Transition Metal Oxide–Decorated Titanium Carbide MXene Electrodes for High‐Energy Supercapacitors with an Expanded Potential Window

The growing demand for flexible and wearable devices drives the development of advanced energy‐storage technologies. Ti 3 C 2 T x MXene–based supercapacitors (SCs) gain attention for their fast charging and discharging capabilities, high power density, and long cycle life. However, the inherent restacking of MXene layers hinders efficient ion transport and limits electrochemical performance. To address this challenge, pseudocapacitive transition metal oxides (TMOs) such as CuO, Fe 3 O 4 , and MnO 2 are introduced as spacers to enhance the electrochemical properties of Ti 3 C 2 T x MXene electrodes. Among the composites, the Ti 3 C 2 T x MXene–MnO 2 (MX–M) electrode exhibits a superior specific capacitance of 212 F g −1 (specific capacity of 47 mA h g −1 ) at 1 A g −1 , outperforming pure MXene and other composites in a 6M KOH electrolyte. The potential window of the symmetric coin‐cell SC is successfully extended to 1.5 V in 1 M LiClO 4 /PC electrolyte, with the device delivering an impressive specific energy of 19.4 Wh kg −1 at a specific power of 1.5 kW kg −1 . Furthermore, by connecting three cells in series, the operating voltage is expanded to 4.5 V, demonstrating its effectiveness in powering light‐emitting diodes. These findings highlight the potential of TMO‐modified Ti 3 C 2 T x MXene electrodes for next‐generation energy‐storage devices with enhanced electrochemical performance.