http://technology.newscientist.com/article/dn14401-fuel-battery-could-take-cars-beyond...
'Fuel battery' could take cars beyond petrol
13:11 25 July 2008
NewScientist.com news service
Colin Barras
A new approach to storing electrical energy can store more energy than
gasoline in the same volume, and could help extend the range of electric
vehicles. But some experts say other approaches are more practical.

The biggest technological hurdle facing electric vehicles is their range.
Even the best rechargeable batteries cannot match the density of energy
stored in a fuel tank.

Combining electric power with a combustion engine to make a hybrid electric
vehicle sidesteps that problem. But a new take on electrical power storage
that is part battery, part chemical fuel cell could ditch gasoline for good.

The new design stores energy more densely than petrol, and was conceived by
Stuart Licht of the University of Massachusetts, Boston, and colleagues.

Gasoline beater
Batteries produce electricity from a closed chemical system that is
eventually exhausted. Fuel cells use a constant supply of fuel, so they are
continually topped up. Licht's cell has features of each.

Its negative electrode, or anode, is made from vanadium boride, which serves
double-duty as a fuel too. But unlike the flowing fuel of a fuel cell, the
material is held internally, like the anode material of a battery.

The vanadium boride reacts with a constant stream of oxygen, as in a fuel
cell, provided by the positive electrode, or cathode. This brings in a
supply of air from outside.

The cell has a theoretical energy capacity of 27 kilowatt hours per litre,
compared to 9.7 kilowatt hours per litre for gasoline. But both approaches
are limited by practical factors to smaller figures.

Licht says his new system would likely have a practical energy capacity of
around 5 kilowatt hours per litre. "But that's two-fold higher than the
practical storage capacity of gasoline," he says.

Electrode refill
He imagines drivers swapping exhausted vanadium boride electrodes for fresh
ones at filling stations. The old electrode can be chemically regenerated
for reuse. Consumers are more familiar with a mechanical process like that
than with recharging a battery, Licht thinks.

Eric Stuve, a fuel cell specialist at the University of Washington, says
Licht's way of thinking makes sense, "especially the estimates of practical
efficiencies".

Chao-Yang Wang, a specialist in fuel cells and advanced battery technology
at Pennsylvania State University, says the design is interesting, but adds
that vanadium boride may take more energy to create than gasoline.

John Owen, an electrochemist at the University of Southampton, UK, thinks
the results are less impressive than they seem.

He says that other designs could yield even higher energy densities than the
vanadium boride system. A lithium-air cell should give twice the energy
density of a vanadium boride-air cell. "Aluminium-air also gets close, and
that is a well-established and large-scale technology," says Owen.
"Moreover, aluminium recovery is already done on a very large scale."

Journal reference: Chemical Communications (DOI: 10.1039/b807929c)

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Weblinks
Stuart Licht, University of Massachusetts
http://alpha.chem.umb.edu/faculty/licht/
Chao-Yang Wang, Pennsylvania State University
http://mtrl1.me.psu.edu/Mtrl/CYWang.html
Eric Stuve, University of Washington
http://faculty.washington.edu/stuve/
John Owen, University of Southampton
http://www.soton.ac.uk/chemistry/research/owen/owen.html