This article presents an innovative approach to monitor working redox flow batteries using dynamic electrochemical impedance spectroscopy, diverging from the commonly sequential impedance methods carried out under potentiostatic or galvanostatic conditions close to the open circle voltage. The authors introduce a fresh variation of dynamic impedance measurement that leverages an amplitude-modulated multi-frequency alternating current perturbation signal. This technique leads to a reduction in measurement time, making it possible to monitor impedance in real-time under typical operational conditions. Consequently, it effectively addresses the limitations stemming from the absence of stationary conditions during impedance measurements. There is no doubt that measurement techniques enabling the study of processes during the operational life of a battery provide the most valuable insights into the properties of these systems. The potential of this proposed approach is exemplified through the examination of a full vanadium redox flow battery as a case study. Classical impedance measurements were also conducted under potentiostatic and galvanostatic conditions with sequential frequency signal change, which requires stopping the battery operation, resulting in electrode potential changes of over 200 mV compared to the working system. Spectra for all modes of measurements were compared. In the case of dynamic measurements, such significant differences in spectra during charging and discharging are not observed, which is characteristic of classical measurements. The authors deliberately and consciously refrain from analyzing the results by fitting equivalent circuits.

中文翻译：

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全钒氧化还原液流电池电化学阻抗谱测量的三种模式

本文提出了一种使用动态电化学阻抗谱监测工作氧化还原液流电池的创新方法，该方法不同于在接近开环电压的恒电位或恒电流条件下进行的常见顺序阻抗方法。作者介绍了动态阻抗测量的一种新变化，该变化利用调幅多频交流电扰动信号。该技术可以减少测量时间，从而可以在典型操作条件下实时监测阻抗。因此，它有效地解决了阻抗测量过程中缺乏静态条件所带来的限制。毫无疑问，测量技术能够研究电池使用寿命期间的过程，为了解这些系统的特性提供了最有价值的见解。通过检查全钒氧化还原液流电池作为案例研究，例证了该方法的潜力。经典阻抗测量也在恒电位和恒电流条件下进行，频率信号连续变化，这需要停止电池运行，导致与工作系统相比电极电位变化超过 200 mV。比较了所有测量模式的光谱。在动态测量的情况下，在充电和放电期间没有观察到光谱的显着差异，这是经典测量的特征。作者有意识地避免通过拟合等效电路来分析结果。