全钒液流电池开路电压模型

Model of open-circuit voltage for all-vanadium redox flow battery

建立全钒液流电池六参数开路电压计算模型,揭示开路电压由电池总电势和VO2+/VO2+电极电势决定,并与电解液中钒离子透膜扩散行为密切相关。模型计算得到开路电压存在两个电压平台和一个转折点,与实验结果较为一致。利用该模型计算了电池开路时电解液中4种钒离子浓度随时间的变化关系,指出电池电解液不均衡性是由不同价态钒离子在膜相的Donnan平衡和透膜扩散系数不同产生的。该模型可为优化电池操作提供理论指导,并可为电池长期运行时电解液管理提供工程指导。

A six-parameter model of the open-circuit voltage （OCV） for all-vanadium redox flow battery （VRB） was proposed. This model indicated that OCV was associated with the electromotive force of the cell, VO2^＋/VO^2＋ electrode potential, and the transport behavior of vanadium ions in electrolyte across the membrane. Two plateaus and a turning point were obtained in OCV curve by this model, indicating that the calculated results were in good agreement with the experimental data. The dependence of concentrations of four kinds of vanadium ions on time was also investigated. The result showed that the electrolyte imbalance was caused by the differences of Donnan balance and diffusion coefficients of different vanadium ions across the membrane. This model can provide theoretical fundamentals for operation process and engineering guidance for electrolyte management of VRB.