Page last updated at 19:20 GMT, Thursday, 2 April 2009 20:20 UK

Virus battery could 'power cars'

Professor Belcher holds up the battery
Professor Belcher holds up the battery

Viruses have been used to help build batteries that may one day power cars and all types of electronic devices.

The speed and relatively cheap cost of manufacturing virus batteries could prove attractive to industry.

Professor Angela Belcher, who led the research team, said: "Our material is powerful enough to be able to be used in a car battery."

The team from MIT in the US is now working on higher power batteries.

Scientists at MIT used the viruses to build both the positively and negatively charged ends of a battery, the cathode and anode, the journal Science reports.

A battery typically has four key components - the anode and cathode, an electrolyte that flows between them, and a separator to keep the anode and cathode apart.

Essentially, a battery turns chemical energy into electrochemical energy when an electron flow passes from the negative end to the positive end through a conductive chemical, the electrolyte.

Researchers constructed a lithium-ion battery, similar to those used in millions of devices, but one which uses genetically engineered viruses to create the negatively charged anode and positively charged cathode.

Virus battery
The virus battery could be commercialised

The virus is a so-called common bacteriophage which infects bacteria and is harmless to humans.

Three years ago the MIT scientists manipulated genes inside a virus that coaxed the particles to grow and self-assemble to form a nanowire anode one-tenth the width of a human hair.

The microbes are encouraged to collect exotic materials - cobalt oxide and gold - and because the particles are negatively charged, they can be formed into a dense, virus-loaded film which acts as an anode and "grows" on a polymer separator.

Researchers, including MIT Professor Gerbrand Ceder and Associate Professor Michael Strano, have now developed a highly powerful cathode.

The work was more difficult because the material had to be highly conductive in order to be effective and most candidate materials for cathodes are highly insulating.

The virus picks up a carbon nanotube after being genetically engineered

The virus was coaxed into binding with iron phosphate and then carbon nanotubes to create a highly conductive material.

The batteries have the same energy capacity and power performance as rechargeable batteries used to power plug-in hybrid cars.

The prototype battery is currently the size of a coin but the scientists believe it can be scaled and be used to create flexible batteries that can take the shape of their container, which is perfect for mobile or small devices.

The scientists have also been able to create micro-batteries which could be used to power a future generation of tiny devices.

"The advantage of using genetics is that things can be made better and better," explained Professor Belcher.

"You are not stuck with a particular material; you have selection and evolution on your side because it can be genetically engineered."

The researchers are now looking for better materials to work with the viruses to create a next-generation battery, which is even higher powered.

"Scale is the issue," admitted Professor Belcher. "But we are not going to scale until we have the right material. We believe this is possible and has commercial implications otherwise we would not be researching in this area."

Currently, the virus battery can only be charged and discharged about 100 times before it begins to lose its capacity to store a charge, but Professor Belcher said "we expect them to be able to go much longer".

The process to build the batteries uses no harmful or toxic materials and so is attractive from an environmental point of view.

Professor Belcher said: "To us, the environmental aspects are very important.

"Put simply, we can't do anything that kills our organisms."

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