Enhanced polysulfides conversion with hybrid bipolar membrane composed of CoSe2 and amide-functionalized CNTs composites for lithium sulfur batteries

Lithium sulfur battery has been considered as promising energy storage devices because of its superiority in energy density. However, the sulfur loading, low active material utilization, shuttle effect and torpid kinetic of polysulfides, and poor cycling stability limit its commercial applications. Herein, a hybrid bipolar membrane composed cobalt diselenide nanoparticles and amide-functionalized CNTs (CoSe2@A-CNTs) composites has been fabricated by the combination of hydrothermal and vacuum filtration technology, and contained Li2S6 catholyte for lithium sulfur batteries. The introduction of amidation functional groups enhance the polarity of the mesoporous CNTs surface and promote adsorption capability toward lithium polysulfides. The intrinsic polarity of CoSe2 nanoparticles can further adsorb the soluble polysulfides and serve as catalysts to promote the redox kinetics of polysulfides conversion. Benefiting from the synergism of physical confinement, polar chemical adsorption, and catalytic conversion, the as-prepared CoSe2@A-CNTs delivers excellent electrochemical performances at high sulfur loading. The lithium sulfur cell with CoSe2@A-CNTs membrane with 4.8 mg cm-2 sulfur loading exhibits a high initial capacity of 1009.7 mAh g-1 and excellent long-term cycling stability up to 300 cycles with a low decay rat 0.07 % per cycle at 0.2C. Remarkably, even at 9.6 mg cm-2 sulfur loading, the CoSe2@A-CNTs membrane displays high area capacity of 7.5 mAh cm-2 and maintains 6 mAh cm-2 over 100 cycles. The results show that the efficient chemical anchoring polysulfides and catalyzing redox reaction by multifunctional CoSe2@A-CNTs hybrid composites is promising for assembling with a high sulfur loading electrode, which exhibits a superior electrochemical performance in lithium sulfur batteries.