Redox activity supercapacitors

Zhong, J., Fan, L.-Q., Wu, X., Wu, J.-H., Liu, G.-J., Lin, J.-M., Huang, M.-L., Wei,Y.-L., 2015b. Improved energy density of quasi-solid-state supercapacitors using sandwich-type redox-active gel polymer electrolytes. Electrochim. Acta 166,150-156. 

Yigit, D., M. Giillii, T. Yumak, and A. Sinag. 2014. Heterostructuredpoly(3,6-dithien-2-yl-9H-carbazol-9-yl acetic acid)/Ti02 nanoparticles composite redox-active materials as both anode and cathode for high-performance symmetric supercapacitor applications. Journal of Materials Chemistry A 2 6512-6524. 

Mai, L. Q., A. Minhas-Khan, X. Tian et al. 2013. Synergistic interaction between redox-active electrolyte and binder-free functionalized carbon for ultrahigh supercapacitor performance. Nature Communications 4 1-7. 

Roldan, S., M. Granda, R. Menendez, R. Santamarfa, andC. Blanco. 2011. Mechanisms of energy storage in carbon-based supercapacitors modified with a quinoid redox-active electrolyte. Journal of Physical Chemistry C 115 17606-17611. 

Yu, H., L. Fan, J. Wu et al. 2012. Redox-active alkaline electrolyte for carbon-based supercapacitor with pseudocapacitive performance and excellent cyclability. RSC Advances 2 6736-6740. 

Chen, W., R. B. Rakhi, and H. N. Alshareef. 2013. Capacitance enhancement of polyaniline coated curved-graphene supercapacitors in a redox-active electrolyte. Nanoscale 5 4134-4138. 

Batteries/Supercapacitors. Electrochemical charge storage systems (batteries and supercapacitors) are currently employed in a wide variety of applications (14) there is a constant demand for performance improvements and reduced environmental impact. Redox-active polymers are promising materials for use in batteries and supercapacitors because of their hi gravimetric and volumetric charge capacities, fast charge/discharge rates, robustness, environmentally friendly nature, and lower costs relative to noble metal oxides (406-408). 

Room-temperature ionic liquids (RTILs) are intrinsic ionic conductors which have been successfully employed as nonflammable/nonreactive electrolytes in a range of electrochemical devices, including dye-sensitized solar cells [1,2], lithium batteries [3], fuel cells [4], and supercapacitors [5]. The quantification of mass transport is of interest in any solvent, particularly those employed in electrochemical devices, as it affects the ultimate rate/speed at which the device can operate. The diffusivity or diffusion coefficient (D) of a redox active species, along with other thermodynamic parameters such as the bulk concentration (c) and the stoichiometric number of electrons (n) that are of fundamental significance in any study of an electrode reaction, can be determined experimentally using a range of electroanalytical techniques [6], As with any analytical method, the ideal electroanalytical technique for parameter characterization should be accurate, reproducible, selective, and robust. In many respects voltammetric methods meet these requirements, since they can be... 

Faradaic in nature and therefore is different farm Pseudocapacitance usually originates from electrosorption (specific adsorption) processes and related partial electron transfer or surface charging (Section 5-5). On metal oxide "supercapacitor" types of electrodes (such as iridium and ruthenium oxides) possessing several oxidation states, pseudocapacitance originates from potential dependence of multiple oxidation/reduction couples that are active on the surfaces of the materials. Another coiiunon source of pseudocapacitance is charging-discharging of redox-active polymers such as polyaniline and polypyrrole. 

This chapter intends to discuss the fundamental role played by carbons, taking particularly into account their nanotexture and surface functionality. The general properties of supercapacitors are reviewed, and the correlation between the double-layer capacitance and the nanoporous texture of carbons is shown. The contribution of pseudocapacitance through pseudofaradaic charge transfer reactions is introduced and developed for carbons with heteroatoms involved in functionalities able to participate to redox couples, e.g., the quinone/hydroquinone pair. Especially, we present carbons obtained by direct carbonization (without any further activation) of appropriate polymeric precursors containing a high amount of heteroatoms. 

Senthilkumar, S. T., R. K. Selvan, and J. S. Melo. 2013. Redox additive/active electrolytes A novel approach to enhance the performance of supercapacitors. Journal of Materials Chemistry A 1 12386-12394. 

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