Two-dimensional sandwich-like heterostructures of amorphous VO x /MXene as freestanding cathode materials with superior electrochemical performance for aqueous zinc-ion batteries

Although vanadium-based compounds are considered to be reliable zinc storage materials due to their high theoretical specific capacity, notorious poor conductivity and unstable structure hamper their practical applications. Herein, novel two-dimensional (2D) sandwich-like heterostructures of amorphous vanadium dioxide uniformly grown on two sides of ultrathin MXene nanosheets (A-VO x /M heterostructures) are constructed by ion adsorption method and following low-temperature annealing, which can be readily incorporated into carbon nanotube (CNT) network to obtain freestanding cathodes for aqueous zinc-ion batteries. The combination of 2D heterostructure, amorphous framework and conductive substrate endows A-VO x /M heterostructures with short ion diffusion pathway, high chemical stability, extra active sites and superior electrical conductivity. The freestanding A-VO x /M heterostructured cathodes for aqueous zinc-ion batteries exhibit a remarkable discharge capacity of 362 mAh g −1 at 0.2 A g −1 and high-rate capability of 202 mAh g −1 at 15 A g −1 as well as admirable cycling stability with a capacity decay of only 0.0043% per cycle over 3000 cycles. Besides, due to the outstanding conductivity and stability of freestanding A-VO x /M heterostructured cathodes, soft-package batteries are assembled with steady electrochemical performance, suggesting brilliant future in the field of energy storage.