Polybenzimidazole (PBI) Ion-Exchange Membrane for Redox Flow Battery, CRFBIEMPBI

Polybenzimidazole (PBI) is a high-performance, non-fluorinated thermoplastic that has become a leading alternative to Nafion for Vanadium Redox Flow Batteries (VRFBs).

While materials like SPEEK are modified to have negative charges, PBI is a basic polymer. In the acidic environment of a flow battery, the nitrogen atoms in the PBI backbone become protonated, giving the membrane a positive charge. This creates a unique "Donnan Exclusion" effect that makes it one of the most selective membranes available. The features of PBI membrane in redox flow battery are shown below:

(1) Protonation: The imidazole groups in the PBI backbone (N-H) react with the acid to form positively charged sites.

(2) Donnan Exclusion: These fixed positive charges electrostatically repel the positively charged vanadium ions (V2+, V3+, VO2+). 

(3) Ion Transport: While vanadium is repelled, protons (H+) and sulfate anions (HSO4-) can still pass through the polymer's free volume to maintain charge balance.

Part Number	CRFBIEMPBI (C-RFB-IEMPBI)
Chemical Structure
Appearance	Yellow
Dimension	T 25 um * L 100mm * W 100 mm (Other membrane sizes can be supplied upon request)
Ion Conductivity	> 40 mS/cm
Vanadium Ion Permeability	<9*10-8 cm2/min
Tensile Strength	>40 MPa
Columbic Efficiency for VRFBs	>99%
Package Grade	1 pcs/pack

References

(1）X. Che, et al., Porous polybenzimidazole membranes with high ion selectivity for the vanadium redox flow battery, J. Membrane Sci., 2020, 611, 118359. 

(2) Y. Chen, et al., Ion conductive mechanisms and redox flow battery applications of polybenzimidazole-based membranes, Energy Storage Mater., 2022, 45, 595-617.