Recent trends in the development of MXenes and MXene-based composites as anode materials for Li-ion batteries

Two-dimensional (2D) nanomaterials have been introduced as superior materials for energy applications owing to their high electrical conductivity, high surface area, and high mechanical strength. Since 2011 MXenes, have attracted great attention as new 2D nanomaterials, in many applications due to their outstanding physicochemical properties. Recent works have shown that MXenes can be used as anode materials for Li-ion batteries (LIBs) due to their unique properties such as layered structure, excellent electrical conductivity, and hydrophilicity. It has been shown that the high specific capacity value of 320 mAh/g at a current 100 mA/g after 760 cycles can be achieved for MXenes. However, generally, MXenes suffer from the restacking issue during cycling, restricting their Li-ion storage capability. Most of the performed works have focused on the Li-ion storage capability of multi-layered MXene but they suffer from restacking phenomenon during cycling and their performance is similar to graphite. The performed studies have shown that increasing the interlayer spacing, changing the functional groups of MXenes, and synthesis of few-layered MXenes are the most important ways for improving the Li-ion storage capability of MXenes. MXene-based composites are generally prepared with two aims of restricting the restacking of the MXenes and also buffering the volumetric expansion and loss of electrical contact of high-capacity anode materials, achieving a synergic effect between the MXenes and other constituents of the composites. The results of reviewed works have demonstrated that the addition of the low contents of MXenes to the metal oxides, transition metal dichalcogenides (TMDs), and silicon can significantly address their issues for their practical applications in LIBs. In this review, the most important works on the use of MXenes and MXene-based composite anode materials for LIBs are summarized. The main results, mechanisms of operation, and parameters affecting the electrochemical performance of MXene-based anodes for LIBs are reviewed.