Yin Chen

Thermal runaway of lithium-ion batteries is a critical issue restricting their safe application. Efficient thermal management and flame-retardant protection are essential for improving the safety of battery systems. In this study, polyethylene glycol (PEG) was used as the phase change energy storage matrix, and expanded graphite (EG), flake copper, and MXene nanosheets were introduced to construct a three-dimensional thermally conductive enhancement network. Zinc hydroxystannate (ZHS) and ammonium polyphosphate (APP) were added as synergistic flame retardants to prepare thermally conductive enhanced composite phase change materials with efficient heat dissipation, leakage prevention, and flame retardancy. The structure and thermal properties of the materials were systematically characterized by XRD, SEM, DSC, TGA, and the steady-state heat flow method, with emphasis on evaluating their thermal safety regulation performance in lithium-ion battery cells and modules. The results show that the composite PCMs exhibit no leakage at 60 °C and 80 °C, and the thermal conductivity reaches 3.81 W/(m·K) at a metal filler mass fraction of 20%. In module tests at a 3C discharge rate, the CM2 material reduced the peak temperature by 25.2 °C compared with natural cooling and maintained the maximum temperature difference between cells within the safety threshold. In addition, the inherent flame retardancy of the material helps delay thermal runaway propagation, providing dual safety protection through heat dissipation and fire resistance for battery systems. This study offers a new approach for the design of high-safety thermal management materials for lithium-ion batteries.

With the continuous increase in energy density of lithium-ion batteries, thermal safety has become a critical constraint on their further development. To address the limitations of mechanical brittleness and high-temperature infrared transparency in SiO₂ aerogels for thermal safety applications in lithium-ion batteries, this study developed a novel nanofiber aerogel composite by incorporating chitosan and MXene into a SiO₂ aerogel matrix. This material retains the characteristics of being ultra-lightweight and highly elastic while significantly enhancing mechanical strength and high-temperature insulation performance. It exhibits a thermal conductivity of 0.034 W/m K at room temperature and 0.053 W/m K at 400 °C, alongside a compressive strength of 1.172 MPa. In battery thermal runaway propagation tests, the aerogel successfully prevented propagation in serially connected and electrically isolated systems, and delayed thermal runaway propagation by 35 s in a parallel system, demonstrating excellent thermal runaway suppression capability. This work provides an effective material solution for the practical application of high-performance thermal insulation aerogels in battery safety protection and offers inspiration for developing new insulating ceramic aerogels.

Battery thermal runaway (TR) is usually accompanied by a large amount of heat release, as well as a jet of flame. This not only causes harm to the surrounding environment but even exacerbates thermal runaway propagation (TRP). At this stage, many types of materials are used to suppress TRP, and people tend to focus on improving one characteristic of the material while ignoring other properties of the material. This may leave potential pitfalls for TRP suppression, suggesting the need to study multiple properties of multiple materials. In order to better weigh the advantages and disadvantages of different types of materials when suppressing TRP, we compared three typical materials for suppressing TRP behavior in lithium-ion batteries (LIBs). These materials are phase change materials (PCM), ceramic fibers, and glass fibers. They are all available in two different thicknesses, 2 mm and 3 mm. The experiments started with a comparative analysis of the TR experimental phenomena in the presence of the different materials. Then, the temperature and mass loss of the battery module during TR were analyzed separately and comparatively. The 3 mm glass fiber showed the best inhibition effect, which extended the TR interval between cells 1 and 2 to 894 s and successfully inhibited the TR of cell 3. Compared with the blank group, the total mass loss decreased from 194.3 g to 182.2 g, which is a 6.2% reduction. Subsequently, we comprehensively analyzed the performance of the three materials in suppressing TRP by combining their suppressing mechanisms. The experimental results show that glass fiber has the best effect in suppressing TRP due to its excellent thermal insulation and mechanical properties. This study may provide new insights into how to trade-off material properties for TRP suppression in the future.

Pure phase change materials (PCMs) have drawbacks such as low thermal conductivity and poor physical properties like flammability, which limit their further application in battery thermal management systems. This paper introduces an innovative flame-retardant composite phase change material (CPCM) made from paraffin, expanded graphite, chitosan (CS), ammonium polyphosphate (APP), and aluminum hypophosphite (AHP). The physicochemical properties and flame-retardant performance of CPCMs with five different flame-retardant ratios of 9%, 12%, 15%, 18%, and 21% are studied, and their application effects in battery thermal safety are revealed. The results show that the combination of flame retardants CS, APP, and AHP exhibits effective synergistic effects, and the prepared CPCM exhibits good flame-retardant properties and thermal management effects. The CPCM exhibits outstanding thermal management performance when the flame-retardant content is 12%. At a maximum discharge rate of 3C, compared to natural air-cooling conditions, the maximum battery temperature and temperature difference are controlled within the safe range of 41 °C and below 5 °C, respectively. The CPCM can play an important role in the thermal safety of lithium-ion batteries.

This study investigates the effectiveness of different wrapping materials, namely aerogel felt, thermal conductive gel, and two phase change materials (PCMs) in mitigating thermal runaway in lithium-ion batteries. The experimental results reveal that all the materials tested delay the onset of thermal runaway and safety valve rupture compared to unwrapped batteries. Specifically, aerogel felt and thermal conductive gel offer substantial thermal runaway inhibition, delaying the safety valve rupture time by 97 and 99 s, respectively. PCM-1 demonstrates a delay in safety valve rupture but has a limited impact on the onset of thermal runaway. Among all materials, thermal conductive gel shows the most significant impact, postponing both safety valve rupture and thermal runaway onset. In contrast, the PCMs exhibit relatively weaker effects. Furthermore, batteries wrapped in aerogel felt produce the highest CO concentration during thermal runaway, reaching 3,658 ppm. The maximum mass loss rate of the batteries varies with the wrapping material, ranging from 20.1 to 68.5 g/s, with the unwrapped batteries exhibiting the highest loss rate. Overall, the results suggest that thermal conductive gels and phase change materials improve the safety and emergency response of lithium-ion batteries under extreme conditions, with the thermal conductive gel showing the most promising results in delaying both safety valve rupture and thermal runaway.

Although phase change materials (PCMs) exhibit effective performance in the thermal management of lithium-ion batteries (LIBs), their development is limited by low thermal conductivity and susceptibility to leakage during the solid–liquid phase transition. To address these challenges and enhance thermal management capabilities, this study introduces a novel composite phase change material (CPCM) synthesized by physically mixing paraffin (PA), expanded graphite (EG), and bacterial cellulose (BC). The thermal performance of CPCMs with varying BC proportions is evaluated, and their impact on temperature control in battery thermal management systems (BTMS) is assessed. The results show that the addition of EG and BC significantly improves the thermal conductivity of the CPCM, reaching a value of 1.39 W·m⁻¹·K⁻¹. This also enhances the uniformity of temperature distribution within the battery module and reduces CPCM leakage. By comparing temperature variations within the battery module under different operating conditions, it was found that the intricate network structure of the CPCM promotes uniform temperature distribution, effectively mitigating temperature rise. Consequently, the maximum temperature and maximum temperature difference within the battery module were maintained below 47 °C and 4 °C, respectively. Compared to a system without phase change material at a 3C discharge rate, the maximum cell temperature, maximum module temperature, and maximum temperature difference were reduced by 32.38%, 26.92%, and 34.94%, respectively. These findings provide valuable insights for the design and optimization of BTMS.

Lithium-ion batteries (LIBs) are extensively utilized in electric vehicles (EVs), energy storage systems, and related fields due to their superior performance and high energy density. However, battery-related incidents, particularly fires, are increasingly common. This paper aims to first summarize the flame behavior of LIBs and then thoroughly examine the factors influencing this behavior. Based on these factors, methods for suppressing LIB flames are identified. The factors affecting flame behavior are categorized into two groups: internal and external. The paper then reviews the flame behavior within battery modules, particularly in confined spaces, from both experimental and simulation perspectives. Furthermore, methods for suppressing battery flames are classified into active and passive techniques, allowing for a more comprehensive analysis of their effectiveness. The paper concludes with a summary and outlook, offering new insights for future research and contributing to the development of safer and more efficient battery systems.