Harnessing viruses to build a better battery
The first virus to be discovered was the Tobacco mosaic virus (TMV) back in 1898. It is a rigid, rod-shaped virus that, under an electron microscope, looks like uncooked spaghetti. This widespread virus devastates tobacco, tomatoes, peppers and other plants but in the lab, engineers at the University of Maryland's A. James Clark School of Engineering and College of Agriculture and Natural Resources, have managed to harness and exploit the self-replicating and self-renewing characteristics of TMV to build tiny components for more efficient lithium-ion batteries.
To create the highly efficient batteries the researchers first modified the TMV rods to bind perpendicularly to the metallic surface of a battery electrode and arrange the rods in intricate and orderly patterns on the electrode. Because TMV can be programmed to bind directly to metal, the resulting components are lighter, stronger and less expensive than conventional parts. They then coated the rods with a conductive thin film that acts as a current collector and finally the battery's active material that participates in the electrochemical reactions.
10-fold increase in energy capacity
This results in an electrode with a greatly increased surface area that increases its capacity to store energy and enables fast charge/discharge times. The new batteries boast up to a 10-fold increase in energy capacity over a standard lithium-ion battery. The researchers say that the use of the TMV virus in fabricating batteries can be scaled up to meet industrial application needs. And because the TMV becomes inert during the manufacturing process, the batteries do not spread the virus. "The resulting batteries are a leap forward in many ways and will be ideal for use not only in small electronic devices but in novel applications that have been limited so far by the size of the required battery," said Ghodssi, director of the Institute for Systems Research and Herbert Rabin Professor of Electrical and Computer Engineering at the Clark School.
"The technology that we have developed can be used to produce energy storage devices for integrated microsystems such as wireless sensors networks. These systems have to be really small in size - millimeter or sub-millimeter - so that they can be deployed in large numbers in remote environments for applications like homeland security, agriculture, environmental monitoring and more; to power these devices, equally small batteries are required, without compromising in performance," added Ghodssi.
Virus suited for other jobs
While the focus of the University of Maryland researchers has been on energy storage, they say that the structural versatility of the TMV template used to create the highly efficient lithium-ion batteries means it could also be used in a variety of other applications. "One of our lab's ongoing projects is aiming at the development of explosive detection sensors using versions of the TMV that bind TNT selectively, increasing the sensitivity of the sensor. In parallel, we are collaborating with our colleagues at Drexel and MIT to construct surfaces that resemble the structure of plant leaves. These biomimetic structures can be used for basic scientific studies as well as the development of novel water-repellent surfaces and micro/nano scale heat pipes," said Ghodssi.