Oxidized multiwall carbon nanotube modified separator for high performance lithium-sulfur batteries with high sulfur loading

摘要

Recently, researchers have demonstrated that a thin conductive coating on a separator toward the cathode side of lithium-sulfur (Li-S) batteries can improve their electrochemical performance significantly. However, their experimental data are mostly based on cathodes with low sulfur mass loading, while the practical application of Li-S cells requires cathodes with high sulfur loading (>= 4 mg cm(-2)) and high sulfur content (>= 70 wt%). Thus, research on the effects of such coatings on Li-S cells with high sulfur loading is essential. Herein, we demonstrate the effectiveness of an oxidized multiwall carbon nanotube (o-MWCNT) coating (0.4 mg cm(-2)) for improving the electrochemical performance of cathodes with sulfur loading of 5.0 mg cm(-2). Due to the physical and chemical trapping of polysulfides, efficient electron conduction and fast ion transport induced by the coating, the fabricated Li-S batteries show dramatically improved specific discharge capacities of up to 925 mA h g(-1) (the areal capacity of the cathode is 4.6 mA h cm(-2)) at a current density of 100 mA g(-1) after 50 cycles; they also show good rate performance.