Self-templating synthesis of carbon-encapsulated SnO2 hollow spheres: A promising anode material for lithium-ion batteries

Carbon-encapsulated SnO 2 hollow spheres were fabricated by a self-templating method from Sn spheres for lithium-ion batteries (LIBs). High-temperature annealing (e.g., 700 °C) inevitably led to the formation of Sn on the exterior surface, which was disadvantageous for long-term cycling. In contrast, the preparation at an optimal annealing temperature of 600 °C coupled with subsequent acid etching completely encapsulated the SnO 2 within a carbon shell while maintaining a stable hollow structure. The as-prepared carbon-encapsulated SnO 2 hollow spheres after acid etching (SnO 2 @C–6H) exhibited enhanced electrochemical performance for LIBs characterized by high cycling stability and rate capacity. Specifically, SnO 2 @C–6H displayed a reversible capacity of 897.9 mA h g −1 at 200 mA g −1 after 120 cycles and a promising rate capacity of 549.8 mA h g −1 at a high current density of up to 2000 mA g −1 . The obtained high-performance could be attributed to the formation of a unique hollow structure with an enlarged specific surface area of 215.18 m 2  g −1 and a relatively high degree of graphitization (i.e., I D /I G  = 0.84) of the carbon shell. A plausible cause for this performance was that the acquired hollow spheres not only provide a barrier effect for volume expansion and the aggregation of SnO 2 , but also promote lithium storage.