Capacitance improvement of supercapacitor active material based on activated carbon fiber working with a Li-ion containing electrolyte

In an attempt to provide a favorable active material of Li+ supercapacitor for HEV use, we modified the surface of an activated carbon fiber felt by coating with some transition metal oxides after mild-oxidation treatment. Major source of enhancing capacitance is attributed to be due to the nano-ionics mechanism proposed by Maier and coworkers.Cyclic voltammetry and constant current charge–discharge performance were examined for the surface modified samples in view of power capability. The oxides of Ag, Cu, Pd, and Sn were found effective to enhance the capacitance and high rate charge/discharge performance. The cycleability test was performed as well.

► Novel method to enhance the capacitance of supercapacitor is proposed.
► The method is to coat the surface of activated carbon fiber with the film of transition metal oxide (Pd, Sn, Ag, Cu).
► Electrochemical evaluation was performed in an organic ester containing LiClO4.
► The evaluation was done with cyclic voltammetry and constant current test.
► The capacitance was enhanced up to three times to that of pristine sample.