Failure Of Lithium-ion Batteries Research Articles

Failure of Lithium-Ion Batteries Accelerated by Gravity.

The safety concerns surrounding lithium-ion batteries (LIBs) have garnered increasing attention due to their potential to endanger lives and incur significant financial losses. However, the origins of battery failures are diverse, presenting significant challenges in developing safety measures to mitigate accidental catastrophes. In this study, the aging mechanism of LiNi0.5Co0.2Mn0.3O2||graphite-based cylindrical 18,650 LIBs stored at room temperature for two years was investigated. It was found that an uneven distribution of electrolytes can be caused by gravity, leading to temperature variations within the battery. Specifically, it was observed that the temperature at the top of the battery was approximately -0.89 °C higher than at the bottom, correlating with an increase in partial internal resistance. Additionally, upon disassembly and analysis of spent batteries, the most significant damage to electrode materials at the top of the battery was observed. These findings suggest that gravity-induced electrolyte insufficiency exacerbates side reactions, particularly at the top of the battery. This study offers a unique perspective on the safety concerns associated with high-energy-density batteries in long-term and large-scale applications.

Revealing the mechanism of pack ceiling failure induced by thermal runaway in NCM batteries: A coupled multiphase fluid-structure interaction model for electric vehicles

Structure failure of lithium-ion battery (LIB) pack ceiling leads to the unintended release of combustible and poisonous substances during thermal runaway (TR), resulting in personnel injuries and financial losses. However, limited research has been conducted on the mechanism behind pack ceiling failures. In this study, we developed a coupled multiphase fluid-structure interaction (FSI) model to simulate the evolution of up-cover baffle under the TR impact of a 52 Ah NCM battery. Our findings reveal several important insights:1) the maximum force and temperature on the baffle are 13.01 N and 598.5 °C in experiment; 2) the simulation shows that particles exert higher temperature and greater force on the baffle compared to the gas phase; 3) the overall equivalent stress in the stainless-steel baffle surpasses the tensile strength that incurs crack on the baffles. According to the validated model, we find that the baffle structure failure is caused by the thermal stress from particle-structure heat conduction. Furthermore, this observation is applicable to the structure failure problems associated to the thermal runaway of high-density battery that involves enormous particles. In addition, the insulation layer is found to be more effective than the gap distance in protecting the pack ceiling. These findings offer a valuable insight into the structure design of LIB pack, and provide the guidance toward future battery integration technologies.

Performance Analysis Based on Desert Rescue UAV Power Battery in High Temperature Environment

The main purpose of this paper is to analyze and discuss the performance of the lithium iron phosphate battery and the new lithium titanate battery commonly used in UAV that affect the endurance in high temperature environment. This paper first introduces the functions of desert rescue UAV and the development status of UAV power battery technology. This paper first points out the main factors that affect their endurance at high temperature, expounds the reasons for the failure of lithium-ion batteries and high-temperature polymer batteries at high temperature, and introduces the materials and general performance characteristics of the two types of batteries, and then reviews the methods and results of various studies on the performance of lithium-ion batteries and lithium polymer batteries at high temperature. Finally, this paper points out the shortcomings of the existing research and points out the direction for the future development. By comparing the working performance of the two batteries at high temperature and combining with the practical problems that need to be considered in production and use, this paper puts forward selection suggestions according to the existing conditions, so that later workers can choose the type of UAV power battery according to different working environments.

A fast response hydrogen sensor based on the heterojunction of MXene and SnO2 nanosheets for lithium-ion battery failure detection

During the process of lithium-ion battery failure, the discharge of hydrogen indicates that the electrolyte has leaked and is being electrolyzed, which is a sign of thermal runaway in lithium batteries. In this work, stannic oxide (SnO2) nanosheets was formed by high-temperature calcination and compounded with Ti3C2Tx (MXene) in different proportions. The morphology, microstructure and element composition of the material were characterized. The sensing response of MXene-SnO2 for hydrogen (H2) at the most suitable temperature was explored. The test results show that compared with single SnO2, MXene-SnO2 composite sensor has higher response, shorter response/recovery time, stable repeatability and excellent selectivity. Finally, through density functional theory (DFT) calculation, it may be caused by the microstructure of SnO2 and MXene synergism in the effect of forming heterostructures between the two materials in response to hydrogen gas.

(Invited) Culprits or Collateral Damage? The Science behind Lithium-Ion Battery Failure Investigations

Thermal runaway failures of lithium-ion batteries have garnered a great deal of attention in recent years, including notable failures in the spaces of consumer products, electric vehicles, and energy storage systems. The growing public awareness of hazards associated with thermal runaway in lithium-ion batteries has coincided with increased scrutiny of lithium-ion batteries when they are found at fire scenes. Lithium-ion batteries can go into thermal runaway due to heating from an external fire, even if they are not the cause of the fire. As always, the fire investigator and other experts involved in the failure analysis need to remain guided by the scientific method when performing an origin and cause analysis, including when that analysis involves lithium-ion batteries.This presentation will encompass many of the tools and reasoning that may be relied upon when analyzing the role lithium-ion batteries at fire scenes, as well as in the post-scene analysis of batteries and battery-containing devices. Techniques for understanding heat release and heat release rate during thermal runaway failures will be discussed, as well as the associated literature that may be relied upon to estimate heat release based on chemistry and capacity of the cells in question. Also to be discussed are metallurgical approaches and techniques that may inform the conditions that likely existed during the failure of the battery.

Fault diagnosis of lithium-ion batteries based on voltage dip behavior

ABSTRACT In recent years, the safety accidents of new energy electric vehicles have been increasing due to the failure of lithium-ion batteries. The lithium-ion battery fault diagnosis technology is critical to ensure the safe operation of electric vehicles. In this paper, we proposes a lithium-ion battery fault diagnosis method based on voltage dip behavior. The method first uses the Sparrow Search Algorithm(SSA) to optimize the Variational Modal Decomposition(VMD), then reconstructs multiple dynamic components and extracts the multi-feature parameters of the reconstructed components, and finally uses SSA to optimize Density Based Spatial Clustering of Applications with Noise(DBSCAN) for fault diagnosis. Through verification with real vehicle data and experimental data at different temperatures, this method can be applied to the operating environment of real vehicles at different temperatures, and can quickly and accurately identify abnormal cells.

A method of lithium-ion battery failure diagnosis based on parameter boundaries of heterogeneous multi-physics aging model

Lithium-ion batteries experience capacity fading during long-term operation, and they need to be replaced when reach a certain aging degree. However, it is difficult to measure a complete charge/discharge curve to obtain the capacity whether the battery is used for vehicle or energy storage. The aging state of the battery can only be judged according to the partial data of voltage and current based on the data-driven method, which is not reliable enough. In this work, a new method of battery failure diagnosis in terms of capacity fading is proposed based on the heterogeneous multi-physics aging model of lithium-ion batteries. The key parameters are obtained by parameter identification method, and the parameter boundaries when the battery is on the verge of failure are obtained by model driven method. In practical application of batteries, the failure of batteries can be diagnosed online by monitoring the key parameters, so that an early warning signal can be provided when the battery reaches the end of its life, which is of great significance to ensure that the battery can meet the performance and safety requirements.

Experimental determination of metals generated during the thermal failure of lithium ion batteries

This work describes the deliberate failure of lithium-ion cells, and subsequent analysis of both the smoke and near field residue for the metals commonly found in battery cathodes.

Research on Overdischarge Lithium-Ion Battery Based on X-Ray Computed Tomography

Abstract Overdischarge is one of the main factors of lithium-ion battery failure, due to the inconsistency of lithium-ion battery in pack. However, the failure mechanism remains unclear. This article introduces the X-ray computed tomography (CT) to explore the gas production and copper dissolution of lithium battery during overdischarge state. From tomographic images in two different cross-sectional directions, the internal structure changes of bulge deformation and copper deposition are observed to quantitatively analyze the relationship between copper deposition and overdischarge state of charge. The position distribution is analyzed by density distribution feature, which indicate that the gas production is mainly distributed in the middle of the battery, and the copper deposition is distributed around the outer side. The experimental result shows that X-ray CT is a nondestructive, quantitative, visual, and effective way to study the internal structure and material distribution of the overdischarge battery, so as to effectively monitor the state of the lithium-ion battery, to avoid dangerous problems such as internal short circuits and thermal runaway.

Safety Characteristics of Lithium-Ion Batteries under Dynamic Impact Conditions

With the rapid development of electric vehicles, the safety accidents caused by the damage and failure of lithium-ion batteries under mechanical load are increasing gradually, which increases the significance of collision safety in lithium-ion batteries. The failure threshold of the cell in a free state is different from that of the cells in the module. Therefore, the safety characteristics of cells and modules under vertical dynamic impact conditions were studied in this paper. Lithium iron phosphate (LiFePO4) batteries and assembled 2-in-10 series modules with a 100% state of charge (SOC) were tested. Analyses included the voltage, temperature, and mechanical behavior of test samples under different impact loads, extrusion positions, and indenter shapes. The results showed that the damage behavior of a battery was closely related to the contact shape, contact area, and contact position. A smaller contact area led to greater deformation; moreover, the contact area being closer to the edge position meant greater deformation and weaker load-carrying capacity. The load-carrying capacity of the cell in a free state was weaker than that of the module, but the failure threshold of the cell in a free state was higher than that of the module. It can be concluded that the failure threshold of the cell cannot reflect the failure threshold of the module.

A Review of Lithium-Ion Battery Failure Hazards: Test Standards, Accident Analysis, and Safety Suggestions

The frequent safety accidents involving lithium-ion batteries (LIBs) have aroused widespread concern around the world. The safety standards of LIBs are of great significance in promoting usage safety, but they need to be constantly upgraded with the advancements in battery technology and the extension of the application scenarios. This study comprehensively reviews the global safety standards and regulations of LIBs, including the status, characteristics, and application scope of each standard. A standardized test for thermal runaway triggering is also introduced. The recent fire accidents in electric vehicles and energy storage power stations are discussed in relation to the upgrading of the rational test standards. Finally, the following four suggestions for improving battery safety are proposed to optimize the safety standards: (1) early warning and cloud alarms for the battery’s thermal runaway; (2) an innovative structural design for a no-fire battery pack; (3) the design of a fire water injection interface for the battery pack; (4) the design of an immersive energy storage power station. This study provides insights for promoting the effectiveness of relevant safety standards for LIBs, thereby reducing the failure hazards.

An Adaptive Noise Reduction Approach for Remaining Useful Life Prediction of Lithium-Ion Batteries

Lithium-ion batteries are widely used in the electric vehicle industry due to their recyclability and long life. However, a failure of lithium-ion batteries can cause some catastrophic accidents, such as electric car battery explosion fires and so on. To prevent such harm from occurring, it is essential to monitor the remaining useful life of lithium-ion batteries and give early warning. In this paper, an adaptive noise reduction approach is proposed to predict the RUL (Remaining Useful Life) of lithium-ion batteries, which uses CEEMDAN (Complete Ensemble Empirical Mode Decomposition with Adaptive Noise) combined with wavelet decomposition to achieve adaptive noise reduction decomposition, and then inputs the obtained IMF (Intrinsic Mode Function) components into LS–RVM (Least Square Relevance Vector Machine) for training, prediction, and reconstruction, so as to achieve high-precision prediction of RUL. Moreover, in order to verify the validity of the model, the model in this paper is compared with other common models. The results demonstrate that the RMSE, MAPE, and MAE of the proposed model are 0.008678, 0.005002, and 0.006894, and that it has higher accuracy than the other common prediction models.

In-Situ/Operando X-Ray CT Characterisation of Lithium-Ion Pouch Cells during Thermal Failure

The safety of concerns of lithium-ion batteries continues to be a prevalent obstacle toward their widespread application from vehicle electrification to space exploration. Aside from the highly oxidising and reducing electrode materials, their safety is compounded by an inherent drawback of poor heat dissipation [1]. High-speed imaging with in-situ/operando X-ray CT has been used extensively to study various lithium-ion battery safety features and failure mechanisms [2][3], including thermal failure [4]. However, these are exclusively using synchrotron X-ray sources which are limited in terms of both access and data recording capabilities: high frame rates require the data collection window to be restricted to a few seconds. During lithium-ion battery failure, there are several changes to a cell structure leading up to thermal runaway (TR) which can take minutes, and as a result are often missed. Here, we present an instrument that simulates thermal failure for lab-based radiography at slower imaging speeds and longer recording lengths, which has been validated by correlative synchrotron measurements. The failure mechanisms within a fully charged (100 % SOC, 4.2 V) commercially available LiCoO2 cathode and graphite anode pouch cell (651628-2C, AA Portable Power Corp) rated at 210 mAh are investigated.Three samples are studied using lab-based radiography at a frame rate of 3.75 fps with a 16.1 µm pixel resolution and, for comparison, an additional three samples are studied using synchrotron X-ray sources at a higher speed of 20,000 fps with a 13.3 µm pixel resolution. For the six samples investigated, the total time taken from a start temperature of 80 °C to TR is approximately 20 minutes and the onset temperatures for TR are recorded within the range of 196 °C to 210 °C. The beginning of the TR event (defined as a sample temperature increase greater than 15 °C s-1), where the effects to the electrode structure are the most catastrophic, lasts for approximately 1 s. Operando radiographic images during this event reveal that the structural displacement of electrode layers begins at the centre of the cell and propagates outwards in a wave-like motion. The electrode displacement, as a result, is quantified by cross-correlating Gabor signals and spatiotemporal mapping [5] in both types of datasets. For the lab-based radiography, data is recorded from the start temperature to TR (lasting approximately 20 minutes), and reactions such as the electrolyte decomposition, ca. 105 °C, and separator melting, ca.130 °C are characterised in the context of electrode deformation and gas evolution. Investigations of pre- and post-failure 3D X-ray CT images further verify the uniformity of the pristine (or pre-failure) cell assembly as well as the estimated post-failure behaviour between samples. Finally, by comparison with correlative synchrotron measurements, the instrument for inducing thermal failure for lab-based X-ray CT is proven to be a viable and more accessible method to investigate thermal failure within a 210 mAh pouch cell. While synchrotron data has a higher-speed imaging advantage, it is limited to only recording the short TR event at a high temporal resolution. Whereas continuous imaging in lab-based radiography has the benefit of measuring the slower architectural changes taking place up to TR, albeit at a marginally lower spatial resolution.

Prevention, Mitigation and Correlative Acoustic Spectroscopy of Lithium-Ion Battery Thermal Runaway

Scrutiny of lithium-ion battery failure has seen heavy regulations and restrictions with well-reported headlines of catastrophic thermal runaway of commercial electronic devices and electric vehicles. Thermal runaway occurs at a critical temperature when the rate of heat generation exceeds that of dissipation, highly exothermic decomposition reactions occur and temperatures in excess of 600 ᵒC can be measured 1. These concerns continue to grow with applications of greater energy density and capacity, such as the proliferation of electric vehicles.Isolation of electronically conductive components within the electrode assembly to prevent short circuit has shown promise to prevent the onset of thermal runaway within lithium-ion cells. Here 2, the authors present a metal-coated polymer current collector (PCC) and thermally stable separator (TSS) to prevent and mitigate thermal runaway. 2.10 Ah capacity 18650-geometry cells were subject to thermal, internal short circuit and nail penetration abuse techniques with these materials and their commercial counterparts for individual comparison of the PCCs and TSS. Reductions in cell mass were observed on the order of 5%, due to the majority of the PCC consisting of the polymer substrate rather than pure aluminium and copper in commercial current collectors. High speed synchrotron facilities provided insights into the function of the polymer current collectors with post- mortem X-ray computed tomography. During mitigation testing, cells were taken to failure with thermal and with an internal short circuit device (ISCD) within a Fraction Thermal Runaway Calorimeter (FTRC) to measure the reduction in calorific output. This highlighted the difficulty that exists with detecting gas-induced and internal structural degradation within lithium-ion batteries, especially outside specialized diagnostic laboratories to characterize these rapid changes with elapse within seconds. Attenuation and wave velocity determined by the propagative properties of ultrasound through different phases, prominently highlights structural, temperature and formation of different phases which occur during thermal runaway. Such analysis provided by acoustic spectroscopy are characterised by variations in the attenuation and signal peak shifts. Further information which can be derived from spatial mapping using acoustic spectroscopy 3,4 include: state of charge, state of health, electrochemical performance.Cells made with the aluminium-coated PCC demonstrated 100% success in prevention of thermal runaway during nail penetration, retaining a voltage above 4.00 V. Cells manufactured with the PCC, both PCC and TSS, exhibited a reduction in total energy output on average of 19.4% and 41.3% respectively during thermal abuse. ISCD triggered thermal runaways also observed reductions of 24.6% and 30.3% with these respective cell material configurations. Prevention of thermal runaway is a transformative advancement in improving lithium-ion battery safety, especially in the cylindrical 18650-format cell. Additionally, significant reductions in the calorific output during failure were measured. These safety innovations provides efficacy of these materials independent of cell chemistry (provided they are stable in the operating environment) while also increasing the energy density and be assimilated into existing manufacturing technology.Furthermore, the authors demonstrate correlative high-speed acoustic spectroscopy during routine cycling of a commercial 210 mAh lithium-ion pouch cell and during thermal abuse 5. Mechanical deformation such as gas-induced delaminations, which have been linked to degradation in electrochemical performance, capacity retention, cell state of health and impending thermal runaway, were detected. This degradation was observed with characteristic acoustic spectroscopy signal peaks changes during cycling due to cell manufacturing defects and during induced thermal abuse, were corroborated with high speed synchrotron X-ray imaging. This analysis can be observed immediately after application of the acoustic probe which emphasises the rapid diagnostics insights provided by acoustic spectroscopy as a robust field deployable technique. Thus, integration into battery management systems, second-life evaluation/recycling or as in-line cell metrology during manufacturing would provide real time direct insight into these metrics. Finegan DP, Darcy E, Keyser M, et al. Identifying the Cause of Rupture of Li-Ion Batteries during Thermal Runaway. Adv Sci. 2018. doi:10.1002/advs.201700369Pham MTM, Darst JJ, Walker WQ, et al. Prevention of lithium-ion battery thermal runaway using polymer-substrate current collectors. Cell Reports Phys Sci. 2021. doi:10.1016/j.xcrp.2021.100360Robinson JB, Pham M, Kok MDR, Heenan TMM, Brett DJL, Shearing PR. Examining the Cycling Behaviour of Li-Ion Batteries Using Ultrasonic Time-of-Flight Measurements. J Power Sources. 2019;444.Robinson JB, Maier M, Compton T, Alster G, Brett DJL, Shearing PR. Spatially resolved ultrasound diagnostics of Li-ion battery electrodes. Phys Chem Chem Phys. 2018. doi:10.1039/c8cp07098aPham MTM, Darst JJ, Finegan DP, et al. Correlative acoustic time-of-flight spectroscopy and X-ray imaging to investigate gas-induced delamination in lithium-ion pouch cells during thermal runaway. J Power Sources. 2020;470:228039. doi:10.1016/j.jpowsour.2020.228039

Impacts of Dissolved Ni2+ on the Solid Electrolyte Interphase on a Graphite Anode

Transition metal (e.g. Ni) ions dissolved from layered-structured Ni-rich cathodes can migrate to the anode side and accelerate the failure of lithium-ion batteries. The investigations of the impact and distribution of Ni species on the solid electrolyte interphase (SEI) on the anode are crucial to understand the failure mechanism. Herein, we used time-of-flight secondary ion mass spectroscopy (TOF-SIMS) coupled with multivariate curve resolution (MCR) analysis to intuitively characterize the distribution of Ni species in the SEI. We find that the SEI on the graphite electrode using an EC-based electrolyte exhibits a multi-stratum structure. During accelerated aging of the LiNi0.88 Co0.08 Mn0.04 O2 /graphite full cell, the dissolution of Ni aggravates significantly upon cycling. A strong correlation between the dissolved-Ni and organic species in the SEI on graphite is illustrated. The ion-exchange reaction between Ni2+ and Li+ ions in the SEI is demonstrated to be the main reason for the increase of SEI resistivity.

Comprehensive gas analysis of a 21700 Li(Ni0.8Co0.1Mn0.1O2) cell using mass spectrometry

The failure of lithium-ion batteries (LIBs) can be partly defined by the release of toxic and flammable gases. The composition and volume of these gases varies depending on cell type, failure mechanism, state of charge (SoC) and environmental oxygen (O2) levels. Understanding this relationship and the species produced is essential for battery pack manufacturers relying on real-time monitoring to assess the state-of-health (SoH) of a LIB. It also has ramifications for emergency responders attending thermal runaway (TR) events. In this work, NMC-811 21700 cells were overheated, and the resulting gas analysed in real-time using mass spectrometry (MS). Repeat tests were conducted to account for variability. Work has been carried out to both quantify the volume of gas produced and investigate how gas composition changes during different stages of cell failure. Tests were conducted at 5–100% SoC. Results showed that during safety venting (SV), the major constituent gas is methane (CH4), which was positively correlated with SoC. In contrast, during TR the gas mixture contains hydrogen (H2), carbon dioxide (CO2) and carbon monoxide (CO). Further analysis to quantify gas volumes show a 3 to 5-fold increase, in both air and nitrogen (N2) atmospheres, when SoC is increased from 25% to 100%.

Working temperature effects on mechanical integrity of cylindrical lithium-ion batteries

The purpose of this study is to explore the influences of working temperatures on mechanical properties and the short circuit of cylindrical lithium-ion cells. A series of compression and three-point bending experiments of a typical 18,650 cylindrical lithium-ion battery is implemented during the discharging process in different working temperatures. The experimental results show that the working temperature presents a negative correlation with the onset of short-circuit in compression loading but non-significant effects on mechanical properties in three-point bending. For the discharging rate, there are non-significant effects on mechanical properties and short circuits of battery cells in both bending and compression loading experiments. In summary, the working temperature effects cannot be neglected in cylindric lithium-ion battery failure, and combined simulation and experimental results indicate that the short circuit criteria for a highly efficient FE battery cell modeling can be established based on internal stress in a specific direction.

Experimental Study on Thermal-Induced Runaway in High Nickel Ternary Batteries.

Recently, fire and explosion accidents associated with lithium ion battery failure occurred frequently. Safety has become one of the main constraints on the wide application of lithium ion batteries in the field of electric vehicles (EVs). By using a simultaneous thermal analyzer (STA8000) and accelerating rate calorimetry (ARC), we studied the thermal stability of high nickel battery materials and the high temperature thermal runaway of the battery, combining the two experimental results to analyze the battery thermal runaway process. We studied the temperature difference between inside and outside during thermal runaway by arranging two temperature sensors inside and outside the battery. The chemical reactions of the battery at high temperature through the thermal performance of the anode, cathode, and separator are also revealed. In-depth exploration of the occurrence process and the trigger mechanism of thermal runaway of lithium batteries was made. The main findings of the study are as follows: The temperature at which the anode materials begin to decompose is 77.13 °C, caused by decomposition of the solid electrolyte interface and the temperature at which the cathode materials begin to decompose is 227.09 °C. The maximum surface temperature of the battery during thermal runaway is 641.41 °C; and the maximum inside temperature of the battery is 1117.80 °C. The time difference between the maximum temperatures inside and outside the battery is 40 s. The thermal runaway temperature of the battery Tc is 228.47 °C, which is mainly contributed by the internal short circuit of the anode and cathode to release Joule heat and the cathode/electrolyte reaction. The maximum temperature of Tm is 642.65 °C, which is mainly caused by the reaction between oxygen and electrolyte.

Improved Zero-Charge Storage Performance of LiCoO2/Mesocarbon Microbead Lithium-Ion Batteries by Li5FeO4 Cathode Additive.

Discharging lithium-ion batteries to zero-charge state is one of the most reliable ways to avoid the thermal runaway during their transportation and storage. However, the zero-charge state causes the degradation or even complete failure of lithium-ion batteries. Specialized solutions are required to endow lithium-ion batteries with improved zero-charge storage performance, namely, the ability to tolerate zero-charge state for a long time without unacceptable capacity loss. Here, we report that a Li5FeO4 cathode additive can improve the zero-charge storage performance of LiCoO2/mesocarbon microbead (MCMB) batteries. The irreversible charge capacity of the Li5FeO4 additive results in the downregulation of anode and cathode potentials when the battery is at zero-charge state. More importantly, the Li5FeO4 additive offers a small discharge plateau below 2.9 V versus Li/Li+, which can hold the anode potential at zero-charge battery state (APZBS) in a potential range of 2.4∼2.5 V versus Li/Li+ during storage for 10 days. Such a precise control on APZBS not only suppresses the decomposition of the solid electrolyte interface film on the MCMB anode and inhibits the dissolution of the copper current collector occurring at high potentials but also avoids the excessive decrease of the cathode potential at the zero-charge battery state and consequently protects the LiCoO2 cathode from overlithiation occurring at low potentials. As a result, the Li5FeO4 additive with a charge capacity percentage of 23% in the cathode increases the capacity recovery ratio of the LiCoO2/MCMB battery from 37.6 to 95.5% after being stored at the zero-charge state for 10 days.

Characterization of in-situ material properties of pouch lithium-ion batteries in tension from three-point bending tests

To understand the mechanisms of deformation and failure of lithium-ion batteries in case of a crash, it is necessary to accurately characterize their constitutive properties. Previous studies in the field mainly focused on the homogenized compression properties of the cells, which are dominant in load cases such as local indentations. However, in complex practical loadings, such as bending, tension properties play an equally important role. Such complex loads can lead to rupture of the electrode tabs and external short-circuits, which can cause catastrophic outcomes. In the current literature, tensile properties are characterized using specimens extracted from the cell, outside of their operational environment, which leads to unrealistic values. In this study, for the first time, an analytical characterization method is developed to extract the homogenized tensile properties of a cell from bending tests in in-situ conditions. In the next step, this data is used, along with an elaborative procedure, to calibrate a fully uncoupled anisotropic material model for the pouch cells. The material model is utilized to build a single homogenized finite element pouch cell model which is the first of its kind to be validated in all major loading cases; flat, hemispherical, and cylindrical punch indentations and specifically three-point bending, and in-plane compression. This material characterization and the modeling approach provide a universal tool in predicting the load-displacement, shape of deformation, buckling wavelength, and the trend of failure in complex crash scenarios for the safety assessments of Lithium-ion batteries.