Modeling the hydrodynamic and electrochemical efficiency of semi-solid flow batteries

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• 作者：Victor E. Brunini ; Yet-Ming Chiang ; W. Craig Carter ; ^{ccarter@mit.edu}
• 关键词：Flow battery ; Semi-solid ; Modeling ; Energy storage ; Lithium-ion
• 刊名：Electrochimica Acta
• 出版年：2012
• 期刊代码：30_00134686
• 类别：ch
• 出版时间：1 May, 2012
• 卷：69
• 期：Complete
• 页码：301-307
• 文件大小：669 K

摘要

A mathematical model of flow cell operation incorporating hydrodynamic and electrochemical effects in three dimensions is developed. The model and resulting simulations apply to recently demonstrated high energy-density semi-solid flow cells. In particular, state of charge gradients that develop during low flow rate operation and their effects on the spatial non-uniformity of current density within flow cells are quantified. A one-dimensional scaling model is also developed and compared to the full three-dimensional simulation. The models are used to demonstrate the impact of the choice of electrochemical couple on flow cell performance. For semi-solid flow electrodes, which can use solid active materials with a wide variety of voltage-capacity responses, we find that cell efficiency is maximized for electrochemical couples that have a relatively flat voltage vs. capacity curve, operated under slow flow conditions. For example, in flow electrodes limited by macroscopic charge transport, an LiFePO₄-based system requires one-third the polarization to reach the same cycling rate as an LiCoO₂-based system, all else being equal. Our conclusions are generally applicable to high energy density flow battery systems, in which flow rates can be comparatively low for a given required power.