Home' ALGY : ALGY Edition 23 2016 Contents THE AUSTRALIAN LOCAL GOVERNMENT YEARBOOK EDITION 23 • 159
A team of Queensland University of Technology (QUT)
researchers recently developed a lightweight, all-carbon
supercapacitor by sandwiching a gelled electrolyte between two
thin electrodes made of stacked graphene (single graphite layers),
which resulted in a thin and extremely strong film with high
power density . Today, commercial supercapacitors are based on
activated carbon, which is a porous material, and mixed with a
polymer binder to make electrode film. The capacitance of such
material is normally in the scale of tens of Farads per gram (F/g),
and there is not much room to improve further.
The QUT group used graphene and carbon nanotubes
-- two novel carbon nanomaterials -- to make thin films as
supercapacitor electrodes. Contrary to activated-carbon-based
supercapacitors that are bulky and contain liquid electrolyte,
devices made by the QUT group are solid-state, as they use a
polymer electrolyte similar to glue, and are made as thin films.
This kind of supercapacitor is very light, and can be combined
with regular batteries to dramatically boost the power of an
electric car. The key characteristics of supercapacitors are the
ability to charge-discharge within seconds; a long lifetime of
more than 106 cycles; being environmentally friendly; and the
ability to provide stable operation at different temperatures.
Today, several companies such as Maxwell, FastCap Systems,
NEC, Panasonic, Tokin, and even car companies such as Volvo
are investing further in developing this technology because
of the possibility of having a large amount of energy in a small
component that can be easily integrated into a device. Volvo, for
example, is working on reducing the weight and increasing the
space in a hybrid vehicle by incorporating supercapacitors into
the frame of the car.
The film-shaped supercapacitors developed by QUT
researchers could be embedded in a car's body panels, roof,
doors, bonnet and floor -- storing enough energy (after being
plugged into electricity mains) to turbocharge an electric car's
battery in just a few minutes. Currently, the 'energy density' of
a supercapacitor is lower than a standard lithium-ion (Li-ion)
battery, but its 'high power density', or ability to release power
in a short time, is 'far beyond' a conventional battery. In the
future, it is hoped that the supercapacitor will be developed
to store more energy than an Li-ion battery while retaining the
ability to release its energy up to 10 times faster -- meaning
that the car could be entirely powered by the supercapacitors
in its body panels.
The range of electric cars nowadays is very close to 300
kilometres before the battery needs to be recharged. It is likely
that in the near future (five to 10 years' time), this limit could be
overcome by integrating conventional powerful Li-ion or Li-
metal batteries and supercapacitors embedded in the car body.
While Li batteries need hours to be fully recharged (although
recent advances show that it would be possible to turbo-
recharge Li batteries in less than one hour), supercapacitors can
be recharged in minutes, providing the perfect solution for the
mobility of electric cars.
Local government agencies could potentially save a large
amount of money by introducing electric cars and buses in
their fleets, as soon as the combination of powerful batteries
and supercapacitors becomes available at a reasonable price.
Together with electric companies, local governments would
help to build the infrastructure to recharge electric cars and
buses, boosting the economy and saving a large amount of
1 Lu, M., F. Beguin, and E. Frackowiak, Supercapacitors 2013: Wiley-VCH.
2 T.C. Murphy, R.B.W., R.A. Sutula, in: F.M. Delnick, D. Ingersoll, X. Andrieu, K.
Naoi. Electrochemical Capacitors II. in The Electrochemical Society. 1997.
3 Liu, J., F. Mirri, M. Notarianni, M. Pasquali, and N. Motta, High performance
all-carbon thin film supercapacitors. Journal of Power Sources, 2015. 274(0):
Figure 1: Charge and Discharge of an EDLC (from ).
Figure 2. An all-carbon supercapacitor developed at QUT . The
microscopic image shows the structure of the material made by
graphene and carbon nanotubes.
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