High energy storage capacity and mechanical resistance of SiC nanowires with adsorbed Li atoms as anodic materials for rechargeable batteries

In this work, by using Density Functional Theory calculations, we investigated the effect of surface lithium (Li) atoms on the electronic and mechanical properties of hydrogen passivated silicon carbide nanowires with zinc-blende structure (SiCNWs) and grown along the [111] crystallographic direction. Four nanowire diameters and the sequential substitution of hydrogen (H) atoms bonded to carbon (C) ones by Li atoms were considered. The viability of the replacement of H atoms by Li ones was verified by the substitution energy. Likewise, the surface Li atoms maintain almost unaltered the structure of the nanowires, even for the maximum concentration of Li atoms studied, and the moduli of Young of the nanowires are almost independent of the number of Li atoms for the two largest diameters studied. The results also indicate that there is electronic charge transfer from Si to H and from H to C atoms resulting in an excess of negative (positive) charge in the C (Si) atoms, then the adsorption of Li atoms gives rise to a redistribution of electronic charge creating electronic states in both valence and conduction bands of the nanowires which maintain a semiconductor behavior. The open circuit voltage as a function of the number of Li atoms per nanowire unit cell indicates a maximum variation around 0.4 V, warranting the same energy necessary to adsorb or desorb Li atoms during the charge and discharge process. Also, the theoretical energy storage capacities have values ranging from 290 mAhg-1 up to 700 mAhg-1, the last one higher than graphite (372 mAhg-1) used in current Li batteries. The high theoretical storage capacity of SiCNWs, mechanical resistance, stable open circuit voltage and semiconductor behavior of [111]-suggest that they can be used as anodic materials for a new generation of rechargeable batteries.