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• Three layout schemes of liquid cooling plate were discussed. • The heat dissipation in a liquid cooling system was considered under various factors. • The heat dissipation scheme for imported coolant cooling of variable temperature was proposed. • The solution reduces the temperature difference of the battery pack by 36.09 %. To promote energy conservation and emission reduction, the electric vehicles (EVs) are developing rapidly. An effective battery thermal management system (BTMS) can extend the service life of batteries and avoid thermal runaway. In this study, a liquid-cooling management system of a Li-ion battery (LIB) pack (Ni-Co-Mn, NCM) is established by CFD simulation. The effects of liquid-cooling plate connections, coolant inlet temperature, and ambient temperature on thermal performance of battery pack are studied under different layouts of the liquid-cooling plate. Then, A new heat dissipation scheme, variable temperature cooling of the inlet coolant, is proposed. Results indicate that connecting two sets of liquid coolant plates in a 3-series, 1-parallel configuration can effectively reduce the maximum temperature of the battery pack from 48.73 ℃ to 30.75 ℃, while controlling the maximum temperature difference to 3.98 ℃ at the end of discharge. Simultaneously, the proposed cooling scheme reduces the maximum temperature difference within the battery pack by 36.09 % at the beginning of the discharge period. This study provides a valuable reference into advancing BTMSs of battery pack-level for EVs. [ABSTRACT FROM AUTHOR]

• 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]

• Pulsating heat pipes with good thermal performance were designed for battery module heating management at low–temperatures. • The low–temperatures thermal management system for the battery module with pulsating heat pipes was proposed. • The thermal and electrical performance of the battery module with low–temperatures thermal management system was investigated. To effectively solve the problem that the capacity of lithium power batteries decreases significantly and is prone to irreversible damage under low–temperature charge and discharge scenarios, which seriously affects the driving range, cycle life and service safety of electric vehicles (EVs). In this paper, a low–temperatures thermal management system of pulsating heat pipes with ethanol as the base fluids and TiO 2 nanofluids as the working fluids (TiO 2 –CLPHP TMS) is constructed. On this basis, the thermal performance analysis of TiO 2 nanofluids pulsating heat pipes (TiO 2 –CLPHP) is carried out under different volume concentrations (0 %, 0.5 %, 1.0 %, 2.0 %, 4.0 %, and 8.0 %) and different fluid filling rates (30 %, 50 %, 70 %, and 90 %) in a low–temperature environment. Aiming at the low–temperatures charging scenario of the battery module, the performance test of the TiO 2 –CLPHP TMS for the battery module heating management is carried out under different low–temperature environments (−5 °C, −15 °C, and −25 °C) and different charging rates (0.3C, 0.5C, 0.7C, and 1.0C). The experimental results show that TiO 2 –CLPHP with fluids filling rate of 50.00 % and TiO 2 nanofluids concentration of 2.00 % has good performance in start–up and heat transfer, and can optimize the thermal performance of TiO 2 –CLPHP. Meanwhile, TiO 2 –CLPHP TMS can ensure that the battery module has superior thermal performance. the battery module can be charged within the allowed temperature range (greater than 0 °C). under different low temperature environments (−5 °C, −15 °C, and −25 °C), the temperature of the battery module is basically maintained at 3.30 °C, 8.00 °C and 16.00 °C. The temperature difference between different areas of the battery module is within the allowable temperature difference range of 5 °C, which reduces the adverse effects of the battery aging caused by low–temperature charging and uneven temperature. Moreover, the battery module also has good electrical performance, the battery module voltage is in a low–level range in the early and middle stages of charging. During the complete charging process, the low–temperature charging capacity of the battery module has almost no attenuation, and the charging capacity ratio is as high as 95.92 %. Compared with the pure battery module, the charging capacity and charging efficiency of the battery module with the TiO 2 -CLPHP TMS has been improved to different degrees. Especially at −25 °C, the maximum charging capacity and charging efficiency can be increased to 24.51 %, and the minimum can be increased to 13.17 %. which ensures the efficient charging of the battery module. This proves that the designed TiO 2 –CLPHP TMS is feasible and effective for battery module heating management. [ABSTRACT FROM AUTHOR]

• Stimulus strategy with auxiliary heat load is valid for start-up promotion and heat transfer enhancement of PHP. • High interference temperature, weak auxiliary heat load and long period are optimal for stimulus strategy. • Phase-change mechanism and hysteresis of working medium in PHP is the main reason for validity of stimuls. Stimulus strategy is proposed to enhance the heat dissipation performance of Pulsating Heat Pipe (PHP) at low heat load for local hot spot regression in Battery Thermal Management (BTM). An auxiliary heat load is applied to stimulate the start-up of PHP. The performances of PHP with and without stimulus are compared and the properties of PHP after stimulus are discussed. It is concluded that the application of auxiliary heat load is able to stimulate the start-up of PHP in experiments. The strategy is mainly based on the phase-change mechanism as well as the hysteresis of working medium. Thermal resistance and the evaporator temperature are significantly reduced, if PHP starts operation after stimulus. Long period of stimulus and strong auxiliary heat load are favored for the reduction of thermal resistance and the shortening of period for start-up. The thermal resistance may be reduced by 29.1 ∼ 69.6 % and the temperature may be regressed by around 8 °C. However, PHP may suffer from temperature uplift and overshot to the maximum evaporator temperature. Therefore, high interference temperature coupled with weak auxiliary heat load and long period of stimulus are suggested as the optimal strategy. The verified strategy offers a new method for local hot spot regression and a possible way to mitigate the risk of thermal runaway, since the heat dissipation is enhanced at the initial stage of damage or destruction. [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]

• Numerically studied the cell-spacing effect on Li-ion battery pack air cooling. • Optimization of cell-spacing is done using DOE method. • Results of numerical simulation are validated by conducting experiments. • The optimum design significantly improves the thermal performance of BTMS. The spacing in a lithium-ion battery pack is crucial in various aspects; including mechanical stability, heat dissipation, temperature distribution, thermal coupling, and cooling effectiveness. This research aims to enhance the cooling efficiency of a 24 V, 10Ah, 4P7S aligned battery pack by optimizing the distribution of spacing among the battery cells. The parameters examined in this study are the longitudinal pitch (D x), transverse pitch (D y), and distance of first row with the side walls (D w). The Computational Fluid Dynamics (CFD) approach is utilized to compute the flow and temperature fields of the battery thermal management system (BTMS). Thereafter, CFD simulations, in conjunction with the Taguchi approach of Design of Experiments (DOE), is used to determine the optimal parameters. Additionally, an experimental set-up is developed to validate the numerical results with experimental outcomes. Thermal performance evaluation includes examining temperature changes both along and across the airflow direction, temperature variation around the circumference of the cells. The key parameters such as maximum temperature (T max), average temperature (T avg.), maximum temperature differential (∆T max), and temperature standard deviation (σT) are also determined. Furthermore, it is assessed that how different distances affect the necessary power (P) and space utilization factor (α) for the airflow. Enlargement of the cooling air vortices within the backflow zone with an increase in D x is observed to cause a drop in T max , T avg. , ∆T max , and σT. In addition, as D y is increased, the values of these parameters fall to a minimum and then begin to rise. D w also shows a similar impact. Changing D x from 20.00 mm to 36.00 mm raises inlet pressure, which causes P to increase by 0.57 W. It is determined that the optimal dimensions to maximize the thermal performance of the battery pack in question are (D y = 24.00, D x = 36.00, and D w = 12.00, mm). The numerical results closely matched with the experimental results, with a maximum absolute relative error of 1.48%. [ABSTRACT FROM AUTHOR]

• Form-stable and flame-retardant CPCM is produced for battery thermal safety management. • The optimum mass ratio of the CPCM is obtained by comprehensive analysis. • CPCM has a positive effect on battery heat absorption and increasing the time between the thermal runaway spread. Phase change materials (PCMs), characterized by zero energy consumption and high energy storage density capability, have a wide range of applications. However, the development of organic PCM is restricted by their low thermal conductivity, easy leakage and high combustibility. In this study, we produced a composite phase change materials (CPCM) with both high thermal conductivity and flame-retardant effect for application in battery thermal safety management. We demonstrated that addition of a porous network structure of EG as a shaping support to increase PA's thermal conductivity, and incorporation of environmentally safe and non-toxic silica-based flame retardant (SiO 2 sol) improved the flame retardant properties. The optimum mass ratio of the CPCM was obtained by comprehensive analysis of the shape and thermal stability, energy storage performance and thermal conductivity. It was also verified by cone calorimetry that the CPCM outperformed pure PA in several aspects: heat release, smoke release rate and emission of toxic gases. The cooling and thermal runaway experiment of the battery module showed that the addition of CPCM had a positive effect on absorption of battery heat and extending the time between the thermal runaway spread of battery modules (21 s increasing to 396 s), providing valuable time for the safe evacuation of people in the event of a runaway fire. [ABSTRACT FROM AUTHOR]

• Various approaches to modeling the thermal behavior of batteries are reviewed with regard to thermal coupled battery models for the thermal analysis of battery and battery thermal management system (BTMS). • Three commonly used battery models for thermal-coupled simulations, simple battery model, electrical circuit model (ECM), and physics-based electrochemical model are reviewed. • The methods of the parameter identification for the thermal-coupled battery modeling are also introduced. • The merits and drawbacks of each model are discussed in detail, and the complexities involved in parameter identification are investigated. • The objective of this extensive review is to assist researchers and engineers in choosing and effectively employing suitable tools for the investigation of battery thermal management. With the increasing popularity of electric vehicles, there is a growing need for efficient and reliable thermal management systems to regulate the temperatures of lithium-ion batteries. Heat generation, which can lead to decreased performance, reduced lifespan, and even safety hazards if not properly managed, is a major challenge for these batteries. This review provides an overview of the numerical modeling techniques used to simulate heat generation and thermal management in lithium-ion batteries for electric vehicles. Various approaches to modeling the thermal behavior of batteries are reviewed with regard to thermal coupled battery models for the thermal analysis of battery and battery thermal management system (BTMS). This review discusses various modeling approaches, including simple battery models, electrical circuit models (ECMs), and physics-based electrochemical models, focusing on the Newman P2D model. Thermal runaway model that is employed to inform safety design for lithium-ion battery is also reviewed. In addition, the parameter identification methods for these models are reviewed. The merits and drawbacks of each model are discussed in detail, and the complexities involved in parameter identification are investigated. This comprehensive review aims to guide researchers and engineers in selecting and utilizing appropriate tools for battery thermal management studies. [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]

This work proposes an accurate prediction of the directional thermal conductivity of wood at the cell wall scale. To that purpose, the strategy combines the physical characterization at the macroscopic scale, the description of the cellular morphology, homogenization calculations and an inverse analysis. The first step consisted in measuring the macroscopic thermal conductivity using the Transient Plane Source (TPS) method in the three material directions of spruce and poplar. The values range from 0.10 to 0.31 W m − 1 K − 1 depending on direction and species. The 3D morphology was acquired by micro-tomography and subsequently processed to generate a digital representation of the cellular structure. This representation is the input geometry in an homogenization procedure. Based on the results of this algorithm, the measurements of the solid fraction and the macroscopic values, we are able to determine the microscopic thermal conductivity of the cell wall λ 0 s , which is impossible to measure directly. λ 0 s was also found to be anisotropic with respective values of 0.6 and 1.0 W m − 1 K − 1 in the transverse plane and the longitudinal direction. • Multi-scale approach was used to predict the directional thermal conductivity of wood at the cell wall scale. • Transient Plane Source method shows conductivity 0.10 − 0.31 W m − 1 K − 1 , depending on direction and wood species. • 3D micro-tomography creates a digital wood cell model for homogenization input. • Inverse analysis, informed by macro measurements and solid fraction, estimates cell wall's micro thermal conductivity. [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]

• Handled the battery thermal management of a novel helical channeled cylindrical Li-ion battery. • Tested the performance of nanofluid and hybrid nanoparticle-enhanced phase change material for BTMS. • Noticed that the cooling channel arrangement actively removes stored heat from PCM, and reduces PCM temperature. • Observed that the coolant circulation rate keeps the cell temperature below the safe range even with a lower circulation rate of 30 mL/min. Electric vehicles (EVs) have emerged as a viable alternative to Internal Combustion (IC) engine-powered vehicles, and efforts have been directed toward developing EVs that are more reliable and safer to operate. The safe working of EVs necessitates the use of an efficient battery cooling system. In this paper, cooling of cylindrical type Li-ion battery embedded with helical coolant channels is proposed. The effects of nanoparticles on removing heat from the battery cooling system have been investigated for four different nanoparticle concentrations: 0, 2, 5, and 10% of Al 2 O 3 in the base fluid. Two cases of base fluids are considered: phase change material kept in a concentric container surrounding battery volume and coolant water circulated through liquid channels attached to the outer walls of the PCM (phase change material) cylindrical container. This study presented the three configurations (i) base case PCM-WLC: battery cooling system with a cylindrical enclosure filled with RT-42 phase change material. (ii) base case nePCM-WLC: battery cooling system filled with nano-enhanced phase change material. (iii) nePCM-LC: battery cooling system with helical liquid channels and filled with nano-enhanced PCM. The nanofluid was circulated through the liquid passages connected to the PCM container. Results showed using the helical channels, the nePCM-LC arrangement efficiently removes accumulated heat from the phase change material and provides better battery cooling than straight rectangular channel-based BTMS (battery thermal management system). [ABSTRACT FROM AUTHOR]

• Effect of structural parameters on MSTV design in a cooling plate are investigated. • Temperature, pressure and velocity distributions in MSTV design are analysed. • Reverse flow MSTV maintained maximum temperature less than 40 °C. • Less pressure drop noted with large channel width, curve radius, and valve angle. • Channel design showed a substantial impact on thermo-hydraulic performance. With the active promotion of the green energy vehicle sector in recent years, electric vehicles have garnered widespread attention as their future direction. The operating temperature substantially influences the functioning of power batteries, as being one of the key components of electric vehicles. Battery thermal management is vital for improving electric vehicles' performance and durability. Concerning this, a novel 4-channelled liquid cooling plate with reverse flow multi-stage Tesla valve (MSTV) design developed in our previous work is further analysed to effectively manage an undesirable temperature distribution in a cell. The effects of structural parameters, including channel width, outer curve radius, and valve angle, are investigated numerically for a wide range of Reynolds number by applying heat flux on the cooling plate's upper and lower surfaces using COMSOL Multiphysics software. Results indicate that a large channel width, a large outer curve radius, and a small valve angle in MSTV can effectively reduce peak temperature rise of a standard 20Ah pouch li-ion battery of 160 mm × 227 mm × 7.25 mm dimension. Alongside, the variation in pressure drop is minimal with the increase of outer curve radius and valve angle except for the channel width for a given Reynolds number. [ABSTRACT FROM AUTHOR]

It is seen from this figure that the maximum temperature rise of the cell module decreases as the increasing rate of fluid flow. The maximum temperature rise of the cell module is under 40 °C and 36 °C respectively since the flow rate is 0.40 × 10−3 L·s−1 and 1.20 × 10−3 L·s−1, indicating that increasing flow rate increases the cooling capability of the LCP. • A new cooling plate is developed for controlling undesirable cell temperature field. • Inlet and outlet of cooling plate have big impact on cell temperature distribution. • Increasing flow rate decreases cell temperature rise markedly. • Cooling plate channel width has weak impact on cell temperature distribution. • Channel width has great effect on ratio of power consumption of cooling plate. The thermal management for a lithium ion battery cell plays a pivotal role in enhancing the cell performance and reliability for electric vehicles. In this work, a novel serpentine-channel liquid cooling plate with double inlets and outlets is developed for better managing an undesirable temperature distribution of a cell module. With a simplified model for the cell module, numerical analyses are implemented using the software of FloEFD to study effects of flow directions, flow rates and channel widths of the cooling plate on cell temperature distribution under different operating conditions; Likewise, a ratio of power consumption as a non-dimensional number is defined to analyze the hydraulic performance of the developed cooling plate. Results show that locations of the inlet and the outlet as well as flow directions have great impacts on the cell temperature distribution and the ratio of power consumption of the cooling plate. Increasing fluid flow rate substantially decreases the maximum temperature rise of the cell module while it has little effect on the temperature distribution. Moreover, the channel width of the cooling plate has a strong influence on its ratio of power consumption as well as the cell temperature distribution but it has a weak influence on the cell maximum temperature rise. Interestingly, the developed serpentine-channel cooling plate offers one a new method to design a lithium ion battery thermal management system for controlling temperature distribution of a cell module. [ABSTRACT FROM AUTHOR]

It is seen from these two figures that the battery temperature and SOC have a minor effect on its thermal conductivity. Battery thermal conductivity vary with the battery types heavily. • A novel method for determining thermal parameters of lithium ion cells is presented. • Temperature has a linear effect on thermal conductivity and specific heat of cells. • Cell temperature has a higher effect on its specific heat than thermal conductivity. • Cells' thermal conductivity and specific heat vary with the battery types. • The method is more effective to test thermal conductivity and specific heat of cells. Characterizing thermal parameters of a lithium ion battery is a key step to predict the temperature distribution of battery cell modules. In this work, a novel method is developed based on the quasi-steady state heat transfer analysis to determine the thermal conductivity and the specific heat simultaneously. Both prismatic lithium iron phosphate cells and pouch cells with different electrode materials are used in this experimental test. A constant heat flux is applied to the cell surface whereas the heat loss is estimated based upon the temperature drop curve. As such, the quasi-steady state heat transfer can be attained to determine cell thermal parameters. It is observed that cell thermal parameters increase linearly with the increase of the operating temperature. Furthermore, the operating temperature has a more significant influence on the cell specific heat than the thermal conductivity, while the effect of the state of charge has a minimal effect on these two parameters. The current method demonstrates an effective and practical way to determine the thermal conductivity and specific heat of the cell simultaneously. [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]

Highlights • A novel pulse self-heating strategy is proposed to enable quick warming of the battery. • The battery is heated up using pulse self-discharge signal generated by self-designed circuit. • Pulse heating can provide faster heating with lower polarization. • Internal resistance and off-period voltage are predominant influence on heating duration. • Higher SOC is suggested for pulse heating to achieve heating duration within 200 s. Abstract Battery warming at low temperature is a critical issue affecting battery thermal management. In this study, the pulse self–heating strategy is proposed to enable quick and safe warming of lithium–ion battery at low temperature. The battery is heated up using pulse self–discharge. This strategy can heat up 18,650 commercial battery with a control circuit and alleviate the battery degradation during heating. Compared with continuous direct current self–heating, the battery can be heated up from −10 °C to 10 °C by pulse heating within 175 s while the direct current heating consumes 280 s with approximating polarization voltage. The effects of ambient temperature, switching interval, and initial state–of–charge on heating performance are further investigated. Heating duration is found to be insensitive to the switching interval in the studied range. Conversely, battery internal resistance and off–period voltage at different ambient temperatures and initial state–of–charges are found to be the predominant factors that influence heating duration. Heating duration in the range of 150–180 s is achieved at ambient temperature ranging from −10 °C to 0 °C. In real applications, pulse heating is recommended to be performed at higher initial state–of–charge (>0.8), at which heating duration is within 200 s. [ABSTRACT FROM AUTHOR]

Highlights • Effective medium model developed considering high Knudsen effects. • Thermal conductivity measured changing temperature, compression, and environment. • Model effectively tuned to collected data. • Anisotropy estimated from measurements and specific heat estimates. • X-ray CT scans show the source of the anisotropic nature. Abstract Ceramic insulations are often used to mitigate heat losses from high temperature systems. In the case of thermal batteries, insulation is exposed to high temperatures, high axial loads, shock and vibration scenarios, and alternate gaseous environments. All of these conditions influence the effective thermal conductivity of the material and subsequently the performance of the battery. To properly balance the thermal design of these systems, a model that can capture the influence of these variables on the effective thermal conductivity is necessary. A previous publication presented the development of an effective thermal conductivity model for two common materials used for thermal batteries. This paper investigates the application of this model to Min-K TE1400 board, whose microstructure interrupts gas phase conduction to minimize thermal conductivity. This necessitates modifications to the model to accurately represent effective thermal conductivity for this type of material. Thermal conductivity was measured as a function of temperature and compression in air, helium, and partial vacuum environments using the Transient Plane Source (TPS) technique. The trends observed in the measured thermal conductivity are explained through pore size measurements of compressed samples. The effective medium model was tuned using this data and is shown to agree with experimental data. Lastly, the anisotropy of the material was evaluated using the TPS data and specific heat estimations. This showed that axial conductivity is consistently less than radial thermal conductivity, as is corroborated by X-ray CT analysis of the fiber orientations in the material. The results and implications of the anisotropic results are also discussed. [ABSTRACT FROM AUTHOR]

Highlights • A plug-in OHP with flat-plate evaporator and tube condenser was developed. • Excellent heat transfer performance of plug-in OHP was achieved using ethanol-water mixtures. • EV battery temperature could be well-controlled below 46.5 °C based on the plug-in OHP. Abstract The development of highly-efficient, cost-effective, and reliable cooling schemes of electric vehicle (EV) battery is still a big challenge for massive commercialization of EVs. In this work, a proof-of-concept plug-in oscillating heat pipe (OHP) with flat-plate evaporator and tube condenser has been developed and experimentally tested for the potential applications in EV battery thermal management. Pure water, ethanol, and binary-fluid mixtures of them at different mixing ratios (MRs) ranging from 1:1 to 4:1 were used at volumetric filling ratios (FRs) of 30%, 40% and 50%. Owing to the zeotropic properties in phase transition and the complex molecular interactions between the ethanol component and water component, the OHP charged with ethanol-water mixtures exhibited better start-up and heat transfer performance. The average battery pack temperature could be controlled below 46.5 °C under the power input of 56 W. Besides, well-satisfied temperature uniformity was achieved on the battery module and the maximum temperature differences were mostly in the range of 1–2 °C. The complementary features for ethanol-water mixture thermo-physical properties and temperature/concentration gradients induced mass transport account for the OHP performance improvement. The novel plug-in OHP associated with desirable heat transfer performance provides a promising candidate for battery thermal management system. [ABSTRACT FROM AUTHOR]

• The predicted results agree with the experimental results an average error of 1.28%. • Coolant-improved flow direction and thermophysical properties significantly affect the decreasing maximum operating temperature and temperature gradient across a cell. • The highest temperatures of the battery module are 30.06 °C, 30.00 °C, 29.91 °C, 29.89 °C, and 29.49 °C for models II, IV, III, I, and V. • The maximum temperature gradient across a cell, models I, II, and III give the highest value [0.42 °C], and consequently, models [0.40 °C] and model v [0.15 °C]. The operating battery temperature significantly affects electric vehicle performance, reliability, and safety. Therefore, batteries need to keep within the operating temperature design. The 3D Eulerian model is applied to determine battery thermal behavior with five different flow directions of coolant throughout the battery pack jacket. The computational domain consists of sixty cylindrical Li-ion cells inserted into the cooling module socket with constant power input conditions. The predicted results are consistent with the experimental results, with an average error of 1.28%. Coolant-improved flow direction and thermophysical properties significantly affect the decreasing maximum operating temperature and temperature gradient across a cell. The highest temperatures of the battery module are 30.06 °C, 30.00 °C, 29.91 °C, 29.89 °C, and 29.49 °C for models II, IV, III, I, and V, respectively. In addition, for the maximum temperature gradient across a cell, models I, II, and III yield the highest value [0.42 °C], followed by models IV [0.40 °C] and model V [0.15 °C], respectively. The proposed battery nanofluid cooling pack can therefore optimize the thermal management system of the EV pack. [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 novel petal-type battery thermal management system (BTMS) with dual phase change materials (PCMs) is proposed. • The thermal performance of the proposed BTMS at different ambient temperatures and discharge rates is investigated. • The environmental adaptability of 18650 Li-ion batteries is significantly improved. • The proposed BTMS is optimized by fin-reinforced heat transfer technology. Phase change material (PCM) cooling is a prominent approach for battery thermal management. However, its application scenario is severely limited by the narrow range of phase change temperature. When the temperature of PCM does not reach the phase change temperature range, it is either a pure thermal conductive material or a completely molten liquid material, neither of which can play a role in battery thermal management. The present study proposes a novel petal-type battery thermal management system (BTMS) with dual PCMs, which has significantly enhanced the environmental adaptability of the battery based on PCM cooling. The thermal performance of the BTMS at different ambient temperatures and discharge rates is investigated by numerical simulation methods. The results show that when the battery is discharged at 1∼5C at an ambient temperature of 25°C, the maximum battery temperature (T max) is 29.87°C, 32.89°C, 34.69°C, 36.84°C, and 39.41°C, respectively. When the battery is discharged at 2C at 20°C, 30°C and 40°C, the T max is 30.49°C, 34.16°C and 43.70°C, respectively. Compared with the other two conventional BTMSs using a single type of PCM, the thermal performance and environmental adaptability of the proposed BTMS is the best under the three typical ambient temperatures. Furthermore, the above BTMS is optimized using fin-reinforced heat transfer technology in this paper. Compared to the BTMS without fins, the optimized solution 2 with asymmetric fin arrangement reduces the maximum temperature difference (Δ T max) by 5.53% and 29.19% and the maximum temperature rise (Δ T mrise) by 36.15% and 42.76% at ambient temperatures of 30°C and 40°C. [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]

• A novel BTMS is proposed to inhibit thermal runaway propagation. • The BTMS integrates phase change cooling, nanofluid cooling and aerogel. • The parameters affecting the cooling performance of nanofluids are discussed. • Regression analysis is used to find the best combination of parameters. Nowadays, lithium-ion batteries are widely used in electric vehicles as the power source and its safety attracts increasing attention. Particularly, the thermal runaway is a highest risk needed to be solved. In order to effectively inhibit thermal runaway propagation, an efficient and energy-saving battery thermal management system is proposed in this study, which integrates phase change cooling, nanofluid cooling and heat insulation materials. Firstly, the system model is established by integrating electrochemical model, thermal model and fluid model, and the validity of the model is analyzed. Then the cooling performance of the system under two working conditions is discussed. In the normal heat dissipation condition, Scheme 6 can effectively inhibit thermal runaway propagation and reduce the maximum battery temperature from 1013.50 K to 328.34 K. In the extreme condition, Scheme 6 can reduce the maximum battery temperature from 980.51 K to 380.34 K, and the heat in the system can be taken away in time. In addition, the effects of the volume fraction of nanoparticles and the flow rate of nanofluids on the cooling performance are studied. Finally, for purpose of further improving the cooling performance, uniform-precision rotatable central composite design is used to establish the regression equation and determine the best combination factors. Comparing with Scheme 6, the maximum battery temperature in the improved scheme is reduced by 23%, and the economic index is reduced by 22%. [Display omitted] [ABSTRACT FROM AUTHOR]

• Thermal performance of refrigerant-based battery thermal management system for a real HEV battery pack is analyzed. • Effect of battery discharging C-rate, refrigerant mass flow rate, inlet temperature, vapor quality, and heating power on thermal performance of battery pack is studied. • Thermal performance of battery pack at real driving cycle operational conditions for refrigerant cooling is discussed. • Heat flow distribution on the battery pack at different discharging C-rates is analyzed. The thermal performance of refrigerant-based battery thermal management system (BTMS) for a real HEV battery pack in both the cooling and heating conditions is numerically and experimentally investigated in this paper. The heat generation model of battery cells and the numerical methodology for predicting the cooling performance of refrigerant-based cooling system are validated by experiments and the predicted results are consistent with experimental data. The effects of discharging C-rate, mass flow rate, initial temperature and vapor quality of refrigerant on thermal performance of battery pack are analyzed in detail. The thermal performance of refrigerant-based BTMS at a real driving cycle is also examined. The results indicate that the discharging C-rate has a significant impact on thermal performance of battery pack due to the distinctive heat transfer behaviors of battery pack at different discharging C-rates. Increasing mass flow rate of refrigerant is contributed to descend the maximum temperature and improve temperature uniformity of battery pack. Decreasing initial temperature of refrigerant is beneficial to reducing the maximum temperature of battery pack but is disadvantageous to temperature uniformity. The effect of vapor quality on thermal performance of battery pack is limited. The cooling performance of refrigerant satisfies the requirement of BTMS at the real driving cycle. The optimum heating power of the battery pack at heating condition ranges from 400 W to 460 W. [ABSTRACT FROM AUTHOR]

• Diverging channel design cooling plate with oblique fins is newly proposed. • Thermal unbalance of the battery module is improved using the proposed design. • Cell-to-cell temperature difference in the pack cooling is decreased by 19.07%. • The pumping power to satisfy the temperature conditions is decreased by 67.8%. In this study, the thermal and hydraulic performances of a battery thermal management system are investigated in terms of the design of the cooling plate. A diverging channel with oblique fins (DCOF) cooling plate is newly proposed to overcome the limitations of the conventional straight channel cooling plate. The diverging design is applied to control the coolant velocity and heat transfer area, with oblique fins inserted to enhance the heat transfer efficiency. A simulation model of the battery and cooling system is developed and experimentally validated. When the DCOF design is applied to the battery module, the temperature uniformity is improved in terms of the temperature difference and standard deviation. As the investigation is extended from the module to the battery pack, the temperature difference and temperature standard deviation in the battery module are improved by 19.07% and 27.14%, respectively. Considering the power consumption of the cooling system, as the thermal performance of the DCOF design and baseline design is maintained, the power consumption of the coolant pump of the DCOF design is significantly reduced by 67.8%. [ABSTRACT FROM AUTHOR]

• Common factors of inefficient cooling invoke the formation of universal solutions. • Airflow uniformity is the dominant factor for battery air-cooling. • Increased air residence time improves the uniformity of air distribution. Inspired by the ventilation system of data centers, we demonstrated a solution to improve the airflow distribution of a battery energy-storage system (BESS) that can significantly expedite the design and optimization iteration compared to the existing process. A defective cooling system of a BESS decreases the overall operational efficiency and increases the risk of thermal runaway, but current design optimizations rely on a case-by-case approach. The solutions of this fashion are both time-consuming and costly because of the laborious recursive process. The desire to eliminate the time for development motivates us to pursue a more general path for design optimization. In this work, we identified the similarity of geometry between the data center and the BESS, as well as the factors that induced the unbalanced airflow distribution. Inspired by the data-center thermal management, we propose a generalized solution of layout arrangement that we applied to the BESS design. We performed a quantitative analysis of cooling performance and investigated the flow patterns under given operating configurations. After modification, the maximum temperature difference of the battery cells drops from 31.2°C to 3.5°C, the average temperature decreases from 30.5°C to 24.7°C, and the coefficient of performance (COP) increases four-fold. The modification shows an improvement in temperature uniformity, overall temperature and COP. The cooling solution applicable to the general container BESS design demonstrates the enormous potential for an effective and rapid design optimization. [Display omitted] [ABSTRACT FROM AUTHOR]

• Research on battery thermal management systems containing refrigerants and coolants is developed. • The alternate and simultaneous operation of two fluids are studied in this paper. • Alternate cooling saves energy and prolongs compressor start-stop interval time. • Simultaneous cooling prolongs the compressor operating time with a conditional energy-saving effect. The refrigerant cooling scheme can effectively deal with the problem of battery cooling but with a poor economy. A novel battery thermal management (BTMS) called dual flow medium system (DFMS) is proposed in this paper, which is more economical than the refrigerant cooling scheme. The DFMS contains the refrigerant cooling system (RCS) and the coolant cooling system (CCS). The alternate cooling mode and the simultaneous cooling mode of the DFMS were studied under different coolant flow rates, the control range of the batteries' average temperature, and ambient temperature. The results show that the alternate cooling mode makes power consumption saved by 49.15% maximumly when the ambient temperature is 18.3°C and the compressor start-stop interval time is prolonged. The simultaneous cooling mode can prolong the compressor operating time by 16.3% and save a little energy under an appropriate coolant flow rate. The DFMS provides a novel option for the design of BTMS, and the research on the operating modes of the DFMS lays a good foundation for its further development. [ABSTRACT FROM AUTHOR]

• Comprehensively analyze the gas composition generated by LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells. • Compare proportion of main gas of thermal runaway lithium batteries in studies. • Propose and compare three methods to obtain the venting rate. Lithium-ion batteries have been widely used as a power supply and energy storage device, but safety issues such as thermal runaway still make the application not very optimistic. Venting is one of the thermal runaway characteristics of lithium-ion batteries. The gas composition and venting rate is of far-reaching significance for evaluating the impact of batteries on the environment and people, predicting and simulating the development of thermal safety events. Therefore, in this study, a large-format pouch power battery (LiNi 0.8 Co 0.1 Mn 0.1 O 2) was investigated for venting during thermal runaway, including composition and rate. The thermal runaway processes of 0%, 50%, and 100% SOC cells were analyzed according to the temperature, pressure, and video recordings. The gas chromatograph-mass spectrometer (GC-MS) was used to comprehensively identify the venting gas composition of cells. Results show that with the increase of SOC, the gas production composition of the battery became more complex, and the marked gas concentration was higher. The gas and heat production of the cells also increased accordingly. The gas production mechanism of the thermal runaway cells is revealed, and it is believed that the increase in the amount of lithium intercalation in the negative electrode enables more gas production reactions to occur more thoroughly. Besides, three methods for predicting the cell's venting rate based on mass loss, temperature and pressure changes, and gas concentration are compared. [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 novel design for BTMS is proposed to separate the propagation of thermal runaway. • Th BTMS unites phase change cooling, liquid cooling and thermal insulation material. • The electrochemical-thermal and heat transfer-laminar flow coupling model is built. • The influence of coolant flow rate on the novel BTMS in the extreme case is analyzed. Nowadays, electric vehicles attract much attention due to the advantages of low energy consumption and zero emission. As the power source of electric vehicles, the safe and stable operation of lithium ion battery is very important. However, owing to overcharge, mechanical collision, overheating or other conditions, the battery may occur thermal runaway, which can cause serious accidents such as fire or explosion. To solve this problem, an efficient and energy-saving battery thermal management system becomes a necessary choice. In this paper, a novel integrated battery thermal management system with multi-measure prevention strategy is designed and analyzed, which is mainly composed of the composite phase change material, aerogel and cooling-channel. Firstly, the electrochemical-thermal coupling mathematical model is established, and then the reliabilities of thermal runaway model, phase change cooling model and liquid cooling model are verified, respectively. Next the numerical simulation including the effect of different operating modes, extreme case and coolant flow rate on the battery thermal management system is carried out, and finally the results are discussed in detail. The results show that the battery thermal management system can not only quickly take away the accumulated heat and separate the propagation of thermal runaway, but also maintain the temperature uniformity of battery. [Display omitted] [ABSTRACT FROM AUTHOR]

• We propose a thermophoretic microfluidic cell to measure the Soret coefficient quantitatively. • Verification of one-dimensional temperature and concentration gradient in cell. • We demonstrate that the obtained Soret coefficients agree with a validated method. [Display omitted] Thermodiffusion or thermophoresis gained much interest in bio, chemical, and energy engineering. Although there are several methods to measure thermophoresis, they consume large sample volumes, are limited to binary mixtures, and give only indirect access to the applied temperature profile. Herein, we propose a thermophoretic microfluidic cell for quantitative measurements of the Soret coefficient of colloids. The actual microscale measuring channel lies between cooling and heating channels to achieve a one-dimensional temperature gradient. Fluorescence lifetime imaging microscopy with Rhodamine B is utilized to measure the spatial temperature profile in the channel. The fluorescence intensity of fluorescently labeled polystyrene particles with a diameter of 25 nm is used to monitor the concentration profile. The observed temperature and concentration profiles are one-dimensional, as gradients in the longitudinal and height directions can be neglected. In the investigated temperature range, the averaged difference between the measured Soret coefficients with the cell and determined with the Thermal Diffusion Forced Rayleigh Scattering set-up is less than 8%. [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]

• Different reverse flow patterns in parallel channel heat sink were captured. • Effects of inlet subcooling and mass flux on flow instability were discussed. • Variations of standard deviation of the inlet and outlet pressure were analyzed. • Instability maps were established based on different parameters. The present study focused on the flow boiling instability of R1233zd(E) in a 21 parallel mini-channel heat sink designed for the application on battery thermal management. Experiments were conducted under different conditions, including inlet subcoolings (2.5–8 K), mass fluxes (111–276 kg/m2 s), and heat fluxes (up to 12 W/cm2). A high speed camera with the frequency of 2000 fps was used to capture the unstable flow pattern. The results showed that the period and the initial position of reverse flow were shortened with the increase of heat flux, meanwhile four typical reverse flow patterns in the parallel channel were captured. The Parallel Channel Instability (PCI) featured by large inlet pressure oscillation was suppressed when the inlet subcooling was increased, while mass flux had limited influence on the suppression of PCI. The standard deviation of inlet pressure σ (p in) was increased obviously under the inlet subcooling of 5 K. Beside, faster elevation of σ (p in) was observed under 111 kg/m2 s when the heat flux was higher than 3.8 W/cm2. Finally, the flow instability maps were established based on heat flux, mass flux and dimensionless parameters of subcooling number N sub and phase change number N pch. The stable, transition and instability regions were divided on the maps based on the operating conditions and the flow patterns captured during the experiment. [ABSTRACT FROM AUTHOR]

• The evap. and cond. HTCs of 9 AMFHPs with 3 fluids at FR100% were tested. • Higher q e causes the rise of evap. HTCs and the fall of cond. HT of most samples. • Higher v air results in the fall of evap. HTCs as well as cond. HT of most samples. • Cooper correlation predicts the evap. HTCs of AMFHPs at high FR excellently. • Rohsenow correlation predicts cond. HTCs of R134a at FR100% well. An experimental investigation was conducted to evaluate the evaporation as well as condensation heat transfer of air-cooled multi-port flat heat pipes (AMFHPs), designed for extreme working conditions of power battery thermal management in electric vehicles. The experimentally obtained evaporation as well as condensation heat transfer coefficients (HTCs) under various working conditions were compared and analyzed. It was found that, both the orders of the intensity of heat transfer mode in the liquid pool and the condensation Nu c were R134a > ammonia > acetone. The orders of the evaporation HTCs referring to ammonia and R134a AMFHPs with different filling ratios (FRs) were 50 > 30 > 100 > 70 and 30 > 50 > 70 > 100%, while those of Nu c were 50 > 30 > 70 > 100 and 30–50–70 > 100%, respectively. In most cases, evaporation HTC increased with the rise of heating power as well as the decrease of cooling air velocity, while the condensation Nu c decreased with the increasing in the heating power as well as the air velocity slightly. The measured evaporation HTCs were compared with some predictive correlations of pool boiling and pool boiling-thin film evaporation expressions for the evaporator section at different FRs, and the condensation HTCs were also evaluated by several available filmwise condensation models. Results showed that Cooper correlation for pool boiling revealed quite a good agreement with measured results for the AMFHPs of 100% R134a, 70% ammonia and 100% ammonia, and Rohsenow correlation predicted the condensation HTCs of R134a AMFHPs with FR<100% accurately. However, for ammonia, the prediction of the evaporation HTCs in the case of FR < 70% was difficult, and Nusselt theory significantly overestimated the condensation HTCs of all the ammonia samples. [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]

• A direct optimization strategy for efficient design of parallel BTMS is developed. • Field synergy equation is employed to obtain the optimal flow rate distribution. • Flow resistance network model is used to directly calculate the optimal parameters. • Experiments are carried out to demonstrate the effectiveness of numerical method. • >The optimized BTMSs in this study exhibited remarkably enhanced cooling performance. Air-cooled battery thermal management system (BTMS) is critical for the safety and performance of electric vehicles. The system design needs to be optimized to achieve best thermal stability and uniformity. The current optimization methods for system design require empirical adjustment and contain randomness, which impedes to get the optimal system design. In this work, a direct optimization strategy based on field synergy equation is proposed for the optimal design of BTMS. Field synergy equation is introduced to calculate the optimal flow rate distribution in the system, which is combined with flow resistance network model to obtain the optimized structural parameters of the system. The developed strategy is adopted to optimize the parallel channel width distribution and plenum angle of BTMS. Computational fluid dynamics method and experiment are utilized to evaluate the cooling performance of BTMS. The results show that the temperature difference (Δ T max) in battery pack after parallel channel width optimization is reduced by at least 49% without pressure drop increased, while Δ T max after plenum angle optimization is reduced by at least 56% with pressure drop slightly increased. Mechanism of convective heat transfer optimization is taken into consideration by using field synergy equation in the proposed direct optimization strategy, which thus eliminates the burden of repeated adjustment of structural parameters and exhibits high efficiency for design of parallel cooling system. The developed optimization strategy is believed to guide the thermal design of battery packs to enhance their performance and safety. [ABSTRACT FROM AUTHOR]

• A hybrid system coupled PCM with liquid cooling for battery module is proposed. • The thermal performance of battery module with cells connected in series is studied. • The polarization in cell is quantified by a theoretical method. • The discharge uniformity for two cooling systems is compared. • The thermal and electric performances are optimal with coolant at 30 ℃. The thermal management is of vital importance for the secure and highly efficient operation of lithium-ion battery pack. In this work, a new hybrid thermal management system combined with PCM and liquid cooling by a thermal conductive structure is proposed, and the electrochemical-thermal coupling models are developed for the lithium-ion battery module connected in series, by which the hybrid cooling system is preliminarily optimized by studying the effects of separation between cells and inlet water velocity on the electrochemical and thermal performances. The maximum temperature and maximum temperature difference decrease as the separation increases, but the drop rate gets small when the separation exceeds 4 mm. Moreover, the maximum temperature falls while the maximum temperature difference rises with increasing the water velocity. A theoretical calculation is adopted to analyze and quantified the uneven discharge, finding that the diffusion polarization in electrolyte is the key issue for the discharge unbalance among the cells in battery module, which can be improved by the proposed hybrid cooling. Finally, the optimized inlet water temperature of 30 ℃ is recommended, at which the discharge and temperature uniformities perform best, and the maximum temperature is kept below 40 ℃. [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]

• Micro-channel cold plate was used for battery thermal management. • The optimal value area of tree net can be obtained through construction theory. • Increasing flow rate decreases cell temperature rise markedly. • The tree-like net has more obvious pressure drop advantage than the serpentine net. To improve the battery life and promote the application of electric vehicles, microchannel cooling technology had been widely developed. Therefore, this study was inspired by bionics and designed a novel (anode, cathode) double-layer tree-like channel cooling plate based on constructal theory. The anode side was dispersed with a cooler coolant. And the cathode side was used as a hot fluid collecting layer. Meanwhile, the effects of three structural parameters (length ratio, height to width ratio and channel volume fraction) on maximum temperature and standard deviation of surface temperature were investigated. The obtained results demonstrated that optimal maximum temperature and temperature uniformity were achieved at a length ratio of about 0.70, a height to width ratio close to 70/100 and the channel volume fraction of about 0.06. In addition, increasing inlet mass flow rate can obtain the required heat dissipation capacity but at the expense of pressure drop. At the same time, the characteristic changes of the flow thermal characteristic parameters were compared with the serpentine net under the same heat transfer surface area. In summary, the maximum temperature and the standard deviation of surface temperature of the optimized cold plate are reduced by 1.79% and 69.25%, respectively. And the pressure drop reduced by 79.13%. The optimal case in this research can be widely applied to enhance the cooling performance in liquid-cooled BTMS. [ABSTRACT FROM AUTHOR]

• The cold plates of battery liquid cooling system are designed by topology optimization. • Consider the two cold plate models the inlet and outlet on the centerline or the diagonal. • Compare the numerical results of design cold plates with rectangular-channel and serpentine-channel cold plates. • Topology optimization cold plates have better cooling performance and lower flow resistance at the same inlet pressure. • The change of inlet pressure has an impact on the cooling effect of the cold plates. In this paper, the cold plates are designed to cool the rectangular lithium-ion battery packs by the topology optimization method. The topology optimization method obtains the channel structure in the two-dimensional model, and three-dimensional cold plate models are then established according to their two-dimensional structure. In a simple model for a battery pack, numerical analyses of topology optimization cold plate (TCP) are implemented using COMSOL software. Numerical results were compared with conventional rectangular-channel cold plate (RCP) and serpentine-channel cold plate (SCP) to investigate the cooling performance and flow characteristics of the cold plate. The results demonstrate that the flow channel structure of the cold plate has a significant influence on the temperature distribution of the battery. At 150 Pa inlet pressure, the maximum temperature of batteries with TCPs is reduced by 0.27% and 1.08% compared to that with RCP or SCP, and the temperature difference is lowered by 19.50% and 41.88%. Appropriately increasing the inlet pressure of the cold plate can also reduce the maximum temperature and temperature difference of batteries. Due to low flow resistance and high heat transfer coefficient, topology optimization will be widely used to design battery cold plates. [ABSTRACT FROM AUTHOR]

• Design of a liquid cooling system for EV batteries based on the constructal law • Canopy-to-canopy architectures prove to have high thermal efficiency • They allow to maintain the battery cell below the critical temperature level With the growing interest on electric vehicles comes the question of the thermal management of their battery pack. In this work, we propose a thermally efficient solution consisting in inserting between the cells a liquid cooling system based on constructal canopy-to-canopy architectures. In such systems, the cooling fluid is driven from a trunk channel to perpendicular branches that make the tree canopy. An opposite tree collects the liquid in such a way that the two trees match canopy-to-canopy. The configuration of the cooling solution is predicted following the constructal methodology, leading to the choice of the hydraulic diameter ratios. We show that such configurations allow extracting most of the non-uniformly generated heat by the battery cell during the discharging phase, while using a small mass flow rate. [ABSTRACT FROM AUTHOR]

• A Domino prediction model of thermal runaway propagation is proposed. • This model proposes that whether the battery thermal runaway is a probability event. • The thermal runaway propagation path and probability is analyzed. • The thermal runaway propagation process is divided into four stages. Currently, the thermal safety issue of lithium-ion battery (LIB) has become a major challenge to restrict its development. In this work, the thermal runaway propagation (TRP) process of the 18,650-type LIB module is studied by experimental and modeling methods. A novel experimental-based Domino prediction model is proposed, which can predict the TRP path and its probability. The calculation part of the model is realized with the Matlab software. This model for the first time proposes that whether the battery thermal runaway (TR) is a probability event, and the probability is a function of its temperature. To verify the feasibility of the model, the TRP process in a 4 × 4 arrangement battery module with three different first TR battery locations is detailed analyzed. The results show that the dangerous level ranking of cell locations from low to high is the corner location, the edge location, and the location near the module center. Higher dangerous level means more maximum probability TRP paths and higher probability. Moreover, it was found that the whole TRP process can be divided into four stages: the TRP trigger stage, the heat accumulation stage, the Domino effect stage, and the TRP stop stage. The proposed model can effectively predict the TRP process in modules, and the results have important reference value for the design of the battery thermal management system and the research on the method of blocking TRP. [ABSTRACT FROM AUTHOR]

• A reaction-conduction theory is developed for in-cell runaway propagation. • Analytical solution from asymptotic analysis is acquired for propagation speed. • Numerical solution is acquired from phase portrait and heteroclinic orbit. • Good agreement between analytical and numerical solution. • Capable to evaluate thermal runaway propagation speed at various conditions. In this work, a coupled reaction-heat conduction model is developed to describe battery thermal runaway propagation within a single cell. By nondimensionalizing the governing equation and exploiting the largeness of a dimensionless parameter β , analytical solutions for the reaction front propagation speed are obtained based on asymptotic analysis, as a function of both β and dimensionless temperature θ u. Numerical solution of the model is obtained using the phase portrait and the heteroclinic orbit to further justify the analytical results, where satisfactory agreement is achieved specially for large β. This solution can be applied to a wide range of battery system parameters, including thermal diffusivity, exothermicity, activation energy, reaction order as well as the ambient temperature. It is shown that the thermal runaway propagation speed decreases with increasing β , and increases with battery temperature. Also, thermal structure of reaction front is compared among different β and θ u , showing thinner reaction front for faster propagation waves with smaller β and larger θ u. Lastly, by adopting battery parameters from the literature in the analytical formula, thermal runaway propagation speed is estimated in a typical condition. The results can provide useful insights into battery thermal runaway propagation and its prediction. [ABSTRACT FROM AUTHOR]

l The critical thermal issues of lithium-ion batteries are introduced. l The design principles for batteries thermal management are presented. l The latest advances on battery thermal management systems are summarized. l Emerging technologies for next-generation power batteries are discussed. Replacing conventional gasoline-powered cars with electric vehicles (EVs) can reduce not only pollution emissions but also the dependence on fossil fuels. As the most widely used power source to propel EVs, lithium-ion batteries are highly sensitive to the operating temperatures, rendering battery thermal management indispensable to ensure their high performance, long cycle life and safe operation. In this review, we summarize the recent advances in thermal management for lithium-ion batteries. The critical thermal issues caused by high temperature, low temperature and temperature non-uniformity are firstly discussed. The design principles and the existing thermal management systems are then presented and elaborated extensively. Emerging technologies such as thermoelectric devices and internal heating methods for future battery thermal management are analyzed. We highlight that the combination of passive and active cooling/heating methods is promising to meet the stringent thermal requirements, particularly under dynamic conditions with drastic power fluctuations. Finally, the remaining challenges and perspectives of thermal management systems with high efficiency and durability are provided. This review offers comprehensive guidance on the design of advanced thermal management system for next-generation power batteries. [ABSTRACT FROM AUTHOR]