Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
ACS Appl Mater Interfaces. 2013 Aug 14;5(15):7559-66. doi: 10.1021/am401858r. Epub 2013 Jul 19.
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.
为了了解低钒渗透率阴离子交换膜在钒氧化还原流电池（VRFB）中的性能，合成了季铵官能化的 Radel（QA-Radel）膜，其离子交换容量（IEC）分别为 1.7、2.0 和 2.4 mequiv g(-1)，并对厚度为 55-60 μm 的膜样品进行了传输性能和电池性能评估。测量了库仑效率、电压效率和能量效率等单电池测试中的电池性能，以及循环过程中的容量衰减，以研究和关联膜的离子电导率和 VO(2+)渗透率。增加 QA-Radel 膜的 IEC 会同时增加离子电导率和 VO(2+)渗透率。在 VRFB 中，1.7 mequiv g(-1) IEC 的 QA-Radel 具有最高的库仑效率和最佳的循环容量保持率，而电池的电压效率受限于膜的低离子电导率。对于 2.0 和 2.4 mequiv g(-1) 的样品，增加 IEC 会导致更高的电压效率，但这些膜的电池表现出较低的库仑效率和更快的容量衰减。IEC 为 2.0 mequiv g(-1) 的 QA-Radel 具有最佳的离子电导率和 VO(2+)渗透率平衡，实现了 218 mW cm(-2) 的最大功率密度，高于我们系统中使用 Nafion N212 膜组装的 VRFB 的最大功率密度。虽然阴离子交换膜正在各种 VRFB 应用中进行研究，但这项工作表明，必须优化材料参数以获得最大的电池性能。
