Soon, sand may power your cell phone

Imagine if you only had to charge your cell phone or tablet every three days? A new sand-based battery may make it possible.

PTI| Last Updated: Jul 09, 2014, 14:30 PM IST

Washington: Imagine if you only had to charge your cell phone or tablet every three days? A new sand-based battery may make it possible.

Scientists have used sand to create a lithium ion battery that outperforms the current industry standard by three times.
"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 Ozkan and Mihri Ozkan, both engineering professors at University of California, Riverside`s Bourns College of Engineering.

Graphite is the current standard material for the anode, but as electronics have become more powerful graphite`s ability to be improved has been virtually tapped out.

Researchers are now focused on using silicon at the nanoscale, or billionths of a metre, 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 researched sand to find a spot in the US 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.
He came back to the lab at UC Riverside and milled the sand down to the nanometre scale, followed by a series of purification steps changing its colour from brown to bright white, similar in colour and texture to powdered sugar.

After that, he ground salt and magnesium, both very 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 pure nano-silicon formed in a very 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, researchers said.

The improved performance could mean expanding the expected lifespan of silicon-based electric vehicle batteries up to 3 times or more.

For cell phones or tablets, it could mean having to recharge every three days, instead of every day, researchers said.

The team is now trying 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.
The findings were published in the journal Nature Scientific Reports.