Influence of oxygen content on the electrochemical behavior of SiO_x@C anodes for Li-ion battery

Silicon anode usually exhibits high capacity, good initial coulombic efficiency, but poor cycle performance. While the extra oxygen in SiO can significantly contribute to the cyclic stability but at the cost of initial coulombic efficiency. Therefore oxygen content plays a key role in the performance balance of silicon-based anode materials. In order to demonstrate the influence of oxygen content on the electrochemical performance of SiOx-based anodes, different O/Si ratio of SiOx@C composites (x = 0.95, 0.81, 0.71 and 0.61) have been synthesized through magnesiothermic reduction process. It is found that the SiO0.81@C composite exhibits the most excellent electrochemical performance with an initial reversible capacity of 1374 mA h/g and an ICE of 73%. After 200 cycles, the composite shows a reversible capacity of 1230 mA h/g with a capacity retention rate of similar to 90%. The results indicate that the rational O/Si ratio can realize the balance between cycling stability and ICE of SiOx anodes. This study can provide practical guidance for the design of SiOx-based anodes for Li-ion batteries.