Ion-Pairing: A Bygone Treatment of Electrolyte Solutions?

Abstract

The field of battery research has advanced significantly in the past 50 years. Despite the importance of electrolyte solutions for these devices, the battery community's perception of this essential component arguably aligns more with the 19th century reasoning than the 20th centuries advancements. This paper traces the historical evolution of electrolyte theories, emphasizing the consequences of an overly ion-pairing-centric view, and the benefits of a more nuanced analysis. A quantitative example is provided. It will be shown that an association constant of (Formula presented.) can be obtained from conductivity measurements of sodium acetate in water. However, studying the activity coefficients of this electrolyte reveals that this association constant would result in an unreasonable scenario where the free ions behave as uncharged particles at low concentrations. The aim is to promote a nuanced perspective on electrolyte solutions within the battery community, while also providing a collection of reputable references for the interested readers further studies.