Reaction Mechanisms, Design Principles, and Engineering Strategies of Metal Halides in High‐Performance Lithium Rechargeable Batteries

Abstract Lithium‐based batteries (LBs) dominate current rechargeable technologies, and lithium‐ion batteries in them have been successfully commercialized. However, the limited energy density of LIBs remains a huge challenge. Lithium‐metal batteries, employing metal lithium as the anode, exhibit exceptional theoretical capacity, but safety concerns such as thermal runaway significantly hinder their commercialization. In recent years, lithium–sulfur batteries have emerged as promising alternatives due to ultra‐high theoretical specific capacity and energy density. Nonetheless, their practical applications are still impeded by challenges, including the insulating nature and volume expansion of sulfur cathode, “shuttle effect” of lithium polysulfides, and uncontrolled lithium dendrite growth. Metal halides (MHs), featuring unique physicochemical properties and excellent electrochemical performances, have become a novel research focus. Based on this, this review first elucidates the detailed reaction mechanistic roles of MHs in various LBs. Subsequently, it also systematically summarizes the research progress of MHs, including design principles and engineering strategies in high‐performance LBs in recent years from the aspects of cell cathode, anode, and separator, respectively. Finally, the review provides some novel insights into the future direction of MHs. These considerations and suggested insights will provide more meaningful references for realizing high‐performance LBs.