Nanoconfined SnO2/SnSe2 heterostructures in N-doped carbon nanotubes for high-performance sodium-ion batteries

Tin-based compounds are promising anode materials for sodium-ion batteries (SIBs), owing to their high theoretical capacities and relatively low sodiation potential. However, their high-rate performance and cycle life-span are severely impeded by the inherent sluggish reaction kinetics and large structural change during charging and discharging. Herein, we report a composite anode consisting of SnO2/SnSe2 heterostructure nanoparticles uniformly encapsulated in N-doped carbon nanotubes (SnO2/SnSe2@C) for high-performance SIBs. The hollow tube nano-architecture not only accommodates the volume expansion of SnO2/SnSe2, but also facilitates the electrolyte penetration and shortens Na+ pathways. Meanwhile, the N-doped carbon shells provide highways for electron transport and contribute to the total capacity. More importantly, the construction of heterostructures boosts the charge transfer kinetics and further stabilizes the electrode structure by the additional confining effects of the increased crystalline boundaries. Benefiting from the synergistic effects between the elaborately-designed electrode architecture and the incorporation of heterostructures, the SnO2/SnSe2@C composite delivered a superior rate capability (322 mAh g−1 at 4 A g−1) and remarkable cycling stability with a capacity retention of 87.7% after 1000 cycles at 2 A g−1.