Nonequilibrium Electrochemical Phase Maps: Beyond Butler-Volmer Kinetics

TL;DR

This paper introduces a computational framework for creating nonequilibrium phase maps in electrochemical systems using advanced kinetic models beyond traditional Butler-Volmer kinetics, highlighting the influence of various parameters on phase behavior.

Contribution

Develops a Julia-based numerical tool for modeling nonequilibrium phase transformations with general kinetic models, extending beyond analytical Butler-Volmer solutions.

Findings

Critical current magnitude varies significantly across kinetic models.

Model parameters like temperature and reorganization energy impact phase behavior.

Numerical inversion enables analysis of complex integral-based kinetic models.

Abstract

Electrochemical kinetics at electrode-electrolyte interfaces are crucial to understand high-rate behavior of energy storage devices. Phase transformation of electrodes is typically treated under equilibrium thermodynamic conditions, while realistic operation is at finite rates. Analyzing phase transformations under nonequilibrium conditions requires integrating nonlinear electrochemical kinetic models with thermodynamic models. This had only previously been demonstrated for Butler-Volmer kinetics, where it can be done analytically. In this work, we develop a kinetic modeling package in the Julia language capable of efficient numerical inversion of rate relationships for general kinetic models using automatic differentiation. We demonstrate building nonequilibrium phase maps, including for models such as Marcus-Hush-Chidsey that require computation of an integral, and also discuss the impact of a variety of assumptions and model parameters (such as temperature, reorganization energy, activity, and ideal solution interaction energy), particularly on high-rate phase behavior. Even for a fixed set of parameters, the magnitude of the critical current can vary by in excess of a factor of two amongst kinetic models.