Self-reactive rating of thermal runaway hazards on 18650 lithium-ion batteries

Vent sizing package 2 (VSP2) was used to measure the thermal hazard and runaway characteristics of 18650 lithium-ion batteries, which were manufactured by Sanyo Electric Co., Ltd. Runaway reaction behaviors of these batteries were obtained: 50% state of charge (SOC), and 100% SOC. The tests evaluated the thermal hazard characteristics, such as initial exothermic temperature (T ₀), self-heating rate (dT?dt ^?1), pressure-rise rate (dP?dt ^?1), pressure temperature profiles, maximum temperature, and pressure which were observed by adiabatic calorimetric methodology via VSP2 using customized test cells. The safety assessment of lithium-ion cells proved to be an important subject. The maximum self-heating rate (dT?dt ^?1)_max and the largest pressure-rise rate (dP?dt ^?1)_max of Sanyo 18650 lithium-ion battery of 100% SOC were measured to be 37,468.8???C?min^?1 and 10,845.6?psi?min^?1, respectively, and the maximum temperature was 733.1???C. Therefore, a runaway reaction is extremely serious when a lithium-ion battery is exothermic at 100% SOC. This result also demonstrated that the thermal VSP2 is an alternative method of thermal hazard assessment for battery safety research. Finally, self-reactive ratings on thermal hazards of 18650 lithium-ion batteries were studied and elucidated to a deeper extent.     

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.     

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.     

Reactivity in the solid-state between ZnWO<Subscript>4</Subscript> and some rare-earth metal molybdates RE<Subscript>2</Subscript>MoO<Subscript>6</Subscript> (<Emphasis Type="Italic">RE</Emphasis>=Y,Sm, Eu,Gd, Dy,Ho, Er and Lu)

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 parameters study of 1,1-bis(tert-butylperoxy)cyclohexane at low heating rates with differential scanning calorimetry

Having two active peroxide groups, 1,1-bis(tert-butylperoxy)cyclohexane (BTBPC) has a certain degree of thermal instability. It is usually used as an initiator in a chemical process, and therefore, careless operation could result in severe accidents. This study emphasized the runaway reactions of BTBPC 70 mass% (4.5–5.2 mg), the relevant thermokinetic parameters, and the thermal safety parameters. Differential scanning calorimetry was used to evaluate the above-mentioned thermokinetic parameters, using four low heating rates (0.5, 1, 2, and 4 °C min^?1) combined with kinetic simulation method. The results indicated that apparent exothermic onset temperature (T _o), apparent activation energy (E _a), and heat of decomposition (ΔH _d) were ca. 118 °C, 156 kJ mol^?1, and 1,080 kJ kg^?1, respectively. In view of process loss prevention, at the low heating rates of 0.5, 1, 2, and 4 °C min^?1, storing BTBPC 70 mass% below 27.27 °C is a more reassuring approach.     

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 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.     

Slow molecular mobility in the amorphous thermoplastic polysulfone

The thermally stimulated depolarization current (TSDC) technique has been used to study the slow molecular mobility of polysulfone in the glassy state and in the glass transformation region, i.e., in the temperature ranging from ?155 to 183 °C. Since the polysulfone is a rigid polymer without polar side-groups, a broad and low-intensity secondary relaxation was detected in the temperature region from ?120 °C up to the glass transition; the activation energy of the motional modes of this secondary relaxation is in the range between 35 and 100 kJ mol^?1. The glass transition temperature of polysulfone provided by the TSDC technique is T _M = T _g = 176 °C (at 4 °C min^?1). The relaxation time at this temperature is τ(T _g) = 33 s and the fragility index was found to be m = 91. Our results are compared with literature values obtained by dynamic mechanical analysis and by dielectric relaxation spectroscopy. The amorphous polysulfone was also characterized by DSC; a glass transition signal with an onset at T _on = 185.5 ± 0.3 °C (heating rate 10 °C min^?1) was detected, with ΔC _p = 0.21 ± 0.01 J g^?1 °C^?1.     

Research of thermal decomposition kinetic characteristic of emulsion explosive base containing Fe and Mn elements

The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM) which was used to prepare nano-MnFe₂O₄ particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of 2.5, 5 and 7.5°C min⁻¹respectively under the atmosphere of dynamic air from room temperature to 400°C. The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the temperature up to 60°C. The maximum speed of decomposition (dα/dT)_m at the heating rate of 5 and 7.5°C min⁻¹ was more than 10 times of that at 2.5°C min⁻¹ and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction.     

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 properties and kinetics of new-generation posterior bulk fill composite cured light-emitting diodes

In this study, the thermal behavior in terms of glass transition (T _g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E _a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min^?1) during DSC. The results show that the Xtrabase composite displayed the highest T _g (120 °C at a 5 °C min^?1 heating rate) and E _a (157.64 kJ mol^?1) values associated with thermal degradation from the main chain of the polymer.     

Supercapacitors based on carbide-derived carbons synthesised using HCl and Cl2 as reactants

Micro- and mesoporous carbide-derived carbons (CDCs) were synthesised from TiC powder via a gas-phase reaction using HCl and Cl₂ within the temperature range of 700–1,100 °C. Analysis of X-ray diffraction results show that TiC-CDCs consist mainly of graphitic crystallites. The first-order Raman spectra showed the graphite-like absorption peaks at ~1,577 cm^?1 and the disorder-induced peaks at ~1,338 cm^?1. The low-temperature N₂ sorption experiments were performed, and specific surface areas up to 1,214 and 1,544 m²?g^?1 were obtained for TiC-CDC (HCl) synthesised at T?=?800 °C and TiC-CDC (Cl₂) synthesised at T?=?900 °C, respectively. For the TiC-CDC powders synthesised, a bimodal pore size distribution has been established with the first maximum in the region up to 1.5 nm and the second maximum from 2 to 4 nm. The energy-related properties of supercapacitors based on 1 M (C₂H₅)₃CH₃NBF₄ in acetonitrile and TiC-CDC (Cl₂) and TiC-CDC (HCl) as electrode materials were also investigated by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge and constant power methods. The specific energy, calculated at U?=?3.0 V, are maximal for TiC-CDC (Cl₂ 800 °C) and TiC-CDC (HCl 900 °C), which are 43.1 and 31.1 W?h?kg^?1, respectively. The specific power, calculated at cell potential U?=?3.0 V, are maximal for TiC-CDC (Cl₂ 1,000 °C) and TiC-CDC (HCl 1,000 °C), which are 805.2 and 847.5 kW?kg^?1, respectively. The Ragone plots for CDCs prepared by using Cl₂ or HCl are quite similar, and at high power loads, the TiC-CDC material synthesised using Cl₂ at 900 °C, i.e. the material with optimal pore structure, delivers the highest power at constant energy.     

Ultimate tensile properties of elastomers. VII. Effect of crosslink density on time–temperature dependence

Data on tensile strength and elongation at break for a series of Viton A-HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from ?5 to 230°C (25 ? T — T_g ? 260°C) on seven vulcanizates having crosslink densities v_e (estimated from C₁ in the Mooney-Rivlin equation) from 0.46 × 10^?5 to 24.4 × 10^?5 mole/cm³. At an extension rate of 1 min^?1, an increase in v_e affects the tensile strength σ_b (based on the undeformed cross-sectional area) and the true tensile strength σ_bσ_b (based on the cross-sectional area of a deformed specimen) as follows: σ_b is essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λ_bσ_b decreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate-property data gave log a_T; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σ_b/T, log 273λ_bσ_b/T, and (λ_b — 1)/(λ_b — 1)_max against logt_b/(t_b)_max, where t_b is the temperature-reduced time to break and (t_b)_max is the value at which the ultimate extension ratio λ_b attains its maximum, (λ_b)_max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λ_bσ_b/T and (λ_b — 1)/(λ_b — 1)_max are substantially independent of (or only weakly dependent on) crosslink density, that 273λ_b/T increases with v_e, and that 273λ_b/T ∝? v_e^0.6 and λ_b ∝? v_e^?0.4 at a large value of t_b/(t_b)_max.     

Optimization of operating parameters and rate of uranium bioleaching from a low-grade ore

In this study the bioleaching of a low-grade uranium ore containing 480 ppm uranium has been reported. The studies involved extraction of uranium using Acidithiobacillus ferrooxidans derived from the uranium mine samples. The maximum specific growth rate (µ ^max) and doubling time (t _d) were obtained 0.08 h^?1 and 8.66 h, respectively. Parameters such as Fe²⁺ concentration, particle size, temperature and pH were optimized. The effect of pulp density (PD) was also studied. Maximum uranium bio-dissolution of 100 ± 5 % was achieved under the conditions of pH 2.0, 5 % PD and 35 °C in 48 h with the particles of d ₈₀ = 100 μm. The optimum concentration of supplementary Fe²⁺ was dependent to the PD. This value was 0 and 10 g of FeSO₄·7H₂O/l at the PD of 5 and 15 %, respectively. The effects of time, pH and PD on the bioleaching process were studied using central composite design. New rate equation was improved for the uranium leaching rate. The rate of leaching is controlled with the concentrations of ferric and ferrous ions in solution. This study shows that uranium bioleaching may be an important process for the Saghand U mine at Yazd (Iran).     

DSC study on the thermal properties of soybean protein isolates/corn starch mixture

The use of soybean protein isolates (SPI) and corn starch (CS) for the manufacturing of textured protein by thermo-mechanical means requires a characterization of their thermal properties. SPI and CS mixtures were examined at starch mass fractions from 0 (pure SPI) to 100 (pure CS). The blends were determined by means of differential scanning calorimetry, with water content of 30, 50, and 70 % and heating rate of 5 and 10 °C min^?1 over 20 to 130 °C. The results obtained showed that protein in the blend increased the onset (T _o) and peak (T _p) temperatures of the starch gelatinization, while starch in the blend decreased the ΔH and ΔT_1/2 of the protein. T _o , T _p, and ΔT_1/2 of SPI and CS decreased significantly with the increase of water content. T _p and ΔT_1/2 of SPI and CS had a marked increase with an increase of heating rate from 5 to 10 °C min^?1. These results suggested that there was no chemical reaction between SPI and CS when they were heated from 20 to 130 °C. SPI in the blend restricted the CS gelatinization, while the presence of CS protected the SPI from denaturation. The increasing water content did promote thermal transition of the mixture. Higher heating rate leads to higher transition temperature.     

Solvation effect in thermal decomposition of 2,2′-azoisobutyronitrile on the N,N-dimethylformamide/methyl methacrylate system

The thermal decomposition rate constant of AIBN (??_d) in N,N-dimethylformamide (DMF)/methyl methacrylate (MM) mixtures of various compositions at 60°C is studied. The ??_d value is 6.45 × 10^?4min^?1 for pure DMF and 7.20 × 10^?1 min^?1 for pure methyl methacrylate. The ??_d values of DMF/MM mixtures were found to be dependent on the mixture composition. This dependence is not a linear function of the monomer mole fraction, but has a minimum at ca. 20 30 mol% of MM. The relationship between the AIBN decomposition rate constant and the monomer mole fraction was interpreted on the basis of solvation of the initiator molecules. © 1995 John Wiley & Sons, Inc.     

Thermal decomposition of poly(α,α,α′,α′-tetrafluoro-p-xylylene) in nitrogen and oxygen

The thermal decomposition of poly(α,α,α′,α′-tetrafluoro-p-xylylene) (parylene AF-4) films with thicknesses of ca. 7.5 and 10 μm has been studied by both dynamic (10°C min^?1) and isothermal TG in either nitrogen or oxygen atmospheres. In dynamic studies with nitrogen, gross decomposition occurs between 546.7±1.4 and 589.0±2.6°C, with 26.8±4.4% of the initial mass remaining at 700°C. With oxygen as the purge gas, the onset of decomposition shifts slightly to 530.8±4.2°C. The end of the transition at 587.4±2.6°C is within experimental error of the nitrogen value, but no polymer remains above 600°C. Isothermal data were obtained at 10°C intervals from 420 to 490°C in nitrogen, and from 390 to 450°C in oxygen. Plots of log(Δ%wt/Δt)vs. T^?1 are linear throughout the specified range for oxygen and from 420 to 470°C for nitrogen. The calculated activation energies of (147±16) kJ mol^?1 and (150±12) kJ mol^?1 in N₂ and O₂, respectively, are equal within experimental error.     

The thermal decomposition of (NH4)4V2O11 in a nitrogen atmosphere and the kinetics of the first decomposition step

Although the reaction products are unstable at the reaction temperatures, at a heating rate of 2 deg·min^?1 ammonium peroxo vanadate, (NH₄)₄V₂O₁₁, decomposes to (NH₄)[VO (O₂)₂ (NH₃)] (above 93°C); this in turn decomposes to (NH₄) [VO₃ (NH₃)] (above 106°C) and then to ammonium metavanadate (above 145°C). On further heating vanadium pentoxide is formed above 320°C. The first decomposition reaction occurs in a single step and the Avrami-Erofeev equation withn=2 fits the decomposition data best. An activation energy of 148.8 kJ·mol^?1 and a ln(A) value of 42.2 are calculated for this reaction by the isothermal analysis method. An average value of 144 kJ·mol^?1 is calculated for the first decomposition reaction using the dynamic heating data and the transformation-degree dependence of temperature at different heating rates.     

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.