Synergistic Dual Modulation of Li₂S Redox Kinetics and Anode Stability Enabled by a High-Efficiency Organodisulfide Mediator in Anode-Free Lithium-Sulfur Batteries.

Abstract

Lithium sulfide (Li₂S) is pivotal for high-energy-density lithium-sulfur (Li─S) batteries due to its high theoretical capacity, abundant sulfur resources, and compatibility with anode-free architectures. However, its application is hindered by its intrinsically insulating nature and sluggish redox kinetics. Furthermore, traditional 1,3-dioxolane/1,2-dimethoxyethane electrolytes cannot withstand high voltages and pose safety hazards due to low flash points. Herein, we propose a synergistic strategy by introducing diisopropyl dithiocarbonate disulfide (DIP) as a multifunctional redox mediator into a high-flash-point, high-voltage-tolerant tetraethylene glycol dimethyl ether electrolyte system. DIP directly converts Li₂S to lithium polysulfides, decreasing the activation voltage of the first charge to 2.48 from 3.18 V. Simultaneously, DIP facilitates the formation of an organosulfur-rich solid electrolyte interface on the lithium surface, effectively suppressing lithium dendrite formation and growth. Crucially, this system enables stable cycling in anode-free Cu||Li₂S batteries for 160 cycles at 0.3 mAh cm^-2. Standard Li||Li₂S cells also demonstrate superior durability, achieving an extremely low per-cycle decay rate of 0.037% at 1C. Moreover, this strategy holds promise for other metal-sulfur systems, such as Na─S, K─S, Ca─S, Mg─S, and Zn─S batteries, providing a feasible path for safe, next-generation energy storage.