钒离子浓度对全钒液流电池极化分布的影响

Effects of Vanadium Concentration on the Distribution of Polarization in All Vanadium Redox Flow Battery

基于物质传递方程、电荷传递方程和电化学动力学方程提出了浓差极化系数的概念,建立了全钒液流电池二维模型,利用有限元法研究了钒电池极化过程,并对电极区域极化的分布进行了定量评估。研究表明:增加钒离子浓度,电极表面和溶液本体浓度趋同,活化极化和浓差极化减小,这种现象在高电流密度下尤为明显;浓度的增加也使得浓差极化系数减小,物质传递的影响减小,浓差极化相对于整个极化影响越来越弱;从进口到出口,浓差极化系数逐渐增加;电极与集流体接触面的浓差极化系数比电极中间区域高得多。

Based on the mass transfer equation, charge transfer equation and electrochemical kinetics equation, a two-dimensional model of all vanadium redox flow battery （VFB） was established and the concentration polarization coefficient （CPC） was introduced, respectively. The polarization process was studied quantitatively through the research of VFB polarization process and CPC with the finite element method. The results indicate that as the vanadium ion concentration is increased, the concentration on the electrode surface and in the electrolyte bulk trends identical, and the activation polarization, concentration polarization, CPC as well as the mass transfer effect are decreased. This phenomenon is more obviously when VFB is operated at the high current density than at low current density and the polarization decreasing trend will be slowed down during the concentration increasing process. The CPC was much higher at the interface between electrode and current collector than that in the electrode bulk and the CPC is increased gradually from the inlet to outlet.