Two-dimensional V2C@Se (MXene) composite cathode material for high-performance rechargeable aluminum batteries

Compared to lithium-ion batteries, rechargeable aluminum batteries as the potential safer, cheaper, and higher capacity energy storage devices have received more and more attention and research. Herein, we successfully synthesized vanadium carbide (V2C) through etching with lithium fluoride and concentrated hydrochloric acid solution. The composite two-dimensional layered structure (V2C@Se) is formed after calcining with selenium. Through X-ray photoelectron spectroscopy and electrochemical analysis, it can be studied that the reversible redox reaction of V2C@Se mainly includes V2+/V3+, V4+/V5+ , and Se2-/Se2+ in the charging-discharging process. By studying the density functional theory (DFT) calculation results, it can be found that after selenium treatment the adsorption and diffusion of [AlCl4](-) on V2C surface are smoother than before (if functional groups such as -OH are considered). This method not only removed the -OH function group on the surfaces of V2C layers to improve the reversible intercalation of [AlCl4](-), but also realized higher energy density through the combination of Se and V2C layers. Due to the participation of selenium, the cathode materials can reversibly provide an initial discharge specific capacity of 402.5 mAh g(-1) at 1 A g(-1) , and 119.8 mAh g(-1) can be remained even after 1000 cycles. This study can inspire researchers to develop high energy density and high stability aluminum batteries (Al-batteries) by exploring the methods of synthesizing intercalation-type MXene composite cathode materials.