Two birds with one stone: ultrafine Fe₃O₄ nanocrystals functionalized sandwich-like separator for high-efficiency lithium-sulfur full batteries

Lithium−sulfur (Li-S) batteries encounter significant challenges, including the notorious shuttle effect of lithium polysulfide (LiPS) from the S cathode and the uncontrollable lithium dendrite growth at the metal anode.To address these issues, herein, we present an innovative separator. By modifying both sides of a polypropylene (PP) membrane with Fe₃O₄/rGO, constructing a sandwhich-like structured separator capable of simultaneously tackling the challenges associated with the S cathode and the Li mental anode. The Fe₃O₄/rGO composite consists of ultrafine Fe₃O₄ nanocrystals anchored on rGO nanosheets deliver exceptional catalytic efficiency for LiPSs conversion.This catalytic activity, coupled with abundant active sites enabling strong LiPSs chemisorption and reduced nucleation barrier for Li2S deposition, effectively combats the shuttle effect. Moreover, the Fe₃O₄/rGO on the anode side significantly enhances the homogeneous Li⁺ flux across the Li surface, promoting uniform Li plating/stripping. Kinetics analysis and theoretical calculations reveal concurrent improvement of S cathode and Li mental anode is achieved through the excellent “sulfiphilic” and “lithiophilic” properties of Fe₃O₄. Thus, the Li-S “full cell” exhibits exceptional capability, including high sulfur utilization, (1207.4 mAh g^-1 at 0.1 C), excellent cycling stability (maintaining stablility for over 400 cycles at 2 C with a capacity decay rate of 0.1% per cycle ), and splendid rate performance (604 mAh g^-1 at 3 C). A low-cost, sandwich-like for excellent Li-S batteries is demonstrated in this work.