A new type of air-fuelled battery could give up to ten 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 researchers
at the University of St Andrews with partners at Strathclyde and Newcastle.
Diagram of the STAIR (St Andrews Air) cell. Oxygen drawn from the air reacts within the porous carbon to release the electrical charge in this lithium-air battery.
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.
Improved capacity is thanks to the addition of a component that uses oxygen
drawn from the air during discharge, replacing one chemical constituent used
in rechargeable batteries today. Not having to carry the chemicals around in
the battery offers more energy for the same size battery. Reducing the size
and weight of batteries with the necessary charge capacity has been a long-running
battle for developers of electric cars.
The STAIR (St Andrews Air) cell should be cheaper than today’s rechargeables
too. The new component is made of porous carbon, which is far less expensive
than the lithium cobalt oxide it replaces.
This 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. Subsequent
work has more than tripled the capacity to store charge in the STAIR cell.
Principal investigator on the project, Professor Peter Bruce of the Chemistry
Department at the University of St Andrews, says: “Our target is to get
a five to ten fold increase in storage capacity, which is beyond the horizon
of current lithium batteries. Our results so far are very encouraging and have
far exceeded our expectations.”
“The key is to use oxygen in the air as a re-agent, rather than carry
the necessary chemicals around inside the battery,” says Bruce.
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,” says Bruce. He estimates that it will be at
least five years before the STAIR cell is commercially available.
The project is focused on understanding more about how the chemical reaction
of the battery works and investigating how to improve it. The research team
is also working towards making a STAIR cell prototype suited, in the first instance,
for small applications, such as mobile phones or MP3 players.