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。     

Overview of research on thermal safety of lithium-ion batteries

随着锂离子电池在生活和工作中的普及,锂离子电池的安全事故逐年增加,锂离子电池的安全研究逐渐引起学术界的关注。研究锂离子电池的热安全性,可以有效分析锂离子电池发生起火和爆炸的内在原因,指导锂离子电池安全性研究的开展。本文介绍了锂离子电池工作过程中产热的来源和影响因素,以及锂离子电池热失控发生时的内部反应和反应对应的温度,并对电池热失控时的热特性参数进行了总结。     

Research on early warning system of lithium ion battery energy storage power station

研究锂离子电池储能电站消防预警技术对于储能系统的安全运行具有重要意义。本文通过对电池热失控及热扩散特征识别展开讨论,由于锂离子电池发生热失控时会伴随着可燃气体缓慢释放,如果能够提取电池热失控早期气体参数并对其进行研究分析,可以在此基础上建立电池系统的热失控预警机制。本文采用加热方式和过充方式诱发电池热失控气体提取试验,通过采气试验进行气体成分含量分析,确定了将一氧化碳和温度作为典型的侦测依据来实现锂电池热失控的早期预警。并将这种电池热失控早期预警判断应用到了储能电站消防预警系统中,同时结合多级预警及防护机制和安全联动策略做了深入研究,确定了锂离子电池储能电站消防预警系统的设计架构,从系统部件、联动通信、人员安全3个方面对系统设计做了简要说明,在保证快速有效的检测出电池热失控状态的同时快速联动消防设施,极大提高了储能系统运行的可靠性。     

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。     

锂电池储能电站防消一体化系统设计及控制策略

面向锂电池储能电站的安全需求,遵循“预防为主、防消结合”的原则,设计锂电池储能电站防消一体化系统,实现数据融合和智能诊断,建立早期预警、后期灭火防护的完整系统;参照实际储能预制舱结构,搭建储能预制舱试验环境,开展锂电池单体及模组热失控及灭火试验,结果表明：防消一体化系统控制策略通过安全预警、防护、消防系统的分级工作,实现了火灾早期预警以及后期灭火防护,最大程度降低了电池热失控带来的危害;以细水雾作为灭火介质能在短时间内熄灭磷酸铁锂电池火灾,并能有效防止电池复燃。     

Overcharge investigation of lithium-ion polymer batteries

The overcharge performances of lithium-ion polymer batteries (LIPB) have been studied by monitoring their temperature variation and analyzing the generated heat during overcharge. The critical concentration of lithium in the cathode material is determined for the thermal runaway of the battery. Solutions against the thermal runaway are proposed based on these results.     

Influence of coupling of overcharge state and short-term cycle on the mechanical integrity behavior of 18650 Li-ion batteries subject to lateral compression

The study on the mechanism of failure and thermal runaway of lithium-ion battery (LIB) induced by mechanical deformation has received considerable attention. LIBs connected in series are easily overcharged in practical applications. However, the influence of overcharging on the mechanical response of LIBs remains unclear. Thus, we investigated the lateral compression performance of cylindrical batteries before and after short-term cycles at various overcharge states. The onset of short circuits in compression tests for all the batteries before and after cycling at 4.2 and 4.3 V occurred at their modulus peaks, while that of the batteries after cycling at 4.4 and 4.5 V occurred at either the modulus fluctuation points or the first major modulus peaks. Thermal runaway accidents occurred on the batteries at all overcharge states after the short circuits were triggered. Moreover, thermal runaway would occur on the batteries charged at 4.2–4.4 V, when their anode tabs are located in the compression area. The thermal runaway risks of the test batteries would reach 100% when the voltages of these batteries exceeded 4.4 V. Results obtained by using a thermal camera revealed that the highest surface temperatures of all the batteries without thermal runaway were lower than 85 °C during the compression processes, whereas those of the batteries with thermal runaway were between 200 °C and 600 °C. Further analysis of the data indicated that the batteries before and after cycling at high overcharge voltages failed at minimal moduli and stresses, and this trend became obvious with the cycling of batteries.     

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.     

ARC experimental and data analysis for safety evaluation of Li-ion batteries

锂离子电池安全性能可以通过电池热失控过程的量热分析来进行定性和定量评估。电池在不同温度下的放热速率及累计放热量是衡量电池热稳定性的参数。动力电池的量热分析通过绝热加速量热仪进行。本文主要介绍加速量热仪的测试原理和方法、数据分析方法,并对电池安全程度的评估方法提出了建议。     

循环充放电条件下锂离子电池的温度模拟

锂离子电池在充放电过程中产生的热量主要为两部分,即因电化学反应而产生的可逆热和由极化产生的不可逆热。若电池内部温度达到82℃以上时,钴酸锂电池材料将发生热分解,引发一系列不可控化学反应,释放出大量的反应热。本论文在可逆热和不可逆热的基础上,耦合电池材料分解热,采用有限元技术,模拟锂离子电池在充放电过程中不同对流条件以及不同外界温度下电池内部温度的变化,为揭示锂离子电池热失控机制提供理论依据。     

Influence of cycling on the heat-release and thermal runaway of the lithium ion battery under adiabatic condition

随着锂离子电池能量、寿命的提升,对安全性需求也越来越高,温度对电池的寿命和安全有着重要影响。以钴酸锂/中间相碳微球体系电池为研究对象,采用加速量热仪研究了不同工作电流、不同循环老化周期电池的产热特性和热失控行为,电池的发热量随着充放电倍率的增加而增大。通过比较不同循环老化周期电池的产热速率,发现容量衰减速度与直流内阻、产热量之间存在很强的关联性。从热失控行为研究发现,自放热起始温度为105.4℃,随后发生连续自放热,直到温度达到149.7℃热失控起始温度,发生内短路,最终导致电池热失控。循环后电池的热失控过程中自放热和热失控起始温度稍有变化,热失控时间大大缩短。     

New low temperature electrolytes with thermal runaway inhibition for lithium-ion rechargeable batteries

This paper describes a low temperature electrolyte system for lithium-ion rechargeable batteries. The electrolyte exhibits high ionic conductivity, good electrochemical stability and no exothermic reaction in the presence of lithium metal. The system features a low lattice energy lithium salt in a specific mixture of carbonate solvents and a novel thermal runaway inhibitor.     

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.     

Recent progress on mechanism and detection of internal short circuit in lithium-ion batteries

锂离子电池内短路是锂离子电池热失控事故中最常见的诱因之一,也是机械滥用、电滥用、热滥用的共性环节,是潜在的安全威胁。本文从锂离子电池内短路安全问题出发,综述了内短路机理的研究进展,归纳了内短路替代实验方法,介绍了内短路演化过程,指出了内短路检测需在其发展初期和中期完成。进而,总结了多种内短路检测方法,最后,对内短路问题下一步研究进行了展望。     

Thermal explosion hazards of lithium-ion batteries in hermetic space

使用扩展容积加速度量热仪（extend volume accelerating rate calorimeter,EV-ARC）及耐压罐,开展了密闭空间中不同荷电状态（SOC）下18650型锂离子电池的热爆炸实验。实验发现,SOC=0%时电池不会发生热爆炸,而在其它工况下均发生了热爆炸;电池发生热爆炸时,电池表面最高温度、耐压罐内部最大压力都随着SOC的增加而增大。利用实验中电池发生热爆炸时的初始温度和最高温度,通过计算得到了不同SOC下电池发生热爆炸时的爆炸当量,当SOC=100%时,爆炸当量值最大,为5.45 gTNT,约是SOC=25%时的2.5倍,并在耐压罐中产生40.69 bar的峰值压力。锂离子电池在密闭中的热爆炸危险性随着电池SOC的增加而增大。     

Thermal runaway-preventing technologies for lithium-ion batteries

安全性是制约高比能、大容量锂离子电池规模应用的重要技术问题,热失控是导致电池发生爆炸、燃烧等不安全行为的根本原因。从电化学角度来看,在锂离子电池内部建立一种自激发热保护机制,切断危险温度下电池内部的离子或电子传输,关闭电池反应,是解决这一问题的有效途径。基于这一考虑,近年来人们提出了一系列新型热失控防范技术,包括正温度系数电极（即PTC电极）、热敏性微球修饰隔膜（或电极）、热聚合添加剂等。本文在简要介绍这些安全性技术的实现方式和工作原理之后,重点介绍了这一领域的最新研究进展。在此基础上,从实际应用需求出发,对其存在的问题及发展趋势进行了探讨。     

Energy-storage technologies and electricity generation

As the contribution of electricity generated from renewable sources (wind, wave and solar) grows, the inherent intermittency of supply from such generating technologies must be addressed by a step-change in energy storage. Furthermore, the continuously developing demands of contemporary applications require the design of versatile energy-storage/power supply systems offering wide ranges of power density and energy density. As no single energy-storage technology has this capability, systems will comprise combinations of technologies such as electrochemical supercapacitors, flow batteries, lithium-ion batteries, superconducting magnetic energy storage (SMES) and kinetic energy storage. The evolution of the electrochemical supercapacitor is largely dependent on the development of optimised electrode materials (tailored to the chosen electrolyte) and electrolytes. Similarly, the development of lithium-ion battery technology requires fundamental research in materials science aimed at delivering new electrodes and electrolytes. Lithium-ion technology has significant potential, and a step-change is required in order to promote the technology from the portable electronics market into high-duty applications. Flow-battery development is largely concerned with safety and operability. However, opportunities exist to improve electrode technology yielding larger power densities. The main barriers to overcome with regard to the development of SMES technology are those related to high-temperature superconductors in terms of their granular, anisotropic nature. Materials development is essential for the successful evolution of flywheel technology. Given the appropriate research effort, the key scientific advances required in order to successfully develop energy-storage technologies generally represent realistic goals that may be achieved by 2050.     

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。     

Research of leaked toxics from Li-ion battery electrical heat triggering thermal runaway

为探究锂离子电池电热触发热失控过程,本工作在研究和建立电热触发锂离子电池热失控方法的基础上,对不同荷电状态下18650锂离子电池进行电热触发热失控,分析了电热触发18650锂离子电池热失控现象,对热失控过程中泄露的气体进行采集与分析。研究结果表明,电热方法可以触发18650锂离子的热失控,该热失控过程中会产生有毒气体,同时伴随浓烟和高温,防护不当将对人体和环境造成伤害。     

Thermal runaway propagation mitigation of lithium ion battery by epoxy resin board

动力电池热失控扩展阻隔是抑制大规模电池火灾的重要途径。本文采用环氧树脂板（ERB）阻隔锂离子电池的热失控扩展，分析不同厚度ERB对串联及并联模组的热失控阻隔作用。结果表明，ERB可降低热失控电池模组的最高温度，减轻电池热失控剧烈程度，避免喷射火焰的产生；对于并联的电池模组，采用2 mmERB的锂电池模组的电池间热失控扩展平均时间间隔为198 s，为无ERB时的2.29倍，采用4 mm ERB时平均时间间隔延长至无ERB时的5.57倍；对于串联的电池模组，采用2 mm ERB时电池热失控扩展平均时间间隔延长至无ERB锂电池模组的2.09倍，采用4 mm ERB时可完全阻止热失控扩展；研究发现并联的电池模组相对于串联模组更容易扩展,其原因为并联模组单个电池热失控时会形成电回路并产生焦耳热。