Microporous Separators On Fe/V Redox Flow Battery: A Valuable Opportunity for Cost Reduction

Microporous Separators on Fe/V Redox Flow Battery: A Valuable Opportunity for Cost Reduction

Wei, Xiaoliang; Luo, Qingtao; Li, Bin; Nie, Zimin; Shao, Yuyan; Chen, Feng; Chen, Baowei; Xia, Gordon; Li, Liyu; Yang, Z Gary; Wang, Wei

Pacific Northwest National Laboratory, 902 Battelle Boulevard, PO Box 999, Richland, WA 99354

Redox flow batteries are considered as one of the most promising medium-to-large scale energy storage technologies and have attracted much attention both academically and industrially.[1]^,[2] A number of redox chemistries have been proposed, and significant progress has been achieved by today.[3]^,[4] However, broad market penetration of redox flow batteries is still hindered by their intrinsic limitations such as high cost and low durability of components, narrow operational temperature range, limited solubility of active species, and/or low electrochemical activity.[5] The recently invented iron-vanadium (Fe/V) redox flow battery employing Fe^2+/3+ – V^2+/3+ redox couples have shown to be a promising option for stationary energy storage.[6]^,[7] The Fe/V flow battery demonstrated stable cycling performance with a nearly 100% utilization ratio over a broad temperature range of 0-50^oC.

The positive charged species, Fe³⁺, is a relatively weak oxidant. Therefore, hydrocarbon-based ion exchange membranes and/or separators are possible options for use in Fe/V flow battery system. This contribution investigated the cycling performance of a variety of polyethylene microporous separators on Fe/V flow cell. Among them, some separators exhibited energy efficiency of around 70% at temperatures ranging from 5-50^oC and at current densities up to 80mA/cm². Because these separators are very inexpensive, their use significantly reduces the capital cost of Fe/V flow battery, delivering great potential for developing a low-cost energy storage system.

Figure 1 Flow cell cycling efficiencies (CE, VE, and EE) of microporous separators A, B, C, D, and E.

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