Sublimed sulfur powders as novel effective anode additives to enhance the high-rate capabilities of iron anodes for advanced iron-based secondary batteries

Owing to the passivation behavior of iron anode, alkaline iron-based rechargeable batteries usually show very poor high rate performance (below 1.0C), which seriously restricts their widespread commercial deployment. In this work, for the first time, we demonstrate that sublimed sulfur can be used as a novel, cheap and effective anode additive to significantly enhance the high-rate performance of iron-based battery. Influences of S additive on the electrochemical performances of iron anode are investigated systemically. Moreover, the possible mechanism of sublimed sulfur is further investigated. It is interestingly discovered that the adding method and adding content of S has greatly affected the final performance of the iron electrode. The Fe3O4 +10 wt.%S mixing electrode can be charged at 2C and discharged at the rate as high as 5C with a discharge capacity of ～430 mAh g−1. The significant enhancement of high rate performance can be ascribed to that sublimed sulfur can not only provide sustained supply of sulfur ions during cycling but also act as a pore-former to modify the porosity of iron electrode to form a beneficial porous electrode structure. Therefore, it is believed that sublimed sulfur is a promising, highly efficient anode additive for advanced iron-based batteries.