First-principles study on the lithiation/delithiation reactions of Si-doped iron oxide nanoparticles*

Iron oxidizing bacteria produce iron oxide based sludge-like matter (biogenous iron oxide, BIOX) assembled with nanoparticles (NP) that is doped with silicon in ambient environment. BIOX has been considered as unwanted substance in the environment for a long time, but it was proved recently that this material has great potential to be a functional material. For example, it is found that BIOX exhibits good performance as an anode material for lithium-ion battery. However underlying atomistic mechanisms remain elusive. In this study, we have investigated the lithiation/delithiation reactions to elucidate the microscopic reaction mechanism and effect of the impurity element on the reaction based on the first-principles molecular dynamics (FPMD) method. Our FPMD simulations show rapid charging and discharging of NP within 100 fs, with associated surface lithiation and delithiation, respectively. In this presentation, an essential role of Si-doping on the lithiation/delithiation reaction will be discussed with the simulation results.