Fundamental Design Principles and Engineering Strategies of Liquid‐Phase Electrolytes for Highly Durable Rechargeable Lithium Metal Batteries

Lithium (Li) metal has emerged as the premier anode candidate in next-generation high-energy-density batteries due to its ultrahigh theoretical capacity and ultralow electrochemical potential. However, critical technical barriers persist in Li metal anode implementation, such as uncontrolled Li dendrite growth and persistent interfacial side reactions. Acting as the mediating agent between cathodes and anodes, electrolytes critically determine battery overall performance. Taking solvent-salt-additive components as the entry point, adopting liquid-phase electrolyte engineering strategies to optimize electrolyte composition and regulate solvation structure can not only address the inherent issues of Li metal anodes, but also endow Li metal batteries with desired performances, including high safety, high-voltage tolerance, fast-charging capability, and wide-temperature operation. In this review, the design principles of reliable liquid-phase electrolytes for Li metal batteries are discussed in detail. The essential liquid-phase electrolyte engineering strategies, including designing new-type salt/solvent molecular architectures, restructuring salt-solvent combination systems, incorporating electrolyte additives with various functions, utilizing (localized) high-concentration electrolytes, and developing brand-new electrolyte formulations for adapting to different temperature ranges, are comprehensively summarized. Moreover, emerging design strategies, future design considerations, and remaining challenges in electrolyte engineering are highlighted, with the aim of pointing out potential opportunities to propel the practical development of Li metal batteries.