Lithium-sulfur (Li-S) batteries have been disclosed as one of the most promising energy storage systems. However, the low utilization of sulfur, the detrimental shuttling behavior of polysulfides, and the sluggish kinetics in electrochemical processes, severely impede their application. Herein, 3D hierarchical nitrogen-doped carbon nanosheets/molybdenum phosphide nanocrystal hollow nanospheres (MoP@C/N HCSs) are introduced to Li-S batteries via decorating commercial separators to inhibit polysulfides diffusion. It acts not only as a polysulfides immobilizer to provide strong physical trapping and chemical anchoring toward polysulfides, but also as an electrocatalyst to accelerate the kinetics of the polysulfides redox reaction, and to lower the Li2 S nucleation/dissolution interfacial energy barrier and self-discharge capacity loss in working Li-S batteries, simultaneously. As a result, the Li-S batteries with MoP@C/N HCS-modified separators show superior rate capability (920 mAh g-1 at 2 C) and stable cycling life with only 0.04% capacity decay per cycle over 500 cycles at 1 C with nearly 100% Coulombic efficiency. Furthermore, the Li-S battery can achieve a high area capacity of 5.1 mAh cm-2 with satisfied capacity retention when the cathode loading reaches 5.5 mg cm-2 . This work offers a brand new guidance for rational separator design into the energy chemistry of high-stable Li-S batteries.
Keywords: electrocatalysis; lithium sulfide nucleation/dissolution; lithium-sulfur chemistry; molybdenum phosphide; nitrogen-doped carbon nanosheets.
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.