Pseudocapacitor Electrode Materials

In this chapter, in order to make Mn02 more attractive for pseudocapacitor electrode materials, Mn02 was coated spontaneously on CNTs by the simple immersion of the CNTs into a KMn04 aqueous solution. The synthesis mechanism of the heterogeneous nucleation of Mn02 on the CNTs was investigated by in situ monitoring of the solution chemistry. 

Capacity also influences the energy value. Actually, most of the research effort is dedicated to improving the capacity of electrode materials. Since ACs are taken as reference, the cost of the materials is an important criterion at the industrial level. Most of the materials developed for EDLC are of little interest for applications, because of their cost and only slightly improved performance. By contrast, it will be shown that advanced carbon materials can be developed for pseudocapacitors. 

Hydrogel Polymer Electrolytes for Pseudocapacitors and Hybrid ESs As mentioned in Section 2.2 and similar to the research trend in the field of aqueous electrolytes, considerable work has focused on the development of hydrogel electrolytes for ESs with enhanced charge storage capacity, such as pseudocapacitors and hybrid ESs including asymmetric ESs. The electrochemical behavior of the pseudo-capacitive electrode materials is directly influenced by the nature of the electrolytes. 

Wang, L., Z. FI. Dong, Z. G. Wang, F. X. Zhang, and J. Jin. 2013. Layered a-Co(OH)2 nanocones as electrode materials for pseudocapacitors Understanding the effect of interlayer space on electrochemical activity. Advanced Functional Materials 23 2758-2764. 

Mefford, J. T., W. G. Hardin, S. Dai, K. P. Johnston, and K. J. Stevenson. 2014. Anion charge storage through oxygen intercalation in LaMn03 perovskite pseudocapacitor electrodes. Nature Materials 13 726—732. 

Jiang, J., J. P. Liu, R. M. Dingetal. 2011. Large-scale uniform a-Co(OH)j long nanowire arrays grown on graphite as pseudocapacitor electrodes. ACS Applied Materials and Interfaces 3 99-103. 

Despite many advances and an outstanding book [1], we are convinced that we have just begun to evaluate this field. Major advances can be expected from new electrolytes, better purification procedures, new electrode materials, and also from capacitors that include very fast electrochemical reactions (pseudocapacitors). Finally the problem of unsymmetrical voltage window deserves more attention. 

At the same time, a fundamental understanding of supercapacitor design, operation, performance, and component optimization led to improvements of supercapacitor performance, particularly increasing their energy density. To further increase energy density, more advanced supercapacitors called pseudocapacitors, in which the electroactive materials are composited with carbon particles to form composite electrode materials, were developed. The electrochemical reaction of the electroactive material in a pseudocapacitor takes place at the interface between the electrode and electrolyte via adsorption, intercalation, or reduction-oxidation (redox) mechanisms. In this way, the capacitance of the electrode and the energy density can be increased significantly. 

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