Ion-Regulating Membranes with Surface-Enriched Charge Networks Enabling Stable Zinc-Manganese Flow Batteries.

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Energy

Background:

• Zinc-based flow batteries offer sustainable energy storage with high energy density and eco-friendliness.
• Zinc-manganese flow batteries, utilizing Mn2+/MnO2 posolyte, promise ultra-low electrolyte costs.
• Practical application is hindered by low areal capacity and poor lifespan due to proton crossover and zinc dendrite formation.

Purpose of the Study:

• To address proton crossover and zinc dendrite formation in zinc-manganese flow batteries.
• To develop an ion-regulating membrane for enhanced battery performance.
• To improve the stability and energy density of zinc-based flow batteries.

Main Methods:

• Designed an ion-regulating membrane with surface-enriched positive charges via Zn2+ crosslinked networks.
• Utilized charge-enhanced dehydration barriers and nitrogen-groups synergism to amplify H+ retention.
• Employed electrostatic guidance for uniform zinc ion distribution to prevent dendrite formation.

Main Results:

• Achieved a 60% elevated proton transport barrier (0.104 eV) and effective discrimination of K+ ions.
• Demonstrated uniform zinc-oriented growth without dendrites.
• Obtained a record accumulated capacity of 6510 mAh cm-2 (>200 cycles) at 30 mA cm-2.
• Reached a high areal capacity of 100 mAh cm-2 (130.1 mWh cm-2) at 20 mA cm-2.

Conclusions:

• The proposed membrane design effectively suppresses proton crossover and zinc dendrites.
• The synergistic strategy leads to a stable near-neutral zinc-manganese flow system.
• This study presents a viable membrane strategy for low-cost, high-energy-density zinc-based flow batteries.