Feasibility Research of SS304 Serving as the Positive Current Collector of Li||Sb–Sn Liquid Metal Batteries

Liquid metal batteries are an emerging and promising large-scale electrochemical energy-storage technology, the corrosion of which is a significant issue due to their high-operating temperature environment and an all-liquid structure. Herein, we have comprehensively investigated the corrosion behavior of SS304 in the Sb–Sn alloy under static conditions and cell-cycling conditions. The corrosion mechanism and the battery reaction process are clarified on the basis of electrochemical measurements and ex situ analyses. Fe and Ni of SS304 are considered to dissolve easily in the liquid Sb–Sn alloy rather than Cr, forming the Fe–Ni–Sb–Sn corrosion products. Due to corrosion, changes in the composition of the positive electrode cause an abnormal discharge voltage plateau and capacity fading. The appearance of low-discharge voltage plateau is mainly dominated by the reaction of Fe–Sb with Li. Sn in the positive electrode promotes the diffusion of dissolved elements and accelerates the corrosion of the current collector. This work concludes that Fe- and Ni-based alloys such as stainless steel are not promising positive current collectors of Li||Sb–Sn liquid metal batteries. It enlightens us to further find a conductive and corrosion-resistant protective coating or optimize the composition of the positive electrode.