Dear EarthTalk

What is the potential for carbon “nanotubes” in battery technology? I heard them referred to as the biggest battery breakthrough to come along in years. And what else can we expect to see in terms of new battery technology in coming years?

R.M. Koncan

via e-mail

The rechargeable lithium-ion batteries now so common in everything from iPods to hybrid cars can store twice the energy of similarly sized nickel-metal hydride batteries and up to six times as much as their lead-acid progenitors. But these advances are only a small evolutionary step from the world’s first battery designed by Alessandro Volta in 1800 using layers of metal and blotting paper soaked in salt water.

With battery technology advances long overdue, researchers are racing to develop more efficient ways to store power. One hopeful option is in the use of carbon nanotubes, which can store much more electricity by weight than lithium-ion batteries while keeping their charge and remain durable for far longer.

But what are carbon nanotubes, and how can they be used to store energy? Technicians skilled in working with matter at the molecular (nano) level can arrange pure carbon molecules in cylindrical structures that are not both strong and flexible. They have significantly higher energy density and can store more electricity than any currently available technology. These tubes, each only billionths of a meter wide, essentially become highly efficient, electrically conductive pipes for storing and providing power.

Electrical engineers at the Massachusetts Institute of Technology (MIT) have formed carbon molecules into tiny springs that store as much electricity as same sized lithium-ion batteries but can maintain a charge while dormant for years and work well in temperature extremes. Stanford University researchers have created ink made from carbon nanotubes that can be drawn onto paper where it serves as a high-capacity rechargeable energy storage medium. And University of Maryland scientists have created nanostructures able to store and transport power at 10 times the energy density of lithium-ion batteries.

Other technologies in development include batteries using zinc-air, lithium-air and other combinations of elements to provide longer run-times between recharges. Others still are working on prototype nuclear batteries, the trick being to make them small enough to be practical, let alone safe.

Of course, the accelerating growth of nanotechnology itself, which has not yet been thoroughly tested to evaluate potential down sides, has some health advocates worried. Animal studies have shown that some nanoparticles, if inhaled or ingested, can harm the lungs and also cross the blood-brain barrier, which protects the brain from toxins in the bloodstream.

And then there are fuel cells, created in 1839 but only recently commercialized. Not batteries per se, fuel cells generate, store and dispense power by forcing a reaction between a fuel (hydrogen from water, methanol) and oxygen, creating usable non-polluting electricity. One major hurdle for fuel cell makers is making them small enough to be able to work in laptops and other small personal electronics.

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