For the first time, MIT researchers have shown they can genetically engineer viruses to build both the positively and negatively charged ends of a lithium-ion battery.
The new virus-produced batteries have the same energy capacity and power performance as state-of-the-art rechargeable batteries being considered to power plug-in hybrid cars, and they could also be used to power a range of personal electronic devices, said Angela Belcher, the MIT materials scientist who led the research team.
The new batteries, described in the April 2 online edition of Science [abstract], could be manufactured with a cheap and environmentally benign process: The synthesis takes place at and below room temperature and requires no harmful organic solvents, and the materials that go into the battery are non-toxic.
In a traditional lithium-ion battery, lithium ions flow between a negatively charged anode, usually graphite, and the positively charged cathode, usually cobalt oxide or lithium iron phosphate. Three years ago, an MIT team led by Belcher reported that it had engineered viruses that could build an anode by coating themselves with cobalt oxide and gold and self-assembling to form a nanowire.
In the latest work, the team focused on building a highly powerful cathode to pair up with the anode, said Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering. Cathodes are more difficult to build than anodes because they must be highly conducting to be a fast electrode, however, most candidate materials for cathodes are highly insulating (non-conductive).
To achieve that, the researchers, including MIT Professor Gerbrand Ceder of materials science and Associate Professor Michael Strano of chemical engineering, genetically engineered viruses that first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conductive material.
Because the viruses recognize and bind specifically to certain materials (carbon nanotubes in this case), each iron phosphate nanowire can be electrically “wired” to conducting carbon nanotube networks. Electrons can travel along the carbon nanotube networks, percolating throughout the electrodes to the iron phosphate and transferring energy in a very short time.
The viruses are a common bacteriophage, which infect bacteria but are harmless to humans.
…Now that the researchers have demonstrated they can wire virus batteries at the nanoscale, they intend to pursue even better batteries using materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate, said Belcher. Once that next generation is ready, the technology could go into commercial production, she saidBugs Build Batteries
By Lauren Cahoon
ScienceNOW Daily News
3 April 2009
Most commercial rechargeable batteries pass a lithium ion from the anode, the negatively charged terminal, to the positively charged cathode and have to be made at high temperatures. Materials chemist Angela Belcher of the Massachusetts Institute of Technology in Cambridge and her colleagues decided to try making a better battery by using biological processes. This approach is logical, Belcher says, because some of the materials in batteries, such as phosphate and iron, are present in living systems and can be easily manipulated by organisms.
The team first created an anode by genetically engineering the M13 virus, a common parasite of bacteria, to attract cobalt oxide and gold to its outer shell and then assemble into films and sheets (Science, 12 May 2006, p. 885).
The next step was to tackle the positively charged cathode, which is more challenging because it needs to be highly conductive. The team engineered the M13 viruses to accumulate ions of iron phosphate and to latch onto a highly conductive network of carbon nanotubes. Electrons could travel quickly through this system and boost the cathode's capacity. In fact, Belcher's battery had the same power performance as commercially available lithium ion batteries and could be charged and discharged at least 100 times without wearing out, the team reported online yesterday in Science.
The virus-built technology may provide the first biological method for producing batteries. Belcher notes that the entire system, with the exception of the carbon nanotubes, is created at room temperature and uses only water as a solvent. And when the batteries die and degrade, they don't leave behind toxic chemicals. "This is definitely a very clean approach," Belcher says.
However, she cautions that the technology isn't yet useful as a commercial application. Because the virus battery only matches the capacity and power performance of those available on the market, "we're not going to scale up this material," says Belcher. "It wouldn't gain us anything in terms of performance."
Other experts agree that Belcher's discovery isn't going to change the face of the battery industry overnight. "It is of scientific curiosity," says M. Stanley Whittingham, a chemist at the Institute for Materials Research at Binghamton University in New York state. To change battery technology, he says, the researchers need to build a higher capacity cathode.
References : http://sciencenow.sciencemag.org/cgi/content/full/sciencenow;2009/403/1
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