锂电子电池过充电和过放电条件下热失控（失效）特性及机制研究

发布时间：2018-01-01 07:23

本文关键词：锂电子电池过充电和过放电条件下热失控（失效）特性及机制研究　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】：大电流充放电、电池管理系统故障、内阻的不一致性等容易引起锂离子电池发生过充电或过放电,轻则导致电池容量下降或电池故障,严重的将引发热失控。在实际应用中,单电池常常处于通风受限的环境,因此,开展锂离子电池在极端通风条件下的过充电和过放电研究不仅可以明确电池过充电、过放电过程中的热行为表现,还可以深化对锂离子电池发生过充电和过放电热失控(失效)根源的认识,掌握诱发热失控(失效)的主要原因。通过定量确定过充电热失控的临界条件,并建立半失效状态的预测方法,为实现锂离子电池的产业化应用提供理论依据和技术支撑。关于电池过充电热失控机制,本文从三个方面开展研究。首先从充电电压和电流角度,采用电池循环仪与加速度量热仪(ARC)联用的方法,研究了通风条件、过充电方式和电流倍率对商用LiCoO2+Li(Ni0.5Co0.2Mn0.3)O2/石墨+SiOx电池过充电热失控行为的影响。分析表明,通过恒流-恒压充满电后恒流过充的危险性大于直接恒流过充。副反应热在0.1C、0.2C、0.5C、1C和2C过充实验中为热失控分别贡献了 82%、84%、80%、60%和40%的能量。在接近热失控时,电池电压会出现一个拐点。为了防止电池热失控的发生,在电池达到拐点电压时,应在2分钟内采取有效的措施来冷却电池。该拐点电压随着电流倍率的增加而线性增加。从电池化学反应的产物来探索过充热失控的化学机理。通过扫描电子显微镜(SEM)和能谱仪(EDS)分析得到 LiCoO2+Li(Ni0.5Co0.2Mn0.3)O2/石墨+SiOx电池正极材料的分解产物可溶于SiOx。从负极上的某些残余区域的层状石墨结构可以推测,负极锂沉积是由于正负电极间距发生变化,并不是因为负极容量的饱和。自制Li(Ni0.5Co0.2Mn0.3)O2/石墨纽扣电池X射线衍射(XRD)测试表明过充后正极材料晶格参数降低并且伴有Ni02产生。在化学反应的基础上揭示了电池过充电过程中内阻演化与热失控的关系,得到了适用于任何小型电池的半失效状态预测方法。在绝热条件下采用伏安特性法和间歇过充法均得到软包电池电阻随着荷电状态(SOC)的增加先下降后上升的规律,拐点为150%SOC。进一步采用交流阻抗法加以验证和解释,发现该拐点的出现是由于固体电解质界面膜(SEI膜)增厚,表现在阻抗谱中的高频和中低频的半圆分离,电池进入半失效状态。因此,在绝热条件下,一系列伏安法实验或一组间歇过充电实验(≤1C)可以有效获得电池的半失效状态。该方法得到了 LiCoO2 + Li(Ni0.5Co0.2Mn0.3)O2/石墨+SiOx电池的验证。总内阻增加率为0.4C Ωh-1可作为阻止热失控的临界内阻判据。在电池过放电研究方面,本文研究揭示了在绝热条件下电池过放电的热行为和失效机理。结果表明,过放电过程中负极温度始终高于正极。当内短路出现时,热量在电池卷绕结构中积聚,导致电池表面温度急剧升高,电流越大,短路放热量越高。综合ARC测试与容量增量分析,表明0.5 V时观测到的放热峰是由于铜集流体的溶解。过放电后电池的可恢复容量与SEI膜和隔膜的状态有关。C80热分析实验表明,在绝热条件下电池经0.2 C过放电至0 V时,负极SEI膜分解,再循环一次后,新的SEI膜产生但稳定性下降,开始分解温度下降至55.1℃。XRD的结果表明,在过放电期间,正极活性材料的晶体结构不变而负极的晶体结构在一定程度上受到损害。
[Abstract]:High current charge discharge, the battery management system failure, the inconsistency between the internal resistance of the lithium ion battery is easy to cause the occurrence of overcharge or overdischarge, light to cause a reduction in battery capacity or battery failure, severe fever will lead out of control. In practical application, a single cell is often limited ventilation environment, therefore, the research of charging and carry out discharge lithium ion battery in the extreme conditions of ventilation can not only clear the battery overcharge, over discharge process of thermal behavior, also can deepen to the lithium ion battery overcharging and over discharging electric control (failure) source of knowledge, master control induced heating (failure) determined the main reason. The critical condition of electric charge control by quantitative prediction method and the establishment of semi failure state, provide theoretical basis and technical support for the industrial application of lithium ion batteries. The battery overcharge and electric control The mechanism, this paper carries out the research from three aspects. Firstly, from the angle of charging voltage and current, the battery cycle and acceleration calorimeter (ARC) method combined with the research on the ventilation conditions, over charge and current rate of commercial LiCoO2+Li (Ni0.5Co0.2Mn0.3) O2/ + SiOx graphite battery overcharge electric control behavior. Analysis shows that the hazard is greater than the constant current charging constant current constant voltage charged directly after the constant current charge. The side reaction heat in 0.1C, 0.2C, 0.5C, 1C and 2C in the experiment of overcharge for thermal runaway respectively contributed 82%, 84%, 80%, 60% and 40% of the energy in the thermal runaway when close. The voltage of the battery, there will be a turning point. In order to prevent the occurrence of battery thermal runaway, when the battery voltage reaches the inflection point, should be in 2 minutes to take effective measures to cool the battery. The inflection point voltage increases with the current rate of linear increase. From the battery producing chemical reaction To explore the chemical mechanism of filled thermal runaway. By scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis of LiCoO2+Li (Ni0.5Co0.2Mn0.3) decomposition products of soluble O2/ cathode material of +SiOx battery in SiOx. graphite from some residual anode area of layered graphite structure on the cathode of lithium deposition is presumably due to positive and negative the electrode spacing changes, not because of negative capacity saturation. The self-made Li (Ni0.5Co0.2Mn0.3) O2/ graphite battery X ray diffraction (XRD) test shows that the lattice parameters of cathode materials had charged with Ni02 and reduce production. Based on the chemical reaction reveals the relationship between the internal resistance of the battery is charged with thermal runaway in the process of evolution the prediction method, semi failure state is applicable to any small batteries. Under the adiabatic condition using volt ampere characteristic method and batch method are overcharge resistance with a charged battery roolls. State (SOC) increased the first decline after rising of the inflection point is further 150%SOC. by AC impedance method to verify and explain the inflection point is found due to the solid electrolyte interface film (SEI film) thickening, high-frequency performance in the impedance spectra in low frequency and semicircle separated from the battery into the half failure state. Therefore, under the adiabatic condition, a series of voltammetry experiments or a group of intermittent charging experiment (1C) semi failure state can effectively obtain the battery. This method has received LiCoO2 + Li (Ni0.5Co0.2Mn0.3) O2/ verification graphite +SiOx battery. The total increase of the internal resistance rate of 0.4C can be used as the criterion of critical resistance Omega H-1 prevent heat out of control. The excessive discharge of the battery research, this paper reveals the thermal behavior of over discharge of the battery under adiabatic condition and failure mechanism. The results show that the discharge of negative temperature is always higher than that of anode. When the internal short circuit When the heat accumulated in the battery winding structure, which causes the surface temperature of the battery increases sharply, the greater the current, short circuit heat is high. The comprehensive analysis of ARC test and capacity increment, exothermic peak observed that 0.5 V is due to dissolved copper collector. Experimental analysis shows that recovery capacity and SEI membrane and diaphragm the state of the.C80 thermal battery after discharge, the battery discharge by 0.2 C to 0 V under the adiabatic condition, negative electrode SEI decomposition, recycling after a new SEI membrane but the stability decreases, initial decomposition temperature dropped to 55.1 degrees.XRD the results show that during overdischarge, crystal the structure of cathode active material constant and crystal structure of anode damage to a certain extent.

【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】：TM912

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