Balancing pH and Pressure Allows Boosting Voltage and Power Density for a H₂-I₂ Redox Flow Battery

Area of Science:

• Electrochemistry
• Energy Storage Systems
• Materials Science

Background:

• Redox flow batteries (RFBs) offer decoupled power and energy for long-duration storage.
• Hydrogen-iodine (H2-I2) chemistry is promising but faces challenges like low voltage and crossover.

Purpose of the Study:

• To enhance H2-I2 RFB performance by addressing limitations in voltage and mass transport.
• To demonstrate a stable and efficient H2-I2 RFB operation through strategic electrolyte and electrode design.

Main Methods:

• Implemented a neutral-pH catholyte and alkaline anolyte to increase cell voltage.
• Utilized a pressure-balanced gas diffusion electrode (GDE) to improve anode mass transport.
• Investigated the reversibility of side reactions caused by species crossover.

Main Results:

• Achieved an open circuit cell voltage of 1.28 V.
• Reached a maximum power density of 230 W/m² with mild hydrogen breakthrough.
• Demonstrated reversible side reactions for potential long-term operation.

Conclusions:

• Balancing pH and pressure in H2-I2 RFBs significantly boosts performance.
• Further optimization of GDE stability and electrolyte parameters is needed to maximize potential.