Thermal Degradation Mechanism Research Articles

Depolymerization of PMMA-Based Dental Resin Scraps on Different Production Scales

This research explores the depolymerization of waste polymethyl methacrylate (PMMAW) from dental material in fixed bed semi-batch reactors, focusing on three production scales: laboratory, technical and pilot. The study investigates the thermal degradation mechanism and kinetics of PMMAW through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, revealing a two-step degradation process. The heat flow during PMMAW decomposition is measured by DSC, providing essential parameters for designing pyrolysis processes. The results demonstrate the potential of DSC for energetic analysis and process design, with attention to standardization challenges. Material balance analysis across the production scales reveals a temperature gradient across the fixed bed negatively impacting liquid yield and methyl methacrylate (MMA) concentration. Reactor load and power load variables are introduced, demonstrating decreased temperature with increased process scale. The study identifies the influence of temperature on MMA concentration in the liquid fraction, emphasizing the importance of controlling temperature for efficient depolymerization. Furthermore, the research highlights the formation of aromatic hydrocarbons from the remaining char, indicating a shift in liquid composition during the depolymerization process. The study concludes that lower temperatures below 450 °C favor liquid fractions rich in MMA, suggesting the benefits of lower temperatures and slower heating rates in semi-batch depolymerization. The findings contribute to a novel approach for analyzing pyrolysis processes, emphasizing reactor design and economic considerations for recycling viability. Future research aims to refine and standardize the analysis and design protocols for pyrolysis and similar processes.

Startified thermal degradation in blue InGaN quantum well structures: P-GaN growth temperature and its influence on quantum well optical properties

Thermal degradation in blue InGaN multi-quantum well (MQW) structures induced by varying high p-GaN growth temperature and the subsequent influence on the optical properties of MQW are investigated. The results indicate that higher p-GaN growth temperatures improve p-GaN layer contact quality, but may lead to an optical property degradation of InGaN MQWs. A stratified thermal degradation mechanism is observed. The degradation primarily affects the upper quantum barrier layers and results in indium desorption and re-evaporation, where elevated p-GaN growth temperatures may induce more indium segregation and decomposition than in lower layers of MQW. In extreme conditions, such as 1060℃, indium atoms in lower layers escape, causing partial lattice structure corruption and severe degradation in MQW structure, which is also more distinctive in the upper layers.

Accelerated degradation of photovoltaic modules under a future warmer climate

AbstractSolar photovoltaic (PV) module deployment has surged globally as a part of the transition towards a decarbonized electricity sector. However, future climate change presents issues for module degradation due to prolonged exposure to outdoor conditions. Here, we identify key degradation mechanisms of monocrystalline‐silicon (mono‐Si) modules and empirically model their degradation modes under various climate scenarios. Modules tend to degrade faster due to the thermal degradation mechanism. We estimate that the weighted average degradation rate will increase up to 0.1%/year by 2059. On assessing the impacts of module degradation on future PV power generation and levelized cost of energy, we project up to 8.5% increase in power loss that leads to ~10% rise in future energy price. These results highlight the need to climate‐proof PV module design through careful material selection and improvements in the module manufacturing process. In particular, we recommend the use of heat dissipation techniques in modules to prevent degradation due to overheating.

Thermal decomposition kinetics and mechanism of poly(ethylene 2,5-furan dicarboxylate) Nanocomposites for food packaging applications

Poly(ethylene 2,5-furan dicarboxylate) (PEF) based nanocomposites containing different nanoparticles like Ag, TiO2, ZnO, ZrO2 Ce-Bioglass, have been synthesized via in-situ polymerization techniques targeting food packaging applications. Zeta potential measurements showed an increase in the negative zeta potential value due to an increase in the surface charge density of the nanocomposites. Thermogravimetric analysis results proved that, except PEF-ZnO nanocomposite, all the other nanocomposites exhibited good resistance to thermal degradation without serious mass loss until 330 °C. Thermal decomposition kinetic analysis and the dependence of activation energy on the degree of conversion (α), indicated that the presence of ZnO nanoparticles influences, the degradation mechanism of PEF. In contrast, the presence of Ce-Bioglass nanoparticles leads to a slower degradation process, contributing to the enhanced resistance to thermal degradation of the PEF-Bioglass nanocomposite. The thermal degradation mechanism of PEF nanocomposites analyzed by pyrolysis‒gas chromatography/mass spectrometry (Py-GC/MS) indicated that the primary thermal degradation mechanism for the studied nanocomposites was β-hydrogen bond scission, while to a lesser extent, α-hydrogen bond scission products were noted in PEF-TiO2 and PEF-ZrO2 nanocomposites.

Recent advances and challenges in thermal stability of PVA‐based film: A review

AbstractFood packaging film is being developed using biodegradable polymers to prolong the shelf life of foods and address the environmental damage caused by non‐biodegradable plastics. Poly(vinyl alcohol) (PVA) is a biodegradable polymer with outstanding characteristics and can be easily shaped into a film. However, PVA‐based film still faces several obstacles that seriously restrict its practical application in the food packaging industry, particularly its low thermal stability limits the film process method. The growing preference demand for PVA‐based films with enhanced thermal stability in food packaging can be attributed to their advantageous characteristics, including commendable temperature resistance, safety, versatile processing capabilities, and prolonged shelf life. It is critical to comprehend the difficulties with PVA thermal degradation behavior and mechanism, and how to address this problem. In this review, we provide strategies for improving the thermal stability of PVA film including modification with environmentally friendly polymers, nanoparticles, and crosslinking agents. Also, the current challenges, and the potential for future advancements in the thermal stability of PVA and its composites are proposed. The new insight into the relationship between PVA based film processing and thermal properties of materials are expected to provide a valuable guide for developing PVA films with high thermal stability.

Biomass characterization and solvent extraction as tools to promote phenol production from urban pruning

Nowadays, leaves, bark, and branches are generated from the tree-pruning process in urban places, where their management is a problem because of the necessity of disposal. These wastes are lignocellulosic biomasses with poor properties for use in biofuel production, but with interesting projections for building block products such as phenol compounds. Therefore, extensive biomass characterization of urban pruning from Liquidambar styraciflua L. was developed to evaluate its composition as a tool for phenol production through thermal processing, in which solvent extraction is a complementary tool for selectivity improvement. The results showed high lignin content in bark and leaves at 45 and 28 %, respectively, compared with that in branches (14 %). Additionally, high extractives in leaves (14 %) could be an additional source of phenols. The lignin units were analyzed by Raman dispersion, revealing p–hydroxyphenyl (H) units in the bark, guaiacyl (G) units in the bark and leaves, and syringyl (S) units only in the branches. Furthermore, the micropyrolysis coupled with gas chromatography/mass spectrometry assay realized at 600 °C showed high presence of phenolic compounds in the three biomass investigated, where a high phenol concentration was identified in leaves, probably due to the S unit degradation during pyrolysis. With these results, an assay for bio-oil production was performed in a low-temperature pyrolysis reactor using leaves as feedstock, reaching a low bio-oil yield with high water content favored for the high inorganic content of leaves (13 %). The produced bio-oil was used for liquid–liquid extraction evaluation, where 1-octanol and methyl isobutyl ketone were identified as interesting solvents for catechol and phenol extraction, respectively. This article presents the challenge of characterizing each part of urban trees, which could be a tool to promote the use of urban pruning by studying the thermal degradation mechanism to implement processes for high-value products, such as phenols produced from L. styraciflua L.

Preparation of carbon nanotube-filled bismuth/tin green nanocomposites and their efficient catalytic activity in the thermal decomposition of ammonium perchlorate

The practical utility of bismuth and tin compounds, as promising green combustion catalysts, is constrained by their substantial particle agglomeration. Herein, a straightforward ultrasonication-assisted method was reported to incorporate bismuth and tin compounds into the inner spaces of carbon nanotubes (CNTs), affording CNTs-confined bismuth (tin) compounds. The as-prepared nanocomposites were structurally completely characterized. The electrochemical property investigations showed that the introduction of bismuth and tin compounds increases the catalytic active sites of carbon nanotubes and inhibits nanoparticle agglomeration effectively. The theoretical calculations revealed that synergistic effects between Bi2O3 and carbon nanotubes can improve the efficiency of electron transfer in the Bi(NO3)3@A-CNTs(M1) composite. The evaluation results of the combustion catalytic performance of the nanocomposites on ammonium perchlorate (AP) pyrolysis suggested that adding 5 wt.% Bi(NO3)3@A-CNTs(M1) and DBT@A-CNTs(M1) (DBT = Dibutyltin dichloride) in AP brought about a more concentrated thermal decomposition process, advancing the peak of AP in the high-temperature decomposition stage from 420.4 ℃ to 328.9 and 325.9 ℃, respectively, and boosting its heat release from 976.42 J·g−1 to 2251.2 J·g−1 and 2452.03 J·g−1, respectively. The studies on the thermal degradation mechanism of AP, probed by thermal decomposition kinetics, in-situ solid FTIR and TG-FTIR-MS, concluded that the electron transfer from the critical steps ClO4− to NH4+ and O2 to O2− is accelerated by the interaction of the in-situ formed Bi2O3 nanoparticles and carbon nanotubes, boosting the relative contents of more stable gases, and ultimately promoting AP pyrolysis. A tentative catalytic thermal degradation mechanism of AP is finally proposed.

Thermal stability and degradation mechanism of C60 fullerene‐based polymers

AbstractIn this paper, the thermal stability and degradation mechanisms of C60 fullerene‐based polymers, obtained by click polymerization between dialkyne‐substituted C60 derivative monomers and 1,3,5‐tris(dodecyloxy)benzene‐based diazide comonomers, were evaluated. The activation energy of the fullerene polymer C60P2 with an ethylene spacer, determined under peak degradation rate conditions, was lower than that of the counter polymer C60P1 with a methylene spacer, suggesting lower thermal stability of C60P2. The combined technique of thermogravimetric analysis—mass spectroscopy and Fourier transform infrared spectroscopy revealed that the thermal decomposition onset of the analyzed samples is accompanied by CC cleavage of the dodecyloxyside chain groups, followed by the decomposition of the 1,2,3‐triazole, dicarboxylate and benzoate moieties. It was found that no thermal decomposition of the fullerene carbon cage occurs up to 670°C. Molecular modeling with Hyperchem software version 7.5 confirmed that C60P1 is more thermally stable than C60P2.

A Review on the Adiabatic Shear Banding Mechanism in Metals and Alloys Considering Microstructural Characteristics, Morphology and Fracture

The current review work studies the adiabatic shear banding (ASB) mechanism in metals and alloys, focusing on its microstructural characteristics, dominant evolution mechanisms and final fracture. An ASB reflects a thermomechanical deformation instability developed under high strain and strain rates, finally leading to dynamic fracture. An ASB initially occurs under severe shear localization, followed by a significant rise in temperature due to high strain rate adiabatic conditions. That temperature increase activates thermal softening and mechanical degradation mechanisms, reacting to strain instability and facilitating micro-voiding, which, through its coalescence, results in cracking failure. This work aims to summarize and review the critical characteristics of an ASB’s microstructure and morphology, evolution mechanisms, the propensity of materials against an ASB and fracture mechanisms in order to highlight their stage-by-stage evolution and attribute them a more consecutive behavior rather than an uncontrollable one. In that way, this study focuses on underlining some ASB aspects that remain fuzzy, allowing for further research, such as research on the interaction between thermal and damage softening regarding their contribution to ASB evolution, the conversion of strain energy to internal heat, which proved to be material-dependent instead of constant, and the strain rate sensitivity effect, which also concerns whether the temperature rise reflects a precursor or a result of ASB. Except for conventional metals and alloys like steels (low carbon, stainless, maraging, armox, ultra-high-strength steels, etc.), titanium alloys, aluminum alloys, magnesium alloys, nickel superalloys, uranium alloys, zirconium alloys and pure copper, the ASB propensity of nanocrystalline and ultrafine-grained materials, metallic-laminated composites, bulk metallic glasses and high-entropy alloys is also evaluated. Finally, the need to develop a micro-/macroscopic coupling during the thermomechanical approach to the ASB phenomenon is pointed out, highlighting the interaction between microstructural softening mechanisms and macroscopic mechanical behavior during ASB evolution and fracture.

A numerical model to prevent the thermal degradation of CFRPs at extreme heating rates – The laser processing of CF/PEEK

This study proposes a coupled thermal-chemical numerical model for preventing the thermal degradation of carbon fibre (CF) reinforced polymers at extreme heating rates. Its applicability is demonstrated in a laser-heating case study of CF-reinforced poly-ether-ether-ketone (CF/PEEK). The kinetic parameters of the PEEK matrix, derived from thermogravimetric analysis at conventional heating rates, are introduced in the model and an extrapolation approach is applied to investigate the laser heating of CF/PEEK. The results show that the model captures the heating rate effect on the decomposition of the material, and is used to identify the processing conditions that can reach high temperatures without triggering the thermal degradation mechanisms of the PEEK matrix. Then, a multi-technique experimental investigation takes place to identify the processing conditions that first trigger the thermal degradation mechanisms of CF/PEEK in the examined laser-heating case study. Interestingly, a good agreement is found between the experimental and numerical investigations which validates the model and the applied extrapolation approach.

Kinetic modeling of thermal degradation of TDI/MDI-based flexible polyurethane foam under nitrogen and air atmospheres with Shuffled Complex Evolution algorithm: Insights from TG-FTIR analysis

This study investigates the thermal degradation mechanisms and kinetics of TDI/MDI-based flexible polyurethane foam (FPUF) under nitrogen and air atmospheres, employing thermogravimetric (TG) analysis in conjunction with TG-FTIR technique. The information gleaned from these analysis is used to construct kinetic model based on model-free approaches coupled with the Shuffled Complex Evolution optimization algorithm. The results uncovered the five-step complex thermal degradation process of TDI/MDI-based FPUF compared to TDI-based or MDI-based polyurethane in both atmospheres. In nitrogen atmosphere, this involve the dissociation of TDI- and MDI-based urethane bonds, breakage of recombined urea bonds, random chain scission of polyol, and further degradation of incompletely pyrolyzed solid products. In air atmosphere, the process emcompasses dissociation of TDI- and MDI-based urethane linkages, accelerated oxidation of polyol chains, consumption of urea groups, and combustion of partially oxidized intermediates. This work also emphasizes the limitations of solely relying on TG tests for kinetic modeling, necessitating the integration of TG tests and TG-FTIR technique to obtain a comprehensive understanding of degradation mechanisms. The significance of the acquired insights lies in their potential to reshape the design of thermo-chemical reactors, resulting in heightened resource recovery, diminished environmental impact, and a stride towards a circular economy within the polyurethane industry.

Gel Biopolymer Electrolytes Based on Saline Water and Seaweed to Support the Large-Scale Production of Sustainable Supercapacitors.

Climate change and the demand for clean energy have challenged scientists worldwide to produce/store more energy to reduce carbon emissions. This work proposes a conductive gel biopolymer electrolyte to support the sustainable development of high-power aqueous supercapacitors. The gel uses saline water and seaweed as sustainable resources. Herein, a biopolymer agar-agar, extracted from red algae, is modified to increase gel viscosity up to 17-fold. This occurs due to alkaline treatment and an increase in the concentration of the agar-agar biopolymer, resulting in a strengthened gel with cohesive superfibres. The thermal degradation and agar modification mechanisms are explored. The electrolyte is applied to manufacture sustainable and flexible supercapacitors with satisfactory energy density (0.764 Wh kg-1 ) and power density (230 W kg-1 ). As an electrolyte, the aqueous gel promotes a long device cycle life (3500 cycles) for 1 A g-1 , showing good transport properties and low cost of acquisition and enabling the supercapacitor to be manufactured outside a glove box. These features decrease the cost of production and favor scale-up. To this end, this work provides eco-friendly electrolytes for the next generation of flexible energy storage devices.

Study on the thermal decay mechanism of basalt fiber reinforced resin based friction materials

PurposeResin-based friction materials are the most widely used key materials in industry for braking and transmission. However, the friction coefficient of resin-based friction materials significantly decreases at temperatures above 300°C, which reduces their friction performance.Design/methodology/approachThis study combines elevated-temperature mechanical experiments with friction and wear experiments to explain the thermal degradation resistance performance and temperature recovery performance of resin-based friction materials. It also investigates the influence of friction material strength and worn morphology on the friction coefficient of materials at elevated temperature.FindingsThe experimental results show that the increase in friction coefficient of friction materials below 300°C is mainly due to the increase in worn morphology characterization parameters, and the thermal degradation phenomenon above 300°C is mainly due to the decrease of shear strength of friction film. Basalt fiber can significantly improve the thermal degradation resistance of friction materials. The friction coefficient of basalt fiber-reinforced specimens after thermal degradation reaches 0.421–0.443, which is 19–25% higher than the original. The thermal decay rate is 9.03–11.0%, which is 7.9–9.87% lower than the original. Moreover, the friction coefficient has good cooling recovery performance.Originality/valueRevealed the thermal degradation mechanism of resin-based friction materials, verified that basalt fibers can improve the thermal degradation resistance of friction materials and provided reference for the development of new friction materials.

Machine learning approach for ion imprinted (IIP) and non-imprinted (NIP) polymer discrimination based on pyrolysis kinetic data

The improper disposal of effluents containing toxic elements, such as nickel and mercury, can result in the gradual deterioration of surface water quality, impacting aquatic ecosystems and human health. Ionically imprinted polymers (IIPs) are promising candidates for remediating toxic areas due to their high removal rates and selectivity. In this study, multifunctional IIPs were developed using Ni2+ and Hg2+ as template ions and dithizone, methacrylic acid, and ethylene glycol dimethacrylate as complexing agent, monomer, and cross-linking agent, respectively, to remove Ni (II) and Hg (II) from effluents. The thermal decomposition behavior and degradation mechanism of ion imprinted polymers were investigated to address the issue of limited lifespan. The kinetic study revealed that the samples showed significant thermal stability, and the IIP-Duo sample exhibited higher activation energy compared to the non-imprinted polymer (NIP) and the mono-imprinted polymer (IIP), indicating that double impression alters the structure of the polymer and consequently its thermal degradation. Three machine learning models were applied to classify the samples according to imprinting, successfully predicting 95% or more of the classes correctly without overfitting or overmodelling. The master plot method showed that imprinting did not affect the thermal decomposition pathway, with the IIP, IIP-Duo, and NIP samples presenting the same mechanism geometrical contraction model (R3) at a conversion rate between 0.4 and 0.9. These findings suggest that multifunctional IIPs are promising materials for remediating areas impacted by toxic elements.

Understanding the Thermal Degradation Mechanism of High-Temperature-Resistant Phthalonitrile Foam at Macroscopic and Molecular Levels.

Polymer foam, a special form of polymer, usually demonstrates some unexpected properties that rarely prevail in the bulky polymer. Studying the thermal degradation behavior of a specific polymer foam is important for its rational design, quick identification, objective evaluation, and industrial application. The present study aimed to discover the thermal degradation mechanism of high-temperature-resistant phthalonitrile (PN) foam under an inert gas atmosphere. The macroscopic thermal decomposition of PN foam was carried out at the cost of size/weight loss, resulting in an increasing number of open cells with pyrolyzation debris. Using the TGA/DTG/FTIR/MS technique, it was found that PN foam involves a three-stage thermal degradation mechanism: (I) releasing gases such as H2O, CO2, and NH3 generated from azo-containing intermediate decomposition and these trapped in the closed cells during the foaming process; (II) backbone decomposition from C-N, C-O, and C-C cleavage in the PN aliphatic chain with the generation of H2O, CO2, NH3, CO, CH4, RNH2, HCN, and aromatic gases; and (III) carbonization into a final N-hybrid graphite. The thermal degradation of PN foam was different from that of bulky PN resin. During the entire pyrolysis of PN foam, there was a gas superposition phenomenon since the release of the decomposition volatile was retarded by the closed cells in the PN foam. This research will contribute to the general understanding of the thermal degradation behavior of PN foam at the macroscopic and molecular levels and provide a reference for the identification, determination, and design of PN material.

Flavor precursors identification and thermal degradation mechanisms of glucoerucin in fragrant rapeseed oil

The degradation products of glucosinolates endow rapeseed oil with a characteristic aroma, however, the mechanism remains unclear. In this study, 29 individual glucosinolates were identified in six rapeseeds (Brassica napus) using widely targeted metabolism, including 22 aliphatic, 5 aromatic, and 2 indole glucosinolates. Characterization of thermally induced aromas from new precursors-glucoerucin was performed in different pH matrices via headspace-solid phase microextraction and gas chromatography-mass spectrometry. Six glucoerucin degradation were identified including 5-methylthio-pentanenitrile and dimethyl trisulfide et al. The results of thermal model showed that Glucoerucin could generate volatile 5-methylthio-pentanenitrile via dehydration and formed 1-isothiocyanato-4-(methylsulfanyl)butane via (394.9 μg/kg) by the Rosen rearrangement further product pungent odors 4-isothiocyanato-1-butene (5.6 μg/kg) at pH 5. Sulfur-containing compounds included dimethyl disulfide and dimethyl trisulfide can provide pungent and cabbage notes in matrices at pH 7 and 9. The results provide a new understanding in the forming mechanism of characteristic odor in fragrant rapeseed oil.

Enhancing Structural, Optical, and Thermal Properties of PVA/PEO by Incorporating CrBr2

Films of the PVA/PEO polymer blend incorporated by CrBr2 were prepared using the casting method. Several characterization tools were used to study the PVA/PEO CrBr2 samples. Adding CrBr2 to the PVA/PEO significantly affects the structure, optical and thermal behaviour of the samples. The X-ray diffraction peaks suggest that the pure PEO/PVA blend is semi-crystalline. Still, the presence of CrBr2 reduces the intensity of these peaks, indicating interactions between the polymer blend and filler. The appearance of the main peaks of CrBr2 confirms that the complexation between the PVA/PEO and CrBr2 leads to decreased crystallinity and increased amorphous phase. The UV-Visible data indicate that adding CrBr2 reduces the energy band gap transitions due to the presence of defects and increasing disorder in the samples, creating localized energy states that can lead to energy level overlaps and a reduction of the energy gap. The DSC thermograms show that adding CrBr2 results in higher glass transition and melting temperatures, indicating improved thermal properties and enhanced thermal stability due to intermolecular interactions between CrBr2 and the PVA/PEO blend. The Coats-Redfern method was used to estimate ΔS*, ΔH*, and ΔG* in TGA measurements. These thermal parameters suggest that the presence of CrBr2 affects the thermal degradation mechanism. The values of ΔS*, ΔH*, and ΔG* decrease irregularly with increasing CrBr2, indicating that adding CrBr2 alters the thermal degradation mechanism of the PVA/PEO blend. The dielectric constant and the dielectric loss of the samples decrease with frequency No relaxation peaks observed in the dielectric curves indicate non-Debye behavior.

Molecular Evidence of Structural Changes in Silk Using Unlimited Degradation Mass Spectrometry.

Proteomics has important uses in archeological science because it can distinguish species, reveal the evolution of paleontology, and provide biological evidence of historical events. However, this technique still has full potential in the study of silk aging mechanisms. In this work, we propose a strategy combining unlimited degradation with mass-spectrometry-based proteomics techniques, which interpret protein fragmentation propensity and secondary structure changes by detecting content changes of specific peptide groups in complex proteomes. This approach was employed to study the conformational changes in silk microscopic crystals after heat treatment. Combining conventional mechanics and crystallographic characterization, a thermal aging degradation mechanism model was proposed. At the same time, it explained the interesting problem that the crystallinity remained unchanged, but the mechanical properties decreased significantly. Focusing on the unlimited degradation process, this method will be widely applicable to the study of silk and wool aging processes and regenerated silk fibroin.

Thermal conversion performance, kinetic mechanism, and products of electric vehicle lithium battery diaphragms

The proliferation of waste lithium batteries is on the rise; however, the thermal treatment attributes of these batteries are largely overlooked, and the conversion mechanism of lithium battery separators remains unclear. This study marks the first comprehensive to compare the thermal degradation characteristics, kinetic parameters and mechanisms, thermal degradation products, and degradation pathways of polypropylene (PP) and polyethylene (PE) lithium battery diaphragms. The pyrolysis temperatures for the PP and PE were 340–500 and 440–530 °C, respectively. PP and PE exhibited average activation energies of 65.19–73.04 and 207.62–209.40 kJ/mol, respectively. At 600–800 °C, the yields of PP and PE pyrolysis gases and gasoline products increased with increasing temperature, while the yields of diesel and paraffin products decreased. The most dominant products generated from the pyrolysis of PP and PE were olefins, and the amount of olefin products from PE increased with increasing pyrolysis temperature. CH3 fracture was the first reaction step that occurred during PP pyrolysis. Our study provides useful information for industrial recycling, disposal, and utilization of electric vehicle lithium battery separators as well as data on the pyrolysis behaviours and transformation mechanisms of polyolefin wastes.

Research on the impact of high-temperature aging on the thermal safety of lithium-ion batteries

Understanding the thermal safety evolution of lithium-ion batteries during high-temperature usage conditions bears significant implications for enhancing the safety management of aging batteries. This work investigates the thermal safety evolution mechanism of lithium-ion batteries during high-temperature aging. Similarities arise in the thermal safety evolution and degradation mechanisms for lithium-ion batteries undergoing cyclic aging and calendar aging. Employing multi-angle characterization analysis, the intricate mechanism governing the thermal safety evolution of lithium-ion batteries during high-temperature aging is clarified. Specifically, lithium plating serves as the pivotal factor contributing to the reduction in the self-heating initial temperature. Additionally, the crystal structure of the cathode induced by the dissolution of transition metals and the reductive gas generated during aging attacking the crystal structure of the cathode lead to a decrease in thermal runaway triggering temperature. Furthermore, the loss of active materials and active lithium during aging contributes to a decline in both the maximum temperature and the maximum temperature rise rate, ultimately indicating a decrease in the thermal hazards of aging batteries.