Critical role of quantum and electrical double layer capacitance in 2D electrode/ionic-liquid electrolyte based supercapacitors

Abstract

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 among the investigated materials for high-performance supercapacitors, while the study emphasizes the critical role of interfacial engineering in the design of next-generation energy storage systems.