Song Yun-Wei, Peng Yan-Qi, Zhao Meng, Lu Yang, Liu Jia-Ning, Li Bo-Quan, Zhang Qiang
Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical Engineering Tsinghua University Beijing 100084 China.
School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 China.
Small Sci. 2021 Aug 20;1(11):2100042. doi: 10.1002/smsc.202100042. eCollection 2021 Nov.
Lithium-sulfur (Li-S) batteries are highly considered for next-generation energy storage due to their ultrahigh theoretical energy density of 2600 Wh kg. The conversion reactions between lithium polysulfides (LiPSs) constitute the core process in working Li-S batteries. Electrochemical impedance spectroscopy (EIS) analysis of LiPS symmetric cells is an effective tool to provide detailed information on the LiPS conversion reactions and direct further kinetic promotion. However, reasonable interpretation of the EIS responses is so far insufficiently addressed without a well-defined equivalent circuit. Herein, a systematic analysis on the EIS responses of LiPS symmetric cells is conducted to provide a comprehensible equivalent circuit. Interfacial contact, surface reaction, and diffusion are decoupled according to their respective characteristic frequency using the distribution of relaxation time analysis method. A well-defined equivalent circuit is proposed to accurately fit the experimental EIS responses, unambiguously interpret key parameters, and be feasible with a wide range of experimental conditions. This work presents the methodology of understanding the EIS responses of LiPS symmetric cells and inspires analogous analysis on vital electrochemical processes.
锂硫（Li-S）电池因其2600 Wh kg的超高理论能量密度而被高度视为下一代储能电池。多硫化锂（LiPSs）之间的转化反应是工作中的锂硫电池的核心过程。对LiPS对称电池进行电化学阻抗谱（EIS）分析是一种有效的工具，可提供有关LiPS转化反应的详细信息并指导进一步的动力学促进。然而，在没有明确定义的等效电路的情况下，对EIS响应的合理解释目前还不够充分。在此，对LiPS对称电池的EIS响应进行了系统分析，以提供一个可理解的等效电路。使用弛豫时间分布分析方法，根据各自的特征频率将界面接触、表面反应和扩散解耦。提出了一个明确定义的等效电路，以准确拟合实验EIS响应，明确解释关键参数，并在广泛的实验条件下可行。这项工作提出了理解LiPS对称电池EIS响应的方法，并激发了对重要电化学过程的类似分析。
