Gate-Tunable High Energy and Power Density Using Ionic Liquid-2D MXene/Mica Hybrid Microcapacitor

The increasing demand for energy storage devices with high energy and power density is driving significant research efforts to develop advanced energy storage solutions. Among these, dielectric capacitors offer high power density but have low energy density. In this study, we present a gate-tunable hybrid dielectric capacitor architecture that integrates two-dimensional (2D) MXene (Ti₃C₂T_x) nanosheets, dielectric ionic liquid (IL), and 2D mica interlayers. This synergistic design creates an efficient charge storage interface by utilizing the high electrical conductivity of MXene, the high dielectric constant of ionic liquid, and the dielectric properties of mica. The applied side gate voltage through ionic liquid effectively modulates the formation of the electric double layer (EDL) of charge carriers and interfacial charge accumulation on the 2D surface, allowing for controllable enhancements in both energy and power densities. The fabricated IL/2D MXene/mica hybrid capacitors demonstrate remarkable energy storage performance, achieving a high energy density of ~65 mWh/cm³ and a power density of ~350 kW/cm³, which is significantly higher than Ionic liquid-based capacitors. This gate-dependent tunability demonstrates a promising strategy for designing next-generation, high-performance electrostatic capacitors suitable for flexible electronics and smart power systems.