Battery electrodes self-assembled by viruses

06 April 2006
NewScientist.com news service
Stu Hutson

Genetically modified viruses that assemble into electrodes could one day revolutionise battery manufacturing.

Researchers in the US have created viruses that automatically coat themselves in metals and line up head to tail to form an efficient battery anode – the negatively charged component that channels electrons to generate current. These nanowires could be used to make revolutionary new forms of lithium-ion batteries, the researchers say.

"Now it's simply a matter of designing the other components, and we'll be able to form batteries by simply pouring all the ingredients together and letting them self-assemble," says Angela Belcher, a biological engineer at MIT who led the research. "Plus we can make them at room temperature in very safe conditions, instead of the high temperatures and dangers usually associated with battery production."

Belcher's team genetically modified tube-shaped viruses that normally infect bacteria to create the electrodes. They introduced snippets of single-stranded DNA that caused the viruses to manufacture specific molecules on their outer coating that attach to cobalt ions and gold particles. This combination turns the virus into an efficient anode as they provide an ideal conduit for electrons.

Going for gold

To find the right genetic code to produce the gold-clinging molecules, or complexes, Belcher's team exposed billions of viruses with slightly different DNA to gold and then extracted genetic material from the ones that most strongly interacted with the metal. To create the cobalt-clinging complexes, the team created genetic code from scratch by mimicking the code which enables animal cells to harvest calcium. This is because cobalt can be harvested in a similar way to calcium.

The genetic material added to the viruses can easily be interchanged, the researchers say, so it should be relatively simple to create other electronic components, including a positively charged battery electrode (cathode) using the technique.

This flexibility is one of the most powerful aspects of the work, says Trevor Douglas, a pioneer of nanomaterial chemistry at Montana State University in the US, who was not involved with the work. "This proves that you can harness these viruses to do many different things," he says. "It raises the bar for everyone else in the field. We can't be satisfied proving principles – we have to move this on to actually utilising these principles."

The other important aspect, he says, is scalability. The team modified the viruses to cling to a surface – producing 10-centimetre-long anode sheets. "They took this from the nanoscale to the macroscopic, which could mean batteries of every shape and size," Douglas adds. "It's not hard to imagine these being produced on a factory-scale."

But the research may also be useful for other energy technologies. Belcher is currently investigating how to use viruses to create self-assembling solar cells.

Journal reference: Science (DOI: 10.1126/science.1122716)
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