Running on air

A new type of air-fuelled battery could give up to 10 times the energy storage of designs currently available.

This step-change in capacity could pave the way for a new generation of electric cars, mobile phones and laptops.

The research work, funded by the Engineering and Physical Sciences Research Council (EPSRC), is being led by engineers at the University of St Andrews with partners at Strathclyde and Newcastle.

The new design has the potential to improve the performance of portable electronic products and give a major boost to the renewable energy industry. The batteries will enable a constant electrical output from sources such as wind or solar, which stop generating when the weather changes or night falls.

The research team explained the improved capacity is due to a component that uses oxygen drawn from the air during discharge, replacing one chemical constituent used in rechargeable batteries. It is claimed that not carrying the chemicals around in the battery offers more energy for the same size battery. The researchers believe this is a significant development for electric car developers who have struggled for a long time to find smaller and lighter batteries with all the necessary charge capacity.

The St Andrews engineers said their STAIR (St Andrews Air) cell should be cheaper than current rechargeables. The new component is made of porous carbon, which is less expensive than the lithium cobalt oxide it replaces.

The four-year research project, which reaches its halfway mark in July, builds on the discovery at the university that the carbon component’s interaction with air can be repeated, creating a cycle of charge and discharge. The research team claims that its recent work on the technology has more than tripled the capacity to store charge in the STAIR cell.

‘Our target is to get a five to tenfold increase in storage capacity, which is beyond the horizon of current lithium batteries,’ said principal investigator Peter Bruce, a professor in the chemistry department at the University of St Andrews. ‘Our results so far are very encouraging and have far exceeded our expectations. The key is to use oxygen in the air as a reagent, rather than carry the necessary chemicals around inside the battery.’

The oxygen, which will be drawn in through a surface of the battery exposed to air, reacts within the pores of the carbon to discharge the battery.

‘Not only is this part of the process free, the carbon component is much cheaper than current technology,’ added Bruce. He estimates that it will be at least five years before the STAIR cell is commercially available.

The researchers still need to gain a better understanding of how the chemical reaction of the battery works and investigate how to improve it. The research team is also working towards making a STAIR cell prototype suited for small applications such as mobile phones or MP3 players.