Marcus-Hush-Chidsey Kinetics at Electrode-Electrolyte Interfaces

TL;DR

This paper develops a unified framework incorporating DFT-calculated density of states into electrochemical kinetics models, improving understanding of electrode-electrolyte interface reactions in batteries and fuel cells.

Contribution

It introduces a method to explicitly include density of states in electrochemical reaction rate calculations, extending traditional models like Butler-Volmer.

Findings

Reaction rate deviations are minor for flat densities of states like Li.

Significant reaction rate variations occur for Cu due to d-band effects.

Fermi level pinning influences reaction asymmetry in solid-electrolyte interphases.

Abstract

Electrochemical kinetics at electrode-electrolyte interfaces limit performance of devices including fuel cells and batteries. While the importance of moving beyond Butler-Volmer kinetics and incorporating the effect of electronic density of states of the electrode have been recognized, a unified framework that incorporates these aspects directly into electrochemical performance models is still lacking. In this work, we explicitly account for the DFT-calculated density of states numerically in calculating electrochemical reaction rates for a variety of electrode-electrolyte interfaces. We first show the utility of this for two cases related to Li metal electrodeposition and stripping on a Li surface and a Cu surface (anode-free configuration). The deviation in reaction rates is minor for cases with flat densities of states such as Li, but is significant for Cu due to nondispersive d-bands creating large variation. Finally, we consider a semiconducting case of a solid-electrolyte interphase (SEI) consisting of LiF and Li$_2$CO$_3$ and note the importance of the Fermi level at the interface, pinned by the redox reaction occuring there. We identify the asymmetry in reaction rates as a function of discharge/charge naturally within this approach. The analysis code used in this work is available open-source on Github.