Nanoconfined SnS2 in robust SnO2 nanocrystals building heterostructures for stable sodium ion storage

Transition-metal dichalcogenides are emerging as a class of attractive host materials for Na+ insertion, owing to its high theoretical specific capacity, whereas the intrinsic low conductivity and huge volume fluctuations during deep cycles severely restrict their practical applications. Heterostructure engineering can not only optimize ion transport kinetics to boost rate property but confine mechanical degradation by participation of the second phases. In order to cushion the internal stress and dramatic volume variations induced by the large radius of Na+, herein we introduced a more robust material (SnO2) to construct CC@SnS2/SnO2 heterostructure for sodium-ion batteries (SIBs). The experimental and density functional theory calculations indicate that compressive stress at the heterogeneous interface can effectively buffer the sodiation-induced internal strain by 10%, further maintain the structural stability and improve the cycling performances. Meanwhile, the involvement of inert SnO2 phase, which effectively alleviate the serious volume expansion caused by the active SnS2 upon an extensive sodiation/ desodiation process. As expected, the CC@SnS2/SnO2 composite exhibits high reversible capacity (694.7 mAh g(-1) at 0.2 A g(-1)) and long-term cycling retention (78.3% after 100 cycles). Our work inspire a pathway of the selection of heterogeneous materials toward a highly stable SIBs anode.