What’s more, reducing the amount of active, energy-storing material has the counterintuitive effect of increasing the composite’s storage capacity. If too much lithium is removed from conventional cobalt oxide materials, the material degrades and quickly loses its ability to fully charge and discharge. The inactive material makes it possible to use much more of the lithium without damaging the material.
The electrode material can store 45 percent to 50 percent more energy than the best electrodes in laptop batteries. In terms of an entire battery cell–given that the positive electrode represents less than half of the total weight and volume of a battery cell–the total energy storage of the battery can be improved by 20 percent to 30 percent, Henriksen says.
The researchers’ next step is improving the rate at which the composite material can be charged and discharged so that it can be used in hybrid vehicles. As it’s made now, the Argonne material can be completely discharged in about three hours–fast enough for laptops but far too slow for a car. Discharging rates will need to be at least three times faster, and likely more, for the technology to work in plug-in hybrids, vehicles in which the battery can be recharged from a conventional electrical outlet.
Yet-Ming Chiang, a professor of materials science and engineering at MIT, says the new material is “a significant improvement over lithium cobalt oxide” for laptop batteries. “If you think about it in terms of a field that grows 8 to 9 percent per year, you just saved yourself three years. You may have leapfrogged the competition,” he says. “I’m sure that anybody who makes cell phone and laptop batteries would be very happy to have that kind of an edge.”
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