Defense Intelligence Reference Document Ultracapacitors As Energy And Power Storage Devices

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Chapter 5: Future Developments
There have been significant advancements in ultracapacitor technology in the last few
years. Increased understanding of the physical mechanism behind this technology,
combined with advancements in materials science, particularly on the nanoscale, has
led to a rapid increase in capability. Improvements to ultracaps in the next 10 years
(2010-20) will focus on electrodes, better electrolytes, packaging, and alternative
designs. Electrode improvements will most likely include migration away from activated
carbon, for both electrodes. Asymmetric electrodes will eliminate carbon on one side,
and new carbon materials will provide better performance at a competitive price.
Electrolytes will likely move toward additional organic materials and ultracaps with high
temperature performance requirements likely will use ionic liquids.
In the near term, a transition to the asymmetric design is expected. Continued
improvements to the electrodes and cell design will provide better capacitance. Many of
the short-term improvements will likely be directed toward manufacturing capacity.
Ultracapacitors are becoming more common, and as improvements to performance and
cost make them more accessible to multiple applications, this trend will continue. Over
the next few years, it is expected that the market for ultracaps will increase
dramatically. Trends in materials for ultracaps will continue forward with improvements
and utilization of activated carbons, thinner current collectors, and improved cell design
and packaging. Research being done at universities and national labs will continue, but
these will not become common materials for ultracapacitors in the next few years.
However, as the demand for ultracapacitors increases, specialty materials will begin to
see utility for some applications, driving down manufacturing costs, which in turn will
enable their use in more systems. Significant use will be made in integrating into power
converters to reduce size, mass, and cost. Both thin-film and MCap devices will become
prevalent. If MCaps achieve lithium ion specific energy their adoption will be rapid and
revolutionary as has occurred with LiFeP04 (lithium-iron-phosphate) batteries for both
transportation and extremely high pulsed-power systems such as lasers.
Within the next 10 years, ultracaps will begin to see the incorporation of advanced
carbon materials and electrodes designed with features on the nanometer scale. Carbon
nanotubes, graphene, and porous carbons all have extremely high potential to unseat
activated carbon as the electrode of choice. The replacement of carbon systems being
used today (including activated carbon, aerogels, and carbon cloths) will occur as cost
reductions take place in the manufacturing of nanostructured carbonaceous materials.
The tradeoff between surface area and pore size can be exploited at the nanoscale.
Optimization of these parameters will likely yield fairly significant improvements to the
capacitance and result in higher power and better energy density.
The mid-range (2020-30) development of ultracapacitors will most likely be the full
incorporation of advanced carbons and hybrid systems. It is hard to anticipate which
technology has the most to offer, as there are unique benefits and hurdles for each.
Hybrid systems will be common, utilizing a battery-like electrode combined with one of
the advanced carbon electrodes. The pseudocapacitive electrode options will become
diversified, with manufacturers using unique materials to differentiate their product. An
alternative electrode to the ruthenium oxide (Ru02) used today will be used for both
performance and economical reasons. Supply issues will drive electrode materials
toward those with larger availability.
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