Revitalizing Iron Redox by Anion-Insertion-Assisted Ferro- and Ferri-Hydroxides Conversion at Low Alkalinity

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Energy

Background:

• Iron hydroxides are cost-effective and eco-friendly electrode materials for alkaline batteries.
• Challenges include low storage capacity and poor cycling life due to hydrogen evolution and Fe3O4 formation.

Purpose of the Study:

• To investigate the use of green rust (GR) as a promoter for iron-based electrodes.
• To enhance the Fe(OH)2/FeOOH conversion process for improved battery performance.

Main Methods:

• Synthesis of green rust via sulfate insertion.
• Electrochemical testing in half-cells and full-cells.
• Theoretical calculations and classical molecular dynamics simulations.

Main Results:

• Green rust demonstrated a discharge capacity of ~211 mAh g-1 in half-cells.
• Achieved 93% Coulombic efficiency after 300 cycles in full-cells.
• Sulfate anions facilitate Fe(OH)2/FeOOH conversion, with low alkalinity ensuring fast sulfate ion transport.

Conclusions:

• Anion-insertion-assisted conversion, using green rust (sulfate) or chloride ions, improves Fe-based electrode efficiency.
• This method offers a sustainable pathway for developing high-performance iron electrodes for energy storage applications.