The H/Br redox flow batteries (RFBs) have exhibited to be a promising high-power energy storage system in which proton-exchange membranes are used as the ion carriers like the fuel cells. The membrane transport properties are highly influenced by water and hydrogen bromide (HBr) distributions inside a cell, which have a significant impact on charge/species transport efficiency and overall cell performance. In particular, the membrane is in close contact with the aqueous Br/HBr electrolyte solution and thus the hydrogen electrode is prone to flooding, which makes removal of liquid water and HBr in the hydrogen side more challenging, particularly during charge process. In this study, we present a two-phase H/Br RFB model to accurately capture key performance loss factors, i.e., hydrogen electrode flooding and HBr accumulation. The present model which rigorously accounts for the two-phase flow in the hydrogen side and variation of water uptake of membrane as a function of HBr accumulation, is successfully validated against experimental polarization curves and water crossover flux data measured during charge and discharge. The simulation results highlight that severe flooding in the hydrogen electrode occurs during charge, i.e., accompanied by the high level of HBr accumulation. However, the level of electrolyte dehydration due to the high HBr accumulation is not as serious as the activation overpotential increase due to hydrogen electrode flooding.

中文翻译：

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水传输对氢溴氧化还原液流电池性能的影响


H/Br氧化还原液流电池（RFB）已被证明是一种有前途的高功率储能系统，其中质子交换膜像燃料电池一样用作离子载体。膜传输特性很大程度上受电池内水和溴化氢 (HBr) 分布的影响，这对电荷/物质传输效率和整体电池性能具有重大影响。特别是，膜与 Br/HBr 电解质水溶液紧密接触，因此氢电极容易发生水淹，这使得去除氢侧的液态水和 HBr 更具挑战性，特别是在充电过程中。在本研究中，我们提出了一个两相 H/Br RFB 模型，以准确捕获关键性能损失因素，即氢电极淹没和 HBr 积累。本模型严格解释了氢侧的两相流以及膜吸水量随 HBr 积累的变化，并根据实验极化曲线和充电和放电期间测量的水交叉通量数据成功进行了验证。模拟结果强调，充电过程中氢电极会发生严重的溢流，即伴随着高水平的 HBr 积累。然而，由于HBr高积累而导致的电解质脱水程度并不像氢电极淹没导致的活化过电势增加那么严重。