The key to research study was finding a way to modify the nanowires - wires that are about the width of a red blood cell, and can serve as one of a battery’s electrodes - to increase the area where electrochemical activity takes place during charging or discharging of the battery.
The researchers produced an array of nanowires, each about 80 nm 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 were used to create a lithium-air battery’s cathode were made by the viruses. Unlike wires 'grown' via conventional chemical methods, the virus-built nanowires have a rough, spiky surface that increases their surface area.
Angela Belcher, the W.M. Keck Professor of Energy and a member of MIT’s Koch Institute for Integrative Cancer Research, explained that the biosynthesis process is “really similar to how an abalone grows its shell”.
The increase in surface area produced by this method can boost the lithium-air batteries’ rate of charging and discharging. But the process also has other potential advantages. "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," explained Belcher.
Also, rather than isolated wires, the viruses naturally produce a three-dimensional structure of cross-linked wires, which provides 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.
The modifications have the potential to produce a battery that could provide two to three