Affiliation:
1. Department of Materials Science and Engineering National University of Singapore Singapore 117576 Singapore
2. Institute of Sustainability for Chemicals Energy and Environment (ISCE2) Singapore 627833 Singapore
3. Centre for Hydrogen Innovations National University of Singapore Singapore 117580 Singapore
4. National University of Singapore (Suzhou) Research Institute Suzhou Jiangsu 215123 P. R. China
Abstract
AbstractAlkaline zinc‐iron flow batteries (AZIFBs) are well suited for energy storage because of their good safety, high cell voltage, and low cost. However, the occurrence of irreversible anodic parasitic reactions results in a diminished coulombic efficiency (CE), unbalanced charge state of catholyte/anolyte and subsequently, a poor cycling performance. Here, a universal CE compensation strategy centered around the oxygen evolution reaction (OER) on the cathodic side, is reported. This strategy aims to equalize the charge state of the [Fe(CN)6]3‐/4−‐based catholyte and counteract pH fluctuations. The OER process can be implemented either directly on the electrode through electrochemical reaction or in an external catalytic reactor column via a redox‐mediated process. This innovative approach effectively mitigates the gradual accumulation of [Fe(CN)6]3− in discharged catholyte and [Zn(OH)4]2− in charged anolyte by consuming the extra OH− during a continuous cycling process. As a result, AZIFBs demonstrate exceptional cycling performance with an extremely low capacity fading rate of 0.0128%/day (or 0.0005%/cycle) over 600 cycles at 80% state of charge (SOC). The proposed CE compensation strategy not only provides an effective way to address the CE loss issue for AZIFBs, but also can be applied to diverse battery technologies encountering CE loss caused by water/oxygen‐induced parasitic reactions.
Funder
National University of Singapore
Advanced Research and Technology Innovation Centre, College of Design and Engineering, National University of Singapore