Former NASA Scientist Developing Batteries of the Future

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As our lives depend more on electronic devices – smartphones, tablets, hybrid cars – our need for a sustainable energy source is never far from our thoughts. Up until now, our choices for more power-packed battery options were between rechargeable batteries or lithium-ion batteries, which represent the most energy-dense batteries available for practical use. But Sri Narayan, professor of chemistry at USC Dornsife and co-director of the USC Loker Hydrocarbon Research Institute, wants to do better.

eeDesignIt reported that after earning his Ph.D., Narayan began work at NASA’s Jet Propulsion Laboratory and spent nearly 20 years advancing various types of batteries and fuel cells, including the lithium-ion battery technology used on the Mars Spirit, Opportunity and Curiosity rovers.

Since 2010, Narayan has taught at USC Dornsife and is working on a way to bring lithium-sulfur batteries into widespread use. These batteries pack two to three times more energy than their lithium-ion counterparts, reported eeDesignIt. These batteries will be less prone to overheating and erupting in flame when overcharged or overtaxed. Plus, by using the more cost-effective sulfur alternative, these batteries will cost less.

Regarding today’s lithium-sulfur batteries and their charges, Narayan said, “Lithium-sulfur, today, is at a hundred cycles. That’s all. It’s pathetic.” Given that most people charge their phones daily, this means replacing the battery within three months. Lithium-ion batteries generally last two to three years. The short life of the lithium-sulfur batteries stems from the tendency for sulfur ions, called sulfides, to cling to one another and then escape from the positive electrode (the cathode). But Narayan and Ph.D. student Derek Moy, have developed a way to give these batteries longer lives.

The solution is called ‘mixed conduction membrane,’ or MCM. This thin, nonporous material conducts lithium ions but blocks the polysulfide reactions that degrade the battery. Batteries with the MCM lasted through as many as 500 cycles with no loss of charge capacity, Narayan said. This should be enough to get the average person through the lifespan of a cell phone, especially considering that most people upgrade to a new model every few years.

While Narayan cautions the technology is in its infancy, he thinks the advantages of lithium-sulfur – inexpensive, abundant materials, and more energy per unit weight – could soon benefit handheld electronics and eventually vehicles. “Lithium-sulfur will probably find its place in cell phones before it makes it into cars. That’s a natural projection,” he said.

Published October 25, 2017

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