Influence of Additives on the Electrochemical and Interfacial Properties of SiOx-Based Anode Materials for Lithium-Sulfur Batteries

Abstract

The influence of electrolyte additives on the electrochemical and interfacial properties of SiOx-based anodes for lithium-sulfur batteries (Li-S) was systematically investigated. Four different electrolyte additives, namely, lithium nitrate, vinylene carbonate (VC), vinyl ethylene carbonate, and fluoroethylene carbonate (FEC), were added to the bare electrolyte comprising 1 M LiTFSI in tetraethylene glycol dimethyl ether/1,3 dioxolane in a ratio of 1:1 (v/v). The self-extinguishing time (SET) of the liquid electrolytes was measured. The 2032-type half-cells composed of Li/SiOx/Si/C were assembled, and their charge-discharge studies were analyzed at the 0.1 Crate. Upon cycling, the electrode materials were subjected to surface morphology and differential scanning calorimetry analyses. The interfacial properties of SiOx-based electrodes were investigated by electrochemical impedance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy studies. Among the electrolytes examined, FEC-added electrolytes offered the lowest SET and interfacial resistance values. The superior charge-discharge properties of FEC-added electrolytes were attributed to the formation of a stable solid electrolyte interface layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the electrode surface.