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Skeleton Technologies receives US patent for nanoporous carbon powder supercapacitor material; higher energy and power densities and lower cost

Skeleton Technologies, an energy-storage start-up located in Tartu, Estonia, was recently awarded a US patent (#7,803,345) on its nanoporous carbon powder supercapacitor material. The material possesses very high surface area and a high packing of nanopores, according to Skeleton, which aims to commercialize the carbon material and supercapacitor technology. The company was restructured in 2009; until then it acted as a private research center providing contract research to companies such as Toyota Motor Company, Samsung SDI and others.

The material enables the modification of the porosity and pore-size structure of carbon particles in a way in which the surface of carbon particles contain larger pores than the inside of particles. This allows increased access to nanopores by the liquids, in turn raising the energy density. Low internal resistance of the nanostructured material raises the power density.

The patented material has also shown superior characteristics in molecular sieving, hydrogen storage and in electroactive devices, Skeleton says. The US patent and soon-to-be-granted EU patent gives the company protection for carbide-derived-carbons suitable for energy storage applications.

Skeleton Technologies says its supercapacitors based on the material have a two-fold advantage:

  • In specialized, high-performance applications where cost is not a critical driver, they can deliver more power and more energy than competitive offerings at the same weight and volume. Today the energy density and maximum power of Skeleton Technologies´ ultracapacitors reach 13 Wh/L and 70 kW/L respectively, roughly 50% higher energy density and 4x higher power density.

  • In more mass-market applications where cost is an issue, the technology enables delivering the same performance as competitive devices, but at a lower price and smaller, more compact form-factor.

First industry trials for the supercapacitors have been successfully carried out and Skeleton Technologies plans to enter the market with substantial production capability by 2013.

Although the ultracapacitor is not new technology, its utilization as a means for storing energy and delivering power is growing in several key application areas. The most popular segment today for ultracapacitor modules in the transportation market is for use in stop-start vehicles, and early-stage applications for ultracapacitors also include grid-scale energy storage and wind turbines. According to a new report from Pike Research, worldwide sales of ultracapacitors will grow tenfold from just $28.2 million in 2011 to $284.1 million by 2016, with cumulative revenue of $901.3 million during that period.

Ultracapacitors’ greatest advantages over their primary competition, batteries, are superior cycle life and power density. However, ultracapacitors are viewed as too expensive for most energy storage applications and the technology is commonly viewed as not sufficiently mature for transportation applications. That said, ultracapacitors are showing great promise in several niche applications, most notably the burgeoning market for stop-start vehicles.

—Pike senior analyst John Gartner

Oliver Ahlberg, a member of Skeleton Technologies’ board, agrees that so far the main barrier for entry for ultracapacitors has been high cost of the devices. However, he says, Skeleton’s patented material and unique electrode manufacturing technology allow it to significantly reduce the cost of the devices; the high performance of the material means that lower amounts of it can achieve the same results as competitors. This materials efficiency translates directly to a lower price for the devices—materials costs constitute about 80% of the total cost of production for ultracapacitors.

Skeleton is currently preparing a launch of Round A financing at the end of February.



As this process is being achieved in many places around the globe, it is doubtful if a patent should be granted to limit its application.

This could be a way to delay future lower cost BEVs.

The achieved energy and power densities are interesting, specially when coupled with very high energy density batteries, if price is low enough.


It's a little hard to translate the numbers they provide and compare them to Maxwell and Ioxus especially since they are not giving any Wh/kg or kW/kg numbers.

But assuming they are comparable to Ioxus volume numbers, these supercaps have about twice the energy density and about 6-7 times the power density of the cells currently offered from either Ioxus or Maxwell.

Again, it's hard to tell which "version" of their product they are referring to and what the cost will be.


At 13 Wh (~47 kJ) and 70 kW, it appears these capacitors can go from 0 to full in a bit under 700 msec.

GM's BAS II could use a 1-liter cap. 11 kW for 4 seconds is about what it needs, and it could be fully recharged in about 3 seconds at 15 kW.


Yes, it would be interesting to couple with GM's BAS II plus an extra clutch to decouple the ICE to recover more breaking energy, specially in stop and go city traffic situations.

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