Room-temperature liquid metal and alloy systems for energy storage applications

Liquid metals (LM) and alloys that feature inherent deformability, high electronic conductivity, and superior electrochemical properties have attracted considerable research attention, especially in the energy storage research field for both portable devices and grid scale applications. Compared with high temperature LM systems requiring rigorous thermal management and sophisticated cell sealing, room temperature LMs, which can maintain the advantageous features of liquids without external energy input, are emerging as promising alternatives to build advanced energy storage devices. Moreover, compared with high-temperature liquid metal alternatives, RT-LMs are free of thermal management, corrosion, and sealing issues. In this perspective, we summarize recent advances, analyze current challenges, and provide prospects of the RT-LM systems as electrodes for rechargeable batteries. Starting with an introduction of LM systems and their features, we present the status of the development of liquid metal anodes. Theoretical and experimental explorations of mechanisms including phase equilibria, wetting behavior, and alloy deposition behavior in a battery using liquid metal electrodes (LME) are provided to guide the battery design. Taking NaK alkali metal alloys and Ga-based fusible alloys as two model LME systems, different battery designs are presented along with mechanistic discussions on cathode dependence, interfacial chemistry, and the multi-cation effect. In addition, other possible battery designs, major challenges, and possible opportunities for further developments of the RT LM-based energy storage systems are also discussed in the end. Liquid metals and alloy systems that feature inherent deformability, high electronic conductivity, and superior electrochemical properties have enabled further development of next-generation energy storage devices.