Influence of disorder and surface roughness on the electrical and thermal properties of lithiated silicon nanowires

We use density functional theory and reactive-force-field methods to investigate the electrical and thermal transport properties of long disordered lithiated silicon nanowires. The latter could build the core of future lithium ion batteries with enhanced storage capacity. Due to the amorphous nature of these nanowires, disorder and surface roughness effects inevitably arise, affecting the lithiation process. It is found that the electrical conductivity of the nanowires steadily increases as a function of the lithium concentration, despite the presence of disorder, while the thermal conductivity follows the opposite trend and decreases significantly with reduced heat evacuation capabilities as a consequence. This behavior can be attributed to the influence of Li ions, which on one hand tend to metallize Si nanowires and thus enhance their electron mobility. On the other hand, the random distribution of Li atoms perturbs the phonon propagation through the nanowire, explaining the decrease in thermal conductivity.