Researchers from the University of Southern California (USC) Dornsiever School of Letters, Arts and Sciences demonstrated a new all-iron redox flow battery for renewable energy storage. They claim that this battery is inexpensive, safe and environmentally friendly , And long life.
The research proposed an improved coulombic efficiency all-iron iron electrode redox fluid battery, published in the "Equipment of the Electrochemical Society". It is said that the coulombic efficiency-the ratio of charge extraction to the charge placed in a cycle is 97.9%, due to the function Electrolyte additives, pH and temperature rise.
Researchers believe that this level of efficiency is one of the best records of iron electrode charging and discharging. The USC team said: "The coulombic efficiency of electrodeposited iron increases with the increase in pH at all current density values. Ascorbic acid plays an important role in determining the coulombic efficiency."
Researchers claim to have solved the problem of hydrogen parasitic evolution on the iron electrode during battery charging. This problem has caused the performance of the redox flow battery to drop sharply, and significant side reactions occur in devices with acidic electrolytes. The researchers said: "The generation of hydrogen affects the repeated cycles of the redox flow battery by rapidly changing the composition of the electrolyte in the system."
It is said that the adsorption of ascorbic acid added to the electrolyte inhibits hydrogen evolution at zero pH, increases the pH near the electrode surface, and improves the coulombic efficiency of ferroelectrodeposition. Ascorbic acid is used as an electrolyte additive for electroplating iron to minimize air oxidation of iron-it prevents the kinetics of hydrogen generation-combined with an increase in pH. The electrolyte solution is developed from ferric chloride and ammonium chloride. "Although these two compounds are well known, this is the first time they have been combined to demonstrate their potential for large-scale energy storage," said the USC research team.
Scholars believe that if another metal, such as cadmium, which is not completely environmentally friendly, co-deposits with iron and becomes incompatible, hydrogen production may be further inhibited. The team said: "This will ensure that the second metal always stays on the surface and will not diffuse to most of the iron electrode. By staying on the surface, the second metal will continue to provide electrodeposition that inhibits the generation of hydrogen throughout the process."
Researchers have found that battery efficiency increases as the operating temperature of the device increases. The scientists said: "We have observed that the Coulomb efficiency is 97.9% at 60 degrees Celsius and 91.8% at 25 degrees Celsius."
The researchers said: "Through the basic insights gained from this research and the improvement of coulombic efficiency, we believe that ferric chloride-based all-iron redox flow batteries will continue to provide attractive ways for large-scale electrical energy storage. The authors believe In the future, we will benefit from research on methods to achieve 100% Coulomb efficiency."
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