Progress and perspectives of liquid metal batteries.

The increasing demands for the penetration of renewable energy into the grid urgently call for low-cost and large-scale energy storage technologies. With an intrinsic dendrite-free feature, high rate capability, facile cell fabrication and use of earth-abundance materials, liquid metal batteries (LMBs) are regarded as a promising solution to grid-scale stationary energy storage. Typical three-liquid-layer LMBs require high temperatures (>350 °C) to liquefy metal or alloy electrodes and to maintain the high conductivity of molten salt electrolytes, bringing in some critical challenges in cell design and management due to the strong electrochemistry-thermophysics coupling regime during operation. Exploring new battery chemistries facilitates to lower the operation temperature of LMBs, and intensive efforts have been made to design new liquid alloy electrodes, molten salt electrolytes and solid ceramic electrolytes. Consequently, LMBs operated at medium temperature (100∼350 °C) and even room temperature (∼25 °C) emerge, which are rapidly developed by using alternative electrodes and electrolytes, manipulating the underlying electrochemical behavior, and engineering the electrode-electrolyte interfaces. This review systematically summarizes recent advances in representative LMBs operating from approximately 700 °C to room temperature, with a special focus on the battery chemistries and multiphysics modeling of LMBs. In the end, we provide perspectives on current challenges and future opportunities which are expected to significantly contribute to the development of LMBs towards the grid-scale energy storage application.