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Making Li-ion Batteries from Recycled Rice Husks

Li-ion battery from rice husks

These clockwise images show rice, rise husks, white silica powders extracted from rice husks, brown silica powder, porous silicon under scanning electron microscope and an example of using silicon anode in lithium-ion batteries for hybrid electric vehicle. *Image source: Dae Soo Jung

A new study demonstrated that silica in rice husks can be converted into silicon and used as anode material for high-capacity lithium-ion batteries. The high-capacity Li-ion battery has significant impact on the development of portable electronics and hybrid electric vehicle (HEV).

Rice is a world-widely grown crop that has an annual output of about 4.22 billion tons. Each year, large quantities of wasted rice husks are generated with the high annual production of rice. Professor Choi Jang Wook and colleagues from Korea Advanced Institute of Science and Technology, found that 3D porous nano-silicon can be obtained by reducing silica extracted from rice husks. The study, published on PNAS of July 8th, thoroughly introduced how to achieve silicon from rice husks and the uniqueness of the nano-scale, 3D porous structure silicon.

Rice husks have a unique silica layer, which occupy about 19.5 percent of the total weight or rice husks. This silica layer is featured in nano-porosity to protect the inside of rice kernel from bugs and bacteria and allow air and water ventaliation. Hence, silicon reduced from rich husks has 3D nano-porous structure naturally.

The researchers utilized acid and heat treatment to extract silica from rice husks and then separate silicon from the silica. This process preserved that original 3D porous nanostructure of the silica layers and such structure can provide good electronic conductivity. Therefore, the silicon obtained from rice husks is a good fit for constructing high-capacity Li-ion batteries.

The authors believe that as a highly abundant and as yet unexploited resource, recycled rice husks can meet the growing demand of silicon for Li-ion batteries and thus support the development of portable consumer electronics and hybrid electric vehicles.

Choi Jang Wook noted that this technology would show its business significance as silicon anodes in Li-ion batteries become more popular. At that time, such silicon material with superior performance and low price will dominate the market – companies using this kind of silicon to produce Li-ion battery anodes will benefit directly from this technology. In the meanwhile, related agricultural sectors and waste management sectors can also save some work.

Image source: Shutterstock