In Situ Electrochemical Tuning of MIL‐88B(V)@rGO into Amorphous V2O5@rGO as Cathode for High‐Performance Aqueous Zinc‐Ion Battery

Abstract The design and fabrication of advanced cathode materials with excellent electrochemical properties to match the Zn anode is crucial for the development of aqueous zinc‐ion batteries (ZIBs). Herein the synthesis of MIL‐88B(V)@rGO composites is reported, in which MIL‐88B(V) nanorods are anchored on reduced graphene oxide (rGO) sheets, as cathode for ZIBs, where the graphene oxide induces the formation of small‐size nanorods instead of typical prism morphology. During the initial charge/discharge process, the cathode undergoes an in situ irreversible transformation from MIL‐88B(V) to amorphous V 2 O 5 that acts as active site for the subsequent Zn 2+ insertion/extraction. The hierarchical structure of the composites and the amorphous V 2 O 5 provide abundant channels and active sites for Zn 2+ diffusion and adsorption. The density functional theory calculation reveals that the rGO sheets have two functions, i.e., to improve the conductivity and to reduce the Zn 2+ migration energy barrier. Consequently, the MIL‐88B(V)@rGO cathode exhibits an ultrahigh reversible capacity of 479.6 mAh g −1 at 50 mA g −1 and good rate performance of 263.6 mAh g −1 at 5000 mA g −1 , which are superior to metal–organic frameworks (MOFs) cathodes reported in literature. This work may shed a new light to the design and fabrication of MOFs‐based cathodes for aqueous ZIBs.