Enhanced cycling stability in Li-S batteries: CR-CTA modified GF separators with mechanistic insights and performance evaluation

Lithium-sulfur (Li-S) batteries offer high theoretical energy density but face challenges like polysulfide dissolution and poor cycling stability. This study presents an innovative approach to improving Li-S battery performance by modifying glass fiber (GF) separators with a compound (CR-CTA) prepared from Congo Red (CR), a redox-active organic compound, and cetyltrimethylammonium bromide (CTAB), a cationic surfactant. The CR-CTA/SP/PVP-modified GF separator significantly enhances electrochemical properties, cycling stability, and ion transport, reducing the polysulfide shuttle effect and improving sulfur utilization. A Li-S battery using the CR-CTA/SP/PVP-modified GF separator achieved an initial capacity of 1153 mAh g −1 and retained 994 mAh g −1 (86.2 %) after 300 cycles at 0.5C. These results suggest that redox-active molecules like CR can serve as effective functional additives for separator modification, paving the way for high-performance energy storage devices. • CR-CTA-modified GF separator enhances Li-S battery cycling stability. • Innovative CR-CTA compound mitigates polysulfide shuttle effect in Li-S batteries. • Significant boost in sulfur utilization and long-term cycling efficiency. • Dual-modified separator shows 85.6 % capacity retention after 300 cycles. • Redox-active CR in separator improves ion transport and battery performance.