Repazole^® PBI Flow Battery Membrane (High-Current-Density Grade)

Product Overview

Repazole^® PBI flow battery membrane is an ion-exchange membrane developed for high-current-density flow battery stacks, based on intrinsically fluorine-free polybenzimidazole (PBI). At a thickness of 25 μm, the membrane combines low vanadium-ion permeability with high ionic conductivity, suppressing self-discharge and capacity fade while maintaining high voltage efficiency. In third-party testing on a 1 kW VRFB stack, the membrane delivered coulombic efficiency above 99% across the full 120–240 mW/cm² power-density range and energy efficiency of up to 88.5%, outperforming two commercial PFSA reference membranes tested under identical conditions. The product is suitable for vanadium and titanium-bromine flow battery systems and provides a fluorine-free route validated at stack level for long-duration energy storage projects.

Key Features

• Low permeability, low self-discharge: vanadium-ion permeability ≤9.0×10^-8 cm²/min; coulombic efficiency consistently above 99% across all duty points in a 1 kW stack, with excellent capacity retention during extended stands and repeated cycling;
• High conductivity, high efficiency: ionic conductivity ≥40 mS/cm; voltage efficiency comparable to commercial PFSA membranes, with energy efficiency exceeding two reference samples across the entire 120–240 mW/cm² range;
• Mechanical properties matched to thin-film design: tensile strength ≥40 MPa, elongation at break ≥80% and puncture strength ≥7 N, meeting the assembly and operating load requirements of a 25 μm membrane and supporting high-current-density stack design;
• Long-term operational reliability: 8,000+ cycles in a 20 W cell and 5,000 accelerated-aging cycles in a 1 kW stack with no significant performance decay; gradual changes arising from vanadium crossover can be restored to the initial level by re-mixing the electrolyte;
• Intrinsically fluorine-free: the molecular structure contains no fluorine, and no PFAS/PFOA substances are introduced during production — aligned with tightening regulation of fluorinated polymers in the EU and North America, and suitable for projects with explicit environmental-compliance requirements.

Specifications

^a Thicknesses from 20–50 μm available;
^{b, c} Measured in a third-party 1 kW VRFB stack at 180 mW/cm² power density.
Typical values only, for selection reference. Delivered specifications are subject to mutual confirmation.

Measured Performance (1 kW VRFB Stack)

CE = coulombic efficiency, VE = voltage efficiency, EE = energy efficiency (%). Reference samples are commercially available PFSA membranes tested under identical conditions.

Long-term cycling

• 20 W cell: 8,000+ cycles at a constant current density of 180 mA/cm², about 1.5 h per cycle;
• 1 kW stack: 5,000 cycles at a constant power density of 240 mW/cm², with no performance decay.

Slow changes arising from vanadium crossover during operation can be brought back to the initial level by re-mixing the electrolyte.

Handling & Storage

• Unpacking and inspection: open and handle the membrane in a dry, clean environment and check for transport damage such as pinholes or creases. A wetted surface or traces of exudate are normal — the membrane can be assembled as received; do not wipe the surface;
• Installation: in vanadium flow batteries the membrane requires no pre-treatment and can be assembled directly after opening; for other flow-battery chemistries, please consult our technical team before use;
• Storage conditions: store at room temperature, below 50% relative humidity and away from light. Where the ambient temperature may fall below 2 °C, thermal protection is required to prevent freezing, which causes physical damage to the membrane;
• After opening: use the membrane promptly after opening; return unused portions to the sealed bag and keep air exposure to a minimum;
• Temporary storage after removal: whenever a membrane is removed from the stack for temporary storage (transport, standby, etc.), it must be kept immersed in a protective solution matched to the battery chemistry (dilute sulfuric acid of the specified concentration, etc.). Under no circumstances should the membrane be allowed to dry — drying causes irreversible changes to the microstructure, and proton conductivity cannot be recovered. Re-prepare the protective solution if its concentration or pH changes noticeably.

Typical Applications

Ion-exchange membrane for vanadium and titanium-bromine flow battery energy storage systems, with typical applications including renewable energy storage plants, grid peak-shaving and frequency regulation, and wind/solar-plus-storage long-duration projects; the high-current-density design is particularly suited to frequency-regulation duty requiring continuous long-duration operation.

Need the full technical datasheet (TDS), the handling & storage guide, selection advice, or a quotation? Contact sales@riebom.com or leave a message below — we reply within one business day.

Repazole^® and Armurex^™ are trademarks of Guangzhou Riebom New Material Technology Research Co., Ltd.