Zinc-Ferricyanide Flow Batteries Operating Stably under -10 °C

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Alkaline ferri/ferro-cyanide flow batteries offer cost-effective energy storage with high electrochemical activity.
• Key limitations include low energy density and poor performance at low temperatures due to ferrocyanide precipitation.
• Existing sodium hydroxide (NaOH) or potassium hydroxide (KOH) electrolytes exhibit limited ferrocyanide solubility (~0.4 M at 25°C).

Purpose of the Study:

• To develop a supporting electrolyte that enhances ferrocyanide solubility and improves temperature adaptability.
• To investigate the impact of lithium hydroxide (LiOH) on ferrocyanide solubility and battery performance.
• To demonstrate a high-performance zinc-ferricyanide flow battery utilizing the novel electrolyte.

Main Methods:

• Utilized a lithium-based supporting electrolyte, specifically lithium hydroxide (LiOH).
• Investigated the ion-dipole interactions and polarization effects of the lithium-based electrolyte on ferrocyanide.
• Fabricated and tested a zinc-ferricyanide flow battery with the enhanced catholyte.

Main Results:

• Achieved significantly enhanced ferrocyanide solubility: 1.7 M at 25°C and 0.8 M at -10°C.
• Demonstrated a zinc-ferricyanide flow battery with a charge energy of ~72 Wh L⁻¹ catholyte at 25°C.
• Exhibited stable cycling performance: ~4200 cycles at 25°C and ~800 cycles at -10°C.

Conclusions:

• The lithium-based supporting electrolyte effectively overcomes the solubility and temperature limitations of traditional ferrocyanide catholytes.
• This breakthrough enables higher energy density and robust performance in flow batteries across a wider temperature range.
• The developed zinc-ferricyanide flow battery shows promise for reliable and efficient large-scale energy storage.