Reconstructing interfacial electric double layer for efficient sulfur conversion reaction in aqueous zinc sulfur batteries
Jie Lei, Jiandong Lin, Yinze Zuo, Yong Yan, Lu Yue, Rongxin Gao, Peining Lin, Mingquan Liu, Hao Yan, Wei‐Bin Yan, Jiujun Zhang
Abstract
Aqueous zinc sulfur batteries promise low−cost and safe grid−scale energy storage, but face challenges due to sluggish interfacial Zn2+ transfer and H2O−induced ZnS disproportionation reactions at the interface of sulfur positive electrode. Here, we develop a hybrid electrolyte by introducing ZnI2 and organic N,N−dimethylformamide cosolvent, in which iodide species contribute to catalytic oxidation of ZnS, while N,N−dimethylformamide cosolvent can effectively facilitate sulfur reduction reaction. By combining operando Raman spectroscopy with non−destructive electrochemical impedance spectroscopy and theoretical calculations/simulations, it demonstrates that N,N−dimethylformamide molecules preferentially adsorb on sulfur electrode surface and strongly interact with Zn2+, thereby reconstructing interfacial electric double layer with H2O−poor inner Helmholtz plane and Zn2+−rich outer Helmholtz plane, which not only favors interfacial Zn2+ transfer to promote sulfur conversion reaction, but also suppresses H2O−induced side reactions. Through an additional constant voltage charge procedure to avoid I−/I3− redox shuttle, the assembled Zn||S batteries can exhibit a voltage hysteresis of 0.326 V and a long−term cycling stability with a capacity fading of 0.034% per cycle after 1000 cycles at 2 C (i.e., 3.34 A g−1), even enabling a high areal capacity of 7.68 mAh cm−2 and a stable low−temperature performance with a specific capacity of 500 mAh g−1 at −10 °C. Aqueous Zn||S battery is mainly limited by irreversible sulfur positive electrode. Here, authors develop a hybrid electrolyte to reconstruct interfacial electric double layer with rapid Zn2+ transfer and inhibited side reactions, thereby achieving efficient and reversible sulfur conversion reaction.