Highly ion-selective sulfonated poly (4,4′-diphenylether-5,5′-bibenzimidazole) membranes for vanadium redox flow battery

Abstract

Renewable energy requires long-duration energy storage technologies, of which vanadium flow battery is regarded as the ­most suitable candidate for safe and long-duration energy storage ­applications. However, vanadium flow batteries still suffer from capacity decay and low power density, which arise from membrane degradation and high resistance. Herein, a sulfonated poly (4,4′-diphenylether-5,5′-bibenzimidazole) (SOPBI) membrane is reported for use in vanadium redox flow batteries. The prepared SOPBI membranes show an area resistance of 0.63 Ω cm² at room temperature after doped with 3 M H₂SO₄. Moreover, membranes with 3 M H₂SO₄ doping exhibit tensile stress at break of 15.1 MPa. Benefiting from the SOPBI membrane, the all-vanadium redox flow battery delivers a superior energy efficiency of 77.7% at 140 mA cm⁻² while operating stably at a current density of 120 mA cm⁻² for 200 cycles.

Keywords:

• Sulfonation
• OPBI
• polymer membrane
• vanadium flow batteries

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement (DAS)

The authors confirm that the data supporting the findings of this study are available within the article.