基于三维分层结构的锂离子电池电化学-热耦合仿真及极耳优化

Electrochemical-thermal coupled simulation and tab optimization of lithium ion battery based on three-dimensional multi-layer structure

本文研究采用基于三维分层结构的锂离子电池电化学-热耦合模型,分析方形电池最小单元的温度场及电流场特性,并优化极耳尺寸。恒流放电工况实验及仿真结果对比显示,模型在0.5 C、1 C及2 C倍率放电时的温度及电压曲线均与实验吻合良好,说明该模型可用于分析电池的电化学特性及热特性。研究发现随着放电倍率的增大,放电终止时刻电池最大温升以凸型曲线的趋势升高,2 C倍率放电时高达33.83℃;自身最大温差以凹型曲线的趋势增大,2 C倍率放电时为1.6645℃;垂直于隔膜方向的平均电流密度及电流密度分布的最大差值呈线性增长,2 C倍率放电终止时分别为43.62 A/m^2及2 A/m^2。进一步研究发现电池最大温升及最大温差与负极耳和正极耳的电阻比Sc显著相关,最优的Sc值被认为在0.875附近。当Sc<0.875时,电池最大温升及最大温差分别以1.52℃/Sc及5.2℃/Sc的速率快速下降;当Sc>0.875时,电池最大温升以0.2021℃/Sc的缓慢速率下降,最大温差以0.1934℃/Sc的速率缓慢上升。另外垂直于隔膜方向的平均离子电流密度及电流密度差值受Sc值的影响较小。

This work focused on the electrochemical-thermal coupled simulation of lithium-ion battery based on three-dimensional multi-layer structure. Temperature and current characteristics of the smallest unit of prismatic battery were analyzed, and tab size was optimized. Temperature and voltage results of experiments under 0.5 C, 1 C, and 2 C constant current discharge processes agreed well with the simulation, and indicated that the model could be furtherly used to analyze the electrochemical and thermal characteristics of the batteries. It was found that with the increase of discharge rate, the maximum temperature rise of the battery at the end of discharge increased in the trend of the convex curve, and it was high to 33.83 ℃ at the end of 2 C discharge process. And The increasing trend of the maximum temperature difference was in the concave curve, which was 1.6645 ℃ at 2 C discharge process. Both the average current density perpendicular to the separator and the current density difference were found linearly increased with the increasing discharge rate. At the end of 2 C discharge process, they were 43.62 A/m^2 and 2.0 A/m^2, respectively. Besides, the temperature rise and maximum temperature difference of the battery were significantly correlated with the resistance ratio of the negative tab to positive tab(Sc). The optimal Sc value was considered to be around 0.875. When Sc was less than 0.875, the maximum temperature rise and maximum temperature difference decreased rapidly at a rate of 1.52 ℃/Sc and 5.2 ℃/Sc respectively. When Sc was greater than 0.875, the maximum temperature rise decreased at a slow rate of 0.2021 ℃/Sc, and the maximum temperature difference increasing rate was 0.1934 ℃/Sc. In addition, the average current density perpendicular to the separator and the current density difference were found little affected by Sc.