Tailoring Alkalized and Oxidized V2CTx as Anode Materials for High-Performance Lithium Ion Batteries.

Abstract

V2CTx MXenes have gained considerable attention in lithium ion batteries (LIBs) owing to their special two-dimensional (2D) construction with large lithium storage capability. However, engineering high-capacity V2CTx MXenes is still a great challenge due to the limited interlayer space and poor surface terminations. In view of this, alkalized and oxidized V2CTx MXenes (OA-V2C) are envisaged. SEM characterization confirms the accordion-like layered morphology of OA-V2C. The XPS technique illustrates that undergoing alkalized and oxidized treatment, V2CTX MXene replaces -F and -OH with -O groups, which are more conducive to pseudocapacitive properties as well as Na ion diffusion, providing more active sites for ion storage in OA-V2C. Accordingly, the electrochemical performance of OA-V2C as anode materials for LIBs is evaluated in this work, showing excellent performance with high reversible capacity (601 mAh g-1 at 0.2 A g-1 over 500 cycles), competitive rate performance (222.2 mAh g-1 and 152.8 mAh g-1 at 2 A g-1 and 5 A g-1), as well as durable long-term cycling property (252 mAh g-1 at 5 A g-1 undergoing 5000 cycles). It is noted that the intercalation of Na+ ions and oxidation co-modification greatly reduces F surface termination and concurrently increases interlayer spacing in OA-V2C, significantly expediting ion/electron transportation and providing an efficient way to maximize the performance of MXenes in LIBs. This innovative refinement methodology paves the way for building high-performance V2CTx MXenes anode materials in LIBs.