An All-Soluble Fe/Mn-Based Alkaline Redox Flow Battery System.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Redox flow batteries (RFBs) are crucial for large-scale energy storage and renewable energy integration.
• Developing cost-effective and high-performance RFB systems remains a significant challenge.
• Iron and manganese are abundant, low-cost elements suitable for sustainable battery chemistries.

Purpose of the Study:

• To investigate a novel alkaline iron-manganese (Fe/Mn) redox flow battery system.
• To evaluate the performance of the [(TEA)Fe-O-Fe(TEA)]^3-/4- and MnO₄^-/2- redox couples.
• To assess the feasibility of this system for low-cost, high-energy storage applications.

Main Methods:

• Constant current cycling tests were conducted at ±41 mA cm^-2.
• The battery was cycled between 20% and 80% state of charge (SOC) for 800 hours (400 cycles).
• Periodic acid treatment was employed to address performance degradation.

Main Results:

• The Fe/Mn RFB system achieved an apparent Coulombic efficiency (CE) approaching 100%.
• Voltage efficiency (VE) decreased from approximately 75.3% to 61.4% over the testing period.
• Manganese dioxide (MnO₂) deposition on the separator was identified as a cause for increased internal resistance.

Conclusions:

• The alkaline Fe/Mn RFB system shows promise for low-cost, sustainable energy storage.
• Maintaining voltage efficiency requires mitigation strategies for MnO₂ deposition.
• Periodic acid treatment can effectively restore voltage efficiency by removing separator deposits.