The relationship between spectroscopic and electrochemical properties of NaCl-Glycerol deep eutectic electrolyte for supercapacitor

The urgent need for alternative energy sources has driven significant progress in electrochemical energy storage systems (EESS), including metal-ion batteries and electrochemical double-layer capacitors, which are critical for the widespread adoption of electric vehicles and renewable technologies like photovoltaics. Despite these advancements, EESS still depend on organic carbonate-based electrolytes, which pose challenges due to their flammability, toxicity, and environmental impact. To overcome these limitations, Deep Eutectic Solvents (DESs) have been proposed as a new class of electrolytes, characterized by low volatility, reduced flammability, and superior thermal and electrochemical stability. Our study aims to design truly green electrolytes, focusing on metal-polyol DESs for EESS. Through comprehensive thermal analysis (DSC) and vibrational spectroscopy (Raman and FIR), we not only identified the NaCl-Glycerol 1:10 mixture as DES but also uncovered the crucial relationship between the structural (conformational) features of Gly and the mass transport and electrochemical properties of the mixtures. Ultimately, the DES electrolyte we formulated was successfully tested in an electrochemical double-layer capacitor (EDLC), yielding remarkable performance results, underscoring the potential of these cost-effective and environmentally friendly electrolytes.