Self‐Assembling Delaminated V4C3Tx MXene into Highly Stable Pseudocapacitive Flexible Film Electrode for Supercapacitors

Abstract The compactly stacked layers and the use of binders are detrimental to the rate performance and long cycle stability for V 4 C 3 T x MXene. To solve this problem and add a new member to flexible electrodes, the multi‐layered V 4 C 3 T x MXene is delaminated into nanoflakes (d‐V 4 C 3 T x ) with tetra‐n‐butylammonium hydroxide (TBAOH) and self‐assembled into the flexible film without binder. The d‐V 4 C 3 T x film as a negative electrode delivers a high specific capacitance of 292.0 F g ‐1 (622.4 F cm ‐3 ) at 2 mV s ‐1 , remarkable rate performance (86.0% at 200 mV s ‐1 , 78.4% at 500 mV s ‐1 ), and the splendid cycle stability (93.1% for 40 000 cycles, 82.9% for 60 000 cycles at 10 A g ‐1 ). The excellent electrochemical performance for the d‐V 4 C 3 T x film is attributed to the outstanding electrical conductivity (16 465.3 S m ‐1 ), and the large interlayer spacing (2.1 nm), as well as the surface capacitive control mechanism. The asymmetric supercapacitor composed of d‐V 4 C 3 T x film and activated carbon (AC) also shows high energy and power densities of 22.2 Wh L ‐1 at 285.3 W L ‐1 . This work provides a novel flexible and more stable film (d‐V 4 C 3 T x ) electrode with long cycle life for supercapacitors, and further promotes the development for flexible supercapacitors.