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Composite phase change materials commonly exhibit drawbacks, such as low thermal conductivity, flammability, and potential leakage. This study focuses on the development of a novel flame-retardant phase change material (RPCM). The material's characteristics and its application in the thermal management of lithium-ion batteries are investigated. Polyethylene glycol (PEG) serves as the medium for phase change; expanded graphite (EG) and multi-walled carbon nanotubes (MWCNT) are incorporated. Moreover, an intumescent flame retardant (IFR) system based on ammonium polyphosphate (APP) is constructed, aided by the inclusion of bio-based flame-retardant chitosan (CS) and barium phytate (PA-Ba), which can improve the flame retardancy of the material. Experimental results demonstrate that the RPCM, containing 15% IFR content, exhibits outstanding flame retardancy, achieving a V-0 flame retardant rating in vertical combustion tests. Moreover, the material exhibits excellent thermomechanical properties and thermal stability. Notably, the material's thermal conductivity is 558% higher than that of pure PEG. After 2C and 3C high-rate discharge cycles, the highest temperature reached by the battery module cooled with RPCM is 18.71 °C lower than that of natural air-cooling; the material significantly reduces the temperature difference within the module by 62.7%, which achieves efficient and safe thermal management. [ABSTRACT FROM AUTHOR]

Summary: The widespread use of lithium‐ion battery (LIB) urgently needs a thermal management system with excellent performance to manage it. Phase change material (PCM) has been adapted for thermal management of LIB because it can absorb a mass of energy without additional power. In this research, the thermal conductivity of PCM is improved, and its cooling effect is detected. The addition of hybrid thermal conductivity filler is beneficial to its uniform dispersion and improvement of aggregation phenomenon on the surface of materials. The results show that the PCM with hybrid filler has better thermal conductivity, which is increased by 264%. In different proportions of composite materials, the composite phase change material with 1% few‐layer graphene and 2% graphite nanoplatelet can play a better cooling effect in LIB module thermal management, and it respectively decreases the maximal temperature of the battery module by 7.17°C, 10.52°C, and 16.33°C at 1C, 2C, and 3C conditions, and the maximal temperature difference does not exceed the safety range of 5°C. [ABSTRACT FROM AUTHOR]

• There exists domino phenomenon in the process of thermal failure propagation. • Failure propagation speed has a square index decline relationship with battery gap. • Failure propagation speed grows linearly with the increasing module SOC. • Once thermal failure appears, traditional PCM will deteriorate the failure propagation behavior. A series of thermal failure researches were conducted to explore the effects of parameters on the failure propagation behavior within battery modules, including the gap between batteries, the state of charge (SOC) and traditional phase change material (PCM). Based on the results, obvious domino phenomena were revealed during the process of thermal failure propagation, where the thermal failure of module (3 × 3) could be divided into six phases. It was illustrated that increasing battery gap could effectively prevent thermal failure propagation by postponing each phase of failure and decreasing the propagation speed. The propagation speed agreed well with the square of battery gap, and it grew linearly with the increasing module SOC. Due to the low conductivity and diffusivity of traditional PCM, it was found that the failure propagation behavior of the module wrapped with PCM would be severer. [ABSTRACT FROM AUTHOR]

• A dual-functional battery module was designed using aerogel felt coupled with PCM. • Thermal behaviors of the battery modules with PCM and aerogel were studied. • Evaluation of battery modules were conducted from two aspects simultaneously. In view of the flammability of phase change materials (PCMs), a safer structure design for thermal insulation protection is crucial in a PCM-based battery thermal management system. In this work, a series of experiments is performed on battery modules with and without PCM and/or aerogel to investigate their heat dissipation capability and thermal insulation capability in both thermal runaway tests and cycling tests. The results demonstrate that the PCM added with expandable graphite considerably inhibits the combustion flame and lowers the peak temperature of battery modules; however, it accelerates the thermal runaway propagation speed. In comparison, the aerogel felt exhibits excellent performance in delaying battery thermal runaway. Based on the foregoing, an optimized dual-functional battery module is proposed. The module combines the strengths of the PCM and aerogel, and its thermal behaviors are explored via proper analysis with experimental verification. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) are frequently employed in electric vehicles for their high energy density and lengthy cycle life. However, efficient battery thermal management system (BTMS) is critical for ensuring the reliability, safety, and service life, as temperature greatly impacts their performance. The potential risks of battery fire and explosion under excessive temperatures necessitate the development of effective emergency management and technologies to maintain safe operation. Phase change material (PCM) which offers distinct advantages, including reasonable cost, low energy consumption, and excellent temperature uniformity, making it an attractive candidate for thermal management, has emerged as a promising solution for BTMS. This comprehensive review aims to shed light on PCM-based BTMS, and it is found that carbon-based additives are better than metal-based additives concerning density and stability, and the addition of polymers and nanomaterials can improve the structural stability and mechanical properties. However, the flammability of PCM exacerbates the fire risk and hazard of battery thermal runaway (TR), and this review also has a particular emphasis on enhancing PCM's flame retardant properties and exploring its applications in BTMS. Flame-retardant PCM can ensure the safety of LIB utilization process and has a promising application in suppressing TR. Moreover, there exists a prominent challenge of the comprehensive need for optimization of heat dissipation optimization and improvement of TR propagation suppression ability of PCM-based BTMS. Finally, the challenges and outlooks focus on the future PCM-based BTMS are disclosed, in the hope of bring new insights to building a synergistic BTMS. Graphic abstract [Display omitted] • Heat dissipation optimization and thermal runaway propagation suppression coordination. • Highly thermally conductive, non-leakage deformable, flame retardant PCM compared. • Feasibility to utilize PCM to prevent the propagation of thermal runaway proposed. • Insights into research gap and further development and of PCM provided. [ABSTRACT FROM AUTHOR]

In advanced battery thermal management systems for electric vehicles, liquid cooling (LC) is typically coupled with a phase-change material (PCM) cooling for secondary heat dissipation. However, a continuous LC consumes a considerable amount of energy without considering the operating conditions. In this study, the thermal behaviors of tubular PCMs were examined under different liquid temperatures (25, 45, and 65 °C) to simulate the complex operating conditions of battery modules. In addition, a thermal management module coupling the PCM and copper pipe (CP) with LC was assembled to enhance the secondary heat dissipation of PCM cooling, particularly in a high-temperature environment. The experimental results confirmed the superior cooling effect of the PCM–CP module, even at high temperatures. Moreover, a dynamic LC (DLC) mode was proposed to reduce the energy consumption caused by LC, where LC operates intermittently. The effects of the LC activation time on the cooling behavior were explored. A coefficient illustrating the energy efficiency ratio (EER) was defined to evaluate the cooling performance and energy consumption of the two DLC modes with varying working times. The results proved that DLC-2 performed better than DLC-1 with E E R ¯ j values of 0.35 and 0.24, respectively. These results are expected to provide insights into the development of advanced energy-saving thermal management systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Majority existing organic composite phase change materials (CPCMs) are flammable that result in thermal hazards such as fire and explosions in battery modules. Furthermore, the performance of PCM-based battery modules in extreme conditions like thermal runaway has not been studied adequately. In this study, a tubular CPCM-cell structure is designed using physically flame-retardant-modified CPCMs, and a series of experiments on the CPCMs with/without real cells is conducted with calorimeter tests and SEM analysis on morphology structure. First, the calorimeter tests and comparison on the heat release rate (HRR) are conducted on the CPCMs with and without flame retardant additives. Results show that the addition of Al(OH) 3 reduced the HRR from 242.5 to 204.4 kW/m2 with 15 wt% additives. Besides, the analysis of the mitigating performances of structure-enhanced tubular module and traditional cuboid module with real batteries is conducted. A factor of safety (FOS) parameter is defined to evaluate the safety degree of thermal runaway domino with energy density. The FOS of blank, CPCM–0 C , and CPCM–15 C modules are 0, 3.59, and 16.67, respectively, while that of CPCM-15 T reaches 21.01, indicating a significant improvement on mitigating effects by structure enhancement compared to adding flame retardant additives. This study brings novelty in the design of PCM-based battery modules, particularly from the thermal safety prospect. • An optimized tubular module using modified CPCM is designed to reduce hazard risk. • Bottleneck issue is solved by structure enhancement without reducing energy density. • Effect of flame retardant additives on thermal hazards is tested with/without cells. • Mitigation of tubular unit with air-flow-channel on heat propagation is tested. • Evaluation of battery modules are conducted from two aspects simultaneously. [ABSTRACT FROM AUTHOR]

• Branch-structured fins are designed for high temperature environment. • Thermal behaviors of modules under different ambient temperatures are compared. • How PCT influences the performance of PCM is investigated under high temperature. Battery modules with phase change material (PCM) cooling inevitably suffer from heat-storage saturation and poor secondary-heat dissipation, especially in high-temperature environments or hot regions. To optimize thermal management, this study firstly explores the thermal behaviors of PCMs with different phase change temperatures (PCTs) in a high-temperature environment. The experimental results show that a PCM with a PCT of 46 °C offers the best cooling effect at a high ambient temperature of 40 °C in this study. For example, the maximum temperature of a cell without PCM reaches 53.3 °C, whereas that of the cell with PCMs having PCTs 40, 46, and 55 °C, are 59.2, 51.6, and 57.5 °C, respectively, during the dynamic cycling process. Nevertheless, the application of above PCM is still unsatisfying because the maximum temperature of the battery in the PCM module exhibits obvious increasing trend with cycles in 40 °C environment. On this basis, several novel fins with multiple heat-flow channels (of V, Y and X shapes) are designed and introduced into the PCM module to enhance the secondary heat dissipation capability. These fins with innovative branch structures deliver excellent performance in alleviating the battery temperature than the traditional rectangular fins, which can be attributed to the ability of the branch structures to increase the heat transfer area by adding heat transfer channels. The results of this work show that the X-shape delivers the best performance in a high-temperature environment of 40 °C by maintaining the maximum temperature of the cell below 47 °C. [ABSTRACT FROM AUTHOR]

• New PCM filling methods with gradient thickness or conductivity were proposed. • PCM thickness optimization was studied via experiments and theoretical calculation. • A parameter of δ ct has been proposed for the PCM application in cylindrical batteries. • How the laying-aside time influenced cooling performance of PCM was studied. Phase change material (PCM) cooling, as an excellent option for ensuring safety via balancing heat distribution, has been widely used in the thermal management of lithium-ion battery. In this work, a simple PCM cooling structure has been designed. Then we systematically investigate its cooling behavior and the influence of several detailed factors on the performance, including the thickness and phase change temperature (PCT) of the PCM, as well as the laying-aside time during dynamic cycling. The experimental results show that a PCM module with a thickness of ∼10 mm presents the optimal cooling performance, consistent with the theoretical calculation, but the lower heat dissipation capability at the bottom of the battery should be taken into account when designing the PCM module. In addition, increasing the laying-aside time is also beneficial to enhancing the cooling efficiency, whereas the selection of the PCT is variable based on different specific applications and comprehensive requirements, particularly those targeting guaranteeing a higher capacity of the batteries. [ABSTRACT FROM AUTHOR]