Capacitance material

Schuster EW, Allen SJ, D ltri MP (2000) Capacitated materials requirements planning and its application in the process industries. Journal of Business Logistics 21 (1) 169-187... 

The ESs mentioned above consist of two electrodes with the same type of capacitive materials made from either EDL capacitive materials or pseudocapacitive materials (symmetrical configuration). In order to further increase the operating potential window, energy, and power density, a new type of ES has been developed, which is known as hybrid capacitors. With extensive achievements in this area, various types of hybrid ESs have been developed. Generally, hybrid capacitors utilize both the EDL capacitance and faradaic reaction to store charges. The hybrid capacitors reviewed in this book include (1) ESs based on composite electrodes made from both EDL capacitive materials and pseudocapacitive materials (2) asymmetric ESs with one EDL electrode and another pseudocapacitive or battery-type electrode and (3) asymmetric ESs with one pseudocapacitive electrode and another rechargeable battery-type electrode. 

Sharma et al. reported a novel and cost-effective fabrication of the CNT/ PPy nanocomposite on the poly(4-styrenesulfonic acid) (PSS)-dispersed MWNTs [79]. PSS not only stabilized the MWNT suspension but also provided charged groups to facilitate an ordered and uniform growth of pseudo-capacitive materials around the MWNTs through electrostatic attractions. The in situ oxidation of Py with KMnO yielded molecular-level dispersion of the MnO in PPy matrix that improved the electronic conductivity, mechanical stability, and pseudo-capacitance. The MWNT-PSS/PPy MnOj ternary nanocomposite exhibited a high SC of 268 F/g at 5 mV/s and only 7% faded in the specific capacity at 100 mV/s and 10% faded in the same after 5000 CV cycles (Figure 8.9). 

Conducting polymers constitute another category of promising pseudo-capacitive materials. The most common ones include polypyrrole (PPy), polyaniline (PANI), and poly-(3,4)-ethylenedioxythiophene (PEDOT). This group is of particular interest due to low cost and ease of synthesis. These compounds can be polymerized directly onto a collector material via EPD. Alternatively, the polymerization can be done within surfactant emulsions... 

Similar to the value proposition behind composite electrodes that use pseudo-capacitive materials on high surface area carbon supports, hybrid structures offer improvements to the energy limitations of EDLC systems. Asymmetric systems utilize one EDLC electrode with the other made of either a pseu-docapacitive material or a lithium electrode. Systems employing these techniques trade lower cycle life and power for an increase in energy density. 

Current collectors are used in ES devices to gather and feed electrical charges stored within the active capacitive material. In most cases, the conduction of charge throughout the active material of an electrode is insufficient and provides a large amount of resistance that can ruin performance characteristics of an otherwise acceptable ES material. Efficient contacts and additives are needed to effectively transport charge current and provide a system with sufficient power. 

Capacitance, Material as dielectric Capacitance, Air (or Vacuum) as dielectric... 

Fig. 1 The expected a CV, b GCD, and c EIS results for an ideally capacitive material. The potential values in a and b extending to negative values indieate that the characterisation was performed in three-electrode eonfiguration and in which the potential was measured against a standard reference...

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