Costentin Cyrille, Savéant Jean-Michel
Université Paris Diderot, Sorbonne Paris Cité , Laboratoire d'Electrochimie Moléculaire , Unité Mixte de Recherche Université - CNRS No. 7591 , Bâtiment Lavoisier, 15 rue Jean de Baïf , 75205 Paris Cedex 13 , France . Email:
Chem Sci. 2019 May 9;10(22):5656-5666. doi: 10.1039/c9sc01662g. eCollection 2019 Jun 14.
The two main types of charge storage devices - batteries and double layer charging capacitors - can be unambiguously distinguished from one another by the shape and scan rate dependence of their cyclic voltammetric current-potential (CV) responses. This is not the case with "pseudocapacitors" and with the notion of "pseudocapacitance", as originally put forward by Conway After insisting on the necessity of precisely defining "pseudocapacitance" as involving faradaic processes and having, at the same time, a capacitive signature, we discuss the modelling of "pseudocapacitive" responses, revisiting Conway's derivations and analysing critically the other contributions to the subject, leading unmistakably to the conclusion that "pseudocapacitors" are actually true capacitors and that "pseudocapacitance" is a basically incorrect notion. Taking cobalt oxide films as a tutorial example, we describe the way in which a (true) electrical double layer is built upon oxidation of the film in its insulating state up to an ohmic conducting state. The lessons drawn at this occasion are used to re-examine the classical oxides, RuO, MnO, TiO, NbO and other examples of putative "pseudocapacitive" materials. Addressing the dynamics of charge storage-a key issue in the practice of power of the energy storage device-it is shown that ohmic potential drop in the pores is the governing factor rather than counter-ion diffusion as often asserted, based on incorrect diagnosis by means of scan rate variations in CV studies.
两种主要的电荷存储装置——电池和双层充电电容器——可以通过其循环伏安电流-电势（CV）响应的形状和扫描速率依赖性彼此明确区分。但“赝电容器”以及最初由康威提出的“赝电容”概念并非如此。在坚持必须将“赝电容”精确定义为涉及法拉第过程且同时具有电容特征之后，我们讨论了“赝电容”响应的建模，回顾了康威的推导并批判性地分析了该主题的其他贡献，明确得出结论：“赝电容器”实际上是真正的电容器，“赝电容”是一个基本错误的概念。以氧化钴薄膜作为示例教程，我们描述了在薄膜从绝缘状态氧化到欧姆导电状态时构建（真正的）电双层的方式。在此过程中吸取的经验教训被用于重新审视经典氧化物、RuO、MnO、TiO、NbO以及其他所谓“赝电容”材料的示例。在探讨电荷存储动力学这一储能装置功率实践中的关键问题时，结果表明，基于CV研究中扫描速率变化的错误诊断，孔隙中的欧姆电势降是主导因素，而非通常所认为的反离子扩散。
