Revealing and Mitigating Crossover-Driven Side Reactions in Ferrocyanide-Based Redox Flow Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous organic redox flow batteries (AORFBs) are crucial for grid-scale energy storage and decarbonization.
• Current AORFBs face limitations in operational lifetime due to electrolyte decomposition and crossover.
• The interplay between electrolyte decomposition and crossover is poorly understood, hindering battery development.

Purpose of the Study:

• To investigate the impact of electrolyte crossover on redox flow battery degradation.
• To identify crossover-driven side reactions and their contribution to capacity fade.
• To develop strategies for mitigating these degradation pathways and enhancing battery lifetime.

Main Methods:

• Utilized an established on-line 1H NMR crossover characterization technique.
• Introduced novel 'simulated-crossover' experiments to probe anolyte-catholyte interactions.
• Analyzed electrolyte stability and side reaction products under simulated crossover conditions.

Main Results:

• Provided the first experimental evidence of crossover-driven side reactions in redox flow batteries.
• Demonstrated that neglecting these side reactions leads to underestimation of crossover's impact.
• Identified specific anolyte-catholyte combinations prone to these detrimental reactions.

Conclusions:

• Crossover-driven side reactions significantly impact AORFB lifetime and must be considered in degradation studies.
• Avoiding anolytes with hydroxyl functional groups when using ferrocyanide electrolytes effectively mitigates crossover-driven side reactions.
• These findings will guide the rational design of novel electrolytes for more durable and efficient redox flow batteries.