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A new use for rice — lithium ion batteries

From rice husk to refined silicon (PNAS).

From rice husk to refined silicon (PNAS).

Discarded rice husks could become standard ingredients for lithium ion batteries.

Researchers in Korea report that rice husks — the tough, protective layer covering a rice kernel — are ideal sources of silicon for high-capacity lithium battery anodes. Their findings are published in PNAS Early Edition.

Husks protect rice kernels from bacteria and insects, while allowing air and moisture to penetrate through tiny pores in layers of silica. This three dimensional structure maintained its shape even as the researchers processed the silica husks into purified silicon.

During cycling, the capacity of silicon anodes usually fades because the volume of silicon alloys changes dramatically, up to 300%, during charging and discharging. This can fracture the silicon alloys and create unstable connections within the battery.

Thanks to previous work, nanostructured Si materials are already known to work well as high-performance lithium ion battery anodes. But in the process outlined by Jang Wook Choi, Dae Soo Jung, and colleagues, the nanopores are preserved from the rice’s natural design. The researchers point out that, with more than 420 million metric tons of rice grown each year, “the readily available amount of the rice husk originated silicon […] is at least several orders of magnitude larger than the current demand for LIB anode raw materials.”

According to Wook Choi, this paper highlights the value of interdisciplinary research. He hit on this “crazy idea” only by collaborating with agricultural scientists. “I learned that interdisciplinary research with different backgrounds and expertise could make unexpected breakthroughs.”

The advance, he hopes, will lead to longer lasting batteries for cellphones, laptops, and electrical vehicles. He has already received some messages of interest from major battery makers and agricultural ministers from the government of Korea.

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