High performance quasi-solid-state supercapacitor based on activated carbon derived from asparagus waste
Niyaz Ahmad, Alessia Rinaldi, Michele Sidoli, Giacomo Magnani, Alberto Morenghi, Silvio Scaravonati, Vincenzo Vezzoni, Lorenzo Pasetti, Laura Fornasini, Francesca Ridi, Chiara Milanese, Mauro Riccò, Daniele Pontiroli
Abstract
Supercapacitors with carbon electrodes derived from biomass and utilizing gel polymer electrolytes are currently a focal point in the development of highly efficient, environmentally friendly, and cost-effective energy storage devices. In this study, we present porous activated carbon derived from asparagus waste, prepared through chemical activation with ZnCl 2 followed by physical activation with CO 2 , as a high-performance electrode material for supercapacitors. The performance of electrodes has been discussed in comparison with supercapacitors employing both gel polymer electrolytes and conventional liquid electrolytes i.e. 7 M KOH. The flexible film of the gel polymer electrolyte exhibits noteworthy characteristics, including a high ionic conductivity of ∼6.3 mS cm −1 , and a high electrochemical stability window of ∼4.5 V. Supercapacitors prepared with this gel polymer electrolyte outperform supercapacitors with liquid electrolytes thanks to a broader electrochemical stability window, showing optimal charge-discharge performance, a specific capacitance of 160 F g −1 , a specific energy of 31 Wh kg −1 , and an effective power of 0.56 kW kg −1 . The superior rate performance is demonstrated by powering a LED for a substantial duration, highlighting the exceptional capabilities of the system. Additionally, the supercapacitor employing the gel polymer electrolyte displays an extended stability, sustaining approximately 10,000 charge-discharge cycles with only a modest initial fading of ∼16 % in specific capacitance and maintaining a high coulombic efficiency of ∼100 %. • Supercapacitors derived from asparagus waste and with ionic liquid-based gel polymer electrolytes have been developed. • Optimized activation of biomass waste has been obtained by combining chemical and physical processes. • Up to 4.5 V stability window of gel polymer electrolytes allowed to reach 31 Wh kg −1 specific energy.