Fluorination of PEO-based polymer electrolytes and their application in solid-state lithium batteries

Solid-state lithium batteries offer a promising solution to address the growing demand for high-energy-density energy storage systems, particularly in the context of new energy vehicles. Among various solid electrolytes, poly(ethylene oxide) (PEO)-based polymer electrolytes have attracted considerable research interest owing to their exceptional flexibility, excellent interfacial compatibility with lithium metal, low cost and ease of processing. However, PEO-based solid electrolytes face several critical challenges, including low ionic conductivity at room temperature, a narrow electrochemical stability window, inadequate mechanical strength and interfacial instability with lithium metal anodes. Fluorine is the most electronegative element in the periodic table. It forms chemical bonds with high bond energy and stability. Thus fluorine-containing materials are valuable for electrolyte applications. This paper systematically summarizes recent advances in fluorination modification strategies for PEO-based electrolytes and provides an in-depth discussion of the underlying mechanisms. Furthermore, we outline prospective research directions for the development of fluorinated PEO-based electrolytes. Investigations of these strategies are expected to enhance the comprehensive and fundamental understanding of fluorinated PEO-based polymer electrolytes and offer new insights for their practical implementation in solid-state batteries.