Low-polarity solvent-mediated lithium metal stabilization for improved performance in lithium–sulfur batteries

Abstract

Rechargeable lithium–sulfur (Li–S) batteries are considered promising next-generation energy storage systems owing to their high theoretical energy density, but their application is hindered by the shuttle effect arising from dissolved lithium polysulfides (LiPSs). Herein, we design an optimized electrolyte to achieve long-term stability by employing an appropriate low-polarity solvent. A combination of diethyl ether (DEE) and 1,2-dimethoxyethane (DME) was selected to improve Li metal stability even in the presence of LiPSs. The DEE/DME electrolyte not only suppresses parasitic reactions between Li and LiPSs but also promotes uniform Li deposition. Moreover, operando optical microscopy was employed to directly visualize electrolyte stability and dendrite evolution in real time, while quantitative analysis was conducted via normalized hue index and contour image mapping. The enhanced anode stability of the DEE/DME electrolyte enabled excellent cycling performance, retaining 80.14% of its initial capacity after 300 cycles at 3 C, while maintaining superior performance under practical conditions with high sulfur loading and a low E/S ratio. These findings highlight that solvent properties critically influence Li metal stabilization in Li–S batteries and underscore the significance of solvent engineering in electrolyte design.