Boosting the energy density of aqueous MXene‐based supercapacitor by integrating 3D conducting polymer hydrogel cathode

Abstract The wide‐spread proliferation of aqueous MXene‐based supercapacitor has been largely shadowed by the limited cell potential window (typically in the range of 0–0.6 V). To address this baffling issue, designing asymmetric supercapacitor (ASC) is proposed as a rational strategy to enlarge the potential window (thus energy density) of individual cell in aqueous electrolytes. To this date, however, it still remains a great challenge to develop easy fabricating, 3D nanostructured, and pseudocapacitive cathode materials that can perfectly match with MXene anode materials. In this work, we propose a supramolecular strategy to construct conducting polymer hydrogel (CPH) with highly interconnected 3D nanostructures and large pseudocapacitance, which can finely match with 2D Ti 3 C 2 T x . The as‐assembled CPH//Ti 3 C 2 T x ASC with CPH cathode and MXene anode can operate in a broadened potential window of 1.15 V in aqueous PVA/H 2 SO 4 gel electrolyte with remarkably improved energy density of 16.6 μWh/cm 2 (nine times higher than that of symmetric MXene supercapacitor). Additionally, this ASC exhibits outstanding cyclic stability with no trackable performance decay over 30,000 galvanostatic charge and discharge cycles. It is demonstrated in this work that employing positive CPH electrode is a feasible yet promising strategy to enhance the potential window and energy density of aqueous MXene supercapacitors.