Boosting the Zn-ion energy storage capability of graphene sandwiched nanoporous VO x 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 VO x wrapped with graphene nanosheets (rGO-VO x ) 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-VO x 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 V 2 O 5 transforms into layered Zn x V 2 O 5 · n H 2 O with larger interspacing upon cycling. NaV 6 O 15 and the in situ formed Zn x V 2 O 5 · n H 2 O co-contribute to the subsequent insertion and extraction process.