Energy specific capacitance

The fabrication of supercapacitors and electrochemical actuators that could be used as artificial muscles is another alternative for nanotube applications. Supercapacitors already were built on hybrid vehicles because this could provide rapid acceleration and store braking energy electrically. When using sheet electrodes with SWNT and MWNTs, it is possible to obtain specific capacitance of 180 and 102 F/g and power densities of 20 and 8kW/kg, respectively. 

Hence, in the case of a capacitor built from two electrodes with different capacitance, the component of smaller capacitance will contribute more to the total value because of the reciprocal dependence. The capacitance is expressed in farad (F), which is the charge (in coulombs) accumulated in a defined range of voltage (1 F = 1 C/1 V). The specific capacitance can be related to the electrode mass (F/g), to the electrode volume (F/cm ), or to the electrode surface (F/cm ). The amount of electrical energy W accumulated in electrochemical capacitor is proportional to the capacitance C and to the square of voltage U, according to formula (23.5) ... 

The specific capacitance C, energy density E, and corresponding power density P are defined by the following equations [4]... 

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