An overview of 2D metal sulfides and carbides as Na host materials for Na-ion batteries

Both sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) operate on a similar principle and are striking for energy storage purposes. Although some electrode materials adapt favorably to LIBs, they are not pertinent for SIBs systems because Na+ (0.98 Å) has a significantly bigger diameter as compared to Li+ (0.69 Å). The use of two-dimensional (2D) materials as anodes for SIBs has established tremendous advancement in the last decade through their exceptional 2D layered structure, infinite planar lengths, and highly disclosed active sites. 2D materials assist the current SIB anode materials as profitable successors. To resolve the energy storage crisis, superior quality anode materials are essential for rechargeable next-generation SIBs. Among all anode materials, layered metal sulfides (MSs) and metal carbides (MCs) are the promising host anodes for SIBs because of their substantial capacity and impressive redox reversibility. The distinctive structures of 2D MCs and MSs provide an innovative era to surmount the challenges in anode materials like structural collapse, volume change, small storage capacity, and confined phase variation. The layered structure and large surface area provide substantial potential for intercalating and hosting more Na ions, thus maximizing the storage capacity. This review delineates some influential 2D MCs and MSs for anodic uses. In this review, we analyze theoretical and experimental techniques for scrutinizing predicted anode materials, electronic characteristics, and electrochemical performances, and they are reported to be beneficial for SIBs. Furthermore, the future perspective and the material design are described. The light shaded on the 2D MCs and MSs is anticipated to identify new anode materials for SIBs.