Jung et al., PNAS, 2013.
Generation of 3D nanoporous Si from a rice plant. (A) Photographs of rice plant. (B) Photograph of rice husks obtained after milling. (Upper Inset) Optical microscope image showing the morphological characteristic of outer/inner surfaces of a rice husk. (Lower Inset) Circular chart indicating the com- position of rice husks. (C) Optical microscope image of a rice husk shell magnified from the black box in B. (Inset) Si-mapped SEM-EDS image suggesting that Si exists mostly along the outer rugged surfaces of rice husks. (D) A series of photographs summarizing the procedures of synthesizing nanostructured Si from rice husks. (Left to Right) Pretreated rice husks by an acid-leaching process, rice husk-originated silica by a thermal decomposition process, a Si/MgO mixture formed after a magnesiothermic reduction process, and the final 3D porous Si obtained after an additional two-stage acid etching process.
You’ve heard of rice pudding. But rice … batteries?
This is Sandra Tsing Loh with the Loh Down on Science.
A grain of rice is born with a hull that’s removed during processing. And for good reason! Its outer layer is made of silica—the stuff of sand and glass. Ouch! Interestingly, the unique structure is peppered with nanoscopic pores. It keeps pests out but lets moisture and air in. Turns out, it also makes a great battery part!
Meet Jang Choi from the Korea Advanced Institute of Science and Technology. He figured out how to extract this silica layer as-is. Then he removed oxygen molecules to turn it into silicon—without changing its holey design. He plunked the silicon into otherwise normal lithium batteries as electrodes. They worked! Previous attempts to use silicon in batteries have fallen flat. There’s something about the naturally pitted rice-based silicon that makes it work.
Why bother? Silicon can provide ten times the charge of today’s electrodes.
The downside? They might make your iPad display a tad, uh, grainy. Sorry!
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The Loh Down on Science is produced by LDOS Media Lab, in partnership with the University of California, Irvine, and 89.3 KPCC. And made possible by the generous support of the Gordon and Betty Moore Foundation.