2025 Vol. 45, No. 2
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2025, 45(2): 021411.
doi: 10.11883/bzycj-2024-0329
Abstract:
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. Quasi-static and dynamic compression experiments were conducted under a wide range of strain rates and temperatures. These tests assessed the mechanical behavior and damage mechanism of separator at elevated temperatures and different strain rates. The strain rate-dependent and temperature-dependent mechanical properties of the separator was meticulously explored. The results indicated that the mechanical behavior of separator is highly sensitive to both the strain rate and the temperature. As the strain rate increases, the yield point of the separator decreases. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with the temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. Quasi-static and dynamic compression experiments were conducted under a wide range of strain rates and temperatures. These tests assessed the mechanical behavior and damage mechanism of separator at elevated temperatures and different strain rates. The strain rate-dependent and temperature-dependent mechanical properties of the separator was meticulously explored. The results indicated that the mechanical behavior of separator is highly sensitive to both the strain rate and the temperature. As the strain rate increases, the yield point of the separator decreases. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with the temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
2025, 45(2): 021412.
doi: 10.11883/bzycj-2024-0339
Abstract:
The deformation and failure of the internal separator in a lithium-ion battery under external impacts is one of the crucial factors in triggering internal short circuits. The surfaces of battery electrodes are usually not smooth, which tends to cause stress concentration on the separator, affecting the mechanical stability of the battery. Therefore, based on numerical simulation and theoretical analysis, this study conducted an in-depth exploration of the mechanical behavior of the battery separator under the condition of being compressed on a non-smooth surface and its short-circuit safety boundaries. A representative unit cell, including a section of the separator with a width of 50 μm and the nearby cathode and anode coating areas, was selected for two-dimensional finite element modeling and numerical calculation. The study compares three forms of the surface morphology: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, to understand the effects of particle size, separator thickness, and loading rate. By analyzing the equivalent stress-strain curves of the separator, it was found that the separator under compression on a non-smooth surface exhibited a softening phenomenon compared with that under ideal flat surface compression. For the ideal plane case, the strain distribution is very uniform, so the load-bearing capacity of the battery is larger. However, for the cases of densely packed granular and single granular protrusion, under the same loading displacement, the loaded area is small, and the generated reaction force is also small. As the loading process proceeded, the gaps were gradually filled, the loaded area increased, and gradually tended to be loaded on the entire surface, and the load difference gradually decreased. Through the parametric analysis of the failure stress of the separator, it was discovered that with the increase in particle diameter, the decrease in separator thickness, or the increase in loading rate within a certain range, the separator exhibited softening behaviors such as a decrease in average stress and a backward shift of the yield point, and the short-circuit failure stress also decreased accordingly. Furthermore, by establishing an equivalent compressive constitutive model of the separator under compression on a non-smooth surface, the influence of roughness on the failure stress was theoretically explained, and the quantitative relationship between the two was deduced.
The deformation and failure of the internal separator in a lithium-ion battery under external impacts is one of the crucial factors in triggering internal short circuits. The surfaces of battery electrodes are usually not smooth, which tends to cause stress concentration on the separator, affecting the mechanical stability of the battery. Therefore, based on numerical simulation and theoretical analysis, this study conducted an in-depth exploration of the mechanical behavior of the battery separator under the condition of being compressed on a non-smooth surface and its short-circuit safety boundaries. A representative unit cell, including a section of the separator with a width of 50 μm and the nearby cathode and anode coating areas, was selected for two-dimensional finite element modeling and numerical calculation. The study compares three forms of the surface morphology: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, to understand the effects of particle size, separator thickness, and loading rate. By analyzing the equivalent stress-strain curves of the separator, it was found that the separator under compression on a non-smooth surface exhibited a softening phenomenon compared with that under ideal flat surface compression. For the ideal plane case, the strain distribution is very uniform, so the load-bearing capacity of the battery is larger. However, for the cases of densely packed granular and single granular protrusion, under the same loading displacement, the loaded area is small, and the generated reaction force is also small. As the loading process proceeded, the gaps were gradually filled, the loaded area increased, and gradually tended to be loaded on the entire surface, and the load difference gradually decreased. Through the parametric analysis of the failure stress of the separator, it was discovered that with the increase in particle diameter, the decrease in separator thickness, or the increase in loading rate within a certain range, the separator exhibited softening behaviors such as a decrease in average stress and a backward shift of the yield point, and the short-circuit failure stress also decreased accordingly. Furthermore, by establishing an equivalent compressive constitutive model of the separator under compression on a non-smooth surface, the influence of roughness on the failure stress was theoretically explained, and the quantitative relationship between the two was deduced.
2025, 45(2): 021421.
doi: 10.11883/bzycj-2024-0312
Abstract:
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with the continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the influence of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the ability to withstand secondary loads of the battery and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and optimizing safety standards for their continued use in collision-prone environments.
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with the continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the influence of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the ability to withstand secondary loads of the battery and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and optimizing safety standards for their continued use in collision-prone environments.
2025, 45(2): 021422.
doi: 10.11883/bzycj-2024-0368
Abstract:
Unavoidable electric vehicle collisions can cause defects in lithium-ion batteries, and whether defective batteries after minor collisions can continue to be used is still unknown. In this work, we focus on the mechanical performance and electrochemical performance of defective batteries, safety boundaries, and its failure mechanism. Firstly, three typical defects , namely indentation, 50%-offset compression defect and plate-compression defect, were prepared by quasi-static loading and drop-hammer impact with different indenters. The defective batteries did not exhibit voltage drops or temperature increases, indicating that no internal short circuits occurred. Subsequently, their mechanical and electrochemical responses were evaluated through quasi-static plate compression at a loading rate of 1 mm/min and 1C charge/discharge cycling, respectively. It was found that the defective batteries exhibited significant deterioration in mechanical performance, including earlier onset of internal short circuit, reduced short circuit force, and decreased energy absorption capacity. Defective batteries also exhibited significant electrochemical performance degradation, with greater capacity loss during cycling compared to new batteries. Further, its degradation mechanism was explained through disassembling the cells. The separator of the defective batteries exhibited significant thinning, making it more prone to rupture under secondary loading. Therefore, the mechanical failure criterion of the batteries was proposed based on the separator thickness. After 500 cycles, graphite delamination was observed in the defective batteries, whereas the defective batteries without cycling only exhibited cracking. Therefore, the degradation of electrochemical performance in defective batteries was caused by the combined effects of initial defects and cyclic aging stress. The effects of loading speed and defect type on the performance of defective cells were also discussed. Defective batteries subjected to higher loading rates exhibit greater performance degradation, which is related to inertia effects. Different types of defects lead to variations in separator thickness and graphite delamination, resulting in different levels of degradation. Results are instructive for the study of safety identification and treatment of defective lithium-ion batteries.
Unavoidable electric vehicle collisions can cause defects in lithium-ion batteries, and whether defective batteries after minor collisions can continue to be used is still unknown. In this work, we focus on the mechanical performance and electrochemical performance of defective batteries, safety boundaries, and its failure mechanism. Firstly, three typical defects , namely indentation, 50%-offset compression defect and plate-compression defect, were prepared by quasi-static loading and drop-hammer impact with different indenters. The defective batteries did not exhibit voltage drops or temperature increases, indicating that no internal short circuits occurred. Subsequently, their mechanical and electrochemical responses were evaluated through quasi-static plate compression at a loading rate of 1 mm/min and 1C charge/discharge cycling, respectively. It was found that the defective batteries exhibited significant deterioration in mechanical performance, including earlier onset of internal short circuit, reduced short circuit force, and decreased energy absorption capacity. Defective batteries also exhibited significant electrochemical performance degradation, with greater capacity loss during cycling compared to new batteries. Further, its degradation mechanism was explained through disassembling the cells. The separator of the defective batteries exhibited significant thinning, making it more prone to rupture under secondary loading. Therefore, the mechanical failure criterion of the batteries was proposed based on the separator thickness. After 500 cycles, graphite delamination was observed in the defective batteries, whereas the defective batteries without cycling only exhibited cracking. Therefore, the degradation of electrochemical performance in defective batteries was caused by the combined effects of initial defects and cyclic aging stress. The effects of loading speed and defect type on the performance of defective cells were also discussed. Defective batteries subjected to higher loading rates exhibit greater performance degradation, which is related to inertia effects. Different types of defects lead to variations in separator thickness and graphite delamination, resulting in different levels of degradation. Results are instructive for the study of safety identification and treatment of defective lithium-ion batteries.
2025, 45(2): 021423.
doi: 10.11883/bzycj-2024-0316
Abstract:
Electric vehicles are prone to collision accidents during operation, and power lithium-ion batteries are inevitably subjected to impact, which leads to varying degrees of damage to the battery, and assessing the extent of this damage is crucial for the safe use of the battery. Based on the above background, the study was conducted on the influence of different impact masses on the dynamic impact response and failure behavior of square lithium-ion batteries. Firstly, in the quasi-static compression test, six different feed rates were used to test the extrusion of lithium-ion batteries. The test results show that the peak load required for lithium-ion batteries to reach hard short-circuit failure continues to decrease with the increment of feed rate. This indicates that the short-circuit failure load of lithium-ion batteries under quasi-static conditions is mainly determined by the feed rate. Then the hammer impact test, through the regulation of the quality of the punch and impact speed, the system simulates the lithium-ion battery may encounter a variety of impact conditions. Impact quality is an important factor in determining the degree of damage to lithium-ion batteries. Under the same impact energy, the damage of low-speed large mass impact on lithium-ion battery is significantly higher than that of high-speed low mass impact. At a constant impact energy, mass is the dominant factor in determining the degree of battery damage. If the impact mass is heavier, it will produce a larger impact load, which will cause more serious damage to the internal structure of the lithium-ion battery, leading to its functional damage or even failure. Conversely, if the impact mass is lighter, the impact force generated is relatively small, and the damage to the battery structure is correspondingly reduced. Therefore, the size of the impact mass directly affects the degree of damage to the lithium-ion battery, which is a key indicator for evaluating its safety performance and durability. The impact speed has a significant impact on the voltage drop of lithium-ion batteries after damage. Especially accelerating the occurrence of hard short circuits, further exacerbating the sharp drop in voltage. This characteristic makes the impact velocity as an important consideration for evaluating the voltage stability and overall safety performance of lithium-ion batteries after damage.
Electric vehicles are prone to collision accidents during operation, and power lithium-ion batteries are inevitably subjected to impact, which leads to varying degrees of damage to the battery, and assessing the extent of this damage is crucial for the safe use of the battery. Based on the above background, the study was conducted on the influence of different impact masses on the dynamic impact response and failure behavior of square lithium-ion batteries. Firstly, in the quasi-static compression test, six different feed rates were used to test the extrusion of lithium-ion batteries. The test results show that the peak load required for lithium-ion batteries to reach hard short-circuit failure continues to decrease with the increment of feed rate. This indicates that the short-circuit failure load of lithium-ion batteries under quasi-static conditions is mainly determined by the feed rate. Then the hammer impact test, through the regulation of the quality of the punch and impact speed, the system simulates the lithium-ion battery may encounter a variety of impact conditions. Impact quality is an important factor in determining the degree of damage to lithium-ion batteries. Under the same impact energy, the damage of low-speed large mass impact on lithium-ion battery is significantly higher than that of high-speed low mass impact. At a constant impact energy, mass is the dominant factor in determining the degree of battery damage. If the impact mass is heavier, it will produce a larger impact load, which will cause more serious damage to the internal structure of the lithium-ion battery, leading to its functional damage or even failure. Conversely, if the impact mass is lighter, the impact force generated is relatively small, and the damage to the battery structure is correspondingly reduced. Therefore, the size of the impact mass directly affects the degree of damage to the lithium-ion battery, which is a key indicator for evaluating its safety performance and durability. The impact speed has a significant impact on the voltage drop of lithium-ion batteries after damage. Especially accelerating the occurrence of hard short circuits, further exacerbating the sharp drop in voltage. This characteristic makes the impact velocity as an important consideration for evaluating the voltage stability and overall safety performance of lithium-ion batteries after damage.
2025, 45(2): 021424.
doi: 10.11883/bzycj-2024-0320
Abstract:
This paper takes the soft-package lithium-ion batteries as the research objects to study the dynamic response modes and explosion ignition characteristics of lithium-ion batteries used in light-weight and small consumer unmanned aerial vehicles (UAVs) under high-energy impact and evaluate the safety performances of lithium batteries under dynamic impact. The drop hammer and gas gun were used to carry out the drop-hammer impact of the soft-package battery pack and the high-speed impact of the battery on the aluminum plate. The deformation modes and ignition characteristics of the soft-package lithium-ion batteries under different battery powers after impact were studied. Based on the mechanical deformation response and ignition characteristics of the batteries, the impact safety of small soft-package lithium-ion batteries was analyzed. The results show that the ignition risk of small soft-package lithium-ion batteries under conventional battery shell protection after being impacted by loads in the out-of-plane direction is much higher than that impacted in the in-plane direction. The ignition risk of lithium-ion batteries is related to battery power and impact velocity. The thickness of the impacted aluminum plate has little effect on the ignition risk of lithium-ion batteries. The lithium-ion battery samples used in this study all have a relatively low risk of combustion after impacting the aluminum plate at the velocity of 50 m/s with the state of charge of 100%, and at the velocity of 85 m/s with the states of charge of less than 50%, respectively.
This paper takes the soft-package lithium-ion batteries as the research objects to study the dynamic response modes and explosion ignition characteristics of lithium-ion batteries used in light-weight and small consumer unmanned aerial vehicles (UAVs) under high-energy impact and evaluate the safety performances of lithium batteries under dynamic impact. The drop hammer and gas gun were used to carry out the drop-hammer impact of the soft-package battery pack and the high-speed impact of the battery on the aluminum plate. The deformation modes and ignition characteristics of the soft-package lithium-ion batteries under different battery powers after impact were studied. Based on the mechanical deformation response and ignition characteristics of the batteries, the impact safety of small soft-package lithium-ion batteries was analyzed. The results show that the ignition risk of small soft-package lithium-ion batteries under conventional battery shell protection after being impacted by loads in the out-of-plane direction is much higher than that impacted in the in-plane direction. The ignition risk of lithium-ion batteries is related to battery power and impact velocity. The thickness of the impacted aluminum plate has little effect on the ignition risk of lithium-ion batteries. The lithium-ion battery samples used in this study all have a relatively low risk of combustion after impacting the aluminum plate at the velocity of 50 m/s with the state of charge of 100%, and at the velocity of 85 m/s with the states of charge of less than 50%, respectively.
2025, 45(2): 021425.
doi: 10.11883/bzycj-2024-0321
Abstract:
To clarify the influence of the discharge state on the dynamic mechanical response and failure mode of lithium-ion batteries, an experimental analysis of the quasi-static compression characteristics and safety performance of lithium-ion batteries under different discharge states was systematically conducted. By presetting the battery to a specific discharge capacity and conducting compression tests at the time nodes of 1 and 24 h after standing during and after the discharge process, the force-displacement response characteristics, maximum load-bearing capacity and safety performance of the battery were thoroughly explored under varying electrochemical states. The experimental results show that, compared with other states, the battery in the discharge state exhibits a lower force-displacement curve, indicating that its stiffness increases after standing compared with that during the discharge process and this decrease is attributed to the electro-chemical reaction inside the battery during the discharge process. In addition, the battery in the discharge state shows a significantly higher maximum load-bearing capacity than that in the standing state after discharge, and the compression test during the discharge process is more likely to cause the battery to explode, while the battery after standing shows a significantly improved safety. The analysis using scanning electron microscope (SEM) further indicates that the damage degree of the internal electrode particles of the battery in the discharge state is more severe. The observed damage and increased risk of mechanical failure are primarily attributed to the diffusion-induced stress generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical compression. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
To clarify the influence of the discharge state on the dynamic mechanical response and failure mode of lithium-ion batteries, an experimental analysis of the quasi-static compression characteristics and safety performance of lithium-ion batteries under different discharge states was systematically conducted. By presetting the battery to a specific discharge capacity and conducting compression tests at the time nodes of 1 and 24 h after standing during and after the discharge process, the force-displacement response characteristics, maximum load-bearing capacity and safety performance of the battery were thoroughly explored under varying electrochemical states. The experimental results show that, compared with other states, the battery in the discharge state exhibits a lower force-displacement curve, indicating that its stiffness increases after standing compared with that during the discharge process and this decrease is attributed to the electro-chemical reaction inside the battery during the discharge process. In addition, the battery in the discharge state shows a significantly higher maximum load-bearing capacity than that in the standing state after discharge, and the compression test during the discharge process is more likely to cause the battery to explode, while the battery after standing shows a significantly improved safety. The analysis using scanning electron microscope (SEM) further indicates that the damage degree of the internal electrode particles of the battery in the discharge state is more severe. The observed damage and increased risk of mechanical failure are primarily attributed to the diffusion-induced stress generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical compression. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
2025, 45(2): 021431.
doi: 10.11883/bzycj-2024-0175
Abstract:
The safety of propulsion lithium-ion batteries is a technical bottleneck to restrict the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium-ion batteries will cause catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the latest research status on the thermal runaway explosion characteristics of aircraft lithium-ion battery from three aspects, i.e., lithium-ion battery’s thermal runaway combustion and explosion behavior, the limit of thermal runaway gas explosion and the hazard assessment of thermal runaway and gas explosion. For lithium-ion battery thermal runaway and explosion behaviors, this paper introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the characteristic parameters of the thermal runaway shock and summarized the evolution of the thermal jet mechanism as well as the associated simulation and experimental methods. For the limit of thermal runaway gas explosion, the national and international testing standards for the gas explosion limit were compared and the theoretical calculation of the explosion limit of thermal runaway gas are summarized together with the introduction of the in-situ detection method of the gas explosion limit. For the thermal runaway gas explosion risk assessment, a risk assessment method of ageing lithium-ion battery is introduced by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method, from which a severity factor of gas explosion hazard is obtained. Based on the characteristics of lithium-ion battery’s thermal runaway gas explosion limit and pressure rise rate, the factors of explosion risk and severity are obtained together with the formula for the calculation of explosion risk and severity. This study shows that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research should focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques and the establishment of standardized test procedures and technical regulations.
The safety of propulsion lithium-ion batteries is a technical bottleneck to restrict the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium-ion batteries will cause catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the latest research status on the thermal runaway explosion characteristics of aircraft lithium-ion battery from three aspects, i.e., lithium-ion battery’s thermal runaway combustion and explosion behavior, the limit of thermal runaway gas explosion and the hazard assessment of thermal runaway and gas explosion. For lithium-ion battery thermal runaway and explosion behaviors, this paper introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the characteristic parameters of the thermal runaway shock and summarized the evolution of the thermal jet mechanism as well as the associated simulation and experimental methods. For the limit of thermal runaway gas explosion, the national and international testing standards for the gas explosion limit were compared and the theoretical calculation of the explosion limit of thermal runaway gas are summarized together with the introduction of the in-situ detection method of the gas explosion limit. For the thermal runaway gas explosion risk assessment, a risk assessment method of ageing lithium-ion battery is introduced by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method, from which a severity factor of gas explosion hazard is obtained. Based on the characteristics of lithium-ion battery’s thermal runaway gas explosion limit and pressure rise rate, the factors of explosion risk and severity are obtained together with the formula for the calculation of explosion risk and severity. This study shows that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research should focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques and the establishment of standardized test procedures and technical regulations.
2025, 45(2): 021432.
doi: 10.11883/bzycj-2024-0352
Abstract:
The thermal runaway reactions of lithium-ion batteries exhibit significant deviations following full life-cycle cycling aging when compared to their fresh-state counterparts, particularly under low-temperature conditions. These conditions more closely simulate the operational scenarios encountered in low-altitude aviation, where the risk of catastrophic failure in battery systems is heightened. This study, utilizing a custom-built platform designed for testing thermal runaway and gas explosion phenomena, systematically investigates the impact of low-temperature (−10 °C) cycling aging on the associated explosion hazards. Key parameters analyzed in this research include the initiation time of thermal runaway, the peak surface temperature of the battery, the overpressure generated during thermal runaway, the lower explosion limit (LEL) of the gases produced, and the explosion pressure and temperature, serving as crucial indicators of the system’s safety performance. Experimental results demonstrate that, under ambient temperature conditions, aged batteries exhibit a marked increase in the thermal runaway initiation time, as well as a notable extension in the interval between the activation of the safety valve and the onset of complete thermal runaway (Δt), when compared to fresh batteries. Specifically, thermal runaway occurs at 559.86 s, while Δt increases to 122.56 s. Moreover, the LEL of hazardous gases rises by 30.95%, and the resulting explosion pressure diminishes to 258.6 kPa, suggesting a reduced likelihood of catastrophic failure. However, when subjected to low-temperature cycling aging, the explosion risk profile shifts dramatically. In this case, the thermal runaway initiation time is significantly reduced to 412.38 s, with Δt contracting sharply to 56.66 s. Furthermore, the LEL of the gases decreases by 20.49%, while the explosion pressure surges to 319.5 kPa, indicating an elevated risk of severe explosion. The multifaceted analysis of these hazard indicators reveals a complex interplay between aging processes and environmental conditions, profoundly influencing the explosion risks and thermal runaway behavior of lithium-ion batteries. These findings emphasize the critical necessity of developing advanced battery management systems that incorporate predictive early-warning mechanisms, strategic battery layout designs, and improved containment strategies, specifically tailored to the demands of electric aviation. By incorporating the effects of both cycling aging and low-temperature environments into risk assessments, this study provides vital insights for mitigating the elevated hazards associated with thermal runaway and the explosion of emitted gases in aviation applications. Ultimately, these findings contribute to the enhancement of safety protocols and risk mitigation strategies for the reliable and secure operation of lithium-ion battery systems throughout their entire operational lifecycle.
The thermal runaway reactions of lithium-ion batteries exhibit significant deviations following full life-cycle cycling aging when compared to their fresh-state counterparts, particularly under low-temperature conditions. These conditions more closely simulate the operational scenarios encountered in low-altitude aviation, where the risk of catastrophic failure in battery systems is heightened. This study, utilizing a custom-built platform designed for testing thermal runaway and gas explosion phenomena, systematically investigates the impact of low-temperature (−10 °C) cycling aging on the associated explosion hazards. Key parameters analyzed in this research include the initiation time of thermal runaway, the peak surface temperature of the battery, the overpressure generated during thermal runaway, the lower explosion limit (LEL) of the gases produced, and the explosion pressure and temperature, serving as crucial indicators of the system’s safety performance. Experimental results demonstrate that, under ambient temperature conditions, aged batteries exhibit a marked increase in the thermal runaway initiation time, as well as a notable extension in the interval between the activation of the safety valve and the onset of complete thermal runaway (Δt), when compared to fresh batteries. Specifically, thermal runaway occurs at 559.86 s, while Δt increases to 122.56 s. Moreover, the LEL of hazardous gases rises by 30.95%, and the resulting explosion pressure diminishes to 258.6 kPa, suggesting a reduced likelihood of catastrophic failure. However, when subjected to low-temperature cycling aging, the explosion risk profile shifts dramatically. In this case, the thermal runaway initiation time is significantly reduced to 412.38 s, with Δt contracting sharply to 56.66 s. Furthermore, the LEL of the gases decreases by 20.49%, while the explosion pressure surges to 319.5 kPa, indicating an elevated risk of severe explosion. The multifaceted analysis of these hazard indicators reveals a complex interplay between aging processes and environmental conditions, profoundly influencing the explosion risks and thermal runaway behavior of lithium-ion batteries. These findings emphasize the critical necessity of developing advanced battery management systems that incorporate predictive early-warning mechanisms, strategic battery layout designs, and improved containment strategies, specifically tailored to the demands of electric aviation. By incorporating the effects of both cycling aging and low-temperature environments into risk assessments, this study provides vital insights for mitigating the elevated hazards associated with thermal runaway and the explosion of emitted gases in aviation applications. Ultimately, these findings contribute to the enhancement of safety protocols and risk mitigation strategies for the reliable and secure operation of lithium-ion battery systems throughout their entire operational lifecycle.
2025, 45(2): 021433.
doi: 10.11883/bzycj-2024-0240
Abstract:
The thermal shock caused by thermal runaway of lithium-ion batteries causes damage in the installation structure and poses a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for thermal runaway of lithium battery, it was found that the impact pressure on the pack top plate of battery from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature beyond 274 °C. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method that involves applying a fireproof coating to the top plate of the battery pack. is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure induced by thermal runaway of a lithium-ion battery by expanding, and absorbing heat, thereby reducing and delaying the temperature rise of the top plate of the battery pack, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1.0-mm-thickness coating is more suitable for practical application requirements. Referring to relevant airworthiness regulations, verification tests were conducted on the thermal runaway containment of lithium battery. The analysis of the experiment results shows that the 1.0-mm-thickness E80S20 coating and E85S15B3 coating reduced the maximum temperature of the top plate of the battery pack by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that the passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium-ion battery systems.
The thermal shock caused by thermal runaway of lithium-ion batteries causes damage in the installation structure and poses a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for thermal runaway of lithium battery, it was found that the impact pressure on the pack top plate of battery from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature beyond 274 °C. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method that involves applying a fireproof coating to the top plate of the battery pack. is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure induced by thermal runaway of a lithium-ion battery by expanding, and absorbing heat, thereby reducing and delaying the temperature rise of the top plate of the battery pack, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1.0-mm-thickness coating is more suitable for practical application requirements. Referring to relevant airworthiness regulations, verification tests were conducted on the thermal runaway containment of lithium battery. The analysis of the experiment results shows that the 1.0-mm-thickness E80S20 coating and E85S15B3 coating reduced the maximum temperature of the top plate of the battery pack by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that the passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium-ion battery systems.
2025, 45(2): 021434.
doi: 10.11883/bzycj-2023-0452
Abstract:
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
2025, 45(2): 021441.
doi: 10.11883/bzycj-2024-0318
Abstract:
The battery pack of electric vehicles is highly susceptible to failure and may catch fire under side pole collision. To accurately and rapidly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF) method, and back propagation neural network (BPNN) machine learning method were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average determination coefficient R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by Gaussian noise, where the BPNN exhibited better robustness. The BP model maintained an average R2 of 0.91 for the prediction parameters when Gaussian noise with a standard deviation of 0.5. The established data-driven model can effectively predict the mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating the battery pack safety.
The battery pack of electric vehicles is highly susceptible to failure and may catch fire under side pole collision. To accurately and rapidly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF) method, and back propagation neural network (BPNN) machine learning method were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average determination coefficient R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by Gaussian noise, where the BPNN exhibited better robustness. The BP model maintained an average R2 of 0.91 for the prediction parameters when Gaussian noise with a standard deviation of 0.5. The established data-driven model can effectively predict the mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating the battery pack safety.
2025, 45(2): 021442.
doi: 10.11883/bzycj-2024-0351
Abstract:
As lithium-ion batteries are widely used in the industry represented by electric vehicles, their collision-induced safety problems have aroused widespread concern in the industry and society. Under the collision condition of an electric vehicle, on the one hand, the deformation of the battery will lead to direct fire and explosion. On the other hand, the unknown deformation of the battery caused by the collision will bring safety risks to subsequent use. For the unknown deformation of batteries after the collision, abnormal batteries can only be perceived by physical signals such as voltage, temperature, and current, and there is no direct monitoring method for battery deformation. To bridge this gap, this paper uses small piezoelectric plates and realizes deformation and collision monitoring of lithium-ion batteries based on ultrasonic guided waves. An experimental platform for different loads of lithium-ion batteries was built, and quasi-static and micro-collision experiments were carried out. The experimental results were analyzed and discussed to clarify the change law of ultrasonic signals under different loads. The results show that in the quasi-static battery experiment, the ultrasonic amplitude signal was negatively correlated with the deformation degree of the battery. When the battery was subjected to a gradually increasing load and the deformation became more serious, the amplitude would gradually decrease; when the battery was deformed and failed, the amplitude would drop instantaneously. In the ball-dropping experiment, the impact deformation will affect the change of amplitude and energy integration of the ultrasonic signal, which can be used as a basis to judge whether the battery collision occurs. Finally, a mapping relationship between ultrasonic signal and battery deformation for failure monitoring under large deformation is established, and the criteria for collision deformation based on ultrasonic sensors is proposed. The results suggest a new method for the safety monitoring of lithium-ion batteries, which is expected to be applied in electric vehicles and other fields.
As lithium-ion batteries are widely used in the industry represented by electric vehicles, their collision-induced safety problems have aroused widespread concern in the industry and society. Under the collision condition of an electric vehicle, on the one hand, the deformation of the battery will lead to direct fire and explosion. On the other hand, the unknown deformation of the battery caused by the collision will bring safety risks to subsequent use. For the unknown deformation of batteries after the collision, abnormal batteries can only be perceived by physical signals such as voltage, temperature, and current, and there is no direct monitoring method for battery deformation. To bridge this gap, this paper uses small piezoelectric plates and realizes deformation and collision monitoring of lithium-ion batteries based on ultrasonic guided waves. An experimental platform for different loads of lithium-ion batteries was built, and quasi-static and micro-collision experiments were carried out. The experimental results were analyzed and discussed to clarify the change law of ultrasonic signals under different loads. The results show that in the quasi-static battery experiment, the ultrasonic amplitude signal was negatively correlated with the deformation degree of the battery. When the battery was subjected to a gradually increasing load and the deformation became more serious, the amplitude would gradually decrease; when the battery was deformed and failed, the amplitude would drop instantaneously. In the ball-dropping experiment, the impact deformation will affect the change of amplitude and energy integration of the ultrasonic signal, which can be used as a basis to judge whether the battery collision occurs. Finally, a mapping relationship between ultrasonic signal and battery deformation for failure monitoring under large deformation is established, and the criteria for collision deformation based on ultrasonic sensors is proposed. The results suggest a new method for the safety monitoring of lithium-ion batteries, which is expected to be applied in electric vehicles and other fields.
2025, 45(2): 021443.
doi: 10.11883/bzycj-2024-0188
Abstract:
This article studies the dynamic response characteristics of cylindrical lithium-ion batteries under large deformation based on the membrane factor method to improve the safety performance of batteries under radial dynamic impacting. Firstly, the battery was simplified to a sandwich beam consisting of a casing and an inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical and FE results of the displacement and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the stranger the axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with the initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant when the battery casing is thin. The maximum deflection of the battery decreases with the increase of casing thickness. Under a high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for failure prediction and structural safety design of batteries.
This article studies the dynamic response characteristics of cylindrical lithium-ion batteries under large deformation based on the membrane factor method to improve the safety performance of batteries under radial dynamic impacting. Firstly, the battery was simplified to a sandwich beam consisting of a casing and an inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical and FE results of the displacement and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the stranger the axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with the initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant when the battery casing is thin. The maximum deflection of the battery decreases with the increase of casing thickness. Under a high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for failure prediction and structural safety design of batteries.
