Liquid cooling based on thermal silica plate for battery thermal management system

To achieve safe, long lifetime, and high‐performance lithium‐ion batteries, a battery thermal management system (BTMS) is indispensable. This is especially required for enabling fast charging‐discharging and in aggressive operating conditions. In this research, a new type of battery cooling system based on thermal silica plates has been designed for prismatic lithium‐ion batteries. Experimental and simulations are combined to investigate the cooling capability of the BTMS associated to different number of cooling channels, flow rates, and flow directions while at different discharge C‐rates. Results show that the maximum temperature reached within the battery decreases as the amount of thermal silica plates and liquid channels increases. The flow direction had no significant influence on the cooling capability. While the performance obviously improves with the increase in inlet flow rate, after a certain threshold, the gain reduces strongly so that it does not anymore justify the higher energy cost. Discharged at 3 C‐rate, an inlet flow rate of 0.1 m/s was sufficient to efficiently cool down the system; discharged at 5 C‐rate, the optimum inlet flow rate was 0.25 m/s. Simulations could accurately reproduce experimental results, allowing for an efficient design of the liquid‐cooled BTMS.     

Effects of reciprocating liquid flow battery thermal management system on thermal characteristics and uniformity of large lithium-ion battery pack

To investigate the thermal characteristics and uniformity of a lithium-ion battery (LIB) pack, a second-order Thevenin circuit model of single LIB was modeled and validated experimentally. A battery thermal management system (BTMS) with reciprocating liquid flow was established based on the validated equivalent circuit model. The effects of the reciprocation period, battery module coolant flow rate and ambient temperature on the temperature and the temperature imbalance of batteries were studied. The results illustrate that the temperature difference can be effectively reduced by 3°C when the reciprocating period is 590 seconds. The reciprocating coolant flow rate is 11.5% and 33.3% that of the unidirectional flow BTMS for cooling and heating when same thermal effects are to be achieved. Under the same ambient temperature condition, the maximum temperature and average temperature difference can be reduced by 1.67°C and 3.77°C, respectively, at best for the battery module investigated with a reciprocating liquid-flow cooling system. The average temperature difference and heating power consumption could be reduced by 1.2°C and 14 kJ for reciprocating liquid flow heating system with period of 295 seconds when compared with unidirectional flow. As a result, the thermal characteristics and temperature uniformity can be effectively improved, and the parasitic power consumption can be significantly reduced through adoption of a reciprocating liquid flow BTMS.     

Novel investigation strategy for mini-channel liquid-cooled battery thermal management system

Many researchers have focused on liquid-cooled devices with simple structure and high efficiency, which promoted the gradual development of the mini-channel liquid-cooled plate battery thermal management system (BTMS), due to the advancement of liquid cooling technology. This paper has proposed an electrochemical-thermal coupling model to numerically predict the thermal behavior of the battery pack in different parameters of mini-channel cold plates and optimize the parameter combinations. The effects of cooling plate width, mini-channel interval, and inlet mass flow rate on the heat dissipation performance of the system were analyzed at a constant C-rate to provide a reliable experimental basis for the optimization model. Results indicate that increasing the cold plate width and the inlet mass flow rate reduce the temperature and temperature gradients. In addition, the minimum temperature difference is obtained at the mini-channel interval of 6 mm. The optimum cooling plate width (90 mm), mini-channel interval (4 mm), and inlet mass flow rate (80 g/s) are determined using the orthogonal test, analysis of variance, and comprehensive analysis of multi-index results. The addition of an auxiliary cooling system based on the optimized combination further reduces the maximum temperature and temperature difference of the battery pack by 4.9% and 9.2%, respectively. The developed strategy and methods can further improve the performance of the BTMS and provide a reference for the development of a compact battery pack at high discharge rates for engineering applications.     

锂离子电池热管理和安全性研究

温度是影响锂离子电池性能、寿命和安全性的重要因素,电池热管理系统能使电池的工作温度维持在适宜范围,保障电池安全、高效和长寿命使用。因此,电池热管理系统对动力和储能设备在不同工况和环境下的运行至关重要。本文介绍了锂离子电池热模型的发展和应用,对热管理和安全性的研究进行了归纳;总结了本课题组的相关工作进展;在此基础上,指出了锂离子电池热管理和安全性进一步的研究方向。     

Numerical modeling and experimental investigation of a prismatic battery subjected to water cooling

In this paper, a numerical model using ANSYS Fluent for a minichannel cold plate is developed for water-cooled LiFePO₄ battery. The temperature and velocity distributions are investigated using experimental and computational approach at different C-rates and boundary conditions (BCs). In this regard, a battery thermal management system (BTMS) with water cooling is designed and developed for a pouch-type LiFePO₄ battery using dual cold plates placed one on top and the other at the bottom of a battery. For these tasks, the battery is discharged at high discharge rates of 3C (60?A) and 4C (80?A) and with various BCs of 5°C, 15°C, and 25°C with water cooling in order to provide quantitative data regarding the thermal behavior of lithium-ion batteries. Computationally, a high-fidelity computational fluid dynamics (CFD) model was also developed for a minichannel cold plate, and the simulated data are then validated with the experimental data for temperature profiles. The present results show that increased discharge rates (between 3C and 4C) and increased operating temperature or bath temperature (between 5°C, 15°C, and 25°C) result in increased temperature at cold plates as experimentally measured. Furthermore, the sensors nearest the electrodes (anode and cathode) measured the higher temperatures than the sensors located at the center of the battery surface.     

Heat dissipation analysis of different flow path for parallel liquid cooling battery thermal management system

As the main form of energy storage for new energy automobile, the performance of lithium-ion battery directly restricts the power, economy, and safety of new energy automobile. The heat-related problem of the battery is a key factor in determining its performance, safety, longevity, and cost. In this paper, parallel liquid cooling battery thermal management system with different flow path is designed through changing the position of the coolant inlet and outlet, and the influence of flow path on heat dissipation performance of battery thermal management system is studied. The results and analysis show that when the inlet and the outlet are located in the middle of the first collecting main and the second collecting main, respectively; system can achieve best heat dissipation performance, the highest temperature decrease by 0.49°C, while the maximum temperature difference of system decreases by 0.52°C compared with typical Z-type BTMS under the discharge rate of 1 C. Then an optimization strategy is put forward to improve cooling efficiency compared with single-inlet and single-outlet symmetrical liquid cooling BTMS; the highest temperature of three-inlet and three-outlet is 27.98°C while the maximum temperature difference of three-inlet and three-outlet is 2.69°C, decrease by 0.7 and 0.67°C, respectively.     

A comprehensive investigation on thermal management of large‐capacity pouch cell using micro heat pipe array

A proper and effective battery thermal management system (BTMS) is critical for large‐capacity pouch cells to guarantee a suitable operating temperature and temperature difference. Hence, in this paper, a micro heat pipe array (MHPA) is utilized to build the thermal management system for large‐capacity pouch cells. In order to study the property of BTMS in depth, experimental and numerical investigation are carried out by considering the C‐rate, working medium, air velocity and duty. The experimental results present that the T_max can be maintained below 43.7°C and the ΔT is below 4.9°C at the discharge rate of 3C in the battery module with MHPA‐liquid. Moreover, the T_max of the battery module with MHPA‐liquid falls as the air velocity increases. The simulation results show that the variation and distribution of temperature matched well with experimental results. It demonstrates that the MHPA‐based BTMS is viable and effective for large‐capacity pouch cell battery, even at high C‐rate and cycle duty.     

Experimental study on thermal performance of a pumped two-phase battery thermal management system

Battery thermal management system (BTMS) is of great significance to keep battery of new energy vehicle (NEV) within favorable thermal state, which attracts extensively attention from researchers and automobile manufacturers. As one BTMS scheme, pumped two-phase system displays excellent cooling capacity owing to large amount of latent heat usage, while there is limited research efforts focusing on the feasibility of the BTMS scheme. This paper experimentally investigates thermal performance of a pumped two-phase BTMS heated by a dummy battery with relative high heat fluxes. The effects of heat fluxes, flow rates and cold source temperatures on thermal performance have been studied and conclusions have been drawn accordingly. The results show that the thermal performance of the system is generally enhanced with the increase of the refrigerant flow rates. When the heat flux and cold source temperature are 0.11 W/cm² and 10°C, respectively, t_avg and △t_max are decreased by 3.4°C and 0.5°C, respectively, when the refrigerant flow rate is increased from 0.20 to 1.67 L/min. Meanwhile, heat transfer coefficient is also improved with an increase of the flow rates, while the enhancements become less obvious under high heat flux. In addition, the t_avg and △t_max of cold plate surface are increased when the heat flux is elevated, while the t_avg at the low flow rate is increased slightly. However, the increase of △t_max is more obvious at the low flow rate, compared to that at high flow rate. When the heat flux is increased from 0.11 to 0.60 W/cm², t_avg is increased by 3.8°C under the flow rate of 0.2 L/min, while that at the flow rate of 1.67 L/min is almost doubled. Meanwhile, the heat transfer coefficient is increased monotonously at the low flow rate, while that at the high flow rate is first decreased and then increased. Besides, lower surface temperatures can be obtained with low cold source temperatures. However, cold source temperatures affect temperature uniformity less.     

Thermal management of lithium-ion batteries using phase change materials

良好的热管理系统是电池安全及高效使用的保证,电池的热管理需要确保电池温度在安全温度范围以及电池组内最大温差不超过5 ℃.传统的热管理方式,如空气冷却,不仅需要额外的动力输入,而且越来越不能满足高能量密度的新型锂离子电池的热管理需要.使用相变材料的电池热管理系统,利用相变材料的相变潜热吸收电池产生的热量,在不使用外界功耗的条件下,可以长时间保持电池的温度在适宜的范围内.通过与膨胀石墨,金属泡沫复合,相变材料的热导率可以大大提高,电池组内体系温度均匀性可以满足工作要求.而且,相变材料的形状不固定,可以使用在任意形状的电池上.被动式热管理是应用于电池热管理系统中最具前景的技术.     

流动风阻网格模型与热仿真设计方法优化动力电池模组结构的研究

风冷系统因结构简单、成本低等特点,在热管理系统中占据重要地位。目前常规的风冷热管理设计方法存在重复性工作多、设计时间长的缺点。本文提出空气流动风阻网格模型结合热力学模型仿真的设计方法,先采用空气流动风阻网格模型获得优化的电池结构,再采用热力学模型进行仿真求解,获得优化的电池模组的流场和温度场分布特性。仿真结果验证了优化结构的准确性。优化结果表明,“C”字形结构更有利于提升模组内单体电池冷却效果的一致性,并且优化后的“C”字形结构进一步提升了电池模组内单体电池温度场的一致性。此外,计算结果发现模组内空气流动方向为上进下出时可进一步降低模组内单体电池的最高温度,提升单体电池温度场的一致性。     

Experimental study of a direct evaporative cooling approach for Li-ion battery thermal management

A desirable operating temperature range and small temperature gradient is beneficial to the safety and longevity of lithium-ion (Li-ion) batteries, and battery thermal management systems (BTMSs) play a critical role in achieving the temperature control. Having the advantages of direct access and low viscosity, air is widely used as a cooling medium in BTMSs. In this paper, an air-based BTMS is modified by integrating a direct evaporative cooling (DEC) system, which helps reduce the inlet air temperature for enhanced heat dissipation. Experiments are carried out on 18650-type batteries and a 9-cell battery pack to study how relative humidity and air flow rate affect the DEC system. The maximum temperatures, temperature differences, and capacity fading of batteries are compared between three cooling conditions, which include the proposed DEC, air cooling, and natural convection cooling. In addition, a DEC tunnel that can produce reciprocating air flow is assembled to further reduce the maximum temperature and temperature difference inside the battery pack. It is demonstrated that the proposed DEC system can expand the usage of Li-ion batteries in more adverse and intensive operating conditions.     

An experimental investigation of liquid cooling scheduling for a battery module

The thermal safety of electric vehicle battery modules attracts public concern; controlling the severe temperature rise and ensuring uniform temperature distribution are essential to addressing this problem. In this research, a liquid cooling-based cooling structure equipped with minichannels is proposed to prevent a battery module's overheating. A novel cooling scheduling study is proposed to arrange the coolant flow rates at different cooling stages. The temperature rise, temperature difference, and energy consumption of all the cooling schedules are measured in experiments. Experimental findings indicate that appropriate cooling scheduling achieves the thermal objectives and reduces energy consumption through scheduling the coolant flow rate in the cooling process. A comprehensive cooling schedule selection is carried out to select the optimal cooling schedule with the highest cooling efficiency through evaluating both the thermal and energy consumption objective parameters under different discharging current rates (0.5C, 1C, and 1.5C). The optimal cooling schedule maintains the maximum temperature of the battery module within 26°C, 32°C, and 40°C under 0.5C, 1C, and 1.5C discharging current rates, respectively. Moreover, the temperature SD and the energy consumption of the liquid cooling-based battery pack can be controlled within 3.5°C and 40 J, respectively.     

Effect of electrode configuration on the thermal behavior of a lithium-polymer battery

A thermal modeling was performed to study the effect of the electrode configuration on the thermal behavior of a lithium-polymer battery. It was examined the effect of the configuration of the electrodes such as the aspect ratio of the electrodes and the placing of current collecting tabs as well as the discharge rates on the thermal behavior of the battery. The potential and current density distribution on the electrodes of a lithium-polymer battery were predicted as a function of discharge time by using the finite element method. Then, based on the results of the modeling of potential and current density distributions, the temperature distributions of the lithium-polymer battery were calculated. The temperature distributions from the modeling were in good agreement with those from the experimental measurement for the batteries with three different types of electrodes at the discharge rates of 1C, 3C, and 5C.     

Simplification strategy research on hard-cased Li-ion battery for thermal modeling

Numerical simulation is widely used in research and design of the battery thermal management system (BTMS). Battery cells are commonly homogenized to a block for module or pack level modeling. However, how the homogenization method affects results is not proven. This paper works on a hard-cased Li-ion battery to find a proper simplification method. First, a detailed three-dimensional thermal model (model A) is set up and validated by experimental data. Then, the other three models with different simplification strategies are proposed. They are model B (the cell is homogenized to a block), model C (the cell preserves only core region and housing case), and model D (based on model C, the thin insulation films are also considered). Take the results of model A as a reference, the calculation accuracy and efficiency are summarized. It is found that model B shows the best efficiency and is a proper choice for evaluation of temperature dynamics, while model D is more recommended when the internal temperature distribution of the battery is more concerned.     

Modelling the thermal behaviour of a lithium-ion battery during charge

A method for modelling the thermal behaviour of a lithium-ion battery (LIB) during charge is presented. The effect of charge conditions on the thermal behaviour is examined by means of the finite element method. A comparison of the experimental charge curves with the modelling results validates the two-dimensional modelling of the potential and current density distribution on the electrodes of an LIB as a function of charge time during constant-current charge followed by constant-voltage charge. The heat generation rates as a function of the charge time and the position on the electrodes are calculated to predict the temperature distributions of the LIB based on the modelling results for potential and current density distributions. The temperature distributions obtained from the modelling are in good agreement with the experimental measurements.     

Study on accelerated life test method for Zn-Ag reserve battery

本工作通过比较不同存储期锌银电池中AgO的热力学特性、容量特性,研究AgO热稳定性以有效评价该类电池满足或拓展存储期限的可行性。本工作提出从不同恒速升温条件下的DSC曲线峰温和峰温时的反应深度计算/确定AgO分解反应动力学因子E、A的方法。建立数学模型,估算不同温度条件下锌银电池贮存期限并计算不同存储期锌银电池容量年衰减率,与不同温度下加速升温容量衰减率进行比较,最终确定适用于锌银电池加速寿命试验方法。     

Numerical model of the passive thermal management system for high-power lithium ion battery by using porous metal foam saturated with phase change material

A two-dimensional transient model for a passive thermal management system was developed for commercial square lithium ion battery by using the phase change material (PCM) of paraffin saturated in metallic copper foam. This model combined the thermo-electrochemical model for the battery and a model that characterized the solid–liquid phase change of paraffin in copper foam. The thermo-electrochemical model was composed of species conservation, charge conservation, and energy balance equations. In the model of phase change in metal foam, the non-Darcy, natural convection of melted paraffin, and local thermal non-equilibrium effects were considered. The thermo-electrochemical performance of the battery and convective heat transfer behavior of the foam-PCM composite were investigated. The predicted results were in agreement with experimental data. Compared to the air convection and adiabatic modes, the thermal management by foam-PCM composite has dramatically reduced battery surface temperature to the allowable range at 1C and 3C discharge rates.     

Experimental Investigation on Composite Phase-Change Material (CPCM)-Based Substrate

Many high-power electronic devices such as high-power light-emitting diodes and aerial devices work intermittently. If some of the heat generated by the chips could be stored in the thermal storage medium during the working time and then be released to the ambient in the nonworking time, the heat dissipation load of the heat sinks could be diminished and a better thermal characteristic could be achieved. Inspired by this idea, we proposed a thermal storage substrate and investigated its thermal storage properties by experiment in this study. First, the composite phase-change material (CPCM) was prepared as the thermal storage medium. Second, the thermal and phase-transition properties of the CPCM were studied through differential scanning calorimeter tests. Third, the thermal conductivity of the CPCM was measured for the analysis of thermal performance. Afterward, the CPCM-based substrate was fabricated and several experiments were conducted to examine its thermal storage performance. The results showed that the thermal storage substrate could store the heat, as much as 55,773.80 J, which accounts for 32% of the heat generated by the heat source approximately. With so much heat stored in the CPCM, the temperature of the heat source went up much more slowly. To accelerate the heat conduction inside the CPCM, five aluminum pillars were added into the substrate. As a result, the temperature of the heat source and the substrate wall decreased by 3.5°C and 4.5°C, respectively.     

NCR18650A电池的充放电温度特性与管理

采用实验测试与数值仿真的方法对NCR18650A三元锂电池组在1 ~ 3 C放电和1.6 C充电过程的温升特性进行测试,同时验证所建立电池产热模型的准确性。结果显示,实验测试结果与电池产热模型仿真结果之间的相对误差在合理范围内,满足工程应用需求。电池组在自然冷却的情况下,仅在1 C放电状态下符合其最佳工作区间42.5 ~ 45.0℃的要求,3 C放电倍率下最高温度为89.4℃。提出并建立基于热电致冷主动热管理模型,将热电致冷组件设置在电池组上方,致冷功率为50 W时可有效控制电池组3 C放电过程的温度,在最佳工作区间实现电池单体温差小于5℃,抑制电池组的热失效并实现良好的均温性。     

Temperature characteristics of lithium iron phosphatepower batteries under overcharge

High-capacity LiFePO₄ batteries are widely used in public transportation in China. However, overcharge causes serious safety issues, and the nature of the process requires further research. This study investigates an overcharge-induced thermal runaway of 20 and 24 Ah LiFePO₄ batteries under different initial states of charge (SOC) and charging rates. Chemical reactions inside the battery are influenced by the capacity of the battery, that is, a higher capacity induces faster heating and a higher maximal surface temperature than the lower capacity under the same conditions. The temperature curve of low initial SOC battery at low chargingratedoes not change notably. Under other conditions, the thermal runaway exhibits two stages, an initial slow temperature increase (stage I) followed by a rapid temperature increase (stage II). The initial SOC and charging rate are relevant only for the rate of temperature increase in stage I, with little effect in stage II. The study on the temperature characteristics of overcharge-induced thermal runaway can promotethe safety research of LiFePO₄ power batteries.