Capacitance Enhancement of Activated Carbon through Mechanical Activation for Li-Ion Capacitors

Lithium ion capacitors (LICs) have the potential to combine the high energy density of lithium ion batteries and the high power density of supercapacitors into one device. In this study, the feasibility of surface functionalization of activated carbon (AC) powder via mechanical activation to serve as the cathode for LICs with non-aqueous electrolytes is investigated. It is found that mechanical activation through high-energy ball milling can impart pseudocapacitance to the AC powder. Although ball milling has reduced the specific surface area, the specific capacitance of the AC powder has increased by 100% because the capacitance per surface area has increased by 3,000%. The capacitance enhancement is mainly attributed to the pseudo-capacitive redox reaction on the C=O sites introduced by mechanical activation.