BBC News, Leo
Kelion, Technology reporter, 17 April 2013
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| Researchers claim their technology could shrink the size of batteries by 10 times while offering the same power |
The
University of Illinois team says its use of 3D-electrodes allows it to build
"microbatteries" that are many times smaller than commercially
available options, or the same size and many times more powerful.
It adds
they can be recharged 1,000 times faster than competing tech.
However,
safety issues still remain.
Details of
the research are published in the journal Nature Communications.
Battery
breakthrough
The
researchers said their innovation should help address the issue that while
smartphones and other gadgets have benefited from miniaturised electronics,
battery advances have failed to pace.
Batteries
work by having two components - called electrodes - where chemical reactions
occur.
In simple
terms, the anode is the electrode which releases electrons as a result of a
chemical reaction.
The cathode
is the electrode on the other side of the battery to which the electrons want
to flow and be absorbed - but a third element, the electrolyte, blocks them from
travelling directly.
When the
battery is plugged into a device the electrons can flow through its circuits
making the journey from one electrode to the other.
The
scientists' "breakthrough" involved finding a new way to integrate
the anode and cathode at the microscale.
"The
battery electrodes have small intertwined fingers that reach into each
other," project leader Prof William King told the BBC.
"That
does a couple of things. It allows us to make the battery have a very high
surface area even though the overall battery volume is extremely small.
 |
| A cross-section of the battery reveals the 3D-design of the research project's anodes and cathodes |
"Because
we're reduced the flowing distance of the ions and electrons we can get the
energy out much faster."
Repeatable
technique
The battery
cells were fabricated by adapting a process developed by another team at the
university which is designed to make it faster to recharge the batteries than
lithium ion (Li-on) and nickel metal hydride (NiMH) equivalents.
It involves
creating a lattice made out of tiny polystyrene spheres and then filling the
space in and around the structure with metal.
The spheres
are then dissolved to leave a 3D-metal scaffold onto which a nickel-tin alloy
is added to form the anode, and a mineral called manganese oxyhydroxide to form
the cathode.
Finally the
glass surface onto which the apparatus was attached was immersed into a
chemical liquid heated to 300C (572F).
"Today
we're making small numbers of these things in a boutique fabrication process,
but while that's reliable and we can repeat it we need to be able to make large
numbers of these things over large areas," said Prof King.
"But
in principle our technology is scaleable all the way up to electronics and
vehicles.
"You
could replace your car battery with one of our batteries and it would be 10
times smaller, or 10 times more powerful. With that in mind you could jumpstart
a car with the battery in your cell phone."
Safety fear
Other
battery experts welcomed the teams efforts but said it could prove hard to
bring the technology to market.
"The
challenge is to make a microbattery array that is robust enough and that does
not have a single short circuit in the whole array via a process that can be
scaled up cheaply," said Prof Clare Grey from the University of
Cambridge's chemistry department.
University
of Oxford's Prof Peter Edwards - an expert in inorganic chemistry and energy -
also expressed doubts.
"This
is a very exciting development which demonstrates that high power densities are
achievable by such innovations," he said.
"The
challenges are: scaling this up to manufacturing levels; developing a simpler
fabrication route; and addressing safety issues.
"I'd
want to know if these microbatteries would be more prone to the self-combustion
issues that plagued lithium-cobalt oxide batteries which we've seen become an
issue of concern with Boeing's Dreamliner jets."
 |
| Prof William King hopes to use the microbattery to power electronic equipment before the end of the year |
He said
that in the test equipment only a microscopic amount of the liquid was used,
making the risk of an explosion negligible - but if it were scaled up to large
sizes the danger could become "significant".
However, he
added that he soon planned to switch to a safer polymer-based electrolyte to
address the issue.
Prof King
added that he hoped to have the technology ready to be trialled as a power
source for electronic equipment before the end of the year.
The
University of Illinois at Urbana-Champaign team is one of several groups
attempting to overhaul the way we power gadgets.
Researchers
in Texas are working on a kind of battery that can be spray-painted onto any
surface while engineers at the University of Bedfordshire are exploring the
idea of using radio waves as an energy source.
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