Issue 9, 2018

Electrochemical potential window of battery electrolytes: the HOMO–LUMO misconception

Abstract

A widespread misconception in the lithium ion battery literature is the equality of the energy difference of HOMO and LUMO of the solvent with the electrochemical stability window. HOMO and LUMO are concepts derived from approximated electronic structure theory while investigating electronic properties of isolated molecules, and their energy levels do not indicate species participating in redox reactions. On the other hand, redox potentials are directly related to the Gibbs free energy difference of the reactants and products. While redox potentials in some cases show strong correlation with HOMO energies, the offset can be of several eVs. Presence of electrolytes and other molecules can also significantly affect the redox potentials of the solvent leading to offset as high as 4 eV from the HOMO energies. In this opinion we provide a correct thermodynamic representation for the electrochemical stability of the electrolyte, based on redox potentials and Fermi level of the electron in solution, and demonstrate that the use of terms HOMO and LUMO should be avoided when talking about the electrochemical stability of electrolytes. Instead, it is more correct to speak of potential of electrolyte reduction at negative potentials, and of potential of solvent oxidation at positive potentials.

Graphical abstract: Electrochemical potential window of battery electrolytes: the HOMO–LUMO misconception

Supplementary files

Article information

Article type
Opinion
Submitted
02 Maijs 2018
Accepted
27 Jūl. 2018
First published
28 Jūl. 2018

Energy Environ. Sci., 2018,11, 2306-2309

Electrochemical potential window of battery electrolytes: the HOMO–LUMO misconception

P. Peljo and H. H. Girault, Energy Environ. Sci., 2018, 11, 2306 DOI: 10.1039/C8EE01286E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements