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

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 C MXene (V CT ), 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 CT cathode is raised significantly from V /V to V /V , forming a nanoscale vanadium oxide (VO ) coating that effectively undergoes multi-electron reactions, whereas the inner V-C-V 2D multi-layers of V CT are intentionally preserved, providing abundant nanochannels with intrinsic high conductivity. Owing to the synergistic effects between the outer high-valence VO and inner conductive V-C-V, the activated V CT presents an ultrahigh rate performance, reaching 358 mAh g at 30 A g , together with remarkable energy and power density (318 Wh kg /22.5 kW kg ). The structural advantages of activated V CT 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. 2 2 x 2 x x 2 x x 2 x 2 x 2+ 3+ 4+ 5+ −1 −1 −1 −1