Critical Role of Quantum and Electrical Double Layer Capacitance in 2D Electrode/Ionic-Liquid Electrolyte Based Supercapacitors.

This work examines graphene and MXene electrodes integrated with three imidazolium-based ionic liquid electrolytes for supercapacitor applications. Quantum capacitance and electric double-layer capacitance were systematically analyzed to evaluate electrode-electrolyte performance. MXenes exhibited nearly an order of magnitude higher quantum capacitance than multilayer graphene, highlighting their superior suitability. Among the electrolytes, EMIM-TCB showed limited applicability with peak capacitance confined to zero potential. In contrast, BMIM-PF 6 and BMIM-BF 4 displayed strong compatibility, particularly with MXenes, delivering enhanced capacitance across a wide potential range due to favorable structural and electrostatic interactions. Overall, the MXene-BMIM-PF 6 combination emerges as a promising candidate for high-performance supercapacitors, while the study emphasizes the critical role of interfacial engineering in the design of next-generation energy storage systems.