Two-Dimensional Transition Metal Dichalcogenide Monolayers as Promising Sodium Ion Battery Anodes

A family of transition metal dichalcogenide (TMD) nanosheets has recently shown its potential as negative electrodes in lithium ion batteries (LIBs). Herein, Na ion adsorption and migration properties as well as the possibility of phase transition induced by the Na adsorption on TiS2, VS2, CrS2, CoTe2, NiTe2, ZrS2, NbS2, and MoS2 are predicted using first-principles calculations. In terms of average voltage and capacity, M = Ti, Zr, Nb, and Mo are found to be suitable as anodes for sodium ion batteries (SIBs) with voltages of 0.49–0.95 V and theoretical capacities of 260–339 mA h g–1. Among the latter four screened TMDs, in particular, TiS2 and NbS2 are expected to maintain the same configurational phase upon sodiation (favorable kinetics) with Na ion migration barriers of 0.22 and 0.07 eV, respectively, suggesting that these TMD compounds could be promising for high-power energy storage applications. It is shown that a proper treatment of phase transitions during sodiation, though often neglected in the literature, is critical in an accurate theoretical description and interpretation of these two-dimensional materials.