MARQUEZ, Kristina Patriz S.
2013-48674
STS-THY
Individual Project for STS
Transparent
Batteries: Step closer into Sci-fi no more
In
the year 2011, several researchers at the Stanford University lent their hands
to create transparent lithium-ion batteries, which can be seen in the picture
above. This research was led by Yi Cui. The researchers made a grid-structured
electrode, which is fabricated by a microfluidics-assisted method.
But,
what are these transparent batteries for? At first, I was really wondering why
someone would waste so much effort just to create transparent batteries. But
then of course, I realized how people starve so much for transparent devices,
for the devices introduced to us by sci-fi movies.
What
good is a see through screen if the electronics behind it are as opaque as
ever? Several companies have already created partially transparent gadgets;
however, fully transparent devices seem to have remained in our imaginations
due to one missing piece.
"If
you want to make everything transparent, what about the battery?", Yi Cui
asked. Transparent batteries, a key component in fully integrated transparent
devices, have not yet been reported. Developing a transparent power source was
the last obstacle, the last puzzle piece, to creating fully transparent digital
gadgets.
Yuan
Yang and Cui came up with a research idea on how to make transparent batteries.
“Since key active materials in batteries cannot yet be made transparent or
replaced with transparent alternatives, Yang and Cui realized that they had to
find a way to construct a battery such that its nontransparent components were
too small to be seen by the naked eye.”(Liou, 2011)
The
human eye’s maximum resolving power is between 50 to 100 microns. This means
that things smaller than 50 microns would appear transparent in front of the
naked eye. With this in mind, Yang and Cui devised a mesh-like framework for
the battery electrodes, with each "line" in the grid being
approximately 35 microns wide.
Instead
of using copper or aluminum, polydimethylsiloxane (PDMS) was used as a
transparent alternative. PDMS is actually pretty cheap but is not conductive so
metals had to be deposited onto it. To do so, PDMS was poured into silicon
molds to create grid-patterned trenches. A metal film was evaporated over the
trenches, creating a conductive layer. A liquid slurry solution containing
minuscule, nano-sized active electrode materials were then dropped into the
trenches.
Next,
a special transparent substance was developed to be sandwiched between
electrodes. Yang modified an existing gel electrolyte to make it serve
double-duty as both an electrolyte and a separator. By precisely placing an
electrolyte layer between two electrodes, one functional battery is created.
Multiple layers can be added in order to create a larger and more powerful
battery.
As
long as the gridlines are matched accurately, transparency is maintained. Yang
and Cui's light transmittance tests showed a 62 percent transparency in visible
light, and approximately 60 percent
transparency even with three full cells stacked on top of each other.
The
transparent battery is less expensive than one might expect. Cui even said that
"Its cost could be similar to those of regular batteries.” The resulting
power packs are cheap and flexible but, currently, can only store about half as
much energy as a traditional lithium-ion battery. Although Cui says that they
could still increase the amount of energy the battery can store without
sacrificing its transparency by simply lining up a few transparent cells in the
same way that most batteries use a series of cells to produce more power.
References:
[1]
Anthony, S. (2011). Transparent
lithium-ion batteries make sci-fi gadgets a reality. Retrieved from http://www.extremetech.com/computing/90964-transparent-lithium-ion-batteries-make-sci-fi-gadgets-a-reality.
March 1, 2014.
[2] Cui,
Y., Hu, L., Jeong, S., Lee, S. W., Woo, H., & Yang, Y. (2011). Transparent lithium-ion batteries. doi: 10.1073/pnas.1102873108 or http://www.pnas.org/content/early/2011/07/18/1102873108?tab=author-info.
March 1, 2014.
[3]
DiSalvo, D. (2011). 10 Big science and technology advances to watch. Retrieved
from http://www.forbes.com/sites/daviddisalvo/2011/07/29/10-big-science-and-technology-advances-to-watch/. March 1,
2014.
[4]
Liou, S. (2011). Stanford transparent batteries: seeing straight through to the
future?. Retrieved from. http://news.stanford.edu/news/2011/july/transparent-litiumion-battery-072511.html.
March 1, 2014.
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