CrXY (X/Y = S, Se, Te) monolayers as efficient anode materials for Li and Na-ion batteries: a first-principles study.

Over the last decade, two-dimensional (2D) materials have been of great interest in the energy storage field. Large-scale electrochemical energy storage is based on the intercalation of metal ions in layered materials having van der Waals gaps. In this work, by means of first-principles calculations, we explored the use of 2D Janus transition metal dichalcogenides (TMDs) CrSSe, CrSTe and CrSeTe as anode materials for lithium and sodium-ion batteries. To examine the electronic properties and electrochemical performance, density functional theory (DFT) calculation was used. Our research shows that lithium diffuses easily with short diffusion distances and prefers to bind effectively to the monolayer. These structures are metallic in their bare phases. The highest adsorption energy shown by CrSSe, CrSTe, and CrSeTe is -1.86 eV, -1.66 eV, -2.15 eV with a low diffusion barrier of 0.3 eV, 0.6 eV, and 0.1 eV for the Li atoms and 0.54 eV, 0.32 eV and 0.15 eV for the Na atoms, respectively. At different chemical stoichiometries, we discovered negligible average open-circuit voltages of 1.0 V, 0.52 V, 0.6 V for lithium and 0.1 V, 0.49 V, and 0.51 V for sodium atoms respectively. The storage capacities shown by CrSSe, CrSTe, and CrSeTe are 348 mA h g-1, 254 mA h g-1, 208 mA h g-1 for the Li atoms and 260 mA h g-1, 198 mA h g-1, 177 mA h g-1 for the Na atoms respectively.