Researchers have developed a detailed three-dimensional electro-thermo-mechanical model to identify and quantify the swelling force generated by lithium-ion batteries during charging, offering a new tool for improving battery safety at the cell and module level. The study addresses a practical problem that becomes especially important once batteries are packed into constrained assemblies: as cells expand during charging, the resulting internal pressure can alter performance, intensify mechanical stress, and contribute to safety risks if it is not properly understood and managed.
Lithium-ion batteries are rarely used as isolated cells in real applications. In electric vehicles, energy storage systems, and other high-power devices, they are usually assembled into modules and packs where surrounding structures mechanically constrain their expansion. Under those conditions, charging-induced volume change does not simply lead to harmless swelling. Instead, it can generate substantial internal pressure and contact force within the battery pack. That pressure evolution matters because it can affect electrochemical behavior, structural integrity, and long-term reliability. Yet despite its importance, swelling force has been difficult to quantify precisely, especially in a way that links local internal processes to macroscopic force response.
The new study tackles that challenge through a multiphysics coupling framework. The researchers developed a three-dimensional electrochemical-thermal-mechanical coupled model that incorporates the actual layered structure of a lithium-ion battery. This is important because stress and deformation do not emerge uniformly throughout a cell. Different layers respond differently as lithiation progresses, and a simplified model can miss the spatial variations that shape overall force generation. By combining electrochemical, thermal, and mechanical effects in one framework, the model is able not only to predict battery swelling force over time, but also to visualize stress distribution and deformation patterns across the layered architecture.
According to the paper, the model was rigorously validated against experimental data, which is a key strength of the work. A physically rich model is only useful for engineering practice if its predictions hold up under real measurements. The study reports that the framework can accurately identify and quantify swelling force during the charging process. That means the model is not merely descriptive in a qualitative sense. Instead, it offers a quantitative route to understanding when swelling force rises, how it evolves, and where within the battery the underlying stress and strain fields are developing.
One of the study's more interesting findings concerns a turning point in the swelling-force curve. The researchers report that this turning point coincides with the moment when the lithiation rate at position P3 increases significantly compared with other positions. In other words, the macroscopic force signal is linked to a specific shift in local electrochemical behavior inside the cell. This kind of connection is valuable because it helps translate a pack-level mechanical phenomenon into layer-scale and position-specific physical causes. For engineers, that means swelling-force dynamics may be more interpretable and potentially more controllable than if they were viewed as a purely bulk mechanical response.
The paper also reveals an asymmetry between cathode and anode behavior at the end of charging. Because the active materials in the cathode and anode have different Young's moduli, the cathode shows the maximum stress but minimum strain, while the anode exhibits the opposite trend. That finding underscores why battery swelling cannot be understood simply by asking where deformation is largest. Stress and strain distribute differently depending on material stiffness and electrochemical state, and those distinctions matter for structural design, constraint strategy, and failure prevention.
The broader significance of the work lies in battery safety enhancement through better structural and assembly design. If swelling force can be identified accurately and linked to internal lithiation dynamics, module designers may be better equipped to determine how much mechanical constraint a battery can safely tolerate and where structural reinforcement or compliance is most needed. This is especially relevant for tightly packaged battery systems, where mechanical pressure can accumulate across many cells and potentially influence aging, local damage, or safety-critical failure pathways.
Further work will still be needed to extend the framework to additional cell formats, chemistries, and pack-level operating conditions. But the study provides a compelling example of how in-situ quantification and multiphysics modeling can work together to improve safety understanding. Rather than treating battery swelling as a secondary side effect of charging, the paper frames swelling force as a measurable, interpretable, and design-relevant variable. For lithium-ion battery systems operating under real mechanical constraints, that perspective could become increasingly important as energy density and packaging complexity continue to rise.
Reference
Author:
Quanqing Yu a b , Liubin Fan a , Huanyong Deng a , Donglin Fang a , Can Wang a b
Title of original paper:
Li-Ion Battery Swelling Force: Multiphysics Coupling Modeling and In-Situ Quantification for Safety Enhancement
Article link:
https://www.sciencedirect.com/science/article/pii/S2773153725001343
Journal:
Green Energy and Intelligent Transportation
DOI:
10.1016/j.geits.2025.100384
Affiliations:
a School of Automotive Engineering, Harbin Institute of Technology, Weihai, Shandong 264209, China
b School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
Experimental study
Not applicable
4-Mar-2026