A model for SEI-growth based on non-equilibrium thermodynamics
Authors
- Landstorfer, Manuel
ORCID: 0000-0002-0565-2601 - Pohl, Christoph
- Brosa Planella, Ferran
- Manmi, Kawa
2020 Mathematics Subject Classification
- 78A57 35Q92 80A22 35R37 74A15
Keywords
- Battery modelling, moving interface, solid electrolyte interphase, non-equilibrium thermodynamics, electrochemistry
DOI
Abstract
The growth of the solid electrolyte interphase (SEI) is a dominant degradation mechanism in lithium-ion batteries, governing capacity fade, coulombic efficiency, and long-term performance. Despite extensive experimental investigation, quantitative understanding of SEI formation and evolution remains limited by its nanoscale thickness, complex chemistry, and strong sensitivity to operating conditions. Existing zero-dimensional models capture individual rate-limiting mechanisms but typically treat the SEI as an idealized interface layer, neglecting spatially resolved transport, solvent consumption, and dynamic interface motion. In this work, we present a continuum-level model for SEI growth grounded in non-equilibrium thermodynamics. The SEI is treated as a distinct thermodynamic domain and modeled as a mixed ion - electron conductor, while the SEI - electrolyte interface is described as a moving boundary. The framework systematically derives transport laws and reaction kinetics from electrochemical poten- tials and interfacial free energies, ensuring thermodynamic consistency. A finite electrolyte reservoir is explicitly included, allowing solvent depletion to emerge naturally as a limiting mechanism for SEI growth. The general formulation consists of coupled partial differential equations for all domains and interfaces. Under open-circuit voltage conditions, the system reduces to a tractable set of ordinary differential equations describing lithium concentration in the active material, solvent concentration, and SEI thickness. Numerical simulations under charging, rest, and cycling conditions reproduce experimentally observed features such as linear and square root of time growth regimes, voltage shifts due to parasitic current consumption, capacity contributions from lithium stored in the SEI, and self- discharge during rest. Two distinct termination mechanisms - active lithium depletion and solvent exhaustion - are identified. Overall, the proposed framework unifies multiple SEI growth mechanisms within a single thermodynamically consistent model and provides a mechanistic basis for improved lifetime prediction and optimization of battery formation and operating protocols.
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