Accelerating Rate Calorimeter Research Articles

Evaluation of the thermal hazard and pyrolysis mechanism of 1-allyl-3-methylimidazole nitrate and 1-propyl-3-methylimidazole nitrate via thermal analysis and DFT calculation: Effect of structural characteristics

Imidazole ionic liquid, as a green solvent, is one of the most widely used ionic liquids. Understanding its thermal safety characteristics and mechanism is the essential basis for its safe application. In this paper, the thermal hazard characteristics of two ionic liquids with typical structural characteristics are systematically studied, which were 1-allyl-3-methylimidazole nitrate and 1-propyl-3-methylimidazole nitrate ionic liquids. The thermal decomposition peculiarities of two ionic liquids were systematically analyzed by thermogravimetric analyzer, differential scanning calorimetry and accelerating rate calorimeter techniques, and the risk of thermal runaway is also evaluated. In addition, the pyrolysis products and microscopic pyrolysis mechanism of ionic liquids were studied via thermogravimetry-Fourier transform infrared spectroscopy, thermogravimetric mass spectrometry and density functional theory calculation, and the essential mechanism of thermal hazard were determined. The influence of substituent structure on the thermal hazard characteristics of imidazole nitrate ionic liquid was preliminarily analyzed from macroscopic experiment and microscopic mechanism two aspects. This study provides a theoretical basis for the safe application, design and development of imidazole nitrate ionic liquids.

Effect of fast charging on degradation and safety characteristics of lithium-ion batteries with LiNixCoyMnzAl1-x-y-zO2 cathodes

Fast charging compatibility is an important technical aspect required of advanced lithium-ion (Li-ion) batteries to lead the revolution and increase the adoption of electric vehicles. Although substantial material-level innovations have greatly promoted the widespread employment of fast charging rates for Li-ion batteries, the unfavorable rapid degradation and cell-level thermal instability are still bottlenecks for commercial success. In this study, fast-charging induced aging mechanisms and thermal safety characteristics of Li-ion batteries with quaternary energy-dense LiNixCoyMnzAl1-x-y-zO2 (NCMA) cathodes are comprehensively investigated. Promising fast-charge strategies under different thermal environments are applied to reveal their specific adverse side effects on electrochemical performances and cell lifetime. Post-mortem analysis is conducted to understand the distributions, microstructures, and chemical states of electrodepositions on cell components. Cell-level thermal safety evaluations are carried out based on accelerating rate calorimeter tests to determine evolutions of thermal safety hazards as a result of imposed fast charging conditions. This research highlights the significant role of lithium plating and aluminum dissolution in accelerating the thermo-electrochemical failure of the chosen NCMA-based Li-ion chemistry, providing new insights on degradation-safety interactions and effective mitigation strategies under fast charging conditions.

An Electrode-Crosstalk-Suppressing Smart Polymer Electrolyte for High Safety Lithium-Ion Batteries.

Electrode crosstalk between anode and cathode at elevated temperatures is identified as a real culprit triggering the thermal runaway of lithium-ion batteries. Herein, to address this challenge, a novel smart polymer electrolyte is prepared through in situ polymerization of methyl methacrylate and acrylic anhydride monomers within a succinonitrile-based dual-anion deep eutectic solvent. Owing to the abundant active unsaturated double bonds on the as-obtained polymer matrix end, this smart polymer electrolyte can spontaneously form a dense crosslinked polymer network under elevated temperatures, effectively slowing down the crosstalk diffusion kinetics of lithium ions and active gases. Impressively, LiCoO2/graphite pouch cells employing this smart polymer electrolyte demonstrate no thermal runaway even at the temperature up to 250°C via accelerating rate calorimeter testing. Meanwhile, because of its abundance of functional motifs, this smart polymer electrolyte can facilitate the formation of stable and thermally robust electrode/electrolyte interface on both electrodes, ensuring the long cycle life and high safety of LIBs. In specific, this smart polymer electrolyte endows 1.1AhLiCoO2/graphite pouch cell with a capacity retention of 96% after 398 cycles at 0.2 C.

Study of thermal decomposition mechanism of methylene diphenyl diisocyanate (MDI) through accelerating rate calorimeter and theoretical approach

Study of thermal decomposition mechanism of methylene diphenyl diisocyanate (MDI) through accelerating rate calorimeter and theoretical approach

Experimental Study on Low-Temperature-Oxidation Parameters and Simulations of Exothermic Process during Air Injection in Light Oil Reservoirs

Summary The thermal development process for light oil reservoirs using air injection technology is to release heat through low-temperature oxidation (LTO) between the injected air and crude oil and gradually increase the reaction zone’s temperature to displace crude oil. However, existing LTO experimental methods for air injection do not adequately capture the characteristics of LTO and struggle to directly obtain LTO kinetic parameters at low temperatures. In this paper, we used light oil samples from the Huabei Oilfield, China, as the studied objects and proposed innovative methods for obtaining and calculating LTO kinetic parameters. Further, we validated the feasibility of the proposed methods through experimental and numerical simulations. The results indicate that the lower limit temperature at which oxidation parameters can be directly measured through the accelerating rate calorimeter (ARC) experiments is 124°C. We matched the calculations from the ARC experiment curve-extension method for kinetic parameters with the results from both the high-pressure thermogravimetric analyzers (HP-TGA) experiment and the ramped thermal oxidizer (RTO) experiment. The fit between these results indicates that three methods are suitable for obtaining LTO parameters and can be used to derive chemical equations for LTO reactions in numerical simulation models. The simulation results from the reservoir scale indicate that, following air injection into the light oil reservoir, the peak temperature at the leading edge of the high-temperature zone reaches 370.9°C. The interaction between crude oil and air remains in the LTO phase, facilitating a sustained thermal accumulation within the reservoir. This study can provide a reference for reservoir development under similar conditions.

Thermal runaway of Li-ion battery with different aging histories

Safety issues associated with thermal runaway (TR) in batteries have attracted extensive research attention. However, understanding and predicting TR encounter significant challenges due to the complexities of chemical reactions, venting events, thermal stratification, multiphase interactions, and variable boundary conditions. These challenges are further complicated by intrinsic battery degradation, a phenomenon often insufficiently characterized and governed by multiple mechanisms. These primarily include the depletion of electrolyte and active materials, thickening of the solid-electrolyte-interphase (SEI), and formation of lithium plating and dendrites. Such degradation alters the battery's materials and structure, directly causing electrochemical performance penalties and potentially affecting its TR behavior. This study examines the TR behavior of commercial 18,650 cells with lithium nickel manganese cobalt oxide (NMC) cathodes, focusing on degradation associated typical usage scenarios: long-term cycling, low-temperature cycling, dynamic cycling with calendar aging. We employ Electrochemical Impedance Spectroscopy (EIS) to probe internal changes in the electrochemical properties of aged cells compared to fresh counterparts. The EIS results reveal pronounced SEI impedance and substantially increased charge transfer impedance in long-term cycled cells. TR tests were conducted using an Accelerating Rate Calorimeter (EV+ ARC, Thermal Hazard Technology) following the heat-wait-seek (HWS) strategy. Our findings indicate a significant impact of aging mechanisms on second-life battery safety. Specifically, cells subjected to low-temperature cycling demonstrated a considerably lower onset temperature for exothermic reactions, and shorter TR delay time, despite all aged cells showing similar state of health (SOH). Furthermore, the temperature corresponding to the cell voltage drop is consistently much lower for aged cells with dynamic cycling and calendar aging.

Influence of cathode materials on thermal characteristics of lithium-ion batteries.

In this work, the thermal stability of four types of 18,650 lithium-ion batteries with LiCoO2 (LCO), LiFePO4 (LFP), LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiNi0.8Co0.15Al0.05O2 (NCA) materials as cathodes are experimentally investigated by the accelerating rate calorimeter (ARC) and the isothermal battery testing calorimeter (iso-BTC) under adiabatic and isothermal conditions, respectively. The thermal runaway danger level of these batteries can be ranked as LCO > NCA > NCM811 >> LFP by judging from the values of Tmax and HRmax, nominal. The higher the nickel and cobalt content, the higher the lithium-ion battery capacity, but the worse the thermal stability. The Qtotal of NCA is the largest in the complete standard charge and discharge process, due to that the capacity of NCA is significantly higher than that of the other three batteries, resulting in remarkable increase in Qirre proportioned to the square of the current. When the ambient temperature rises, the energy release decreases owing to the decrease in the internal resistance of the battery. These studies are expected to have important implications for the subsequent safe design of commercial lithium-ion batteries with different cathode materials.

Thermal hazard evaluation and risk assessment of 1-allyl-3-methylimidazole nitrate ionic liquid

Imidazole ionic liquids (ILs) have broad application prospects in batteries and other fields. Researching the thermal decomposition features of ILs holds paramount importance for the application in battery electrolyte. 1-allyl-3-methylimidazole nitrate ionic liquid (IL) as a new functional IL, and its related thermal decomposition properties are unknown. In this paper, the thermal decomposition peculiarities of 1-allyl-3-methylimidazole nitrate IL were systematically analyzed by thermogravimetric analyzer, differential scanning calorimetry, and accelerating rate calorimeter techniques, and the relevant thermodynamic parameters and thermal decomposition models were derived. In addition, 1-allyl-3-methylimidazole nitrate IL possesses strong thermal runaway characteristics and the risk of thermal runaway is also evaluated. The main gaseous products formed by the pyrolysis of 1-allyl-3-methylimidazole nitrate IL was detected and analyzed by thermogravimetry-Fourier transform infrared spectroscopy and thermogravimetric-photoionization mass spectrometry techniques. The results showed that flammable gas, toxic gas, and asphyxiating gas are formed during the pyrolysis of 1-allyl-3-methylimidazole nitrate IL. This study lays a theoretical foundation for the safe application and the formulation of corresponding safety protection measures of 1-allyl-3-methylimidazole nitrate IL.

Investigation on gas generation and corresponding explosion characteristics of lithium-ion batteries during thermal runaway at different charge states

This study investigates the gas generation characteristics and explosion limits of the gas generated by 18650-type LiNi1/3Co1/3Mn1/3O2 (NCM) cells during thermal runaway (TR) at different states of charge (SOCs). An accelerating rate calorimeter is employed to initialize TR, together with an airtight jar for gas measurement. Based on the detected gas composition for NCM cells, the corresponding explosion limits are computed and further compared with those of LiFePO4 (LFP) and LiNi0.80Co0.15Al0.05O2 (NCA) cells. The results reveal that the gas generation rates are slightly higher for NCM cells with lower SOCs prior to the violent TR processes compared to those for high-SOC cells, primarily due to the elevated reaction temperature. Moreover, during violent TR, multiple-peak features are observed for the gas generation rate curves, especially at high-SOC conditions. On the other hand, typical Z-shaped explosion limit curves are observed for all generated mixtures. As the cathode material varies from NCM to LFP and NCA, the explosion limits shift from high-temperature regions to low-temperature regions. In contrast to common beliefs that the generation gas at high SOCs is more explosive, non-monotonic responses of the explosion limit curves are found with respect to cell SOC. The significance of minor components of the generated gas, including ethylene and ethane, in reducing the explosivity of the mixture, is highlighted through sensitivity analyses.

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.