This is the holy grail a low cost, non-toxic, environmentally friendly way to produce high performance lithium ion battery anodes, said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.
The idea came to Favors six months ago. He was relaxing on the beach after surfing in San Clemente, California when he picked up some sand, took a close look at it and saw it was made up primarily of quartz, or silicon dioxide.
Favors’ research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles. Favors is focused on the anode of the battery. Graphite is the current standard material for the anode, but as electronics have become more powerful graphites ability to be improved has been virtually run out.
Researchers are now focused on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite. The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.
Favors set out to solve both these problems. He researched sand to find a spot in the USA where it is found with a high percentage of quartz. That took him to the Cedar Creek Reservoir, east of Dallas, where he grew up.
Sand in hand, Favors came back to the lab at UC Riverside and milled it down to the nanometer scale, followed by a series of purification steps changing its color from brown to bright white, similar in color and texture to powdered sugar.
After that, Favors ground salt and magnesium, both common elements found dissolved in sea water into the purified quartz. The resulting powder was then heated. With the salt acting as a heat absorber, the magnesium worked to remove the oxygen from the quartz, resulting in pure silicon.
The Ozkan team was pleased with how the process went. And they also encountered an added positive surprise. The pure nano-silicon formed in a porous 3-D silicon sponge like consistency. That porosity has proved to be the key to improving the performance of the batteries built with the nano-silicon.
The improved performance could mean expanding the expected lifespan of silicon-based electric vehicle batteries up to three times or more, which would be significant for consumers, considering replacement batteries cost thousands of dollars. For cell phones or tablets, it could mean having to recharge every three days, instead of every day.
The findings have been published in a paper entitled ‘Scalable Synthesis of Nano-Silicon from Beach Sand for Long Cycle Life Li-ion Batteries’, in the journal Nature Scientific Reports.
The Ozkan team is looking to produce larger quantities of the nano-silicon beach sand and is planning to move from coin-size batteries to pouch-size batteries that are used in cell phones.
Source: http://www.electronics-eetimes.com/en/surfer-triples-li-ion-battery-performance-with-sandy-solution.html?cmp_id=7&news_id=222921693&page=0
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