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• The dynamics of the thermal runaway front in large-scale Li-ion batteries are deduced theoretically. • The velocity of the front yields a 1/2 power relationship between the thermal conductivity and reaction rate. • Freezing thermal runaway front is possible in theory and validated by experiments. • Heat dissipation enlarged by heat transfer time delay is critical for the freeze. Large-scale lithium-ion batteries are favored in electric vehicles and energy storage stations; for instance, BYD blade batteries and CATL Kirin batteries are popular. A tiny defect will trigger thermal runaway from a local point towards the other parts of the battery, and the boundary between the failure region and the intact region is called the "thermal runaway front," of which the dynamics are still unclear. Herein, this paper deduces two formulas for the moving speed (v TR) of the thermal runaway front by applying the principles of energy conservation (Formula I) and flame front (Formula II); formulas for the thermal runaway front velocity (v TR) are derived. The velocity v TR conforms to the 1/2 power of the heat conductivity and reaction rate in both formulas. Data regression for the experimental data demonstrated that the overall estimation error was 10 % using Formula I and 25 % using Formula II. As the zero velocity value indicates the termination of thermal runaway propagation, further derivations reveal that forced cooling can suppress thermal runaway as long as the heat dissipation power is higher than the heat generation power. Sufficient heat dissipation time is achieved by the time delay of heat transfer in the long run of thermal runaway propagation. The formula for the dynamics of thermal runaway propagation universally applies to various large-scale lithium-ion batteries, assisting the safe design of high-energy batteries and providing new insights into suppressing battery thermal runaway by the heat transfer delay effect. [ABSTRACT FROM AUTHOR]

• The presence of mechanical vibrations has been found to alter the optimal number of fins in the PCM-fin structure thermal management system. • Amplitude and frequency of mechanical vibration notably impact the thermal performance of the PCM-fin structure thermal management system. • The research findings emphasize the significance of considering mechanical vibrations in the design of the PCM-fin structure thermal management system, contributing to the development of lightweighting strategies in electric vehicle battery thermal management. The PCM-fin structure battery thermal management system (PCM-fin structure BTMS) has garnered significant attention due to its exceptional thermal performance. However, existing research has overlooked the presence of mechanical vibration that is inevitable in the operational environment of electric vehicle BTMS. This study aims to address this knowledge gap by comprehensively analyzing the effect of mechanical vibration on the thermal performance of the BTMS under high-temperature and high-rate discharge condition. Four novel findings are introduced for the first time: Firstly, mechanical vibration can significantly enhance the thermal performance of the BTMS, and the enhancement effect is more pronounced compared to the PCM-based BTMS without fins. Secondly, mechanical vibration also affects the ideal fin quantity for the BTMS. Under no vibration condition, the ideal quantity of fins is 10, while under mechanical vibration condition of 30 mm amplitude and 20 Hz frequency, the ideal fin quantity is 8. Thirdly, the thermal performance of the BTMS can be improved by increasing the vibration amplitude. Nevertheless, once a certain high value is reached, further increasing the vibration amplitude has a negligible effect on the enhancement of thermal performance. Lastly, even under low vibration frequency of 10 Hz, the BTMS can still perform well. However, as the vibration frequency increases, the thermal performance of the BTMS becomes progressively less sensitive to changes in vibration frequency. This work can provide guidance for the design and practical application of PCM-fin structure BTMS. [ABSTRACT FROM AUTHOR]

• A hybrid heat exchanger which enables sole air or liquid cooling as well their combination simultaneously is proposed. • The performance of the proposed heat exchanger is documented experimentally. • Hybrid heat exchanger keeps the battery cell temperature below 30°C for continuous 3C discharge rate. • Hybrid cooling increases temperature uniformity and the maximum temperature difference is 2.7°C. • The applicability of the proposed heat exchanger for electronic cooling is validated experimentally with resistance heaters. The temperature of cells varies greatly during dis/charge while their performance and lifetime are greatly affected by this fluctuation. Elevated temperatures may yield battery fire due to thermal runaway as well they accelerate ageing and capacity fade of cells. Thermal management systems are a necessity for electric vehicles to extend the lifetime of battery cells and eliminate any fire risks, especially for fast dis/charging applications. Here, we document a hybrid cold plate with a working fluid(s) of sole air or liquid as well as both of them. Hybridization of air and liquid cooling promises to minimize energy consumption requirements during a charge/discharge cycle by combining the benefits of both thermal management strategies if energy management is controlled accordingly. The temperature of each cell can be kept below 30°C with the proposed hybrid cooling heat exchanger, and the temperature difference between the cells is reduced by 30 % relative to liquid cooling. The maximum temperatures are decreased by 18 % and 3 % in hybrid cooling when compared to air and water cooling, respectively. Furthermore, a step function combining various discharge rates (1C and 3C) was employed in experiments to mimic a realistic situation, i.e. variable C-rate rather than constant. The results show that the temperature of the battery cells can be kept below 30°C with air cooling for variable discharge rate and the effect of contact resistance should not be overlooked for liquid cooling. Furthermore, the possible use of the proposed hybrid cold plates is surveyed in the cooling of electronic devices which produce more and continuous heat than cells. Therefore, three resistance heaters with a capacity of 50W are used in experiments as well. The results show that the proposed cold plates could be used in both electronics cooling and battery thermal management with a control algorithm to switch between sole working fluid and combination modes which could be developed based on the results of this paper. [ABSTRACT FROM AUTHOR]

• An integrated system capable of cooling battery and cab is proposed. • Phase change cooling and liquid cooling are used to inhibit thermal runaway. • The parameters affecting the cooling performance of system are discussed. • A reasonable and economical parameter combination is determined. Nowadays, thermal runaway of lithium-ion battery is widely considered to be a serious hazard to the safety of electric vehicles. In order to effectively prevent thermal runaway, an integrated thermal management solution is proposed. Firstly, a few models of battery, air conditioning system, phase change cooling and liquid cooling are established, respectively. The temperature and heat are used to coupling each model. Then the effectiveness of models is validated by experiment. Finally, the cooling performances of this system are discussed. Under the circumstance of thermal runaway, the battery thermal management system can inhibit thermal runaway, and the battery temperature is reduced from 1208.17 to 304.82 K. In addition, the influences of the convective heat transfer coefficient and flow channel number on the cooling effect are also studied, and in order to ensure that the batteries have an appropriate temperature and reduce energy consumption, their values should be 20 W∙m−2∙K−1 and 5, respectively. When the vehicle is normally driving, the influences of different driving speeds, pump speeds and compressor speeds on the battery temperature are discussed, meanwhile, combined with the cooling effect of air conditioning, a reasonable and economic scheme is determined, that is, the pump speed is 2250 r∙min−1 and the compressor speed is 2500 r∙min−1, and under this scheme, the maximum battery temperature is only 35 °C, and the cab temperature can be reduced to the target temperature within 112 s. [Display omitted] [ABSTRACT FROM AUTHOR]

• A thermal model of full-size-scale real EV battery packs is developed. • Thermal management of the battery pack cooled by channeled liquid flow is studied. • The thermal management system is fine-tuned by re-managing the flow distribution. • Parametric studies on discharge/charge C-rate and coolant flow rate are conducted. A numerical study with the aim of upgrading thermal performances of battery pack of electric vehicles is conducted for a full-size-scale battery pack with 22 modules (totally 5664 18650-type lithium-ion batteries contained) cooled by a channeled liquid flow. The heat generation of the battery is modeled based on experimental measurements. Experiments with one typical module (consisting of 180 batteries) of the pack, charging and discharging at different C-rate (2C, 1C or 0.5C) at a specified liquid flow rate, are first carried out. The experimental results in what concerns maximum temperature in the battery module is in good agreement with the corresponding numerical predictions, demonstrating the reliability/fidelity and consequent accuracy of the developed model. The battery thermal management system is then fine-tuned to re-manage the flow distribution among modules for the sake of improving the thermal uniformity across the pack. The effect on the pack thermal performance of different charge/discharge C-rates and flow rates are extensively investigated, and the results indicate that the pack is thermally well-performed during 1C/0.5C discharge/charge operation with a fluid flow rate of 18 L/min; increasing the discharge/charge C-rate worsens the battery pack's thermal characteristics and increasing the coolant flow rate makes the battery pack perform better. [ABSTRACT FROM AUTHOR]

• Thermal runaway assessed by means of Natural Luminosity and Schlieren. • LCO, NMC and LFP cathodes compared under reactive and inert conditions. • Inert atmosphere inhibits the mixture ignition outside the battery cell. • Similar venting penetration and speed for all the chemistries assessed. • LFP chemistry depicts the safer operation amongst the chemistries. Thermal runaway is one of the main concerns of battery electric vehicles due to the hazard level that represents for the user and the surroundings. Several works studied different type of abuse in lithium-ion cells and packs, but the understanding is still insufficient in terms of the combustion process. In this study, three different lithium-ion cell chemistries (LCO, NMC and LFP) are studied in two environmental conditions with different oxygen content (0 and 21%) in a continuous flow vessel to understand if the use of inert atmosphere may be a pathway to avoid thermal runaway. In addition, detailed optical research is conducted together with temperature sensing to understand the venting through the vent cap before the thermal runaway. The combustion is recorded with a high-speed camera (6000 fps) while the venting is visualized through a Schlieren technique with another high-speed camera (12,000 fps). The thermodynamic results show that the venting process can be detected by a cell surface temperature decrease of around 5 °C, while the thermal runaway is seen as a battery self-heating (cell temperature higher than the ambient) and a suddenly increase of temperature until 700 °C in the surface of the cell. The optical access to the combustion chamber allows to observe with detail the venting of liquid electrolyte amongst the gases generated by the thermal abuse. In addition, the combustion records show that with inert atmosphere the combustion it is not initiated, and the process is restricted to smoke ejection. By contrast, the case of air (21% O 2) resulted in combustion outside the battery cell with high increase of the air temperature. In terms of battery chemistry, the Lithium, Ferrum, Phosphate (LFP) shows the highest safety time and lowest chamber temperatures. LCO and Nickel Manganese Cobalt (NMC) had similar behaviour in terms of safety time and temperature behaviour, but Lithium Cobalt Oxygen (LCO) shows more variation with respect to the atmosphere (reactive and inert) than NMC. [ABSTRACT FROM AUTHOR]

• Battery thermal management based on the liquid cooling with impregnated composite PCM is investigated. • Differential melting in CPCM leads to large battery temperature difference at module level. • Double-sided cooling reduced both maximum battery temperature and temperature difference and prolonged the working time as against single-sided cooling. • Better agreement with experiments is found for the present numerical analysis by incorporating the interfacial gaps. Thermal management of lithium-ion batteries has been a crucial task in the development of battery based electric vehicles. In this paper, the thermal performances of the composite phase change material (CPCM) made of paraffin and high porosity copper foam for the battery modules are presented by means of experiments and numerical simulation. The test battery module consisting of 3 × 5 cylindrical batteries were immersed in the paraffin/copper foam composite enclosed in the aluminum housing. Experiments were conducted for external single-sided liquid cooling and double-sided liquid cooling, in comparison with the natural convection case. The thermal characteristics of the battery module under natural convection conditions were first examined. In order to further reduce the temperature rise, the liquid cooling on the single side and double sides of the battery housing was implemented and tested. It is found that the double-sided liquid cooling has the better temperature control performance with the lowest battery temperature within acceptable temperature difference. Moreover, a two-dimensional numerical model for the battery module with CPCM was also established by taking into account the interfacial gaps. The numerical simulation results were in better agreement with the experimental observations, as against the conventional one-temperature model. Image, graphical abstract [ABSTRACT FROM AUTHOR]