Ultrafine SnO2 dispersed carbon matrix composites derived by a sol–gel method as anode materials for lithium ion batteries

Ultrafine crystalline SnO2 particles (2–3 nm) dispersed carbon matrix composites are prepared by a sol–gel method. Citric acid and hydrous SnCl4 are used as the starting constituents. The effect of the calcination temperatures on the structure and electrochemical properties of the composites has been studied. Structure analyses show that ultrafine SnO2 particles form and disperse in the disordered carbon matrix in the calcination temperature range of 500–800 °C, forming SnO2/C composites, and the carbon content shows only a slight increase from 35.8 wt.% to 39.1 wt.% with the temperature. Nano-Sn particles form when the calcination temperature is increased to 900 °C, forming a SnO2/Sn/C composite, and the carbon content is increased to 49.3 wt.%. Electrochemical testing shows that the composite anodes provide high reversible cycle stability after several initial cycles, maintaining capacities of 380–400 mAh g−1 beyond 70 cycles for the calcination temperature of 600–800 °C. The effect of the structure feature of the ultrafine size of SnO2 and the disordered carbon matrix on the lithium insertion and extraction process, especially on the reversible behavior of the lithium ion reaction during cycling, is discussed.