反应工程方法在锂电池真空干燥模拟上的应用

doi:10.11949/0438-1157.20220141

摘要/Abstract

摘要：

锂离子电池注液之前的真空干燥，对于电芯的循环性能、安全性、稳定性有极其重要的影响。电芯结构设计、材料体系、烘箱尺寸等的不同会导致真空干燥过程存在差异。反应工程方法(REA)在常压、高初始水含量的对流干燥模拟预测上已有广泛应用，本研究将REA干燥理论应用于真空、低初始水含量的干燥过程仿真，发现与实验结果匹配良好。同时考虑了电芯气袋与烘箱环境湿度变化对干燥过程的影响，水含量预测偏差小于10%，利用单因子仿真实验所总结的规律能用于指导锂电池真空干燥工艺的改善。介绍了该模型在生产中的应用情况，也表明REA将在锂电池真空干燥预测上有很好的工业应用前景。

关键词: 锂电池, 真空, 干燥, 反应工程方法, 蒸发, 模拟

Abstract:

Vacuum baking before electrolyte injection has an important impact on the cycling performance, safety and stability of lithium battery. Differences in cell structure design, material system, oven size, etc. will lead to differences in the vacuum drying process. For vacuum baking, drying performance varies with different cell design, materials and oven size. Reaction engineering approach (REA) to drying modelling has been widely used for convective drying under atmospheric pressure and high initial water content materials. Here, REA was applied to the extremely low moisture process for battery vacuum baking. The results matched well with the experimental results. The influence of environmental humidity on drying process is considered in this work, and the prediction error is less than 10%. The rules of thumb established in this work by single factor experiment can guide the improvement of vacuum drying process of lithium-ion battery. The application in mass production is also briefly introduced here. The current work has demonstrated that REA can have excellent application in vacuum drying for lithium battery.

Key words: lithium battery, vacuum, baking, reaction engineering approach, evaporation, simulation

中图分类号:

TQ 02

杨兴富, 陈文, 肖杰, 陈晓东. 反应工程方法在锂电池真空干燥模拟上的应用[J]. 化工学报, 2022, 73(7): 3262-3272.

Xingfu YANG, Wen CHEN, Jie XIAO, Xiaodong CHEN. Application of reaction engineering approach in modelling vacuum baking of lithium battery[J]. CIESC Journal, 2022, 73(7): 3262-3272.

图/表 22

图1 真空干燥简化模型

Fig.1 Simplified model of vacuum drying

图2 简化的电芯温升(a)与环境压力对数(b)曲线

Fig.2 Simplified temperature (a) and environment pressure logarithm (b) curve

表1 真空干燥实验组别

Table 1 Experimental conditions of vacuum drying

组别	温度/℃	真空度/kPa
1	85	-97
2	95	-97
3	85	-101
4	95	-101

图3 仿真模拟的干燥曲线与实验数据对比

Fig.3 Comparison of the simulated drying curve and experiment data

图4 不同条件下电芯水蒸气平均分压对比

Fig.4 Comparison of the average vapor pressure in the cell under different conditions

图5 固体/气体中水浓度云图 (组别1：85℃ & -97 kPa)

Fig.5 Moisture contour of solid and gas phase (Group1：85℃ & -97 kPa)

表2 偏差分析

Table 2 Deviation analysis

项目	组1	组2	组3	组4
相关系数平方R²	0.99909	0.99950	0.99889	0.99893
均方根误差RMSE	9.99408	10.69929	13.09409	9.70212
平均相对误差MRE	0.04018	0.07066	0.08872	0.07039

表3 关键变量初始值

Table 3 Initial value of characteristic variable

变量	数值	数据来源
换气	有/无	实验
传质系数	$h m = D g δ × θ$	文献[13]
多孔介质平均直径	15 μm	实验
孔隙率	0.3	实验
初始水含量	700 mg/kg	实验

表3 关键变量初始值

Table 3 Initial value of characteristic variable

变量	数值	数据来源
换气	有/无	实验
传质系数	$h m = D g δ × θ$	文献[13]
多孔介质平均直径	15 μm	实验
孔隙率	0.3	实验
初始水含量	700 mg/kg	实验

图6 有无“呼吸”换气动作对干燥的影响

Fig.6 Effect of breathing action on drying process

图7 有无“呼吸”换气动作对电芯水蒸气分压的影响

Fig.7 Effect of breathing action on vapor pressure in the cell

图8 传质系数对干燥的影响

Fig.8 Effect of mass transfer coefficient on drying process

图9 颗粒平均直径对干燥的影响

Fig.9 Effect of average diameter of porous media on drying process

图10 孔隙率对干燥的影响

Fig.10 Effect of porosity of porous media on drying process

图11 电芯初始水含量对干燥的影响

Fig.11 Effect of battery initial moisture on drying process

图12 零维模型与三维模型干燥仿真结果对比

Fig.12 Comparison of drying simulation results between 0-D model and 3-D model

图13 钴酸锂电芯的温升(a)与环境压力对数(b)曲线

Fig.13 Temperature (a) and environment pressure logarithm (b) curve

表4 钴酸锂电芯的平衡干基含水率

Table 4 Equilibrium moisture content（dry basis） of lithium cobalt oxide battery

温度/℃	平衡干基含水率X_b
20	0.000300
75	0.000105
85	0.000086
95	0.000080
105	0.000070

图14 钴酸锂电芯的相对活化能曲线

Fig.14 Relative activation energy curve of lithium cobalt oxide battery

图15 钴酸锂电芯水含量仿真预测与实验结果对比

Fig.15 Comparison of moisture content prediction and experimental result of lithium cobalt oxide battery

表5 不同实验条件下实测与预测水含量对比

Table 5 Comparison of measured and predicted moisture content under different experimental conditions

实验条件	实测水含量/ (mg/kg)	预测水含量/ (mg/kg)	偏差/ (mg/kg)
85℃&干燥200 min	73.4	79.9	6.5
85℃&干燥150 min	88.0	85.4	-2.6
85℃&干燥90 min	99.9	108.5	8.6
82℃&干燥90 min	119.5	116.1	-3.4
80℃&干燥85 min	129.7	132.7	3.0
85℃&干燥65 min	143.8	146.7	2.9
83℃&干燥65 min	158.3	164.5	6.2
83℃&干燥60 min	165.9	185.5	19.6

图16 量产实测与预测水含量对比

Fig.16 Comparison of measured and predicted moisture content in mass production

图17 磷酸铁锂电芯(a)与三元电芯(b)水含量仿真预测与实验结果对比

Fig.17 Comparison of moisture content prediction and experimental result of lithium iron phosphate (a) and ternary lithium battery (b)

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