Electrochemical capacitors compared with batteries

Fig. 13.53. Ragone plot comparing electrochemical capacitors with lithium ion batteries and electrolytic capacitors. (Reprinted from Electrochemical Society Proc. 97-18, p. 610, Fig. 1, 1997. Reproduced by permission of The Electrochemical Society Inc.)...

Figure 1.2. The different electrochemical devices, super capacitors, batteries and fuel cells are compared with fuel motors within the same Ragone diagram...

An electric double-layer capacitor, also known as supercapacitor, pseudocapacitor, electric double layer capacitor (EDLC), supercapacitor or ultracapacitor is an electrochemical capacitor with relatively high energy density. Compared to conventional capacitors the energy density is typically on the order of thousands of times greater than an electrolytic capacitor. In comparison with conventional batteries or fuel cells, EDLCs have lower energy density but a much higher power density. 

Fig. 7.55 For electrochemical applications the question of how much and how rapidly energy per unit mass can be called up is extremely significant. The figure gives information in this respect for the lead accumulator, zinc-air battery, Uthium rocking chair battery and for modem fuel cells, and compares them with electrochemical capacitors (see also ptage 444). From Ref. [649].

As a compromise between the above two approaches, the third approach adopts nonactive (inert) materials as working electrodes with neat electrolyte solutions and is the most widely used voltammetry technique for the characterization of electrolytes for batteries, capacitors, and fuel cells. Its advantage is the absence of the reversible redox processes and passivations that occur with active electrode materials, and therefore, a well-defined onset or threshold current can usually be determined. However, there is still a certain arbitrariness involved in this approach in the definition of onset of decomposition, and disparities often occur for a given electrolyte system when reported by different authors Therefore, caution should be taken when electrochemical stability data from different sources are compared. 

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