Facile synthesis of ultrasmall stannic oxide nanoparticles as anode materials with superior cyclability and rate capability for lithium-ion batteries

Abstract

Ultrasmall monodisperse stannic oxide (SnO₂) nanocrystals (diameter around 4 nm) with high-performance lithium storage are successfully synthesized via a simple calcination process, during which SiO₂ mesoporous nanotubes (SiO₂-MNT) are used to play an important role in restraining the growth and aggregation of the nanocrystals. As a kind of anode material for lithium-ion batteries, the as-prepared SnO₂ nanocrystals show an excellent electrical performance with a super high reversible capacity of 816 mA h g⁻¹ over 200 charge/discharge cycles at a current density of 160 mA g⁻¹. Moreover, when the current density rises to 3200 mA g⁻¹, the capacity is still as high as 550 mA h g⁻¹, and it can be recovered to 816 mA h g⁻¹ simultaneously when the current density turns back to 80 mA g⁻¹. These results suggest that the obtained SnO₂ nanocrystals can achieve a completely reversible transformation from Li_4.4Sn to SnO during discharging (i.e., Li is extracted by dealloying and a reversible conversion reaction, generating 6.4 electrons). The superior electrochemical performance can be ascribed to the ultrafine particle size of SnO₂, which promotes the reactive activity and alleviates the volume change of the anode composite during charge/discharge cycling.