Delaminated V2C MXene Nanostructures Prepared via LiF Salt Etching for Electrochemical Applications

Vanadium carbide MXenes have demonstrated both one of the highest theoretical capacities for Li and Mg storage among all members of the MXene family and a high performance as cathodes for high-energy-density Zn-ion batteries (ZIBs). However, V2C research has been limited because of the instability of delaminated V2C (d-V2C) in water suspension. Herein, we propose improvements of the HF-free synthesis of V2C MXenes via selective etching of the V2AlC MAX phase by a HCl and LiF mixture. A combination of etching in the closed environment of the hydrothermal autoclave under continuous stirring and thermal isolation of a reaction vessel and improved washing techniques result in high-quality d-V2C MXene nanostructures. High crystallinity and chemical purity of the as-synthesized materials is confirmed by X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and aberration-corrected high-resolution transmission electron microscopy. A high concentration of Li cations in the etching mixture results in significantly improved stability of d-V2C in water suspension. In addition, cyclic voltammetry analysis is conducted to gauge the electrochemical characteristics of fabricated d-V2C MXenes. Electrochemical tests confirm that fabricated MXenes are highly promising as cathode materials for aqueous ZIBs. Moreover, a charge storage mechanism of V2C MXenes can be tuned through the implementation of different synthetic methods as well as electrochemical activation protocols.