Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea.
Department of Material Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
Proc Natl Acad Sci U S A. 2022 Mar 1;119(9). doi: 10.1073/pnas.2114947119.
Redox flow batteries (RFBs) are attractive large-scale energy storage techniques, achieving remarkable progress in performance enhancement for the last decades. Nevertheless, an in-depth understanding of the reaction mechanism still remains challenging due to its unique operation mechanism, where electrochemistry and hydrodynamics simultaneously govern battery performance. Thus, to elucidate the precise reactions occurring in RFB systems, an appropriate analysis technique that enables the real-time observation of electrokinetic phenomena is indispensable. Herein, we report in operando visualization and analytical study of RFBs by employing a membrane-free microfluidic platform, that is, a membrane-free microfluidic RFB. Using this platform, the electrokinetic investigations were carried out for the 5,10-bis(2-methoxyethyl)-5,10-dihydrophenazine (BMEPZ) catholyte, which has been recently proposed as a high-performance multiredox organic molecule. Taking advantage of the inherent colorimetric property of BMEPZ, we unravel the intrinsic electrochemical properties in terms of charge and mass transfer kinetics during the multiredox reaction through in operando visualization, which enables theoretical study of physicochemical hydrodynamics in electrochemical systems. Based on insights on the electrokinetic limitations in RFBs, we verify the validity of electrode geometry design that can suppress the range of the depletion region, leading to enhanced cell performance.
氧化还原液流电池（RFBs）是一种很有吸引力的大规模储能技术，在过去几十年中，其性能得到了显著提高。然而，由于其独特的工作机制，电化学和流体动力学同时控制电池性能，因此深入了解其反应机制仍然具有挑战性。因此，为了阐明 RFB 系统中发生的精确反应，需要一种能够实时观察电动现象的适当分析技术。在这里，我们报告了通过使用无膜微流控平台（即无膜微流控 RFB）对 RFB 进行操作中的可视化和分析研究。使用该平台，对最近提出的高性能多氧化还原有机分子 5,10-双（2-甲氧基乙基）-5,10-二氢吩嗪（BMEPZ）进行了电动研究。利用 BMEPZ 的固有比色性质，我们通过操作中的可视化揭示了多氧化还原反应过程中电荷和质量转移动力学的固有电化学特性，从而可以对电化学系统中的物理化学流体动力学进行理论研究。基于对 RFB 中电动限制的深入了解，我们验证了抑制耗尽区范围的电极几何设计的有效性，从而提高了电池性能。
