accommodation inside the pore walls. As a consequence, the use of extremely high surface area carbons for EDLCs may be unprofitable.