Accelerating Rate Calorimeter Research Articles

Needle penetration studies on automotive lithium-ion battery cells: Influence of resistance between can and positive terminal on thermal runaway

Thermal runaway (TR) can be initiated by the heat dissipated from an internal short circuit (ISC). In prismatic cells, a crucial type of ISC is located between the cell can on positive potential and the first anode layer. To enhance the safety, the potential of the can could be adjusted by increasing the ISC resistance, i.e., realizing a floating can, whereas a universal automotive prismatic cell has a can on potential in contrast. This work demonstrates that the floating can mitigates the ISC current and possibly prevents ISC from leading to TR using an advanced needle penetration test. Moreover, the ISC current was quantitatively measured, proving that there is no significant ISC current between floating can and outmost anode, while the ISC with can on potential can cause TR. To demonstrate that such difference originates only from the increased resistance, the equivalence in thermal behaviors between the two types of cans was analyzed by a heat-wait-seek test in an accelerating rate calorimeter. This work provides not only a guidance on designing a safer prismatic cell but also a prospect how the optimized needle penetration test can bring a deeper insight into the internal processes of Lithium-ion cells during mechanical abuse.

Fire Characteristics of Lithium-ion Battery According to the State of Charge in an Accelerating Rate Calorimeter

Recently, the interest in ecofriendly energy as an alternative to fossil fuels, which cause climate change and sea level rise, has increased. To achieve the efficient utilization of ecofriendly energy, such as a renewable energy, considerable effort has been made to use energy storage systems (ESSs) and smart grid systems. However, many safety problems, such as battery fires caused by the increase in the use of secondary batteries, significantly limit their application scope. In this study, to investigate the fire characteristics of lithium ion batteries (LIBs), the characteristics of the spontaneous exothermic reaction and thermal runaway phenomenon that occur at each temperature of an LIB battery were investigated using an accelerating rate calorimeter. The batteries used in the experiments were standard 18650 cylindrical batteries with a capacity of 2600 mAh, and they were tested at three different state-of-charge (SOC) levels: 0%, 50%, and 100%. The type of heat generated by each experimental condition was classified into four stages, and the existence and temperature rise characteristics of each stage were investigated according to the SOC. Although thermal runaway occurred at both 50% and 100% SOC, the reaction at 50% SOC did not escalate into violent explosions like the reaction observed at 100% charging. Furthermore, the activation energies for the thermal runaway observed in the experiments conducted at 50% and 100% SOC are presented.

Online pressure and gas analysis of lithium-ion cells during abuse tests

Online pressure and gas analysis of lithium-ion cells during abuse tests Dr Carlos Ziebert, Leader of the Group Batteries – Calorimetry and Safety, KIT, explains how online venting gas analysis of batteries can be performed using a combination of battery calorimetry and online mass spectrometry. The main objective of the AnaLiBa project (Analytics of LithiumIon- Batteries) is the joint method development of a standardised sample handling process for the gas analysis of large cells by combining an accelerating rate calorimeter (ARC) and online mass spectrometry (MS). It is a part of the competence cluster Analytics/Quality Assurance (AQua) funded by the German Federal Ministry of Education and Research (BMBF). The Fraunhofer Institute for Chemical Technology coordinates the project.

Thermal stability of lithium-ion battery subjected to inhomogeneous aging

Aged battery is prone to fire accidents. Thermal stability change of battery subjected to inhomogeneous aging is studied in this manuscript by accelerating rate calorimeter. The results indicate that thermal runaway time decreases for aged batteries. Solid electrolyte interphase and lithium plating suppress and accelerate onset exothermic side reactions. Transition metal dissolution accelerates positive electrode decomposition and oxygen release. TTR of aged batteries decreases compared to fresh battery. Microscopic changes of negative electrodes for batteries cycled at high and low temperature are inhomogeneous. Tonset for batteries cycled at low temperature decreases as lithium plating covers all of the negative electrode surface. Tonset for batteries cycled at high temperature and with 100% state of charge (SOC) increases. This is the same to battery stored at high temperature. Local lithium plating affects thermal stability of battery with 100% SOC less. However, Tonset for batteries with SOC lower than 50% SOC and subjected to local lithium plating decreases compared to fresh battery. Local lithium plating accelerates onset exothermic side reactions for battery with SOC lower than 50% SOC. The results of this manuscript are important to thermal runaway prevention for batteries in their whole operation life.

Thermal decomposition characteristics and thermal safety performance evaluation of HAN-based propellant under different external environmental stimulations

This research aims to investigate thermal characteristics and assess thermal hazards of hydroxylamine nitrate (HAN)-based liquid propellant using a combination of accelerating rate calorimeter and high-pressure differential scanning calorimetry. Adiabatic experiments revealed that the exothermic reaction initiated at 115.7 °C and a rise sharply was at 128.4 °C with a maximum self-heating rate of 164.3 °C/min and the exothermic event was accompanied by a pressure rise of 3.7 bar in 0.03s. The corrected values of adiabatic temperature rise and time to maximum rate were 605.6 °C and 1.46 min, which confirms the vulnerability of the propellant to undergo a catastrophic explosion. To prevent thermal loss prevention accidents, time to maximum rate was obtained as 24 h under 111.3 °C. The apparent activation energy calculated decreased greatly with the increase of storage temperature from 25 °C to 45 °C, and so did the thermal explosion temperature (Tb) and self-accelerating decomposition temperature (TSADT). Additionally, the linear relationship between Ea and T was E = 991.7–2.7904T. The reliability of TSADT prediction was validated through slow cook-off test. Furthermore, the propellant exhibited more violent thermal decomposition under high pressure, resulting in a higher peak power. The thermokinetic parameters related to this phenomenon were identified, specifically at pressure of 4.0 MPa.

Effect of incompatible substances on the thermal stability and decomposition products of 2,2-azobisisobutyronitrile and 1,1′-azobis(cyclohexanecarbonitrile)

2,2-Azobisisobutyronitrile (AIBN) and 1,1′-azobis (cyclohexanecarbonitrile) (ABCN) are two common azo initiators in the polymerization industry. In the chemical process, incompatible substances are commonly in contact with azo initiators. However, the thermal stability and decomposition process of azo compounds may change. In this study, the effects of common incompatible substances (hydrochloric acid (HCl), sodium hydroxide (NaOH), ferric oxide (Fe2O3), and water (H2O)) on the thermal stability and decomposition products of AIBN and ABCN were investigated. Thermal activity monitor IV (TAM IV) was utilized to investigate the thermal behavior of AIBN and ABCN industrial applications and storage processes. Several parameters such as the maximum peak power (Qmax), time to maximum rate under isothermal conditions (TMRiso), and heat of decomposition (ΔHd), were used to evaluate the effect of incompatible substances on the thermal stability of AIBN and ABCN. The results show that HCl will significantly reduce the thermal stability of AIBN and ABCN and increase the thermal risk in industrial applications. Accelerating rate calorimeter (ARC) was utilized to simulate the thermal runaway of the industrial application process. The real thermal runaway behavior was obtained by correcting the ARC experimental data with thermal inertia (φ). The decomposition products affected by incompatible substances were explored by Fourier transform infrared spectrometer (FTIR). After AIBN or ABCN were mixed with the incompatible substances, in addition to the free radicals and nitrogen generated, there may be 2-propenenitrile, 2-methyl-, hydrazinecarboxamide, and 4-cyano-1-cyclohexene. The process safety parameters can provide a valuable reference for industrial loss prevention.

A comprehensive insight into the thermal runaway issues in the view of lithium-ion battery intrinsic safety performance and venting gas explosion hazards

A comprehensive understanding of thermal runaway (TR) features and battery venting gas (BVG) explosion characteristics is the critical issue of thermal hazard prevention. In this study, commercial-size lithium-ion batteries with LiFePO4 (LFP) and Li(NixCoyMnz)O2 (NCM, x from 0.5 to 0.8) cathode materials, as well as the micro-overcharged cells, are triggered to TR under adiabatic conditions using an accelerating rate calorimeter. In addition, the obtained BVG is transferred into the gas chromatograph for further component identification. Subsequently, the specific values of the intrinsic battery safety performance (TR tolerance and TR hazards) and BVG explosion risks (lower explosion limits, LEL) are calculated. The results show that, from the perspective of battery TR evolution features, LFP batteries have greater TR tolerance than NCM batteries. Moreover, the TR hazards of NCM batteries are more severe than LFP batteries and worsen with increasing nickel content, which is proved by ambient temperature and post-disaster analysis. The primary types of BVG consist of hydrogen, carbon monoxide, carbon dioxide and hydrocarbon gases for both LFP and NCM batteries. However, due to the significant amount of hydrogen and hydrocarbon gases with low LEL values, the LEL values of BVG for LFP batteries are lower than NCM batteries, demonstrating the higher deflagration risks for the former. Besides, the LEL values of NCM batteries' BVG increase with higher energy density. A single micro-overcharge leads to lower TR tolerance and TR hazards but has little effect on LEL values for NCM cells. It is obvious that the safety issues associated with LFP batteries should also be given sufficient attention to avoid system-level explosions. The quantitative evaluation results of this paper provide new ideas for battery intrinsic safety performance assessment and a clear direction for mitigation strategy of battery TR-related secondary disasters.

Curtailing the thermal runaway and ameliorating interfacial charge kinetics using electrolyte-cum-separator in Li-battery

Recently, absolute requirements for high-performing energy storage devices with high thermal stability and superior safety features keep motivating to replace conventional liquid electrolyte systems with lithium-based secondary batteries. Instead, incorporating the solid-state electrolytes can be an elegant strategy; however, the solid electrolyte's poor interfacial kinetics and brutal ceramic nature are the significant hitches for commercial battery manufacturing. Considering these critical issues, an electrolyte cum separator (ECSP) membrane composed of robust polymer and high ion-conducting ceramic has been rationally designed to improve interfacial ion kinetics during electrochemical cycling. The electrolyte-cum-separator (ECSP) attains high thermal endurance (150 °C), superior mechanical strength, and excellent wettability to commercially available systems. Further, the ECSP ensures low interfacial resistance against the Li metal even at a high current density, that let to prevent the dendritic growth and short-circuiting of the battery. The ECSP membrane-enabled batteries demonstrate excellent discharge capacity with high potential cathode and metal anodes that outperform those batteries assembled from commercial electrolyte and separator systems. Moreover, the thermal stability of the ECSP membrane using the accelerating rate calorimeter (ARC) has also been investigated. The excess flammable solvent and lower thermal endurance of the commercial electrolyte separator system are responsible for the batteries' thermal runaway. Additionally, the full-cell performance composed of a commercial cathode (Li(NixCoxMnx)O2, x =1/3), anode (MCMB), and the ECSP membrane manifests good cycle life and stable capacity retention. Therefore, the fabrication of electrolyte-cum-separator is a prominent strategy to achieve flexible, dendrite-free, and high-performing solid-state Li metal as well as Li-ion battery technologies for high-end applications.

In-situ calibration method for thermocouples in accelerating rate calorimeter based on multiple fixed-points and Joule heat

To solve the problem of temperature drift of thermocouples in accelerating rate calorimeter caused by long-term operation, an in-situ calibration method based on multiple fixed-points and Joule heat is proposed in this article. Firstly, the heat transfer model of the calorimeter is established, and the validity of the method is verified by numerical simulation. Secondly, a multiple fixed-points graphite calibrator and a cylindrical electronic resistance element are designed. Finally, the in-situ calibration is carried out. The calibration results show that the maximum permissible measurement error of the sample thermocouple after calibration is better than 0.220 °C and that the bias of consistency in-situ calibration method is smaller than 0.110 °C. In addition, a di‑tert‑butyl peroxide in toluene solution with a mass percent of 20% is selected as the experimental sample. The sample experiment results show that the kinetic and thermodynamic parameters are closer to the reference values after thermocouples calibration.

Runaway reaction investigation of di‑tert‑butyl peroxide using adiabatic calorimetry

Thermal safety assessment is an effective means to put an end to frequent chemical accidents. The conventional safety assessment generally uses differential scanning calorimetry (DSC) or accelerating rate calorimeter (ARC), while in this work the adiabatic calorimetry technique is applied to study the thermal runaway reaction for the first time. Adiabatic calorimeter (AC) has an excellent adiabatic and vacuum environment, and the process simulation of adiabatic runaway is more real in theory. The thermal decomposition reaction of 20% di‑tert‑butyl peroxide (DTBP) /toluene solution was measured, and the kinetic parameters and model of DTBP decomposition in the adiabatic reaction process were obtained by fitting the temperature rise rate-temperature data in the thermal runaway process. These research results not only show that the adiabatic calorimetry is competent for the determination and thermal risk assessment of adiabatic runaway reactions, but also provide an important reference for broadening the application of adiabatic calorimetry.

Research on the thermal hazard characteristics of 1-propyl-3-methylimidazolium nitrate and risk assessment

The application of ionic liquids is prevalent in various industries, including pharmaceutical, chemical, and aerospace, especially in environments with high temperatures. Thus, the importance of researching the characteristics and mechanism of the pyrolysis hazard of ionic liquids cannot be overemphasized. This research presents a systematic study of a new versatile ionic liquid, 1-propyl-3-methylimidazolium nitrate ([Pmim][NO3]). The flash-ignition temperature, thermal decomposition and thermal runaway characteristics of [Pmim][NO3] were analyzed using various techniques, including thermogravimetric analyzer, differential scanning calorimetry, flash-ignition temperature tester, and accelerating rate calorimeter, for determining its major hazard characteristics. The main thermodynamic and safety parameters, as well as the reaction pattern of the pyrolysis process, were obtained. Additionally, an assessment was conducted to determine the potential occurrence and seriousness of a runaway reaction of [Pmim][NO3] decompose. The present study is of significant importance in improving the intrinsic safety level of ionic liquids in the processes of synthesis, utilization, storage, and transportation.

The suppression performance of fluorinated cooling agents on the Lithium-ion Batteries fire based on the Accelerating Rate Calorimeter (ARC)

Lithium-ion Batteries (LIB) fire has attracted a wide attention since it threatens the application limitation of LIB. The combustible gases are producted during the LIB thermal runaway. When the immersion cooling technology is used for LIB thermal management, the mixiture of combustible gases and fluorinated cooling agents in a confined space could result in a big explosion due to the LIB thermal runaway. With an aim to have a deep understanding regarding the influence of fluorinated immersion cooling agents on the fire suppression performance, a series of tests were conducted to obtain the profile of critical temperature and pressure based on the accelerating rate calorimeter (ARC). Duing the tests, the cylindrical 18,650 LIB is heated under insulated environment firstly. Then several typical fluorinated cooling agents are selected to clarify the fire suppression performance of LIB thermal runaway. The results and discussion indicate that the utilization of HT (hexafluoropropene trimer) agent has a peak pressure 0.6 Mpa and a peak temperature 823 ℃ during LIB thermal runaway. The suppression results varying seven typical fluorinated cooling agents are discussed. BTP (2-BroMo-3,3,3-triflouro propene) shows an obvious suppression effect because it results in a low pressure ratio.The suppression mechnasim of agents on the LIB thermal runaway is discussed and presented. It could provide a insight into the development of new fluorinated agents for suppression.

Thermal and Mechanical Safety Assessment of Type 21700 Lithium-Ion Batteries with NMC, NCA and LFP Cathodes–Investigation of Cell Abuse by Means of Accelerating Rate Calorimetry (ARC)

In this experimental investigation, we studied the safety and thermal runaway behavior of commercial lithium-ion batteries of type 21700. The different cathode materials NMC, NCA and LFP were compared, as well as high power and high energy cells. After characterization of all relevant components of the batteries to assure comparability, two abuse methods were applied: thermal abuse by the heat-wait-seek test and mechanical abuse by nail penetration, both in an accelerating rate calorimeter. Several critical temperatures and temperature rates, as well as exothermal data, were determined. Furthermore, the grade of destruction, mass loss and, for the thermal abuse scenario, activation energy and enthalpy, were calculated for critical points. It was found that NMC cells reacted first, but NCA cells went into thermal runaway a little earlier than NMC cells. LFP cells reacted, as expected, more slowly and at significantly higher temperatures, making the cell chemistry considerably safer. For mechanical abuse, no thermal runaway was observed for LFP cells, as well as at state of charge (SOC) zero for the other chemistries tested. For thermal abuse, at SOC 0 and SOC 30 for LFP cells and at SOC 0 for the other cell chemistries, no thermal runaway occurred until 350 °C. In this study, the experimental data are provided for further simulation approaches and system safety design.

Change of safety by main aging mechanism – A multi-sensor accelerating rate calorimetry study with commercial Li-ion pouch cells

The safety of Li-ion batteries is the most critical of many important characteristics and must be carefully considered. However, depending on the aging conditions, safety of batteries can change drastically. We had recently introduced ARC-MS as a new tool for safety investigations, which is an updated accelerating rate calorimeter (ARC) combined with a mass spectrometer (MS). Additionally, our ARC-MS setup is equipped by seven more low cost sensors (temperature, voltage, resistance, audio, strain, and transmitted and reflected ultrasound). In this paper, the dependence of safety on the dominant aging mechanism as a function of aging temperature, and state-of-health (SOH) is investigated on the example of 3.3 Ah commercial pouch cells. The ambient temperature during aging has a strong influence on the dominant aging mechanism (Li plating or SEI growth) of this cell as shown by Arrhenius plots of the aging rate and Post-Mortem analyses (ICP-OES, SEM, EDX, Hg porosimetry, STA) of aged cells. Our in-depth evaluation shows that different sensors can provide indications of safety relevant events (onset of swelling, onset of self-heating, cell venting, stable exothermic reactions, separator melting, and thermal runaway) in the cells independently. Combining these low-cost sensors might be a solution for detection of unsafe cells in applications.

Thermal stability and decomposition mechanism analysis of 1, 1’-Azobis(cyclohexanecarbonitrile) by STA, DSC, ARC and TG-FTIR

1, 1′-Azobis(cyclohexanecarbonitrile) (ABCN) is a kind of azo compound, which is widely used as an initiator in the polymer industry. Plenty of heat will be released during the thermal decomposition, and fire or explosive accidents could happen when the cooling system of the polymerization reactor fails. In this manuscript, the thermal decomposition behavior of ABCN under a dynamic temperature environment was investigated by simultaneous thermogravimetric analyzer (STA). Differential scanning calorimeter (DSC) was used to detect the thermal effects of different stages of mass loss. The apparent activation energy was calculated by Kissinger-Akahira-Sunose methods (K-A-S methods). The thermal runaway behavior was investigated by accelerating rate calorimeter (ARC), which was used to predict time to maximum rate under adiabatic condition (TMRad). The results show that the temperatures at TMRad = 8 h and 24 h are 93.0 °C and 89.7 °C, respectively. The self-accelerating decomposition temperature (SADT) is 86.6 °C, which is calculated based on the thermal theory of Semenov. Since ABCN is used at 60–90 °C, a major accident could happen when the heat accumulated in the reactor is not removed timely. The risk of thermal runaway reactions for ABCN was defined against the risk matrix as level Ⅲ, which is an unacceptable risk. The carbon radicals and nitrogen were released during the decomposition of ABCN based on the experiment result of thermal gravimetric analyzer-Fourier transform infrared spectrometer (TG-FTIR) system. Several safety assessment parameters could supply references for the industry to alleviate thermal hazards and prevent critical incidents.

Thermal Behaviors and Interaction Mechanism of Ammonium Dinitramide with Nitrocellulose.

The initial interaction mechanism is very important for the design and safety of nano-scale composite energetic materials composed of ammonium dinitramide (ADN) and nitrocellulose (NC). The thermal behaviors of ADN, NC and an NC/ADN mixture under different conditions were studied by using differential scanning calorimetry (DSC) with sealed crucibles, an accelerating rate calorimeter (ARC), a self-developed gas pressure measurement instrument and a DSC-thermogravimetry (TG)-quadrupole mass spectroscopy (MS)-Fourier transform infrared spectroscopy (FTIR) combined technique. The results show that the exothermic peak temperature of the NC/ADN mixture shifted forward greatly in both open and closed circumstances compared to those of NC or ADN. After 585.5 min under quasi-adiabatic conditions, the NC/ADN mixture stepped into the self-heating stage at 106.4 °C, which was much less than the initial temperatures of NC or ADN. The significant reduction in net pressure increment of NC, ADN and the NC/ADN mixture under vacuum indicates that ADN initiated the interaction of NC with ADN. Compared to gas products of NC or ADN, two new kinds of oxidative gases O2 and HNO2 appeared for the NC/ADN mixture, while NH3 and aldehyde disappeared. The mixing of NC with ADN did not change the initial decomposition pathway of either, but NC made ADN more inclined to decompose into N2O, which resulted in the formation of oxidative gases O2 and HNO2. The thermal decomposition of ADN dominated the initial thermal decomposition stage of the NC/ADN mixture, followed by the oxidation of NC and the cation of ADN.

Experimental investigation on thermal runaway suspension with battery health retention

With growing applications of Li-ion batteries in ground transportation and energy storage, thermal runaway of Li-ion batteries has become a major concern for energy and public safety. Existing studies on thermal runaway mitigation methods are largely passive, in that most of them focus on propagation mitigation and fire extinguish after thermal runaway has been triggered. In this work, we presented experimental results on thermal runaway suspension with battery health retention, for the first time. By analyzing the temperature and voltage evolution of commercial 18,650 cells with Lithium iron phosphate chemistry during step-heating thermal runaway test in an accelerating rate calorimeter, it is found that the voltage signal has a sudden drop corresponding to a similar temperature of 135 °C, before the occurrence of thermal runaway. Thermal runaway suspension experiments are then conducted by activating cooling when either the voltage drop or the target temperature signal is reached. It is observed that thermal runaway suspension from the target voltage drop signal fails to prevent the battery from further damage, even with fast liquid N2 cooling. For thermal runaway suspension at the temperature signal 130 °C, batteries are successfully saved regardless of fast cooling with liquid N2, or slow cooling using N2 gas. Further electrical impedance spectrum testing shows that the batteries survived from thermal runaway suspension have increased bulk resistance while polarization resistance remains unchanged. The cycling performance of the saved batteries has demonstrated identical voltage but reduced capacity by around 20 %. This research can provide useful guidance on thermal runaway prevention and health retention of Li-ion batteries.

Comprehensive analysis on aging behavior and safety performance of LiNixCoyMnzO2/graphite batteries after slight over-discharge cycle

Over-discharge is one of the common abuse conditions for lithium-ion batteries (LIBs), while the safety hazard of over-discharged cell is still unclear. In this work, the aging behavior and safety performance of commercial Li(Ni0.5Co0.2Mn0.3)O2/graphite LIBs under 1.5, 1.0, 0.5, and 0.0 V over-discharge cycles are investigated. The cells experience capacity decay and structural damage during over-discharge cycle. Compare to the normal cycled cells, the increased impedance after over-discharge cycle leads to more heat generation during operating, which further accelerates the inconsistency of LIB module. Moreover, the thermal runaway behavior of the over-discharged cell was studied using Extended Volume Accelerating Rate Calorimeter. The kinetics of self-heating reaction is obtained, and the criticality of thermal runaway under different heat dissipation conditions was analyzed based on Semenov model. The thermal stability and maximum safe storage temperature of the LIB were decreased after over-discharge cycle, especially for the cell over-discharged to 0.0 V. Based on the electrochemical impedance spectroscopy, the loss of lithium inventory relate to the growth of solid electrolyte interphase (SEI) film is found to be the primary aging contribution. Moreover, the post-mortem test implied the dissolution of Cu initiated when over-discharged to 0.5–0.0 V.

Thermal hazard risk and decomposition mechanism identification of 1-Hexyl-2,3-dimethylimidazolium nitrate: Combined thermal analysis experiment and DFT emulation

Ionic liquids are extensively used in pharmaceutical, chemical and aerospace fields, and sometimes used in high temperature environments. Investigating the pyrolysis hazard characteristics and mechanism of ionic liquids is significant. 1-Hexyl-2,3-dimethylimidazolium nitrate ([Hmmim][NO3]) as a new versatile ionic liquid has been systematically studied in this paper. The pyrolysis characteristics of [Hmmim][NO3] in different conditions are researched by using thermogravimetric analyzer, differential scanning calorimetry and accelerating rate calorimeter technologies. Main thermodynamic parameters, safety parameters, and reaction pattern of [Hmmim][NO3] pyrolysis process are acquired. The severity degree and possibility of [Hmmim][NO3] runaway reaction is evaluated, which may result in serious damage to the plant. The microscopic mechanism of [Hmmim][NO3] pyrolysis has been explored comprehensive utilization thermogravimetry-flourier transform infrared spectroscopy, thermogravimetric-photoionization mass spectrometry and quantum-chemical simulation. The primary noxious gas and reaction steps leading to the thermal hazards of [Hmmim][NO3] are confirmed. This research provides a theoretical basis for improving the intrinsic safety of [Hmmim][NO3] application and formulating corresponding safety preventive measures.

Experimental and modeling investigation on the gas generation dynamics of lithium-ion batteries during thermal runaway

The gas generation and rupture are the special features of the thermal runaway (TR) of lithium-ion batteries (LIBs). The LIB’s gas generation dynamics during TR are investigated using the extended-volume accelerating rate calorimeter and a gas-tight canister. The pressure within canister is measured, and the internal gas could be regarded as a lumped system before TR thanks to the adiabatic condition. The pressure increase is about 100 kPa at the safety valve opening, and the corresponding gas release is approximately 10 mmol. For 100% SOC cells, the peak pressure recorded before the canister pressure relief is 2.566 MPa. The gas generation rate is approximately proportional to the temperature increase rate, which facilitates the simulation on the gas generation because temperature is easier to measure. The gas generation process can be divided into different stages, and the multi-stage kinetics parameters (Frequency factor and activation energy) of the gas generation process are calculated, which predict the evolution of internal pressure and rupture behavior of LIB under external heating condition. • Gas generation dynamics of Li-ion battery during thermal runaway is investigated. • Relationship between gas and heat producing rates is revealed. • Multi-stage kinetics parameters help predict the pressure and venting.