Two-Dimensional MnO2 as a Better Cathode Material for Lithium Ion Batteries

On the basis of first-principles calculations, we have systematically studied the adsorption and diffusion of Li ions on monolayer MnO2 and compared with other transition metal dichalcogenides (TMDs) and transition metal dioxides (TMOs). Monolayer MnO2 shows a relatively high Li adsorption energy of 4.37 eV and low Li diffusion barrier of 0.148 eV. The electronic analysis indicates that the electron transferred from Li to the empty orbital of the O atom and there is some orbital coupling between the s orbital of the Li atom and the p(z), orbital of the O atom in MnO2. Due to Li adsorption on both sides of the MnO2 layer, the theoretical Li storage capacity reaches as high as 616 mAh/g. Our results demonstrated that, compared to other two-dimensional (2D) nanomaterials, monolayer or few-layer MnO2 exhibits excellent performance on Li storage capacity and diffusion rate and is believed to be a promising electrode material for high-capacity Li ion batteries.