Thermal Runaway Phenomenon Research Articles

Thermal Runaway in Lithium-Ion Batteries: Incidents, Kinetics of the Runaway and Assessment of Factors Affecting Its Initiation

A study of thermal runaway phenomena in Lithium-Ion Batteries (LIB) was conducted following different approaches. Risks related to thermal runaway are presented based on a series of incidents involving overheating, fires and explosions with these batteries in different devices; significant cases that have occurred in airplane battery cells are shown. An overview of the possible promoters for the thermal event is presented by studying compounds and reactions involved. Kinetic parameter calculations were performed using Differential Scanning Calorimetry (DSC) data available from the literature. Preliminary molecular simulations were made in order to understand mechanisms and related paths proposed. Finally, the system was studied from the perspective of process safety and the theory of runaway reactions.

Investigation on internal short circuits of lithium polymer batteries with a ceramic-coated separator during nail penetration

Internal short circuit of a lithium polymer battery (4.6 Ah capacity and 4.30 V charging voltage) with a ceramic-coated separator has been investigated by infrared measurement during nail penetration. The surface temperatures at nail penetration area and battery body were simultaneously measured by infrared camera and, as a result, three different failure modes have been proposed. The battery with 100% of SOC experiences thermal runaway phenomenon by means of the second internal short circuit. The batteries with low SOC (0% and 50% of SOC) were also investigated to identify the phenomena occurred in SOC 100% battery (the second internal short circuit), but neither fire nor explosion in the battery with low SOC was observed. The analysis of burr status after nail penetration demonstrates that it is quite important factor related to the failure modes. The results of this study can be applied to the design of safe battery.

Absorptive glass mat separator surface modification and its influence on the heat generation in valve-regulated lead-acid battery

This paper presents the results from a comparative study between two types of valve-regulated lead-acid battery cells, with uncoated and polymer composite coated absorptive glass mat (AGM) separators. The volt-ampere characteristics of the studied cells, recorded at different ambient temperatures, show that the cells with polymer coated separators have significantly lower overcharge (recombinant) current than the cells with conventional untreated AGM separator. During overcharge, the higher recombinant current in the cells with plain separator leads to higher cell temperature than that of the cells with polymer coated AGM separator.The possibility to avoid thermal runaway (TR) is also illustrated during polarization of the cells at 2.65 V. After 320 h, a conventional cell has C/4 current (trend to TR), while the cells with composite coating sustain low (C/26) constant current for long period of time (at least 650 h). The cycle life test indicates stable operation of the cells with coated separator, while the conventional cell reaches high recombinant current and thus, it is susceptible to thermal runaway phenomena.

Temperature Control Using Hybrid Control with MRAC and ECS into a MIMO Microwave Heating Process

Microwave heating is an advanced heating technique in which heat is generated inside the material, but thermal runaway phenomenon is still the major challenge of the microwave heating process. The application of a hybrid temperature control structure with model reference adaptive control (MRAC) and expert control system (ECS) to a multi-input multi-output (MIMO) microwave heating process is addressed in this paper. Two input variables, microwave power and ambient temperature, are considered to be regulated and controlled as the output variables to track the desired temperature profiles. Simulation tests are carried out in MIMO configuration to validate that the hybrid controller with MRAC and ECS achieves better control performance than the sole MRAC strategy.

Limiting stable states of high-Tc superconductors in the alternating current modes

The limiting current-carrying capacity of high-T c superconductor and superconducting tape has been studied in the alternating current states. The features that are responsible for their stable formation have been investigated under the conduction-cooled conditions when the operating peak values of the electric field and the current may essentially exceed the corresponding critical values of superconductor. Besides, it has been proved that these peak values are higher than the values of the electric field and the current, which lead to the thermal runaway phenomenon when the current instability onset occurs in the operating modes with direct current. As a result, the stable extremely high heat generation exists in these operating states, which can be called as overloaded states. The limiting stable peak values of charged currents and stability conditions have been determined taking into account the flux creep states of superconductors. The analysis performed has revealed that there exist characteristic times defining the corresponding time windows in the stable development of overloaded states of the alternating current. In order to explain their existence, the basic thermo-electrodynamics mechanisms have been formulated, which have allowed to explain the high stable values of the temperature and the induced electric field before the onset of alternating current instability. In general, it has been shown that the high-T c superconductors may stably operate in the overloaded alternating current states even under the not intensive cooling conditions at a very high level of heat generation, which is not considered in the existing theory of losses.

Research on epoxy resin decomposition under microwave heating by using ReaxFF molecular dynamics simulations

To investigate the effects of microwave heating on decomposing epoxy resin, ReaxFF molecular dynamics simulations are performed. As one of its special effects, the thermal runaway phenomenon is studied and compared under microwave heating and under conventional heating. This study shows that this phenomenon results from the enhancement of system absorption of microwave energy, which is caused by the increasing number of small size polar species generated during the pyrolysis of epoxy resin under microwave heating. Meanwhile, non-thermal effects are investigated under microwave heating. Simulations indicate that, at the early stage of decomposition, average generating rates of H2O and H2 obtained under microwave heating are always, or partly, lower than that obtained under conventional heating. To analyze the influence of microwave heating on reaction rates, collision theory is introduced. Further, several simplified collision models are constructed and formulated to study the effectiveness of collision orientations under microwave heating. Analyses illustrate that external microwave heating reduces the effectiveness of collision orientations between polar hydric fragments as well as hydroxyl radicals and polar hydric fragments, thus, decreasing relevant reaction rates.

On Thermal Stability Analysis for a Reacting Slab

In this chapter, thermal stability analysis of the steady state exothermic chemical reaction in a slab of combustible material is investigated in the present of convective heat loss to the ambient. The nonlinear differential equations governing the system are obtained and solved using perturbation technique together with a special type of Hermite-Padé series summation and improvement method. The effects of various embedded parameters on the temperature profile and thermal stability of the system are presented graphically and discussed quantitatively. The possibility of thermal runaway phenomena was shown and the corresponding thermal criticality values were obtained and illustrated on a bifurcation diagram. The results reveal the thermal stability criticality as well as the effects of various embedded parameters on the system.

12-W $X$-Band MMIC HPA and Driver Amplifiers in InGaP-GaAs HBT Technology for Space SAR T/R Modules

The chip-set for the transmitting power lineup of satellite SAR antenna T/R modules has been designed and implemented exploiting a 2- μm GaInP-GaAs heterojunction bipolar transistor (HBT) technology suitable for space applications. The HBT technology features an integrated emitter ballast resistor that enables high-power density operation without suffering thermal runaway phenomena. Two monolithic microwave integrated circuit (MMIC) driver amplifiers and a MMIC HPA are described: the drivers exhibit small-signal gains exceeding 21 dB and P1 dB output power of about 28 and 29 dBm, respectively, in a 2-GHz bandwidth and CW condition. The HPA delivers more than 40-dBm power at about 2.5-dB gain compression and power-added efficiency (PAE) exceeding 36% in a 700-MHz bandwidth in pulsed operation. Its peak performance at the center of the band are 40.9-dBm output power and 45% PAE. These performance are obtained within tight de-rating conditions for space applications.

Thermal Stability of Silicon Carbide Power Diodes

Silicon carbide (SiC) power devices can operate at much higher junction temperature than those made of silicon. However, this does not mean that SiC devices can operate without a good cooling system. To demonstrate this, the model of a merged p-i-n Schottky (MPS) SiC diode is presented, and its parameters are identified with experimental measurements. This model is then used to study the ruggedness of the diode regarding the thermal runaway phenomenon. Finally, it is shown that, where a purely unipolar diode would be unstable, the MPS structure brings increased stability.

3D Electro-thermal modelling of bonding and metallization ageing effects for reliability improvement of power MOSFETs

This paper presents a methodology, based on 3D electro-thermal simulation, to investigate failures of vertical power MOSFET due to metallization ageing of source terminal. Modelling steps to obtain a 3D finite element modelling of MOSFET are presented with the smart approximations and limitations of MOSFET electrical behaviour. The effects of bonding wire gauge and contact area with top metallization are studied to optimize the power device design. The power device thermal runaway phenomenon and hot spot formation has been simulated and discussed.

Poiseuille Flow of Reactive Phan–Thien–Tanner Liquids in 1D Channel Flow

We investigate, using direct numerical simulations, the effects of viscoelasticity on pressure driven flows of thermally decomposable liquids in channels. A numerical algorithm based on the finite difference method is implemented in time and space with the Phan–Thien–Tanner as the model for the viscoelastic liquids. The strong dependence of fluid temperature on the Frank–Kamenetskii parameter is shown for various fluid types and the phenomenon of thermal runaway is demonstrated. It is shown that viscoelastic fluids have in general delayed susceptibility to thermal runaway as compared with corresponding inelastic fluids. This paper demonstrates the efficiency of using semi-implicit finite difference schemes in solving transient problems of coupled nonlinear systems. It also provides an understanding of nonisothermal flows of viscoelastic fluids.

Thermal explosion simulation and incompatible reaction of dicumyl peroxide by calorimetric technique

Dicumyl peroxide (DCPO) is usually employed as an initiator for polymerization, a source of free radicals, a hardener, and a linking agent. In Asia, due to its unstable reactive nature, DCPO has caused many thermal explosions and runaway reaction incidents in the manufacturing process. This study was conducted to elucidate its essentially thermal hazard characteristics. In order to analyze the runaway behavior of DCPO in a batch reactor, thermokinetic parameters, such as heat of decomposition (ΔH d) and exothermic onset temperature (T 0), were measured via differential scanning calorimetry (DSC). Thermal runaway phenomena were then thoroughly investigated by DSC. The thermokinetics of DCPO mixed with acids or bases were determined by DSC, and the experimental data were compared with kinetics-based curve fitting of thermal safety software (TSS). Solid thermal explosion (STE) and liquid thermal explosion (LTE) simulations of TSS were applied to determine the fundamental thermal explosion behavior in large tanks or drums. Results from curve fitting indicated that all of the acids or bases could induce exothermic reactions at even an earlier stage of the experiments. In order to diminish the extent of hazard, hazard information must be provided to the manufacturing process. Thermal hazard of DCPO mixed with nitric acid (HNO3) was more dangerous than with other acids including sulfuric acid (H2SO4), phosphoric acid (H3PO4), and hydrochloric acid (HCl). By DSC, T 0, heat of decomposition (ΔH d), and activation energy (E a) of DCPO mixed with HNO3 were calculated to be 70 °C, 911 J g−1, and 33 kJ mol−1, respectively.

Spontaneous dissipation of elastic energy by self-localizing thermal runaway

Thermal runaway instability induced by material softening due to shear heating represents a potential mechanism for mechanical failure of viscoelastic solids. In this work we present a model based on a continuum formulation of a viscoelastic material with Arrhenius dependence of viscosity on temperature and investigate the behavior of the thermal runaway phenomenon by analytical and numerical methods. Approximate analytical descriptions of the problem reveal that onset of thermal runaway instability is controlled by only two dimensionless combinations of physical parameters. Numerical simulations of the model independently verify these analytical results and allow a quantitative examination of the complete time evolutions of the shear stress and the spatial distributions of temperature and displacement during runaway instability. Thus we find that thermal runaway processes may well develop under nonadiabatic conditions. Moreover, nonadiabaticity of the unstable runaway mode leads to continuous and extreme localization of the strain and temperature profiles in space, demonstrating that the thermal runaway process can cause shear banding. Examples of time evolutions of the spatial distribution of the shear displacement between the interior of the shear band and the essentially nondeforming material outside are presented. Finally, a simple relation between evolution of shear stress, displacement, shear-band width, and temperature rise during runaway instability is given.

A preliminary study on numerical simulation of microwave heating process for chemical reaction and discussion of hotspot and thermal runaway phenomenon

The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially, the variation of temperature in terms of space and time, as well as the hotspot and thermal runaway phenomena are discussed. Suppose the heated object is a cylinder and the incident electromagnetic (EM) wave is plane wave, the problem turns out to be a coupling calculation of 2D multi-physical fields. The integral equation of EM field is solved using the method of moment (MoM) and the thermal conduction equation is solved using a semi-analysis method. Moreover, a method to determine the equivalent complex permittivity of reactant under the heating is presented in order to perform the calculation. The numerical results for water and a dummy chemical reaction (A) show that the hotspot is a ubiquitous phenomenon in microwave heating process. When the radius of the heated object is small, the highest temperature occurs somewhere inside the object due to the concentration of the EM wave. While the radius increases to a certain degree, the highest temperature occurs somewhere close to the surface due to the skin effect, and the whole high temperature area shows crescent-shaped. That is in accordance with basic physical principles. If the radius is kept the same in the heating process, the hotspot position of water does not change, while that of reaction A with several radius values varies. For either water or A, the thermal runaway phenomenon in which small difference of radius results in large difference of highest temperature, occurs easily when the radius is small. On the contrary, it is not evident when the radius is large. Moreover, it is notable that the highest temperature in water shows oscillating decreasing trend with the increase of radius, but in reaction A almost decreases monotonously. Further study should be performed to determine if this difference is only an occasional occurrence.

Evaluation of runaway reaction for dicumyl peroxide in a batch reactor by DSC and VSP2

Dicumyl peroxide (DCPO) is usually employed as an initiator for polymerization, a source of free radicals, a hardener, and a linking agent. In Asia, due to its unstably reactive nature, DCPO has caused many thermal explosions and runaway reaction incidents in the manufacturing process. This study was conducted to elucidate its essentially hazardous characteristics. To analyze the runaway behavior of DCPO in a batch reactor, thermokinetic parameters, such as heat of decomposition (ΔH d ), exothermic onset temperature ( T 0), maximum temperature rise ((d T d t −1) max), maximum pressure rise ((d P d t −1) max), and self-heating rate, were measured via differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Meanwhile, adiabatic thermal runaway phenomena were then thoroughly investigated by VSP2. The thermokinetics of DCPO mixed with acids or bases was determined by DSC/VSP2, and the experimental data were compared with kinetics-based curve fitting of thermal safety software (TSS). Results from curve fitting indicated that all of the above-mentioned acids or bases could induce exothermic reactions at even an earlier stage of the experiments. To diminish the degree of hazard, hazard information must be provided to the manufacturing process.

A step by step methodology to analyze the IGBT failure mechanisms under short circuit and turn-off inductive conditions using 2D physically based device simulation

A systematic methodology is developed in order to clarify the punch through trench insulated gate bipolar transistor (T-IGBT) failure mechanisms which can occur under extreme operating conditions such as short circuit and clamped inductive switching. By considering a 2D dimensional physically based device simulation, and by analyzing some T-IGBT physical parameters, it is possible to identify if the failure mechanism is due to a breakdown, a latchup or a thermal runaway phenomenon.

Trench IGBT failure mechanisms evolution with temperature and gate resistance under various short-circuit conditions

Two extreme configurations under short-circuit conditions leading to the punch through trench IGBT failure under the effect of the temperature and the gate resistance have been studied. By analyzing internal physical parameters, it was highlighted that the elevation of the temperature causes an acceleration of the failure which is due to a thermal runaway phenomenon, whereas the influence of the gate resistance on the failure evolution is minimal.

A new equation for the description of dielectric losses under microwave irradiation

A new equation was developed to describe quantitatively the dielectric loss of materials that is a key parameter in the fields of microwave chemistry and microwave processing of materials under microwave irradiation. This equation can be applied to explain the complicated thermal runaway phenomenon that has relations with dielectric relaxation and to simulate the dielectric loss under microwave irradiation. It was also found that the simulation results based on this equation are in good agreement with the Volge–Fulcher law. The new equation has potential application in the study of microwave interaction with solid materials, especially in materials' processing which involves microwave chemistry, synthesis, sintering, melting, joining, surface-modifications, quality improvements, etc and it is hoped that the dynamic process of material under microwave irradiation could be explained.

Monte Carlo model for analysis of thermal runaway electrons in streamer tips in transient luminous events and streamer zones of lightning leaders

Streamers are thin filamentary plasmas that can initiate spark discharges in relatively short (several centimeters) gaps at near ground pressures and are also known to act as the building blocks of streamer zones of lightning leaders. These streamers at ground pressure, after 1/N scaling with atmospheric air density N, appear to be fully analogous to those documented using telescopic imagers in transient luminous events (TLEs) termed sprites, which occur in the altitude range 40–90 km in the Earth's atmosphere above thunderstorms. It is also believed that the filamentary plasma structures observed in some other types of TLEs, which emanate from the tops of thunderclouds and are termed blue jets and gigantic jets, are directly linked to the processes in streamer zones of lightning leaders. Acceleration, expansion, and branching of streamers are commonly observed for a wide range of applied electric fields. Recent analysis of photoionization effects on the propagation of streamers indicates that very high electric field magnitudes ∼10 Ek, where Ek is the conventional breakdown threshold field defined by the equality of the ionization and dissociative attachment coefficients in air, are generated around the tips of streamers at the stage immediately preceding their branching. This paper describes the formulation of a Monte Carlo model, which is capable of describing electron dynamics in air, including the thermal runaway phenomena, under the influence of an external electric field of an arbitrary strength. Monte Carlo modeling results indicate that the ∼10 Ek fields are able to accelerate a fraction of low‐energy (several eV) streamer tip electrons to energies of ∼2–8 keV. With total potential differences on the order of tens of MV available in streamer zones of lightning leaders, it is proposed that during a highly transient negative corona flash stage of the development of negative stepped leader, electrons with energies 2–8 keV ejected from streamer tips near the leader head can be further accelerated to energies of hundreds of keV and possibly to several tens of MeV, depending on the particular magnitude of the leader head potential. It is proposed that these energetic electrons may be responsible (through the “bremsstrahlung” process) for the generation of hard X rays observed from ground and satellites preceding lightning discharges or with no association with lightning discharges in cases when the leader process does not culminate in a return stroke. For a lightning leader carrying a current of 100 A, an initial flux of ∼2–8 keV thermal runaway electrons integrated over the cross‐sectional area of the leader is estimated to be ∼1018 s−1, with the number of electrons accelerated to relativistic energies depending on the particular field magnitude and configuration in the leader streamer zone during the negative corona flash stage of the leader development. These thermal runaway electrons could provide an alternate source of relativistic seed electrons which were previously thought to require galactic cosmic rays. The duration of the negative corona flash and associated energetic radiation is estimated to be in the range from ∼1 μs to ∼1 ms depending mostly on the pressure‐dependent size of the leader streamer zone.

Complexity in battery systems: Thermal runaway in VRLA batteries

During battery discharge, the heat generated is the sum of the Joule (resistive) and enthalpic (chemical) heating effects. Conversely, during battery charging, the heat generated is the Joule minus the enthalpic heating. If the conditions are carefully selected, one can observe a net battery cooling during charging. However, an interesting phenomenon takes place during overcharge. Those cells designed as sealed recombinant systems develop significant heating. Flooded designs do not exhibit this effect. The applied electric power generates energetic reaction products as a consequence of the electrochemical reactions. This is an energy absorbing process. The gasses are then vented into the environment. Since the sealed cells undergo a closed recombination cycle, i.e., no material is exchanged with the environment, the rate of heat generated is proportional to the power input to the cell. Essentially, the cell is behaving in the manner of a resistor. In this connection, the thermal runaway phenomenon that has been often observed in starved electrolyte cell designs raises a potential problem in battery applications. It is not efficient to design around the worst case scenario, i.e., anticipating the thermal runaway effect. It is wiser to detect its onset and shut down the charging process. An alternative approach is to develop an understanding of the thermal runaway process and, perhaps, develop a method for eliminating or effectively controlling it. A study was performed in an attempt to model the thermal runaway effect. In short, the effect appears to be related to the electrolyte distribution in the separator. This suggests that modification of the AGM separator properties could provide a means for better controlling the thermal runaway failure mode.