Electrochemistry consists of two core fields: electrodics and ionics. The electrodics mainly deals with the charge transport at the electrified interface, while the ionics concerns on the ion transport and speciation in the ionic media. For the last century, the electrochemistry society has focused mainly on the electrodics, whereas the ionics has seen no noticeable progress. This indifference to the ionics is partly due to the misunderstanding that the ionics is an old-fashioned field, and also due to the absence of the appropriate tools and theories. However, over the past decade, we have come to realize the importance of the ion conduction and solution structure in the concentrated electrolytes in developing energy storage/conversion devices (e.g., batteries, fuel cell, capacitors). At the same time, we are now lucky enough to enjoy remarkable advances in the analytical instruments and computing power, which now enable us to tackle the super-complex topic.
This talk will introduce some recent findings on the solution structure and ionic conduction behaviors in the Li-ion battery electrolytes including PC solutions of LiPF₆ and LiBF₄ and EC/linear carbonate solutions of LiPF₆ in an association with the ion-ion and ion-solvent interactions as investigated using Raman and pulse-field-gradient NMR measurements and a rather unfamiliar dielectric relaxation spectroscopy.