Enhancing the Stability of Aqueous Membrane-Free Flow Batteries: Insights into Interphase Processes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Conventional redox flow batteries face limitations due to expensive ion-selective membranes.
• Membrane-free flow batteries offer a potential solution but struggle with low power density and self-discharge.

Purpose of the Study:

• To develop a novel aqueous biphasic system for membrane-free flow batteries.
• To improve electrolyte properties, enhance active species compatibility, and understand interphase phenomena.

Main Methods:

• Computational and experimental examination of potassium ferrocyanide and sulfonated viologen species.
• Utilized scanning electrochemical microscopy (SECM) to analyze the liquid-liquid interphase.
• Evaluated electrolyte ionic conductivity, viscosity, and active species concentration.

Main Results:

• Achieved a tenfold higher concentration of redox species in their respective electrolytes.
• Expanded open-circuit voltage to 1.1 V and increased power densities by 3.5 times.
• Demonstrated 80.2% energy efficiency and stable performance over a month (400 cycles).

Conclusions:

• The novel aqueous biphasic system enhances electrolyte properties and active species compatibility for membrane-free flow batteries.
• Detailed interphase studies revealed insights into species transport and stability.
• This work advances membrane-free flow battery technology by avoiding parasitic reactions and improving performance.