Thermal Failure Research Articles

Li-ion battery charge transfer stability studies with direct current impedance spectroscopy

The safety of lithium-ion batteries is closely related to the charge transfer process inside the battery. With the rapid increase in battery usage, battery safety issues have become increasingly prominent. Due to technical limitations, the current battery thermal failure management system cannot realize risk early warning. Charge transfer resistance (Rct) is a macroscopic parameter characterizing the battery transport process, which can be detected by electrochemical impedance spectroscopy (EIS). Due to the high cost of EIS test equipment and high signal-to-noise ratio requirements, it is still not applicable to electric vehicles. In addition, Rct is affected by ambient temperature and battery aging, which brings challenges to online safety diagnosis. Here we propose a method to obtain the activation energy of a battery using direct current impedance spectroscopy (DCIS), which enables the stability diagnosis of the charge transport process. DCIS is a time-domain impedance spectroscopy technique. It uses the time constant characteristic of the internal resistor–capacitor network to detect battery parameters. Activation energy is the energy barrier for lithium-ions to cross the electrode/electrolyte interface and can indicate the stability of the charge transport process. Since activation energy is a microscopic parameter, it is not affected by temperature and aging, which is beneficial for battery safety diagnosis. The experimental results show that the charge transfer process of the sample cells with a state of health (SOH) greater than 80% is stable. When the SOH is less than 80%, the activation energy drops rapidly from 0.55 eV to 0.16 eV, indicating an increased risk of thermal runaway. Since DCIS supports online detection, it provides an option for safety diagnosis of electric vehicle batteries.

Experimental study of thermal runaway propagation along horizontal and vertical directions for LiFePO4 electrical energy storage modules

With the growing installation of electrochemical energy storage systems, the safety issues of lithium-ion batteries have attracted extensive attention. To identify the development of thermal failure in energy storage systems, horizontal and vertical thermal runaway (TR) propagation characteristics of lithium-iron-phosphate battery modules with different connections are systematically investigated herein. Once TR occurs in the initial battery, it initially propagates to subsequent batteries along the horizontal direction, followed by vertical propagation to the upper batteries. Particularly, the almost simultaneous occurrences of TRs in the upper batteries accompanied by extreme combustion are observed during vertical propagation, exhibiting huge thermal hazards. The maximum temperature and heat release of upper batteries are 548.3 °C and 490.7 kJ, much higher than that of lower batteries with values of 423.2 °C and 217.7 kJ, demonstrating upper batteries experience severer TR. Moreover, the heat generated by the combustion of the individual battery can increase temperatures of upper batteries by 30 °C–40 °C, which is insufficient to cause vertical TR propagation, while TRs of upper batteries will eventually be triggered with the proceeding of horizontal TR propagation. The results provide valuable information for TR propagation between battery modules and benefit the safety application of energy storage systems.

Investigation on safe-operating-area degradation and failure modes of SiC MOSFETs under repetitive short-circuit conditions

• Repetitive short circuits cause thermal runaway failure of SiC MOSFETs • Safe operating area reduces after repetitive short-circuit conditions • Repetition frequency and duration affect degradation of SiC MOSFETs • Hole traps in gate oxides induce degradation of SiC MOSFETs The safe operating area is an operating area with high reliability for SiC MOSFET, and its degradation may cause power electronic system failure. The safe-operating-area degradation and the failure modes of 1200V/66A SiC MOSFET caused by repetitive short-circuit stress with different short-circuit times and short-circuit time intervals are investigated. A short circuit test platform with circuit protection is configured to degrade DUT(device under test), and the safe operating area is characterized after repetitive short circuit stress is applied. The degradation mechanism of the safe operating area is explained by the 1-D electro-thermal coupling model based on Sentaurus TCAD. When the critical short-circuit duration is 12μs, the single short-circuit failure mode of DUT with 400V dc-bus voltage is a gate-source short-circuit failure. From the short circuit test result, the failure modes under repetitive short-circuit conditions include gate-source short-circuit failure and thermal runaway, depending on the repetitive short-circuit time intervals. For the same short-circuit time interval, when the short-circuit duration is 10μs, the weakest boundary of the safe operating area is the blocking voltage. When the short-circuit duration is 2μs, all three boundaries of the safe operating area are contracted. These results are confined to 400V dc-bus voltage, 25°C case temperature, and 18V/-3V gate-source voltage. Schematic diagram of the degradation of the safe operating area of the device under long-term operating conditions. (a) Small margin, failure (b) Large margin, high cost (c) Optimal design

Thermal cycling behavior and failure mechanism of Yb2O3-doped yttria-stabilized zirconia thermal barrier coatings

Thermal cycling behavior and failure mechanism of Yb2O3-doped yttria-stabilized zirconia thermal barrier coatings

A thermo-elastic-hydrodynamic model for air foil thrust bearings considering thermal seizure and failure analyses

This study aims to investigate the thermo-elastic performance of an air-lubricated thrust bearing under the thermal failure effect. A thermo-elastic-hydrodynamic model was established using temperature-dependent alloy material properties. The thermo-elastic deformation characteristics were analyzed based on the fluid-thermal-structure interaction approach. The mechanisms of bearing thermal seizures and failure behavior were studied. The results show that the rotor thermal warping deformation at low rotating speed plays a leading role in the increase of the film thickness. The rotor-foil thermal seizure occurs in a high rotating speed. The additional forced cooling conditions effectively reduce the risk of thermal failure.

Thermal Performance Analysis and Prediction of Printed Circuit Boards

Printed circuit boards (PCBs) are important components of electronic devices, they play the roles of mechanical connections and electrical transmission, thermal failure is their main failure mode, the heat flow analysis and thermal reliability design are the basis and premise to improve thermal performance of PCBs. In this paper, analysis models of PCBs thermal performance are built based on the principles of fluid mechanics and the finite element method, and we obtain the influence and analysis of internal heat sources on PCBs thermal performance. The study provides a theoretical basis for PCBs thermal reliability design which can be applied to high-density Internet of Things and blockchain ICT integration.

Analysis on thermal stress of optimized functionally graded coatings during thermal shock based on finite element simulation

Thermal barrier coatings (TBCs) are mainly coated on the high-temperature hot components for aero engines or gas turbines. TBCs can provide sufficient protection to the metal and improve the service life of the turbine blades. In this paper, three different structures of TBCs were designed, which were single ceramic layer coatings (SCLC), double ceramic layer coatings (DCLC), and optimized functionally graded coatings (OFGC). The thermal shock resistance was analyzed to investigate the effect of structure on the thermal shock failure of the coatings. The thermal stress inside the coatings during the thermal cycling of the TBCs was analyzed based on the finite element simulation. The results indicated that using a buffer layer to reduce the maximum stress value in the coating system was an effective means of increasing the coating thermal cycle service life.

Challenges and Opportunities to Mitigate the Catastrophic Thermal Runaway of High‐Energy Batteries

AbstractLi‐ion batteries (LIBs) that promise both safety and high energy density are critical for a new‐energy future. However, recent studies on battery thermal runaway (TR) suggest that the higher the energy is compressed in a battery, the thermal accidents with fires and explosions can occur in a more catastrophic way. This “trade‐off” between energy density and safety poses challenging obstacles toward the future applications of the developing high‐energy chemistries. Herein, the thermal studies on the most appealing high‐energy (HE)‐LIB chemistries are carefully reviewed. The TR characters of the HE‐LIBs, the material thermal failure behaviors as well as the underneath reaction mechanisms, and the most advanced TR mitigation technologies are comprehensively summarized. Moreover, the effectiveness of different TR mitigation routes is analyzed. Based on the analysis, the main challenges for TR mitigation in HE chemistries are further explained. Finally, opinions on the future TR mechanism studies and the promising safety design routes to overcome this intrinsic “trade‐off” between high energy and safety are presented.

Responsive materials and mechanisms as thermal safety systems for skin-interfaced electronic devices

Soft, wireless physiological sensors that gently adhere to the skin are capable of continuous clinical-grade health monitoring in hospital and/or home settings, of particular value to critically ill infants and other vulnerable patients, but they present risks for injury upon thermal failure. This paper introduces an active materials approach that automatically minimizes such risks, to complement traditional schemes that rely on integrated sensors and electronic control circuits. The strategy exploits thin, flexible bladders that contain small volumes of liquid with boiling points a few degrees above body temperature. When the heat exceeds the safe range, vaporization rapidly forms highly effective, thermally insulating structures and delaminates the device from the skin, thereby eliminating any danger to the skin. Experimental and computational thermomechanical studies and demonstrations in a skin-interfaced mechano-acoustic sensor illustrate the effectiveness of this simple thermal safety system and suggest its applicability to nearly any class of skin-integrated device technology.

Photovoltaic Penetration with MILP Method and Technical Minimum Loading Consideration

Technological development and the reduction of installation costs have caused a rapid growth of solar power plants in Indonesia. The National Electricity Company (Perusahaan Listrik Negara, PLN) strives to achieve the energy mix of renewable energy to 23% by 2025. Solar power plants are unique in that they only supply their power during the daytime. It makes solar power plants connected to the power system change the load profile of the Java-Bali system. In this study, the penetration of solar power plants changed the scheduling of the Java-Bali system because the penetration was installed to the technical minimum loading of existing power plants. When penetration is too big, thermal generator scheduling failure is possible. Unit commitment and economic dispatch with mixed-integer linear programming (MILP) method using CPLEX and Python were carried out to calculate the fuel and generation costs per kWh before and after the penetration. MILP was used to solve the cost fuel equation, namely an integer and nonlinear mix equations, that are challenging to be solved using standar nonlinear programming methods. Due to the use of the MILP-UC, all objective function equations and restraint functions must be linear functions. The tests were conducted for three years, from 2023 to 2025. Simulation results on the Java-Bali system show that the capacity of solar power plants penetrating the Java-Bali system against the peak load will be 52%, 52%, and 50% in 2023, 2024, and 2025, respectively. Meanwhile, penetration of solar power plants to technical minimum loading of existing power plants resulted in the fuel cost falling by 23% in 2023 and 22% in 2024 and 2025. Lastly, the cost of generation per kWh will be decreased by 8% in 2023 and will be as low as 7% in 2024 and 2025.

Personalized design and field experiment of polycrystalline diamond compact bits for high-temperature geothermal wells

Considering the existing geothermal drilling conditions in Kenya (200 °C, low penetration rate, and short service life), we propose new polycrystalline diamond compact (PDC) bits. The new PDC bit oblong holes, increase the drill hole radial coverage, can enlarge hole direct injection cooling cleaning the area of cutting tooth, reduce thermal wear failure of PDC cutters. Combined with the formation characteristics of the Olkaria block in a Kenyan well, the personalized design of PDC bits was realized by considering the following three aspects: high temperature–resistant PDC cutter optimization, bit cutting structure realization, and bit hydraulic structure realization. Furthermore, a φ 215.9-mm flat and long waterstoma PDC bit was developed and a field experiment was conducted. Experimental results show that the drilling speed of the PDC bit with flat waterstoma increased by 35.8%–144.3% and the footage increased by 173.4%–361.5% compared with the same bit in adjacent wells. This indicates that the PDC bit with flat waterstoma can adapt to Kenya's high temperature conditions (200 °C), efficiently cool the cutters, and prolong the service life of bits, accelerating the exploration and development of high-temperature geothermal wells. Furthermore, reducing geothermal drilling costs has positive implications.

Towards Thermal-Aware Workload Distribution in Cloud Data Centers Based on Failure Models

Increasing workload conditions lead to a significant surge in power consumption and computing node failures in data centers. The existing workload distribution strategies focused on either thermal awareness or failure mitigation, overlooking the impact of node failures on the energy efficiency of cloud data centers. To address this issue, a new holistic model is built to characterize the impacts of workloads, computing and cooling costs, heat recirculation, and node failure on the energy efficiency of cloud data centers. Leveraging such a holistic model, we propose a novel thermal-aware workload distribution strategy called <i>HGSA</i> that takes node failure into accountand can improve the energy efficiency of cloud data centers. Our empirical findings confirm that (i) faulty nodes lead to a large rise in power consumption, and (ii) failure locations play a vital role in the power consumption of data centers. Experimental results unveil that HGSA is adroit at making near-optimal decisions in workload distribution strategies. In particular, HGSA cuts down the minimum inlet temperature by 5.2 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> -15 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> , improves the maximum air temperature of a Computer Room Air Conditioner (CRAC) model by 4.2 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> -26.5 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> , lowers the cooling cost by 15.4 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> -50 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> compared to the existing solutions. Furthermore, HGSA cuts back the total power consumption by 0.65 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> -78 <inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> .

Investigation on thermal failure of functionally graded materials using fully coupled thermo-mechanical peridynamics

Investigation on thermal failure of functionally graded materials using fully coupled thermo-mechanical peridynamics

Understanding of thermal runaway mechanism of LiFePO4 battery in-depth by three-level analysis

The complex chemical composition and material interactions of lithium-ion batteries challenge the in-depth understanding of thermal runaway reactions and failure mechanisms. In this study, detailed analysis and implementation have been made from three levels to further explain the thermal failure mechanism, from material interactions to cell-level experiments and applications. The LiFePO4 thermal runaway mechanism is put forward to characterize exothermic peaks from differential analysis of differential scanning calorimetry (DSC) and Accelerating Rate Calorimetry (ARC) data. Furthermore, the development, parameterization, and application of the thermal runaway prediction model are also discussed. Multi-heating rate data is a prerequisite to kinetic analysis and modeling work and provides valuable data set for LiFePO4 thermal failure. And the unraveled mechanism is believed to provide a profound understanding of the thermal failure mechanism, strengthening interactions between material characterization and thermal runaway modeling.

Thermal monitoring of lithium-ion batteries based on machine learning and fibre Bragg grating sensors

Lithium-ion batteries (LiBs) are well-known power sources due to their higher power and energy densities, longer cycle life and lower self-discharge rate features. Hence, these batteries have been widely used in various portable electronic devices, electric vehicles and energy storage systems. The primary challenge in applying a Lithium-ion battery (LiB) system is to guarantee its operation safety under both normal and abnormal operating conditions. To achieve this, temperature management of batteries should be placed as a priority for the purpose of achieving better lifetime performance and preventing thermal failures. In this paper, fibre Bragg Grating (FBG) sensor technology coupling with machine learning (ML) has been explored for battery temperature monitoring. The results based on linear and nonlinear models have confirmed that the novel methods can estimate temperature variations reliably and accurately.

Experimental study and numerical analysis of vacuum thermal characteristics of brush DC motor

Brush direct current (DC) motors have several qualities that make them very attractive for space flight applications. Considering the high reliability requirements of aerospace missions, the thermal characteristics and thermal failure of the brush DC motor in the space environment were studied. Using a motor thermal resistance network model, a special thermal test method was determined and combined with a thermal conductivity analysis model, the thermal parameters were obtained via item-by-item stripping, and the motor temperature field was constructed. By introducing the arc discharge factor to evaluate the electric-corrosion heat consumption, the numerical analysis results were in good agreement with the test results under the conditions of stalled rotor, normal rotation, single brush, and multiple brushes. The analysis and test results show that continuous operation for 110 s will lead to melting of the brush solder joints, and electrical corrosion heat consumption is one of the main factors that cannot be ignored. The reliability model of vacuum applications should be established in the normal working mode of at least two brushes in both the positive and negative electrodes. To improve the reliability, a sealed air-filled structure of the motor was proposed, a heat-flow co-simulation model of a continuous medium flow with a large curvature and constant without a gravity field was established, and the temperature and velocity fields under different sealed pressures were obtained. The results show that the temperature of the single brush reduced to below 140 °C from 204.5 °C in vacuum, which can meet the long-term continuous working requirement of high reliability of brush motors in space missions. In addition, it was found that with the decrease in pressure, the effect of convective heat transfer gradually weakens, the temperature gradually increases and converges to the unique heat conduction process of the gas, while the effect of convection is negligible. As the pressure continues to decrease, the sealed gas evolves from continuous medium flow to transitional and free molecular flow, and the heat conduction effect of the gas weakens again until it approaches the singleness solid conduction process.

Probing the thermal degradation mechanism of polycrystalline and single-crystal Li(Ni0.8Co0.1Mn0.1)O2 cathodes from the perspective of oxygen vacancy diffusion

The Ni-rich cathode is one of the most promising materials for application in high-energy-density lithium-ion batteries. However, the inherent thermal instability of this material raises the risk of thermal runaway, which presents a significant obstacle to its eventual commercialization. At present, the in-depth mechanism of how grain structure affects the thermal stability of Ni-rich cathodes remains unclear. In this work, we study the thermal degradation behavior of polycrystalline and single-crystal NCM811 cathodes from multiple dimensions based on a series of state-of-the-art physicochemical characterization tools combined with theoretical calculations, report different degradation pathways of polycrystalline and single-crystal cathodes, and investigate the enhancement mechanism of single-crystal structure on the thermal stability of cathodes from the atomic scale. The larger grain size and better integrity of single-crystal NCM811 particle effectively retard the oxygen vacancy formation and increase oxygen vacancy diffusion paths at high temperatures. As a result, the diffusion of oxygen vacancies is kinetically unfavorable during heating, which delays the degradation of its lattice structure and the release of oxygen. This work provides insight into the thermal failure mechanisms of Ni-rich cathode materials with different grain structures and offers an essential theoretical basis for designing future thermally stable cathode materials.

Feasibility research of Yb3Al5O12 garnet as environmental barrier coating materials

In this work, Yb3Al5O12 (YbAG) garnet, as a new material for environment barrier coating (EBC) application, was synthesized and prepared by atmospheric plasma spraying (APS). The phases and microstructures of the coatings were characterized by XRD, EDS and SEM, respectively. The thermal stability was measured by TG-DSC. The mechanical and thermal-physical properties, including Vickers hardness (Hv), fracture toughness (KIC), Young's modulus (E), thermal conductivity (κ) and coefficient of thermal expansion (CTE) were also measured. The results showed that the as-sprayed coating was mainly composed of crystalline Yb3Al5O12 and amorphous phase which crystallized at around 917 °C. Moreover, it has a hardness of 6.81 ± 0.23 GPa, fracture toughness of 1.61 ± 0.18 MPa m1/2, as well as low thermal conductivity (0.82–1.37 W/m·K from RT-1000 °C) and an average coefficient of thermal expansion (CTE) (∼6.3 × 10−6 K−1 from RT to 660 °C). In addition, the thermal shock and water-vapor corrosion behaviors of the Yb3Al5O12-EBC systems on the SiCf/SiC substrates were investigated and their failure mechanisms were analyzed in details. The Yb3Al5O12 coating has an average thermal shock lifetime of 72 ± 10 cycles as well as an excellent resistance to steam. These combined properties indicated that the Yb3Al5O12 coating might be a potential EBC material. Both the thermal shock failure and the steam recession of the Yb3Al5O12-EBC systems are primarily associated with the CTE mismatch stress.

ENERGY EFFICIENCY OF THE HEATING SYSTEM OF THE PSACEA HIGH-RISE BUILDING

The research aims to deepen the methodological and organisational-practical principles of energy efficiency for further application in the educational buildings thermal modernization.&#x0D; The relevance of the work is to reduce energy consumption by increasing the energy efficiency of buildings. Based on the calculations and research, the following scientific and practical results were obtained:&#x0D; - a technical inspection of the educational building heating system was conducted;&#x0D; - a thermal imaging survey was conducted and infiltration thermal failures of the building's heating system were detected;&#x0D; - the energy efficiency class of the building before thermal renovation is determined;&#x0D; - economic expediency of the heating system thermal modernization was proposed and calculated.&#x0D; - the energy efficiency class of the building after thermal renovation is determined.&#x0D; As an outcome of obtaining scientific and practical results for the heating system thermal failures, indicating the need to introduce measures to reduce the amount of thermal energy losses, ways for the heating system thermal modernization are proposed.&#x0D; The obtained scientific and practical implications of the research work can be used in the future on similar objects, as an example for increasing the energy efficiency level.

Thermal failure of diamond tools indicated by diamond degradation: Damage evaluation and property prediction on small image datasets

High temperature induced diamond degradation often leads to the failure of diamond tools. In this work, diamond samples holding different degrees of thermal damage were prepared by heating and sintering. The influence of diamond particle size and processing temperature was investigated through mechanical testing and micromorphology observation, meanwhile, a dataset containing 2870 SEM images showing diamonds with different degrees of degradation was constructed. By modification of VGG16 network, classification models and regression models were developed for thermal damage evaluation and sample property prediction. Training strategies including transfer learning and data augmentation were implemented and verified essential on the small dataset, where drop-out showed no positive effects. Two classification models (3-class and 65-class) were constructed and trained for damage evaluation. Visualized damage feature maps exported from Grad-CAM revealed the influential mechanism of thermal damage on diamonds, which proved the effectiveness of the classification models as well. Under the optimized training strategies, regression models were built for sample property prediction. The models towards toughness index, bending strength loss, relative density and Rockwell hardness were examined. Comparing the output results with real property values in test sets, the first two models matched well, and the latter two showed the opposite. It verified the validity of the regression models for property prediction as they were all established based on diamond damage image datasets. The loss in bending strength loss prediction model was smaller than that of toughness index, indicating bending strength easier to be shorten than impact toughness for diamond/metal composites suffering thermal impacts.