锂离子电池单层电芯内短路建模与热失控触发特性

Modeling internal short circuit and thermal runaway triggers in single-layer lithium-ion battery cells

锂离子电池内短路诱因复杂,为深入研究内短路引起的电池失效问题须构建合适的精细化仿真模型。本工作以NCM/石墨电池为研究对象,围绕电池内短路失效机理,基于电化学-热耦合物理场,建立了考虑热失控放热副反应的三维单层电芯内短路模型,探究了热失控触发边界,并从内外部特征讨论了单层电芯内短路-热失控的演变过程。首先利用Arrhenius公式得到内短路触发的四种放热副反应产热量与反应速率,探究对电池温升影响最大的副反应类别,结果表明内短路过程放热副反应中负极与电解液反应总热量最大。进一步分析单层电芯内四种典型内短路形式的热失控触发特性,综合考虑组分材料导电性和导热性,得到铝-阳极内短路危险程度最高,其短路电阻值与热失控触发时间呈现正相关趋势,且临界短路电阻的高温热点区域面积值约为30 mm^(2)。模拟结果获得了四种形式内短路临界短路电阻值,并揭示了单层电芯内短路-热失控触发时内部锂离子浓度和温度分布的空间演变规律,相关结果可为研究内短路失效机制和设计安全锂离子电池提供理论指导。

Internal short circuits(ISC)present significant challenges in lithium-ion batteries,underscoring the need for accurate simulation models to understand battery failure mechanisms.This study examines NCM/graphite batteries and develops a three-dimensional single-cell ISC model that includes exothermic side reactions with thermal runaway.By utilizing electrochemical-thermal coupling,the study investigates the triggers of thermal runaway and the progression of ISC-induced thermal runaway.Initially,the heat generation and reaction rates of four exothermic side reactions are calculated using the Arrhenius equation.The results indicate that the highest heat is produced by reactions between the negative electrode and the electrolyte.Additionally,an analysis of the thermal runaway triggering characteristics of four typical ISC forms within a single cell reveals that an internal short circuit involving an aluminum anode poses the greatest danger.The resistance value of the short circuit is positively correlated with the time it takes for thermal runaway to be triggered.Additionally,the area of the high-temperature hotspot at the critical short-circuit resistance is determined to be 30 mm^(2).This simulation identifies the critical short-circuit resistance values for four different ISC forms and reveals the internal lithium-ion concentration and temperature distribution when thermal runaway is triggered.These findings offer valuable theoretical insights for investigating ISC failure mechanisms and designing safe lithium-ion batteries.