One-pot synthesis of core-shell-structured tin oxide-carbon composite powders by spray pyrolysis for use as anode materials in Li-ion batteries

Abstract Core-shell-structured tin oxide-carbon composite powders with mixed SnO₂ and SnO tetragonal crystals are prepared by one-pot spray pyrolysis from a spray solution with tin oxalate and polyvinylpyrrolidone (PVP). The aggregate, made up of SnO_x nanocrystals (several tens of nanometers), is uniformly coated with an amorphous carbon layer. The initial discharge capacities of the bare SnO₂ and SnO_x-carbon composite powders at a current density of 1 A g^-1 are 1473 and 1667 mA h g^-1, respectively; their discharge capacities after 500 cycles are 78 and 1033 mA h g^-1, respectively. The SnO_x-carbon composite powders maintain their spherical morphology even after 500 cycles. On the other hand, the bare SnO₂ powder breaks into several pieces after cycling. The structural stability of the SnO_x-carbon composite powders results in a low charge transfer resistance and high lithium ion diffusion rate even after 500 cycles at a high current density of 2 A g^-1. Therefore, the SnO_x-carbon composite powders have superior electrochemical properties compared with those of the bare SnO₂ powders with a fine size.