Power Electronics

European Ultracapacitor Research Focuses on Improving Energy Density

According to research from Frost & Sullivan, ultracapacitor manufacturers are targeting transport applications such as hybrid vehicles, trolleys and buses, although ultracapacitors are currently in use for small devices (1 F to 10 F).

Researchers and companies are making progress to resolve issues such as series resistance, cell resistance and low energy density so that ultracapacitors can be used in transport applications. Researchers at the Université Paul Sabatier, Toulouse, are focusing on activated carbon ultracapacitors and working on the current collector/active material film interface to reduce series resistance. Furthermore, the research team is experimenting on areas such as the synthesis of new activated carbons or new forms of carbons to store higher energy and the improvement of the energy density of the ultracapacitors by associating a battery type electrode to an activated carbon electrode.

"A significant difference that distinguishes this research team's work is that they apply the surface treatment science to the current collector/active material interface in ultracapacitor electrodes, to improve the power," says Frost & Sullivan Research Analyst Viswanathan Krishnan. "This concept is rather novel since it requires a material/corrosion/surface science culture in addition to an electrochemical/energy storage culture."

Ultracapacitors suffer from low energy densities when compared to rechargeable batteries. Because energy density is correlated with the morphological characteristics of the porous carbon electrodes, such as the surface area and pore size distribution of the carbon, researchers and industry participants have been working on tailoring the porosity of carbon so as to achieve a higher energy density.

Apart from working on the development of capacitor modules for hybrid cars, researchers at the Electrochemistry Laboratory, Paul Scherrer Institut, Switzerland, have carried out a fundamental research on capacitance limits of activated carbon and their degradation mechanisms and life time aspects. The findings of this research indicate that carbons with surface area greater than 1500 m2/g do not increase capacitance and gas evolution and dimensional changes affect operating lifetime.

"Advantages such as high power density, high recharging cycles, reliability and easy recyclability have attracted various applications for ultracapacitors ranging from portable applications to automobiles," says Krishnan. "However, the ability of ultracapacitors to compete with the conventional batteries in terms of cost and energy density are crucial to determine the pace of technology adoption in the market."

These and other aspects of ultracapacitors are discussed in the Frost & Sullivan report, “Analysis of Ultracapacitors Technologies—Global Trends and Developments.”

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