Toward sustainable lithium batteries: From high-fluorine to fluorine-free electrolyte design

Lithium-based batteries, including lithium-ion batteries (LIBs) and lithium metal batteries (LMBs), underpin modern energy-storage technologies for electric vehicles and portable electronics. Fluorinated electrolytes have played a central role in the commercialization of LIBs owing to their favorable interfacial chemistry; however, increasing concerns regarding thermal and hydrolytic instability, hydrofluoric acid (HF) generation, toxic degradation products, and environmental persistence have stimulated growing interest in reducing or eliminating fluorine from electrolyte formulations. In this review, we present a systematic and quantitative evaluation of fluorine content across representative electrolyte systems and establish a unified framework that delineates the transition from fluorine-rich to low-fluorine and fluorine-free electrolyte designs. The fundamental electrochemical challenges associated with fluorine elimination are critically examined from the perspectives of solvation structure and interphase chemistry. Particular emphasis is placed on rational strategies for regulating solvation environments and engineering interfacial structures to compensate for the absence of fluorine-derived passivation layers while maintaining competitive electrochemical performance. Finally, future research priorities and design guidelines are proposed to accelerate the development of fluorine-free electrolytes. This review provides new insights into electrolyte design principles and offers a forward-looking perspective for the development of sustainable, high-performance lithium-based batteries with reduced fluorine reliance.