Theoretical prediction of two-dimensional Cr3C2 monolayer and its derivatives as potential electrode of Li-ion batteries

The investigations on Cr3C2 and Cr3C2T2 (T = F, Cl, O, OH) monolayers as promising electrode materials for lithium-ion battery (LIBs) are systematically carried out by Hubbard-corrected density functional theory (DFT + U). It indicates that Cr3C2 monolayer and its derivatives are dynamically and thermally stable. At the same time, the pristine Cr3C2 monolayer exhibits metallic character and the conductivity can be maintained through chemical modification. The lithium diffusion barrier on Cr3C2 monolayer is only 0.024 eV, which can guarantee a fast rate during the charge/discharge process. The storage capacity of Cr3C2 monolayer adsorbing one layer of Li atoms is about 298 mAh/g. It is found that the Cr3C2T2 (T = Cl, O, OH) monolayer can keep at least one layer of Li atoms adsorbed without any structural deformation, and the theoretical capacities are 214, 253 and 250 mAh/g, respectively. The Li storage capacities can be increased exponentially with the more layers of Li atoms adsorbing on the two-dimensional (2D) materials. Thus, Cr3C2 and Cr3C2T2 monolayers are potential electrode materials for LIBs.