Kinetics-driven design of 3D VN/MXene composite structure for superior zinc storage and charge transfer

Aqueous zinc-ion batteries (ZIBs) employing zinc as the anode have recently inspired widespread attention. However, crackly cathode and inefficient transfer kinetics upon the Zn2+ shuttle make the storage capacity and service life far from satisfactory to meet the practical demand. Herein, a 3D VN/MXene composite structure is elaborately designed as the electrode by uniformly encapsulating VN microspheres in MXene nanosheets, which prevents the microsphere over aggregation to ensure full exposure of reactive sites, and serves as a conductive buffer for inhibiting the structure damage to realize fast transfer kinetics. VN/MXene anode exhibits high reversible capacity (521 mAh g-1 vs. 324 mAh g-1) at 0.5 A g-1 and superior rate performance, remarkably higher than that of pure VN electrode. The capacity still maintains 146.3 mAh g-1 at 5 A g-1 coupled with high stability up to 2200 cycles. Moreover, the energy storage mechanism of highly reversible phase transition of VN upon Zn2+/H+ co-insertion/extraction is elucidated by in-situ X-ray diffraction and ex-situ X-ray photoelectron spectrometer. The structural merits of 3D VN/MXene composite work with fast and reversible Zn2+ (de)intercalation toward superior zinc storage and charge transfer. Such design strategy lights up a brilliant insight into the development of cathode materials for ZIBs.