Thursday, July 11, 2013: Lithium-ion (Li) batteries play an important role in today’s technological progress as they power the electronics and hybrid electric vehicles industries. With an aim to increase battery capacity, many researchers have so far struggled to replace the carbon anode in today’s technology with a silicon anode which has the capacity to hold 10 times more charge. Next-generation high-capacity lithium-ion batteries thus developed are expected to speed the development of more sophisticated portable electronics.
A team of scientists from South Korea have now proposed to use layers of silicon dioxide, or silica as a source of silicon. Usually, the silica-rich husks left over after rice is harvested are turned into fertiliser additives. These silica layers are said to be uniquely porous at the nano-scale level.
“Silicon converted from the silica in rice husks may be able to resist this volume change, says Jang Wook Choi at the Korea Advanced Institute of Science and Technology in Daejeon, South Korea. The tiny holes in the husk that allow the rice kernel to breathe should also mean that any derived silicon would also be porous. Its holes could provide places for the ions to reside on the electrodes during charging and discharging, preventing the volume from significantly changing,” said a report by New Scientist.
The team chemically converted the rice husk silica into pure silicon and then fashioned battery electrodes out of the material. “It showed no capacity fade even after 200 charge-drain cycles. A synthetic silicon electrode used for comparison had a higher initial charge capacity but faded badly: it began performing worse than the rice-husk electrode after 10 to 15 cycles,” the report added.
Whether the rice husk electrodes can be made commercially competitive is still an open question, but as “most silicon is produced from similar thermal treatment processes so we should be able to find reasonable competitiveness,” said Choi.
These findings were published in the Proceedings of the National Academy of Sciences.
