Using viruses to grow nanowires boosts performance of energy-dense batteries

A team of US researchers has found a way to improve the performance of lithium-air batteries – they used modified viruses to grow unusual nanowires that increase the electrochemical activity in the electrodes when the energy-dense batteries are charging or discharging.

Battery innovation and improvement is becoming an increasingly hot research area, as demand for cleaner ways to produce and store energy increases.

Lithium-air batteries are a promising new type of battery because they have the potential to store a lot of energy for a small amount of weight, making them attractive for use in electric cars, for example.

The bigger the ratio of power to weight, the greater the driving range per charge.

Lithium-air batteries not yet commercially viable

But there are many challenges still to overcome before lithium-air batteries are anywhere near commercially viable.

One challenge is how to make more durable materials for the electrodes; another is improving the number of charging and discharging cycles the battery can sustain.

Now nanotechnology, where materials are manipulated on an atomic scale to produce unique properties, and virology, that uses modified viruses to manipulate the materials, have come together to provide a possible solution to one of these challenges.

Writing in a recent issue of the journal Nature Communication, MIT graduate student Dahyun Oh, and colleagues, describe how adding viruses to the production of nanowires can result in nanowires with novel structural properties.

They genetically modified a virus called M13, and showed it could capture metal molecules from water and bind them into structural shapes – producing arrays of nanowires, each measuring about 80 nanometers across.

And unlike nanowires produced by conventional chemical means, the surfaces – in this case of manganese oxide nanowires – were rough and spiky as opposed to smooth. Rough and spiky surfaces have much greater surface areas, thus vastly increasing the amount of electrochemical activity that goes on where metal wire meets chemical solution during battery charging and discharging.

The researchers liken the biosynthesis of the nanowires to the way the abalone grows its shell, except in the case of the sea snail, it extracts calcium from seawater and deposits it into a solid, linked structure.

The researchers say the nanowires grown by the virus method also offer other advantages that make lithium-air batteries even more attractive for commercial use.

However, they say there are still a lot more scientific challenges to overcome before such a battery is ready for the road.