Redox-Additive Gel Polymer Electrolyte Based on the Biodegradable Polymer Pectin for Supercapacitors with Enhanced Thermal Stability

High Resolution Image Download MS PowerPoint Slide The implementation of environmentally green materials in energy storage technologies is essential to ensure a fair and ethical transition to net zero. In this work, we present a gel electrolyte (GPE) based on pectin, a biodegradable natural biopolymer synthesized by using lithium chloride (LiCl) and potassium iodide (KI) as redox additives to enhance the performance of a supercapacitor. GPE shows enhanced thermal stability and flame retardancy, as confirmed by thermogravimetric and differential scanning calorimetry analysis. The optimized redox-additive GPE exhibits high flexibility and outstanding electrochemical properties including a high ionic conductivity (σ = 43 mS cm –1 ) at room temperature and a wide stable potential window (∼2 V vs Ag/Ag + ). The optimized GPE, with a redox additive and without, was tested with activated carbon electrodes derived from melon peel waste in symmetric supercapacitors. The addition of a redox additive to GPE films directly influences the performance of supercapacitors, leading to a 5 times increase in the specific capacitance (∼437 F g –1 ) and specific gravimetric energy density (∼34 Wh kg –1 ). The optimized supercapacitor exhibits stable cycling performance up to ∼8000 cycles by having an initial ∼31% fade in capacitance and a high Coulombic efficiency close to 99–100%.