Regulating the electrode-electrolyte interface in Li-S batteries with 2,5-dimercapto-1,3,4-thiadiazole additives

The commercialization of Li-S batteries is constrained by the unstable interface, severe shuttle of polysulfides, and sluggish kinetic conversion reactions. Electrolyte regulation is a straightforward and efficient way to tackle those mentioned issues. Herein, a multifunctional electrolyte additive of 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) is introduced in the ether-based electrolyte, which can be lithiated into Li₂-DMTD when contacted with the Li or Li₂S during the discharge process. The generated Li₂-DMTD can operate as a highly ionic-conducting protective coating on the Li surface, inhibiting the formation of Li dendrites, and increasing interface stability. Then, it is reversibly oligomerized with Li₂S, forming two organosulfur oligomers during the ensuing electrochemical process. Such a modified reaction routine can reduce the shuttle effect and speed up the reaction kinetics of Li₂S at the cathode, preventing cathode passivation and boosting active material utilization. As a result, The Li||Li symmetric cells with DMTD exhibit about 5-fold cycle life than the reference cell under 5 mA cm⁻² current density. Meanwhile, the initial charge voltage of Li||Li₂S battery is greatly decreased from 3.7 V to 3.0 V with DMTD, and the assembled Li-S cell shows an improved capacity retention from 45.7 % to 81.2 % after 320 cycles. Therefore, this work successfully tackled the critical issues by designing functional organosulfur electrolyte additives in LSBs, which provides theoretical guidance for the electrolyte design in LSBs.