Flexible, highly conductive, and microscopically disordered MXene film electrode constructed via in-situ carbon dots intercalation toward high-performance supercapacitors

Two-dimensional MXenes are being recognized as favorable supercapacitor electrode materials due to their metallic conductivity, excellent hydrophilicity, high density, and rich surface chemistry. However, layer-restacking within MXene electrodes substantially hinders the efficient utilization of the active surface and ion accessibility. Herein, a unique carbon dots (CDs) intercalated MXene film (CDs-MF) is designed by introducing gelatin within the MXene interlayers followed by carbonization. The CD intercalation can enlarge the interlayer spacing of MXene film and induce microscopic disorder, exposing the active surface and facilitating ion diffusion within the electrode. The optimal CDs-MF electrode shows exceptional capacitive performance, achieving high gravimetric/volumetric capacitances (396.4 F g-1 at 1 A g-1 and 1,153.2 F cm-3 at 1 A cm-3), superior rate capability (123.2 F g-1 at 1,000 A g-1), and excellent cycling stability with no capacitance decay over 100,000 cycles. Moreover, the assembled quasi-solid-state symmetric supercapacitor exhibited a maximum energy density of 21.2 Wh L-1 and a power density of 12 kW L-1. The device could operate efficiently under various configurations (series or parallel) and different bending angles, reflecting its promising application in flexible energy storage devices.