Warburg Conductivity for Binary Electrolyte for Enabling Electrolyte Screening and Efficient Battery Operations

Abstract

Estimating the potential drop in a separator and an electrode is crucial for efficient battery operations and electrolyte screening. Currently, calculating the potential drop in the electrolyte phase for Li-ion batteries requires numerical simulation of coupled partial differential equations resulting from concentrated solution theory. In this study, we introduce the concept of Warburg conductivity to represent the potential drop due to concentration gradient in a binary electrolyte to simplify the theoretical treatment. Accurate quantification of this potential drop can facilitate the development of fast charging algorithms by allowing a higher voltage cutoff during battery charging. To express the potential drop in the binary electrolyte, four parameters are necessary: conductivity, diffusivity, transference number, and thermodynamic factor. While the effect of the conductivity on the potential drop in the electrolyte is straightforward (representing ionic resistance), this work introduces the concept of Warburg conductivity to combine the remaining three parameters and derive the expression of the Warburg resistance. By considering both ionic and Warburg resistances, a comprehensive understanding of the total potential drop in the electrolyte phase is achieved, which is essential for analyzing battery performance and electrolyte screening.