A heterogeneous structured C/SnO2/SnSe2@C hybrid: exploring the superior rate performance in sodium ion batteries

Transition metal oxides are regarded as the prospective anode materials for next-generation sodium-ion batteries owing to their high theoretical capacity. Nevertheless, its low conductivity and large volume variation obstruct its practical applications. In this study, a design of heterostructured SnO2/SnSe2 nanoparticles encapsulated by a carbon shell (C/SnO2/SnSe2@C) synthesized through a templating method and in-situ gas-phase selenization process. The rich heterostructures and the interfacial effect induced by a built-in electric field significantly accelerate reaction kinetics and enhance the reaction activity. When employed as an anode for sodium-ion batteries , C/SnO2/SnSe2@C electrodes achieve a superior rate performance (238.4 mAh/g at 5.0 A/g) and cycling performance (422.3 mAh/g at 0.1 A/g after 150 cycles; 289.7 mAh/g at 1.0 A/g after 200 cycles). A quantitative examination into the origin demonstrated that the Na+ storage is dominated by the fast surface redox reaction, which endows the heterostructure with a durable rate performance. Moreover, based on a dQ/dV analysis and in situ X-ray diffraction results, the C/SnO2/SnSe2@C anode has a hybrid mechanism of SnO2 (conversion and alloying reaction) and SnSe2 (intercalation, conversion, and alloying reactions). This strategy of the heterostructure design provides a potential route to develop high-performance sodium-ion storage materials and sheds light on the behavior of Na-storage mechanisms.