NiCo2S4 yolk-shell hollow spheres with physical and chemical interaction toward polysulfides for advanced lithium-sulfur batteries

Lithium-sulfur (Li-S) battery attracts significant attention as the next-generation battery candidate due to its considerable theoretical energy density. However, the shuttle effect of polysulfides and relatively slow reaction kinetics of sulfur cathode severely hinder the commercial applications of the Li-S battery. Herein, we report NiCo2S4 yolk-shell hollow spheres used as an ideal sulfur host in Li-S battery for the first time. Benefiting from the unique yolk-shell hollow sphere structure and the bimetal sulfide component, the as-synthesized NiCo2S4 yolk-shell hollow spheres cannot only effectively physically absorb the polysulfides but also facilitate the polysulfides conversion. Accordingly, the cathode of S/NiCo2S4 composite with 70 wt% sulfur delivers notable cyclic stability up to 500 cycles at 0.5 C with a capacity decay rate of only 0.074% per cycle. Therefore, this unique NiCo2S4 yolk-shell hollow sphere could be considered an efficient sulfur host material candidate for high-energy density Li-S batteries.