One-Step Incorporation of Nitrogen and Vanadium between Ti₃C₂T_x MXene Interlayers Enhances Lithium Ion Storage Capability

Two-dimensional (2D) transition-metal carbide materials termed MXene have attracted huge attention in the field of electrochemical energy storage. To this end, MXenes whose capability depends on the M transition elements represent a new paradigm extending beyond the realm of oft-explored elemental 2D materials beginning with graphene. However, the as-prepared MXenes suffer from unsatisfied capability due to the loss M elements during the etching process for the preparation of MXenes. Here, taking Ti₃C₂T_x as an example, we demonstrate that nitrogen and vanadium incorporation by means of microwave irradiation in NH₄VO₃-containing ethylene glycol can significantly improve the electrochemical performance of multilayered Ti₃C₂T_x MXene. While maintaining the 2D structure of MXene layers, the N and V elements are incorporated between the Ti₃C₂T_x MXene interlayers in the forms of C–V–OH, C–V–O, V–O, and Ti–O–N species. Specifically, at a V:Ti atomic ratio of about 1:30 (N:Ti = 0.29), N and V incorporation between the Ti₃C₂T_x interlayers gives rise to an increase in capability by about 40%, corresponding to an impressive reversible capacity of 92 mA h g^–1 at 3 C rate after 1000 cycles. These results demonstrate that N (V)-incorporated Ti₃C₂T_x MXenes offer fascinating potential for high-performance electrode materials and provide guidelines for designing and engineering anode materials.