Ion-vacancy coupled charge transfer model for ion transport in concentrated solutions

• 来源期刊: 中国科学:化学（英文版）
• 年，卷（期）: 2019,（4）
• 页码范围: 515-520
• 页数: 6页
• 语种: 英文

摘要

We present a conceptual framework for understanding and formulating ion transport in concentrated solutions,which pictures the ion transport as an ion-vacancy coupled charge transfer reaction.A key element in this picture is that the transport of an ion from an occupied to unoccupied site involves a transition state which exerts double volume exclusion.An ab initio random walk model is proposed to describe this process.Subsequent coarse-graining results in a continuum formula as a function of chemical potentials of the constituents,which are further derived from a lattice-gas model.The subtlety here is that what has been taken to be the chemical potential of the ion in the past is actually that of the ion-vacancy couple.By aid of this new concept,the driving force of ion transport is essentially the chemical affinity of the ion-vacancy coupled charge transfer reaction,which is a useful concept to unify transport and reaction,two fundamental processes in electrochemistry.This phenomenological model is parameterized for a specific material by the aid of first-principles calculations.Moreover,its extension to multiple-component systems is discussed.