摘要
锂离子电池在发生热失控前会出现明显的体积膨胀,因此研究动力电池膨胀力的变化规律对于提升电池性能及安全性预警具有重要意义。本文以三元/石墨体系电池作为研究对象,探究了其在不同温度、不同倍率下充电时膨胀力的变化规律。动力电池在25℃充电时的膨胀力增加幅值较小,这是因为较低的环境温度使得锂离子堆积在石墨层表面,电池厚度增加,膨胀力也增大;而较高的环境温度不但使得动力电池的体积变大,也会在充电过程中生成SEI膜,故具有更大的膨胀力。动力电池以不同倍率充电时,膨胀力随着倍率增加而逐渐增加,这可能是因为大倍率充电使得电池温度升高且在材料表面生成SEI膜。CT扫描结果精确量化分析电池在充电过程中的厚度变化。由充电过程中的容量微分曲线(dQ/dV)可知,该电池膨胀力增长趋势的不同主要是因为在不同的充电阶段,正负极材料具有不同的相变,进而从机理层面揭示了动力电池充电过程中膨胀力的变化特征。
Lithium-ion batteries demonstrate a noticeable volume swell before thermal runaway occurs.Therefore,studying the changing law of power battery swelling force is significant for improving battery performance and early warning safety.This study explores the changing law of the swelling force for ternary/graphite batteries when charging at various temperatures and rates.The increase in the swelling force of the power battery is minimum when charged at 25℃.Consequently,the low ambient temperature causes lithium ions to accumulate on the surface of the graphite layer,thereby increasing the battery thickness and swelling force.Moreover,the higher the ambient temperature,the larger the volume of the power battery;an SEI film is produced during charging,leading to a greater expansion force.When the power battery is charged at different rates,the swelling force gradually rises with an increase in charging rate,possibly because the high rate charging increases the battery temperature;the SEI film is formed on the material’s surface.The CT scan results accurately quantify and analyze the thickness variations of the battery during the charging process.The capacity differential curve(dQ/dV)during the charging process reveals that the variation in the growth trend of the swelling battery force is primarily due to the various phase transitions of the positive and negative materials in the different charging stages.Then,the change characteristics of the expansion force in the charging process of the power battery are revealed from the mechanism level.
作者
林春景
李丹华
温浩然
马天翼
常宏
常沛祥
李海强
刘仕强
LIN Chunjing;LI Danhua;WEN Haoran;MA Tianyi;CHANG Hong;CHANG Peixiang;LI Haiqiang;LIU Shiqiang(China Automotive Research Institute New Energy Vehicle Inspection Center(Tianjin)Co.,Ltd.,Tianjin 300300,China)
出处
《储能科学与技术》
CAS
CSCD
北大核心
2022年第5期1627-1633,共7页
Energy Storage Science and Technology
基金
退役动力电池无损诊断、余能检测方法研究及分级装备研制(2018YFC1902200)。
关键词
锂离子电池
膨胀力
相变
lithium-ion battery
swelling force
phase transition
