Synergetic catalytic regulation of nitrogen doped NiS2/CoS2 heterostructure for polysulfide immobilization in Li-S batteries

Abstract

The sluggish kinetics of sulfur species conversion and the shuttle effect in lithium-sulfur batteries are severely hindered in practical applications. Herein, we propose nitrogen doped NiS2/CoS2 heterostructure supported on CNT (N-NiS2/CoS2/CNT) by simple thiourea pyrolysis served as electrocatalyst functionalized on PP separator. The new formed M-N bonds on N-NiS2/CoS2/CNT motivate the catalytic activity of metal active centers strengthening the chemical anchoring towards polysulfides and Li2S electrodeposition behavior. The N,S dual doping on CNT support synergistically affords the electrochemical active sites for polysulfides conversion kinetics and increases the electrical conductivity of the whole catalyst. In Li-S batteries, the initial capacity of the battery with N-NiS2/CoS2/CNT functionalized separators reaches 1317.3 mAh g−1 at 0.2 C, and after 200 cycles, the capacity reaches 939.5 mAh g−1 with a capacity retention rate of 59.8%. Even at a large multiplicity rate of 2 C, the capacity can still be maintained at 552.2 mAh g−1 with a low-capacity decay of 0.068% after 500 cycles.