Query: lithium ion failure

title: Generalized separator failure criteria for internal short circuit of lithium ion battery
abstract: To enable the understanding of the internal short circuit mechanism triggered by separator failure, mechanical indentation loadings are designed to create the deformation of the separator in a precisely controllable way. Herein, two characteristic short circuit types are observed in anode separator cathode stack upon mechanical abusive loading, i.e. rapid and gentle voltage drop. Through the ex situ experiment, the rapid voltage drop is due to the direct contact between cathode and anode as a result of separator fracture, while the gentle voltage drop is related to the flattening of the separator with the absence of its function to isolate electron transfer. The developed detailed numerical models, considering the failure of anode and cathode and the anisotropy of separator, can well describe the mechanical responses of components and stack. Thanks to the numerical computation model and computation, we establish and validate the generalized short circuit criteria for the two representative failure modes based on the volumetric strain and equivalent strain of separator. Results provide a powerful and generalized tool aiming for the design of next generation separator technology, enabling a more fundamental and effective way for future ISC detection, monitoring, and evaluation which can be embedded within the battery management system.

title: Simultaneous measurement of multiple thermal hazards associated with a failure of prismatic lithium ion battery
abstract: Lithium ion batteries (LIBs) are efficient, high density electrical energy storage devices utilized in a perpetually increasing range of applications. One of the weaknesses of LIBs is that a small deviation from the normal operating conditions may cause an irreversible failure accompanied by a rapid self heating and ejection of combustible gases and aerosols. The information on how much energy is released upon failure is critical for design of energy storage systems. In the current study, a novel technique, Copper Slug Battery Calorimetry (CSBC) was combined with oxygen consumption calorimetry to measure the rate of heat generated inside an LIB cell (PIHG) and the rate of heat generated as a result of combustion of ejected battery materials (PFlaming) A short duct equipped with a perforated plate was added to the original design of the CSBC apparatus to collect gases and aerosols ejected from the cell, reduce their flow speed and deliver them to a hot wire igniter, which was used to initiate a diffusion flame. The exhaust from this flame was collected to measure the oxygen consumed in the combustion process and compute PFlaming. This approach to handling the ejected materials increased their combustion efficiency and eliminated thermal feedback from the flame to the cell, which enabled simultaneous measurement of PIHG and PFlaming. The new setup was employed to investigate thermally induced failure of an 1880 mA h prismatic LIB at various states of charge (SOC) It was determined that, at 100% SOC, this LIB released 33 1.0 kJ of energy into the body of the cell and 113 19 kJ was produced as a result of combustion of the ejected battery materials. The latter value is significantly greater than those previously reported for similarly sized cells, which can be explained by a more complete combustion achieved in this new apparatus.

title: Overcharge behaviors and failure mechanism of lithium ion batteries under different test conditions
abstract: Overcharge is one of the most severe safety problems for the large scale application of lithium ion batteries, and in depth understanding of battery overcharge failure mechanism is required to guide the safety design of battery systems. In this paper, the overcharge performance of a commercial pouch lithium ion battery with Liy(NiCoMn)1/3O2 LiyMn2O4 composite cathode and graphite anode is evaluated under various test conditions, considering the effects of charging current, restraining plate and heat dissipation. Charging current is found to have only minor influences on battery overcharge behaviors, whereas the battery overcharged with pressure relief design (restraining plate and cuts on pouches) and good heat dissipation shows significantly improved overcharge performance and can endure larger amount of overcharge capacity and higher temperature before thermal runaway. Characterizations on cathode and anode materials at different overcharge states are carried out to identify the side reactions inside the battery. The overcharged cathode suffers from electrolyte decomposition, transition metal dissolution and phase transition, but still exhibits no obvious exothermic behaviors before thermal runaway occurs. Severe lithium plating happens on the anode, and would accelerate the overcharge induced thermal runaway process. Further analysis on the onset temperature of thermal runaway helps to reveal the overcharge induced thermal runaway mechanism of lithium ion batteries. The result shows that rupture of the pouch and separator melting are the two key factors for the initiation of thermal runaway during overcharge process.

title: Deformation and failure of lithium ion batteries treated as a discrete layered structure
abstract: Safety of lithium ion batteries under mechanical loadings is currently one of the most challenging and urgent issues facing in the Electric Vehicle (EV) industry. The architecture of all types of large format automotive batteries is an assembly of alternating layers of anode, separator, and cathode. The anode is composed of a very thin copper foil double side coated with graphite powders, while the cathode is an aluminum foil with the active material coating. Each of the five components may develop a large plastic deformation until fracture. This study focuses on the effect of the properties of the coated materials on the local and global responses of a battery cell. Both anode and cathode coatings are described by the Drucker Prager/Cap plasticity model, which is carefully calibrated through axial and lateral compression tests and closed die compaction test. A separate experimental effort is put on finding the strength of the interface between the foils and the granular materials with a binder. The main new finding is that in the cases of plane strain and axisymmetric loadings, the failure of cells proceeds in two stages. First, the shear bands localize along discrete lines. Then, fracture develops inside the shear bands due to large local strain gradient. The present model is applied to study the deformation and strength of large format pouch cells subjected to local indentations by rigid punches. The prediction of the present model follows closely the measured load displacement curve and captures with good accuracy the magnitude of the peak load and the corresponding critical displacement. In addition, an excellent correlation is achieved between the calculated profile of the through thickness crack and the result of the micro CT scan. The present detailed computational model should be useful in the battery design process and will serve as an important new computational tool for assessing the safety of lithium ion batteries against mechanical loading.

title: Modelling and experiments to identify high risk failure scenarios for testing the safety of lithium ion cells
abstract: Intentionally inducing worst case thermal runaway scenarios in Li ion cells on demand is a definitive way to test the efficacy of battery systems in safely mitigating the consequences of catastrophic failure. An internal short circuiting (ISC) device is implanted into three 18650 cell designs: one standard, one with a bottom vent, and one with a thicker casing. Through an extensive study of 228 cells, the position at which thermal runaway initiates is shown to greatly affect the tendency of cells to rupture and incur side wall breaches at specific locations. The risks associated with each failure mechanism and position of the ISC device are quantified using a custom calorimeter that can decouple the heat from ejected and non ejected contents. Causes of high risk failure mechanisms, such as bursting and side wall breaches, are elucidated using high speed synchrotron X ray imaging at 2000 frames per second and image based 3D thermal runaway computational models, which together are used to construct a comprehensive description of external risks based on internal structural and thermal phenomena.

title: Analysis of mechanical failure at the interface between graphite particles and polyvinylidene fluoride binder in lithium ion batteries
abstract: The capacity fade corresponding to the mechanical failure of active materials is one of hurdles to overcome in the widespread of echo friendly vehicles. However, the mechanisms of the mechanical failure at the electrode are not fully understood. In this study, the initiation and propagation of debonding at the interface between an active particle and a binder are investigated using a coupled electrochemical mechanical and cohesive zone finite element model. The effects of particle sizes and lithiation kinetics on the progressive growth of interfacial debonding are studied, and critical states of charges are determined. The normal and shear tractions at the interface are systematically analyzed to understand their role in debonding behavior. The simulation results show that the interfacial debonding is less likely to happen as the particle size and C rate increase, which is opposite to the inner particle fracture behavior. The numerical study indicates that there is a trade off between the inter particle failure and inner particle fracture. This study suggests that the binder effect needs to be included in the theoretical model for better understanding of the mechanical failure at the electrode. The debonding failure maps provided from the study can assist in engineering design of active materials and safe operation of batteries.

title: Dynamic impact response of lithium ion batteries, constitutive properties and failure model
abstract: Use of lithium ion batteries in transportation necessitates understanding of the cell mechanical response in case of a vehicle accident. Many researchers have access to test equipment to characterize the behavior of cells at low speeds. However, testing batteries at high speeds requires special setups that are not available for many interested parties. In this research, a methodology is proposed for predicting the material response and failure patterns of lithium ion batteries subjected to high impact based on the experimental results at lower velocities. For this purpose, a constitutive law was proposed and parameters were calibrated for two types of lithium ion cells, pouch and elliptical. Test results at lower impact velocities (up to 0.5 m s 1) were used for calibrating the constitutive response and the failure criteria. The test data at higher impact velocities of up to 5 m s 1 were used for validation. A Johnson Cook type strain rate sensitivity model could successfully capture the strain rate hardening response of both cell types. Finite element models were developed for each cell type and empirical linear relationships were found between failure strain and strain rate. For the case of pouch cells, this correlation was negative, whilst there was a positive correlation for elliptical cells. The FE models closely followed the experiments in terms of load displacement behavior and predicted the peak load and punch displacement at the onset of short circuit with good accuracy.

title: Performance degradation due to anodic failure mechanisms in lithium ion batteries
abstract: We report a mechano chemical model for anodic degradation during fast charging of nickel manganese cobalt (NMC)/graphite (C) cell due to SEI growth, lithium plating/stripping, dead lithium storage, and film fracture of composite SEI and plated lithium film. Degradation of the battery is analyzed for a range of charging rates from 1 to 6 C rates, and the influence of plating mechanisms lithium plating and dead lithium deposition and recovery during stripping on the film resistance of the anode are accounted for in the model. Dynamic evolution of the interfacial properties is modeled using rule of mixture approach. Model predictions of plating associated stress fields are used to compute critical energy release rate for film cracking. The results indicate an increased tendency of fracture for thinner SEI film with lithium plating at higher charging rates. The process of reforming the cracked film absorbs a significant portion of the electrode current thereby reducing the cell capacity and plating efficiency. The mechano chemical model provides an extensive analytical framework for understanding the synergistic coupling of anodic degradation mechanisms, prognosticating conditions of SEI failure, and evaluating the capacity fade and efficiency of lithium ion battery.

title: Deformation and Failure Behavior of Cylindrical Lithium Ion Batteries Subjected to Mechanical Loading

title: THERMAL BEHAVIOR OF LITHIUM ION BATTERIES: AGING, HEAT GENERATION, THERMAL MANAGEMENT AND FAILURE
abstract: This work presents a succinct review of the thermal behavior of lithium ion batteries (LIBs) and its relationship with aging, heat generation, thermal management and thermal failure. This work focuses on the temperature effects that promote the main aging mechanisms in the anode and compare these effects among different cell chemistries for calendar and cycling aging modes. We review the strategies to mitigate aging, including the design of the battery thermal management system (BTMS) best practices of battery users to minimize the effect of stress factors, and the appropriate selection of the anode material. We discuss the heat generation and surface temperature variations in LIBs, including comparisons among different cell chemistries. We analyze the thermal failure of LIBs due to extreme events that cannot be countered by the BTMS, such as overcharge. Finally, the main challenges and opportunities related to the impact of the thermal behavior of LIBs on their performance and life cycle are identified, including trends in anode material selection, BTMS design, and fast charging methods.