High-Performance Antimony–Bismuth–Tin Positive Electrode for Liquid Metal Battery

The liquid metal battery (LMB) is an attractive chemistry for grid-scale energy-storage applications. The full-liquid feature significantly reduces the interface resistance between electrode and electrolyte, endowing LMB with attractive kinetics and transport properties. Achieving a high energy density still remains a big challenge. Herein, we report a low-melting-point antimony–bismuth-tin positive electrode for LMB with high energy density and excellent rate performance for the first time. The electromotive force of Li||Sb–Bi–Sn system is determined by Li||Sb and Li||Bi chemistries. The Sn component plays a bifunctional role in the chemistry, decreasing the melting point of Sb–Bi–Sn alloy and providing rapid lithium diffusion paths for the electrode reaction. The ternary feature of the positive electrode ensures a low Sn concentration for the eutectic requirement of the positive electrode working at moderate temperature (500 °C). The stepwise reaction characteristics of Sb and Bi provides a dynamic microstructure change of intermediate compounds during the charge/discharge process, allowing the electrolyte to penetrate and make contact with the positive electrode to enable a fast electrode reaction. A synergetic combination of these advantages enables the reported Sb–Bi–Sn electrode to demonstrate a high energy density of about 260 Wh kg–1 and excellent rate capability with almost no capacity degradation at different current densities from 200 to 1200 mA cm–2. All these excellent properties demonstrate that the Sb–Bi–Sn alloy is an ideal positive electrode of LMB for large-scale applications.