Supercapacitors — also known as ultracapacitors — have been promoted as a potential battery replacement over the past two decades, and they already fill that role in a number of applications, such as smart meters, memory backup, energy recovery, and emergency doors. However, their limited energy density with conventional activated carbons has spurred much research into exotic, high energy density carbons. These advanced higher capacity supercapacitor carbons have failed in the marketplace because of issues with market realities despite their technical feasibility. As the supercapacitor industry matures, it is becoming more and more sensitive to materials cost, much like the battery industry is.

1. 10 Batteries International Summer 2013 www.batteriesinternational.com
OPINION — SUPERCAP CARBON PRICING
Supercapacitors — also known as ultra-
capacitors — have been promoted as a
potential battery replacement over the
past two decades, and they already fill
that role in a number of applications,
such as smart meters, memory backup,
energy recovery, and emergency doors.
However, their limited energy density
with conventional activated carbons has
spurred much research into exotic, high
energy density carbons. These advanced
higher capacity supercapacitor carbons
have failed in the marketplace because
of issues with market realities despite
their technical feasibility. As the super-
capacitor industry matures, it is becom-
ing more and more sensitive to materials
cost, much like the battery industry is.
Advanced carbon materials produced
for supercapacitors such as carbon
aerogels, carbide-derived carbon, and
nanotubes offer superior energy density
(up to double the capacity of conven-
tional activated carbon) at several times
the cost of the coconut shell activated
carbon that powers commercial su-
percapacitors. Meanwhile, graphene’s
long-term pricing and performance are
uncertain since graphene manufactur-
ing is still in its infancy.
End-users tend to be much more sen-
sitive to pricing and reliability than to
power/energy density metrics for the
demonstrated range in performance;
there seems to be little need for expen-
sive higher capacity supercapacitors.
Based on commercial trends in the
industry, there is a substantial oppor-
tunity for producing lower-cost super-
capacitor carbons with similar perfor-
mance to conventional coconut shell
carbons.
The need for low cost carbon
Supercapacitor manufacturers have
sent clear signals regarding the need
for low cost carbon; Maxwell’s VP of
communications and investor relations
was quoted in MIT’s technology review
stating that the supercapacitor indus-
try is highly sensitive to carbon pric-
ing. Nonetheless, technology start-ups
have almost exclusively focused on the
very small high-performance end of the
market.
Almost all commercial supercapaci-
tors currently use activated carbon as
the active material in their electrodes;
supercapacitor-grade coconut shell
carbon has dropped in price to only
$15-$20 per kilogram from over $150-
$200 per kilogram. Activated carbon is
made by charring a carbon-containing
precursor (such as wood, coal, coconut
Low cost carbon —
key to a successful
supercap future
In addition to misunderstanding the requirements
for a successful market entry, the would-be
supercapacitor carbon manufacturers have
overestimated the size of the market for their
material.
How have researchers, funding agencies and investors misread the
market for supercapacitor carbons? Ranjan Dash and Lawrence
Weinstein explain

2. www.batteriesinternational.com Batteries International Summer 2013 11
OPINION — SUPERCAP CARBON PRICING
shells, or resins), then using an oxidiz-
ing agent (such as steam or carbon di-
oxide) to form nanoscopic pores.
To provide some perspective on the
current state of the art, currently avail-
able coconut shell supercapacitor car-
bons provide roughly 25 Farads on a
device level for every gram of carbon
used in conventional organic electro-
lytes.At $15 per kg, one obtains rough-
ly 1600 Farads per dollar. Currently,
large format supercapacitors are sold
for roughly 60 Farads per dollar.
Choices on offer
To date, coconut shell and resin based
carbons have been used in most com-
mercial supercapacitors. While resin-
based carbons have offered slightly
better performance, their cost premium
has been high enough that supercapaci-
tor manufacturers have moved to using
coconut shell activated carbon.
Carbon aerogel has demonstrated
comparable performance to activated
carbons, but is more expensive, reduc-
ing its relevance. Carbide-derived car-
bons (CDCs), made by etching carbides
with halogens at elevated temperature,
have also been demonstrated as offer-
ing double the volumetric capacity of
coconut shell activated carbon. How-
ever, CDCs will likely remain substan-
tially more expensive than coconut
shell carbon because of raw material
and production costs, and thus have
limited potential for most of the com-
mercial market.
Carbon nanotubes have also attract-
ed substantial interest over the past
decade for supercapacitor applications.
In practice, single-walled nanotubes
remain prohibitively expensive, while
multi-walled nanotubes offer perfor-
mance on a par or slightly inferior to
activated carbon, but at a higher cost
(well over $50 per kg). Nanotubes also
have issues with toxicity due to retained
catalysts, complicating manufacturing
and eventual device disposal.
Graphene, which consists of carbon
sheets one atom thick giving a theoreti-
cal surface area of 2,630 square meters
per gram, has attracted much attention
from carbon researchers.
While the high gravimetric capac-
ity of graphene is extremely attractive
from the perspective of fully utilizing
the carbon and has attracted much aca-
demic attention, for a device the low
density seen due to poor packing (fluffi-
ness) inherently corresponds to poorer
energy density than activated carbon.
Graphene electrodes, consisting of
planes of carbon, have relatively low
density, due to poor packing when
the planes lie skewed to each other.
This corresponds to large open spaces
within the electrode. These open spaces
fill with electrolyte when the device is
made, adding weight to the device and
reducing its energy density. By contrast,
conventional activated carbons are rel-
atively densely packed, so that a smaller
amount of electrolyte is needed to fill
the interparticle voids.
Because of the tighter packing of
materials, volumetric energy density
is greater for activated carbon super-
capacitors than for graphene. Further-
more, the electrolyte within the inter-
particle voids is inactive mass within
the supercapacitor, so that even on a
weight-for-weight basis supercapaci-
tors containing activated carbon have
greater energy density than those con-
taining graphene.
Unless a way can be found to effi-
ciently pack graphene flakes within an
electrode while maintaining electrolyte
access, graphene cannot compete with
activated carbon for device energy
density.
A number of start-ups, including
Angstron Materials, Graphene Energy,
Graphene Frontiers and XG Sciences
are actively working to develop gra-
phene-based supercapacitors.
Future pricing
Current pricing on graphene is over
$100 per kilogram. Cost projections
from $5 per kilogram to $40 per kilo-
gram or so are posited by a number of
sources; because new processes are still
being developed for graphene produc-
tion, it is too early to tell what pricing
will look like in the future.
Furthermore, it is unclear whether it
will be possible to stack graphene lay-
ers tightly enough to have sufficient en-
ergy density to compete with conven-
tional activated carbon.
Aside from issues with cost and en-
ergy density, issues with cyclability also
plague novel supercapacitor materials.
Supercapacitor manufacturers achieve
100,000s of cycles with present-day
materials; by contrast, some research
and development laboratories and uni-
versities only focus on achieving 100s
or 1,000s of cycles. This gap represents
part of the misunderstanding between
device manufacturers and material de-
velopers.
Supercapacitor manufacturers achieve 100,000s
of cycles with present-day materials; by contrast,
some research and development laboratories
and universities only focus on achieving 100s or
1,000s of cycles. This gap represents part of the
misunderstanding between device manufacturers
and material developers.
Graphene’s long-term pricing and performance are
uncertain since graphene manufacturing is still in its infancy.

3. 12 Batteries International Summer 2013 www.batteriesinternational.com
OPINION — SUPERCAP CARBON PRICING
Given what has been seen in the past,
unless high performance carbons can be
developed offering well over double the
performance of conventional activated
carbons, it is unlikely that advanced su-
percapacitor carbons will find success
in the marketplace.
In addition to misunderstanding the
requirements for a successful market
entry, the would-be supercapacitor car-
bon manufacturers have overestimated
the size of the market for their material.
The overall market for supercapacitors
was roughly $400 million as of 2010;
based on this value the total market for
supercapacitor carbon is no more than
$30 million per year.
Over-optimism
Market research from outfits such as
IDTechEx and Transparency Market
Research suggest a market of $2 bil-
lion to $3 billion in the next three to
four years, which we feel to be an over
optimistic estimation of the growth
potential. Realistically, the market will
grow between 10% to 15% CAGR in
the next several years. The price of car-
bon-based supercapacitors will likely
decrease in years to come; they do not
incorporate any rare materials like in-
dium or rare earth elements, and there
is still room for improved manufac-
turing efficiency through incremental
improvements and economies of scale.
Therefore, there will be increasing pres-
sure for low cost supercapacitor car-
bons.
Overly optimistic market projections
have been used successfully by start-ups
to attract investments.
US government funding agencies also
used optimistic market projections to
justify large investments in superca-
pacitors. US government funding for
supercapacitor carbon development
has been substantial and about $30
million has been spent in the last five
years. This seems unreasonably high
for an annual market size of $30 mil-
lion. Similar sums have been invested
by private equity based on anticipated
rapidly expanding markets for superca-
pacitors.
Because of the limited size of the su-
percapacitor carbon market compared
to the investment required to enter the
market and the long time to market, it
is extremely likely that many firms will
fail in the marketplace. It will not be
surprising to witness similar failures in
supercapacitor carbon manufacturers
as have been seen with high profile bat-
tery start-ups.
Despite the significant work under-
taken in developing supercapacitor
carbons offering higher performance
at a premium price, very little work has
been undertaken on commercializing
carbons offering similar performance
to coconut-shell carbons at a lower
cost.
Kuraray, which sells coconut shell
carbon, dominates the supercapaci-
tor carbon market. This is a premium
product that took Kuraray several
years to develop, which has ash content
below 1% with iron and halogen con-
tent less than 100 ppm to enable high
supercapacitor cyclability.
By contrast, conventional activated
carbon made from wood, coal and the
like costs less than $4 per kg as com-
pared to $15 per kg for supercapacitor
carbon.
While the process control needed to
achieve high energy density and the
post-processing needed to achieve high
purity may add to the final product
cost, the market opportunity for pro-
ducing a lower-cost supercapacitor ac-
tivated carbon appears to exist.
Over the past few years, Calgon Car-
bon, a large player in conventional ac-
tivated carbon, has been working on
technically and economically competi-
tive supercapacitor carbons, and some
other activated carbon manufacturers
may be. Opportunities also exist for
sugar-derived carbon currently being
developed by TDA Research, Inc. and
MeadWestvaco.
Furthermore, an opportunity also ex-
ists to produce supercapacitor carbons
with maybe double the performance of
coconut-shell carbon at a reasonable
cost premium (30% higher than cur-
rent material).
Size constraints
However, this market niche may be lim-
ited to 10%-15% of the overall market.
Because of the small size of the market
available for exotic carbons in super-
capacitors, some of the supercapacitor
carbon manufacturers are looking to
enter other markets such as lead acid
battery carbons, which is even more
price sensitive than the supercapacitor
market.
Furthermore, the low margins present
in the supercapacitor industry may be
what led Gore, a leading manufacturer
of carbon supercapacitor electrodes, to
exit the market in 2011. The market
for supercapacitor carbons is extremely
price-sensitive, and those looking to en-
ter the market must take this into ac-
count.
Over the past 20 years or so, high
energy density supercapacitor car-
bons have been a hot research topic.
Nonetheless, many of these carbons
have failed in the marketplace and,
we predict, will continue to fail, due
to the nature of the supercapacitor
market.
US government funding for supercapacitor carbon development has been about $30
million in the last five years. This seems unreasonably high for an annual market size of
$30 million.
Ranjan Dash
is a techno-
commercial
professional with
over 10 years of
experience in the
development
management of
materials science related technologies.
Most recently, he was chief execu-
tive officer of Y-Carbon, before that he
worked for Maxwell Technologies.
Lawrence
Weinstein is an
electrochemical
and materials
science profes-
sional. From
2008 to 2011,
he worked on supercapacitor carbons,
carbon electrodes, and capacitive
desalination at Y-Carbon, a Drexel Uni-
versity spinoff.Since 2011, he has been
developing novel batteries at FlexEl.