Temperature, strain-rate and charge dependent mechanical response of Li-ion pouch cells

• Response of pouch Li-ion cells varies strongly with temperature and strain rate. • High temperatures soften cells, reducing load and indentation depth to failure. • Strain rate effects are complex, impacting yield stress and hardening differently. • State of Charge has minor effect, with max. 13 % reduction in peak indentation force. • Formulated surrogate model of jellystacks for large scale FE analysis. A combined experimental-numerical investigation is carried out on the mechanical response of commercial 4 Ah Li-ion pouch cells. Hemispherical indentations were performed across a broad range of conditions, including temperatures from –5 °C to 70 °C, strain rates from 0.001 s⁻¹ to 1000 s⁻¹, and states of charge (SoC) from 0.0 to 0.97. The experiments demonstrate that temperature and strain rate are the dominant factors influencing cell behavior, with higher temperatures leading to pronounced softening (43 % reduction in maximum force from 20 °C to 70 °C). The strain rate dependency is non-monotonic, with a 50 %-reduction in short-circuit displacement from slow to high speed and a 15 % reduction in maximum force from slow to intermediate speed. The influence of the SoC on the mechanical response is comparatively minor. To capture all these effects, a phenomenological constitutive model is proposed. It employs a pressure-sensitive Deshpande–Fleck yield surface with associated plastic flow and incorporates a convex-to-linear hardening transition modulated by temperature and SoC. Strain rate and softening effects are described in close analogy with Johnson–Cook-type of models. Finite element simulations performed with the identified surrogate model showed good agreement across all indentation experiments. The proposed model provides a robust framework for predicting the mechanical behavior of Li-ion cells under varying conditions, offering immediate applicability for the design of safer battery systems in electronic devices and vehicles.