| Summary: | A facile and universal route has been developed to synthesize yolk-shelled metal oxides@N doped C spheres with controllable void size. Based on this approach, a yolk-shelled SnO2@N dopped C (yolk-shelled SnO2@NxC) composite has been successfully synthesized for lithium-ion battery electrodes. The reported yolk-shelled SnO2@NxC, with SnO2 as inner shell and core, can remarkably increase the volumetric energy density of electrodes. The void between shell and core could accommodate the volume expansion during lithiation. More importantly, the NxC outer layer as a framework maintains the structure's integrity and shortens the transmission distance of charges. The results confirm the much-improved electrochemical performance. The yolk-shelled SnO2@NxC electrode delivers excellent cycling stability of 740 mAh g−1 at a current density of 0.25C after 750 cycles and a superior rate performance of 500 mAh g−1 at 5C (1C = 800 mA g−1). In addition, some other yolk-shelled metal oxides such as yolk-shelled TiO2 and yolk-shelled Fe2O3 have also been directly synthesized through the method in this paper for their proper applications.
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