Co-doped g-C3N4 nanotube decorated separators mediate polysulfide redox for high performance lithium sulfur batteries

Abstract

The main issue with lithium–sulfur (Li–S) batteries is the serious irreversible capacity loss caused by the polysulfide shuttle process. In this work, we propose an electro-catalytic strategy for absorbing and transferring long-chain polysulfides during the redox process, which is the key to improving the utilization of S. Reported here is a Co doped tubular g-C₃N₄ (CN) modified separator (Co-TCN@PP), which successfully inhibited the polysulfide shuttle by physical absorption and catalysis, thus facilitating the high utilization of S. Co-TCN with a tube-like structure ensures the uniform dispersion of Co nanoparticles, which provides abundant active sites to absorb polysulfides. Furthermore, Co-TCN exhibits fast reaction kinetics for polysulfide conversion. A Li–S battery with Co-TCN@PP achieves superior rate capacities and a long cycle life (400 times) with capacity fading as low as 0.07% per cycle at a high Li⁺ insertion/extraction rate of 2C. Moreover, electrodes with a high sulfur loading of 5.6 mg cm⁻² can be realized by adopting the Co-TCN@PP separator.