Morphological Stability of Metal Anodes: Roles of Solid Electrolyte Interphases (SEIs) and Desolvation Kinetics

TL;DR

This paper presents a comprehensive theoretical framework that predicts morphological instabilities during lithium metal electrodeposition, emphasizing the roles of SEI properties and desolvation kinetics in stabilizing metal anodes.

Contribution

It introduces a unified model integrating ion transport, desolvation, and SEI breakdown, providing new insights into controlling electrodeposition stability.

Findings

SEI transport and desolvation rate influence reaction kinetics and stability.

Thick, poorly conductive SEIs and slow desolvation reduce limiting current.

An apparent Damköhler number helps balance reaction rates and diffusion for stability.

Abstract

Achieving stable lithium metal anodes requires control over the solid-electrolyte interphase (SEI) and desolvation kinetics. Here, we develop a unified theoretical framework integrating ion transport, desolvation, charge transfer, and SEI breakdown to predict morphological instabilities during electrodeposition. Using linear stability analysis, we identify six dimensionless parameters that govern the onset and evolution of instabilities. We show that SEI transport and desolvation rate effectively modulate apparent reaction kinetics, shifting the system toward a stable, reaction-limited regime. Extending the classical limiting current concept, we demonstrate that a thick, poorly conductive SEI and sluggish desolvation significantly reduce the limiting current. We introduce an apparent Damk\"ohler number to quantify the critical balance: suppressing diffusion-limited instabilities by reaction rate reduction, while maintaining a high limiting current. Our theory enables predictive mapping of electrodeposition morphologies across diverse materials and operating conditions, guiding the rational design of stable lithium metal anodes.