Optimizing EMIMBF4-based electrolyte with LiBr redox medium for enhanced supercapacitors

The formidable challenge of supercapacitors (SCs) is to achieve both high energy density and high power density simultaneously. Although the utilization of porous carbon materials for physical adsorption in electrochemical double-layer capacitors (EDLCs) applications exhibits promising prospects, attaining exceptional performance necessitates additional methodologies. Here, we propose an effective strategy for formulating redox electrolytes through the incorporation of organic solvents and LiBr into 1-ethyl-3-methylimidazole tetrafluoroborate (EMIMBF4) electrolytes. Within this formulation, LiBr serves as a redox mediator, contributing Br−/Br3− redox pairs to the system. The incorporation of EMIMBF4-LiBr-DMSO in brominated redox EDLCs led to a significant enhancement in specific capacitance, reaching up to 39.72 F g−1, representing a remarkable increase of 159 % compared to EDLCs without any redox media. This configuration achieved a high power density of 496.6 W kg−1 while maintaining an energy density of 34.48 Wh kg−1.