Safety Hazards of Lithium Metal Batteries: From the Perspective of Lithium Dendrites and Thermal Runaway

Lithium metal batteries (LMBs) have stepped into the spotlight for a decade, featuring significant potential for high energy density as well as compatibility with off-the-shelf lithium-ion technologies. However, the commercialization of LMBs has lagged behind expectations due to safety concerns related to short circuits. Recent advancements have focused on tackling lithium dendrites and separator/electrolyte-related dielectric failure. In this review, we cover the main factors that promote lithium dendrites and cause separator/electrolyte failure, highlighting the lithium plating mechanism and the decomposition chain triggered by Joule heat. Based on the fundamentals of electrochemistry, we assess and summarize the promising approaches that have been widely applied and proven in literature practice, including the construction of separators with high mechanical modulus and lithium affinity, the incorporation of functional components in electrolytes to regulate lithium plating, and the enhancement of the thermal stability and thermal strain ability of the separator/electrolyte system, among others. We believe that the understanding of mechanisms and proposed strategies may approach the threshold of breakthroughs, and a periodical review is helpful for both academia and industry in pursuing the commercialization of LMBs.