LiFePO_(4)电池阴极板升温过程中逸出气体特征分析

Evolved Gases Characterization Analysis during Heating Process of Cathode Plates from LiFePO_(4) Batteries

LiFePO_(4)电池在电动汽车领域具有独特的优势且占有市场持续扩张和稳步增长,电池失效现象的正确理解和失效机理分析对锂离子电池性能的提升和技术改进有着重要作用。其中,电池材料在工作和升温过程中发生产气、热失控等因素为失效现象中最常见的原因,对LiFePO_(4)电池阴极材料在升温过程中的热行为和反应过程所产生的逸出气体种类及动态特征进行了分析。通过采用具有Skimmer采样接口的热分析-质谱联用设备TG-DSC-EI-MS对惰性气氛和氧气气氛下的反应过程热行为和逸出气体进行定性研究。结果揭示,惰性气氛下的分解反应主要集中在435~800℃,其逸出气体以H_(2)、H_(2)O、PF_(5)为主;氧气气氛下的燃烧反应过程分多个阶段,主要集中在四个温度区间:75~200、235~460、465~590、645~745℃,其逸出气体以H_(2)、H_(2)O、C_(x)H_(y)、CO_(2)等组分为主。不同气体组分受温度和气氛影响,其逸出动态特征也不尽相同,其中低温段逸出气体多为电池无机材料的分解和挥发为主,随着温度升高,逸出气体的产生以有机材料的分解和含碳材料的氧化为主,其中含氟气体的逸出行为贯穿整个升温过程中,^(19)F^(+)主要来源于热稳定性较差的LiPF_(6)。该研究结果为LiFePO_(4)电池使用过程中受温度和产气影响机理研究提供了基础信息和方向。

LiFePO_(4) battery has unique advantages in the field of electric vehicles and its market share continues to expand and grows steadily.Correct understanding of battery failure phenomena and analysis of failure mechanisms play important roles in improving the performance and technological improvement of lithium-ion battery.Among them,factors such as gas production and thermal runaway during the operation and heating process of battery materials are the most common reasons for the failure phenomenon.In this paper,an analysis was conducted on the thermal behavior of LiFePO_(4) battery cathode materials during the heating process,as well as the types and dynamic characteristics of the evolved gases produced in the reaction process.Qualitative research was conducted on the thermal behavior and evolved gases of the reaction process under inert and oxygen atmospheres using thermal analysis-mass spectrometry(TG-DSC-EI-MS)equipment with Skimmer sampling interface.The results revealed that the decomposition reaction in the inert atmosphere was mainly concentrated at 435-800℃,and the evolved gases were mainly H_(2),H_(2)O and PF_(5).The combustion reaction process under oxygen atmosphere was divided into several stages,mainly concentrated in four temperature ranges:75-200,235-460,465-590 and 645-745℃.The evolved gases were mainly composed of H_(2),H_(2)O,C_(x)H_(y),CO_(2),etc.Different gas components were affected by temperature and atmosphere,and their dynamic characteristics were also different.In the low temperature stage,the evolved gases were mainly decomposed and volatilized by inorganic materials of batteries.As the temperature roze,the evolved gases were mainly decomposed by organic materials and oxidized by carbon-containing materials.The escaping behavior of fluorine-containing gases ran through the whole heating process,and ^(19)F^(+) mainly came from LiPF 6,which had poor thermal stability.This research result can provide basic information and direction for the research on the mechanism of temperature and gas production during the use of LiFePO_(4) battery.