Nickel-cobalt Cyclo-tetraphosphate decorated hollow carbon nanocages as effective polysulfide promoters for stable Lithium-Sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are promising next-generation energy storage systems. The construction of high-efficiency electrocatalysts to overcome the barriers of sluggish lithium polysulfides (LiPSs) conversion and shuttle effect is urgent. Herein, nickel–cobalt cyclo-tetraphosphate (NiCoP4O12) nanoparticles embedded in hollow carbon polyhedrons are elaborately prepared and used as excellent polysulfide promoters in LSBs. The well-controlled core–shell structure physically blocks and strongly captures LiPSs, thereby boosting LiPSs conversion kinetics over the large exposed NiCoP4O12 active sites. Meanwhile, the carbon matrix build a conductive network that enables high-speed electron and ion transport, thus forming a rapid and robust “capture-diffusion-transformation” network. As a result, the assembled S@NiCoP4O12 cathode delivers an excellent rate capacity (518.7 mAh g−1 at 5 C), impressive stability (a small capacity decay of 0.0396 % per cycle over 1500 cycles at 1 C), and favorable durability of thick sulfur cathodes under lean electrolyte condition (with 4.13 mg cm−2 sulfur loading and 5.0 µL mg−1 electrolyte) over 120 cycles.