Tg-C3N4-coated functional separator as polysulfide barrier of high-performance lithium-sulfur batteries

Abstract

Lithium sulfur (Li-S) battery is considered as a promising alternative for the development of battery technologies. However, the shuttle effect seriously limits its practical use. Herein, hollow tubular graphene-like carbon nitride (Tg-C3N4) is synthesized and utilized as a functional interlayer to inhibit shuttling effect and promote catalytic kinetics. Both experiments and DFT calculations together suggest that N-doping enhances the electron transfers between Tg-C3N4 and LiPSs, leading to improved chemical adsorptions and catalytic effects towards the redox conversions of the active sulfur species. Besides, Tg-C3N4 delivers a unique hollow tubular architecture with massive ion transfer pathways and fully exposed active interfaces. In addition, the abundant C–N heteroatomic structures also impose strong chemical immobilization toward lithium polysulfides. Benefiting from these unique superiorities, the cell with the Tg-C3N4-modified separator exhibits a reversible capacity of 494 mAh g−1 after 500 cycles at 1 C with a negligible capacity decay of 0.085% per cycle, indicating an efficient strategy toward high-performance modified separators.