Semi-analytical finite element modelling of wave dispersion in pouch batteries

Ultrasonic guided waves provide a promising method for the non-invasive assessment of lithium-ion batteries (LiBs), yet their interpretation remains challenging in pouch cells because wave dispersion is governed by strongly coupled effects of multi-layered architecture, porous electrode microstructure, electrolyte participation, and manufacturing-induced anisotropy. This study proposes a component-wise parameterisation framework for guided wave simulation in LiBs, explicitly accounting for constituent composition, calendering-induced anisotropy in electrode layers, and fluid-phase behaviour. A hybrid Voigt–Reuss–Hill (VRH) and Gibson–Ashby homogenisation strategy is employed to derive effective material properties, while pore conditions are introduced to represent the strong permeability contrast among LiB components within a Biot-type formulation. Based on this framework, a semi-analytical finite element (SAFE) model incorporating Biot poroelastic theory is developed to predict dispersion characteristics, while a transient poroelastic finite element (FE) model is used to simulate wave propagation. Frequency–wavenumber spectra obtained from finite element simulations and laser vibrometer measurements show close agreement with the SAFE-predicted fundamental antisymmetric and symmetric guided wave modes (A 0 and S 0 ) in the low-frequency regime of 100–300 kHz, with relative discrepancies below 4%. The proposed SAFE–FE framework provides a physically grounded and experimentally validated pathway for modelling guided wave behaviour in complex battery architectures, supporting future ultrasonic diagnostics and structural characterisation of lithium-ion pouch cells.