A carbon nanofiber@mesoporous δ-MnO₂ nanosheet-coated separator for high-performance lithium-sulfur batteries

Hollow carbon nanofiber@mesoporous δ-MnO₂ nanosheets (HCNF@pδ-MnO₂) with large surface area composite are prepared by a facile hydrothermal method and decorated on the celgard separator as lithium polysulphides reservoir for lithium-sulfur (Li-S) batteries. In this structure, the bifunctional HCNF provides excellent electrical conductivity and physical confinement of polysulfides. The porous δ-MnO₂ coated on the wall HCNF provides more adsorption sites of polysulfides due to the large surface area. Due to the synergistic effect between HCNF and mesoporous δ-MnO₂, the Li-S batteries with simple cathode (sulfur content reach 70 wt%) structure and HCNF@δ-MnO₂ (coating thickness ≈ 2  μm) modified separator delivers an initial capacity of 1156 mA h g⁻¹ at 0.2 C and a reversible capacity of 856.1 mA h g⁻¹ after 200 cycles at 0.5 C. This result provides a simple and scalable way to improve the electrochemical property of Li-S batteries.