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 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 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.

In enclosed spaces such as battery packs or battery compartments, the jet impact generated by thermal runaway of aviation lithium batteries can cause significant damage to structures. This paper uses high-temperature impact, impact force, and impulse as evaluation parameters. An independently constructed jet impact experimental platform is employed to quantitatively study the damage degree of battery pack or battery compartment structure in actual use scenarios through measured data. Moreover, we also analyze the impact of battery state of charge, impact distance between battery and structure, and compartment thickness on the impact hazard of battery thermal runaway jet impact. The experiment showed that when the 100% State of Charge (SOC) battery had thermal runaway, the 1.0 mm and 1.2 mm thickness experimental plates were perforated to varying degrees after being impacted, with the maximum perforation area reaching 136.488 mm². The 1.5 mm thickness experimental cabin did not perforate and achieved effective containment. As the impact distance increases from 1 cm to 3 cm, the peak temperature of the experimental plate back plate decreases significantly, with an average decrease rate of 47.5 ℃/cm per unit distance; the maximum impact force increases accordingly, with an average unit distance growth rate of 142.95 N/cm. In summary, to control the thickness of the plate to meet the lightweight design, it is necessary to comprehensively analyze the thermal runaway spray temperature and impact hazard, and reasonably select the gap distance between the battery and the shell or the upper wall panel of the cabin to achieve the containment of the thermal runaway high-temperature spray impact by the battery pack or cabin.

By analyzing the impact of mechanical vibration on the safety of lithium ion batteries in various application scenarios, such as transportation and aerospace, the 18650 battery was used as a sample, and the.influence of vibration conditions on the internal structure, cyclic aging mechanism, electrical performance, and thermal runaway characteristics of lithium ion batteries was investigated. The results indicate that vibration can significantly induce alterations in the internal microstructure of lithium ion batteries. Prolonged exposure to vibration stress can lead to deformation of the negative electrode collector, resulting in compression on the electrode roll. Additionally, momentary vibration stress can dynamically affect the contact area between the electrode material and the diaphragm, impeding the migration of lithium ions during the embedding and de-embedding processes. Consequently, this exacerbates the fluctuation of Coulomb efficiency and energy efficiency, leading to insufficient discharge under vibration conditions. Furthermore, thermal runaway experiments demonstrate that the time required to trigger thermal runaway shortens as the duration of vibration increases. Compared with that of non-vibrating batteries, the initial explosion time of thermal runaway of batteries subjected to 600 hours of vibration shortens to 72 seconds, and the combustion-induced explosion time shortens to 114 seconds. Meanwhile, the interval between initial and combustion-induced explosions is shortened. Moreover, the instability of the impact force produced by combustion-induced explosion increases.