Disentangling faradaic, pseudocapacitive, and capacitive charge storage: A tutorial for the characterization of batteries, supercapacitors, and hybrid systems

T. Schoetz, L. W. Gordon, S. Ivanov, A. Bund, D. Mandler, R. J. Messinger*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

78 Scopus citations


Today's electrochemical energy storage technologies aim to combine high specific energy and power, as well as long cycle life, into one system to meet increasing demands in performance. These properties, however, are often characteristic of either batteries (high specific energy) or capacitors (high specific power and cyclability). To merge battery- and capacitor-like properties in a hybrid energy storage system, researchers must understand and control the co-existence of multiple charge storage mechanisms. Charge storage mechanisms can be classified as faradaic, capacitive, or pseudocapacitive, where their relative contributions determine the operating principles and electrochemical performance of the system. Hybrid electrochemical energy storage systems can be better understood and analyzed if the primary charge storage mechanism is identified correctly. This tutorial review first defines faradaic and capacitive charge storage mechanisms and then clarifies the definition of pseudocapacitance using a physically intuitive framework. Then, we discuss strategies that enable these charge storage mechanisms to be quantitatively disentangled using common electrochemical techniques. Finally, we outline representative hybrid energy storage systems that combine the electrochemical characteristics of batteries, capacitors and pseudocapacitors. Modern examples are analyzed while step-by-step guides are provided for all mentioned experimental methods in the Supplementary Information.

Original languageAmerican English
Article number140072
JournalElectrochimica Acta
StatePublished - 20 Apr 2022

Bibliographical note

Funding Information:
T.S., L.W.G., and R.J.M. gratefully acknowledge funding from the U.S. National Aeronautics and Space Administration (NASA) via the NASA-CCNY Center for Advanced Batteries for Space under cooperative agreement no. 80NSSC19M0199 and the U.S. National Science Foundation (NSF) under CAREER award no. CBET-1847552. D.M. acknowledges support from the Israel National Center for Electrochemical Propulsion (INREP) and the Israel Science Foundation-Chinese National Science Foundation (ISF-CNSF) program under award no. 3650/21. The authors thank Arne Jannaschk for providing the open-source JavaScript to separate diffusion-limited and non-diffusion-limited charge storage contributions.

Publisher Copyright:
© 2022


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