I somehow learned about this stuff 3 years ago, and like to keep tabs on it. In bold below is what caught my attention.
The liquid metal battery (LMB) project seeks to develop a low cost and long lifespan battery for grid-scale stationary energy storage. The battery utilizes three liquid layers as the electroactive components, including a liquid metal positive electrode, a fused salt electrolyte, and a liquid metal negative electrode. The three liquid layers float on top of one another due on their density differences and immiscibility, promising low assembly cost with use of inexpensive materials. Furthermore, liquid electrodes avoid common failure mechanisms of solid-state battery components, potentially enabling a long lifespan device. Current research efforts encompass a wide range of scientific topics and engineering challenges, including fundamental thermodynamic measurements of candidate electrode couples, computational thermal modeling, electrochemical studies of molten salt electrolytes, long term corrosion and lifespan testing, testing and characterization of complete single-cell batteries, and scaling up the design to build larger single-cells.
Source: Liquid Metal Batteries