Thousands of hours of battery, and it's green too
By Karin Kloosterman
November 12, 2009
A new battery from Israel lasts thousands of hours and its non-polluting silicon energy source reverts back to sand when it's depleted.
Prof. Yair Ein-Eli hopes that one day his new green battery could be used in anything from hearing aids to electric cars.
Perhaps it was Israel's deserts and dunes that supplied the inspiration for Prof. Yair Ein-Eli's battery that lasts for thousands of hours and has a silicon power source that reverts back to sand when it's spent.
The research was conducted at the Technion - Israel Institute of Science and recently published in the journal Electrochemistry Communications. The article explores how this new breed of portable electrochemical battery produces thousands of hours of charge from an abundant and non-polluting fuel source.
Being small and portable (the battery ranges in size from less than a third of an inch to an inch or so), it could replace the batteries used in hearing aids. Thinking ahead, this technology could replace the two-to-three hour battery lifespan of laptops, allowing them to run for hundreds of hours on a single charge. And it could ultimately evolve into a new kind of battery for electric cars and solar panels, or a power source for space stations on the moon.
The technology could be used in small devices within a couple of years. For the rest, "This would take about 10 years more and be revolutionary," Ein-Eli tells ISRAEL21c. He developed the battery technology over the past two and a half years and has been working in the area of silicon for fuel for about eight years.
A new alternative to hearing-aid users
Based on silicon the battery works by enabling this abundant material to revert back to its original form as sand. The battery can sit on a shelf for years before it's activated.
"In the paper, we showed that at 600 hours it had used only 10 percent of the energy. So we are talking about 6,000 hours," says the professor.
Ein-Eli's technology, created in collaboration with Prof. Digby Macdonald from Pennsylvania State University and Prof. Rika Hagiwara from Kyoto University in Japan, offers an entirely new alternative to today's zinc or lithium-ion batteries that is a real boon to hearing-aid users.
"Do you know someone or have a relative who wears a hearing aid?" asks Ein-Eli. With a charge that lasts only a couple of weeks, people who wear these aids need to carry around a supply of batteries like a box of pills. Worse, they don't work well in conditions with extreme humidity like in Singapore, or in regions with extreme dryness, like Arizona, he says.
Always a battery man
Ein-Eli started working with batteries decades ago, and was raised he says, as an electrochemist. "When I did my PhD in this area it was not so popular - first I worked on lithium metal batteries and then changed to lithium ion in 1993," he recounts.
Working under one of the world's leading battery researchers - Prof. Doron Aurbach at Israel's Bar Ilan University - Ein-Eli says he was fortunate to have a good base, and from there went on to a post-doctorate post at Harvard. Later, while at a Bet Shemesh company called Electric Fuel, Ein-Eli discovered metal air, the basis of his new invention.
Regular zinc batteries, like the ones Duracell makes, are made from two electrodes, a cathode and an anode, which are separated by ions in liquid. But in Ein-Eli's new solution, only one electrode is needed, which means there's more power. In his battery, the oxygen inside passes through a membrane to interact with oxidized silicon. This stable, inert, light and non-toxic material is high in energy and reverts to sand after the fuel is depleted.
For now, the battery is not rechargeable, but the fact that it can last thousands of hours makes it attractive to companies in the small electronics market. One example is MEMS - small electric machines that need their own energy source.
Ein-Eli is currently working on boosting the battery's energy output even further. He believes that in three or four years it will be rechargeable. It's a dream, he says, but "dreams may come true if you work at them."
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