Search

Owing to the slight volume expansion after potassiation, hard carbon is regarded as a promising anode material for potassium-ion batteries (PIBs). Heteroatom doping (such as sulfur or nitrogen) is a common method to modify hard carbon for high K-storage capacity and long cycling performance. High sulfur-doped hard carbon with a sulfur content of 25.8 wt % is prepared by calcining glucose in molten salt (K2SO4@LiCl/KCl). It exhibits high specific capacities of 361.4 mA h g–1during the 1st cycle and 317.7 mA h g–1during the 100th cycle at 0.05 A g–1. The high capacity arises from the K–S reaction behavior, which is demonstrated by the cyclic voltammetry test and galvanostatic intermittent titration technique. This work is an effective application of the molten salt method for PIBs, furnishing an understanding to K-storage behaviors of hard carbon- with high sulfur content.

Highlights:

The chemical process of local oxidation–partial reduction–deep coupling for stibnite reduction of carbon dots (CDs) is revealed by in-situ high-temperature X-ray diffraction.

Sb2S3@xCDs anode delivers high initial coulombic efficiency in lithium ion batteries (85.2%) and sodium ion batteries (82.9%), respectively.

C–S bond influenced by oxygen-rich carbon matrix can restrain the conversion of sulfur to sulfite, well confirmed by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations.

CDs-induced Sb–O–C bond is proved to effectively regulate the interfacial electronic structure. Abstract: The application of Sb2S3with 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−1in 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.