In‐Situ Electrochemically Activated Surface Vanadium Valence in V₂C MXene to Achieve High Capacity and Superior Rate Performance for Zn‐Ion Batteries

Abstract

Abstract Vanadium‐based materials are fascinating potential cathodes for high energy density Zn‐ion batteries (ZIBs), due to their high capacity arising from multi‐electron redox chemistry. Most vanadium‐based materials suffer from poor rate capability, however, owing to their low conductivity and large dimension. Here, we propose the application of V 2 C MXene (V 2 CT x ), a conductive 2D nanomaterial, for achieving high energy density ZIBs with superior rate capability. Through an initial charging activation, the valence of surface vanadium in V 2 CT x cathode is raised significantly from V 2+ /V 3+ to V 4+ /V 5+ , forming a nanoscale vanadium oxide (VO x ) coating that effectively undergoes multi‐electron reactions, whereas the inner V‐C‐V 2D multi‐layers of V 2 CT x are intentionally preserved, providing abundant nanochannels with intrinsic high conductivity. Owing to the synergistic effects between the outer high‐valence VO x and inner conductive V‐C‐V, the activated V 2 CT x presents an ultrahigh rate performance, reaching 358 mAh g −1 at 30 A g −1 , together with remarkable energy and power density (318 Wh kg −1 /22.5 kW kg −1 ). The structural advantages of activated V 2 CT x are maintained after 2000 cycles, offering excellent stability with nearly 100% Coulombic efficiency. This work provides key insights into the design of high‐performance cathode materials for advanced ZIBs.