Soon, mobiles that can charge in seconds and work for weeks

Washington – Researchers have invented a novel supercapacitor design which raised the possibilities of developing solar cells that produce electricity 24 by 7, not just when the sun is shining and mobile phones with built-in power cells that recharge in seconds and work for weeks between charges.

Cary Pint, the assistant professor of mechanical engineering at Vanderbilt University, and his team have developed the first supercapacitor that is made out of silicon so it can be built into a silicon chip along 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.

Instead of storing energy in chemical reactions the way batteries do, “supercaps” 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, instead of a few thousand cycles like batteries.

Supercapacitors still lag behind the electrical energy storage capability of lithium-ion batteries, so they are too bulky to power most consumer devices. However, they have been catching up rapidly.

Research to improve the energy density of supercapacitors has focused on carbon-based nanomaterials like graphene and nanotubes. Because these devices store electrical charge on the surface of their electrodes, the way to increase their energy density is to increase the electrodes’ surface area, which means making surfaces filled with nanoscale ridges and pores.

“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,” Pint said.

The study is published in journal Scientific Reports.