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Breaking the barriers for low-cost energy storage

15 August 2012

A team of researchers has developed a cheap, rechargeable and eco-friendly battery that could be used to store energy at solar power plants.

Sri Narayan tests one of his new iron-air batteries, using it to power a small fan (photograph: Dietmar Quistorf)
Sri Narayan tests one of his new iron-air batteries, using it to power a small fan (photograph: Dietmar Quistorf)

Led by Sri Narayan, professor of chemistry at the University of Southern California (USC), the team developed an air-breathing battery that uses the chemical energy generated by the oxidation of iron plates that are exposed to oxygen in air — a process similar to rusting.

As currently developed, Narayan’s batteries have the capacity to store between eight and 24 hours’ worth of energy. His patent is pending, and both the federal government and California utilities have expressed interest in the project.

Iron-air batteries have been around for decades — they saw a surge in interest during the 1970s energy crisis but suffered from a crippling problem: a competing chemical reaction of hydrogen generation that takes place inside the battery (hydrolysis) removed about 50 percent of the battery’s energy, making it too inefficient to be useful.

Narayan and his team managed to reduce the energy loss down to 4 percent, making iron-air batteries that are about ten times more efficient than their predecessors. The team did it by adding a very small amount of bismuth sulphide into the battery. Bismuth shuts down the wasteful hydrogen generation. Adding lead or mercury might also have worked to improve the battery’s efficiency but wouldn’t have been as safe, Narayan said.

“A very small amount of bismuth sulphide doesn’t compromise on the promise of an eco-friendly battery that we started with,” he said.

Despite this initial success, Narayan’s work is ongoing. His team is working to make the battery store more energy with less material.

Details about the battery are published in the Journal of the Electrochemical Society.

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