DHS gives batteries a jolt
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At the heart of the solution is technology from Flexel, a Maryland-based company that had developed battery technology for the "Smart Dust" program — a National Security Agency (NSA) initiative designed to enable the use of very small electronic sensors, according to Flexel CEO Bob Proctor.
"The problem with making a very small electronic sensor is the power supply," Proctor said. "The two professors that founded the company started looking at alternative battery technology, because the battery became 'the problem.' For those types of small electronic circuits — think about the size of a dime — you need a thin-filmed power supply."
In seeking a solution, Flexel conducted research using ruthenium, a precious metal with attractive electrochemical properties that normally was deemed too expensive — about $100 per ounce — to be used in batteries, Proctor said. However, the Flexel team made an important discovery: simply spreading a thin layer of ruthenium on a surface produced the desired results.
"The reaction that ruthenium undergoes as part of the electrochemical process is a surface reaction," Proctor said. "So, if you think of a particle of this material, anything that's core inside the material is wasted — it's unnecessary.
"The insight was, 'If I can make a surface that's only an atomic layer or two of this material, it offers a lot of potential as a battery material, because now the cost becomes something that's very reasonable.' I'm only using micrograms of the material, so it becomes a cost-effective power supply."
Flexel also discovered that it was "just as easy" to make large printed sheets of the thin-battery material as it was to make the small, dime-sized sheets needed for the NSA project, Proctor said. In working with the DHS S&T, Flexel researchers found that ruthenium could be used as a catalyst in a disposable battery "with performance that was far better than we even projected in our original application," or as an active material in a rechargeable battery, Proctor said.
"So, it really depends on the application, but we can essentially modify the system for a rechargeable application or a disposable application," Proctor said. "In the disposable-application world, because of this catalyst action, the cost becomes very inexpensive relative to the capacity of the battery. It's pretty darned exciting, actually."