Two Birds with One Stone: Ultrafine Fe3o4 Nanocrystals Functionalized Sandwich-Like Separator for High-Efficiency Lithium-Sulfur Full Batteries

Abstract

Lithium−sulfur (Li-S) batteries face great challenges of notorious shuttling effect of lithium polysulfide (LiPS) from the S cathode and uncontrollable growth of lithium dendrites from Li metal anode. Herein, we developed a novel symmetrical sandwiched-like separator with Fe3O4/reduced graphene oxide (Fe3O4/rGO) decorated on both sides of the polypropylene (PP) membrane to solve the issues from the cathode and anode simultaneously. The Fe3O4/rGO consists of ultrafine Fe3O4 nanocrystals anchoring on rGO nanosheets, exposing abundant active sites for strong chemisorption of LiPSs, high catalytic activity for LiPSs conversion, and low nucleation barrier for Li2S deposition. Moreover, the Fe3O4/rGO on the anode side significantly enhance homogeneous Li+ flux along the Li surface and guide uniform Li plating/stripping at the anode side. Kinetics analysis and theoretical calculation reveal the great “sulfiphilic” and “lithiophilic” properties of Fe3O4, significantly optimizing the performance from both the S cathode and Li anode. Thus, the Li-S “full cell” exhibits high sulfur utilization (1207.4 mAh g-1 at 0.1 C), excellent rate capability (604.4 mAh g-1 at 3 C), and stable cycling performance (0.1% capacity decay per cycle over 400 cycles).

Keywords: lithium-sulfur battery, separator modification, ultrafine Fe3O4 nanocrystals, sulfur cathode, lithium metal anode