典型锂离子电池和电解液燃烧特性及航空运输环境对其影响机制研究

发布时间：2018-01-15 21:30

本文关键词：典型锂离子电池和电解液燃烧特性及航空运输环境对其影响机制研究　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：随着锂离子电池的广泛应用和我国航空业的高速发展,航空运输锂离子电池数量日趋增多。锂离子电池作为第9类危险品,其本身存在易燃易爆风险,特殊的航空运输环境(如高温、挤压和碰撞等)使其危险性更加暴露,而目前缺乏与之相对应的风险控制技术,从而导致航空运输锂离子电池火灾或爆炸事故时有发生,带来了极大的财产损失和人员伤亡,为确保锂离子电池的安全运输,需对诱发锂离子电池的不安全因素进行分析,揭示其内在影响机制,并采取针对性的措施来预防锂离子电池火灾事故的发生。本文旨在降低锂离子电池航空运输风险,开展典型锂离子电池和电解液燃烧特性及航空运输环境对其影响机制研究,主要的研究内容如下:对不同辐射热流下电解液池火的燃烧特性参量进行了实验测试与理论分析,同时使用TG-FTIR对高温环境下电解液的热解机理进行了探究。与氢化物不同,电解液池火燃烧行为特征与含有的有机溶剂相对蒸发性有关,线状碳酸酯主控燃烧的早期阶段,而环状碳酸酯主控后期阶段;与氢化物相比,电解液的高汽化热和低燃烧热导致其相对低的热释放速率(Heat Release Rate,HRR)和质量损失速率(MassLossRate,MLR);单位面积的HRR与辐射热流成正相关,与油盘直径成负相关,建立了耦合辐射热流和油盘直径的电解液HRR预测模型;修正Heskestad火焰高度预测模型,建立了耦合有效燃烧热,油盘直径和空气与燃料当量比的电解液火焰高度预测模型;CO和CO2的释放量与辐射热流和油盘直径均成正相关,而CO和CO2的摩尔浓度比与两者无关;电解液热解主要分两步,第一步主要是有机溶剂的蒸发和LiPF6的水解反应,第二步主要是LiPF6热分解(在190℃左右)产生强路易斯酸PF5和HF,PF5催化EC发生开环聚合反应,同时PF5也与EMC和DMC发生反应产生C02、C2H5F和毒性HF等气体。对不同压力下电解液池火的火羽流特征参量进行了实验测试与理论分析,同时验证了压力修正后的火羽流理论模型对电解液池火的适用性。MLR与压力呈正指数关系,但由于电解液中有机溶剂的碳含量少,其指数系数低于普通氢化物;通过拟合m"D和P2D3验证了压力模型对预测对流主导的电解液池火的MLR是适用的;平均火焰高度随压力的降低而升高,通过引入压力项,修正无量纲HRR,拟合L/D和m"2/P∞2D,验证了修正后的Heskestad火焰高度修正公式对电解液池火是适用的;火羽流温度随压力的降低而升高,通过引入压力项,修正特征长度,拟合ln(△T0/T∞)与ln((z-z0)(P/Q)2/5),验证了修改后的Heskestad火羽流温升公式对电解液池火是适用的;拟合火羽流温升与压力修正后的特征长度,发现电解液池火火羽流分为持续火焰区和浮力羽流区两个区域,不符合McMaffrey模型的三区域。基于锥形量热仪对不同荷电状态(State of Charge,SOC)和辐射热流下的18650型锂离子电池燃烧特性参数进行了研究,并揭示了 SOC和辐射热流对燃烧特性参数的内在影响机制。基于氧耗法和质量损失速率法得出的HRR曲线趋势一致,对比两曲线得出消耗锂离子电池内部材料分解释放的氧气所释放的能量和内部短路所释放的焦耳热占总能量的比例小于13%,同时锥形量热仪和前人利用ARC测得的锂电池表面温度数据基本一致也证明了锥形量热仪能够用于测试锂离子电池的燃烧特性;高于50%SOC,HRR曲线均有前小后大的两峰值,且随SOC的增加,HRR峰值和表面最高温度增加,点燃和爆炸时间缩短,放气温度和热失控开始温度降低,CO和CO2增多;低于50%SOC,火灾危险性明显降低,HRR曲线只有一小峰值,发生微弱的燃烧,表面温度低,点燃时间长,CO和CO2少,同时SOC低于50%的锂离子电池的闪燃危险性明显低于高于50%,因此建议将运输锂离子电池的SOC控制在50%以下;随辐射热流的增大,HRR峰值和表面最高温升升高,点燃和爆炸时间缩短,放气温度和热失控开始温度降低,火灾危险性增大;拟合实验数据,得出锂离子电池的点燃时间预测公式和临界点燃热流。对不同压力下锂离子电池燃烧特性参量进行了实验测试和定量分析,并揭示了压力对燃烧特性参量的内在影响机制。燃烧强度随压力的降低而降低,压力降至30kPa燃烧未发生,即降压能抑制明火的产生;MLR与压力呈正相关;对比不同压力下的表面温升得出压力对表面温度超过155℃的热解反应速率有明显的影响,压力大于50kPa,表面最大温度随压力的0.4次方而减小,而小于50kPa,与压力呈线性变化;放气和点燃以及有效控火时间均随压力的降低而增长,压力降至50kPa以下,火灾危险性显著降低。
[Abstract]:With the rapid development of China's aviation industry and the wide application of lithium ion batteries, the number of air transport of lithium ion batteries is increasing. The lithium ion battery as the ninth kind of dangerous goods, which is inflammable and explosive risk, special air transport environment (such as high temperature, extrusion and collision etc.) the risk of more exposure, and the current the lack of risk control technology and the corresponding, resulting in air transport of lithium ion battery fire or explosion accidents have occurred, bring great property loss and casualties, in order to ensure the safe transport of lithium ion batteries, lithium ion batteries are needed to induce the safety factors, to reveal the internal mechanism and influence. Take appropriate measures to prevent the occurrence of fire accidents of lithium ion batteries. This thesis aims to reduce the risk of air transport of lithium ion battery, developing characteristic and typical lithium ion battery electrolyte and combustion Research on the influence mechanism of air transport on the environment, the main research contents are as follows: the combustion characteristic parameters of different heat flux under the electrolyte pool fire were experiment and theoretical analyses, while using TG-FTIR under the environment of high temperature pyrolysis mechanism of electrolyte were studied. With different organic solvent electrolyte hydride, pool fire behavior and contain the relative evaporation on early stage linear carbonate master combustion, and cyclic carbonate master late stage; compared with hydride, high heat of vaporization and electrolyte of low combustion heat due to the relatively low heat release rate (Heat Release, Rate, HRR) and mass loss rate (MassLossRate, MLR) unit; the area of HRR was positively correlated with heat radiation, negative correlation with the diameter of oil pan, a coupling electrolyte HRR radiation heat flux and pan diameter prediction model; modified Heskestad high flame The prediction model established by coupling the effective heat of combustion, the predictive model of oil pan and the diameter of the air and fuel equivalence ratio and flame electrolyte; CO CO2 emission and radiation flux and pan diameter were positively correlated, while CO and CO2 molar ratio and two independent; the electrolyte is mainly divided into two step pyrolysis, the first step is mainly evaporation and LiPF6 hydrolysis reaction of organic solvent, the second step is the thermal decomposition of LiPF6 (at about 190 DEG C) Jon Luis acid PF5 and HF PF5, EC catalyzed ring opening polymerization, and PF5 with EMC and DMC reacted to produce C02, C2H5F and HF. The toxic gas under different pressure the electrolyte pool fire plume characteristic parameters of experiment and theoretical analyses, and to verify the applicability of.MLR and pressure positive exponential relationship between the modified pressure plume theory model for the electrolyte pool fire, but because of the electrolyte The carbon content of organic solvents, the exponential coefficient is lower than that of the ordinary hydride; by fitting m D and P2D3 to verify the pressure model of the electrolyte pool fire prediction convection dominated MLR is applicable; reduce the average flame height increases with pressure, through the introduction of a modified dimensionless pressure, HRR, L/D and m fitting "2/P - 2D, verify the Heskestad modified flame height correction formula for the electrolyte pool fire is applicable; reduce the fire plume temperature increases with pressure, through the introduction of pressure correction, characteristic length, fitting ln (T0/T ~) and ln ((z-z0) (P/Q) 2/5), verify the modification after the Heskestad plume temperature formula of electrolyte pool fire is suitable; fitting plume characteristic length of temperature rise and pressure correction after the electrolyte pool fire plume flow into two zones for flame zone and buoyancy plume, does not comply with the three regional McMaffrey model based on cone. Shape calorimeter for different state of charge (State of, Charge, SOC) were studied in 18650 type lithium ion battery and heat radiation under the combustion characteristic parameters, and reveals the internal mechanism of the SOC and radiative heat flux on the combustion characteristics parameters. The oxygen consumption and the mass loss rate obtained consistent HRR curve based on comparing the two curves, the Joule heat released by the release of the decomposition of internal consumption of materials for lithium ion battery oxygen energy and internal short circuit for the proportion of total energy is less than 13%, the lithium battery surface temperature data and cone calorimeter and previous use of ARC measured is consistent also proved that the cone calorimeter can be used for combustion characteristic test of lithium ion battery; higher than 50%SOC, HRR curves were low in the two peak, and with the increase of SOC, HRR peak and the highest surface temperature increasing, ignition and explosion time, gas temperature And the thermal runaway start temperature decreases and the increase of CO and CO2; less than 50%SOC, the fire risk is significantly reduced, HRR curve is only a small peak, weak combustion, low surface temperature, long ignition time, CO and CO2, the risk of burning was significantly lower than that of more than 50% flash and SOC concentrations of less than 50% of the lithium ion battery. It is suggested that the transport of lithium ion battery SOC 50% in the control; with increasing heat radiation, increase the peak value of HRR and the maximum surface temperature, ignition and explosion time, gas temperature and thermal runaway temperature decreased, the fire risk increases; fitting of the experimental data, the ignition of lithium ion battery and time prediction formula the critical heat flux of light. Under different pressure lithium ion battery combustion characteristic parameters were analyzed and quantitative test, and reveals the internal mechanism of the pressure on the combustion characteristic parameters. The strength with pressure reducing combustion. Low pressure to 30kPa combustion does not occur, which can inhibit the production of fire pressure; MLR was positively associated with stress; it has obvious influence the pyrolysis rate of pressure exceeds 155 DEG C on the surface temperature of the surface temperature rise contrast under different pressure, the pressure is higher than 50kPa, 0.4 times of maximum surface temperature decreases with pressure. But less than 50kPa, changes linearly with pressure; gas and fire control and effective ignition time decreased with the increase of pressure, the pressure below 50kPa, the fire risk is significantly reduced.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：V353;TM912

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