Modelling of cracks developed in lithium-ion cells under mechanical loading

Abstract

This research reports on an experimental and numerical study of material failure in the electrode assemblies (i.e. "jelly roll" and/or "electrode stack") of lithium-ion batteries after local mechanical loading. Deformed cylindrical and pouch cells (i.e. lithium-ion polymer cells) were subjected to X-ray computed tomography (CT scanning) to detect location, size, and orientation of cracks that developed in the electrode assemblies at onset of short-circuit. An experimental program was completed to acquire properties of electrode-separator micro components of electrode assemblies in tension. This data was used for calibration of an anisotropic material model. Finite element models were developed for both cell types and a maximum strain criteria was used for element failure and deletion at short circuit. The models developed here predict the location of cracks in both pouch and cylindrical cells. The finite element models corroborated the CT scan regarding location and orientation of cracks formed in the electrode assemblies. In both pouch and cylindrical cells, cracks were found to initiate perpendicular to the transverse direction of the separator. Fig. 3 Simulation of the crack through element erosion using the two models for 18650 cell. 80372 | RSC Adv., 2015, 5, 80369-80380 This journal is

Integrated computation model of lithium-ion battery subject to nail penetration

“…The equivalent strain failure e c f is determined from tension tests [17]. The values of the parameters are summarized in Table 2.…”

“…[17], and Poisson's ratio is set to m se ¼ 0:3 [39]. [17]. The selected hardening model is also the power hardening model, which is shown as follows:…”

“…The cathode is regarded as an isotropic model for nail penetration even though it is slightly anisotropic in the x 1 -x 2 direction [17]. The elastic-power hardening model [38] is chosen for modeling based on the tension test results and expressed as follows: …”

“…Young's modulus E se = 216.2 MPa is obtained from the stress-strain curve in Ref. [17], and Poisson's ratio is set to m se ¼ 0:3 [39]. [17].…”

“…First, pioneering efforts have been made to understand the mechanical behavior of LIBs that are subjected to physical abuses, e.g., radial compression [15,16], indentation [15,17], and bending [15] loads. The constitutive model for the jellyroll was first established by Greve and Fehrenbach [15] and Sahraei et al [18] through homogeneous isotropic material treatment.…”