Dual-Regulation Strategy to Improve Anchoring and Conversion of Polysulfides in Lithium-Sulfur Batteries.

The sluggish reaction kinetics at the cathode/electrolyte interface of lithium-sulfur (Li-S) batteries limits their commercialization. Herein, we show that a dual-regulation system of iron phthalocyanine (FePc) and octafluoronaphthalene (OFN) decorated on graphene (Gh), denoted as Gh/FePc+OFN, accelerates the interfacial reaction kinetics of lithium polysulfides (LiPSs). Multiple in-situ spectroscopy techniques, ex-situ X-ray photoelectron spectroscopy combined with density functional theory calculations demonstrate that FePc acts as an efficient anchor and scissor for the LiPSs through Fe∙∙∙S coordination, mainly facilitating their liquid-liquid transformation, whereas OFN enables Li-bond interaction with the LiPSs, accelerating the kinetics of the liquid-solid nucleation and growth of Li2S. This dual-regulation system promotes the smooth conversion reaction of sulfur, thereby improving the battery performance. A Gh/FePc+OFN-based Li-S cathode delivered an ultrahigh initial capacity of 1604 mAh g-1 at 0.2 C, with an ultralow capacity decay rate of 0.055% per cycle at 1 C over 1000 cycles.