One-step synthesis of SnOx nanocrystalline aggregates encapsulated by amorphous TiO2 as an anode in Li-ion battery

Abstract

SnO_x nanocrystalline aggregates (NAs) encapsulated by an amorphous TiO₂ layer have been successfully designed by a one-step flame spray pyrolysis (FSP). The synthesized SnO_x NAs@TiO₂ with different degrees of aggregations were composed of SnO_x nanocrystallites ranging from 5 nm to 10 nm and a TiO₂ layer with a thickness of 1–5 nm. The encapsulated TiO₂ layer was introduced in situ by incorporating TiCl₄ into the downstream of an FSP reactor, where TiO₂ nucleated and grew in the surface of the SnO_x NAs. The hydrolysis temperature of TiCl₄ in a flame was controlled to synthesize amorphous TiO₂ with intrinsic electrochemical features. As an anode in LIBs (Li-ion batteries), the SnO_x NAs@TiO₂ electrode showed superior cycle life and rate performance (capacity of 350 mA h g⁻¹ after 300 cycles and 332 mA h g⁻¹ at 1 A g⁻¹) compared to pure SnO_x or TiO₂ electrodes. The remarkably enhanced Li⁺ storage performance is mainly attributed to the nanoscale of nanocrystalline aggregates, the core–shell structure of SnO_x@TiO₂ and the amorphous state of TiO₂.