Abstract
The vanadium redox flow battery (VRFB) is a promising and commercially available technology that poses advantageous features for stationary energy storage. A key component of the VRFB in terms of cost and system efficiency is the membrane. In recent years, anion exchange membranes (AEMs) have gained interest in VRFB research as they in general exhibit lower vanadium crossover due to a more substantial Donnan exclusion effect. In this study, a low-resistance flow cell was developed and the electrochemical performance of Aemion™ anion exchange membranes AF1-HNN5-50-X, AF1-HNN8-50-X and AF1-ENN8-50-X were compared against commonly used cation exchange membranes, Nafion® 211 and 212. The VRFB using AF1-ENN8-50-X exhibited superior performance versus Nafion® 212 regarding cycling efficiency and rate performance. However, relatively high and comparable capacity losses were observed using both membranes. NMR analysis showed no sign of chemical degradation for AF1-ENN8-50-X by immersion in VO2+ solution for 800 h. Although Aemion™ AEMs showed good chemical and electrochemical performance, considerable electrolyte crossover was observed due to high water uptake.
Highlights
With emerging global warming and increasing energy demands, renewable energy sources such as wind and solar power are gaining interest
AemionTM anion exchange membranes (AEMs) developed for alkaline water electrolysis (AF1-HNN5-50X, AF1-HNN8-50-X) and for vanadium redox flow battery (VRFB) (AF1-ENN8-50-X) were purchased from Ionomr
It is important to note that the ionic conductivity of Nafion 212 is due to the proton exchange through negatively charged sulfonic acid groups
Summary
With emerging global warming and increasing energy demands, renewable energy sources such as wind and solar power are gaining interest. Their intermittent nature requires efficient and low-cost energy storage systems to be developed [1,2]. A unique feature of RFBs is the independent scaling of power and energy, which gives excellent flexibility in configuration and operation. This is impossible for secondary batteries where the electrode and electrolyte are stored in the same compartment [3,4]. Up to the present day, RFBs have been further developed based on various chemistries including inorganic or organic redox species and aqueous or organic solvents [5,6,7]
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