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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]

• Thermal management using phase change material in finned shells is proposed. • The finned shells can be embedded and separated upon different thermal requests. • PCM in the embedded shells achieved excellent cooling in mild thermal conditions. • As PCM melts to liquid, air convection is introduced through the separated shells. • The design also well protects batteries at low temperatures by PCM solidification. Phase change material (PCM) has recently been regarded as a promising thermal management means for lithium-ion (Li-ion) batteries. However, solid-liquid phase change of many current PCMs occurs in a narrow temperature range, and the cooling performance of their liquid phase is rather poor. To tackle these issues, this article presents a battery thermal management (BTM) design which injects PCM into an aluminum shell around each cell, and machines the shell inner surfaces into a row of straight rectangular fins immersed into the PCM and its outer surfaces into a plain-fin shape exposed in the air. In the mild thermal conditions, the finned shells of two adjacent cells can be embedded and passive PCM cooling is employed. Once the PCM completely melts, the shells will move apart and an airflow will be driven through the gap between them. The BTM design can also protect Li-ion batteries in a freezing environment, by taking advantage of PCM solidification when the finned shells return to their embedded configuration. A series of experiments were conducted to examine its effectiveness on two 50 Ah lithium nickel cobalt manganese oxide (NCM) prismatic batteries, which were discharged at a capacity-rate of 2 C and at room temperatures of T 0 = 25 ∘ C , 40 ∘ C and − 10 ∘ C. It is shown that in the battery discharge at T 0 = 25 ∘ C , PCM in the embedded finned shells effectively reduced the average battery-surface temperature (T ¯) and the maximum temperature difference (Δ T max) by 21 % and 36. 7 % , respectively, compared to bare batteries. At T 0 = 40 ∘ C , this BTM design successfully limited the growth of T ¯ to 9 . 0 ∘ C and led to Δ T max no more than 1 . 5 ∘ C. As to the low-temperature scenario, it maintained the batteries at temperatures above T 0 for 55.2 % longer than those without any BTM protections. Its cooling performance was also compared with that of the conventional liquid-cooling scheme using a bottom serpentine-channel cooling plate. All these results clearly demonstrate that the BTM design in this article can compensate for the deficiencies of conventional PCM-based BTM schemes. Regardless of whether the PCM phase change is available, it has well coped with different thermal management demands of Li-ion batteries. [ABSTRACT FROM AUTHOR]

• Secondary flow was introduced to improve the performance of serpentine channel BTMS. • A grid + elliptical groove serpentine channel plate is proposed in this paper. • Pump power is reduced by 92.6 % and cooling efficiency coefficient is increased by 11.097 times. • Clear the coolant flow trajectory and eddies distribution. • Sensitivity analysis to further clarify the mechanism of cooling. To improve the thermal and economic performance of liquid cooling plate for lithium battery module in the distributed energy storage systems, on the basis of the traditional serpentine liquid cooling plate, the unidirectional secondary channels and grooves are added, combined to three kinds of serpentine cold plates for the battery module. By contrast, the cold plate with both elliptical groove and secondary channel has the best comprehensive performance. Though the thermal performance is slightly reduced, the consumption of pump power is reduced by 92.6 % and the cooling efficiency coefficient is improved by 12.32 times compared to the original cold plate. The cooling temperature targets of the battery pack are that T max less than 40℃ and Δ T avg less than 3 K. In order to achieving the best performance of the cold plate, the influence of the structural parameters and hydrodynamic parameters on the performance index is analyzed, and the sensitivity analysis is carried out which clear the operational mechanism and key design parameters of the cold plate. The results show that different design parameters would generate the change of eddy current which is influential to the cooling performance. Besides, v and D have a significant effect on the performance of the cold plate, followed by d and n, and a has almost no effect on the cooling performance. [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]

• 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]

• 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]

• The quantity of heat generation that induce TR in lithium-ion batteries is lower than in other overheating strategies. • The trigger time of thermal runaway decreases with the increasing current density. • The series tab connection will accelerate the thermal runaway of the adjacent battery. • The parallel tab connection will induce thermal runaway propagation to all parallel-connected batteries. Thermal runaway (TR) of lithium-ion batteries is the main safety obstacle to the further development of electric vehicles (EVs) and electric energy storage systems (EESSs). Understanding the mechanism of TR propagation is one of the primary ways to improve the thermal safety of the lithium-ion battery. In this paper, an electro-thermal model coupled with the lumped thermal runaway model is applied to investigate the TR behaviors induced by tab overheating and the TR propagation in a battery module with different tab connection methods. The electro-thermal model is used to calculate the heat generation at tabs and the cell body during the normal charge/discharge process, and the lumped thermal runaway model is applied to calculate the TR behavior and TR propagation in the battery module. The results exhibit that the TR behavior and TR propagation are influenced by different aspects (C-rates, insulator, and tab connection modes) in the battery module. The largest quantity of heat generation is at 3C-rate, about 0.98 kJ, because of the heat accumulation in the battery. Besides, the quantity of heat generation that induce TR in lithium-ion batteries in this paper is lower than that from the reference, which means that tab overheating is more dangerous than other heating strategies for triggering the thermal runaway of batteries. The trigger time of TR decreases with the increasing C-rate and the tab connection modes mitigate the TR propagation in the battery module at a low C-rate because of the increasing heat dissipation rate, while the TR propagation is accelerated in the battery module at a high C-rate. At low C-rate conditions, the parallel tab connection exhibits a more significant effect on mitigating the TR behavior, and the effect of mitigation decreases with the increasing C-rate. At high C-rate conditions, the series tab connection accelerates the TR propagation to the adjacent battery, while the parallel tab connection speeds up the TR propagation of all the connected batteries. This work is important for understanding the TR propagation mechanism and improving the thermal safety of pouch-type lithium-ion batteries in EVs. [ABSTRACT FROM AUTHOR]

• A comprehensive model based on battery aging effect is developed for MHP-BTMS. • A framework combing deep learning and multi-objective genetic algorithm. • BTMS shows poor cooling capacity due to SEI formation inside the aged battery. • Two optimization strategies are proposed for multi-objective optimization. • The trade-off between battery temperature and performance is achieved. Battery thermal management and electrochemical performance are critical for efficient and safe operation of battery pack. In this research, a multi-physics model considering the battery aging effect is developed for micro heat pipe battery thermal management system (MHP-BTMS). A novel multi-variables global optimization framework combining multi-physics modeling, deep learning and multi-objective optimization algorithms is established for optimizing the structural parameters of MHP-BTMS to improve battery thermal management and electrochemical performance simultaneously. It is found that MHP-BTMS fails to control the temperature of aged battery pack due to the higher heat generation caused by solid electrolyte interphase formation. After 1000 cycles, the maximum temperature and maximum temperature difference were increased by 3.32 K, 2.49 K, 2.04 K and 1.78 K, 1.46 K, 1.26 K, respectively. It is also found that the battery electrochemical performance during the cycling is highly related to battery thermal behaviors. MHP-BTMS with 0.004/s inlet velocity achieved the best performance in preventing SEI formation and battery aging effect, which was lower by 7.01 nm (SEI) and 1.65% (aging), 2.31 nm and 0.58% as compared to 0.002 and 0.003 m/s cases. Besides, MHP-BTMS with optimized inlet velocity, MHP arrangement and cold plate can improve cooling performance and electrochemical performance. Multi-variables global optimization can provide the optimal structure parameters of MHP-BTMS under the different combinations of weighted coefficients and optimization strategies to achieve the trade-off between battery thermal issues and electrochemical performance. In addition, it is demonstrated that the weighted coefficients and optimization strategies in this novel framework can be changed according to the actual needs in engineering applications. [ABSTRACT FROM AUTHOR]

• A model coupling electrochemistry, battery aging and heat transfer is developed. • The comparison between different coolants and nanofluids is performed. • BTMS shows poor cooling capacity due to SEI formation inside the aged battery. • Dispersing nanoparticle into BTMSs can improve thermal behaviors of aged battery. • Nanoparticle shapes have a significant effect on BTMS overall performance. In this research, a novel model considering electrochemistry, battery aging and heat transfer is developed for the design and optimization of battery thermal management system (BTMS) to ensure efficient and durable operation of batteries. The multiphysics behaviors in different working cycles of BTMSs are analyzed and compared. It is found that solid electrolyte interphase (SEI) formation inside the aged battery pack leads to the higher heat generation rate, which is the main reason that BTMSs only provide effective cooling performance in the initial working cycles but fail to control the battery temperature after 1000 cycles. Meanwhile, BTMS with water provides the lowest maximum temperature and temperature difference with the lowest pressure loss, which were 5.14 K, 4.33 K, 3.79 K and 3.94 K, 3.51 K, 3.2 K and 2772.7 Pa, 3980.9 Pa, 5271.8 Pa lower than those of BTMS with EO, were 2.17 K, 1.66 K, 1.37 K and 1.79 K, 1.43 K, 1.19 K and 544.4 Pa, 758.1 Pa, 984.3 Pa lower than those of BTMS with EG. In addition, BTMS with water also showed the best performance in controlling SEI formation and capacity fade, leading the highest average potential. Furthermore, dispersing nanoparticles into BTMSs can further enhance the cooling performance with a higher pressure loss, and BTMS with water-based nanofluid achieves the best performance. Besides, the cooling performance of BTMS increases with increasing volume fraction of nanoparticles, although the pressure loss is also higher. Nanoparticle shapes also have a significant effect on battery thermal behaviors and electrochemical performance. With brick-shaped nanoparticles, BTMS well cools the battery pack and reduces the battery capacity fade. For comparison, BTMS with spherical-shaped nanoparticles achieves the lowest pressure loss with providing favorable thermal manage for battery pack. [ABSTRACT FROM AUTHOR]

• Developed a CFD approach for heating induced thermal runaway incorporating heat dissipation. • Predictions established the critical temperature to trigger TR for the current LIB as 131–132 °C. • Filled important experimental gaps on heat generation of the different decomposition reactions. • Analysis demonstrates effective prevention of TR propagation needs to be implemented prior to TR. Combined numerical and experimental studies have been carried out to investigate thermal runaway (TR) of large format 21700 cylindrical lithium-ion battery (LIB) induced by different thermal abuse. Experiments were firstly conducted with the Extend Volume Accelerating Calorimetry (EV-ARC) using both the heat-wait-seek (HWS) protocol and under isothermal conditions. The kinetic parameters were derived from one of the HWS EV-ARC tests and implemented in the in-house modified computational fluid dynamics (CFD) code OpenFOAM. For the subsequent CFD simulations, the cell was treated as a 3-D block with anisotropic thermal conductivities. The model was verified by the remaining two HWS tests not used in the derivation of the kinetic parameters and validated with newly conducted isothermal EV-ARC tests. Further laboratory tests and model validation were also subsequently conducted using Kanthal wire heaters. The validated model was also used to fill the experimental gaps by predicting the onset temperature for TR in simulated EV-ARC environment, heat generation rate due to different abuse reactions, the influence of heating power and heating arrangement as well as the effect of heat dissipation on TR evolution and the implications for battery thermal management. The present study has identified the TR onset temperature of the considered 21700 LIB to be between 131 and 132 °C. The predicted heat generation rate due to the decompositions of SEI and anode were found to follow similar patterns while that from cathode increase sharply near the maximum cell surface temperature, indicating the possibility of delaying TR onset temperature by optimising the cathode material. The time to maximum cell surface temperature decreases rapidly with the increase of the heating power. [ABSTRACT FROM AUTHOR]

• A manifold immersion cooling scheme for LIB thermal management is developed. • Influence of structural parameters are numerically studied for cooling optimization. • Manifold system can adapt its cooling ability for lateral surfaces of batteries. • This scheme achieves high cooling performance with extremely low pressure drop. Thermal management is very important because lithium-ion batteries generate a lot of heat under high rate charging and discharging. Inspired by the manifold microchannel (MMC) structure for chip cooling, this paper proposes a new manifold immersion (MI) cooling structure used for battery thermal management. The optimization analysis is performed in numerical simulation models. The local convective heat transfer coefficients of the lateral and baffle surfaces are analyzed separately. The results show that unlike the MMC for chip cooling, MI cooling structure's demands high heat transfer in the lateral surface of batteries but not the bottom or baffle surface. Subsequently, the influence of the design parameters on the cooling capacity is analyzed. The results show that the manifold channel length L ch,m and the battery spacing channel width W ch greatly influence the MI cooling performance. Stable wall jet flows are beneficial for MI cooling. It can be formed when L ch,m or W ch is large enough. MI cooling structure requires smaller vortex regions leading to better thermal load and temperature uniformities. The optimized MI cooling structure achieves the maximum temperature of 35.06 °C for a lithium ion battery pack at 5 C discharging, with the bulk temperature non-uniformity θ bulk of 6.66 °C, and the surface temperature non-uniformity θ sur of 3.52 °C. [ABSTRACT FROM AUTHOR]

• A numerical analysis is performed for direct liquid cooling of lithium-ion batteries using different dielectric fluids. • Study and compared the thermal performance of three different dielectric fluids including mineral oil, deionised water, and one engineered fluid. • The temperature rise is limited to below 3 °C for 1c- discharge by using deionised water at all mass flow rates, where oil-based fluids are delivering better performance only at higher mass flow rates of 0.05 kg/s. • The mineral oil and engineered fluids deliver almost an equal thermal performance, however, the latter consumed 76.43% less power at a mass flow rate of 0.05 kg/s. Lithium-ion battery (LIB) cells are responsible for powering most electric vehicles. LIB is still a superior battery available in the market because of its high energy density, specific power, and long cycle life. However, LIB comes with the challenges like thermal management as it is highly sensitive to temperature. Amongst different cooling methods, direct liquid cooling, also known as immersion cooling, can deliver a high cooling rate mainly because of its complete contact with the heat source. The single-phase liquid immersion with dielectric fluids (DELC) offers safety and cooling performance with lower parasitic power consumption and space requirements. This research involves studying and comparing different DELC's for the direct cooling of lithium-ion batteries. A numerical analysis of the 4S1P arrangement of LIB cells with direct cooling is conducted with three different DELC's including deionised water, mineral oil, and an engineered fluid. The transient behaviour of the battery module for various mass flow rates of DELC and at 1C,2C,3C-discharge rates are examined. All DELC maintains an excellent temperature homogeneity within the individual cells and LIB cells. The DELC with higher specific heat and thermal conductivity is suitable for cooling the LIB cells during high discharge conditions. However, all the dielectric fluids studied here effectively limit the temperature rise below 5 °C at 2-C discharging operation when the mass flow rate is increased to 0.05 kg/s. This improvement in thermal performance comes at the expense of extra power consumption. Even though both DELC-2 and DELC -3 delivered almost similar temperature rise values of 6.1, 5.2 °C, respectively during 2C discharging operation, the latter consumed 76.43% less power at a mass flow rate of 0.05 kg/s. For this reason, engineered fluids with lower viscosity values can be preferred over mineral oils. The deionised water is more effective for limiting the temperature rise below 2.2 °C for 3C discharging with the least parasitic power consumption of 0.52 mW at a mass flow rate of 0.05 kg/s. A variable cyclic load matching HWFET-driving cycle has been applied to the battery pack with all three DELCs, and all three fluids limited temperature rise below 1 °C. [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]

• The temperature distribution of a Li-ion battery pack was investigated and the model was verified by independent test. • The square cooling channel can lower the highest temperature more effectively than the circular cooling channel, but results in a slight increase in the temperature dispersion. • As the aspect ratio increases, the temperature dispersion of the battery pack initially decreases and then increases. • In this paper, the most balanced temperature distribution domain is located near the No. 5 single lithium-ion battery. In this article, we studied liquid cooling systems with different channels, carried out simulations of lithium-ion battery pack thermal dissipation, and obtained the thermal distribution. According to the results shown in the study, the number of channels is inversely proportional to the highest temperature and the temperature dispersion. A liquid cooling system with a square channel can achieve a lower highest temperature than that of a liquid cooling section with a circular channel. Simultaneously, the highest temperature is also negatively correlated with the rectangular channel aspect ratio. In addition, as the aspect ratio increases, the temperature dispersion of the battery pack initially decreases and then increases. Furthermore, from the entrance, along the direction of coolant flow, the temperature dispersion of a single lithium-ion battery will initially increase and then gradually decrease, which indicates that the No. 5 lithium-ion battery is the most balanced module in the battery pack. [ABSTRACT FROM AUTHOR]

• Forced air cooling applying metal foam for li-ion battery module is studied. • Employment of metal foam dramatically reduces battery surface temperature. • Metal foam with larger porosity has better temperature uniformity of batteries. • The temperature uniformity is improved by a "T" shape design of aluminium foam. A lithium-ion battery thermal management system using forced air cooling with open-cell aluminium foam was proposed in this paper. The battery module consists of eight pieces of pouch cell and nine pieces of aluminium foam heat sink. The battery module thermal model was developed to analysis its thermal characteristics. Thermal interaction between battery cells in this model was explored. The effects of porosity and pore density of aluminium foam on the heat dissipation performance at different mass flow rates were investigated. The results show that the thermal interaction between battery cells becomes more obvious after using aluminium foam. Metal foam can significantly reduce battery temperature rise compared with the pure air-cooled system, but it will cause huge flow resistance and pressure loss, which will easily lead to uneven temperature distribution on the battery surface. Additionally, decreasing the porosity of aluminium foam decreases the average surface temperature of batteries, but increases temperature difference. To improve temperature uniformity, the cooling air flow direction, the layout of battery module and the shape of aluminium foam were also studied. Our results showed that the case with quarter inlet width and "T" shape aluminium foam exhibited the most excellent performance among all cases. Despite the mentioned defects, applying aluminium foam is still a promising method in battery thermal management system. And this paper provided a theoretical reference for designing aluminium foam thermal management system in batteries. [ABSTRACT FROM AUTHOR]

• A BTM using heat pipe and water spray is studied for Li-ion battery operating at 40 ∘C. • Battery temperature, its difference and rise rate are assessed with the BTM method. • Various spraying conditions are examined to maximize the cooling effects. • This design excels other heat-pipe based BTM methods in fast heat dissipation. Today, performance of lithium-ion battery is still limited by its operating temperature. The upper bound is capped by 50 ∘C. However, this limit is easily surpassed if batteries work at a high room temperature. In this article, sintered copper-powder heat pipe combining with water spray at its condensation section is designed to attack this issue−The former is sandwiched among batteries, removing battery heat by air convection under normal thermal conditions. When battery operation deteriorates at a room temperature beyond 40 ∘C, water spray functions for rapid heat dissipation by droplet evaporation. To assess effectiveness of this battery thermal management (BTM) design, discharge of lithium iron phosphate batteries at two large currents, I d = 12.5 A and 24 A, are performed at 40 ∘C. The cooling performance of the proposed BTM system is examined at different air speeds, air relative humidity, spraying frequencies and duty cycles. It is also compared to other heat-pipe based BTM approaches, and tested in transient cycles. The results demonstrate the proposed BTM system is highly effective. In the case of I d = 24 A , the maximum temperature and maximum temperature difference of the battery surface are dropped by 29.2 ∘C and 8.0 ∘C in comparison to those without BTM aids. It well protects lithium-ion battery operating at a large discharging current in an adverse thermal environment. [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]

• Novel fin structures are proposed for heat transfer enhancement of PCM. • Visualization of the melting process of PCM within the BTMS is presented. • Thermal management performance of PCM-Fin based BTMS is evaluated. Phase change materials (PCM) based battery thermal management system (BTMS) usually suffers from the low thermal conductivity of PCM. In this paper, novel fin structures which consist of longitudinal fins and cylindrical rings are proposed for heat transfer enhancement. Experiments are firstly designed to compare the thermal performance of different BTMSs. Results demonstrate that the PCM-Fin system shows superior performance over the pure battery system and the PCM system. Numerical simulations are also conducted based on the model validation with the experimental data to reveal the underlying mechanisms. It is found that fin structures not only increase the heat transfer area but also introduce a thermal conductive network within the PCM, which contributes positively to the improvement of thermal performance of the battery. Moreover, the effects of the position of rings, the number of rings and fins, and the heat generation rate on the thermal management performance are evaluated. Results show that the optimal numbers for rings and fins are 1 and 8, respectively, and the recommended dimensionless distance between ring and battery is 0.2. It is also found that the PCM-Fin system can control the temperature rise of the battery even under the heat generation rate of 20 W. [ABSTRACT FROM AUTHOR]