Fabrication of high voltage and energy dense supercapacitor with Manilkara zapota seeds derived porous activated carbon in acidic electrolyte

Abstract

Achieving a high working potential window beyond the water electrolysis limit (>1.23 V) has always been a big challenge in the fabrication of aqueous supercapacitors (SCs). Since energy density has quadratic dependence on voltage, broadening of cell voltage can remarkably increase the energy density of the capacitor. Unfortunately, most of the aqueous electrochemical capacitors operated in strongly acidic or alkaline electrolytes show poor energy densities owing to their narrow operating voltage limit. To obtain a high voltage range of aqueous symmetric carbon/carbon capacitors and achieve high energy density, the chemistry of electrode materials and the electrochemical kinetics of electrolytes play a critical role. Hence, in the present work, we explore a porous activated carbon produced from the seeds of Manilkara zapota (ACMZ-700) in combination with sulfuric acid electrolyte to obtain an encouraging electrochemical stable working voltage window. Thus, the resulting symmetric SC effectively exhibited an enlarged cell voltage of 1.5 V in an acidic medium. Importantly, due to the positive role of oxygenated surface functional groups of the ACMZ-700 active material, the fabricated symmetric cell delivered an attractive specific capacitance of 334 F g−1 @ 1 A/g. As a result of high capacitance and broader working voltage, the symmetric device delivered an excellent energy density of 26 Wh kg−1 at a power density of 748 W kg−1 and held excellent cycling stability over 10,000 charge/discharge cycles.