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.