Natural Polyphenol-Reinforced Ion-Selective Separators for High-Performance Lithium-Sulfur Batteries with High Sulfur Loading and Lean Electrolyte

Ion-selective separators are promising to inhibit soluble intermediates shuttle in practical lithium-sulfur (Li−S) batteries. However, designing and fabricating such high-performance ion-selective separators using cost-effective, eco-friendly, and versatile methods remains a formidable challenge. Here we present ion-selective separators fabricated via the spontaneous deposition of green tea-derived polyphenols onto a polypropylene separator, aimed at enhancing the stability of Li−S batteries. The resulting natural polyphenol-reinforced ion-selective (NPRIS24) separators exhibit rapid Li ion transport and high soluble intermediates inhibition capability with an ultralow shuttle rate of 0.67 % for Li₂S₄, 0.19 % for Li₂S₆ and 0.10 % for Li₂S₈. This superior ion-selectivity arises from the high electronegativity and strong lithiophilic nature of the phenolic compounds. Consequently, we have achieved high-performance Li−S batteries that are steadily cyclable under the challenging conditions of an S loading of 5.7 mg cm⁻², an electrolyte-to-S ratio of 5.1 μL mg⁻¹, and a 50 μm Li foil anode. Furthermore, the NPRIS24 separator enhances the performance of other Li metal batteries utilizing commercial LiFePO₄ (5.3 mg cm⁻²) and LiNi_0.5Co_0.2Mn_0.3O₂ (9.9 mg cm⁻²) cathodes. This work underscores the potential of utilizing natural polyphenols for the design of advanced ion-selective separators in energy storage systems.