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Title: Crashworthiness Models for Automotive Batteries - Report on Project 2088-A031-15 for DOT/NHTSA

Abstract

Safety is a key element of any device designed to store energy, in particular electrochemical batteries, which convert energy of chemical reactions to electrical energy. Safety considerations are especially important when applied to large automotive batteries designed for propulsion of electric vehicles (EV). The high amount of energy stored in EV battery packs translates to higher probability of fire in case of severe deformation of battery compartment due to automotive crash or impact caused by road debris. While such demand for safety has resulted in heavier protection of battery enclosure, the mechanisms leading to internal short circuit due to deformation of the battery are not well understood even on the level of a single electrochemical cell. Moreover, not all internal shorts result in thermal runaway, and thus a criterion for catastrophic failure needs to be developed. This report summarizes the effort to pinpoint the critical deformation necessary to trigger a short via experimental study on large format automotive Li-ion cells in a rigid spherical indentation configuration. Cases of single cells and cell stacks undergoing indentation were investigated. Mechanical properties of cell components were determined via experimental testing and served as input for constitutive models of Finite Element (FE) analysis. Themore » ability of the model to predict the behavior of cell(s) under spherical indentation and to predict failure leading to internal short circuit was validated against experiments. The necessity of resolving pairs of negative and positive electrodes in the FE formulation is clearly demonstrated by comparing layer-resolved simulations with simulations involving batteries with homogenized material properties. Finally, a coupled solution of electrochemical-electrical-thermal (EET) problem on a Nissan Leaf battery module was demonstrated towards the goal of extending the simulations to module level.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1337031
Report Number(s):
ORNL/TM-2016/435
453040170
DOE Contract Number:
AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE

Citation Formats

Kalnaus, Sergiy, Kumar, Abhishek, Lebrun-Grandie, Damien T., Simunovic, Srdjan, Slattery, Stuart R., Turner, John A., Wang, Hsin, Allu, Srikanth, Gorti, Sarma B., and Turcksin, Bruno R. Crashworthiness Models for Automotive Batteries - Report on Project 2088-A031-15 for DOT/NHTSA. United States: N. p., 2016. Web. doi:10.2172/1337031.
Kalnaus, Sergiy, Kumar, Abhishek, Lebrun-Grandie, Damien T., Simunovic, Srdjan, Slattery, Stuart R., Turner, John A., Wang, Hsin, Allu, Srikanth, Gorti, Sarma B., & Turcksin, Bruno R. Crashworthiness Models for Automotive Batteries - Report on Project 2088-A031-15 for DOT/NHTSA. United States. doi:10.2172/1337031.
Kalnaus, Sergiy, Kumar, Abhishek, Lebrun-Grandie, Damien T., Simunovic, Srdjan, Slattery, Stuart R., Turner, John A., Wang, Hsin, Allu, Srikanth, Gorti, Sarma B., and Turcksin, Bruno R. 2016. "Crashworthiness Models for Automotive Batteries - Report on Project 2088-A031-15 for DOT/NHTSA". United States. doi:10.2172/1337031. https://www.osti.gov/servlets/purl/1337031.
@article{osti_1337031,
title = {Crashworthiness Models for Automotive Batteries - Report on Project 2088-A031-15 for DOT/NHTSA},
author = {Kalnaus, Sergiy and Kumar, Abhishek and Lebrun-Grandie, Damien T. and Simunovic, Srdjan and Slattery, Stuart R. and Turner, John A. and Wang, Hsin and Allu, Srikanth and Gorti, Sarma B. and Turcksin, Bruno R.},
abstractNote = {Safety is a key element of any device designed to store energy, in particular electrochemical batteries, which convert energy of chemical reactions to electrical energy. Safety considerations are especially important when applied to large automotive batteries designed for propulsion of electric vehicles (EV). The high amount of energy stored in EV battery packs translates to higher probability of fire in case of severe deformation of battery compartment due to automotive crash or impact caused by road debris. While such demand for safety has resulted in heavier protection of battery enclosure, the mechanisms leading to internal short circuit due to deformation of the battery are not well understood even on the level of a single electrochemical cell. Moreover, not all internal shorts result in thermal runaway, and thus a criterion for catastrophic failure needs to be developed. This report summarizes the effort to pinpoint the critical deformation necessary to trigger a short via experimental study on large format automotive Li-ion cells in a rigid spherical indentation configuration. Cases of single cells and cell stacks undergoing indentation were investigated. Mechanical properties of cell components were determined via experimental testing and served as input for constitutive models of Finite Element (FE) analysis. The ability of the model to predict the behavior of cell(s) under spherical indentation and to predict failure leading to internal short circuit was validated against experiments. The necessity of resolving pairs of negative and positive electrodes in the FE formulation is clearly demonstrated by comparing layer-resolved simulations with simulations involving batteries with homogenized material properties. Finally, a coupled solution of electrochemical-electrical-thermal (EET) problem on a Nissan Leaf battery module was demonstrated towards the goal of extending the simulations to module level.},
doi = {10.2172/1337031},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7
}

Technical Report:

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  • Safety is a critical aspect of lithium-ion (Li-ion) battery design. Impact/crash conditions can trigger a complex interplay of mechanical contact, heat generation and electrical discharge, which can result in adverse thermal events. The cause of these thermal events has been linked to internal contact between the opposite electrodes, i.e. internal short circuit. The severity of the outcome is influenced by the configuration of the internal short circuit and the battery state. Different loading conditions and battery states may lead to micro (soft) shorts where material burnout due to generated heat eliminates contact between the electrodes, or persistent (hard) shorts whichmore » can lead to more significant thermal events and potentially damage the entire battery system and beyond. Experimental characterization of individual battery components for the onset of internal shorts is limited, since it is impractical to canvas all possible variations in battery state of charge, operating conditions, and impact loading in a timely manner. This report provides a survey of modeling and simulation approaches and documents a project initiated and funded by DOT/NHTSA to improve modeling and simulation capabilities in order to design tests that provide leading indicators of failure in batteries. In this project, ORNL has demonstrated a computational infrastructure to conduct impact simulations of Li-ion batteries using models that resolve internal structures and electro-thermo-chemical and mechanical conditions. Initial comparisons to abuse experiments on cells and cell strings conducted at ORNL and Naval Surface Warfare Center (NSWC) at Carderock MD for parameter estimation and model validation have been performed. This research has provided insight into the mechanisms of deformation in batteries (both at cell and electrode level) and their relationship to the safety of batteries.« less
  • As automotive fuel economy requirements increase, the push for reducing overall vehicle weight will likely include the consideration of materials that have not previously been part of mainstream vehicle design and manufacturing, including carbon fiber composites. Vehicle manufacturers currently rely on computer-aided engineering (CAE) methods as part of the design and development process, so going forward, the ability to accurately and predictably model carbon fiber composites will be necessary. If composites are to be used for structural components, this need applies to both, crash and quasi-static modeling. This final report covers the results of a five-year, $6.89M, 50% cost-shared researchmore » project between Department of Energy (DOE) and the US Advanced Materials Partnership (USAMP) under Cooperative Agreement DE-EE-0005661 known as “Validation of Material Models for Automotive Carbon Fiber Composite Structures Via Physical and Crash Testing (VMM).” The objective of the VMM Composites Project was to validate and assess the ability of physics-based material models to predict crash performance of automotive primary load-carrying carbon fiber composite structures. Simulation material models that were evaluated included micro-mechanics based meso-scale models developed by the University of Michigan (UM) and micro-plane models by Northwestern University (NWU) under previous collaborations with the DOE and Automotive Composites Consortium/USAMP, as well as five commercial crash codes: LS-DYNA, RADIOSS, VPS/PAM-CRASH, Abaqus, and GENOA-MCQ. CAE predictions obtained from seven organizations were compared with experimental results from quasi-static testing and dynamic crash testing of a thermoset carbon fiber composite front-bumper and crush-can (FBCC) system gathered under multiple loading conditions. This FBCC design was developed to demonstrate progressive crush, virtual simulation, tooling, fabrication, assembly, non-destructive evaluation and crash testing advances in order to assess the correlation of the predicted results to the physical tests. The FBCC was developed to meet a goal of 30-35% mass reduction while aiming for equivalent energy absorption as a steel component for which baseline experimental results were obtained from testing in the same crash modes. The project also evaluated crash performance of thermoplastic composite structures fabricated from commercial prepreg materials and low cost carbon fiber sourced from Oak Ridge National Laboratory. The VMM Project determined that no set of predictions from a CAE supplier were found to be universally accurate among all the six crash modes evaluated. In general, crash modes that were most dependent on the properties of the prepreg were more accurate than those that were dependent on the behavior of the joints. The project found that current CAE modeling methods or best practices for carbon fiber composites have not achieved standardization, and accuracy of CAE is highly reliant on the experience of its users. Coupon tests alone are not sufficient to develop an accurate material model, but it is necessary to bridge the gap between the coupon data and performance of the actual structure with a series of subcomponent level tests. Much of the unreliability of the predictions can be attributed to shortcomings in our ability to mathematically link the effects of manufacturing and material variability into the material models. This is a subject of ongoing research in the industry. The final report is organized by key technical tasks to describe how the validation project developed, modeled and compared crash data obtained on the composite FBCC to the multiple sets of CAE predictions. Highlights of the report include a discussion of the quantitative comparison between predictions and experimental data, as well as an in-depth discussion of remaining technological gaps that exist in the industry, which are intended to spur innovations and improvements in CAE technology.« less
  • Lithium-water-air (Li-H/sub 2/O-air) cells with electrode areas of 500 cm/sup 2/ were discharged in an acrylic cell casing designed specifically for this purpose. Numerous cells were discharged in lithium hydroxide (LiOH) electrolyte at an electrolyte temperature near 25/sup 0/C. Power output was regulated by controlling the LiOH concentration in the electrolyte. The cells were normally discharged at voltages from 2.0 to 2.3 V and current densities ranging from 50 to 200 mA/cm/sup 2/. The design power density of 0.4 W/cm/sup 2/ was achieved at Li current efficiencies near 90 percent by the conclusion of the test program. The Li-H/sub 2/O-airmore » electrochemical couple does not appear to exhibit any significant scaling factor in regard to either electrode area or the number of cells in the battery. A detailed investigation was carried out to determine the applicability of the aluminum-water-air (Al-H/sub 2/O-air) cell concept as a power source for automotive propulsion. The characteristics of various candidate Al alloys were determined in both laboratory half-cell corrosion studies and full-cell discharge studies. Examination of the effect of variations in operational parameters of a subscale 50-cm/sup 2/ cell was accomplished, and the critical parameters were identified. Evaluation of candidate air cathodes from several sources was undertaken. Cathodes from only two sources were found to have adequate polarization characteristics; of these, only one possessed the durability desired for automotive applications. For a full cell, peak power density of 378 mW/cm/sup 2/ at 425 mA/cm/sup 2/ was obtained. At a nominal useful voltage of 1.3 V, the power density was 230 mW/cm/sup 2/ at 175 mA/cm/sup 2/. Coulombic efficiencies of 90 percent were obtained. 48 figures, 9 tables.« less
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  • The bibliography contains citations concerning the design, manufacture, and marketing of automotive batteries. Included are nickel-cadmium, nickel metal hydride, sodium sulfur, zinc-air, lead-acid, and polymer batteries. Testing includes life-cycling, performance and peak-power characteristics, and vehicle testing of near-term batteries. Also mentioned are measurement equipment, European batteries, and electric vehicle battery development. (Contains a minimum of 76 citations and includes a subject term index and title list.)