In situ polymerization of fluorinated electrolytes for high-voltage and long-cycling solid-state lithium metal batteries

Abstract

Currently, the practical application of liquid lithium-ion batteries faces challenges in meeting the requirements of high energy density and safety. To address concerns such as electrolyte leakage and flammability, solid polymer electrolytes (SPEs) have emerged as promising alternatives to liquid electrolytes. SPEs, particularly those synthesized via in situ polymerization processes, offer advantages in establishing robust interface contacts and compatibility with existing industrial production lines. However, the electrochemical stability of SPEs remains a hurdle for high-voltage lithium metal batteries (LMBs). To enhance interface uniformity, electrochemical stability, and thermal stability, researchers commonly employ fluorination strategies, thus expanding the potential of SPEs in high-voltage, long-cycling LMBs. Fluorine plays a crucial role in achieving these objectives due to its high electronegativity, polarization, outstanding dielectric properties, strong bond strength, stability, and hydrophobic nature. In this study, we delve into how fluorinated electrolytes improve interface stability between SPEs and electrodes by examining their underlying mechanisms. Besides, we provide an overview of current fluorination strategies and their impact on battery performance. Furthermore, we discuss challenges and issues associated with current in situ polymerized fluorinated SPE routes and propose practical strategies for consideration.

Keywords: Lithium metal batteries; In situ polymerization; Fluorinated polymer electrolytes; High-voltage; Long cycling; Stable interface.