Insights into the Impact of the Nafion Membrane Pretreatment Process on Vanadium Flow Battery Performance

Abstract

Nafion membranes are now the most widely used membranes for long-life vanadium flow batteries (VFBs) because of their extremely high chemical stability. Today, the type of Nafion membrane that should be selected and how to pretreat these Nafion membranes have become critical issues, which directly affects the performance and cost of VFBs. In this work, we chose the Nafion 115 membrane to investigate the effect of the pretreatment process (as received, wet, boiled, and boiled and dried) on the performance of VFBs. The relationship between the nanostructure and transport properties of Nafion 115 membranes is elucidated by wide-angle X-ray diffraction and small-angle X-ray scattering techniques. The self-discharge process, battery efficiencies, electrolyte utilization, and long-term cycling stability of VFBs with differently pretreated Nafion membranes are presented comprehensively. An online monitoring system is used to monitor the electrolyte volume that varies during the long-term charge-discharge test of VFBs. The capacity fading mechanism and electrolyte imbalance of VFBs with these Nafion 115 membranes are also discussed in detail. The optimal pretreatment processes for the benchmark membrane and practical application are synthetically selected.

Ultra‐High Ion Selectivity of a Modified Nafion Composite Membrane for Vanadium Redox Flow Battery by Incorporation of Phosphotungstic Acid Coupled UiO‐66‐NH2

“…All the tests begin with a state of charge (SOC) value of 75%, and the OCV changing with time from the VRB with recast Nafion and the modified membrane are presented in Figure a. The OCV of VRBs assembled with both recast Nafion and Nafion‐(UiO‐66‐NH 2 @PWA)‐3 wt% gradually decreases in the initial stage and then appears to undergo sharp voltage drops, which is consistent with the phenomenon that is described in the literature . For the same type of membrane, the initial OCV of VRBs decreases gradually with the reduction of membrane thickness.…”

Investigation of Nafion series membranes on the performance of iron‐chromium redox flow battery

“…It should be noted that the pretreatment methods for the Nafion membranes may have a critical effect on the RFB performance. In the literature, 35,36 it demonstrates that the "wet" and "boiled" Nafion exhibit relatively lower resistance, while simultaneously higher vanadium permeability. This is owing to the acid and deionized water pretreatment may swell the micro micelle structure of the Nafion membrane.…”

Equilibrium and Dynamic Absorption of Electrolyte Species in Cation/Anion Exchange Membranes of Vanadium Redox Flow Batteries

“…[20] The Nafion 117C EM was soaked in as olution of deionized water and HNO 3 (65 %, 1:1v/v) and heated at 90 8Cf or 1h, [21] whereas the FAP4 50 AEM was dipped into 0.5 m NaCl solution and kept at 25 8Cf or 72 h. [22] After that, the membrane samples were washed with deionized water several times and kept in dust-free and dark conditions before testing with vanadium electrolyte. For characterization under equilibrium conditions, the selected membranes were cut into 2 2cm 2 pieces and pretreated as described below to remove any contamination or impurity.…”

“…For characterization under equilibrium conditions, the selected membranes were cut into 2 2cm 2 pieces and pretreated as described below to remove any contamination or impurity. [20] The Nafion 117C EM was soaked in as olution of deionized water and HNO 3 (65 %, 1:1v/v) and heated at 90 8Cf or 1h, [21] whereas the FAP4 50 AEM was dipped into 0.5 m NaCl solution and kept at 25 8Cf or 72 h. [22] After that, the membrane samples were washed with deionized water several times and kept in dust-free and dark conditions before testing with vanadium electrolyte.…”