Natural Stibnite for Lithium-/Sodium-Ion Batteries: Carbon Dots Evoked High Initial Coulombic Efficiency

Abstract

HighlightsThe chemical process of local oxidation–partial reduction–deep coupling forstibnite reduction of carbon dots (CDs) is revealed by in-situ high-temperature X-raydiffraction.Sb2S3@xCDs anode delivers high initial coulombic efficiency in lithium ionbatteries (85.2%) and sodium ion batteries (82.9%), respectively.C–S bond influenced by oxygen-rich carbon matrix can restrain the conversion ofsulfur to sulfite, well confirmed by X-ray photoelectron spectroscopycharacterization of solid electrolyte interphase layers helped with densityfunctional theory calculations.CDs-induced Sb–O–C bond is proved to effectively regulate the interfacialelectronic structure.The application of Sb2S3 with marvelous theoretical capacity for alkali metal-ion batteries is seriously limited by its poor electrical conductivity and low initial coulombic efficiency (ICE). In this work, natural stibnite modified by carbon dots (Sb2S3@xCDs) is elaborately designed with high ICE. Greatly, chemical processes of local oxidation–partial reduction–deep coupling for stibnite reduction of CDs are clearly demonstrated, confirmed with in situ high-temperature X-ray diffraction. More impressively, the ICE for lithium-ion batteries (LIBs) is enhanced to 85%, through the effect of oxygen-rich carbon matrix on C–S bonds which inhibit the conversion of sulfur to sulfite, well supported by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. Not than less, it is found that Sb–O–C bonds existed in the interface effectively promote the electronic conductivity and expedite ion transmission by reducing the bandgap and restraining the slip of the dislocation. As a result, the optimal sample delivers a tremendous reversible capacity of 660 mAh g−1 in LIBs at a high current rate of 5 A g−1. This work provides a new methodology for enhancing the electrochemical energy storage performance of metal sulfides, especially for improving the ICE.