Enhancing Temperature‐Optimized Ionic Liquid Electrolytes for High‐Voltage, High‐Energy Supercapacitors Utilizing Date Stone‐Derived Carbon in Coin Cell Configuration

ABSTRACT This study investigates the advancement of coin cell supercapacitors (SCs) for sustainable, high‐performance energy storage by employing biomass‐derived date stone activated carbon with various ionic liquid (IL) electrolytes at different temperatures. The research reveals that SCs demonstrate both pseudocapacitive and electrochemical double‐layer characteristics. Among the tested ILs, 1‐Butyl‐3‐methylimidazolium trifluoromethanesulfonate (BMIMOTf) emerges as the most effective, achieving an impressive energy density of 129.9 Wh kg −1 , a power density of 403.8 W kg −1 , and a specific capacitance of 103.9 F g −1 at 0.5 A g − 1 . After 5000 cycles, the supercapacitor utilizing BMIMOTf maintains 97.3% of its initial capacitance and exhibits a Coulombic efficiency approaching 100%. Additionally, temperature‐dependent analyses from room temperature to 50°C reveal that higher temperatures boost the electrochemical performance of the SC, attributed to improved ionic conductivity. This research offers a more comprehensive understanding of how materials and electrolytes interact, emphasizing the capacity of BMIMOTf to foster innovations in eco‐friendly energy storage solutions.