Iron (Fe, Ni, Co)-based transition metal compounds for lithium-sulfur batteries: Mechanism, progress and prospects

Lithium-sulfur batteries (LSBs) have a high theoretical capacity, which is considered as one of the most promising high-energy–density secondary batteries due to the double electrons reaction of sulfur. However, the shuttle effects of lithium polysulfides (LiPSs) and sluggish redox kinetics lead to their materials capacity loss and cycle stability deterioration, which restrains LSBs commercialization. Metallic compounds as additions can improve the electrochemical performance of the Li–S system, through the trap of LiPSs and accelerate the conversion of the soluble LiPSs. Among of them, the iron group elements (Fe, Ni, Co)-based compounds are the promising materials for the LSBs, due to their unique outer electronic structure and its tunable properties, low cost, abundant in the earth, environmental benignity, controllable and scalable prepared, and so on. In this review, we have made a summary for iron-based compounds to capture LiPSs according to lithium bond, sulfur bond and magnetic force. The type of iron-based compound including oxides, sulfides, nitrides, phosphides, carbides, and so on, and we have investigated the electrocatalytic mechanism of these materials. Besides, some improvement strategies are proposed, such as the engineering of the special micro/nanostructure, defect concentrations, band structures, and heterostructures. We hope to shed an in-depth light on the rationally design and fabrication of robust, commercial and stable materials for high-performance LSBs.