Mechanical internal short circuit (ISC) is one of the significant safety issues in lithium-ion battery design. As a result, it is possible to subject LIB cells to thorough mechanical abuse tests to determine when and why failure may occur. The indentation test is a recommended loading condition for evaluating mechanical damage and ISC. In this study, 18,650 cylindrical battery cells underwent indentation tests and a voltage reduction following the peak force identified by the ISC. Due to the complexity of the contact surface shape between two cylinders (LIB cell and indenter), a new phenomenological analytical model is proposed to measure the projected contact area, which the FEM model confirms. Moreover, the stress-strain curve and Young’s modulus reduction were calculated from the load-depth data. In contrast to previously published models, the model developed in this paper assumes anisotropic hyperelasticity (the transversely isotropic case) and predicts the growing load-carrying capacity (scalar damage), whose variation is regulated by the Caputo-Almeida fractional derivative.

The crashworthiness of electric vehicles depends on the response of lithium-ion cells to significant deformation and high strain rates. This study thoroughly explores the mechanical behavior due to damage of lithium-ion battery (LIB) cells, focusing on Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Iron Phosphate (LFP) types during both quasi-static indentation and dynamic high-velocity penetration tests. Employing a novel approach, a hemispherical indenter addresses gaps in stress–strain data for pouch cells, considering crucial factors like strain rate/load rate and battery cell type. In the finite element method (FEM) analysis, the mechanical response is investigated in two stages. First, a viscoplastic model is developed in Abaqus/Standard to predict the indentation test. Subsequently, a thermomechanical model is formulated to predict the high-speed-impact penetration test. Considering the high plastic strain rate of the LIB cell, adiabatic heating effects are incorporated into this model, eliminating heat conduction between elements. Addressing a notable discrepancy from prior research, this work explores the substantial reduction in force observed when transitioning from a single cell to a stack of two cells. The study aims to unveil the underlying reasons and provide insights into the mechanical behavior of stacked cells.

The microstructure and mechanical hardness of Inconel 718 (INC718) hexagonal honeycomb cellular structure manufactured by Selective Laser Melting (SLM) was studied in this work. Non-heat-treated SLM-produced samples with cell wall thicknesses of 0.4, 0.6 and 0.8 mm were studied. The hardness was measured using MTS Nanoindenter. For room temperature, continuous hardness measurements over penetration depths up to 2 µm under three different strain rates of 0.02, 0.05 and 0.08 s⁻¹ was performed. For the 100 and 200°C, single hardness measurements at eight different depths were performed. The grain size was found to change considerably as the cell wall thickness changed from 0.6 mm to 0.4 mm compared to the change from 0.8 mm to 0.6 mm. similar trend in mechanical hardness reduction and strain rate sensitivity changes were observed between the three samples. The microstructure and hardness showed anisotropy between the planes parallel and perpendicular to the build planes as well. Temperature and strain rate indentation size effect model developed by the second author was modified and used to evaluate the intrinsic material length scale used in gradient plasticity theory.