Synthesis and Electrochemical Properties of a Si/SiO_x Composite for Reversible Lithium Storage

With the rapid development of electric vehicles and advanced portable electronic devices, the demand for higher-energy-density power sources continues to rise. Among various powers sources, Li ion batteries (LIBs) have been used as the most important power source due to their high energy density, reasonable cost, and long cycle life. Currently, carbonaceous materials are used as commercial anode materials because of their good cycle performance. However, graphite anodes exhibit a limited reversible capacity (LiC6: 372 mAh·g–1), which cannot meet the requirements for high-energy-density LIBs. Therefore, development of high-capacity anode materials is critical. To increase the reversible capacity of an anode, Li-alloy type materials have been intensively studied. Among various materials, Si has attracted a lot of interest because of its high theoretical specific capacity (Li15Si4: 3580 mAh·g–1) and natural abundance. In spite of the high theoretical specific capacity, Si anodes cannot be commercially used due to some drawbacks. The drastic volume variation (~400%) of Si during repeated alloying/dealloying processes causes mechanical pulverization of the electrode. As a result, capacity fading usually occurs. To resolve this issue, various approaches have been applied such as the use of Si nanostructures and active/inactive composites. However, these methods usually required time-consuming and complex procedures, which were not suitable for mass production. In this study, we propose a new Si/SiOx composite by incorporating excess Si as a stable anode material for LIBs. This Si/SiOx composite was prepared through a simple high energy mechanical milling process. Si nanoparticles and silicon monoxide were used as starting materials. To further improve the cyclic performance, a carbon coating on the composite was performed. The prepared materials were investigated by various materials and electrochemical analysis tools. The obtained composite electrode exhibited not only high reversible capacity but also superior cycle performance.