Conductivity of Concentrated Electrolytes

TL;DR

This paper develops a stochastic density functional theory with a modified Coulomb potential to accurately predict ionic solution conductivity at high concentrations, aligning well with experimental data up to 3 molars.

Contribution

It introduces a new theoretical approach that extends conductivity predictions to higher concentrations without fitting parameters.

Findings

Accurately predicts conductivity up to 3 molars

Provides a compact analytical expression for conductivity

Suppresses unphysical short-range electrostatic interactions

Abstract

The conductivity of ionic solutions is arguably their most important trait, being widely used in electrochemical, biochemical, and environmental applications. The Debye-H\"uckel-Onsager theory successfully predicts the conductivity at very low ionic concentrations of up to a few millimolars, but there is no well-established theory applicable at higher concentrations. We study the conductivity of ionic solutions using a stochastic density functional theory, paired with a modified Coulomb interaction that accounts for the hard-core repulsion between the ions. The modified potential suppresses unphysical, short-range electrostatic interactions, which are present in the Debye-H\"uckel-Onsager theory. Our results for the conductivity show very good agreement with experimental data up to 3 molars, without any fit parameters. We provide a compact expression for the conductivity, accompanied by a simple analytical approximation.