A Novel High-Performance TiO_2-x /TiO_1-y N_y Coating Material for Silicon Anode in Lithium-Ion Batteries

Protective surface coatings on Si anodes are promising for improving the electrochemical performance of lithium-ion batteries (LIBs). Nevertheless, most coating materials have severe issues, including low initial coulombic efficiency, structural fracture, morphology control, and complicated synthetic processing. In this study, a multifunctional TiO_{2- x} /TiO_{1- y} N_y (TTN) formed via a facile and scalable synthetic process is applied as a coating material for Si anodes. A thin layer of amorphous TiO₂ is uniformly coated onto Si nanoparticles by a simple sol-gel method and then converted into a two phase TiO_{2- x} /TiO_{1- y} N_y via nitridation. The lithiated TiO_2-x provides high ionic and electrical conductivity, while TiO_1-y N_y can improve mechanical strength that alleviates volume change of Si to address capacity fading issue. Owing to these synergetic advantages, TiO_{2- x} /TiO_{1- y} N_y -coated Si (Si@TTN) exhibits excellent electrochemical properties, including a high charge capacity of 1650 mA h g^-1 at 0.1 A g^-1 and 84% capacity retention after 100 cycles at 1 A g^-1 . Moreover, a significantly enhanced rate performance can be achieved at a high current density. This investigation presents a facile and effective coating material to use as the high-capacity silicon anode in the emerging Si anode technology in LIBs.