Systematic electrochemical characterizations of Si and SiO anodes for high-capacity Li-Ion batteries

Silicon monoxide (SiO), similar to its more common counterpart silicon (Si), is considered as an attracting anode material for advanced Li-ion batteries (LiBs) due to its high theoretical capacity. However, many electrochemical properties of SiO have not been explored as much as those of Si. In this study, we report fundamental properties of SiO as an anode material, which offer promising LiB performances superior to pure Si anodes. The Li-ion diffusion in SiO was found to be consistently faster than that in Si, as evidenced by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). As a result, SiO anodes can deliver much improved fast charging/discharging capability compared with pure Si anodes, which indicates that SiO is a better candidate for high-power cell applications. The volume expansion rate of SiO particles was determined to be ∼118% by using scanning electron microscopy (SEM)-based particle size distribution (PSD) analysis, which is less than half of that of Si particles (c.a. 280%). Meanwhile, the open circuit potential (OCP) of SiO was found to be very close to Si, except near the end of delithiation state. These results provide fundamental information on SiO for its future applications as the next generation LiB anodes.