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Exploring the electrochemical and mechanical properties of lithium-ion batteries in salt spray environments
There is a need to study the evolutionary laws of the risks in the navigation environments of complex marine areas. This can promote shipping safety using an early-warning system. The present study determines shipping flows and meteorological conditions in a marine area on the basis of meteorological and automatic identification system (AIS) data. It also determines the uncertainty evolution law of the navigation environment’s influencing factors. Moreover, a navigation risk evolution system for ships in complex marine areas was developed. A case study was carried out in a coastal area of China on the basis of the determined evolutionary laws. Evolution in the navigational environment risk within the case study area was analyzed. The results showed that the hydrometeorology wind factor has the greatest impact on the risk of ship collisions. This work was not only able to show advances in navigational collision environmental evolution laws but also provides a theoretical reference for the evaluation and early warning of risks in shipping environments.
Understanding the mechanism of battery thermal runaway propagation under low atmospheric pressure is critical for the safe operation of battery energy storage systems. This work explores the thermal runaway propagation over a linear arrayed 18650-type lithium-ion battery module in a low-pressure chamber. The effects of ambient pressure (0.1 kPa to 100 kPa), temperature, and electrical connection mode are comprehensively investigated. Results indicate that the propensity of thermal runaway propagation for the open-circuit battery array is much lower, and it only occurs at high ambient temperature and ambient pressure. For parallel-connected battery modules, as ambient pressure decreases, the rate of thermal-runaway propagation first increases due to the reduced environmental cooling (i.e., thermal controlled). It then falls due to lower remaining electrolytes after venting (i.e., venting controlled). The pressure of maximum thermal runaway propagation speed is 60 kPa. The maximum time interval for the thermal runaway of the next cell is about 7 min. A simplified heat transfer analysis was proposed to explain the trend and limits of thermal runaway propagation and reveal the dual effect of pressure. This work provides new insights into thermal runaway propagation, which can deepen the understanding of battery fire safety under low pressure and inspire the thermal-safety design of the lithium-ion battery modules.
The mechanically induced internal short circuit (ISC) is one of the major safety concerns of lithium‐ion batteries. Mechanical abuse tests are often performed to evaluate the integrity and safety of lithium‐ion batteries under mechanical loadings. Except for the widely explored compression‐dominated indentation tests, bending is another typical real‐world loading condition that is tension‐dominated. To investigate the mechanical damage and ISC behavior of batteries under bending, we carried out controlled three‐point bending tests in four progressive steps on prismatic battery cells with maximum deflections ranging from 38% to 76% of the cell thickness. None of the tested cells experienced an ISC. We then conducted 3D X‐ray computed tomography (CT) scanning on the bent cells after unloading. X‐ray CT images showed three out of the four tested cells have extensive cracking in the electrode layers at the bottom side (opposite to the loading head). This indicates that cracking does not necessarily lead to an ISC under bending. Electrochemical impedance spectroscopy was also measured on the bent cells and substantial changes were observed. Both the bulk resistance and charge‐transfer resistance increased significantly after bending, which could influence the battery performance and lifespan. We then developed a detailed finite (FE) element model to further investigate the mechanical deformation and failure mechanisms. The FE model successfully predicts the load–displacement response and reproduces the deformation patterns. The findings and the FE model developed in the present study provide useful insights and tools for the battery structure and crash safety design.
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Pouch type lithium-ion battery (LIB) has now been widely used in electric vehicles, smartphones, computers and et al. Mechanical abuse is one of the main reasons to cause the safety issues for lithium-ion battery. The highly accurate and efficient computational model is helpful for the safety design, application and analysis of LIB. The previous homogenized mechanical models of the pouch LIB use different material parameters for various loading conditions. Herein, we establish an anisotropic homogenized method to predict the mechanical behavior in in-plane and out-of-plane directions simultaneously. Engineering constants and Hill's 48 criteria are used for the anisotropic properties, and bilinear plastic model is used as the hardening curve under large deformation. Based on this method, we established two homogenized models i.e. one-layer model and multi-layer model. Experiments in various loading conditions including 3-point bending (length direction and width direction), out-of-plane compression, and in-plane compression (length direction and width direction) are conducted for parameters calibration. The calibration methods are then discussed and confirmed through these experiments. The computational models show good correlation with experiments both in in-plane and out-of-plane directions. The difference is that the global buckling behavior can be predicted by both of the two models, while the local buckling can only be predicted by the multi-layer model. The results may shield light on the safety design, application and analysis for pouch LIB.
In order to understand the lithium-ion battery (LIB) failing behavior and to prevent failures and their consequences, different LIB safety tests, also called abuse tests, have been developed. This paper focuses on thermal runway (TR) triggered by overtemperature, overcharge and nail-penetration. It shows the setup and the results of the three different TR triggers on two different cell types in a custom-made TR reactor. The investigated cell types are state-of-the-art automotive pouch and hard case cells. The results are discussed in three main categories: thermal behavior, vent gas production and vent gas composition. The results and findings are supposed to be valuable for battery pack designer, car manufacturer and testing institutions for the development of future battery testing facilities and regulations.
Based on the trend, there have been numerous researches analysing the ship collision risk. However, in this scope, the navigational conditions and external environment are ignored or incompletely considered in training or/and real situation. It has been identified as a significant limitation in the navigational collision risk assessment. Therefore, a novel algorithm of the ship navigational collision risk solving system has been proposed based on basic collision risk and vulnerabilities of marine accidents. The vulnerability can increase the possibility of marine collision accidents. The factors of vulnerabilities including bad weather, tidal currents, accidents prone area, traffic congestion, operator fatigue and fishing boat operating area are involved in the fuzzy reasoning engines to evaluate the navigational conditions and environment. Fuzzy logic is employed to reason basic collision risk using Distance to Closest Point of Approach (DCPA) and Time of Closest Point of Approach (TCPA) and the degree of vulnerability in the specific coastal waterways. Analytical Hierarchy Process (AHP) method is used to obtain the integration of vulnerabilities. In this paper, vulnerability factors have been proposed to improve the collision risk assessment especially for non-SOLAS ships such as coastal operating ships and fishing vessels in practice. Simulation is implemented to validate the practicability of the designed navigational collision risk solving system.
Energy storage is an integral part of modern society. A contemporary example is the lithium (Li)-ion battery, which enabled the launch of the personal electronics revolution in 1991 and the first commercial electric vehicles in 2010. Most recently, Li-ion batteries have expanded into the electricity grid to firm variable renewable generation, increasing the efficiency and effectiveness of transmission and distribution. Important applications continue to emerge including decarbonization of heavy-duty vehicles, rail, maritime shipping, and aviation and the growth of renewable electricity and storage on the grid. This perspective compares energy storage needs and priorities in 2010 with those now and those emerging over the next few decades. The diversity of demands for energy storage requires a diversity of purpose-built batteries designed to meet disparate applications. Advances in the frontier of battery research to achieve transformative performance spanning energy and power density, capacity, charge/discharge times, cost, lifetime, and safety are highlighted, along with strategic research refinements made by the Joint Center for Energy Storage Research (JCESR) and the broader community to accommodate the changing storage needs and priorities. Innovative experimental tools with higher spatial and temporal resolution, in situ and operando characterization, first-principles simulation, high throughput computation, machine learning, and artificial intelligence work collectively to reveal the origins of the electrochemical phenomena that enable new means of energy storage. This knowledge allows a constructionist approach to materials, chemistries, and architectures, where each atom or molecule plays a prescribed role in realizing batteries with unique performance profiles suitable for emergent demands.
During an accident of an electric vehicle, the battery pack can be damaged by the intrusion of an external object, causing large mechanical deformation of its lithium-ion battery cells, which may result in an electrical short circuit and subsequently the possible thermal runaway, fire, and even explosion. In reality, the external objects can come in different directions, for example, an out-of-plane indentation that perpendicularly punches the large surface of the pouch cell and an in-plane loading that compresses the thin edge of the cell. In this study, the mechanical deformation of a large-format lithium-ion pouch cell under in-plane loads is investigated via three different types of tests - in-plane compression of fully constrained cells, in-plane compression of cells sandwiched by foams, and in-plane indentation by a round punch. A special apparatus is designed to apply different boundary conditions on the cell, and the deformation history, especially the formation of the buckles of the cells, are monitored by two digital cameras. Post-testing structural analysis is carried out by a cross-sectional cutting and polishing procedure, which gives clear evidence of buckling of all the component layers. © 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
Rapid growth in the market for electric vehicles is imperative, to meet global targets for reducing greenhouse gas emissions, to improve air quality in urban centres and to meet the needs of consumers, with whom electric vehicles are increasingly popular. However, growing numbers of electric vehicles present a serious waste-management challenge for recyclers at end-of-life. Nevertheless, spent batteries may also present an opportunity as manufacturers require access to strategic elements and critical materials for key components in electric-vehicle manufacture: recycled lithium-ion batteries from electric vehicles could provide a valuable secondary source of materials. Here we outline and evaluate the current range of approaches to electric-vehicle lithium-ion battery recycling and re-use, and highlight areas for future progress. Processes for dismantling and recycling lithium-ion battery packs from scrap electric vehicles are outlined.
Due to rising safety requirements for lithium-ion batteries, the detection of mechanical failure of such batteries is becoming increasingly important. As publications investigating electrochemical impedance spectroscopy (EIS) of lithium-ion battery cells under deforming mechanical abuse as a potential damage detection method are sparse, this work presents tests with stepwise loading of 18,650 lithium-ion battery cells with various impactors (nails, cylindric, hemispheric) and simultaneous EIS measurements to search for indicators which could be used to anticipate hazardous events. The occurrence of different damage mechanisms of the jelly roll is evaluated via computed tomography (µ-CT) and correlated to the measured changes in EIS. For internal short circuits (ISCs) without instantaneous thermal runaway, the results show a decrease of ohmic resistance in the EIS for high measurement frequencies, which is possibly linked to temperature increase, while low frequencies indicate deviations from stationarity or linearity requirements. In the case of large area compression, the EIS measurements display an increase of ohmic resistance, which may be connected to various mechanisms, such as the decrease of porosity of the separator and the active materials or delamination.
The swelling of lithium-ion batteries (LIBs) is one of the responsible reasons to cause capacity degradation and safety problems. Quantification of the swelling force and the corresponding strain is a critical problem in exploring the complex electro-mechanical behaviors in batteries. Though in the current open literature, a few models are available to describe the swelling of the component materials in a battery. A physics-based detailed model linking the component material scale to the cell scale is still lacking. Herein, we develop a fully detailed three-dimensional swelling mechanical model considering the actual structure of the battery. After rigorous validation by the experiment, we leverage the model to investigate a complicated coupled boundary, i.e., plate-constrained swelling. The swelling force and uneven stress distribution of each component are analyzed among various influential factors. The results provide fundamental insights into the application of LIB.
This work addresses the effects of varying nitriding temperatures of 530, 560 and 580 °C for 2 h on corrosion resistance of additively manufactured (AM) 17-4 PH steels, using neutral salt spray (NSS) method for 104 h. The morphological analysis indicated the presence of columnar grains along the built direction of additive manufacturing process. The refined grain size and the amount of the precipitates increased with an increasing nitriding temperature. The results of the analysis showed that a minimum weight loss was observed at 580 °C, due to the formation of passive oxide layer and nitrogen rich precipitates on the surface. The X-ray diffraction (XRD) showed the presence of these compounds: Cr2N, (Fe, Cr)4N, (Fe, Cr)2-3N, Fe2O3, FeOOH, and Cr2O3 on the nitrided sample after the salt spray test.
Most of the mechanical abuse to which lithium-ion batteries (LIBs) are subjected in real-life scenarios is dynamic, and the safety issues involved are cause for concern. An accurate dynamic failure threshold is needed for both safety assessment and engineering protection of LIBs. In this work, the dynamic mechanical response and external voltage behavior of 18650 cylindrical LIBs with various state of charge (SOC) values are investigated via drop weight tests firstly. Then, a novel anisotropic model, incorporating the SOC effects and damage settings, is developed. The model can well predict the mechanical behaviors of LIBs for both quasi-static loading and dynamic radial compression. In addition, a satisfactory consistency is achieved between the cracks formed within the battery and the micro-CT scanning results. Further, a two-stage failure criterion defined by the jellyroll equivalent plastic strain is proposed, based on two special failure modes of LIBs, namely electrochemical failure and structural failure. The failure threshold for LIBs with multiple SOCs is established at various impact masses and shapes. Results provide a high-fidelity computational model for the battery safety behaviors upon dynamic mechanical loading and guidelines for the design of next-generation robust batteries.
Aging of lithium-ion batteries is especially important for applications such as battery electric vehicles, where they constitute a major part of the total cost and practically determine product lifetime. One of the main problems during cycle aging is the swelling of the electrode stack, as this results in increased mechanical stresses inside batteries and can further accelerate aging. Earlier studies have used X-ray tomography to address this issue and were focused on the role of large aberrations in electrode geometry in rapid capacity fade. In this study, however, we focus on batteries not exhibiting such a rapid deterioration, where only small changes to electrode geometry can be expected. Helical trajectory micro-computed X-ray tomography and virtual unrolling were used to reveal axially and radially inhomogeneous swelling of the jelly-roll electrode windings inside commercial 18650 batteries. The results supported by mathematical-physical simulations demonstrate the efficacy of the employed methods in the analysis of minute volumetric changes and show that regions inside the batteries that are comparatively unconstrained mechanically experience accelerated swelling. In particular, the top and bottom of the jelly-roll showed an elevated thickness increase, especially within the innermost windings.
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 18650 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.
In this study, the reversible thickness change of a large-format lithium-ion automotive pouch cell is investigated under precisely monitored cell pressure and temperature using an in-house built actively controlled pneumatic cell press. The quantitative and qualitative contribution of the state-of-the-art NMC811 cathode and the SiO-graphite composite anode to the total pouch cell expansion is resolved by electrochemical dilatometry and validated. Results show that Ni-rich cathodes have a significant impact on the pouch cell expansion and exhibit highly nonlinear thickness change which is related to the change of the individual lattice parameters of the crystal structure. To resolve the contribution of both anode active materials to the total anode expansion, the capacities of SiO and graphite are determined by differential voltage analysis and validated with half-cell measurements. Then, the volume expansion of SiO and graphite as a function of the anode state of charge is calculated. By introducing fitting parameters and applying theories about the interaction of SiO with the surrounding morphology the correlation between the volume expansion of the active materials and the thickness change of the SiO-Gr composite anode is investigated. The findings suggest that there is significant nonlinear reduction of pore volume at low state of charge.
Under the environmental conditions of the aircraft carrier surface, the structure of the carrier aircraft has to withstand the interaction between the takeoff and landing impact load and the corrosion of the marine environment. 38CrMoAl steel is the main material of a carrier aircraft structure which is frequently subjected to impact load. In order to obtain its dynamic fracture toughness under corrosive conditions, it was tested by a experimental-numerical method. The dynamic constitutive model parameters of the corroded 38CrMoAl steel were obtained through dynamic mechanical tests, which were imported into the established finite element model to obtain the dynamic fracture factor time history curve of the material under corrosive conditions. Then, the dynamic crack initiation time of the corroded 38CrMoAl steel was obtained by the three-point bending dynamic fracture toughness test device. Combined with the dynamic fracture factor time history curve, the dynamic fracture toughness of the corroded 38CrMoAl steel was determined. Finally, the fracture mechanism of 38CrMoAl steel under the interaction between corrosion and high strain rate loading was analyzed according to the fracture morphology and EDS energy spectrum of specimens with different loading rates and corrosion cycles. This method provides a new idea for testing the dynamic fracture toughness of corroded materials.
Mechanical integrity is one of the study focuses of lithium-ion batteries, which is greatly influenced by the loading rate and the cycling ageing level. This paper investigates how dynamic loading and low-temperature ageing collectively affect the safety performance of lithium-ion batteries under indentation loadings, by monitoring and comparing the in-situ mechanical-electrical-thermal responses. For the mechanical response, results show that dynamic loading increases the battery stiffness while low-temperature ageing alleviates that. During the intrusion process, the electrical response is mostly influenced by the loading rate. Fast voltage dropping and recovering occur under dynamic loading scenarios, leaving a downward trench in the voltage profile. The higher the loading rate, the earlier the short circuit and the faster the voltage dropping. After the termination of the loading, the voltage dropping is mostly affected by the ageing level. Low-temperature ageing accelerates the long-term voltage dropping rate. As for the thermal response, it is highly related to the short circuit behavior. Upward temperature peaks are formed right after the short circuit under dynamic loadings, corresponding to the voltage trenches. Besides, aged cells have higher long-term temperature profiles, corresponding to the accelerated long-term voltage dropping rates.
The strongly growing uptake of lithium-ion batteries (LIBs) in transportation requires environmentally sustainable ways to treat spent batteries. Novel material circulation processes establish material flows which create significant business opportunities and new jobs and welfare. This paper develops a mathematical model for considering the circular economy in the life cycle costs in the maritime sector. Current articles and models do not quantify economic gains from the LIB circular economy, especially in the marine sector. An additional challenge is that the typical planned lifetime is 30 years which means that the battery energy storage of a ship needs to be retrofitted 1–3 times over the ship's lifetime. The analysis herein considers the cost evolution of ESS during the coming decades to estimate retrofit battery costs and re-use economics. The main finding of the study is that battery material circulation can be conducted in all phases over the lifetime of the marine application and clear revenue streams are identified. These are not only deceasing the costs for battery investment, but are also able to bring revenues, leading to commercially viable reuse of batteries. However, it is also concluded that material circulation requires more technological, procedural, and industrial innovations during the coming years.
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.
Thermal runaway (TR) is a major safety concern for lithium-ion batteries. A TR model incorporating the resulting jet fire can aid the design optimization of battery modules. A numerical model has been developed by coupling conjugate heat transfer with computational fluid dynamics (CFD) to capture the cell temperature and internal pressure evolution under thermal abuse, venting and subsequent combustion of 18650 lithium-ion batteries. The lumped model was employed to predict the thermal abuse reactions and jet dynamics, while the vented gas flow and combustion were solved numerically. Model validation has been conducted with newly conducted experimental measurements for the transient flame height of jet fire and temperatures at selected monitoring points on the cell surface and above the cell. The validated model was then used to investigate the effect of the SOCs on the evolution of TR and subsequent jet fires. Increasing SOCs shortens the onset time of TR and enlarges the peak jet velocity. The peak heat release rates and flame height of the jet fire increase with the increase of SOC. The developed modeling approach extends the TR model to jet fire and it can potentially be applied to assist the design of battery modules.
Lithium-ion batteries (LIBs) have played an increasingly dominant role in the current mobile society. Due to the risky safety testing procedure, ultra-rigorous demands of the testing facility, and complicated multiphysics nature of the safety issues, the lacking of high-fidelity models to describe the safety behaviors of lithium-ion batteries upon abusive loading has significantly deferred the further application of LIBs. Herein, by assistance from the ex-situ observation using the X-ray Computed Tomography scanning technique and post-mortem characterization of the battery samples, we reveal the formation process of various ISC modes upon abusive loading guiding our modeling. A strain-based and ISC mode-dependent criterion is first developed to establish a mechanical-electrical coupling relationship. Particularly, we establish a fully multiphysics-coupled model capable of identifying various internal short circuit (ISC) modes and describing the entire evolution process of the battery from the initial deformation to the final thermal runaway (TR) of the LIBs. The multiphysics model demonstrates a promising generalization in various SOC and loading situations. Finally, the multiphysics model is applied for 100% SOC of the LIB to reveal the evolution mechanism of deformation-different ISC modes-TR. Results highlight the power of computational modeling to understand the underlying mechanism of safety issues in energy storage systems in a broader context.
Electrode processing plays an important role in advancing lithium-ion battery technologies and has a significant impact on cell energy density, manufacturing cost, and throughput. Compared to the extensive research on materials development, however, there has been much less effort in this area. In this Review, we outline each step in the electrode processing of lithium-ion batteries from materials to cell assembly, summarize the recent progress in individual steps, deconvolute the interplays between those steps, discuss the underlying constraints, and share some prospective technologies. This Review aims to provide an overview of the whole process in lithium-ion battery fabrication from powder to cell formation and bridge the gap between academic development and industrial manufacturing.
In response to environmental pollution and the energy crisis, the number of electric vehicles (EV) has increased year by year. However, frequent EV accidents have pushed the safety of EVs to a new height of attention. The failure of lithium-ion batteries (LIBs) is the root of most accidents. Although many standards have been made, the battery system's safety still lacks scientific, comprehensive, and quantifiable assessment. Here, we innovatively put forward a comprehensive map of LIBs failure evolution combining battery tests and forward development. By analyzing the root cause of the EV fire through the Fault Tree Analysis (FTA), 20 basic events, 26 minimum cut sets, and 29 battery tests related to the accident were obtained. The result indicates that the low thermal stability materials and battery management system (BMS) failure to warn in time are the most important factors leading to EV fire. According to the test content, the battery tests are classified, and the Analytic Hierarchy Process (AHP) model of the battery test is established. By comparing the importance of every two tests with the judgment matrix, the weights of battery tests are obtained. Finally, combining with the fault tree branch structure, comprehensive forward development suggestions are put forward to improve the safety of EV.
Battery systems are becoming an increasingly attractive alternative for powering ocean going ships, and the number of fully electric or hybrid ships relying on battery power for propulsion and manoeuvring is growing. In order to ensure the safety of such electric ships, it is of paramount importance to monitor the available energy that can be stored in the batteries, and classification societies typically require that the state of health of the batteries can be verified by independent tests — annual capacity tests. However, this paper discusses data-driven state of health modelling for maritime battery systems based on operational sensor data collected from the batteries as an alternative approach. Thus, this paper presents a comprehensive review of different data-driven approaches to state of health modelling, and aims at giving an overview of current state of the art. More than 300 papers have been reviewed, most of which are referred to in this paper. Moreover, some reflections and discussions on what types of approaches can be suitable for modelling and independent verification of state of health for maritime battery systems are presented.
In recent years, energy and environmental issues have become more and more prominent, and electric vehicles powered by lithium-ion battery have shown great potential and advantages in alleviating these issues. Compared with other batteries, lithium-ion batteries have the advantages of high specific energy, high energy density, long endurance, low self-discharge and long shelf life. However, temperature of the battery has become one of the most important parameters to be handled properly for the development and propagation of lithium-ion battery electric vehicles. Both the higher and lower temperature environments will seriously affect the battery capacity and the service life. Under high temperature environment, lithium-ion batteries may produce thermal runaway, resulting in short circuit, combustion, explosion and other safety problems. Lithium dendrites may appear in lithium-ion batteries at low temperature, causing short circuit, failure to start and other operational faults. In this paper, the used thermal management methods of lithium-ion batteries are introduced and their advantages and disadvantages are discussed and compared. At the same time, the prospect of future development is put forward.
A review summarizes and characterizes the calorimetric results of commercial 18650 lithium-ion batteries under thermal runaway. The cathode materials of 18650 batteries include LiCoO2, LiMn2O4, LiNixMnyCozO2, LiNi0.8Co0.15Al0.05O2, and LiFePO4. Characterization data obtained from calorimetry encompass the exothermic onset temperature, crucial temperature, maximum temperature, maximum self-heat rate, quantity of non-condensable gas, and enthalpy change. Maximum pressure and pressure-rising rate are not taken account of consideration because of the significant dependence on volume of the test system. A hexagonal radar plot is newly proposed for the presentation of runaway hazards aforementioned and associated with respective cathode chemistries. By integrating all the hazard data in the literature into hexagonal plots, the ranking of the hazard potential of commercial 18650 batteries is clearly assessed as follows: LiNi0.8Co0.15Al0.05O2 > LiCoO2 > LiNixMnyCozO2 > LiMn2O4 >> LiFePO4. The LiNi0.8Co0.15Al0.05O2 battery displays the worst case scenario among all the 18650 batteries owing to these highest maximum temperature, maximum self-heat rate, maximum pressure, quantity of non-condensable gas, and enthalpy change under thermal runaway. Differential characteristics of thermal runaway among LiCoO2, LiNixMnyCozO2, and LiNi0.8Co0.15Al0.05O2 batteries are discriminated and discussed. All the non-LiFePO4 batteries act similarly with a maximum self-heat rate exceeding 10000°C min⁻¹ and a crucial temperature occurring at approximately 200°C. The 18650 LiFePO4 battery holds the highest exothermic onset temperature, lowest maximum temperature, lowest maximum self-heat rate, least non-condensable gases and lowest enthalpy change, indicating that the 18650 LiFePO4 battery is relatively safer than others. On the state of the art, a review is detailed herein and future perspectives are propounded as well. This integrated review of 18650 batteries under thermal failures provides a systematic database for extensive experimental investigations, theoretical studies and designs of safer batteries.
Micro arc oxidation (MAO) coating was prepared on AA2024 as a substitute of sulphuric acid anodizing (SAA) with the aim to improve anticorrosion behavior. Evaluation of corrosion resistance was first performed by means of salt spray test (SST) as a conventional but long way in time method, usually more than 1000 h for aeronautical needs. In parallel, an original approach combining electrochemical characterization and Artificial Intelligence was evaluated in order to predict corrosion occurrence in SST. The electrochemical setup consist in an improvement of ISO17463 accelerated cyclic electrochemical method (ACET) with an additional linear polarization step. The whole generates up to 50 parameters that are treated by artificial neural network (ANN). After training and refinement, the average accuracy of predicted corrosion resistance and corroded surface after 200 h of SST are 99 and 90% respectively. This promising combination of ACET and ANN enables the evaluation of corrosion behavior of coating in less than 24 h.
Battery safety is critical to the application of lithium-ion batteries, especially for high energy density battery applied in electric vehicles. In this paper, the thermal runaway mechanism of LiNi0.8Co0.1Mn0.1O2 based lithium-ion battery is illustrated. And the reaction between cathode and flammable electrolyte is proved as the trigger of the thermal runaway accident. In detail, with differential scanning calorimeter tests for battery components, the material combination contributing to thermal runaway was decoupled. Characterization with synchrotron X-ray diffraction and transmission electron microscopy with in-situ heating proved that the vigorous exothermic reaction is initiated by the liberated oxygen species. The pulse of highly active oxygen species reacted quickly with the electrolyte, accompanied with tremendous heat release, which accelerated the phase transformation of charged cathode. Also, the mechanism is verified by a confirmatory experiment when the highly active oxygen species were trapped by anion receptor, the phase transformation of the charged cathode was inhibited. Clarifying the thermal runaway mechanism of LiNi0.8Co0.1Mn0.1 based lithium-ion battery may light the way to battery chemistries of both high energy density and high safety.
Despite the huge expansion of electric vehicle sales in the market, customers are discouraged by the possible catastrophic consequences brought by the safety issues of lithium-ion batteries, such as internal short circuits, especially in crash scenarios. Herein, we reveal the quantitative relation between the deformations of the battery and the internal short circuit. By designing insitu, ex-situ observation and post-mortem characterization of the component materials, we quantify the stress-driven internal short circuit and failure behavior of the component material. With the aid of the validated numerical computational model as well as the in-situ characterization of the globalfield temperature, we successfully identify the minor and major short circuits of the cells upon various mechanical abusive loadings. Finally, we establish the internal short circuit criteria for typical formats of batteries. This discovery also provides a fundamental understanding of both internal and external stress-driven short circuits in a much broader context.
The emergence of electric vehicles equipped with lithium-ion batteries has largely alleviated the environmental crisis, however, the safety and sustainable development of lithium-ion batteries under mechanical abuse conditions is increasingly becoming an obstacle for the promotion of electric vehicles. Lithium-ion batteries exhibit mechanical, electrical, thermal and other multiphysics coupling response behaviors when suffering from mechanical abuse such as compression. In this paper, two high-efficiency multiphysics coupling frameworks and strategies (calculation process) are proposed innovatively. Three abuse tests, flat plate test, rigid rod test and hemispherical punch test under the quasi-static condition are carried out to create mechanical abuse conditions. The geometric-level multiphysics coupling model couples the 3D mechanical model, the 3D thermal model, the 0D battery electrical model and the 0D short-circuit model to provide visual simulation results for battery failure analysis. The simulation results show that the geometric-level multiphysics coupling model can accurately explain the battery failure behavior under a variety of operating conditions, with a calculation time of no more than 1 h on a universal computation platform. The lumped-parameter high-efficiency multiphysics coupling model adopts the lumped-parameter mechanical model and the lumped-parameter thermal model, avoids the finite element calculation process, and can provide efficient and accurate semi-quantitative calculation results for battery safety analysis in the absence of a high-performance computing platform. The calculation time on the universal computation platform is no more than 5 s. The two high-efficiency multiphysics coupling frameworks can adapt to different computational analysis scenarios, helping to analyze the failure mechanism of lithium-ion batteries, improve the safety and maintain the sustainable development of lithium-ion batteries.
Investigation of the multiphysics behaviors of lithium-ion batteries upon mechanical abusive loading becomes a heated topic around the world, and the corresponding modeling methodology is in pressing need. Different from previous modeling methodologies, this paper develops an effective modeling framework based on the representative volume element concept to describe the thermo-mechanical behaviors of lithium-ion batteries. The mesoscale (electrode level) representative volume element model and the macroscale (cell level) homogenous battery model are established and validated by experiments. The two levels are coupled through the homogenization of the mechanical material properties and the calculation of the element power density–strain curve. The internal short circuit behavior can also be well predicted by this model. In addition, the model can predict accurate thermo-electro-mechanical coupled behaviors at a much lower calculation time cost. The proposed new thermo-mechanical modeling methodology in this paper can provide a powerful modeling tool and useful guidance to the design, evaluation, and monitor of the safety behaviors of LIBs.
As one of the commonly used power sources for electric vehicles, cell phones, and laptops, the safety of lithium-ion batteries (LIBs) has aroused more and more attention. Lithium-ion batteries will inevitably suffer from external abuse loading, triggering thermal runaway. Nail penetration is one of the most dangerous external loading methods, so it is meaningful to study the failure behaviors under this loading condition. In this paper, the experimental study of lithium-ion batteries under axial nail penetration is carried out. The lithium-ion battery studied here is commercially available 18650 cylindrical battery with a nickel cobalt aluminum oxide (NCA). Force, temperature and voltage data are recorded synchronously to learn its mechanical, thermal and electrochemical behaviors. Then, the loading velocity effect is discussed, results show the loading velocity has no obvious effect on failure properties of lithium-ion battery. Besides, deformation and failure properties of lithium-ion battery are discussed in detail. A simple homogenous computational model is established to predict the mechanical responses of the battery. The partial detailed model is also established to explore the failure mechanism. The batteries are disassembled after loading to better understand the failure morphologies. Two failure modes are discovered through experiments and computational model. The findings can contribute to a better understanding of the failure mechanism of lithium-ion battery under axial nail penetration, provide reference for battery safe design.
The power system of an All-Electric Ship (AES) establishes an independent microgrid using the distributed energy resources, energy storage devices, and power electronic converters. As a Hybrid Energy System (HES), the power system of an AES works as a unified system where each part can affect the reliability of the other parts. The Systematic Reliability Centered Maintenance (SRCM), which efficiently enhances the reliability and safety of the AES by identifying optimal maintenance tasks of the AES, is considered in this paper to apply on the entire system. In order to calculate the reliability and optimal maintenance schedule, the Markov process and Enhanced JAYA (EJAYA) are utilized. A layer of Protection Analysis (LOPA), which is a risk management technique, is adopted to assess the safety of the system. A hybrid molten carbonate fuel cell, Photovoltaic (PV), and Lithium-ion battery are considered as energy sources of the AES. Based on two common standards, DNVGL-ST-0033 and DNVGL-ST-0373, the suggested maintenance planning method can be used in industrial applications. Eventually, in order to validate the proposed method, a model-in-the-loop real-time simulation using dSPACE is carried out. The obtained results show the applicability and efficiency of the proposed method for improving the reliability and safety.
Dynamic compression is a common scenario of mechanical abuse of lithium-ion batteries for electric vehicles. The safety characteristics under dynamic compression is highly different from that under quasi-static compression, whereas research in this field is still scarce. Here, the lateral quasi-static compression and dynamic compression of two kinds of cylindrical lithium-ion batteries are carried out. According to the first order derivative of the force to the displacement, there are six main stages of the battery behavior under lateral compression. The behavior of STAGE IV under the dynamic compression is obviously different from that under quasi-static compression. Both experimental and modeling results reveal that the dynamic load has a certain strengthening effect on the battery. For both types of batteries, the equivalent strength under high strain rate tends to be consistent. Combined with the Crushable-Foam material model and Johnson-Cook material model, the dynamic and quasi-static mechanical simulation are performed at the cell level, and the simulation results well explain the experimental phenomenon. The simulation and experimental results show that the safety warning of the cylindrical lithium-ion battery based on mechanical penetration has a certain safety margin, which can provide valuable reference for the battery safety under mechanical abuse in the future.
Battery separator is a crucial component of a lithium-ion battery (LIB); it affects the battery performance. However, the effects of the separator on commercial cylindrical LIBs have not been well studied using computational models. This paper presents a numerical study on the effects of separator design on the LIB performance. We developed a two-dimensional electrochemical-thermal coupled model for a 38120-type LiFePO 4 LIB. Model results showed that separator thickness strongly impacted battery energy density: the battery energy density dropped from 148.8 to 110.6 W h/kg, while the separator thickness increased from 5 to 100 μm. In addition, the mass transfer resistance of the separator increased with decreasing separator porosity, resulting in increased electrolyte concentration gradient. However, the correlation between separator porosity and electrolyte concentration gradient indicated that a separator porosity of 80% or greater contributed little to the resistance to mass transfer. Furthermore, the battery temperature rise and temperature difference dropped when both the separator thermal conductivity and heat capacity increased to 1 W m −1 K −1 and 3500 J kg −1 K −1 , respectively.
Thermal runaway and subsequent propagation are the main factors to cause catastrophic consequences in lithium-ion battery packs. Exploring the thermal runaway propagation is thus of great fundamental and practical interest in understanding the mechanism of battery safety. A thermal runaway propagation mathematical model is established by combining the 0 D thermal runaway, and electrical and thermal conduction models that are verified by a series of experiments where thermal runways are triggered by mechanical abusive loading. Two thermal runaway propagation modes are observed and it is found that overheating of the local area or high overall temperature determines the propagation mode. The governing factors of thermal runaway propagation speed, including ambient temperature, packing spacing, and stacking form, are further analyzed. Our analysis reveals a complete link between engineering design variables and the thermal runaway behaviors of a specific battery pack. Our study paves a novel avenue to design the safer and higher energy density lithium-ion battery pack and elevates the limits of battery pack energy density without sacrificing safety risks.
Lithium ion batteries have been widely used in the power-driven system and energy storage system. While thermal safety for lithium ion battery has been constantly concerned all over the world due to the thermal runaway problems occurred in recent years. Lithium ion battery has high temperature sensitivity and the relatively narrow operating temperature range because of the complex electrochemical reactions at different temperatures. And the temperature change, including the global temperature change in different seasons and the local temperature rise that is induced by its self-heating etc., can trigger side reactions and then lead to thermal runaway, which should be further considered to ensure thermal safety of lithium ion battery. This review summarizes the inducements of thermal runaway and relevant solutions, spanning a wide temperature range. The low temperature induced issues, such as capacity fade and lithium plating and dendrite, can cause internal short circuit (ISC), while as the temperature is above the critical temperature, the speeding of side reactions and reduction of lifespan (T > 40 °C) and thermal runaway (T > 90 °C) will be triggered. In order to solve the thermal issues in batteries, extensive approaches have been investigated to prevent the occurrence, propagation and deterioration of thermal runaway, from the perspective of material to the battery system. The triggered mechanism at a wide temperature range, key factors for thermal safety and the effective heat dissipation strategies are concluded in this review. This review is expected to offer effective thermal safety strategies and promote the development of lithium ion battery with high-energy density.
Electromechanical structural integrity and thermal stability dictate the safety performance of lithium-ion batteries. Progressive deformation and failure across microscopic and macroscopic lengths scales that are responsible for internal short circuit (ISC) in lithium-ion cells under mechanical abuse conditions remains elusive. In this study, a series of indentation tests were conducted on lithium-ion cells with different capacities up to the occurrence of ISC. The external response and internal configuration of these cells were investigated. It is discovered that cells with different capacities and state of charges exhibited different behaviors. Maximum temperature, which is often regarded as the most important parameter related to thermal runaway (TR), varied considerably due to the complicated contact configurations. X-ray computed tomography (XCT) showed that ISC was a collective result of shear band or other strain-localization modes in the electrode assembly, shear offsets in the granular coatings of electrodes, and the accompanying ductile fracture in the metal foils. We believe that the irregular strain-localization modes (kinks, cusps, and buckles), radical mismatches in mechanical properties of different layers, and geometric features of the indenter eventually lead to the tearing/puncture of cell separator at various locations. The results could provide useful guidance for the micromechanical modeling of lithium-ion cells.
A frame Structure Comprised of Precast Prestressed Concrete Components (SCOPE) has been widely used in China. According to previous research, the length of non-contact lapped splice between U-shape bars and the steel strands plays an important role in seismic performance of the beam column joint. However, the splice may deteriorate due to corrosion when the frame is used in coastal region. This paper presents an experimental investigation on seismic behaviors of the corroded beam-column joints of the SCOPE system. Ten specimens with different key slot lengths and different corrosion levels were tested under cyclic loading, and their hysteretic loops, envelop curves, bearing capacity, and energy dissipation were compared and analyzed. It is observed that the corrosion of steel bars would significantly affect seismic behaviors of the structure, and most specimens showed flexural failure, while for the seriously corroded specimens with long key slots, failure might occur at the interface between the precast beam and the key slot due to severe corrosion and bond failure of the lapped splice. In general, the energy dissipation of specimens with shorter slot length was greater than that of specimens with the longer key slot under the same corrosion level. However, as the corrosion level increases, the difference became smaller.
The environmental pressure effect on thermal runaway and fire behaviors in the 18650 lithium-ion battery (LIB) with various cathodes and states of charge (SOC) are experimentally investigated in this work. The fire hazards were characterized by the combustion process, total mass loss (TML) and total heat release (THR). The TML and THR increase with the ascending of the SOC at two pressures. The amount of materials ejected by both LiFePO4 and LiCoO2 batteries during the combustion is slightly affected by the environmental pressure. Meanwhile, the environmental pressure has a significant influence on the combustion heat that the THR value at high pressure is relatively bigger than that at low pressure. The unit growth rate in combustion heat between the two pressures also increases with the SOC.
The safety design of systems using lithium-ion batteries (LIBs) as power sources, such as electric vehicles, cell phones, and laptops, is difficult due to the strong multiphysical coupling effects among mechanics, electrochemistry and thermal. An efficient and accurate computational model is needed to understand the safety mechanism of LIBs and thus facilitate fast safety design. In this work, a detailed mechanical model describing the mechanical deformation and predicting the short-circuit onset of commercially available 18650 cylindrical battery with a nickel cobalt aluminum oxide (NCA) system is established for the first time. The mechanical properties of anode, cathode, and separator are characterized. Based on the experiment results, the constitutive models of component materials are established and validated through numerical simulations. A detailed computational model including all components (i.e., separator, anode, cathode, winding, and battery casing) is then developed by evaluating four typical mechanical-loading conditions. Short-circuit criteria are subsequently established based on the separator failure, thereby enabling the mechanical model to predict the short circuit electrochemically. Results show that the model can describe LIB behaviors from mechanical deformation to internal short circuit. Results provide a powerful tool for the safety design of LIBs and related engineering systems.