Separator Modified by Carbon-Encapsulated CoFe Alloy Nanoparticles Supported on Carbon Nanotubes for Advanced Lithium-Sulfur Batteries

The commercialization of lithium-sulfur (Li-S) batteries still confronts great challenges due to the sluggish redox kinetics of sulfur and the shuttle effect of lithium polysulfides. Designing a highly active electrocatalyst is an effective strategy to address the problems caused by complex multistep reactions. Herein, a hybrid composite composed of nitrogen-doped carbon-wrapped bimetallic cobalt-iron alloy nanoparticles (NC@CoFe) is derived from a Prussian blue analogue and multiwalled carbon nanotubes (CNTs), which is used as a functional coating on a separator for Li-S batteries. The cross-linked CNTs provide a robust and conductive network for quick charge transfer and sufficient active-site exposure, and the NC@CoFe nanoparticles demonstrate a strong ability for anchoring and catalytic conversion of lithium polysulfides. The specific discharge capacity of the cell with the NC@CoFe/CNT-modified separator can reach 865.4 mA h/g at 3.18 mA/cm(2) (0.5 C) and is 576.3 mA h/g after 300 cycles with a Coulombic efficiency of approximately 98.2%. The cells with a 7.4 mg/cm(2) sulfur loading display a remarkable capacity retention of 77.8% after 100 cycles. The electrocatalyst with functionalized carbonaceous adsorption and alloy nanoparticle catalysis holds substantial promise for advancing the commercialization of durable Li-S batteries.