Progressive mechanical indentation of large-format Li-ion cells

Abstract

Large format Li-ion cells were used to study the mechanical responses of single cells of thickness 6.5 mmand stacks of three cells under compressive loading. Various sequences of increasingdepth indentations were carried out using a 1.0 inch (25.4 mm) diameter steel ball with steel plate as a rigid support surface. The indentation depths were between 0.025" and 0.250" with main indentation increments tests of 0.025" steps. Increment steps of 0.100" and 0.005" were used to pinpoint the onset of internal-short that occurred between 0.245" and 0.250". The indented cells were disassembled and inspected for internal damage. Load vs. timecurves were compared with the developed computer models. Separator thinning leading to the short circuit was simulated using both isotropic and anisotropic mechanical properties. Our study show that separators behave differently when tested as a single layer vs. a stack in a typical pouch cell. The collective responses of the multiple layersmust be taken into account in failure analysis. A model that resolves the details of the individual internal cell components was able to simulate the internal deformation of the large format cells and the onset of failure assumed to coincide with the onset of internal short circuit.

Review: Characterization and Modeling of the Mechanical Properties of Lithium-Ion Batteries

“…Wang et al reported on spherical indentation tests on commercially available large NMC/graphite pouch cells (SOC = 25% and 75%) [40]. A steel ball (25.4 mm in diameter) was used to indent single cells as well as stack of three cells in a progressive manner at indentation depths between 0.635 mm (0.025") to 6.35 mm (0.25") in increments of 0.635 mm.…”

“…This can be done by considering cells as a homogenous material and ignoring their interior layered structure, or by more detailed analysis of evaluating the interactions of the layers that create a deformation at the cell level [9,33,[34][35][36][37][38]. The last step will be considering the problem in hand at the system level, which includes stacks of cells, modules of batteries, and finally battery packs inside a vehicle [39][40][41][42][43][44]. This review is focused on mechanical characterization and modeling efforts at the cell level.…”

Resistance exterior force property of lithium‐ion pouch batteries with different positive materials

“…The electrochemical property and resistance exterior force property of LIPB under exterior loading were investigated by many researchers . According to electrochemical and thermal coupled model, the thermal runaway and temperature distribution of LIPB under exterior loading were obtained by experiment .…”

“…The electrochemical property and resistance exterior force property of LIPB under exterior loading were investigated by many researchers. [15][16][17][18][19][20][21][22][23] According to electrochemical and thermal coupled model, the thermal runaway and temperature distribution of LIPB under exterior loading were obtained by experiment. [11][12][13] In addition, the mechanical property and ISC under quasi-state loading and dynamic impacting were investigated experimentally, 10,[22][23][24][25][26][27][28] and the results concluded that mechanical property and ISC played an important role in the failure analysis of LIPB.…”

The indentation analysis triggering internal short circuit of lithium-ion pouch battery based on shape function theory

“…The homogenized crushable foam model was an extension model developed by Deshpande and Fleck . The mechanical properties and short circuit of LIPB under different loading conditions were investigated by Sahraei et al, Kumar et al, and Wang et al numerically and experimentally. The results demonstrated that numerical model of homogenized crushable sandwich foam could predict load‐displacement relationship and deformation profile successfully.…”