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Linear and non-linear pseudocapacitances with or without diffusion control

Chen, George Zheng

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Abstract

Pseudocapacitance is an important reversible charge storage mechanism in many electrode materials. Although the concept was first proposed in early 1960s, it has been more widely studied following the observation of rectangular cyclic voltammograms (CVs) when testing some transition metal oxides and electronically conducting polymers, and the association with supercapacitor. However, interpretation of pseudocapacitance is inconsistent in the literature. Although all agree that materials are pseudocapacitive if they undergo Faradaic reactions and exhibit rectangular CVs, some have regarded any surface confined Faradaic reactions which may present non-rectangular or even peak-shaped CVs to be pseudocapacitive. In the case of rectangular CVs, the amount of charge stored in the electrode is a linear function of the electrode potential, whilst for non-rectangular or peak-shaped CVs, the relationship is non-linear. It is shown in this article that only linear pseudocapacitance is of relevance to supercapacitor, but non-linear pseudocapacitance may find applications in rechargeable battery and supercapattery. Further, it is clarified that the equation i ​= ​k1v ​+ ​k2v1/2 is useful in analysis of electrode kinetics in terms of surface confinement and diffusion control. However, this kinetic equation is blind to the thermodynamically determined charge storage mechanisms as shown by experimental evidence, and should not be used to differentiate non-capacitive Faradaic processes from pseudocapacitance, either linear or non-linear.

Citation

Chen, G. Z. (2021). Linear and non-linear pseudocapacitances with or without diffusion control. Progress in Natural Science, 31(6), 792-800. https://doi.org/10.1016/j.pnsc.2021.10.011

Journal Article Type Article
Acceptance Date Oct 24, 2021
Online Publication Date Nov 19, 2021
Publication Date 2021-12
Deposit Date Nov 26, 2021
Publicly Available Date Nov 26, 2021
Journal Progress in Natural Science: Materials International
Print ISSN 1002-0071
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 31
Issue 6
Pages 792-800
DOI https://doi.org/10.1016/j.pnsc.2021.10.011
Keywords General Materials Science
Public URL https://nottingham-repository.worktribe.com/output/6790048
Publisher URL https://www.sciencedirect.com/science/article/pii/S1002007121001684?via%3Dihub

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