New study could lead to more efficient, environmentally friendly batteries
A computer virus won’t help your laptop work — but a biological virus could. Tweaking their genes just so could engineer viruses for making the rechargeable lithium ion batteries that power devices such as laptops, iPods and cell phones, researchers report online April 2 in Science.
In previous research, the same team used viruses to construct the negative electrode, or anode, of the battery. In the new work, the researchers engineered viruses for the positive electrode, or cathode. When the two are put together, the virus batteries should perform better than traditional lithium ion batteries and also be environmentally friendly, the team reports.
“Because the viruses are living organisms, we had to use only water-based solvents, no high pressures and no high temperatures,” says Angela Belcher, a materials scientist at the Massachusetts Institute of Technology in Cambridge and a study coauthor.
Lithium ion batteries store up and release electrical energy when lithium ions and electrons move between the anode and cathode. The cathode is often made of iron phosphate, a stable material that, when it reacts with lithium, has a high capacity to store energy. But it’s not a very good conductor. The movement of ions and electrons through the cathode is relatively slow, making the battery less efficient at releasing energy.
Ions and electrons can move through smaller particles more quickly. But fabricating nano-sized particles of iron phosphate is a difficult and expensive process, the researchers say.
So Belcher’s team let the virus do the work. By manipulating a gene of the M13 virus to make the viruses coat themselves in iron phosphate, the researchers created very small iron phosphate particles.
“We’re using a biological template that’s already on the nanoscale,” Belcher says.
Tweaking a second gene made one end of the virus bind to carbon nanotubes, which conduct energy well. The resulting network of iron phosphate-coated viruses and carbon nanotubes formed a highly conductive cathode, one that ions and electrons could move through quickly.
“This work is an exciting breakthrough,” comments battery chemist Kang Xu of the U.S. Army Research Laboratory in Adelphi, Md. “Belcher is the first to use viruses as a nano-template to assemble materials.”
Using different cathode materials could make the future batteries even better, Belcher says. “This paper proved that the concept works.”
Lee, Y.J., et al. In press. Fabricating gentically engineered high-power lithium ion batteries using multiple virus genes. Science.