Published on November 18th, 2013 | by James Ayre2
Lithium-Air Batteries Get Big Boost From Genetically Modified Viruses
November 18th, 2013 by James Ayre
Lithium-air battery performance can be greatly enhanced through the use of genetically modified viruses, according to new research from MIT. By using genetically modified viruses, it’s possible to create nanowires — wires roughly the size of red blood cells that can function as electrodes — with a much greater surface area than those produced via normal means.
These rough, spiky-surfaced nanowires thus confer a greatly increased ability to charge and discharge — potentially significantly cutting charge times. The new virus-aided method of production also has a number of other advantages: it doesn’t rely on high temperatures of hazardous chemicals, and it can be carried out at room-temperature via a water-based process.
Lithium-air batteries have significant upsides as compared to conventional batteries — most notably, they possess significantly increased power per battery weight. But a number of barriers have remained in place, preventing them from entering wide-scale use. The most significant of these barriers has been the need to develop better and more durable materials for the batteries’ electrodes. Another major barrier is working out a way to increase the number of charge-discharge cycles that the batteries can withstand.
But now, researchers at MIT have apparently found a way to address these barriers — through the addition of genetically modified viruses during the production of nanowires. “The key to the new work was to increase the surface area of the wire, thus increasing the area where electrochemical activity takes place during charging or discharging of the battery.”
MIT provides more info:
The researchers produced an array of nanowires, each about 80 nanometers across, using a genetically modified virus called M13, which can capture molecules of metals from water and bind them into structural shapes. In this case, wires of manganese oxide — a “favorite material” for a lithium-air battery’s cathode, Belcher says — were actually made by the viruses. But unlike wires “grown” through conventional chemical methods, these virus-built nanowires have a rough, spiky surface, which dramatically increases their surface area.
The increase in surface area produced by this method can provide a big advantage in lithium-air batteries’ rate of charging and discharging. But the process also has other potential advantages. Rather than isolated wires, the viruses naturally produce a three-dimensional structure of cross-linked wires, which provides greater stability for an electrode.
A final part of the process is the addition of a small amount of a metal, such as palladium, which greatly increases the electrical conductivity of the nanowires and allows them to catalyze reactions that take place during charging and discharging. Other groups have tried to produce such batteries using pure or highly concentrated metals as the electrodes, but this new process drastically lowers how much of the expensive material is needed.
Altogether, these modifications have the potential to produce a battery that could provide two to three times greater energy density — the amount of energy that can be stored for a given weight — than today’s best lithium-ion batteries, a closely related technology that is today’s top contender.
Professor Angela Belcher, the WM Keck Professor of Energy and an affiliate of MIT’s Koch Institute for Integrative Cancer Research, explains that this method of biosynthesis is “really similar to how an abalone grows its shell,” as if anyone know how that would be. MIT’s press office explains that it does so “by collecting calcium from seawater and depositing it into a solid, linked structure.”
The researchers note that this line of research is still in its early stages, and more work needs to be done before a commercially viable lithium-air battery can be created — but it certainly looks promising so far… as long as there are no notable concerns about the creation of genetically modified viruses. However, there could be ways around that. “Belcher says that once the best materials for such batteries are found and tested, actual manufacturing might be done in a different way. This has happened with past materials developed in her lab, she says: The chemistry was initially developed using biological methods, but then alternative means that were more easily scalable for industrial-scale production were substituted in the actual manufacturing.”