ABSTRACT
Electrochemical capacitors (ECs) store electric charges at electrode-
electrolyte interface. The performances of ECs depend greatly on
many factors such as electrode (material derived, pore distribution,
surface functionality, and so on), electrolyte (kind of cation and
anion, solvent), and additives for the electrode and electrolyte,
interfacial conditions between electrode and electrolytic solution,
separator, and so on.1-7 As for the electrodes, activated carbons
(ACs) have been widely used as electrode material because of its
high specific surface area (1000-2000m2/g), immediate availability,
and low cost.8-12 For electrolytes, nonaqueous electrolytes con-
sisting of acetonitrile (AN) or propylene carbonate (PC) solutions
with tetraethylammonium tetrafluoroborate (Et4NBF4) are used
in commercial ECs because they permit wide operating voltage
(2.5-2.7 V).13
