Ti–C bonds reinforced TiO2@C nanocomposite Na-ion battery electrodes by fluidized-bed plasma-enhanced chemical vapor deposition

Abstract

Carbon coatings hold great promise for next-generation non-conductive energy storage nanomaterials. However, simplicity, stable, uniformity and high-performance remain unresolved issues. Here, unique synergy of the fluidized bed reactor with plasmas enables highly-effective, single-step fluidized-bed plasma-enhanced chemical vapor deposition (FB-PECVD) of uniform, low-temperature carbon coatings on TiO2 nano-powder (TiO2@C). Plasma-specific effects induce the formation of new phases that are beneficial for energy storage. The 6 nm carbon layer is grown within only 10 min, while the TiO2 maintains its anatase phase. The unique plasma conditions make it possible to form Ti–C bonds at the Ti/C interface at much lower temperatures than achievable otherwise. The electronic transport at the interface and structural stability are thus greatly improved. Consequently, TiO2@C shows excellent electrochemical performances as a negative electrode of sodium ion battery, such as specific discharge capacity of 290.2 mA h g−1 at 50 mA g−1 and very stable long-term cyclability (101.2% capacity retention over 300 cycles at 4000 mA g−1). Our results show that FB-PECVD is not only a versatile method for bond-reinforced interface nanoparticle coating with carbon, but also provide a new strategy for designing hybrid-phase electrochemically active nanocomposite materials.