Heterostructural Sn/SnO2 microcube powders coated by a nitrogen-doped carbon layer as good-performance anode materials for lithium ion batteries

The nitrogen-doped carbon (NC) coating encapsulating heterostructural Sn/SnO2 microcube powders (Sn/SnO2@NC) are successfully fabricated through hydrothermal, polymerization of hydrogel, and carbonization processes, in which the SnO precursor powders exhibit regular microcube structure and uniform size distribution in the presence of optimized N2H4·H2O (3.0 mL of 1.0 mol/L). Interestingly, the precursor powders are easily subjected to a disproportionated reaction to yield the desirable heterostructural Sn/SnO2@NC microcube powders after being calcined at 600 °C in N2 atmosphere in the presence of home-made hydrogel. The coin cells assembled with the Sn/SnO2@NC electrode present a high initial discharge specific capacity (1058 mAh g-1 at 100 mA g-1), improved rate capability (an excellent DLi+ value of 2.82 × 10-15 cm2 s-1) and enhanced cycling stability (a reversible discharge specific capacity of 486.5 mAh g-1 after 100 cycles at 100 mA g-1). The enhanced electrochemical performance can be partly ascribed to the heterostructural microcube that can accelerate the transfer rate of lithium ions by shortening the transmission paths, and be partly to the NC coating that can accommodate the volume effect and contribute to partial lithium storage capacity. Therefore, the strategy may be able to extend the fabrication of Sn/SnO2 heterostructural microcube powders and further application as promising anode materials in lithium ion batteries.