A Review of the Structural Design of Anode Materials in Sodium-Ion Batteries Based on MXenes and Their Composites

The typical two-dimensional layered structure materials, MXenes, are widely used in energy conversion and storage due to their high conductivity, ion transport ability, and rich surface structures. Recently, MXenes and their composites have been widely employed in secondary batteries, especially sodium-ion batteries (SIBs), with obvious performance improvement. As anodic materials, MXenes, metal oxides, metal sulfides, and other materials contain certain advantages in Na+ storage, but they individually also suffer from some issues and challenges, such as low conductivity and serious volume change, as well as the associated low capacity and poor cyclability. By virtue of the advantages of MXenes, with their high conductivity and ultrathin two-dimensional structures, the construction of surface-functionalized MXenes and MXene-based composites could effectively improve the conductivity and mass-transport properties of composites, alleviate volume expansion, and, thus, enhance the capacity properties, rate performances, and cycle stability of SIBs. Herein, we review the latest research status of the structural design of MXenes and Mxene-based materials, as well as their applications in SIBs. We briefly introduce the research background and introduce MXenes and SIBs, and focus on their structural designs and corresponding applications in SIBs. Finally, the important challenges of MXene-based materials applied to SIBs are discussed, and the future prospects of MXene-based composite developments in SIBs are presented.