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Rice Husks Could Lead to Longer Battery Life

Rice Husks Could Lead to Longer Battery Life

Image source: flickr.com/photos/sedap

An agricultural waste product, such as rice husks, is an unlikely source for a material that could lead to better, and longer lasting, batteries. But the results of a recent study suggest that those same rice husks could one day be used to produce silicon anodes for lithium batteries.

Researchers at the Korea Advanced Institute of Science and Technology (KAIST) were recently able to convert the silica from rice husks into pure silicon, and then fashioned it into anodes for a high-capacity lithium-ion battery. The resulting battery exhibited no reduction of capacity after 200 charge cycles, which suggests that the husk-based silicon could be the answer to more powerful and longer lasting batteries.

The fading of capacity in batteries with silicon electrodes is an issue that has plagued previous attempts to use the material (instead of graphite) in lithium batteries, because of tiny fractures that build up in them. But the silicon made from the rice husks have nanoporous layers that can allow ions to move freely and not fracture the electrodes.

“Silicon has attracted much attention as anode material for next generation lithium ion secondary batteries because it exhibits 3~5 times higher capacity than conventional graphene. The high capacity will pave the way to lithium secondary batteries with higher energy densities than conventional batteries. It is anticipated that the application of silicon batteries will yield electronic devices with a longer duration for use in addition to electronic vehicles boasting longer mileage.” – KAIST

The process to convert the silica into silicon is an energy-intensive one, similar to that used to produce other types of silicon, so it isn’t quite a viable alternative yet, but the researchers believe they will be able to “find reasonable competitiveness” in the market. If so, the resulting business could take a waste product (estimated at 108 tons per year globally) and turn it into a highly desirable material for the next generation of high capacity batteries.

“In an effort to recycle rice husks for high-value applications, we convert the silica to silicon and use it for high-capacity lithium battery anodes. Taking advantage of the interconnected nanoporous structure naturally existing in rice husks, the converted silicon exhibits excellent electrochemical performance as a lithium battery anode, suggesting that rice husks can be a massive resource for use in high-capacity lithium battery negative electrodes.”

The results are published at PNAS: Recycling rice husks for high-capacity lithium battery anodes

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