Battery boost from coated silicon

The super-capacitors could help store energy harvested by solar power plants

Phone batteries that recharge in minutes and last for weeks could result from work on silicon super-capacitors.

Created by American scientists, the components exploit properties of carefully engineered silicon slices to hold and quickly deliver a charge.

Renewable energy sources could also benefit from the work on the cheaper super-capacitors.

The silicon components should be easy to add to existing chip-production systems, said the researchers.

Solar storage

Super-capacitors built from carbon are already used as energy storage systems in electric vehicles and in wind turbines to ensure blades turn smoothly, but their bulk and cost have limited them to these niche applications.

Scientists in the engineering department at Vanderbilt University in Tennessee tested different materials to see if they could be used to reduce the cost and size of these super-capacitors.

Silicon became a good candidate when the Vanderbilt team found a way to apply a coat of graphene that was only a few nanometres thick. This coating was needed to stop the silicon reacting with the chemicals that provide the ions used to store an electrical charge.

The team, headed by engineering professor Cary Pint, used porous silicon in their research because the method of etching billions of tiny pits on to the material is well established. All those nano-scale features give the material a huge surface area relative to its size and help it store a significant electrical charge.

Writing in a paper in the journal Nature, the scientists explained how the coating bestowed on the silicon properties similar to those seen in commercial super-capacitors. It allows them to dispense their stored power quickly and last much longer than current re-chargeable batteries.

The team is now looking into ways to integrate the coated silicon into existing manufacturing processes so the super-capacitors can be more widely used in gadgets such as phones.

One of the first applications of the work could be as a storage system for solar power plants. Super-capacitors on the rear of solar cells could store power as it is collected and then dispense it during the night when demand grows.

"All the things that define us in a modern environment require electricity," said Prof Pint. "The more that we can integrate power storage into existing materials and devices, the more compact and efficient they will become."