Boosting the Zn-ion energy storage capability of graphene sandwiched nanoporous VOx derived from MXene†
Aqueous rechargeable zinc-ion batteries (ZIBs) are emerging in grid energy storage due to zinc abundance and intrinsic safety. However, developing suitable cathode materials with satisfactory stability and rate capacity remains a great challenge. Herein, a structure of layered MXene derived nanoporous VOx wrapped with graphene nanosheets (rGO–VOx) is constructed as a cathode for ZIBs. The incorporation of two typical 2D materials imparts composites with shortened diffusion pathways and increased electrical conductivity. Thus, the rGO–VOx cathode exhibits a remarkable rate capability of 196 mA h g−1 at 8 A g−1 and long-term stability with 90% retention after over 1200 cycles at 5 A g−1 in an aqueous coin cell. The Zn storage mechanism is also systematically investigated. The layered V2O5 transforms into layered ZnxV2O5·nH2O with larger interspacing upon cycling. NaV6O15 and the in situ formed ZnxV2O5·nH2O co-contribute to the subsequent insertion and extraction process.