MC2 (M = Y, Zr, Nb, and Mo) Monolayers Containing C2 Dimers: Prediction of Anode Materials for High-performance Sodium Ion Batteries

Seeking novel anode materials with high performance for sodium ion batteries (SIBs) is an attractive theme in developing energy storage devices. In this work, by means of density functional theory computations, we predicted a family of MC2 (M = Y, Zr, Nb, and Mo) monolayer containing C2-dimers to be promising anode materials for SIBs. The stability, electronic structure, adsorption/diffusion/storage behavior of sodium atoms in MC2 (M = Y, Zr, Nb, and Mo) monolayer were explored. Our computations revealed that Na adsorbed MC2 (M = Y, Zr, Nb, and Mo) monolayer show metallic characteristics that give rise to excellent electrical conductivity and Na mobility with low activation energies for diffusion (0.21, 0.04, 0.20, and 0.22 eV, respectively) in these materials, indicative of a fast charge/discharge rate. In addition, the theoretical capacities of the Na-adsorbed on YC2, ZrC2, NbC2, and MoC2 monolayer are 478, 697, 687, and 675 mA h g-1, respectively, higher than that of commercial graphite (284 mA h g-1), and the open-circuit voltage are moderate (0.110.25 V). Our results suggest that MC2 (M = Y, Zr, Nb, and Mo) monolayers have great potential to serve as anode materials for SIBs.