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

Abstract

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.