Encapsulating Sulfides into Tridymite/Carbon Reactors Enables Stable Sodium Ion Conversion/Alloying Anode with High Initial Coulombic Efficiency Over 89%

Electrode dissolution/collapses and interfacial reactions pose challenges to batteries, leading to pronounced capacity loss particularly during the initial few cycles. As high-capacity conversion/alloying anodes for sodium storage, metal sulfides generally show unsatisfactory performances like poor initial Coulombic efficiency (ICE; mostly <70% in the usual electrolyte) and inferior cyclic stability due to thick solid-electrolyte interface (SEI) layer formation and ubiquitous volume/phase changes. Using SnS2 as an example, here, sulfides are elaborately encapsulated into functionalized amorphous tridymite/carbon reactors to address the above issues. The outer tridymite/carbon manifests good ionic permeability and superb electrochemical/mechanical tolerance against destructive Na+ insertion. Confining actives into tailored reactors endows SnS2 full of nanoboundaries with an ultrahigh ICE of approximate to 89.13% and remarkable electrochemical attributes including large initial capacity (Max. 733.24 mAh g(-1)), prominent stability in subsequent cycles, and excellent rate capability. Detailed investigation unveils that thin and steady SEI condition on tridymite/carbon rather than SnS2 is key to achieving outstanding ICE. Engineered reactors always keep intact and free of valence-state changes, guaranteeing capacities running at a high level without an evident downtrend. Their peculiar functions on enlisting Na+ diffusion/transport and inhibiting sulfides' release are also discussed. Packed full-cell Na-ion batteries with less irreversibility may show great potential in practical utilizations.

Automated summary

By encapsulating metal sulfides into tailored reactors, the performance of sodium-ion batteries can be improved, including initial Coulombic efficiency, stability, and rate capability. Engineered reactors maintain integrity and play a key role in Na+ diffusion/transport and inhibiting sulfides' release.