Electrolyte Design for Low Temperature Lithium-Sulfur Battery: From Different Polysulfide Conversion Mechanisms

With the increasing demand for large-scale energy storage devices, lithium-sulfur (Li-S) batteries have emerged as a promising candidate because of their ultrahigh energy density (2600 Wh Kg-1) and the cost-effectiveness of sulfur cathodes. However, the notorious shuttle effect derived from lithium polysulfide species (LiPSs) hampers their practical application, especially at low temperature. Therefore, electrolytes with low viscosity and high conductivity are required with the advancement of next-generation Li-S batteries. Understanding the interface structure dependent solvent electrochemistry and recognizing the existing issues relating to electrolytes are indispensable prerequisites. This review briefly summarizes the challenges to further develop the new generation of Li-S batteries, which can operate steadily at subzero temperature, including LiPSs accumulation, Li2S nucleation, lithium deposition, and so on. On the basis of the crucial role of electrolytes in solving these questions, we outline the corresponding electrolyte design strategies from the different mechanisms (solid-liquid-solid conversion, all-solid-phase conversion, and all-liquid-phase conversion) such as lithium salt modification, additive introduction, and introduction of strong cationic electrolytes, as well as the application of solid-state electrolytes, and so on. Finally, we emphasize promising strategies and solutions to improve low-temperature performance, pointing the way for the future development of maximizing extreme-temperature electrolytes toward practical applications.