锂离子电池参数获取及变参数模型

发布时间：2018-04-22 20:25

本文选题：锂离子电池 + 电化学模型　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：锂离子电池因性能优良而在电子设备及电动车领域得到了广泛应用。在电池的使用过程中，如何预测电池的充放电行为具有重要意义，电化学模型能够比较准确的预测电池性能，但是传统电化学模型存在很多缺陷，尤其中高倍率仿真精度很低，本文对如何提高P2D电化学模型的仿真精度进行了深入研究，提出了锂离子电池变参数模型。首先，针对一节自制的锂离子电池，通过物理的、电化学的以及参数辨识的方法获取模型参数，提出一套完整的参数获取方法。采用物理测量的方法获取电池结构参数及设计参数；采用库仑滴定法获取材料开路电势曲线并通过高斯公式进行拟合；采用EIS、PITT、GITT法分别测量了固相扩散系数并进行了比较，结果PITT与GITT法测量结果一致，EIS法测量结果较前两种少一个数量级；采用LSV法测量了材料反应速率常数，结果正极反应速率常数变化范围不大，负极为分段函数形式；采用EIS法以及DC/AC法测量了电解液电导率和阳离子迁移系数；提出通过0.04C的小电流放电曲线辨识初始嵌锂量的方法。其次，深入分析了粒径分布、SEI膜内阻、变化的反应速率常数、变化的固相扩散系数对模型的影响，提出了变参数模型。在粒径分布上，提出了两粒度以及三粒度模型，结果小倍率时小粒度起主导作用，大倍率时大粒度起主导作用使放电截止点提前，同时三粒度模型能够解释0.5C以上“拐点”消失的现象；SEI膜的作用相当于欧姆内阻，相当于放电曲线的“平移”，对放电截止点影响较小；变化的反应速率常数通过改变电流密度分布来影响电压平台，不影响放电截止点；变化的固相扩散系数能够影响表面与平均的SOC分布，使得电压平台以及放电截止点发生变化。最后，对P2D模型与变参数模型进行仿真并比较，在低倍率时，P2D模型仿真精度比变参数模型高，平均误差不超过10mV；在中倍率时，变参数模型的精度远远高于P2D模型，，误差不超过18mV(0.5%)，同时能准确预测放电曲线“拐点”消失的现象；在高倍率时，变参数模型平均误差不超过54mV(1.5%)，因此变参数模型很大程度地提高了仿真精度。
[Abstract]:Lithium ion batteries have been widely used in electronic equipment and electric vehicles due to their excellent performance. In the process of battery use, how to predict the charge and discharge behavior of the battery is of great significance. The electrochemical model can accurately predict the performance of the battery. However, the traditional electrochemical model has many defects, especially the low precision of high rate simulation. In this paper, how to improve the simulation accuracy of P2D electrochemical model is studied, and the variable parameter model of lithium ion battery is proposed. Firstly, for a self-made lithium ion battery, the model parameters are obtained by physical, electrochemical and parameter identification methods, and a complete set of parameters acquisition method is proposed. The structural parameters and design parameters of the battery were obtained by physical measurement, the open-circuit potential curves of materials were obtained by Coulomb titration and fitted by Gao Si's formula, and the solid diffusion coefficients were measured and compared by EISPITT GITT method. Results the results of PITT and GITT methods were consistent with those of the former two methods. The reaction rate constants of materials were measured by LSV method, and the range of positive reaction rate constants was small, and the negative electrode was a piecewise function. The conductivity and cation transfer coefficient of electrolyte were measured by EIS method and DC/AC method, and the method of identifying the initial lithium intercalation by the low current discharge curve of 0.04C was proposed. Secondly, the influence of particle size distribution on the internal resistance of SEI film, the reaction rate constant and the solid diffusion coefficient are analyzed, and the variable parameter model is proposed. In the particle size distribution, two and three particle size models are proposed. The results show that the small particle size plays the leading role when the small ratio is small, and the large particle size plays the leading role in making the discharge cut-off point advance when the ratio is large. At the same time, the three-particle model can explain the phenomenon of disappearance of "inflection point" above 0.5 C. The effect of SEI film is equivalent to ohmic internal resistance, equivalent to "translation" of discharge curve, and has little effect on the cut-off point of discharge. The varying reaction rate constant affects the voltage platform by changing the current density distribution, and does not affect the discharge cut-off point. The variation of solid diffusion coefficient can affect the surface and average SOC distribution, which makes the voltage platform and the discharge cut-off point change. Finally, the simulation and comparison of P2D model and variable parameter model show that the accuracy of P2D model is higher than that of variable parameter model at low rate, the average error is less than 10 MV, and the accuracy of variable parameter model is much higher than that of P2D model at medium ratio. The error is not more than 18 MV / 0. 5, and the "inflection point" of the discharge curve can be accurately predicted. At high rate, the average error of the variable parameter model is not more than 54 MV / 0. 5, so the simulation accuracy of the variable parameter model is greatly improved.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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