Ultra-fine SnO2 nanocrystals anchored on reduced graphene oxide as a high-performance anode material for sodium-ion batteries.

SnO2 has attracted extensive research attentions as a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, its application is largely hindered by sluggish sodium ion diffusion and drastic volume change during the conversion reaction and alloying process. Herein, ultra-fine SnO2 nanocrystals (3-5 nm) anchored on reduced graphene oxide (rGO) is demonstrated as a promising anode material for SIBs. Ultra-fine SnO2 nanocrystals are uniformly grown on rGO sheets by a facile one-step hydrothermal process. Nano-scaled SnO2 grains tolerate volume expansion and provide shortened diffusion pathway for sodium ions, and meanwhile rGO acts as an excellent conductive matrix, thus endowing the composite electrode with excellent electrochemical performance. More importantly, the ratio of SnO2 to rGO in the composite is optimized. The optimized sample delivers an initial charge capacity of 518 mAh g-1 at a current density of 50 mA g-1, and 504 mAh g-1 after 300 cycles at a current density of 100 mA g-1. Furthermore, a capacity of 287 mAh g-1 can be maintained after 1000 cycles at a current density of 1000 mA g-1.