车用锂离子电池热分析

发布时间：2018-03-12 13:42

本文选题：锂离子电池　切入点：电化学-热特性　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：电动汽车的发展,为降低石油消耗和改善空气质量提供了有效的途径。锂离子电池因其电压高、能量大、无记忆效应、绿色环保等优点而成为电动汽车的主要动力源之一。锂离子电池工作过程受自身与外界环境温度的影响较大,温度较高时,副反应加快,造成电池的容量衰减;温度过低时,电池功率、容量明显下降,可能引起电池寿命的降低,埋下安全隐患。因此分析锂离子电池的热特性,对锂离子电池组进行合理的热管理,对提高电动汽车的安全性,乃至降低能源消耗,改善环境质量都具有极其重要的意义。本文以18650圆柱锂离子电池为研究对象,从单体电池的电化学、热特性出发,逐步探究了该电池的充放电特性、以及充放电过程的产热规律和影响因素;为改善其电池组的散热性能,设计了一种并行通风散热系统,并采用仿真的手段对该散热系统与传统串行通风散热系统的散热效果进行对比分析。所做的主要工作如下:(1)以电荷守恒方程、质量守恒方程以及电极动力学理论等为基础建立18650锰酸锂电池的电化学模型,对恒流充放电过程的电化学性能进行分析。结果表明:在充电时电池充电倍率越高,电池充电过程的“电压平台”越高,平台持续时间越短,电池的充电容量越小;放电时,电池放电倍率越高,“电压平台”越低且持续时间越短,电池放电容量越小。(2)结合传热理论,建立电池电化学-热耦合模型,分析了外部绝热条件、自然对流条件、低强制对流条件以及风冷条件等因素对电池温度的影响,并根据绝热条件下电池充、放电过程的平均温度变化对电池的产热量进行计算。结果表明风冷条件对单体锂离子电池的温度影响较大。(3)对传统串行通风散热系统以及所设计的并行通风散热系统的散热效果进行对比分析。从电池组内单体电池的内部温度、表面温度、以及不同入口条件的角度来看,所设计的并行通风散热系统散热效果均优于传统的串行通风方式,且能源消耗较少。
[Abstract]:The development of electric vehicles provides an effective way to reduce oil consumption and improve air quality. Green environmental protection and other advantages have become one of the main power sources for electric vehicles. The working process of lithium-ion batteries is greatly affected by the temperature of their own and outside environment. When the temperature is high, the side effects are accelerated, resulting in the capacity attenuation of the battery, and when the temperature is too low, The decrease of battery power and capacity may lead to the decrease of battery life and the hidden danger of safety. Therefore, the thermal characteristics of lithium ion battery are analyzed and the reasonable thermal management of lithium ion battery pack is carried out to improve the safety of electric vehicle. It is of great significance to reduce energy consumption and improve environmental quality. In this paper, the charge and discharge characteristics of 18650 cylindrical lithium ion battery are investigated step by step from the electrochemical and thermal characteristics of the single cell. In order to improve the heat dissipation performance of the battery pack, a parallel ventilation heat dissipation system is designed. By means of simulation, the heat dissipation effect of this heat dissipation system is compared with that of the traditional serial ventilation heat dissipation system. The main work done is as follows: 1) the charge conservation equation is used. On the basis of mass conservation equation and electrode dynamics theory, the electrochemical model of 18650 lithium manganese oxide battery was established, and the electrochemical performance of constant current charge-discharge process was analyzed. The results show that the higher the charge rate of the battery is, the higher the charge rate is. The higher the "voltage platform" of the battery charging process, the shorter the duration of the platform, the smaller the charging capacity of the battery, and the higher the discharge rate of the battery during discharge, the lower the "voltage platform" and the shorter the duration. The smaller the discharge capacity of the battery is, the more the heat transfer theory is used to establish the electrochemical-thermal coupling model of the battery. The effects of external adiabatic conditions, natural convection conditions, low forced convection conditions and air-cooled conditions on the cell temperature are analyzed. And according to the battery charge under the adiabatic condition, The results show that the air cooling condition has a great effect on the temperature of the single lithium ion battery. The results show that the air cooling condition has a great effect on the conventional serial ventilation heat dissipation system and the designed parallel ventilation heat dissipation system. The heat dissipation effect of the system was compared and analyzed. From the inside temperature of the single cell in the battery pack, From the point of view of surface temperature and different inlet conditions, the heat dissipation effect of the designed parallel ventilation system is better than that of the traditional serial ventilation system, and the energy consumption is less.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;U469.72

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