Blends of Protic Ionic Liquid and Water as Electrolyte for Ultrastable Ti ₃ C ₂ T x MXene‐Based Asymmetric Supercapacitors

This study introduces trimethylammonium trifluoromethanesulfonate (N 111H TFO) as a promising salt for formulating aqueous protic ionic liquid (PIL) electrolytes in electrochemical supercapacitors. The temperature dynamic transport behavior of this electrolytic solution reveals high ionic conductivity and efficient ion dissociation, underscoring their suitability as environmentally benign electrolytes. When employed in an asymmetric supercapacitor featuring Ti 3 C 2 T x MXene and activated carbon (AC) as an active material in negative and positive electrodes respectively, the device delivers a specific capacitance of ~22 F g −1 . The capacitance retention exceeding 93% after 10,000 charge–discharge cycles demonstrates excellent electrochemical reversibility and interfacial stability. Importantly, the device exhibits exceptional long‐term floating stability, maintaining over 90% of its initial capacitance after 2500 h of continuous voltage stress. Postmortem transmission electron microscopy studies confirm the preservation of electrode morphology and structure, validating the robustness of the charge storage process. This work highlights the potential of PILs as safe, stable, and efficient electrolytes for next‐generation Ti 3 C 2 T x MXene‐based supercapacitors.