Cell Designs Symmetric versus Asymmetric

Cyclic voltammograms of differently treated active carbon (AC) materials illustrating overlap region and overall potential window. (Source Khomenko, V., E. Raymundo-Pinero, and F. Beguin. 2010. Journal of Power Sources, 195,4234-4241. With permission.) 

Another interesting fabrication technique is designing asymmetric carbon cells with controlled functionalities. Each electrode is based on a different carbon precursor and is subjected to different treatment to produce pseudocapacitance. The pseudocapacitance boosts performance but more importantly it extends the overpotential and prevents gas evolution (Eigure 3.20) [48]. The results can achieve capacitance as high as 300 F.g at 1 A.g 1. This capacitance is spread over a reversible potential window of 1.6 V, leading to energy densities of 10 to 30 Wh.kgyi and power levels of 10 to 20 kW.kg 1 [48]. 

Based on the charge matching of the electrodes in a two-electrode configuration, a natural open circuit resting position of the device will exist between 

Electrochemical Characteristics of Symmetric and Asymmetric ESs Based on Different Active Materials 

Source Khomenko, V. et al. 2005. Applied Physics A, 82,567-573. With permission. Carbon Maxsorb is a high-surface-area activated carbon. 

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