Honeycomb-like carbon nanoflakes as a host for SnO₂ nanoparticles allowing enhanced lithium storage performance

While possessing potential advantages as electrodes for lithium-ion batteries, SnO₂@carbon composites have been suffering from one common drawback-aggregation of Sn particles during the repeated alloying-dealloying cycles and the resulting pulverization issue. We combat this issue through the fabrication of honeycomb-like SnO₂@carbon nanoflakes (SnO₂@CNFs) that are able to confine SnO₂ nanoparticles within well-separated carbon cavities, so that the Li-Sn alloying-dealloying reaction occurs in the independent microreactors thus avoiding aggregation of Sn metal particles formed. The SnO₂ particle size, loading amount and the coverage density are controlled by adjusting the weight ratio between the tin precursor and the CNF. Transmission electron microscopy confirms that the highly graphitic honeycomb-like CNF matrix efficiently buffers and accommodates volume changes of the Li-Sn alloy. Used as anode materials for lithium-ion batteries, the SnO₂@CNFs with 66.0 wt% SnO₂ display the highest lithium storage capacity, delivering a discharge capacity of 940 mA h g⁻¹ after 150 cycles at 200 mA g⁻¹. For the long-term and high-rate applications, the SnO₂@CNFs with 41.5 wt% SnO₂ show the best electrochemical performance, delivering a discharge capacity of 400 mA h g⁻¹ at 1 A g⁻¹ after 500 cycles.