One-pot facile synthesis of Janus-structured SnO₂-CuO composite nanorods and their application as anode materials in Li-ion batteries

SnO₂-CuO composite nanorods with a Janus structure were prepared by one-step flame spray pyrolysis. High-aspect-ratio SnO₂ nanorods were positioned on one side of the spherical CuO powder. The mean length of the rod-shaped crystals decreased from 200 to 20 nm when the SnO₂ content in the composite powders decreased from 70 to 10 wt%. Initially, SnO ₂-CuO composite nanopowders formed from the vapors in the high-temperature diffusion flame by surface growth and coagulation. Phase separation of the composite nanopowders occurred and rod-like Janus structures evolved during the growth of SnO₂ and CuO crystals in the quenching process. The maximum charge capacities of pure SnO₂ and the composite powders with SnO₂/CuO of 90/10, 70/30, and 50/50 were 547, 499, 493, and 316 mA h g^-1, respectively, at a high current density of 3000 mA g^-1. The corresponding capacity retentions after 50 cycles were found to be 39, 47, 80, and 85%, respectively. The decrease in the charge capacity with increasing current density was slower in SnO₂-CuO (70/30) composite powders than in pure SnO₂. The Janus-structured SnO₂-CuO (70/30) composite powders showed a high charge capacity and excellent cycling performance at high current densities.