First Supercapacitor that can even store electricity inside a silicon chip

A group of researchers at the Vanderbilt University in Nashville, Tenessee has designed a supercapacitor made primarily of silicon  with the microelectronic circuitry that it powers. In fact, it should be possible to construct these power cells out of the excess silicon that exists in the current generation of solar cells, sensors,mobile phones and a variety of other electromechanical devices, providing a considerable cost savings. 

Silicon chip with porous surface next to the special furnace where it was coated with graphene to create a supercapacitor electrode

This is a wonderful step in the field of semi conductor electronics. Just imagine about the solar cells that produce electricity 24/7, not just when sun is shining. Mobile phones with built-in power cells that can recharge in seconds and work for weeks between charged. Amazing, isn't it. :)  

Assistant Professor Cary Pint

"If you ask experts about making a supercapacitor out of silicon, they will tell you it is a crazy idea". Said Cary Pint, the assistant professor of mechanical engineering who headed the development. "But we have found an easy way to do it."

As we all know batteries store energy in chemical reactions. But on the other hand, supercapacitors store electricity by assembling ions on the surface of a porous material. As a result, they tend to charge and discharge in minutes, instead of hours and operate for a few million cycles, comparatively  less when compared to that of batteries. These properties will be able to help this "supercap" to capture markets and we will be able to see amazing applications of this little master. 

Initially silicon wasn't their choice. Research to improve the energy density of super capacitors has focused more on nanomaterials like nanotubes and graphene. Because these devices store electrical energy on the surface of their electrodes. But there was always a challenge for this choice. Mainly assembling the materials. Not only that, doubts where always present about repeating the same success even if the first attempt will be a mark. So Pint and his research team-graduate students Landon Oakes, Andrew Westover and post-doctoral fellow Shahana Chatterji-decided to take a radical different approach. Their choice was porous silicon, a material with a controllable and well-defined nanostructure made by electrochemically etching the surface of a silicon wafer. This allowed them to create surfaces with optimal nanostructure for supercapacitor electrodes. But still there was a major problem. Silicon is generally considered unsuitable for use in supercapacitors because it reacts readily with some of chemicals in the electrolytes. But Pint and his team were determined and his experience in growing nanostructures helped him in this problem. They decided to coat the porous silicon surface with carbon. The amazing thing was, it stabilized the silicon surface which will avoid the further chemical reactions with electrolytes. 

Transmission electron microscope image of the surface of porous silicon coated with graphene. The coating consists of a thin 5-10 layers of graphene which filled pores with diameters less than 2-3 nanometers architecture of the underlying silicon

Currently research are still going on to develop energy storage that  can be formed in the excess materials on the unused back sides of solar cells and sensors. The supercapacitors would store excess the electricity that the cells generate at midday and release it when the demand peaks in afternoon. That will be another breakthrough we cant wait until it get released. It will be definitely energy saving measure that can help a lot.   

Supercapacitor research group