Fabricating a Partially Fluorinated Hybrid Cation-Exchange Membrane for Long Durable Performance of Vanadium Redox Flow Batteries

Abstract

The long-term durability of vanadium redox flow batteries (VRFBs) depends on the stability and performance of the membrane separator. We have architected a hybrid membrane by uniform dispersion of MIL-101(Cr) (Cr-MOF) in a partially fluorinated polymer grafted with sulfonic acid groups (PHP@AMPS Cr-MOF(1.0) ). The single cell VRFB performance of the PHP@AMPS Cr-MOF(1.0) membrane was studied in comparison with the Cr-MOF incorporated Nafion membrane (Nafion Cr-MOF(1.0) ) and showed an excellent result with 97.5% Coulombic efficiency (CE) at 150 mA/cm 2 without any significant deterioration in the charge−discharge process for 1500 cycles (over 650 h). Meanwhile, the CE value of the Nafion Cr-MOF membrane (94.5%) deteriorated after 800 cycles (about 360 h) under similar conditions. The high VRFB performance of the PHP@AMPS Cr-MOF(1.0) membrane has been attributed to the synergized properties and good interactions between Cr-MOF and partially fluorinated polymer matrix responsible for the creation of hydrophilic proton-conducting channels to achieve high selectivity. Furthermore, the cost-effective polymer and thus membranes may open new windows for practical applications in other energy devices such as fuel cells, electrolysis, and water treatment.

High Proton Conductivity Membrane Based on Sulfonated Polybenzimidazole by Doping Ethylenediaminetetraacetic Acid-Modified MOF-808 for Vanadium Flow Battery

“…PHP@AMPS Cr-MOF(1.0) composite membrane's battery performance exhibited a splendid Coulombic efficiency (CE) (97.5%) at 150 mA cm −2 . 17 Recently, a study demonstrated that Zr-based MOFs have outstanding acid stability and oxidative stability, especially MOF-801 and MOF-808. Xin et al introduced MOF-801 and MOF-808 into SPEEK.…”

“…Sharma and Shahi designed a composite membrane by evenly dispersing MIL-101­(Cr) within a polymer that was functionalized with sulfonic acid groups (PHP@AMPS Cr‑MOF(1.0) ). PHP@AMPS Cr‑MOF(1.0) composite membrane’s battery performance exhibited a splendid Coulombic efficiency (CE) (97.5%) at 150 mA cm –2 . Recently, a study demonstrated that Zr-based MOFs have outstanding acid stability and oxidative stability, especially MOF-801 and MOF-808.…”

Construction and Investigation of Novel Cross-Linked Fluorine-Containing Sulfonated Polyimide Membranes for VFB Application

“…Vanadium flow battery (VFB), as a promising candidate for large-scale energy storage/conversion system, has been regarded as a solution to the intermittency and volatility of renewable resources. VFB has numerous merits, including long cycle life, safety, and independently scalable power and capacity. − As a key component, the membrane mainly plays two roles: (i) to separate the positive and negative electrolytes of VFB and (ii) to allow protons to transfer to form an internal circuit and obstruct the cross-migration of vanadium ions. An ideal membrane should have excellent proton conductance and strong vanadium ions resistance and stability. , …”

Quinone convertible sulfated ion conductive side chain for highly selective vanadium redox flow batteries

“…[13][14][15][16][17][18][19][20] The cationic exchange side chains have been widely investigated (as in Naon membranes), aiming to fabricate nano-scale wide ion conductive channels for fast proton conduction; however, they usually suffer from low coulomb efficiency and capacity retention. 21,22 To avoid high vanadium permeation through the anionic wide channels, one strategy is the hydrophilic non-ionic side chain that narrows the ion conductive channels via the less dissociated hydroxyl group 18 and amino group; 16 another strategy is the amphiprotic side chain that introduces cationic Donnan effect to the ion conductive membranes. 12,23 Despite the advantages, the-state-of-the-art non-ionic and amphiprotic side chains oen suffer from relatively high proton conduction resistance, difficulty in tuning the ratio of the anionic to cationic groups, being easy to precipitate by ionic cross-linking, etc., which restrict the balance between energy efficiency and capacity retention.…”