Facile synthesis of hierarchically γ-Al2O3@C yolk-shell microspheres for lithium-sulfur batteries

The practical application of lithium-sulfur batteries (LSBs) remains restricted because of a severe polysulfide-shuttle effect and the insulating nature of sulfur. In this work, a kind of unique γ-Al2O3@C yolk-shell microspheres comprising carbon coating on the γ-Al2O3 yolk-shell microspheres were synthesized using organic adsorpting and in-situ thermal reduction methods, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). It was demonstrated that the γ-Al2O3@C yolk-shell microspheres could encapsulate the polysulfides and increase the sulfur utilization. Accordingly, γ-Al2O3@C yolk-shell microspheres cathode achieved high initial discharge capacity of 1046.9 mAh g−1, excellent discharge capacity (765.5 mAh g−1) after 70 cycles (the capacity retention was about 73%) and superior rate performance. In addition, the appropriate C content was proved to be an important factor in the influence of electrochemical performances. Hence, our present method paves a new path to improve the performance of LiS batteries.