MXene/Carbon Nanotube/Poly(ethylene oxide) Heterostructured Interface for Polysulfide Regulation in Lithium-Sulfur...

Lithium-sulfur (Li-S) batteries are promising next-generation energy-storage systems but are severely hindered by polysulfide shuttling, sluggish sulfur redox kinetics, and unstable Li₂S nucleation/growth behavior. Herein, a multifunctional MXene/carbon nanotube/poly(ethylene oxide) (MX/CNT/PEO)-modified separator is developed to regulate polysulfide behavior and improve interfacial electrochemical stability. In this composite architecture, MXene provides polar sites for lithium polysulfide adsorption, while carbon nanotubes construct interconnected conductive networks and suppress MXene restacking. The incorporation of poly(ethylene oxide) improves interfacial continuity and introduces additional oxygen-containing functionalities within the composite framework. Benefiting from the integrated effects of polar adsorption, conductive pathways, and structural integration, the MX/CNT/PEO-modified separator effectively suppresses polysulfide diffusion, reduces charge-transfer resistance, and promotes more favorable Li₂S nucleation/growth behavior. Electrochemical analysis shows that the charge-transfer resistance decreases from 175.9 Ω for pristine PP to 15.7 Ω for the MX/CNT/PEO@PP separator, corresponding to a 91.1% reduction. Potentiostatic Li₂S deposition analysis further supports favorable Li₂S nucleation/growth behavior on the MX/CNT/PEO-modified interface, after background subtraction. As a result, the Li-S cell with the MX/CNT/PEO@PP separator delivers a high initial discharge capacity of 1613 mAh g^-1 at 0.1 C and maintains average capacities of 1331.1 and 803.1 mAh g^-1 at 0.1 and 2 C during rate testing, respectively. During long-term cycling at 2 C, the cell retains 319.3 mAh g^-1 after 1000 cycles, with an average capacity decay rate of 0.064% per cycle. This work provides a rational composite-interlayer design strategy for multifunctional separator materials in high-performance Li-S batteries.