Research progress on gel polymer electrolytes for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have become a promising candidate for advanced energy storage system owing to low cost and high theoretical specific energy. In the last decade, in pursuit of Li-S batteries with enhanced safety and energy density, the investigation on the electrolytes has leaped form liquid organic electrolytes to solid polymer ones. However, such solid-state Li-S battery system is greatly limited by unfavorable ionic conductivity, poor interfacial contact and narrow electrochemical windows on account of the absence of any liquid components. To address these issues, gel polymer electrolytes (GPEs), the incorporation of liquid electrolytes into solid polymer matrixes, have been newly developed. Although the excellent ionic transport and low interfacial resistance provided by GPEs have prompted numerous researchers to make certain progress on high-performance Li-S coins, a comprehensive review on GPEs for Li-S batteries remains vacant. Herein, this review focuses on recent development and progress on GPEs in view of their physical and chemical properties for the applications in Li-S batteries. Studies on the components including solid hosts, liquid solutions and fillers of GPEs are systematically summarized with particular emphasis on the relationship between components and performance. Finally, current challenges and directional outlook for fabricating GPEs-based Li-S batteries with outstanding performance are outlined.