美国加州大学Duan, Xiangfeng团队报道了16电子硫还原反应网络的建立。相关研究成果于2024年1月31日发表于国际一流学术期刊《自然》。

硫还原反应（SRR）在大容量锂硫（Li-S）电池中起着核心作用。SRR涉及复杂的16电子转化过程，具有多个多硫化锂中间体和反应分支。建立复杂的反应网络对于合理调整改进型锂硫电池的SRR至关重要，但这是一个艰巨的挑战。

该文中，研究人员系统地研究了电催化SRR，以使用氮、硫、双掺杂多孔石墨烯框架作为模型电极来破译其反应网络，以了解电催化剂在加速转化动力学中的作用。综合循环伏安法、原位拉曼光谱和密度泛函理论计算，研究人员在不同电位下识别并直接表征了关键中间体（S₈、Li₂S₈、Li₂S₆、Li₂S₄和Li₂S），并阐明了它们的转化途径。主要观察到Li₂S₄和Li₂S₆，其中Li₂S₄代表决定整个SRR动力学的关键电化学中间体。

通过歧化反应产生（消耗）的Li₂S₆不直接参与电化学反应，但对多硫化物穿梭过程有显著贡献。研究发现，氮、硫双掺杂多孔石墨烯骨架催化剂可以帮助加速多硫化物转化动力学，导致可溶性多硫化物锂在更高电势下更快地耗尽，从而减轻多硫化物穿梭效应并提高输出电势。

研究结果突出表明，电催化方法是解决锂硫电池基本挑战的一种有前途的策略。

附：英文原文

Title: Establishing reaction networks in the 16-electron sulfur reduction reaction

Author: Liu, Rongli, Wei, Ziyang, Peng, Lele, Zhang, Leyuan, Zohar, Arava, Schoeppner, Rachel, Wang, Peiqi, Wan, Chengzhang, Zhu, Dan, Liu, Haotian, Wang, Zhaozong, Tolbert, Sarah H., Dunn, Bruce, Huang, Yu, Sautet, Philippe, Duan, Xiangfeng

Issue&Volume: 2024-01-31

Abstract: The sulfur reduction reaction (SRR) plays a central role in high-capacity lithium sulfur (Li-S) batteries. The SRR involves an intricate, 16-electron conversion process featuring multiple lithium polysulfide intermediates and reaction branches1,2,3. Establishing the complex reaction network is essential for rational tailoring of the SRR for improved Li-S batteries, but represents a daunting challenge4,5,6. Herein we systematically investigate the electrocatalytic SRR to decipher its network using the nitrogen, sulfur, dual-doped holey graphene framework as a model electrode to understand the role of electrocatalysts in acceleration of conversion kinetics. Combining cyclic voltammetry, in situ Raman spectroscopy and density functional theory calculations, we identify and directly profile the key intermediates (S8, Li2S8, Li2S6, Li2S4 and Li2S) at varying potentials and elucidate their conversion pathways. Li2S4 and Li2S6 were predominantly observed, in which Li2S4 represents the key electrochemical intermediate dictating the overall SRR kinetics. Li2S6, generated (consumed) through a comproportionation (disproportionation) reaction, does not directly participate in electrochemical reactions but significantly contributes to the polysulfide shuttling process. We found that the nitrogen, sulfur dual-doped holey graphene framework catalyst could help accelerate polysulfide conversion kinetics, leading to faster depletion of soluble lithium polysulfides at higher potential and hence mitigating the polysulfide shuttling effect and boosting output potential. These results highlight the electrocatalytic approach as a promising strategy for tackling the fundamental challenges regarding Li-S batteries.

DOI: 10.1038/s41586-023-06918-4

Source: https://www.nature.com/articles/s41586-023-06918-4