Open circuit voltage of vanadium redox flow batteries: Discrepancy between models and experiments
Open circuit voltage of vanadium redox flow batteries: Discrepancy between models and experiments
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DOI：
10.1016/j.elecom.2011.01.020
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发表时间：
2011-04-01
影响因子：
5.4
通讯作者：
Kumbur, E. C.
中科院分区：
文献类型：
--
作者：
Knehr, K. W.;Kumbur, E. C.
现有的钒液流电池(VRFB)模型的一个主要问题是对开路电压(OCV)的预测不准确，导致预测的电池电压与实验数据相差131-140 mV。这种偏差是由于采用燃料电池文献中的能斯特方程计算开路电压时，对电池内部电化学双电层的描述不完整所造成的。在这里，我们提出了一个更完整的能斯特方程，它解释了VRFB中存在的两个额外的电化学机制，即：i)由于质子参与氧化还原反应而在正极上的质子活性，以及ii)由于膜上的质子浓度差异而产生的Donnan势。本文提出的完整形式的Nernst方程准确地预测了已报道的实验数据，平均误差为1.2%，比目前VRFB模型中使用的不完全Nernst方程(平均误差为8.1%)有了显著的改善。(C)2011爱思唯尔B.V.保留所有权利。
A major issue with the existing vanadium redox flow battery (VRFB) models is the inaccurate prediction of the open circuit voltage (OCV), which results in a discrepancy of 131 to 140 mV in predicted cell voltages when compared to experimental data. This deviation is shown to be caused by the incomplete description of the electrochemical double layers within the cell when calculating the OCV using the Nernst equation adopted from fuel cell literature. Here, we propose a more complete description of the Nernst equation, which accounts for two additional electrochemical mechanisms that exist in a VRFB, namely: i) the proton activity at the positive electrode due to the involvement of the protons in the redox reaction, and ii) the Donnan potential due to the proton concentration differences across the membrane. The complete form of the Nernst equation proposed herein accurately predicts the reported experimental data with an average error of 1.2%, showing a significant improvement over the incomplete Nernst equation (8.1% average error) currently used in VRFB models. (C) 2011 Elsevier B.V. All rights reserved.