May 21, 2009 Rechargeable lithium-ion batteries are the preferred power storage technology for the vast majority of portable devices, such as cell phones, laptop computers and MP3 players. They have also made their way into electric cars, but even with recent developments making them more effective, storage capacity continues to remain a problem. Now researchers at the University of St Andrews, with associates at Strathclyde and Newcastle, have developed a new type of air-fueled battery that could provide up to 10 times the energy storage of existing designs, paving the way for a new generation of electric cars and portable devices.

Dubbed the STAIR (St Andrews Air), the new battery improves capacity by adding a carbon component. Oxygen drawn in through a surface of the battery exposed to air reacts within the pores of the carbon to discharge the battery. The discovery that the carbon component’s interaction with air can be repeated, creating a cycle of charge and discharge, led to the development of the new battery.

The technology should result in cheaper batteries since this process is free and the carbon component is less expensive than the lithium cobalt oxide used in lithium-ion batteries. Also, by replacing one of the chemical components of rechargeable batteries, more energy can be created by the same-sized battery. Reducing the size and weight of batteries, without compromising their charge capacity, should allow developers of electric cars to produce vehicles with greater range and provide longer life for portable devices.

Initial results from the research project found a capacity-to-weight ratio of 1,000 milli-amp/hours per gram of carbon (mA/hours/g), while recent work achieved up to 4,000 mA/hours/g. Although the STAIR and lithium cobalt oxide technologies work very differently, the results equate to an eight-fold increase using the porous carbon electrode compared to the lithium cobalt oxide electrode found in standard cell phones.

The researchers believe the new design not only has the potential to improve the performance of portable electronic products, but also provide a major boost to renewable energy from sources, such as wind and solar by getting around the problem of intermittent supply when the weather changes or night falls. By discharging batteries to provide electricity and recharging them when the wind blows or sun shines, renewable energy becomes a much more viable option.

The researchers estimate that it will be at least five years before the STAIR cell is commercially available.

Darren Quick