What was once thought of as a pipe dream is now reality: a team of material scientists at Vanderbilt University have created a supercapacitor made out of silicon.
Where batteries work on chemical reactions, supercapacitors store energy by gathering ions on the surface of porous material. This allows the technology to charge and discharge in minutes (as opposed to hours), and operate for a few million cycles (as opposed to thousand) before needing to be recharged.
Supercapacitors have seen some integration of late, such as storing energy captured by regenerative braking systems, providing the bursts of power that are necessary to adjust the blades of giant wind turbines to changing wind conditions, and more. But to be effective, the technology needs to be big, and so in its present state, it’s still too bulky to power consumer devices.
Silicon was tested out as a material that might be able to scale down the technology, but it provide too unstable for use as a supercapacitor. To overcome this hurdle, the Vanderbilt team thought it worthwhile to coat the material with a few nanometers of carbon; specifically the “magic” material graphene.
Now, this wasn’t just a random guess by the team. Carbon-based nanomaterials have actually received a lot of focus of late when it comes to improving the energy density of supercapacitors. The thinking is that since supercapacitors store electrical charges on the surface of their electrodes, by increasing the electrodes’ surface area, they will be able to, in turn, increase its energy density.
And the best way to increase an electrode’s surface area is to fill it with nanoscale ridges and pores. So why not take specially etched silicon and coat it with some graphene to stabilize the structure during use?
“If you ask experts about making a supercapacitor out of silicon, they will tell you it is a crazy idea,” said assistant professor Cary Pint, who headed the development team at Vanderbilt. “But we’ve found an easy way to do it.”
“The ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storage,” Pint adds. “Despite the excellent device performance we achieved, our goal wasn’t to create devices with record performance — it was to develop a road map for integrated energy storage. Silicon is an ideal material to focus on because it is the basis of so much of our modern technology and applications. In addition, most of the silicon in existing devices remains unused since it is very expensive and wasteful to produce thin silicon wafers.”
Should the technology make its way into the public’s smartphones and tablets, the Vanderbilt solution can be built right into the very microcircuitry that it’s tasked with powering. For now, though, Pint and his group are using their approach to develop energy storage that can be formed in the excess materials or on the unused back sides of solar cells and sensors, with the goal being to store the excess electricity that the cells generate at midday, and release this power when demand peaks in the afternoon.
The group’s study was published in the October 22nd issue of Scientific Reports, under the title “Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.”
Story via: Vanderbilt.edu
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