Perspective—The Correct Assessment of Standard Potentials of Reference Electrodes in Non-Aqueous Solution

The challenges facing metal-air batteries have prompted fundamental studies of non-aqueous electrochemistry. However it appears that contributors in the field are not aware that the potentials of Li/Li + , Na/Na + , K/K + , and Mg/Mg 2+ electrodes depend on the nature of solvent due to the cation solvation. Therefore, it is imperative to define a clear potential scale that can be correlated in different solvents. Here we report on the strong effect of the solvent on the Li/Li + redox potential and discuss the use of the ferrocene/ferrocenium couple as internal or external standard for the measurements in non-aqueous solvents in lithium-ion and lithium-0 2 battery systems.