Effective Dual Polysulfide Rejection by a Tannic Acid/Fe^III Complex-Coated Separator in Lithium-Sulfur Batteries

The solubility behaviour of polysulfides in electrolyte solutions is a major bottleneck prior to the practical application of the lithium-sulfur battery. To address this issue, we fabricate a tannic acid/Fe^III complex-coated polypropylene (PP) separator (TA/Fe^III-PP separator) via a simple, fast, and green method. Benefiting from dual-confinement effects based on Lewis acid-base interactions between Fe^III and polysulfides as well as the dipole-dipole interactions between rich phenol groups and polysulfides, the migration of polysulfides is effectively suppressed. Meanwhile, the porous structure of the PP separator is not destroyed by an additional coating layer. Thus, the TA/Fe^III-PP separator can retain rapid lithium ion transport, eventually leading to a significant improvement in both the discharge capacity and rate performance of the corresponding lithium-sulfur cells. The cell with the TA/Fe^III-PP separator presents a low capacity fade of 0.06% per cycle over 1000 cycles at 2.0 C, along with a high Coulombic efficiency of >97% over 300 cycles at 0.5 C. With respect to the one with the bare PP separator, the cell with the TA/Fe^III-PP separator exhibits a 1.7-fold increase in the discharge capacity at 3.0 C. The proposed simple and economical approach shows great potential in constructing advanced separators to retard the shuttle effect of polysulfides for lithium-sulfur batteries.