Thermal runaway features of 18650 lithium-ion batteries for LiFePO4 cathode material by DSC and VSP2

In view of availability, accountability, and applicability, LiFePO₄ cathode material has been confirmed to be better than LiCoO₂ cathode material. Nevertheless, few related researches were conducted for thermal runaway reaction of the LiFePO₄ batteries. In this study, vent sizing package 2 (VSP2) and differential scanning calorimetry were employed to observe the thermal hazard of 18650 lithium-ion batteries and their content??LiFePO₄ cathode material, which were manufactured by Commercial Battery, Inc. Two states of the batteries were investigated, which was charged to 3.6?V (fully charged) and 4.2?V (overcharged), respectively, and important parameters were obtained, such as self-heating rate (dT?dt ^?1), pressure-rise rate (dP?dt ^?1), and exothermic onset temperature (T ₀). The results showed that T ₀ for fully charged is about 199.94?°C and T _max is about 243.23?°C. The entire battery for LiFePO₄ cathode material is more stable than other lithium-ion batteries, and an entire battery is more dangerous than a single cathode material. For process loss prevention, the data of battery of VSP2 test were applied as reference for design of safer devices.     

Thermal hazard evaluations of 18650 lithium-ion batteries by an adiabatic calorimeter

In this study, the thermal hazard features of various lithium-ion batteries, such as LiCoO₂ and LiFePO₄, were assessed properly by calorimetric techniques. Vent sizing package 2 (VSP2), an adiabatic calorimeter, was used to measure the thermal hazards and runaway characteristics of the 18650 lithium-ion batteries under an adiabatic condition. The thermal behaviors of the lithium-ion batteries were obtained at normal and abnormal conditions in this study. The critical parameters for thermal hazardous behavior of lithium-ion batteries were obtained including the exothermic onset temperature (T ₀), heat of decomposition (ΔH), maximum temperature (T _max), maximum pressure (P _max), self-heating rate (dT/dt), and pressure rise rate (dP/dt). Therefore, the result indicates the thermal runaway situation of the lithium-ion battery with different materials and voltages in view the of TNT-equivalent method by VSP2. The hazard gets greater with higher voltage. Without the consideration of other anti-pressure measurements, different voltages involving 3.3, 3.6, 3.7, and 4.2 V are evaluated to 0.11, 0.23, 0.88, and 1.77 g of TNT. Further estimation of thermal runaway reaction and decomposition reaction of lithium-ion battery can also be confirmed by VSP2. It shows that the battery of a fully charged state is more dangerous than that of a storage state. The technique results showed that VSP2 can be used to strictly evaluate thermal runaway reaction and thermal decomposition behaviors of lithium-ion batteries. The loss prevention and thermal hazard assessment are very important for development of electric vehicles as well as other appliances in the future. Therefore, our results could be applied to define important safety indices of lithium-ion batteries for safety concerns.     

Thermal hazard evaluation of tert-butyl peroxide using non-isothermal and adiabatic calorimetric approaches

Tert-butyl peroxide (TBPO), is a typical organic peroxides (OPs),which is widely applied as initiator in poly-glycidyl methacrylate (PGMA) reaction, and is employed to provide a free-radical in frontal polymerization, and which has also caused many thermal runaway reactions and explosions worldwide. To find an unknown and insufficient hazard information for an energetic material, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2) were employed to detect the fundamental thermokinetic parameters involving the exothermic onset temperature (T ₀), heat of decomposition (??H _d), temperature rise rate (dT · dt ^?1), time to maximum rate under adiabatic situation (TMR_ad), pressure rise rate (dP · dt ^?1), and maximum pressure (P _max), etc. The T ₀ was calculated to be 130?°C using DSC and VSP2. Activation energy (E _a) of TBPO was evaluated to be 136?kJ?mol^?1 by VSP2. In view of the loss prevention, calorimetric applications and model evaluation to integrate thermal hazard development are adequate means for inherently safer design.     

Evaluation of thermal hazard for lauroyl peroxide by VSP2 and TAM III

When above certain temperature limits, lauroyl peroxide is an unstable material. If the thermal source cannot be properly governed during any stage in the preparation, manufacturing process, storage or transport, runaway reactions may inevitably be induced immediately. In this study, the influence of runaway reactions on its basic thermal characteristic was assessed by evaluating thermokinetic parameters, such as activation energy (E _a) and frequency factor (A) by thermal activity monitor III (TAM III). This was achieved under five isothermal conditions of 50, 60, 70, 80, and 90?°C. Vent sizing package 2 (VSP2) was employed to determine the maximum pressure (P _max), maximum temperature (T _max ), maximum self-heating rate ((dT?dt ^?1)_max), maximum pressure rise rate ((dP?dt ^?1)_max), and isothermal time to maximum rate ((TMR)_iso) under the worst case. Results of this study will be provided to relevant plants for adopting best practices in emergency response or accident control.     

Evaluation of adiabatic runaway reaction of methyl ethyl ketone peroxide by DSC and VSP2

Methyl ethyl ketone peroxide (MEKPO) is generally applied to manufacturing in the polymerization processes. Due to thermal instability and high exothermic behaviors of MEKPO, if any operation is undertaken recklessly or some environmental effect is produced suddenly during the processes, fires and explosions may inevitably occur. In this study, thermal analysis was evaluated for MEKPO by differential scanning calorimetry (DSC) test. Vent sizing package 2 (VSP2) was used to analyze the thermal hazard of MEKPO under various stirring rates in a batch reactor. Thermokinetic and safety parameters, including exothermic onset temperature (T ₀), maximum temperature (T _max), maximum pressure (P _max), self-heating rate (dT dt ⁻¹), pressure rise rate (dP dt ⁻¹), and so on, were discovered to identify the safe handling situation. The stirring rates of reactor were confirmed to affect runaway and thermal hazard characteristics in the batch reactor. If the stirring rate was out of control, it could soon cause a thermal hazard in the reactor.     

Explosion evaluation and safety storage analyses of cumene hydroperoxide using various calorimeters

Plenty of thermal explosions and runaway reactions of cumene hydroperoxide (CHP) were described from 1981 to 2010 in Taiwan. Therefore, a thermal explosion accident of CHP in oxidation tower in 2010 in Taiwan was investigated because of piping breakage. In general, high concentration of CHP for thermal analysis using the calorimeter is dangerous. Therefore, a simulation method and a kinetic parameter were used to simulate thermal hazard of high concentrations of CHP only by the researcher. This study was applied to evaluate thermal hazard and to analyze storage parameters of 80 and 88 mass% CHP using three calorimeters for the oxidation tower, transportation, and 50-gallon drum. Differential scanning calorimetry (DSC) (a non-isothermal calorimeter), thermal activity monitor III (TAM III) (an isothermal calorimeter), and vent sizing package 2 (VSP2) (an adiabatic calorimeter) were employed to detect the exothermic behavior and runaway reaction model of 80 and 88 mass% CHP. Exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), maximum temperature (T _max), time to maximum rate under isothermal condition (TMR_iso) (as an emergency response time), maximum pressure (P _max), maximum of self-heating rate ((dT/dt)_max), maximum of pressure rise rate ((dP/dt)_max), half-life time (t _1/2), reaction order (n), activation energy (E _a), frequency factor (A), etc., of 80 and 88 mass% CHP were applied to prevent thermal explosion and runaway reaction accident and to calculate the critical temperature (T _c). Experimental results displayed that the n of 80 and 88 mass% CHP was determined to be 0.5 and the E _a of 80 and 88 mass% CHP were evaluated to be 132 and 134 kJ mol^?1, respectively.     

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Organic peroxides (OPs) have caused many momentous explosions and runaway reactions, resulting from thermal instability, chemical pollutants, and even mechanical shock. In Taiwan, dicumyl peroxide (DCPO), due to its unstable reactive nature, has caused two thermal explosions and runaway reaction incidents in the manufacturing process. To evaluate thermal hazards of DCPO in a batch reactor, we studied thermokinetic parameters, such as heat of decomposition (†H _d), exothermic onset temperature (T ₀), maximum temperature rise ((dT/dt)_max), maximum pressure rise ((dP/dt)_max), self-heating rate (dT/dt), etc., via differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2).     

Thermal runaway and fire behavior investigation of lithium ion batteries using modified cone calorimeter

The lithium ion battery has been widely used, but it has high fire risk due to its flammable materials. In this study, a series of combustion tests are conducted on the 18650-type lithium ion batteries using the modified cone calorimeter. The temperature and voltage variation of the battery, heat release rate and gas generation during combustion are measured in this study. The battery is heated evenly by the self-made heater, and the reliable trigger temperatures of thermal runaway are obtained for different states of charge (SOCs) batteries in this study. The fire behavior of the 100% SOC batteries is shown in this paper. The net heat absorption by the battery before thermal runaway is calculated based on the heat transfer theory. It ranges from 56.81 to 64.05 kJ for 0 to 100% SOC batteries, which shows a decreasing trend as SOC increases. The peak combustion heat release rate of 100% SOC batteries is 3.747?±?0.858 kW. CH₄ and CO gases are detected before and after thermal runaway. The generation of CO shows an increasing trend as SOC increases. Some suggestions on the early warning system of battery thermal runaway are proposed based on this study.

     

Effects of cumene hydroperoxide on phenol and acetone manufacturing by DSC and VSP2

Cumene hydroperoxide (CHP) being catalyzed by acid is one of the crucial processes for producing phenol and acetone globally. However, it is thermally unstable to the runaway reaction readily. In this study, various concentrations of phenol and acetone were added into CHP for determination of thermal hazards. Differential scanning calorimetry (DSC) tests were used to obtain the parameters of exothermic behaviors under dynamic screening. The parameters included exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), and exothermic peak temperature (T _p). Vent sizing package 2 (VSP2) was employed to receive the maximum pressure (P _max), the maximum temperature (T _max), the self-heating rate (dT/dt), maximum pressure rise rate ((dP/dt)_max), and adiabatic time to maximum rate ((TMR)_ad) under the worst case. Finally, a procedure for predicting thermal hazard data was developed. The results revealed that phenol and acetone sharply caused a exothermic reaction of CHP. As a result, phenol and acetone are important indicators that may cause a thermal hazard in the manufacturing process.     

Thermal runaway analyses for two organic peroxides with H2O and dry fire-extinguishing chemicals by DSC and VSP2

In recent years, organic peroxides, including methyl ethyl ketone peroxide (MEKPO) and cumene hydroperoxide (CHP), have often caused thermal runaway reactions, fires, and thermal explosions worldwide. Under normal circumstances, H₂O and dry fire-extinguishing chemicals are often employed to eliminate fire situations. We evaluated the thermal runaway reaction for MEKPO and CHP mixed with H₂O and dry fire-extinguishing chemicals by differential scanning calorimetry, and thermal runaway reaction for CHP mixed with dry fire-extinguishing chemicals by vent sizing package 2. The results showed that ABC dry chemical, BC dry chemical, and XBC dry chemical all caused the decomposition of MEKPO to occur at lower onset temperature and H₂O caused the ΔH _d of MEKPO to become higher. On the other hand, H₂O and XBC dry chemical induced the decomposition of CHP to occur at lower onset temperature as well as lower thermal explosion temperature. The maximum of self-heating rate ((dT/dt)_max) and the maximum pressure-rise rate ((dP/dt)_max) of CHP mixed with dry fire-extinguishing chemicals were measured lower than CHP alone. The results indicated that MEKPO and CHP are highly hazardous when mixed with H₂O and some dry fire-extinguishing chemicals. In view of loss prevention, the results can be useful references for fire fighters dealing with thermal upsets in chemical plants.     

Evaluation of thermal hazard for commercial 14500 lithium-ion batteries

Commercial lithium-ion batteries ranged from different sizes, shapes, capacities, electrolytes, anode and cathode materials, etc. have recently caused many incidents under abusive or normal operating conditions worldwide. Inherently safer designs with active or passive protections have became the captious issues that need more attentions paid to. In this study, the worst scenarios on thermal runaway of four commercial batteries were conducted and compared. A customized-made closed testing instrument was utilized to measure and track thermal behaviors of four brands of cylindrical lithium-ion batteries under maximum open circuit voltage condition. Characteristics on thermal hazards of lithium-ion batteries such as onset temperature, maximum temperature, maximum self-heat rate, maximum pressures, battery mass loss, etc. were measured and evaluated. Results point out that one brand of cells reached the maximum temperature and maximum self-heat rate of 590.9 K and 1,130.4 K min^?1, respectively. In conclusion, in case of thermal runaway all the lithium-ion batteries will rupture the cell and catch fire automatically owing to the maximum temperatures over the auto-ignition temperature of electrolytes and the maximum pressure higher than four times of maximum allowable working pressure, respectively. In addition, Lithium-ion battery with cathode material of LiFePO₄ was verified to be more stable than the lithium-ion battery with cathode material of LiMn₂O₄ or LiCoO₂.     

Thermal decomposition of hydrogen peroxide in the presence of sulfuric acid

Hydrogen peroxide (H₂O₂) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H₂O₂ mixed with sulfuric acid (H₂SO₄) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H₂SO₄, the experimental data of T ₀, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H₂O₂ and H₂O₂ mixed with H₂SO₄ (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.     

Study on thermal hazards for isoprene monomer (IPM) mixed with aluminum oxide

Isoprene monomer (IPM) is a colorless, volatile liquid obtained from petroleum or coal tar that occurs naturally in many process plants. It is used chiefly to make synthetic rubber. Our study used calorimetric approaches to conduct thermal analysis and hazard assessment of aluminum oxide (Al₂O₃) and IPM relevant studies. Differential scanning calorimetry, thermal activity monitor III, thermogravimetry, and vent sizing package 2 were used to discuss thermal instability reaction of Al₂O₃, which adsorbed IPM, and find every possible reason for cases of fire to prevent any future recurrence of the package store and transport related hazards. By means of calorimetric analysis technology, we can observe thermal decomposition or mass loss for different adsorbed concentrations of IPM and Al₂O₃ to discuss the related thermal stability parameters, such as exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), self-accelerating exothermic rate (dT dt ^?1), pressure rise rate, and maximum reaction temperature (T _max). Then, we can understand the potential hazard factors that contribute to disasters related to processing, transport, and storage of security controls and reaction process design.     

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li₄Ti₅O₁₂/LiMn₂O₄ batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.     

Thermal hazard evaluation of tert-butyl hydroperoxide mixed with four acids using calorimetric approaches

Possessing thermal instability inherently, organic peroxides have caused many severe accidents in chemical industries all over the world. tert-Butyl hydroperoxide (TBHP) is usually used as initiator or oxidant because of its strong oxidizing ability in the chemical process. In this study, the thermal hazard analysis of TBHP mixed with various acids was investigated. Differential scanning calorimetry (DSC) and vent sizing package 2 were used to figure out the thermal runaway behaviors of TBHP. Thermokinetic parameters, such as exothermic onset temperature (T ₀), maximum temperature (T _max), and enthalpy (ΔH), were obtained from thermal curves. In addition, the activation energy (E _a) and rate constant (k) were calculated by the Arrhenius equation. Therefore, the T ₀ was determined to be 91.6 °C for exothermic reaction using DSC under 4 °C min^?1 of heating rate. The E _a for exothermic reaction was calculated to be 92.38 kJ mol^?1 by DSC in this study. As far as loss prevention is concerned, thermokinetic parameters are crucial to the relevant processes in the chemical industries, particularly under process upsets.     

Thermal hazard investigation of cumene hydroperoxide in the first oxidation tower

This article studies the thermokinetics and safety parameters of cumene hydroperoxide (CHP) manufactured in the first oxidation tower. Vent sizing package 2 (VSP2), an adiabatic calorimeter, was employed to determine reaction kinetics, the exothermic onset temperature (T ₀), reaction order (n), ignition runaway temperature (T _{C, I}), etc. The n value and activation energy (E _a) of 15?mass% CHP were calculated to be 0.5 and 120.2?kJ?mol^?1, respectively. The heat generation rate (Q _g) of 15?mass% CHP compared with hS (cooling rate)?=?6.7?J?min^?1?K^?1 of heat balance, the T _S,E and the critical extinction temperature (T _{C, E}) under 110?°C of ambient temperature (T _a) were calculated 111 and 207?°C, respectively. The Q _g of 15?mass% CHP compared with hS?=?0.3?J?min^?1?K^?1 of heat balance was applied to determine the T _{C, I} that was evaluated to be 116?°C. This article describes the best operating conditions when handling CHP, starting from the first oxidation tower.     

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.     

Thermal hazard evaluation for methyl ethyl ketone peroxide mixedwith inorganic acids

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO₃, H₃PO₄ and H₂SO₄) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T ₀), heat of reaction (ΔH _d), time to maximum rate (TMR), maximum self heat rate (dT/dt)_max, adiabatic temperature rise (ΔT _ad), maximum pressure of decomposition (P _max) and so on. Mixing MEKPO with hydrochloric acid resulted in the lowest T ₀ among inorganic acids. Nitric acid not only lowered the T ₀ but also delivered the highest heat releasing rate or self heat rate (dT/dt), which was concluded to be the worst case in terms of contamination hazards during storage or transportation of MEKPO.     

Fire behaviors study on 18650 batteries pack using a cone-calorimeter

To investigate the effects of different state of charges (SOCs), external heating powers and charging/discharging treatment on the fire behaviors of 18650 batteries pack, three groups of abuse experiments were conducted with the help of a cone-calorimeter. The fire hazards of batteries pack were characterized by measuring the flame photographs, battery surface temperature, ignition time, thermal runaway time, heat release rate and radiative heat flux. According to the results, it is found that the fire behaviors of batteries pack will appear in advance and behave more violent with the increase in SOC. Additionally, the higher heating power will exacerbate the fire hazards of batteries pack by increasing the surface temperature rise rate, the total heat released and the total heat flux of pack leading to an earlier thermal runaway and more rigorous consequence. Finally, the pack with discharging/charging treatment has a much lower heat released compared to the pack without any treatment due to the incomplete burning and incomplete release of energy. Besides, their fire behaviors also exhibit earlier and severer.

     

Incident investigation on thermal instability of an intermediate using adiabatic calorimeter

Thermal instability is a loss of thermal control which liberates high amount of energy and pressure. An incident took place during drying of an intermediate having amino alcohol functional group in agitated nutsche filter dryer at plant scale. During our investigation using advanced reactive system screening tool (ARSST), thermal decomposition was observed. Onset temperature of decomposition (T _o) is at 85 °C, adiabatic temperature rise due to decomposition (ΔT _ad) is 215 °C, maximum temperature attained due to decomposition (T _max) is 300 °C, maximum self-heat rate (dT/dt)_max is 6,215 °C min^?1, and maximum rate of pressure rise (dP/dt)_max is 1,442 psi min^?1 obtained from ARSST experiments. T _D24 value is 75 °C which was estimated experimentally. The correlations of these results were utilized to identify the root cause of this incident and necessary control measures were taken accordingly.