Recent progress on thermal runaway propagation of lithium-ion battery

简述了电动汽车锂离子动力电池热失控蔓延机理、建模与抑制技术的最新研究进展。为了满足汽车高能量的要求,需要动力电池进行串并联成组来提供动力。电池组成组安全问题成为电动汽车大规模应用的重要技术问题。电池组中的某一个电池单体发生热失控后产生大量热,导致周围电池单体受热产生热失控。因而,电池组成组安全问题的重要关注点是电池组内的热失控蔓延问题。本文对锂离子电池热失控蔓延问题的国内外研究进展进行了综述,分析了对于不同种类锂离子动力电池影响其热失控蔓延特性的主要因素。总结了文献中的热失控蔓延建模方法,并指出了已有方法的不足。从电池系统热安全管理的角度,阐述并分析了热失控蔓延防控技术的研究成果与方向。最后对锂离子电池热失控蔓延研究进行了展望。     

An alternative cooling system to enhance the safety of Li-ion battery packs

A passive thermal management system is evaluated for high-power Li-ion packs under stressful or abusive conditions, and compared with a purely air-cooling mode under normal and abuse conditions. A compact and properly designed passive thermal management system utilizing phase change material (PCM) provides faster heat dissipation than active cooling during high pulse power discharges while preserving sufficiently uniform cell temperature to ensure the desirable cycle life for the pack. This study investigates how passive cooling with PCM contributes to preventing the propagation of thermal runaway in a single cell or adjacent cells due to a cell catastrophic failure. Its effectiveness is compared with that of active cooling by forced air flow or natural convection using the same compact module and pack configuration corresponding to the PCM matrix technology. The effects of nickel tabs and spacing between the cells were also studied.     

A review on thermal management techniques for lithium-ion battery

随着新能源汽车的广泛使用,动力锂离子电池的热安全性问题日益突出。本文以Bernardi生热机理为基础,耦合不同物理量,分别从电化学-热耦合模型、电-热耦合模型和热滥用模型来介绍单体电池的热特性。由于电池能量密度的增加与行驶工况复杂程度的提高,动力锂离子电池容易发生热量堆积,甚至造成热失控,对此,文中梳理了商用动力电池包的常用冷却方式。最后,根据对影响电池模组安全性的热失控蔓延机理及实测结果,介绍了阻断单体及基本模块热失控传播的有效方法。     

基于COMSOL的锂离子电池热失控仿真与防控

动力电池是新能源汽车关键部件,为进一步探究其热失控机理及影响因素,总结热失控发展过程,利用COMSOL软件构建锂离子电池单体模型,结合仿真实验结果详细分析其影响因素,并提出一款利用隔热罩、隔热盖板、隔热底座和可滑动扩容盒延缓热失控效果的可延缓热失控的汽车电池包。研究结果表明：热失控过程大致分为加热阶段、喷射和燃烧阶段、熄灭阶段,受4种副反应产热影响;在超过445.08 K的高温环境下,长时间工作的锂离子电池易发生热失控,失控热源关键在正极活性材料与电解液分解反应;当电池实际温度超过500 K时,温度若无法及时控制将导致火灾事故发生;同时,对流传热系数越高,电池温度变化越快;初始温度越高,热失控可能性越大。     

Analysis of Heat Dissipation Performance between a Horizontal and Longitudinal Battery Pack Based on Forced Air Cooling

A battery pack is the main energy storage element, and directly affects the performance of an electric vehicle. Battery thermal management system research and its development for a modern electric vehicle is required. This paper selects the forced air cooling of battery pack as the research object, and uses simulation methods to research the heat dissipation performance with different structures of battery packs. The results indicate that according to the four types of transient state conditions, the rising temperature of both battery packs are significantly higher than the temperature difference, the maximum temperature rise and temperature difference of a horizontal battery pack are lower than a longitudinal battery pack. When an electric vehicle begins to decrease speed, the curves of temperature rising and temperature difference increase. This shows the internal heat is continuously rising, so even in a electric vehicle beginning to decrease speed, the fan must work. The reference basis for choosing battery pack type and an analysis of heat flow field characteristics, including fan run‐time control, are offered.     

Numerical investigation of thermal runaway propagation in a Li-ion battery module using the heat pipe cooling system

It is a promising cooling strategy to use the heat pipe for the Li-ion battery module, which can maintain the temperature of the battery module properly and prevent high temperature, triggering the thermal runaway among adjacent batteries. In this study, the thermal runaway model is simulated through the internal short circuit, which couples with Volume of Fluid (VOF) model of the heat pipe cooling and solves in ANSYS FLUENT to realize the heat and mass transfer between batteries and heat pipes. A user-defined function (UDF) code including mass source and energy source is used to calculate the heat and mass transfer in VOF model during the thermal runaway process. Numerical simulations are adopted to probe thermal runaway processes of a single battery under different operation conditions and the thermal runaway propagation from a battery to adjacent batteries. It is concluded that the heat pipe cooling system cannot prevent the thermal runaway of a single battery, but it can prevent the thermal runaway propagation from a battery to adjacent batteries.     

Numerical study on thermal behavior and a liquid cooling strategy for lithium-ion battery

Investigation on the thermal behavior of the lithium-ion battery which includes the temperature response, heat contribution and generation, is of vital importance for their performance and safety. In this study, an electrochemical-thermal cycling model is presented for a 4 Ah 21700 type cylindrical single cell and 3× 3 battery pack and the model is validated by experiment on a single cell. Thermal behavior on a single cell is first analyzed, the results show that the heat generated in the charge is smaller than the discharge, and the polarization heat contributes the most to total heat, especially under higher rate. It can also be concluded from the battery pack that the temperature of the cell inside the battery pack is significantly greater than the external battery, while the temperature difference exists the opposite regular due to the worst heat dissipation of the central cell. Finally, after taking the enhanced liquid cooling strategy, the maximum temperature is 320.6 K that is reduced by 9.38%, and the maximum temperature difference is 4.9 K which is reduced by 69.6% at 2C, meeting the requirements of battery thermal management system.     

Experimental and numerical investigation of heat transfer in Li‐ion battery pack of a hoverboard

Li‐ion cells are used for energy storage and conversion in electric vehicles and a variety of consumer devices such as hoverboards. Performance and safety of such devices are severely affected by overheating of Li‐ion cells in aggressive operating conditions. Multiple recent fires and accidents in hoverboards are known to have originated in the battery pack of the hoverboard. While thermal analysis and measurements have been carried out extensively on large battery packs for electric vehicles, there is relatively lesser research on smaller devices such as hoverboards, where the extremely limited thermal management design space and the critical importance of user safety result in severe thermal management challenges. This paper presents experimental measurements and numerical analysis of a novel approach for thermal management of the battery pack of a hoverboard. Measurements indicate that temperature rise in cells in the pack can be as large as 30°C at 4C discharge rate, which, although unlikely to be a standard discharge rate, may result from a malfunction or accident. A novel thermal management approach is investigated, wherein careful utilization of air flow generated by hoverboard motion is shown to result in significant temperature reduction. Measurements also indicate the key role of the metal housing around the battery pack in thermal management. Measurements are found to be in good agreement with finite element simulations, which indicate that the battery pack can be cooled as effectively in presence of a perforated metal casing as without the casing at all. Experimental data and simulation model presented here offer critical insights into the design of hoverboard thermal management and may result in safer, high performance hoverboard battery packs.     

A case study of Japan airlines B-787 battery fire

日本航空公司的JA829J次航班的蓄电池燃烧事故,是一起典型的由内短路引发的锂离子蓄电池热失控在电池模块内部的单体电池之间相互传递从而导致连锁反应的安全事故.本文通过对这起热失控引发的安全事故进行案例分析来揭示热失控的典型特征以及关键性的影响因素,针对这起事故暴露出的问题提出改善大型锂离子动力蓄电池模块安全性的相关建议.     

Exploring the heat transfer performance of nanofluid as a coolant for power battery pack

Nanofluids with high thermal conductivity coefficient are introduced to the thermal management system of power battery packs for electric vehicles and hybrid electric vehicles. Two typical cooling structures of cylindrical and square battery packs are described, and their flow models are established. By similarity transformations, the nonlinear system of partial differential equations is reduced and then solved numerically by the shooting method. The heat transfer properties of three types of nanofluids, that is, CuO‐EG, Al₂O₃‐EG, TiO₂‐EG, are analyzed in detail. It is found that CuO‐EG nanofluid is the best coolant for the cylindrical battery pack, whereas Al₂O₃‐EG nanofluid is the best choice for square battery pack cooling.     

The forced air cooling heat dissipation performance of different battery pack bottom duct

Due to the requirement of the battery for the thermal management system, based on the coupling relationship between the velocity field and the thermal flow field of the field synergy principle, the flow paths of the forced air cooling system for different battery packs were analyzed. First, the thermodynamic parameters of the battery were collected through experiments and verified by simulation. Secondly, based on the collected thermodynamic parameters of the battery, the heat generation model of the battery, the heat conduction model of the gas, and the coupled heat dissipation model of the battery and air were established. Determine the boundary conditions, calculation methods and evaluation indicators required for simulation; Finally, based on four different driving conditions, the forced air cooling performance of the double “U” shape duct and double “1” type duct is simulated. Through the analysis of the results, the dual “U” air ducts have a more heat dissipation effect on the battery pack than the double “1” shape duct. The results conform to the definition of the field synergy principle for the coupling relationship between the velocity field and the heat flow field. Then research provide references for the design of battery packs and matching of cooling systems.     

Towards impedance-based temperature estimation for Li-ion battery packs

In order to meet the required power and energy demand of battery-powered applications, battery packs are constructed from a multitude of battery cells. For safety and control purposes, an accurate estimate of the temperature of each battery cell is of vital importance. Using electrochemical impedance spectroscopy (EIS), the battery temperature can be inferred from the impedance. However, performing EIS measurements simultaneously at the same frequency on each cell in a battery pack introduces crosstalk interference in surrounding cells, which may cause EIS measurements in battery packs to be inaccurate. Also, currents flowing through the pack interfere with impedance measurements on the cell level. In this paper, we propose, analyse, and validate a method for estimating the battery temperature in a battery pack in the presence of these disturbances. First, we extend an existing and effective estimation framework for impedance-based temperature estimation towards estimating the temperature of each cell in a pack in the presence of crosstalk and (dis)charge currents. Second, the proposed method is analysed and validated on a two-cell battery pack, which is the first step towards development of this method for a full-size battery pack. Monte Carlo simulations are used to find suitable measurement settings that yield small estimation errors and it is demonstrated experimentally that, over a range of temperatures, the method yields an accuracy of ±1°C in terms of bias, in the presence of both disturbances.     

Heat Generation and Thermal Transport in Lithium-Ion Batteries: A Scale-Bridging Perspective

ABSTRACT

Lithium-ion batteries (LIBs) are complex, heterogeneous systems with coupled electrochemical and thermal phenomena that lead to elevated temperatures, which, in turn, limit safety, reliability, and performance. Despite years of research, there are still open questions about the electrochemical-thermal phenomena within battery cells. This article highlights recent advances in thermal characterization and modeling of LIBs with an emphasis on the multi-scale aspect of battery systems: from the microscale electrode components to the macroscale battery packs. Both heat generation and thermal properties (thermal conductivity and specific heat capacity) are impacted by battery capacity, charge/discharge rate, ambient conditions, and the underlying microstructure. Understanding thermal phenomena and designing batteries to prevent thermal runaway requires multiscale efforts from the microstructure of the electrodes to the overall system behavior. Experimental efforts have focused on both property and performance characterization, as well as development of new battery chemistries for improved performance and new designs for improved thermal management. Past numerical modeling work ranges from computationally efficient lumped approaches to high fidelity microstructural finite element models. Ultimately, coupled electrochemical-thermal investigations (both numerical and experimental) are required to further improve the performance and reliability of batteries, and to prevent thermal runaway. This perspective article provides insight into directions to improve these approaches with the goal of informing design of batteries with improved performance, safety, and reliability.     

Research on the heat dissipation performance of lithium‐ion cell with different operating conditions

This paper aims to research the thermal power of lithium‐ion cell with different operating conditions. A 55‐Ah lithium‐ion cell is selected as the research object. Experiment and simulation are chosen as the methods to research the temperature distribution and thermal power of the cell under different conditions. Combining with the thermal power of cells, this paper also researches the heat dissipation performance of battery pack under different operation conditions. The results indicated that average thermal power of a 55‐Ah lithium‐ion cell decreases along with the increase of ambient temperature and the decrease of state of charge and charge and discharge rates. The results achieved through simulation and experiment are consistent, so simulation could be used to research the temperature distribution of cell during charge and discharge. As considering the longitudinal battery pack with steady analysis, high temperature area is in the centre, and the temperature of air inlet is relatively low. The airflow mostly passes the top of battery pack but not through both sides. As considering the longitudinal battery pack with transient analysis, the temperature rise of battery pack is evidently higher than the inner temperature difference by studying three operating conditions (sustained deceleration, sustained acceleration and pulsed discharge). The curves of temperature rise and inner temperature difference rise along with sustained acceleration of the electric vehicle; therefore, even if the electric vehicle begins to decelerate, the fan must still work until the temperature of battery pack decreases. Then, the references are given for researching thermal characteristic during charge and discharge of the cell and the heat dissipation analysis of battery pack. Copyright © 2017 John Wiley & Sons, Ltd.     

Thermal runaway fire characteristics of lithium ion batteries with high specific energy NCM811

通过NCM811高比能锂离子电池在低氧环境、电滥用、热滥用和机械滥用工况下热失控实验研究,获取该电池的热失控特性及关键参数,为进一步的热失控早期预警和火灾扑救研究提供了技术支持。     

Research on heat dissipation performance and flow characteristics of air‐cooled battery pack

With the depletion of fossil fuels and the aggravation of environmental pollution, the research and development speed of electric vehicles has been accelerating, and the thermal management of battery pack has become increasingly important. This paper selects the electric vehicle battery pack with natural air cooling as the study subject, conducts simulation analysis of the heat dissipation performance of battery packs with and without vents. Then this paper researches on the influence of internal flow field and external flow field. Field synergy principle is used to analyze the effect of velocity field and temperature field amplitude. The results show the following: it is found that the maximum temperature rise and the internal maximum temperature difference of the battery pack with vents are reduced by about 23.1% and 19.9%, raising speed value can improve the heat dissipation performance, and raising temperature value can decrease the heat dissipation performance. Reasonable design of the vents can make the inner and outer flow field work synergistically to achieve the best cooling effect. Then the reference basis for the air cooling heat dissipation performance analysis of electric vehicle, battery pack structure arrangement, and air‐inlet and air‐outlet pattern choosing are offered.     

Thermal management of lithium‐ion batteries for electric vehicles

Thermal issues associated with electric vehicle battery packs can significantly affect performance and life cycle. Fundamental heat transfer principles and performance characteristics of commercial lithium‐ion battery are used to predict the temperature distributions in a typical battery pack under a range of discharge conditions. Various cooling strategies are implemented to examine the relationship between battery thermal behavior and design parameters. By studying the effect of cooling conditions and pack configuration on battery temperature, information is obtained as to how to maintain operating temperature by designing proper battery configuration and choosing proper cooling systems. It was found that a cooling strategy based on distributed forced convection is an efficient, cost‐effective method which can provide uniform temperature and voltage distributions within the battery pack at various discharge rates. Copyright © 2012 John Wiley & Sons, Ltd.     

Heat dissipation analysis and optimization of the pure electric bus lithium-ion battery pack based on CFD

针对某纯电动客车电池箱散热效果不佳的问题,本文基于CFD技术以该车的电池箱散热系统为研究对象,建立了估算锂离子电池生热速率数学模型,采用三维软件UG建立电池箱的几何模型,并利用软件Star-ccm+对该模型的速度场和温度场进行仿真和分析。通过添加导流板等措施,对电池箱的结构进行了优化改进,并进行了正交仿真实验,确定了电池箱导流散热的最优方案,结果表明,导流板能够降低电池箱内单体电池的最高温度,使电池组温度分布更加均匀。     

Machine learning approach for solving inconsistency problems of Li-ion batteries during the manufacturing stage

The inconsistency in the mass production of lithium-ion battery (LIB) packs stem from the inconsistency in the capacity, voltage and internal resistance of single batteries that compose packs. The inconsistency issue of these battery packs can greatly reduce the output performance of a large power pack. This paper proposed the machine learning approach based on self-organization mapping (SOM) neural networks for establishing the consistency of LIBs. This method comprehensively compares and analyzes the real-LIB parameters (internal resistance, capacity and voltage) data obtained during charging and discharging to form the clusters of similar performing LIBs. Experimental result validated the clustering analysis and it indicates that the performance of clustered battery pack typically precedes than that of original. The capacity of clustered battery pack increased 1.9% compared with brand-new pack. The temperature distribution of the battery pack assembled after screening is consistent. The peak temperature is 4°-5° lower than the ordinary battery, and the temperature fluctuation is reduced by 2.6°. In addition, the application of cluster analysis is expanded and some key research directions are pointed out.     

锂离子电池热安全防控技术的研究进展

在众多储能技术中,锂离子电池以其能量密度大、能量转换效率高、循环寿命长、应用范围广、对环境友好等优势,成为当前最具应用前景的电力系统电池储能技术之一。但现有锂离子电池体系无法从本质上保证其安全性,在使用过程中具有发生热失控乃至燃烧、爆炸等安全事故的风险。本文就锂离子电池的热失控机理、电池本体的安全设计、安全预警、电池组热失控起火的阻燃装置以及消防安全的研究进展进行了综述。