Graphene nanoribbons could double Li-ion battery capacity

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Rice University researchers have used ribbons of graphene to boost the efficiency of lithium ion batteries.

The nanoribbons, when combined with a tin oxide solution, have been shown to double the capacity for lithium compared to standard anodes used in current commercial batteries. "After 50 charge/discharge cycles, the test units retained a capacity that was still more than double that of the graphite currently used for lithium battery anodes," noted Rice chemist James Tour. Tour and his colleagues developed a method for unzipping nanotubes into graphene nanribbons, or GNRs, in 2009. Since then, they have found a way to make them in bulk and are moving toward commercial applications. In the new experiments, the team mixed GNRs with tin oxide particles about 10nm wide with a cellulose gum binder and a bit of water. They then spread this on a current collector and encased it in a button style battery. Not only did the GNRs separate and support the tin oxide, they also helped deliver Li-ions to the nanoparticles. Lab tests showed initial charge capacities of more than 1,520mAh/g. Over repeated charge/discharge cycles, the material settled into a solid 825mAh/g. "It took about two months to go through 50 cycles," said lead researcher Jian Lin, who believes it could handle many more without losing significant capacity.