Sonochemical synthesis of SnO₂/carbon nanotubes encapsulated in graphene sheets composites for lithium ion batteries with superior electrochemical performance

The SnO₂/carbon nanotubes encapsulated in graphene sheets (CSGN) composites are synthesized via a sonochemical method which is straightforward, low-cost and operable under ambient conditions. The open spaces formed by carbon nanotubes and graphene offering the accommodation of volume change and the access of an easy electrolyte-wetting, and the improved electrical conductivity by the presence of graphene and carbon nanotubes, lead to the superior cycling performance. As a result, the CSGN with SnO₂ content of 61.4 wt% exhibits a reversible specific capacity of 842.9 mAh g^-1 at the first cycle and retains 793.8 mAh g^-1 after 50 cycles at a current density of 125 mA g^-1, indicating a high capacity retention rate of 94%. The cycling performance is attributed to the unique structure of CSGN and enhanced electrical conductivity, which may make much sense to the structure designing of other electrode materials for lithium ion batteries.