Aqueous Electrolytes For Fe Metal Batteries

Aqueous Electrolytes Reinforced by Mg and Ca Ions for Highly Reversible Fe Metal Batteries

Iron (Fe) metal batteries, such as Fe-ion batteries and all Fe flow batteries, are promising energy storage technologies for grid applications due to the extremely low cost of iron and iron salts. However, the cycle life of Fe metal batteries is poor due to the low columbic efficiency of the iron deposition/stripping reaction. Current aqueous electrolytes based on iron chloride or sulfate salts can only operate at an efficiency of 68-80% due to undesired hydrogen evolution side reaction.

Electrolytes that can support highly reversible iron metal anode is critical to realize the potential of aqueous Fe metal batteries as a low-cost energy storage technology. The use of two novel aqueous Fe electrolyte reinforced with Mg ion (FERMI) and Ca ion (FERCI), show remarkably better iron deposition/stripping efficiency (99.1%) than the baseline iron electrolytes (68%-80%). Coin cell studies show the baseline iron-electrolyte fails due to a sudden increase in overpotential in less than one hundred hours, whereas FERMI and FERCI can cycle hundreds of hours without failure, long-cycle Fe metal batteries. Comprehensive experimental and computational studies reveal the enhanced iron deposition/striping efficiency is due to a synergy of improved deposit morphology and enhanced water reduction resistance. Due to the simple method of fabrication and low cost of raw materials, these novel electrolytes are ideal for unleashing the low-cost benefit of Fe metal batteries. These electrolytes not only enable long-cycle Fe metal batteries but also open a new avenue to address the HER side reaction for other electrochemical technologies based on aqueous electrolytes, such as the CO2 reduction NH3 synthesis, etc.

Proof of Concept

- Does not require expensive catalysts.

- Does not require high salt concentration.

- Inexpensive and versatile.

Aqueous Electrolytes Reinforced by Mg and Ca Ions for Highly Reversible Fe Metal Batteries ACS Cent. Sci. 2022, 8, 6, 729–740 https://pubs.acs.org/doi/10.1021/acscentsci.2c00293

Clay Macomber
u6072657@utah.edu