The primary concerns for individuals using lithium-ion batteries (LIBs) are aging and thermal runaway (TR). This paper focuses on the thermal runaway propagation (TRP) of cycling aged LIB modules. The impacts of state of charge (SOC), state of health, and cyclic aging temperature on TRP in LIB modules are investigated. The analysis includes parameters such as temperature, voltage, and mass of the modules during TRP. It was found that as SOC increases, the maximum increase in temperature and maximum temperature rate of the modules increased, as did the total mass loss and smoke emissions. The average heat transfer between adjacent cells was higher for the lower SOC. Cycle aging reduces the thermal stability of LIBs, leading to a lower maximum temperature and maximum temperature rate, as well as a larger mass loss compared with fresh battery modules. Regarding aging temperature, low-temperature aging reduces the total duration of TRP compared with room temperature, but it increases the maximum temperature rate and causes greater mass loss. Aging also increases the average heat transfer between adjacent cells.

Temperature is an important factor affecting the working efficiency and service life of lithium-ion battery (LIB). This study carried out the experiments on the thermal performances of Sanyo ternary and Sony LiFePO₄ batteries under different working conditions including extreme conditions, natural convection cooling and phase change material (PCM) cooling. The results showed that PCM could absorb some heat during the charging and discharging process, effectively reduce the temperature and keep the capacity stable. The average highest temperature of Sanyo LIB under PCM cooling was about 54.4 °C and decreased about 12.3 °C compared with natural convection in the 2 C charging and discharging cycles. It was found that the addition of heat dissipation fins could reduce the surface temperature, but the effect was not obvious. In addition, the charge and discharge cycles of the two kinds of LIBs were compared at the discharge rates of 1 C and 2 C. Compared with natural convection cooling, the highest temperature of Sanyo LIB with PCM cooling decreased about 4.7 °C and 12.8 °C for 1 C and 2 C discharging respectively, and the temperature of Sony LIB highest decreased about 1.1 °C and 2 °C.

Thermal management systems are critical to the maintenance of lithium-ion battery performance in new energy vehicles. While phase change materials are frequently employed in battery thermal management systems, it’s important to address the concerns related to their leakage and flammability, as they can pose hazards to the safety performance of batteries. This paper proposes a novel flame retardant composite phase change material (CPCM) consisting of paraffin, high-density polyethylene, expanded graphite, ammonium polyphosphate, red phosphorus, and zinc oxide. The performance of CPCMs containing different ratios of flame retardants is investigated, and their effects when applied to battery thermal management systems are compared. The results demonstrate that the leakage rate of the flame retardant CPCMs is maintained within 1%, indicating excellent flame retardant performance and thermal management efficiency. The combination of ammonium polyphosphate and red phosphorus in the flame retardant exhibits effective synergistic effects, while zinc oxide may help phosphate compounds create their bridging bonds, which would then make it possible to construct a char layer that would separate heat and oxygen. Under a 2C discharge rate, the maximum temperature of the battery pack remains below 50 °C, and the temperature difference can be controlled within 5 °C. Even under a 3C discharge rate, the maximum temperature and temperature difference are reduced by 30.31% and 29.53%, respectively.

Thermal runaway (TR) of lithium-ion batteries (LIBs) has always been the most important problem for battery development, and the TR characteristics of large LIBs need more research. In this paper, the thermal runaway propagation (TRP) characteristics and TR behavior changes of three lithium iron phosphate (LFP) batteries (numbered 1 to 3) under different states of charge (SOCs) were studied. The main parameters discussed include temperature, temperature rise rate, mass, mass change rate, and TRP flue gas ejection behavior. The experimental results indicate that with the increase in SOC, the TRP behavior of the battery is more obvious. The higher the temperature, more blocked temperature rise rate, mass loss rate, and greater mass loss, the shorter the TRP time that can be observed. The TRP interval of 100% SOC battery 1 to 2 is 71.4% smaller than that of 50% SOC, while the TRP interval of battery 2 to 3 is reduced by 87.2%. In addition, a 100% SOC battery pack exhibits spark ejection, while 50% SOC and 0% SOC battery pack exhibit flue gas generation.

Road traffic accidents pose significant challenges to sustainable urban safety and intelligent transportation management. The effective hazard identification of crash hotspots is crucial in implementing targeted safety measures. A severity-weighted system was adopted to quantify crash hazard levels. Using 1059 valid crash records of the City of London, the spatial correlations of crash points were first examined via average nearest neighbor analysis. Then, the optimal KDE bandwidth was determined via ArcGIS’s automatic extraction method, multi-distance spatial cluster analysis, and incremental spatial autocorrelation (ISA) analysis. The predictive accuracy index (PAI) was used to evaluate the accuracy of KDE results at various bandwidths. The results revealed a clustered spatial distribution of crash points. The optimized KDE bandwidth obtained via ISA analysis was 134 m, and the yielded PAI was 4.381, indicating better predictive accuracies and balanced hotspot distributions and reflecting both local concentrations and the overall continuity of crash hazard hotspots. Applying this bandwidth to the validation data allowed the successful identification of most high-risk areas and potential crash hazard hotspots attributed to traffic environmental factors; this method exhibits reliability, accuracy, and robustness over medium to long time scales. This workflow can serve as an analytical template for assisting planners in improving the identification accuracy of hazard hotspots, thereby reducing crash occurrences, actively promoting sustainable traffic safety development, and providing valuable insights for targeted crash prevention and intelligent traffic safety management in urban areas.

The thermal safety problem of lithium-ion batteries (LIB) in use requires an excellent thermal management system to preserve it. In the paper, an expansion flame-retardant composed of APP and CFA and kaolinite is used to enhance the flame-retardant property of phase change materials (PCM). The performances of PCM and their property in the thermal management of LIB were studied. The results indicate that the kaolinite can improve the long-term thermostability of PCM. The addition of flame retardant can make the flame-retardant property of PCM reach V0 level. The synergistic action of expansion flame-retardant and kaolinite can increase the residual carbon and enhance the thermal reliability of flame-retardant PCM (RPCM). The RPCM has an obvious cooling effect on the surface temperature of the battery. The RPCM can reduce the maximum temperature of the cell to 37.4 °C at 3 C, which is 12 °C lower than pure PA. The peak temperature of the battery pack at 3 C is also reduced to 50.28 °C by the flame-retardant PCM, and the temperature difference is kept within 5 °C.