A MoO₂ sheet as a promising electrode material: ultrafast Li-diffusion and astonishing Li-storage capacity

The potential of MoO₂ crystal as an electrode material is reported, and nanostructural MoO₂ systems, including nanoparticles, nanospheres, nanobelts and nanowires, were synthesized and proved to be advanced electrode materials. A two-dimensional (2D) geometric structure represents an extreme of surface-to-volume ratio, and thus is more suitable as an electrode material in general. Stimulated by the recent fabrication of 2D MoO₂, we adopted an ab initio molecular dynamics simulation and density functional theory calculation to study the stability and electrochemical properties of a MoO₂ sheet. Identified by a phonon dispersion curve and potential energy curve calculations, the MoO₂ sheet proved to be dynamically and thermally stable. After lithiation, similar to most promising 2D structures, we found that a Li atom can strongly adsorb on a MoO₂ sheet, and the lithiated MoO₂ sheet presented excellent metallic properties. Note that, compared with most promising 2D structures, we unexpectedly revealed that the diffusion barrier of the Li atom on the MoO₂ sheet was much lower and the storage capacity of the MoO₂ sheet was much larger. The calculated energy barrier for the diffusion of Li on the MoO₂ sheet was only 75 meV, and, due to multilayer adsorption, the theoretical capacity of the MoO₂ sheet can reach up to 2513 mA h g^-1. Benefiting from general properties, such as strong Li-binding and excellent conductivity, and unique phenomena, such as ultrafast diffusion capacity and astonishing storage capacity, we highlight a new promising electrode material for the Li-ion battery.