Multiphysics Modelling of Micromechanical Degradation in Lithium-Ion Batteries
Time: Fri 2025-11-21 09.00
Location: Kollegiesalen, Brinellvägen 8, Stockholm
Video link: https://kth-se.zoom.us/j/64018994876
Language: English
Subject area: Solid Mechanics
Doctoral student: Vinit Nagda , Material- och strukturmekanik
Opponent: Professor Javier Segurado, IMDEA Materials Institute, Spanien
Supervisor: Artem Kulachenko, Material- och strukturmekanik
QC 251105
Abstract
Lithium-ion batteries play a crucial role in the global transition toward clean transportation and the integration of renewable energy sources. In this transition, Ni-rich layered positive electrodes are regarded as leading candidates for next-generation high-energy lithium-ion batteries because of their high specific capacity. However, their widespread deployment is limited by an insufficient understanding of mechanical degradation, which governs performance loss and cycle life. Addressing this knowledge gap is essential for enabling reliable and durable lithium-ion batteries in future energy systems.
Lithium-ion batteries are inherently complex systems where electrochemical, mechanical, and transport processes are strongly coupled, posing significant challenges for accurate modelling and prediction. This thesis presents a comprehensive investigation into the mechanical degradation behaviour of lithium-ion battery positive electrodes, employing advanced computational modelling to bridge microstructural features with macroscopic performance. In Paper A, a novel workflow combining deep learning-based image segmentation, spherical harmonics, and a Copula model is introduced for generating statistically equivalent 3D electrode digital twins, enabling high-fidelity simulations.
In Paper B, the high-fidelity particle-scale simulations reveal that particle cracking, primarily driven by anisotropic deformation at grain boundaries, significantly impacts electrochemical performance. The simulation reveals that particle cracking can occur as early as the first charging cycle, and even at low C-rates. Crucially, Paper C, focusing on 3D electro-chemo-mechanical models, uncovered that the counterintuitive volumetric expansion of secondary particles post-cracking stems from the release of manufacturing-induced residual stresses, while ruling out alternative hypotheses such as dynamic cracking, CEI growth, and capillary pressure effects. Furthermore, explicitly modelling the carbon-binder domain in Paper D demonstrated that particle-binder interfacial delamination is the dominant mechanical failure mode, critically disrupting electronic connectivity and accelerating capacity loss.
These findings underscore the indispensable role of high-fidelity, microstructure-informed computational tools in accurately predicting degradation and its impact on performance. The work provides a clear roadmap for designing durable, high-energy positive electrodes by using single-crystal active particles and optimizing electrode processing and binder morphology.