Quasi-Solid, Bio-Renewable Supercapacitors Based on Cassava Peel and Cassava Starch and the Use of Carbon Dots as Performance Enhancers
Thanapat Jorn‐am, Preeyanuch Supchocksoonthorn, Wasinee Pholauyphon, Jedsada Manyam, Chalathorn Chanthad, Peerasak Paoprasert
Abstract
Despite receiving high regard as potential energy storage devices, high-performance supercapacitors that can be produced from bio-renewable sources at low cost are still in need. In this work, a novel fabrication process for cassava-based supercapacitors was described in which carbon dots (CDs) and activated carbon (AC) were prepared from cassava peel and a quasi-solid polymer electrolyte was prepared for the first time from cassava starch (CS). A specific capacitance (Csp) of 138.2 F g–1 was obtained from the AC electrode in the CS/H2SO4 electrolyte, which was much greater than 95.9 F g–1 of the AC electrode in a PVA/H2SO4 solution. The CDs were employed as additives in the electrode and electrolyte. The addition of 10 wt % CDs to the AC electrode in the pristine CS/H2SO4 electrolyte increased the Csp to 239.5 F g–1. When 0.02 wt % CDs were added to the CS/H2SO4 electrolyte, a high specific capacitance of 374.6 F g–1 was obtained. Moreover, the fabricated supercapacitor exhibited an impressive cycling stability of 93.3% after 10,000 cycles and showed good performance in a wide temperature range from −40 to 50 °C. Based on intensive electrochemical analysis using several models, the CDs were demonstrated to improve the Csp and cycling stability by enhancing the surface capacitance and surface-controlled processes. In this work, a novel, simple strategy was demonstrated for fabricating practical, high-performance supercapacitors from cassava at a low cost.