Stabilizing dual-cation liquid metal battery for large-scale energy storage: A comprehensive hybrid design approach

Liquid metal batteries (LMBs) hold immense promise for large-scale energy storage. However, normally LMBs are based on single type of cations (e.g., Ca²⁺, Li⁺, Na⁺), and as a result subject to inherent limitations associated with each type of single cation, such as the low energy density in Ca-based LMBs, the high energy cost in Li-based LMBs, and the short cycling lifespan in Na-based LMBs. Here we propose a dual-cation (Ca²⁺ and Li⁺) liquid metal battery, which allows access to, simultaneously, high energy density, prolonged cycling lifespan, reduced energy cost, and enhanced cycling stability. For this strategy to work, the main obstacle to overcome is the instability of the dual-cation system in electrochemical reactions. We have undertaken a hybrid design approach to resolve this issue, by integrating phase diagram design, first-principles calculations, and machine learning techniques. We discover that incorporating magnesium as an inert additive can effectively stabilize the cycling performance of dual-cation LMBs. Furthermore, our results reveal that specific ion ratios are required to release tailor dual-cation chemistry, to enable the designed multi-component alloy (Ca-Li-Mg in our case) electrode to function properly in LMBs. These findings are expected to have general implications for future developments of innovative LMBs with enhanced performance.