Black phosphorous nanosheets@CNTs hybrid composite for boosting conversion of polysulfides in lithium sulfur batteries

Abstract

Lithium sulfur batteries offer high specific energy at low cost but are hindered by the shuttle effect, which reduces capacity and cycled life due to sluggish sulfur redox kinetics. The efficient limitation of the shuttle effect of polysulfides from rational construction of electrocatalysts to accelerate the redox kinetics of polysulfides is extremely important. In this study, black phosphorous (BP) nanosheets derived commercial red phosphorous by solvothermal treatment, and modified carbon nanotubes (CNTs) hybrid materials are coated on a pristine polypropylene separator for capturing and boosting the conversion of polysulfides in lithium sulfur batteries. The one-dimensional CNTs not only promote the lithium-ions and electron pathways in redox kinetics, and two-dimensional BP nanosheets ensure the full exposure of active sites and accelerate polysulfides redox kinetics through chemisorption and catalytic conversion. Considering of these advantages mentioned above, when applied as the lithium sulfur batteries separator modifier, the cell assembled from the BP@CNTs modified separator with 4.2 mg cm⁻² sulfur loading demonstrate high specific capacity (946.1 mAh g⁻¹ at 0.3 C), and excellent cycling performance, which can maintain the capacity of 804.1 mAh g⁻¹ after 300 cycles with low-capacity decay rate of 0.05 % per cycle. Even under a high sulfur loading of 8.9 mg cm⁻², the cell can still present excellent cycling stability. This study paves the design black phosphorous modified carbonaceous materials hybrid for the construction outstanding functional separator layer and feasible synergistic approach for the inhibition of shuttle effect in lithium sulfur batteries.