Of
all the criticisms of electric vehicles, probably the most
commonly-heard is that their batteries take too long to recharge – after
all, limited range wouldn’t be such a big deal if the cars could be
juiced up while out and about, in just a few minutes. Well, while no one
is promising anything, new batteries developed at the University of
Illinois, Urbana-Champaign do indeed look like they might be a step very
much in the right direction. They are said to offer all the advantages
of capacitors and batteries, in one unit.
"This
system that we have gives you capacitor-like power with battery-like
energy," said U Illinois’ Paul Braun, a professor of materials
science and engineering. "Most capacitors store very little energy. They
can release it very fast, but they can’t hold much. Most batteries
store a reasonably large amount of energy, but they can’t provide or
receive energy rapidly. This does both."
The speed at which conventional batteries are able to
charge or discharge can be dramatically increased by changing the form
of their active material into a thin film, but such films have typically
lacked the volume to be able to store a significant amount of energy.
In the case of Braun’s batteries, however, that thin film has been
formed into a three-dimensional structure, thus increasing its storage
capacity.
Batteries
equipped with the 3D film have been demonstrated to work normally in
electrical devices, while being able to charge and discharge 10 to 100
times faster than their conventional counterparts.
To
make the three-dimensional thin film, the researchers coated a surface
with nano scale spheres, which self-assembled into a lattice-like
arrangement. The spaces between and around the spheres were then coated
with metal, after which the spheres were melted or dissolved away,
leaving the metal as a framework of empty pores. Electro polishing was
then used to enlarge the pores and open up the framework, after which it
was coated with a layer of the active material – both lithium-ion and
nickel metal hydride batteries were created.
The
system utilizes processes already used on a large scale, so it would
reportedly be easy to scale up. It could also be used with any type of
battery, not just Li-ion and NiMH.
The
implications for electric vehicles are particularly exciting. "If you
had the ability to charge rapidly, instead of taking hours to charge the
vehicle you could potentially have vehicles that would charge in
similar times as needed to refuel a car with gasoline," Braun said. "If
you had five-minute charge capability, you would think of this the same
way you do an internal combustion engine. You would just pull up to a
charging station and fill up."
Braun and his team
believe that the technology could be used not only for making electric
cars more viable, but also for allowing phones or laptops to be able to
recharge in seconds or minutes. It could also result in high-power
lasers or defibrillators that don’t need to warm up before or between
pulses.
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