Advanced aqueous sodium hybrid supercapacitors based on plant waste-derived activated carbon anode and multilayered Ti3C2 MXene cathode

Hybrid sodium supercapacitors are emerging as highly promising energy storage devices for current and future applications in high-power electronics and the automotive industry. However, pushing their performance to competitive levels requires the development of innovative electrode material combinations to simultaneously enhance specific energy and power while significantly reducing energy production costs. Here, we report the first demonstration of an aqueous sodium supercapacitor employing an asymmetric electrode configuration with multilayered Ti 3 C 2 T x MXene as the cathode and plant waste-derived activated carbon (AC) as the anode. In contrast to MXene/Carbon composite electrodes, already described in the literature, our system relies on asymmetric pairing of different electrode materials, exploiting their respective pseudocapacitive (MXene) and electric double-layer (AC) charge accumulation mechanisms. The device achieves a specific capacitance of 155 Ah/kg, a high energy density of 57 Wh/kg, and a power density of 2110 W/kg. These metrics are maintained over 5000 charge-discharge cycles, demonstrating excellent stability, rate performance, and Coulombic efficiency. The use of eco-friendly and low-cost AC from plant waste as an anode, in synergy with pseudocapacitive multilayered Ti 3 C 2 T x as cathode material, offers a sustainable route toward efficient energy storage systems, demonstrating the potential of this electrode combination in practical supercapacitor applications. • First capacitor demonstration with MXene cathode and biomass-based AC anode. • Multilayered MXene enables rapid electrochemical reactions. • Pseudocapacitance and double-layer effects together boost capacitor performance. • Asymmetric cell shows stable energy and power density over 5000 charge cycles.