Their work is partly of an intensifying push to build a better battery — not only for portable electronics but also for storing solar and wind power for times when the sun doesn't shine and the wind doesn't blow. Universities, start-ups and major companies are working with new materials, such as vanadium, or tweaking the lithium-ion battery that Sony introduced more than 20 years ago.
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In a new breakthrough, the Stanford team says it's using nanotechnology to create a pure lithium battery — an advance sought for decades because of its light weight and superior efficiency.
"If we can triple the energy density and simultaneously decrease the cost four-fold, that would be very exciting," Chu said in a university announcement. "We would have a cellphone with triple the battery life and an electric vehicle with a 300-mile range that cost $25,000 — and with better performance than an internal combustion engine car getting 40 mpg."
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Today's lithium batteries only have lithium in the electrolyte, which is one of three basic parts of a battery. The electrolyte provides electrons, while the anode discharges them and the cathode receives them.
The Stanford team is also putting lithium in the anode. This is tricky, because while silicon and graphite — two commonly used materials in anodes — expand during charging, lithium expands even more and can also eat up the electrolyte.
The solution? Cui's lab has built a honeycomb-like microscopic layer — called "nanospheres" — that creates a flexible non-reactive film to protect the unstable lithium. It describes the work in a study published this week in the journal Nature Nanotechnology.
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The layer improves battery efficiency. To become commercially viable, batteries generally need to put back 99.9% of the lithium lost in use during recharging. Previous anodes of unprotected lithium got about 96% efficiency, but Cui says his version is approaching 99.6%, and he expects it can reach 99.9% in two years.
Some experts are skeptical. John Goodenough, who helped invent the original lithium-ion battery of the late 1970s and is still working to improve the technology, said Cui's protective layer is not an "ideal" solution.
"It's not clear he has achieved that goal with a sufficiently cheap process," says Goodenough, now a 92-year-old professor of materials science at the University of Texas-Austin.
The battery world, like other cutting-edge technology, has seen its share of failures. In October 2012, lithium-ion battery manufacturer A123 filed for bankruptcy after spending $132 million in federal stimulus funds. Two months later, Wanxiang America, the U.S. arm of a Chinese automotive parts giant, bought A123's technology.
Yet Cui, whose lithium anode work has not yet received any federal funds, knows how to commercialize his research. He's the founder of Silicon Valley start-up Amprius, which received $30 million in venture capital in January — in addition to prior funding — to sell a new type of long-lasting lithium-ion battery. Amprius' board includes Chu, who won the 1997 Nobel Prize in physics and returned to Stanford after leaving the Obama administration.