Steric Hindrance-Induced Amorphous Lithium Sulfide Deposition Accelerates Sulfur Redox Kinetics in Lithium-Sulfur Batteries.

Abstract

Lithium-sulfur (Li─S) batteries are promising candidates for next-generation energy storage due to their ultrahigh theoretical energy density. However, their practical application is severely hindered by the sluggish conversion kinetics, particularly during the crystalline lithium sulfide (Li₂S) formation stage. Herein, a steric hindrance-mediated engineering strategy is proposed that induces an amorphous Li₂S deposition process, effectively boosting the sulfur redox kinetics in Li─S batteries. By introducing benzo-15-crown-5 (B15C5) as an electrolyte additive, a strong coordination between B15C5 and lithium ion (Li⁺) is established, which creates spatial confinement around Li₂S and disrupts the crystallinity of Li₂S during its deposition. Synchrotron pair distribution function analysis combined with in situ X-ray diffraction reveals that the deposited Li₂S with B15C5 exhibits significant local disorder with irregular Li─S bond oscillations, confirming the generation of an amorphous phase. This strategy not only ensures a uniform Li₂S layer at the cathode/electrolyte interface but also lowers the energy barrier of sulfur species at the molecular scale, enabling the Li─S batteries with excellent cycling stability and overall enhanced sulfur reaction kinetics. This work provides a novel pathway for overcoming the intrinsic limitations of sluggish cathode conversion kinetics of Li─S batteries, paving the way for their practical deployment in high-performance energy storage applications.