MIT researchers have found a way to boost lithium-air battery performance, with the help of modified viruses.
MIT researchers have found that adding genetically modified viruses to the production of nanowires -- wires that are about the width of a red blood cell, and which can serve as one of a battery's electrodes -- could help solve some of these problems.
The new work is described in a paper published in the journal Nature Communications, co-authored by graduate student Dahyun Oh, professors Angela Belcher and Yang Shao-Horn, and three others. The key to their 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.
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.
Belcher, the W.M. Keck Professor of Energy and an affiliate of MIT's Koch Institute for Integrative Cancer Research, explains that this process of biosynthesis is "really similar to how an abalone grows its shell" -- in that case, by collecting calcium from seawater and depositing it into a solid, linked structure.
The increase in surface area produced by this method can provide "a big advantage," Belcher says, in lithium-air batteries' rate of charging and discharging. But the process also has other potential advantages, she says: Unlike conventional fabrication methods, which involve energy-intensive high temperatures and hazardous chemicals, this process can be carried out at room temperature using a water-based process.
Also, rather than isolated wires, the viruses naturally produce a three-dimensional structure of cross-linked wires, which provides greater stability for an electrode.
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