Pre-treated biomass waste melon peels for high energy density semi solid-state supercapacitors
Niyaz Ahmad, Alessia Rinaldi, Michele Sidoli, Giacomo Magnani, Vincenzo Vezzoni, Silvio Scaravonati, Lorenzo Pasetti, Laura Fornasini, Harsh Gupta, Michele Tamagnone, Francesca Ridi, Chiara Milanese, Mauro Riccò, Daniele Pontiroli
Abstract
Semi-solid-state supercapacitors employing highly porous activated carbon (AC) electrodes are promising, cost-effective, and environmentally friendly energy storage devices with exceptional power performance. In this work, for the first time in literature, we report a comparative study on different pre-treatments made on melon waste starting precursor to produce hierarchical large surface area porous AC. Also, for the first time in our knowledge, a gel polymer electrolyte (GPE) consisting in lithium trifluoromethanesulfonate in ethylmethylimidazolium trifluoromethanesulfonate, with a high ionic conductivity (∼3.3 × 10 −3 S cm −1 ) and a working voltage window of ∼3.9 V vs Ag/Ag + , was used. The supercapacitors were electrochemically characterized with electrochemical impedance spectroscopy , cyclic voltammetry , and galvanostatic charge-discharge tests. The working voltage window of the device was optimized in the range of 0–2.3V. Hydrothermally pre-treated AC-based supercapacitor is characterized by the best performance in terms of capacitance (∼161–170 F g −1 ), specific energy (29–31.34 Wh kg −1 ), and power density (839–860 W kg −1 ) at 1 A g −1 . Supercapacitors based on ACs pre-treated via hydrothermal and ethanol soaking outperform devices based on simple chemically/physically ACs in rate performance, while hydrothermally pre-treated AC demonstrates superior stability over 8000 cycles, exhibits initial 15 % capacitance fading and coulombic efficiency close to 99–100 %.