Scientists have created a powerful micro-supercapacitor, just nanometres thick,
that could help electronics companies develop mobile phones and cameras that are
smaller, lighter and thinner than ever before. The tiny power supply measures
less than half a centimetre across and is made from a flexible material, opening
up the possibility for wearable electronics.
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The research is published in the Royal Society of
Chemistry journal Energy & Environmental Science.
A bottleneck in making
portable electronic devices like mobile phones even smaller is reducing the size
and increasing the flexibility of the power supplies in electronic circuits.
Supercapacitors are attractive power supplies because they can store almost as
much energy as a battery, with the advantage of high-speed energy discharge.
Supercapacitor electrodes are normally made from carbon or conducting polymers,
but these can be relatively costly.
A team led by Professor Oliver G Schmidt
at the Leibniz Institute for Solid State and Materials Research in Dresden
(IFW-Dresden) examined the use of manganese dioxide as an alternative electrode
material, which is more environmentally friendly and less expensive than the
standard materials. Manganese dioxide is not a natural choice for an electrode
material because it isn't very electrically conductive, nor is it naturally
flexible or strong. However, the scientists overcame this by vaporising the
manganese dioxide using an electron beam and then allowing the gaseous atoms to
precipitate into thin, bendy films. They incorporated very thin layers of gold
into the films to improve the electrical conductivity of the material.
Tests
on the new micro-supercapacitor showed that the tiny, bendy power supply can
store more energy and provide more power per unit volume than state-of-the-art
supercapacitors.
Dr Chenglin Yan, leader of the research group at
IFW-Dresden, said: "Supercapacitors, as a new class of energy device, can store
high energy and provide high power, bridging the gap between rechargeable
batteries and conventional capacitors. So we thought a micro-supercapacitor
would be an important development in the rapid advance of portable consumer
electronics, which need small lightweight, flexible micro-scale power
sources.
"The device could be applied to many miniaturised technologies,
including implantable medical devices and active radio frequency identification
(RFID) tags for self-powered miniaturised devices. "
The next step in the
team's research is finding a cheaper alternative to gold to improve the
conductivity of the micro-supercapacitor.
Dr Yan said: "The major challenge
we had to overcome in developing this technology was to obtain really high
energy density on the micro-scale, at a low cost. The inclusion of gold in our
micro-supercapacitor makes it more expensive, so we are now looking at replacing
gold with cheaper metals, such as manganese, to make the device more practical
for the market. "
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