Self-healing action of Bi in high-performance Sb–Bi–Sn positive electrodes for liquid metal batteries

Li||Sb–Bi–Sn liquid metal batteries (LMBs) have comprehensive advantages of a high energy density, excellent rate capability, low material costs, and high cycle performance. However, the corrosion of the positive electrode to the current collector at high temperatures cannot be neglected over the long term. Here, we investigate the corrosion behavior of SS304 in two types of Sb–Bi–Sn alloys under static and cell cycling conditions. Interestingly, we find that the cell performance of Li||Sb–Bi–Sn LMBs are not affected by corrosion between the positive electrode and stainless-steel current collector. The corrosion products and their participation in the cell reaction process are determined using ex situ analyses and electrochemical measurements. Bi not only inhibits the dissolution of SS304 in Sb–Bi–Sn alloy but also spontaneously promotes the decomposition of Fe–Sb and Fe–Cr–Sb corrosion products during lithiation, releasing the active component Sb, and Sb–Bi–Sn alloy is recovered. Encouragingly, even in the event of corrosion, the cell capacity, efficiency, and cycle stability remain almost unaffected due to this self-healing action of Bi. This study represents a new direction toward inhibiting the corrosion of positive electrode and stabilizing cell performance for practical application and commercialization by alloying.