Exploring the electronic and mechanical properties of lithium-decorated silicon carbide nanowires for energy storage

The high chemical stability of silicon carbide (SiC) is attractive to inhibit unwanted side chemical reaction and prolongate the cyclability performance of lithium ion batteries anodes. However, SiC has high surface lithiation energy barrier due to its intrinsic nature and the low electrical conductivity limited the application in this area. The surface modification of SiC is an alternative to boost the lithiation-delithiation kinetics. Hydrogen incor-poration on SiC surface is extensively used in semiconductor industry to passivate electrically active centers. In this work, we present a theoretical study of the effect of surface lithium (Li) atoms on the electronic and me-chanical properties of hydrogen passivated SiC nanowires (H-SiCNWs) with zinc-blende structure. The results show that the adsorption of Li on the carbon (C) atoms at the surface of the nanowire introduces new electronic states within the former band gap of the H-SiCNWs, whose main contribution comes from the C and silicon (Si) atoms in the valence and conduction bands, respectively. Moreover, the number of new bands within the former band gap increases as a function of the concentration of Li atoms and the systems remain as intrinsic semi-conductors up to the maximum Li concentrations. The formation energy reveals that the stability of the nano-wires increases when the concentration of Li atoms augments. Moreover, the values of the open circuit voltage are found between 1.6 and 1.9 V for all studied concentrations of Li atoms and morphologies. The charge population analysis indicates that the Li atoms give up charge to the C ones resulting in ionic bonds. On the other hand, the Young modulus of the H-SiCNWs increases when their diameter augments and their values are lower than that of the bulk SiC. Besides, the Young modulus slightly diminishes when the concentration of Li grows, then the mechanical resistance could offer a large useful life of the electrode. Finally, the maximum theoretical storage capacity values indicate that the SiC nanowires (SiCNWs) are good potential anodic materials for rechargeable Li-ion batteries.

Automated summary

The high chemical stability of silicon carbide (SiC) prevents unwanted side chemical reactions and enhances the cyclability performance of lithium-ion battery anodes. However, the high surface lithiation energy barrier and low electrical conductivity of SiC hinder its application. Surface modification of SiC through hydrogen incorporation is explored in this study. The results show that lithium (Li) adsorption on the surface of hydrogen-passivated SiC nanowires (H-SiCNWs) introduces new electronic states within the band gap, significantly improving their performance as anodic materials for Li-ion batteries.