Energies

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18 pages, 12110 KiB

Open AccessArticle

Multiscale Analysis and Safety Assessment of Fresh and Electrical Aged Lithium-Ion Pouch Cells Focusing on Mechanical Behavior

by Marvin Sprenger, Norbert Dölle, Florian Schauwecker, Marco Raffler, Christian Ellersdorfer and Wolfgang Sinz

Energies 2022, 15(3), 847; https://doi.org/10.3390/en15030847 - 24 Jan 2022

Cited by 12 | Viewed by 3937

Abstract

Analyzing the impact of electrical aging on the lithium-ion cell’s mechanical behavior and safety is an important factor to assess the crash safety of electric vehicles during their lifetime. In this study, fresh and electrical aged state-of-the-art NCM pouch cells were investigated. Aged [...] Read more.

Analyzing the impact of electrical aging on the lithium-ion cell’s mechanical behavior and safety is an important factor to assess the crash safety of electric vehicles during their lifetime. In this study, fresh and electrical aged state-of-the-art NCM pouch cells were investigated. Aged cells, which were cycled electrically to 90% state of health, under laboratory conditions in electric vehicle battery modules were used. The used charging/discharging strategy represents real customer behavior based on accelerated driving profiles. First, it is shown that electrical aging has a significant influence on the anodes’ and separators’ mechanical properties, which had a lower mechanical strength and stiffness under tension. Additionally, quasi-static cylindrical indentation and three-point bending tests were performed to investigate aging effects on cell level at varying state of charge (SOC). Aged cells with 0% SOC showed a right-shifted force–displacement curve and a 29% lower maximum force compared to fresh cells. Fully charged, aged cells reached a similar maximum force to fresh cells, but faster temperature increase and higher temperature peaks after internal short circuit. Inductively coupled plasma optical emission spectrometry analyses confirmed an increased lithium content on the anode surface, which is indicated in literature as a reason for the increased exothermic reaction of the aged cells. The results indicate a higher safety risk for the aged investigated pouch cells under mechanical loads based on their changed mechanical properties and thermal runaway behavior. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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17 pages, 8317 KiB

Open AccessFeature PaperArticle

A Material Model for the Orthotropic and Viscous Behavior of Separators in Lithium-Ion Batteries under High Mechanical Loads

by Marian Bulla, Stefan Kolling and Elham Sahraei

Energies 2021, 14(15), 4585; https://doi.org/10.3390/en14154585 - 29 Jul 2021

Cited by 10 | Viewed by 2090

Abstract

The present study is focused on the development of a material model where the orthotropic-visco-elastic and orthotropic-visco-plastic mechanical behavior of a polymeric material is considered. The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage [...] Read more.

The present study is focused on the development of a material model where the orthotropic-visco-elastic and orthotropic-visco-plastic mechanical behavior of a polymeric material is considered. The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage of electric powered drive systems using Lithium-ion (Li-ion) batteries. For the safety and crashworthiness investigations, a deeper understanding of the mechanical behavior under high and dynamic loads is needed. In order to prevent internal short circuits and thermal runaways within a Li-ion battery, the separator plays a crucial role. Based on results of material tests, a novel material model for finite element analysis (FEA) is developed using the explicit solver Altair Radioss. Based on this model, the visco-elastic-orthotropic, as well as the visco-plastic-orthotropic, behavior until failure can be modeled. Finally, a FE simulation model of the separator material is performed, using the results of different tensile tests conducted at three different velocities, 0.1 mm·s⁻¹, 1.0 mm·s⁻¹ and 10.0 mm·s⁻¹ and different orientations of the specimen. The purpose is to predict the anisotropic, rate-dependent stiffness behavior of separator materials in order to improve FE simulations of the mechanical behavior of batteries and therefore reduce the development time of electrically powered vehicles and consumer goods. The present novel material model in combination with a well-suited failure criterion, which considers the different states of stress and anisotropic-visco-dependent failure limits, can be applied for crashworthiness FE analysis. The model succeeded in predicting anisotropic, visco-elastic orthotropic and visco-plastic orthotropic stiffness behavior up to failure. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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15 pages, 58733 KiB

Open AccessArticle

Extending a Homogenized Model for Characterizing Multidirectional Jellyroll Failure in Prismatic Lithium-Ion Batteries

by Lingxiao Zhu, Yong Xia, Yuanjie Liu, Yulong Ge, Lin Wang and Lei Zhang

Energies 2021, 14(12), 3444; https://doi.org/10.3390/en14123444 - 10 Jun 2021

Cited by 11 | Viewed by 2725

Abstract

Lithium-ion batteries have been widely used in electric vehicles but may cause severe internal short circuit during extreme intrusion-type accidents. A well-defined homogenized model of battery or jellyroll is necessary for safety assessment and design on large-scale structure level. In our previous study, [...] Read more.

Lithium-ion batteries have been widely used in electric vehicles but may cause severe internal short circuit during extreme intrusion-type accidents. A well-defined homogenized model of battery or jellyroll is necessary for safety assessment and design on large-scale structure level. In our previous study, the jellyroll of prismatic lithium-ion battery cell shows anisotropic mechanical behavior and failure tolerance. For homogenized characterization of jellyroll, in the present paper, the user subroutine of a constitutive model taking anisotropy into account is implanted into Abaqus finite element analysis software, which is capable of capturing the force versus displacement responses along different loading directions before jellyroll failure. To extend the capability of the homogenized model, five single-parameter failure criteria and two combined failure criteria are examined in predicting the failure onsets in jellyroll along different directions. The result proves the combined failure criteria is competent to correctly predict the multidirectional failure onsets compared with the single-parameter ones. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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18 pages, 7442 KiB

Open AccessArticle

Evaluation of Modelling and Simulation Strategies to Investigate the Mechanical Integrity of a Battery Cell Using Finite Element Methods

by Shraddha Suhas Kulkarni, Filip Vysoudil and Thomas Vietor

Energies 2021, 14(11), 2976; https://doi.org/10.3390/en14112976 - 21 May 2021

Viewed by 3530

Abstract

The mechanical integrity of a lithium ion battery cell can be evaluated using finite element (FE) simulation techniques. In this study, different FE modelling approaches including heterogeneous, homogeneous, hybrid and sandwich methods are presented and analysed. The basic capabilities of the FE-methods and [...] Read more.

The mechanical integrity of a lithium ion battery cell can be evaluated using finite element (FE) simulation techniques. In this study, different FE modelling approaches including heterogeneous, homogeneous, hybrid and sandwich methods are presented and analysed. The basic capabilities of the FE-methods and their suitability to simulate a real mechanical safety test procedures on battery cells are investigated by performing a simulation of a spherical indentation test on a sample pouch cell. For each modelling approach, one battery cell model was created. In order to observe the system behaviour, relevant parametric studies involving coefficient of friction and failure strain of separator were performed. This studied showed that these parameters can influence the maximum force and the point of failure of the cell. Furthermore, the influence of an anisotropic separator on the results was also investigated. The advantages and disadvantages of each modelling approach are discussed and a simplified approach with a partial cell modelling is suggested to further reduce the simulation time and complexity. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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24 pages, 13798 KiB

Open AccessArticle

Numerical Modeling and Safety Design for Lithium-Ion Vehicle Battery Modules Subject to Crush Loading

by Feng Zhu, Runzhou Zhou and David J. Sypeck

Energies 2021, 14(1), 118; https://doi.org/10.3390/en14010118 - 28 Dec 2020

Cited by 11 | Viewed by 2775

Abstract

In this work, a computational study was carried out to simulate crushing tests on lithium-ion vehicle battery modules. The tests were performed on commercial battery modules subject to wedge cutting at low speeds. Based on loading and boundary conditions in the tests, finite [...] Read more.

In this work, a computational study was carried out to simulate crushing tests on lithium-ion vehicle battery modules. The tests were performed on commercial battery modules subject to wedge cutting at low speeds. Based on loading and boundary conditions in the tests, finite element (FE) models were developed using explicit FEA code LS-DYNA. The model predictions demonstrated a good agreement in terms of structural failure modes and force–displacement responses at both cell and module levels. The model was extended to study additional loading conditions such as indentation by a cylinder and a rectangular block. The effect of other module components such as the cover and cooling plates was analyzed, and the results have the potential for improving battery module safety design. Based on the detailed FE model, to reduce its computational cost, a simplified model was developed by representing the battery module with a homogeneous material law. Then, all three scenarios were simulated, and the results show that this simplified model can reasonably predict the short circuit initiation of the battery module. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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20 pages, 5599 KiB

Open AccessArticle

Experimental and Numerical Investigation of the Behavior of Automotive Battery Busbars under Varying Mechanical Loads

by Tobias Werling, Marvin Sprenger, Christian Ellersdorfer and Wolfgang Sinz

Energies 2020, 13(24), 6572; https://doi.org/10.3390/en13246572 - 13 Dec 2020

Cited by 4 | Viewed by 3079

Abstract

Automotive high-voltage busbars are critical electrical components in electric vehicle battery systems as they connect individual battery modules and form the connection to the vehicle’s powertrain. Therefore, a vehicle crash can pose a significant risk to safety by compromising busbar insulation, leading to [...] Read more.

Automotive high-voltage busbars are critical electrical components in electric vehicle battery systems as they connect individual battery modules and form the connection to the vehicle’s powertrain. Therefore, a vehicle crash can pose a significant risk to safety by compromising busbar insulation, leading to electrical short circuits inside the battery. In turn, these can trigger thermal chain reactions in the cell modules of the battery pack. In order to ensure a safe design in future applications of busbars, this study investigated the mechanical behavior of busbars and their insulation. Our results indicated that crashlike compressive and bending loads lead to complex stress states resulting in failure of busbar insulation. To estimate the safety of busbars in the early development process using finite element simulations, suitable material models were evaluated. Failure of the insulation was included in the simulation using an optimized generalized incremental stress state dependent model (GISSMO). It was shown that sophisticated polymer models do not significantly improve the simulation quality. Finally, on the basis of the experimental and numerical results, we outline some putative approaches for increasing the safety of high-voltage busbars in electric vehicles, such as choosing the insulating layer material according to the range of expected mechanical loads. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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26 pages, 11384 KiB

Open AccessArticle

Dynamic High Strain Rate Characterization of Lithium-Ion Nickel–Cobalt–Aluminum (NCA) Battery Using Split Hopkinson Tensile/Pressure Bar Methodology

by Hafiz Fadillah, Sigit Puji Santosa, Leonardo Gunawan, Akbar Afdhal and Agus Purwanto

Energies 2020, 13(19), 5061; https://doi.org/10.3390/en13195061 - 26 Sep 2020

Cited by 4 | Viewed by 2636

Abstract

The dynamic behavior of the lithium-ion battery is evaluated by simulating the full battery system and each corresponding component, including the jellyroll and thin-foil electrodes. The thin-foil electrodes were evaluated using a novel design of split Hopkinson tensile bar (SHTB), while the jellyroll [...] Read more.

The dynamic behavior of the lithium-ion battery is evaluated by simulating the full battery system and each corresponding component, including the jellyroll and thin-foil electrodes. The thin-foil electrodes were evaluated using a novel design of split Hopkinson tensile bar (SHTB), while the jellyroll was evaluated using the split Hopkinson pressure bar (SHPB). A new stacking method was employed to strengthen the stress wave signal of the thin-foil electrodes in the SHTB simulation. The characteristic of the stress–strain curve should remain the same regardless of the amount of stacking. The jellyroll dynamic properties were characterized by using the SHPB method. The jellyroll was modeled with Fu-Chang foam and modified crushable foam and compared with experimental results at the loading speeds of 20 and 30 m/s. The dynamic behavior compared very well when it was modeled with Fu-Chang foam. These studies show that the dynamic characterization of Li-ion battery components can be evaluated using tensile loading of stacked layers of thin foil aluminum and copper with SHTB methodology as well as the compressive loading of jellyroll using SHPB methodology. Finally, the dynamic performance of the full system battery can be simulated by using the dynamic properties of each component, which were evaluated using the SHTB and SHPB methodologies. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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17 pages, 5474 KiB

Open AccessArticle

An Experimental and Computational Study on the Orthotropic Failure of Separators for Lithium-Ion Batteries

by Marian Bulla, Stefan Kolling and Elham Sahraei

Energies 2020, 13(17), 4399; https://doi.org/10.3390/en13174399 - 26 Aug 2020

Cited by 18 | Viewed by 2728

Abstract

In the present study, the mechanical properties of a dry-processed polyethylene (PE) separator are investigated in terms of deformation and failure limits. The focus is set on the anisotropic mechanical behavior of this material. A deeper understanding of the damage mechanism is important [...] Read more.

In the present study, the mechanical properties of a dry-processed polyethylene (PE) separator are investigated in terms of deformation and failure limits. The focus is set on the anisotropic mechanical behavior of this material. A deeper understanding of the damage mechanism is important for further safety and crashworthiness investigations and predictions of damage before failure. It has been found that separator integrity is one of the crucial parts in preventing internal short circuit and thermal runaway in lithium-ion (Li-ion) batteries. Based on uniaxial tensile tests with local strain measurement, a novel failure criterion for finite element analysis (FEA), using the explicit FEA solver Altair Radioss, has been developed to predict the effect of high mechanical loads with respect to triaxiality, large plastic strain and orthotropy. Finally, a simulation model of a PE separator was developed combining the novel failure criterion with Hill’s yield surface and a Swift–Voce hardening rule. The model succeeded in predicting the anisotropic response of the PE separator due to deformation and failure. The proposed failure model can also be combined with other constitutive material laws. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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15 pages, 10705 KiB

Open AccessFeature PaperArticle

Electrical Response of Mechanically Damaged Lithium-Ion Batteries

by Damoon Soudbakhsh, Mehdi Gilaki, William Lynch, Peilin Zhang, Taeyoung Choi and Elham Sahraei

Energies 2020, 13(17), 4284; https://doi.org/10.3390/en13174284 - 19 Aug 2020

Cited by 16 | Viewed by 7583

Abstract

Lithium-ion batteries have found various modern applications due to their high energy density, long cycle life, and low self-discharge. However, increased use of these batteries has been accompanied by an increase in safety concerns, such as spontaneous fires or explosions due to impact [...] Read more.

Lithium-ion batteries have found various modern applications due to their high energy density, long cycle life, and low self-discharge. However, increased use of these batteries has been accompanied by an increase in safety concerns, such as spontaneous fires or explosions due to impact or indentation. Mechanical damage to a battery cell is often enough reason to discard it. However, if an Electric Vehicle is involved in a crash, there is no means to visually inspect all the cells inside a pack, sometimes consisting of thousands of cells. Furthermore, there is no documented report on how mechanical damage may change the electrical response of a cell, which in turn can be used to detect damaged cells by the battery management system (BMS). In this research, we investigated the effects of mechanical deformation on electrical responses of Lithium-ion cells to understand what parameters in electrical response can be used to detect damage where cells cannot be visually inspected. We used charge-discharge cycling data, capacity fade measurement, and Electrochemical Impedance Spectroscopy (EIS) in combination with advanced modeling techniques. Our results indicate that many cell parameters may remain unchanged under moderate indentation, which makes detection of a damaged cell a challenging task for the battery pack and BMS designers. Full article

(This article belongs to the Special Issue Crash Safety of Lithium-Ion Batteries)

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