摘 要

锂离子电池因其诸多优点，在新能源汽车、电子科技产品、日常民用动力电池等各个方面被愈加广泛地应用。在锂离子电池广泛普及并为人们谋得越来越多便利的同时，锂电池各类相关安全事故层出不穷，制约行业发展。在处置锂电池发生热失控事故火灾时，相较于传统灭火剂的水，液氮因其窒息、降温、抑爆三重灭火特性和鲜明优点更适用于锂电池火场降温灭火。然而在有限的研究和实际应用中，液氮大多用于矿场火灾及燃油火灾，未能真正将液氮研究应用于锂电池热失控火灾事故场景中。在参阅有关文献后，将锂离子电池热失控与液氮降温冷却结合研究。

在本毕业设计第二章以18650型锂离子电池为研究对象，并详细介绍了研究时所需的相关装置设备，在整合这些装置设备及其功能基础之上，设计绘制出18650型锂电池外短路条件下热失控液氮降温冷却处置装置图以及外部电加热18650型锂离子电池热失控燃烧喷射火焰时的液氮降温灭火处置装置图。在这两个液氮处置装置设计完成后，在本毕业设计第三章部分，首先基于两个装置设计图进行了实验路线分析与绘制，第三章后续部分为详细实验方案的展开与实施。主要包括外短路状态热失控研究时的空白实验组方案设计以及不同温度点降温冷却实验方案设计，还有在外加热条件下的锂离子电池热失控空白组实验设计以及不同液氮喷射处置时长条件下的实验组方案的设计。以此探究不同触发因素条件下锂电池热失控时的升温规律及关键温度点参数，以及进行液氮喷射降温冷却处置的效果的分析研究。

通过设计实验装置及实验方案，在本毕业设计第四章分别研究了锂电池外短路条件下的热失控升温危险特性与液氮降温冷却处置研究，以及外短路锂电池热失控燃爆时液氮降温灭火的探索研究。经实验研究分析得出锂电池外短路状态下的升温持续时间与升温最高温度值由电池电量所决定，电池在100％SOC外短路状态下升温至130℃时升温速率会加快。在80℃、100℃喷射液氮具有很好的降温冷却效果，能够快速降低电池表面温度，但因电池电量未耗尽，电池会再次升温至危险温度值，在120℃以0.03MPa出口压力喷射液氮300s可以一次性使得外短路锂电池达到安全状态。同样在外加热锂电池热失控燃爆液氮处置实验研究中，通过实验与分析得出100％SOC锂电池在外加热升温至147±3℃时，其安全阀会弹开，安全阀开启后泄放电池内部压力和热量会对电池形成一种过热时的保护。在温度升至182±4℃时电池会发生热失控喷射着火，在此时喷射液氮可以显著降低电池喷射火时长，降低最高温度，加速电池降温冷却。

在本毕业设计的最后，再次简明总结了本次毕业设计中的装置设计及实验研究结论，提出后续研究规划与方向。同时提出了基于本实验研究装置的18650型锂电池热失控燃爆时液氮自动降温灭火处置装置的设计与实际应用结合优化的展望。

关键词：锂离子电池 热失控 液氮 降温灭火处置

Technology and Device design of Liquid nitrogen cooling disposal for Heat runaway of 18650 Lithium ion battery

ABSTRACT

Lithium-ion batteries are increasingly used in various aspects such as new energy vehicles, electronic technology products, and daily civilian power batteries due to their many advantages. While lithium-ion batteries are widely used and more and more convenient for people, various related safety accidents of lithium batteries are emerging one after another, restricting the development of the industry. Compared with the traditional water extinguishing agent, liquid nitrogen is more suitable for the fire extinguishing in lithium battery fire field because of its fire extinguishing characteristics and distinct advantages of suffocation, cooling and explosion suppression. However, in limited research and practical applications, liquid nitrogen is mostly used in mine fires and fuel fires, and liquid nitrogen research has not been applied to the scene of thermal runaway fire accidents in lithium batteries. In this paper, after referring to relevant studies, the heat runaway of lithium ion battery was combined with liquid nitrogen cooling and cooling to explore the cooling effect and fire-extinguishing disposal effect of liquid nitrogen in the case of heat runaway of lithium battery.

In the second chapter of this graduation design, the 18650 lithium-ion battery is taken as the research object, and the related equipments required for the research are introduced in detail. Based on the integration of these devices and their functions, the 18650 lithium battery is designed and drawn. Diagram of thermal runaway liquid nitrogen cooling and cooling treatment device under short circuit condition and liquid nitrogen cooling and fire extinguishing disposal device for external electric heating 18650 lithium ion battery thermal runaway combustion jet flame. After the design of the two liquid nitrogen disposal devices is completed, in the third chapter of the graduation design, the experimental route analysis and drawing are first carried out based on the two device design drawings. The subsequent part of the third chapter is the development and implementation of the detailed experimental plan. It mainly involves the design of blank experimental group design and the design of cooling temperature cooling experiment for different temperature points in the study of thermal runaway in external short circuit state, as well as the experimental design of thermal runaway blank group of lithium ion battery under external heating conditions and the conditions of different liquid nitrogen injection treatment. The design of the experimental group program. This paper explores the heating law and key temperature point parameters of lithium battery thermal runaway under different triggering factors, as well as the analysis of the effect of liquid nitrogen injection cooling and cooling treatment.

By designing the experimental device and experimental scheme, the thermal runaway temperature hazard characteristics and liquid nitrogen cooling and cooling treatment under the condition of external short circuit of lithium battery were studied in the fourth chapter of the graduation design, and the liquid nitrogen in the thermal runaway ignition of the external short circuit lithium battery was studied. Exploratory research on cooling and extinguishing fires.Through experimental research and analysis, it is concluded that the temperature rise duration and the maximum temperature rise value of the lithium battery are determined by the battery power. When the battery is heated to 130°C under the external short circuit condition of 100% SOC, the heating rate will increase. At 80℃, 100℃ injection liquid nitrogen cooling has the very good cooling effect, can quickly reduce the battery surface temperature, but not because of battery run out, the battery will be heating up again to dangerous temperature, 0.03MPa outlet pressure jetting liquid nitrogen at 120℃ in 300s can be one-time to achieve safe state short circuit outside the lithium battery. In the experimental study of the heat-dissipated blasting liquid nitrogen treatment of the externally heated lithium battery, it is concluded through experiments and analysis that when the 100%SOC lithium battery is heated up to 147±3°C, the safety valve will pop open, and the safety method will be vented after opening. The internal pressure and heat of the battery create a protection against overheating of the battery. When the temperature rises at 182±4°C, the battery will generate thermal runaway injection fire. At this time, the liquid nitrogen can significantly reduce the battery injection fire duration, lower the maximum temperature, and accelerate the battery cooling and cooling.

At the end of this graduation project, the conclusions of the device design and experimental research in this graduation design are summarized and summarized, and the follow-up research plan and direction are proposed. At the same time, the prospect of combining design and practical application of liquid nitrogen automatic cooling and extinguishing treatment device for 18650 lithium battery thermal uncontrolled combustion and explosion based on this experimental research device is proposed.

Key Words: Lithium Ion Battery; Thermal runaway; Liquid nitrogen; Cooling fire disposal

目 录

摘 要 I

ABSTRACT III

第一章 绪论 1

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