Mild pH-decoupling aqueous flow battery with practical pH recovery

Author(s):Show less -

Xi, Dawei ; Alfaraidi, Abdulrahman M. ; Gao, Jinxu ; Cochard, Thomas ; Faria, Luana C. I. ; Yang, Zheng ; George, Thomas Y. ; Wang, Taobo ; Gordon, Roy G. ; Liu, Richard Y. ; Aziz, Michael J.

• Document type: Journal article
• Source: NATURE ENERGY; v. 9, n. 4, p. 12-pg., 2024-02-19.

Abstract

Establishing a pH difference between the two electrolytes (pH decoupling) of an aqueous redox flow battery (ARFB) enables cell voltages exceeding the 1.23 V thermodynamic water-splitting window, but acid-base crossover penalizes efficiency and lifetime. Here we employ mildly acidic and mildly alkaline electrolytes to mitigate crossover, achieving high round-trip energy efficiency with open circuit voltage >1.7 V. We implemented an acid-base regeneration system to periodically restore electrolytes to their initial pH values. The combined system exhibited capacity fade rate <0.07% per day, round-trip energy efficiency >85% and approximately 99% Coulombic efficiency during stable operation for over a week. Cost analysis shows that the tolerance of acid-base crossover could be increased if the pH-decoupling ARFB achieved a higher voltage output and lower resistance. This work demonstrates principles for improving lifespan, rate capability and energy efficiency in high-voltage pH-decoupling ARFBs and pH recovery concepts applicable for pH-decoupling systems. (AU)

• FAPESP's process: 21/14537-2 - Low-cost and high-performance carbon electrodes for application in redox flow battery
• Grantee: Luana Cristina Italiano Faria
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• FAPESP's process: 19/21089-6 - Carbon surfaces for organic battery application: structural properties of the hydrogel/electrolyte/electrode interface
• Grantee: Luana Cristina Italiano Faria
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)