Metalloporphyrin conjugated porous polymer in-situ grown on a Celgard separator as multifunctional polysulfide barrier and catalyst for high-performance Li-S batteries

Abstract

The severe shuttling of soluble polysulfides (LiPSs) (Li2Sx, 4 ≤ x ≤ 8) and sluggish kinetics of solid–solid conversion (Li2S2 → Li2S), lead to the premature end of discharge, resulting in fast capacity decay, limiting the practical performance and safety of lithium-sulfur batteries (LSBs). Functional modifiers on separators exhibit significant performances in migrating diffusion and promoting conversion for LiPSs; thus, endowing the separator with multiple high-performance parameters by multifactorial engineering to address the two issues mentioned above is an urgent need. Herein, for the first time, an ultra-light (≈0.14 mg cm−2) and multifunctional modifier consisting of metalloporphyrin conjugated porous polymer (Al-CPP) is interface-induced growth on the commercial separator to develop advanced LSBs. The electrocatalyst of metalloporphyrin is covalently constructed by an imidazolium-containing linker with bis(trifluoromethane)sulfonimide (TFSI−) anions within the porous skeleton, improving diffusion and conversion of LiPSs as well as facilitating electrolyte accessibility and Li+ transport, thereby performing enhanced full-range sulfur redox kinetics, and guiding uniform Li deposition. The in-situ growth of metalloporphyrin conjugated porous polymer is further verified in LSBs that realize superior rate performances and long lifespans. This contribution proposes an efficient in-situ growth of an ultra-light modifier design strategy to functionalize separators and inspires multi-function synergetic integration facing high-performance LSBs.