Direct resistive heating (DRH) packed beds provide a promising route towards efficient electrified packed-bed heating, yet predictive modeling remains hindered by unresolved contact-scale transport. This work develops a mechanics–electro–thermal particle-resolved CFD (PRCFD) model resolving electric and thermal fields to predict contact-scale heat generation and contact-to-bulk heat transfer. Electrical contact resistance (ECR) and thermal contact resistance (TCR) are first evaluated from Hertzian contact mechanics under mechanical equilibrium. For ECR, two commonly adopted limiting assumptions fail to capture the intermediate interfacial-film activation and produce 1- and 3-order-of-magnitude errors in the electrical equivalent resistance, respectively, whereas the newly introduced effective conduction area fraction, ϕc, represents this intermediate state and reduces the mean absolute deviation to 8.2% against the experimental data. For TCR, gas resistance is evaluated with a rarefied-gas correction. After model selection, the predicted ECR and TCR are implemented in the PRCFD model through bridge effective conductivities, making both heat generation and heat transfer mechanically dependent. Because the physical contact region is replaced by an artificial contact bridge, a parametric study is conducted to determine the acceptable bridge radius ratio, β. Based on heat generation, heat transfer, and hotspot formation, the acceptable range is identified as β=0.18–0.27, with β=0.18 selected for further analysis. The resolved fields reveal contact-region hotspot formation as a mechanics–electro–thermal effect. Heat is generated locally at distributed contact regions and then diffuses into the particle bulk, while the packed bed still maintains predictable bulk heating behavior in particle and gas domains.

With the widespread deployment of lithium iron phosphate (LFP) cells in energy-storage systems, the timely identification of thermal runaway precursors has become essential for battery safety management. In this work, overheating-induced thermal runaway tests are conducted on 52 Ah and 314 Ah prismatic LFP cells. Multidimensional signals, including safety-valve strain, expansion force, surface temperature, voltage and impedance, are synchronously monitored to clarify their temporal responses under different states of charge (SOCs) and cell capacities. The results show that safety-valve strain is more sensitive than lateral strain to internal gas accumulation and pressure build-up. For 52 Ah cells, strain and expansion force exhibit clear slow-growth, accelerated-growth and release stages before and during venting, whereas temperature, voltage, and impedance respond mainly after venting or close to thermal runaway. Increasing SOC advances the venting process and intensifies post-runaway heat release, with the 100% SOC cell showing the highest temperature-rise rate. Capacity comparison further reveals that the 314 Ah cell enters mechanical abnormality and venting earlier than the 52 Ah cell and exhibits a higher peak temperature, indicating a stronger thermal hazard for larger-format cells. Based on these findings, a staged warning strategy is proposed: Safety-valve strain rate and expansion-force growth rate are used as early-warning indicators, while temperature-rise rate, voltage collapse and impedance increase are used as mid-stage warning indicators. The proposed strategy provides a mechanistic and engineering-feasible basis for early thermal runaway warning of LFP energy-storage cells.

To achieve a plastic upcycling pyrolysis process with high conversion efficiency and low energy input, the pyrolysis conditions of polypropylene(PP)/HZSM-5 were optimised. Through reactive force field molecular dynamics (ReaxFF-MD) simulation techniques, it was discovered that the optimal pyrolysis temperature and catalyst loading of PP are 2000 K (748 K in the experiments) and 30 % respectively, with a conversion efficiency over 98 %. The catalytic efficiency of PP decreased by less than 2 % after 5 cycles for HZSM-5. Moreover, the catalytic effect can be breakdown down into two steps: Firstly, the HZSM-5 enhances the conversion of C3H5 and C3H7, and then these intermediate species have a higher tendency to form C3H6 as the final products. Furthermore, the deterioration mechanism of HZSM-5 was attributed to structural deformation on the active sites after numerous reactions with PP, and subsequently, a neutral hydroxyl group replaced the active site. Overall, this work demonstrated an in-depth characterisation approach using ReaxFF-MD in visualising the molecular breakdown process, revealing the catalytic and deactivation mechanism of HZSM-5 to PP. it presents an innovative framework for future research on the development of zeolite-based catalysts to improve the recycling efficiency of waste plastic

During thermal runaway, lithium-ion batteries generate a large amount of gas, leading to a rapid increase in interior gas pressure, thereby inducing shell expansion, venting, and cascading safety hazards. In this study, the thermal runaway behaviors of large-format prismatic energy storage batteries are investigated, where the evolution of interior gas pressure is especially focused, combining with expansion force and temperature under conditions with different states of charge (0%, 50%, 100% SOC) and heating powers (1000 W, 1200 W). The results indicate that with increasing SOC, the severity of thermal runaway is significantly intensified. The maximum surface temperature increases from 157 degrees C (0% SOC) to 370 degrees C (100% SOC), while the time interval between safety valve activation and complete thermal runaway sharply decreases from 1764 s to 196 s. Meanwhile, both the peak interior gas pressure and the maximum expansion force increase markedly with SOC. In contrast, increasing the heating power advances the safety valve activation time by approximately 60 s but exerts negligible influence on the peak interior pressure and expansion force. Prior to safety valve opening, a stable and consistent linear mapping relationship is observed between the interior gas pressure and expansion force, with a slope of similar to 2.2. This indicates that the externally measured expansion force can effectively and reliably characterize the variation of interior gas pressure. Based on these experimental results, the interior gas pressure and expansion force signals are extracted to establish a two-level early warning strategy for thermal runaway. In summary, the findings of this study provide valuable insights into the thermal runaway mechanism of lithium-ion batteries and offer important references for the safety design and risk mitigation of energy storage systems.

This study investigates the hydrophobic modification of silica aerogels using trimethylchlorosilane (TMCS) and characterises their morphology, wettability, and surface properties through SEM, FTIR, and contact angle measurements. Additionally, the foam stability, fire-extinguishing efficacy, and burn-back resistance of three foam formulations were analysed to investigate the impact of silica aerogel particles on the performance of fluorine-free firefighting foams. The results demonstrated that TMCS effectively modified the surface of the aerogel particles, imparting hydrophobicity. SEM analysis revealed the irregular polyhedral structure of the hydrophobic aerogel. FTIR analysis confirmed an enhanced C-H vibration peak in the hydrophobic aerogels and a higher hydroxyl content in the hydrophilic ones. Fluorine-free foams with added aerogel particles exhibited improved drainage times and outstanding fire-extinguishing performance. The hydrophobic particles increased the drainage time by 55 s and achieved a cooling rate of 35.27 degrees C/s, with a burn-back resistance time extended to 1123 s, 1.64 times that of the control. Similarly, the addition of hydrophilic aerogels increased the burn-back resistance time by 41 %. Furthermore, to deliver an in-depth atomistic description of the interactions between aerogel particles and foam components, molecular dynamics (MD) simulations using the ReaxFF force field were conducted. ReaxFF-MD revealed the key molecular-level interactions that influence foam stability and fire extinguishing, offering insights into the synergistic effects between aerogel particles and the foam matrix under high-temperature conditions.

Polypropylene (PP) is among the most versatile polymers, widely used in packaging, containers, and films, owing to its lightweight, chemical stability, and durable properties. Given the global market size of over 120 billion USD and its continued growth, insights into thermal degradation are crucial for the recycling and waste management of PP. Nevertheless, its underlying mechanisms have not been fully explored, especially the detailed reaction pathways and gas volatiles produced at different temperatures. In this study, the pyrolysis mechanisms of PP were investigated through in-depth tracking of the molecular breakdown process using reactive molecular dynamics (ReaxFF-MD) simulations at elevated temperatures to accelerate sampling. Kinetics are benchmarked against thermogravimetric analysis (TGA) under various temperature conditions to validate the degradation rates. Using chemical tracing techniques, it was discovered that the primary driving breakage forces of PP pyrolysis were the cleavage of C-C and C-H bonds and bond-scission reactions..Propylene (C3H6) is abundant at lower temperatures, whereas ethylene (C2H4) and methane (CH4) accumulate at higher temperatures; hydrogen (H2) increases with temperature, and acetylene (C2H2) remains minor and is only detectable at the highest temperature.Moreover, the pyrolysis kinetics were elucidated based on thetemperature-dependent product formation rates. The activation energy of the ReaxFF simulations of 140.84 kJ/mol was found to be reasonably consistent with the experimental results of 128.64 kJ/mol, supporting the ability of the ReaxFF model to capture key features of PP pyrolysis. Further analysis of the reaction pathways revealed the evolution patterns of intermediate and final products at different temperatures. Additionally, this study provides fundamental insights for future optimisation of pyrolysis processes to mitigate plastic waste, enhancing recycling and energy conversion operations.

Considering that large-format LiFePO4 (LFP) cells may experience internal short-circuits caused by mechanical abuse or separator failure, this study comprehensively investigates the thermal runaway behavior of large-format LFP cells under internal short-circuit conditions induced by penetration and partial separator failure. Thermal runaway triggered by penetration evolves much more rapidly than that caused by overheating or overcharging, with the internal temperature exceeding 800 degrees C within only a few tens of seconds. Penetration parameters including nail diameter, penetration rate, penetration depth, and penetration location, exert significant influence on the resulting thermal runaway characteristics. In particular, heat generation inside the cell intensifies markedly as the nail diameter and penetration depth increase. Penetration through the safety valve, however, results in only minor cell damage and fails to trigger thermal runaway due to the absence of a severe internal short-circuit. In addition, reducing the cell capacity substantially mitigates the severity of thermal runaway, whereas replacing the LFP cathode with LiNi0.5Mn0.3Co0.2O2 greatly decreases the cell's sensitivity to penetration, accompanied by violent gas generation, ejection, and combustion. Compared with penetration-induced short-circuits, thermal runaway develops more slowly when triggered by partial internal short-circuits caused by localized single-layer separator failure. Under such conditions, full internal short-circuiting and subsequent thermal runaway evolve progressively as the internal temperature rises. Distinct from the behaviors observed under overheating and overcharging, no reliable quantitative relationship is found between the internal and external parameters of the cell during internal short-circuit scenarios, as the parameter evolution depends strongly on the specific short-circuit conditions.

Amid the escalating urban heat island effects and increasing fire hazards driven by climate change and rapid urbanization, buildings face two parallel challenges: excessive heat accumulation and heightened fire vulnerability. Multifunctional surface materials that integrate passive radiative cooling (PRC) and flame retardant (FR) have emerged as promising solutions for enhancing both energy efficiency and fire safety. By synergistically combining PRC and FR functionalities, these materials can reflect solar radiation and emit heat to reduce surface temperatures, while simultaneously inhibiting ignition, slowing flame spread, and suppressing toxic smoke via gas-phase and condensed-phase mechanisms. This review presents a comprehensive overview of their working principles, performance evaluation methods, and material classifications of such materials, focusing on four main systems: organic polymer-based materials, polymer–inorganic composites, bio-based materials, and other material systems. Particular emphasis is placed on the relationship among materials, structure, and properties, strategies for integrating multifunctionality, and the influence of environmental conditions on long-term performance. Key challenges related to climate adaptability, outdoor durability, and filler dispersion are discussed to guide future research. These materials offer a promising pathway toward energy-efficient, fire-safe, and climate-resilient buildings.

High humidity typically degrades triboelectric nanogenerator (TENG) performance by dissipating surface charge. We present a printable strategy that leverages ambient moisture to enhance output by integrating polar hydrophilic networks via liquid crystal display (LCD) 3D printing. Photocopolymerization of acrylic acid (AA), 2-hydroxyethyl acrylate (HEA), and N-hydroxyethyl acrylamide (HEAA) with PEGDA yields micrometre-thin films rich in & horbar;COOH, & horbar;OH, and & horbar;CONH & horbar; groups. These groups immobilize water molecules through hydrogen bonding, forming a stable interfacial-polarization tribolayer that resists charge loss. Optimizing the HEAA:PEGDA formulation and incorporating 5 wt.% sulfobetaine methacrylate (SBMA) creates a trimer network with enhanced dipole density, achieving outputs of 45.6 & micro;A, 802 V, and a peak power density of 48.4 W m- 2 at 90% relative humidity. Density functional theory (DFT) and molecular dynamics (MD) simulations reveal water-enhanced dipole moments and robust bound-water interactions that strengthen polarization. The photocurable resin enables printing of complex micro-architectures and flexible wearables, demonstrated in a Morse-code finger-sleeve TENG and an insole sensor distinguishing gait patterns. A proof-of-concept TENG-powered backscatter communication system showcases wireless energy transmission, addressing battery replacement challenges in implantable devices.

To ensure both thermal safety and performance in high-energy-density lithium-ion battery systems, this study proposes an integrated modelling and optimization framework for a novel Thermal Management and Barrier Integration Structure (TMBIS), which couples phase change materials (PCM) with flame-retardant (FR) insulation layers. A hybrid modelling strategy is established by combining a computational fluid dynamic (CFD) based electrochemical–thermal model with a reduced-order thermal resistance network (TRN) model, capturing both internal heat generation and inter-module heat transfer mechanisms. To evaluate and optimize the thermal runaway (TR) mitigation and thermal management (BTMS) performance of the structure, Latin hypercube sampling (LHS) is first employed to generate representative design points. An artificial neural network (ANN) surrogate model is then trained to predict key performance indicators, including the maximum battery temperature and TR delay times. Finally, a multi-objective optimization is conducted using the NSGA-II algorithm to balance competing objectives, and representative trade-off solutions are identified via KMeans clustering. The proposed framework efficiently identifies optimal PCM–FR design configurations, achieving a favourable compromise between TR suppression and thermal management performance.

Zeolites offer tunable acidity and porous frameworks, making them an ideal candidate for the plastic upcycling process. However, the efficiency of currently used zeolites has yet to satisfy needs in terms of industrial-scale applications. In-depth understanding is required to realise the catalytic effect of zeolite structures, particularly the active site distribution and Si/Al ratios of zeolites result in uncertainties towards their conversion efficiency and gas product of plastic recycling, leaving the quantitative relationship between zeolites' structural parameters and catalytic efficiency insufficiently understood. Herein, reactive molecular dynamics (ReaxFF-MD) simulations integrated with experimental validation are employed to elucidate how zeolite topology, aluminium distribution, and Si/Al ratio govern polypropylene (PP) upcycling behaviour. Comparative analyses of HZSM-5, HZSM-11, HZSM-23, and HZSM-35 reveal that HZSM-23 achieves the highest gas yield of 44% and complete conversion efficiency, corresponding to a 57.7% enhancement over non-catalytic PP pyrolysis. The strong acidity and derived activation energy (184.8 kJ/mol) confirmed its superior catalytic activity. Density functional theory (DFT) calculation identifies the T7 position with the lowest Fermi level (-3.488 eV), facilitating hydrogen transfer that converts & sdot;C3H5 intermediates into propylene (C3H6). The optimal Si/Al = 30 ratio further balances acidity and desorption, maximising olefin selectivity. Orthogonal optimisation established HZSM-23@T7 (Si/Al = 30) as the most efficient configuration with good reusability and stability. This combined computational-experimental approach provides molecular-scale insights for rational zeolite design, offering a predictive pathway for industrial-scale production towards energy-efficient and sustainable plastic recycling.

Accurate and physically consistent prediction of temperature evolution in lithium-ion battery modules is essential for mitigating thermal runaway risks under realistic operating conditions. In this study, a physics-informed graph neural network–Transformer framework, termed TRPformer, is proposed for simultaneous spatiotemporal prediction of the full temperature field and fault-induced thermal anomaly identification in battery modules. The battery pack is represented as a weighted graph derived from the physical thermal resistance network and busbar heat-transfer pathways, enabling explicit modelling of inter-cell thermal coupling. A graph neural network captures spatial heat propagation, while a Transformer encoder learns long-range temporal dependencies. To enhance robustness and physical consistency, node-wise energy conservation is enforced through a physics-informed constraint during training. In thermal runaway propagation scenarios, TRPformer provides early warning more than 20 s prior to rapid temperature escalation, while under normal charge–discharge thermal management cycles, it can identify fault-induced thermal abnormal and locate faulty cells approximately 50 s in advance. By enabling one-shot prediction of the entire module temperature field, TRPformer offers a novel and scalable solution for real-time thermal monitoring, fault diagnosis, and early warning in safety-critical battery systems.

Considering that results obtained under adiabatic conditions are generally more universal and reliable, the thermal runaway issues of four typical commercial large-format energy storage cells (206, 280, 314, and 530 Ah) are systematically evaluated using an extended-volume accelerating rate calorimetry method. The solid electrolyte interphase layer decomposition at approximately 100 degrees C initiates self-heating of the cells, and all cells eventually undergo thermal runaway after being heated for 3000-4000 min under the heat-wait-search protocol. Both the onset temperature of self-heating and the thermal runaway temperature decrease with increasing cell capacity, indicating deteriorated thermal stability in larger-capacity cells. This trend is consistent with the variation in the activation energy profiles during the thermal runaway process. Furthermore, the extremely violent thermal runaway behavior of the 530 Ah cell significantly limits the effective heat release, resulting in a noticeably lower peak temperature compared with the other cells. The thermal runaway tolerance and hazard of these cells are further evaluated, showing that the tolerance decreases steadily with increasing capacity. In contrast, the 314 Ah cell exhibits the highest thermal runaway hazard due to its greater heat release, which is equivalent to the explosion of approximately 414 g of TNT and may lead to a destructive radius of about 9.81 m. Additionally, the amount of gas generated during thermal runaway increases exponentially with cell capacity, with hydrogen and hydrocarbons accounting for a large proportion of the products, indicating a considerable combustible and explosive risk. Moreover, the explosion limits of the thermal runaway gases range from approximately 4% to 40%, and this range slightly narrows as the cell capacity increases.

Forced flow immersion cooling technology is considered to have great potential for application in battery thermal management systems due to its excellent heat transfer performance. However, the external liquid tank greatly reduces the energy density and the compactness of the system. Herein, a forced flow immersion cooling system without an external tank is designed to solve the complexity problem of an immersion battery thermal management system. AF-710 L coolant as the medium is selected for the experiment and six flow modes without an external liquid tank are designed to investigate its heat dissipation performance under a high discharge rate and compare it with natural air cooling and static flow immersion cooling. The results show that this forced flow immersion cooling system can control the battery temperature within 50 degrees C under 3C discharge. Of note, the maximum temperature in M3 mode is only 42.1 degrees C, and the temperature difference is controlled within 2.5 degrees C. In addition, the AF-710 L coolant shows good thermal barrier capability in nail-puncture tests, which can significantly reduce the temperature during thermal runaway and prevent re-ignition. The system does not require an external liquid tank, which reduces the system complexity and space requirements, improves the energy density of the battery module. Our finds can provide inspirations for development of highly-efficient thermal management systems for electric vehicles.

Thermal runaway propagation (TRP) in lithium-ion battery systems remains a critical safety challenge, yet its fundamental mechanism is not fully understood. In this work, a heat flux-oriented framework is developed to investigate TRP and thermal management. A lumped thermal resistance network (TRN) model is used for system-level analysis of structural topology, triggering location, and state-of-charge (SOC) distribution, while threedimensional CFD simulations are employed to resolve spatial heat transfer associated with inter-cell materials. Three representative materials, phase change material (PCM), thermal switching material (TSM), and flameretardant material (FR), are considered. The key novelty of this work is to unify different TRP protection strategies from the perspective of heat flux control. Thermal runaway behaviour is governed by the spatiotemporal evolution of heat flux, where structural topology defines transfer pathways, SOC distribution sets thermal driving forces, and inter-cell materials regulate heat dissipation. Quantitatively, configurations with multi-path topology (e.g., 5s5p) significantly reduce heat flux imbalance and delay thermal runaway propagation. SOC heterogeneity effectively delays propagation by reducing local heat generation and redistributing thermal load. Inter-cell materials play a critical role in regulating heat flux magnitude and temporal evolution. PCM reduces peak heat flux through phase-change buffering, while TSM enables temperature-triggered thermal blocking. An optimal design combining multi-path topology, gradient SOC, and PCM/TSM achieves the most effective suppression of heat accumulation, peak temperature rise, and TRP.

Traditional fluorinated foams (AFFF/FFFP), widely used for liquid fire suppression, suffer from poor thermal stability, re-ignition propensity, and often contain environmentally harmful fluorocarbon surfactants. This study developed an interpenetrating double-network gel foam (IDNGF) using non-fluorinated surfactants (AEG and AOS), gelling agent (CMC-Na and Na₂SiO₃), and crosslinking agent (AlCit). Orthogonal experiments optimized the foam expansion ratio and water retention. The optimal formulation-0.6 wt% AOS/AEG (1:9), 2.2 wt% Na₂SiO₃, 0.14 wt% CMCNa, and 1.0 wt% AlCit-produced homogeneous foams with enhanced thermal stability due to the formation of a CMC-Al3+/silicate double-network structure. Thermogravimetric analysis revealed a significantly higher complete evaporation temperature than conventional FFFP. Reactive forcefield molecular dynamics (ReaxFF-MD) simulations identified orthosilicic acid and aluminum-containing oxides as key pyrolysis products. Fire extinguishing and re-ignition existence experiments demonstrated that IDNGF reduced extinguishing time by 3.6% relative to FFFP while significantly extending the burnback time to 603 s-a 76.3% improvement. These results highlight the potentil of using IDNGF as a high-performance, re-ignition-resistant, and sustainable fire suppression agent.

The catalytic conversion of polyolefin waste into valuable hydrocarbons strongly depends on the atomistic structure of zeolite, yet the fundamental interactions between polypropylene (PP) degradation intermediates and zeolite active sites remain insufficiently understood. In this work, the active-site chemistry of HZSM-5 during PP pyrolysis is systematically investigated by integrating experimental catalytic pyrolysis, reactive molecular dynamics (ReaxFF-MD) simulations, and density functional theory (DFT) calculations. The influence of the framework, including Si/Al ratio, isolated Al T-site location, paired Al configurations, and metal-modified active sites, is examined to elucidate how nanoscale catalytic environments regulate radical reactions during PP decomposition. ReaxFF-MD results reveal that the catalytic behaviour of HZSM-5 is highly sensitive to the spatial configuration of framework aluminium. A Si/Al ratio of 60 achieves the highest gas yield (41.8 %) and exhibits pronounced selectivity towards propylene (C3H6), while the Si/Al ratio of 30 favours the production of gasoline-range hydrocarbons (38.5 %). Additionally, the T8 site provides the most favourable environment for converting large hydrocarbon intermediates into gas yield (46.4 %) with the lower Fermi level (-3.331 eV) and adsorption energy (7.426 eV), suggesting a lower energy barrier for polymer degradation. DFT analysis further shows that cooperative paired Al sites (T5-T11) enhance the adsorption and stabilisation of reaction intermediates with the lowest Ef of -6.574 eV and adsorption energy of 3.045 eV, thereby facilitating radical cracking pathways. In addition, Fe-modified HZSM-5 significantly improves propylene formation (54.9 %) by promoting intermediate activation and hydrogen transfer reactions. Overall, fundamental insights via ReaxFF-MD simulation results have been provided in this work, revealing molecular-level interactions of zeolite-catalysed polyolefin degradation, which offer important insights towards nanoengineering of HZSM-5 catalysts for high-efficient plastic upcycling.