Battery Separators Functionalized with Edge-Rich MoS2/C Hollow Microspheres for the Uniform Deposition of Li2S in High-Performance Lithium–Sulfur Batteries

As promising energy storage systems, lithium–sulfur (Li–S) batteries have attracted significant attention because of their ultra-high energy densities. However, Li–S battery suffers problems related to the complex phase conversion that occurs during the charge–discharge process, particularly the deposition of solid Li2S from the liquid-phase polysulfides, which greatly limits its practical application. In this paper, edge-rich MoS2/C hollow microspheres (Edg-MoS2/C HMs) were designed and used to functionalize separator for Li–S battery, resulting in the uniform deposition of Li2S. The microspheres were fabricated through the facile hydrothermal treatment of MoO3–aniline nanowires and a subsequent carbonization process. The obtained Edg-MoS2/C HMs have a strong chemical absorption capability and high density of Li2S binding sites, and exhibit excellent electrocatalytic performance and can effectively hinder the polysulfide shuttle effect and guide the uniform nucleation and growth of Li2S. Furthermore, we demonstrate that the Edg-MoS2/C HMs can effectively regulate the deposition of Li2S and significantly improve the reversibility of the phase conversion of the active sulfur species, especially at high sulfur loadings and high C-rates. As a result, a cell containing a separator functionalized with Edg-MoS2/C HMs exhibited an initial discharge capacity of 935 mAh g−1 at 1.0 C and maintained a capacity of 494 mAh g−1 after 1000 cycles with a sulfur loading of 1.7 mg cm−2. Impressively, at a high sulfur loading of 6.1 mg cm−2 and high rate of 0.5 C, the cell still delivered a high reversible discharge capacity of 478 mAh g−1 after 300 cycles. This work provides fresh insights into energy storage systems related to complex phase conversions.