Electrochemical supercapacitors and their complementarity to fuel cells and batteries
Other energy conversion related topics
Published Online: 15 DEC 2010
Copyright © John Wiley & Sons, Ltd. All rights reserved.
Handbook of Fuel Cells
How to Cite
Conway, B. E. 2010. Electrochemical supercapacitors and their complementarity to fuel cells and batteries. Handbook of Fuel Cells. .
- Published Online: 15 DEC 2010
In recent years, so-called supercapacitors have been developed providing specific capacitances on the order of 50–100 Farads g−1 of high surface area substrates, e.g., carbon powders, fibers or aerogels, and some transition-metal oxide films having specific real areas up to ca. 2000 m2 g−1. The capacitance of carbon-based devices originates from the double-layer capacity of the carbon/liquid electrolyte interfaces, giving rise to a high degree of reversibility of the charging/discharging processes, leading to perceived operability at large power densities. The large achievable specific capacitance provides systems for substantial charge and electrical energy storage, complementary to that provided by batteries. However, on account of the distributed nature of capacitative, C, and ohmic, R, components of the impedance, a broad range of RC time-constants arises, corresponding to a power spectrum. Hence high power operation is available from only a fraction of the total capacitance at large current densities or a.c. frequencies, or in short-time pulses.
An important application of supercapacitors has been envisaged in a load-leveling role in hybrid configuration with fuel cells or rechargeable batteries. To achieve this, the relation between operable power densities and achievable energy densities of each of the components has to be evaluated in terms of so-called Ragone plots in a complementary way.
- Electrochemical capacitors;
- Hybrid power systems;