Developments in supercapacitor fabrication drive forward the state-of-the-art

By Gary Elinoff, contributing writer

Supercapacitors
have it all over batteries in terms of how quickly they can be charged. They
needn’t contain the oh-so-volatile element lithium or troublesome liquid
electrolytes, so the dangers of explosion and fire are drastically reduced. The
problem is energy density; pound for pound, present-day supercapacitors can
only hold about 10% of the watt-hours that modern lithium-ion batteries (LIB)
can.

At the University
of Waterloo
, Professor Michael Pope and his colleagues are working on a
way to drastically improve storage capacity. The plates of the capacitor
they’ve developed are constructed of graphene and are coated with a special
oily liquid salt. Then detergent and water are used to reduce the size of the
droplets of liquid salt to a few nanometers. The detergent also serves the
purpose of causing the droplets to stick tightly to the graphene.

The
nanometer scale of the droplets, microscopically separating layers of plates,
makes it possible to deploy a huge number of plates in a given area. And better
yet, the droplets themselves serve as the capacitor’s electrolyte, so no
separate element needs to be added, which would increase the separation between
the plates, thereby avoiding the negative result of lowering the overall
capacitance of the device. A description of the work conducted by Professor
Pope and his team was released in a press release from the University of
Waterloo, and a paper published in the journal ACS
Nano
describes the work in detail.

Fabricating_Supercapacitor

Fabricating a supercapacitor. Image
source: ACS
Nano
.

Early uses
envisioned for high-density supercapacitors include applications in which really
fast charging and discharging are decisive. These include supplying power for
high-power lasers and rail-guns, as well as serving as power sources for
wearable and mobile devices.

Supercapacitors
will also be extremely useful in electrical vehicle braking, which works by
converting kinetic energy into electrical energy, thereby slowing or stopping
the vehicle. This generates a huge electrical power surge, much of which is now
uselessly and wastefully dissipated. Supercapacitors, which can absorb
electrical charge far faster than batteries can, reabsorb this previously lost
energy, holding it in reserve until it is again deployed to the vehicles motor
to put it back in motion.

Research
into LIBs for EVs has moved out of the lab and is well-ensconced in corporate
research labs such as those of Toyota,
which is working on the issues surrounding the charging speed and fire hazards,
and they have a large head start over supercapacitors in terms of market penetration.
However, these devices can only be manufactured via environmentally dirty
processes, while the building of supercapacitors seems to be going down a
cleaner path.

In the
shorter-term, we may see supercapacitors replace the LIBs in mobile devices such
as smartphones. According to Professor Pope, “If they’re marketed in the correct ways for the right
applications, we’ll start seeing more and more of them in our everyday lives.”