Optimized Anion Exchange Membranes for Vanadium Redox Flow Batteries

Abstract

In order to understand the properties of low vanadium permeability anion exchange membranes for vanadium redox flow batteries (VRFBs), quaternary ammonium functionalized Radel (QA-Radel) membranes with three ion exchange capacities (IECs) from 1.7 to 2.4 mequiv g(-1) were synthesized and 55-60 μm thick membrane samples were evaluated for their transport properties and in-cell battery performance. The ionic conductivity and vanadium permeability of the membranes were investigated and correlated to the battery performance through measurements of Coulombic efficiency, voltage efficiency and energy efficiency in single cell tests, and capacity fade during cycling. Increasing the IEC of the QA-Radel membranes increased both the ionic conductivity and VO(2+) permeability. The 1.7 mequiv g(-1) IEC QA-Radel had the highest Coulombic efficiency and best cycling capacity maintenance in the VRFB, while the cell's voltage efficiency was limited by the membrane's low ionic conductivity. Increasing the IEC resulted in higher voltage efficiency for the 2.0 and 2.4 mequiv g(-1) samples, but the cells with these membranes displayed reduced Coulombic efficiency and faster capacity fade. The QA-Radel with an IEC of 2.0 mequiv g(-1) had the best balance of ionic conductivity and VO(2+) permeability, achieving a maximum power density of 218 mW cm(-2) which was higher than the maximum power density of a VRFB assembled with a Nafion N212 membrane in our system. While anion exchange membranes are under study for a variety of VRFB applications, this work demonstrates that the material parameters must be optimized to obtain the maximum cell performance.

Preparation and performance evaluation of novel alkaline stable anion exchange membranes

“…Typically, anion exchange membrane (AEM) is a fundamental component in electrochemical systems for energy storage and energy conversion such as electrolyzers [1], flow batteries [2] and alkaline polyelectrolyte fuel cells [3]. Today, AEM is still a subject requiring multi-disciplinary investigation toward the development of polymer electrolyte fuel cell.…”

Thin skinned asymmetric polybenzimidazole membranes with readily tunable morphologies for high-performance vanadium flow batteries

“…These membranes are low-cost and show high vanadium prevention attributed to the rigid main chain which leads to a poor microphase separation and narrow and tortuous ionic channels. 7,[21][22][23][24][25] Nevertheless, the application of these membranes in VFB is hampered by their poor chemical stability, which is considered to be induced by the introduction of ion exchange groups. [26][27][28][29][30] In order to address this issue, Zhang et al started to focus on porous membranes for VFBs, 31 which separates large vanadium ions from small protons by screening mechanism.…”

Hybrid membranes with low permeability for vanadium redox flow batteries using in situ sol-gel process

“…However, sulfonated aromatic polymer membranes exhibit degradation due to backbone oxidation, which cannot tolerate the cyclic environment in VRFBs [16]. Several research groups have also studied anion exchange membranes as potential membranes for VRFBs due to their low cost and low permeability [17][18][19][20]. However, the low ionic conductivity and stability of anion exchange membranes in VRFBs exhibits low performance.…”