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

Abstract

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/cm2 (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/cm2 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.