Development and assessment of an innovative gel electrolyte using polyvinyl alcohol, lithium sulfate, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate for advanced supercapacitor performance

The quest for gel electrolytes with superior ionic conductivity, robust mechanical strength and expanded voltage window is an ongoing and significant area of interest. This study introduces a gel electrolyte, formulated from polyvinyl alcohol (PVA), lithium sulfate (Li₂SO₄), and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (IL), termed PVA-Li₂SO₄-IL. Developed through a straightforward solution casting and a freezing-thawing process, the incorporation of an ionic liquid into the gel polymer containing lithium salt enhances both the ionic conductivity of the electrolyte and imposes some pseudocapacitance to the supercapacitor. Comprehensive characterizations of the gel electrolyte's morphology, chemical composition, crystallinity, thermal stability, and mechanical attributes were conducted using various characterization techniques. Notably, the optimized gel electrolyte demonstrates a high ionic conductivity of 13.32 mS/cm at ambient temperature, improved to a peak conductivity of 31.42 mS/cm at 80 °C. When employed in a symmetric supercapacitor using activated carbon derived from date stones (DSCA) as electrodes, the supercapacitor achieves an exceptional energy density of 65.14 Wh/kg and high power density of 5000 W/kg. This energy density is attained due to the high operating potential window of 2 V and a notable specific capacitance of 117.25 F/g at a current density of 0.5 A/g. Furthermore, the supercapacitor exhibits remarkable cycling stability, maintaining 88.7 % of its initial capacitance after 10,000 cycles. These results position the PVA-Li₂SO₄-IL gel electrolyte as a highly promising material for the advancement of high-power and high-energy-density energy storage systems.