Liquid metal batteries for future energy storage

The search for alternatives to traditional Li-ion batteries is a continuous quest for the chemistry and materials science communities. One representative group is the family of rechargeable liquid metal batteries, which were initially exploited with a view to implementing intermittent energy sources due to their specific benefits including their ultrafast electrode charge-transfer kinetics and their ability to resist microstructural electrode degradation. Although conventional liquid metal batteries require high temperatures to liquify electrodes, and maintain the high conductivity of molten salt electrolytes, the degrees of electrochemical irreversibility induced by their corrosive active components emerged as a drawback. In addition, safety issues caused by the complexity of parasitic chemical reactivities at high temperatures further complicated their practical applications. To address these challenges, new paradigms for liquid metal batteries operated at room or intermediate temperatures are explored to circumvent the thermal management problems, corrosive reactions, and challenges related to hermetic sealing, by applying alternative electrodes, manipulating the underlying electrochemical behavior via electrolyte design concepts, and engineering the electrode-electrolyte interfaces, thereby enabling both conventional and completely new functionalities. This report briefly summarizes previous research on liquid metal batteries and, in particular, highlights our fresh understanding of the electrochemistry of liquid metal batteries that have arisen from researchers' efforts, along with discovered hurdles that have been realized in reformulated cells. Finally, the feasibility of new liquid metal batteries is discussed along with their distinct chemistries and performance characteristics to answer the question of how liquid metals can be accessible for next-generation battery systems.