Novel ether-free sulfonated poly(biphenyl) tethered with tertiary amine groups as highly stable amphoteric ionic exchange membranes for vanadium redox flow battery

Side-Chain Grafting-Modified Sulfonated Poly(ether ether ketone) with Significantly Improved Selectivity for a Vanadium Redox Flow Battery

“…The proton conductivity of the SPEEK-SA-50 (0.099 S cm –1 ) series membranes is higher than SPEEK membranes (0.061 S cm –1 ). The proton conductivity of grafted SPEEK-SA-50 membranes increases, which can be attributed to the fact that the N atoms of the SPEEK-SA series membranes act as proton donors and acceptors and protons can transport between N atoms and −SO 3 H groups within a short distance . With the increase of the grafting degree, the conductivity of the membrane began to increase.…”

“…The proton conductivity of grafted SPEEK-SA-50 membranes increases, which can be attributed to the fact that the N atoms of the SPEEK-SA series membranes act as proton donors and acceptors and protons can transport between N atoms and −SO 3 H groups within a short distance. 29 With the increase of the grafting degree, the conductivity of the membrane began to increase. However, when the grafting degree was further increased, the conductivity of the membrane decreased.…”

“…So far, because of its extraordinarily high conductivity and outstanding chemical stability, Nafion membranes are still one of the finest choices for VRFB ion-selective membranes . However, the drawbacks of a high expansion rate, substantial vanadium ion penetration, and high cost are the key issues for large-scale deployment of Nafion membranes in VRFBs. , Many efforts have been made to date to produce innovative ion-selective membranes with improved performance and cheaper costs, such as cross-linking-modified − and polymer-blended composite membranes. − Because of their low cost, stability, and ease of manufacture, sulfonated poly­(ether ether ketone) membranes (SPEEK) have received a lot of interest. ,,,− Amphoteric ion exchange membranes with fixed cations and anion exchange groups have received a lot of interest in recent years. , Due to electrostatic repulsion, the positive ion group can effectively prevent the positive diffusion of vanadium ions under battery operating conditions, while the negative ion group provides optimum proton conductivity. Sulfamic acid (SA) contains −SO 3 H (acidic) and −NH 2 (weak basic) groups, which can be used to replace the inherent conductivity/permeability balance of the proton exchange membrane …”

“…14,16,17,23−28 Amphoteric ion exchange membranes with fixed cations and anion exchange groups have received a lot of interest in recent years. 29,30 Due to electrostatic repulsion, the positive ion group can effectively prevent the positive diffusion of vanadium ions under battery operating conditions, while the negative ion group provides optimum proton conductivity. Sulfamic acid (SA) contains −SO 3 H (acidic) and −NH 2 (weak basic) groups, which can be used to replace the inherent conductivity/permeability balance of the proton exchange membrane.…”

Development of a High-Performance Proton Exchange Membrane: From Structural Optimization to Quantity Production

“…We synthesized the PEMs via two simple reactions, as shown in Scheme . Indoline was selected as the backbone unit due to the highly reactive −NH groups for grafting with flexible sulfonate acid side chains. , Further, the grafting degree of the sulfonate groups is controllable by changing the addition amount of 1,3-propanesultone. In this study, we synthesized SBPI-0.6, SBPI-0.8, and SBPI-1.0 to achieve PEMs with different IEC values (the corresponding IEC values are 1.6, 2.0, and 2.3 mmol g –1 , respectively).…”