New micro-supercapacitor structure inspired by the
intricate design of leaves
- A team of scientists in Korea has devised a new method for
making a graphene film for supercapacitors
June 29, 2015
There was a time during the early
development of portable electronics when the biggest hurdle to overcome was making
the device small enough to be considered portable. After the invention of the microprocessor in
the early 1970s, miniature, portable electronics have become commonplace and ever
since the next challenge has been finding an equally small and reliable power
source. Chemical batteries store a lot
of energy but require a long period of time for that energy to charge and
discharge plus have a limited lifespan.
Capacitors charge quickly but cannot store enough charge to work for long
enough to be practical. One possible
solution is something called a solid-state micro-supercapacitor (MSC). Supercapacitors are armed with the power of a
battery and can also sustain that power for a prolonged period time. Researchers have attempted to create MSCs in
the past using various hybrids of metals and polymers but none were suitable
for practical use. In more recent trials
using graphene and carbon nanotubes to make MSCs, the results were similarly
lackluster.
An
international team of researchers led by Young Hee Lee, including scientists
from the Center for Integrated Nanostructure Physics at the Institute for Basic
Science (IBS) and Department of Energy Science at Sungkyunkwan University in
South Korea, has devised a new technique for creating an MSC that doesn’t have
the shortcomings of previous attempts but instead delivers high electrochemical
performance.
When
designing something new and complex, sometimes the best inspiration is one
already found in nature. The team
modeled their MSC film structure on natural vein-textured leaves in order to
take advantage of the natural transport pathways which enable efficient ion
diffusion parallel to the graphene planes found within them.
To
create this final, efficient shape, the team layered a graphene-hybrid film
with copper hydroxide nanowires. After
many alternating layers they achieved the desired thickness, and added an acid
solution to dissolve the nanowires so that a thin film with nano-impressions
was all that remained.
To
fabricate the MSCs the film was applied to a plastic layer with thin, ~5μm
long parallel gold strips placed on top.
Everything not covered by the gold strips was chemically etched away so
that only the gold strips on top of a layer of film were left. Gold contact pads perpendicular to the gold
strips were added and a conductive gel filled in the remaining spaces and was
allowed to solidify. Once peeled from
the plastic layer, the finished MSCs resemble clear tape with gold electrical
leads on opposite sides.
The team produced stunning test results. In addition to its
superior energy density, the film is highly flexible and actually increases
capacitance after initial use. The volumetric energy density was
10 times higher than currently available commercial supercapacitors and also
far superior to any other recent research. The MSCs are displaying electrical properties
about five orders of magnitude higher
than similar lithium batteries and are comparable to existing, larger
supercapacitors. According to Lee, “To our knowledge, the volumetric energy density
and the maximum volumetric power density in our work are the highest values
among all carbon-based solid-state MSCs reported to date.”
In
the future, consumers will likely power their devices with MSCs instead of
batteries. Applications for light,
reliable energy storage combined with a long lifespan and fast charge/discharge
time. The team’s MSCs could be embedded
into an electronic circuit chip as power sources for practical applications
such as implantable medical devices, active radio frequency identification
tags, and micro robots. If engineers
utilize the material’s incredible flexibility, these MSCs could be utilized in
portable, stretchable, and even wearable electronic devices.
By Daniel
Kopperud
Notes for editors
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References
Jian Chang , Subash
Adhikari , Tae Hoon Lee , Bing Li , Fei Yao , Duy Tho Pham ,
Viet Thong Le, and Young
Hee Lee, (2015), “Leaf Vein-Inspired Nanochanneled Graphene Film for Highly
Efficient Micro-Supercapacitors”, Advanced Energy Materials, DOI:
10.1002/aenm.201500003
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Media
Contact
For further information or to request media
assistance, please contact: Mr. Shi Bo Shim, Head of Department of
Communications, Institute for Basic Science (+82-42-878-8189; sibo@ibs.re.kr)
or Ms. Sunny Kim, Department of Communications, Institute for Basic Science
(+82-42-878-8135; Sunnykim@ibs.re.kr)
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About
the Institute for Basic Science (IBS)
IBS was founded in 2011 by the government of the Republic of Korea with the
sole purpose of driving forward the development of basic science in Korea It
comprises a total of 50 research centers in all fields of basic science,
including mathematics, physics, chemistry, life science, earth science and
interdisciplinary science. IBS
has launched 24 research centers as of January 2015.There are eight physics,
one mathematics, six chemistry, seven life science, and two interdisciplinary
research centers.
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