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ULTRACAPACITOR TECHNOLOGY
Ultracapacitor Principal
The alternative way to achieve high capacitance on the order of 10 F/cm3 is to use nanosized materials for electrode manufacture. These materials possess huge specific surface area - up to 2000 m2/g. Such materials include, in particular, special nanoporous activated carbon powders. Activated carbon consists of extremely small and very "rough" particles, sized in a range of 3-7 micron, which in bulk, forms a low-density volume of particles with pores of different size that resembles a sponge. Nanoporous material structure under electrone microscope. The ultracapacitor consists of two electrodes immersed into a special organic electrolyte. Very thin double electric layer, on the order of 1 nm, forms on the developed surface of each electrode under the applied external voltage. Schematic representation of this process is shown in a picture below: During the capacitor charging process, the charge is accumulated in the negative and positive carbon electrodes and maintained there by the attraction of cations and anions (positively and negatively charged particles of electrolyte), respectively. The amount of charge that can be maintained in the capacitor is proportional to the accessible surface of the electrodes that can interact with ions of electrolyte. Hence, as we increase the effective surface of the electrode the overall capacitance increases. The use of activated carbons allows to achieve tremendous capacitance value.
Ultracapacitor DesignOn the whole, there are two maror types of ultracapacitor cells: cycindrical and prismatic. A typical ultracapacitor cell resembles a sandwich, or a roll, of thin aluminum foil and carbon electrodes. To prevent the short circuits between the electrodes, an ionically permeable dielectric separator is used. The thin foils, acting as current collectors, are later joined to the corresponding current leads (negative and positive), which are used for technical connections. YUNASKO is developing prismatic ultracapacitor cells. Prismatic shape is beneficial due to maximazing efficiency of the packing cells into modules which is especially important for applications, where the space for the energy storage module is limited (in automobiles, consumer electronics etc).
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