搅拌时间和混合顺序对锂离子电池正极浆料分散特性的影响

doi:10.11949/0438-1157.20230528

摘要/Abstract

摘要：

综合采用电阻抗谱(electrical impedance spectroscopy，EIS)方法、扫描电子显微镜(scanning electron microscopy，SEM)方法和流变法，分析了锂离子电池正极浆料(cathode slurry)的电化学特性、形貌特性和流变特性，并总结出了正极浆料的分散特性。基于COMSOL Multiphysics软件建立了正极浆料的静态仿真模型，从电化学特性角度出发，验证了EIS实验结果的正确性。综合考虑实验分析与仿真验证，结果表明：搅拌时间对正极浆料的分散特性影响较大，较长(9 min以上)或者较短(3 min以下)的搅拌时间会增加阻抗值从而恶化正极浆料内粒子的分散；而6 min的搅拌时间则会减小阻抗值从而使正极浆料内粒子分散。先将炭黑(CB)与PVDF-NMP溶液混合制成CB浆料，后将钴酸锂(LiCoO₂)粒子与CB浆料混合的顺序，能使锂电池正极浆料具有较好的分散特性。最后，提出了一套提高正极浆料分散特性的制浆方案，为高性能锂电池的制备提供了理论依据与实验参考。

关键词: 锂离子电池, 正极浆料, 浆料制备, 浆料分散

Abstract:

This paper comprehensively used electrical impedance spectroscopy (EIS) method, scanning electron microscopy (SEM) method and rheological method to analyze the electrochemical, morphological and rheological properties of the cathode slurry of lithium-ion battery, as a result, the dispersion properties of the cathode slurry are summarized. In addition, based on the COMSOL Multiphysics software, a static simulation model of the cathode slurry was established, and the correctness of the EIS experimental results was verified from the perspective of electrochemical characteristics. Taking into account experiment analysis and simulation verification, the results show that stirring time has a significant impact on the dispersion properties of the cathode slurry, and more (more than 9 min) or less (less than 3 min) stirring time is able to increase the impedance value and deteriorate the dispersion of particles in the positive electrode slurry, while 6 min stirring time is able to reduce the impedance value, thereby dispersing the particles in the cathode slurry. Carbon black (CB) is pre-mixed with PVDF-NMP solution to form CB slurry, and then lithium cobalt oxide (LiCoO₂) particles are mixed with CB slurry to form cathode slurry. This slurry preparation order enables cathode slurry to have good dispersion properties. Finally, this paper proposed a slurry preparation scheme to improve the dispersion properties of cathode slurry with the aim of providing theoretical basis and experimental reference for the preparation of high-performance lithium batteries.

Key words: lithium-ion battery, cathode slurry, slurry preparation, slurry dispersion

中图分类号:

TH 3

王志龙, 杨烨, 赵真真, 田涛, 赵桐, 崔亚辉. 搅拌时间和混合顺序对锂离子电池正极浆料分散特性的影响[J]. 化工学报, 2023, 74(7): 3127-3138.

Zhilong WANG, Ye YANG, Zhenzhen ZHAO, Tao TIAN, Tong ZHAO, Yahui CUI. Influence of mixing time and sequence on the dispersion properties of the cathode slurry of lithium-ion battery[J]. CIESC Journal, 2023, 74(7): 3127-3138.

图/表 26

表1 实验材料

Table 1 Experimental materials

材料名称	级别/型号	生产厂家
钴酸锂(LiCoO₂)	纯度>99.8%	上海麦克林生化科技有限公司
导电炭黑(CB)	电池级	太原力之源科技有限公司
聚偏二氟乙烯(PVDF)	颗粒， M_W=400000	上海麦克林生化科技有限公司
N-甲基吡咯烷酮(NMP)	纯度>98%	上海阿拉丁生化科技股份有限公司

表2 实验设备

Table 2 Experimental equipments

设备	级别/型号	生产厂家
电子天平	WTC2003	杭州万特衡器有限公司
搅拌器	LC-ES-200SH	上海力辰邦西仪器科技有限公司
LCR测量仪	IM3536	日本日置公司
扫描电子显微镜	Sigma500	卡尔蔡司光学有限公司
电热恒温鼓风干燥箱	101-008	绍兴市严氏风机有限公司
旋转流变仪	MARS60	珩璟科技(上海)有限公司

表3 实验材料用量

Table 3 Mass of experimental materials

材料	质量/g
CB	3.0
LiCoO₂	35.2
PVDF	1.5
NMP	34.9

图1 10参数等效电路

Fig.1 Parameter equivalent circuit

图2 不同搅拌时间下的正极浆料的EIS结果

Fig.2 EIS result of cathode slurries under different stirring times

表4 不同搅拌时间下正极浆料EIS数据的关键元件拟合结果

Table 4 Key element fitting results of cathode slurry EIS data with different stirring time

时间	R_SO/Ω	R_P/Ω	R_dl/Ω	C_dl/F
t=3 min	3.54×10¹	4.27×10³	5.27×10¹	1.85×10^-4
t=6 min	2.78×10¹	2.63×10³	3.46×10¹	2.75×10^-4
t=9 min	3.65×10¹	3.58×10³	4.38×10¹	2.30×10^-4
t=12 min	5.01×10¹	3.94×10³	3.69×10¹	2.32×10^-4
t=15 min	3.52×10¹	4.66×10³	6.80×10¹	1.12×10^-4

图3 不同搅拌时间下正极浆料EIS数据的关键电路元件参数变化趋势

Fig.3 Variation trend of key circuit element parameters of cathode slurry EIS data under different stirring time

图4 不同搅拌时间下浆料的SEM图

Fig.4 SEM images of slurry with different stirring times

图5 不同搅拌时间浆料内C元素分布

Fig.5 Distribution of C element in slurry with different stirring times

图6 不同搅拌时间下各浆料的黏度变化

Fig.6 Viscosity curve of each slurry with different stirring time

图7 不同搅拌时间下各浆料的黏弹性

Fig.7 Viscoelastic curves of each slurry with different stirring time

图8 不同混合顺序下正极浆料的EIS结果

Fig.8 EIS result of cathode slurries under different mixing orders

表5 不同混合顺序下正极浆料EIS数据的关键元件拟合结果

Table 5 Key element fitting results of cathode slurry EIS data with different mixing orders

混合顺序	R_SO/Ω	R_P/Ω	R_dl/Ω	C_dl/F
①	6.75×10¹	3.28×10³	2.57×10¹	1.58×10^-4
②	2.95×10¹	2.63×10³	4.99×10⁰	2.38×10^-4
③	2.78×10¹	2.27×10³	4.46×10⁰	2.84×10^-4
④	5.09×10¹	3.89×10³	2.90×10¹	9.38×10^-5

图9 不同混合顺序下正极浆料EIS数据的关键电路元件参数变化趋势

Fig.9 Variation trend of key circuit element parameters of cathode slurry EIS data under different mixing orders

图10 不同混合顺序下浆料的SEM图

Fig.10 SEM images of slurry with different mixing orders

图11 不同混合顺序浆料内C元素分布

Fig.11 Distribution of C element in slurry with different mixing orders

图12 不同混合顺序下各浆料的黏度变化

Fig.12 Viscosity curve of each slurry with different mixing orders

图13 不同混合顺序下各浆料的黏弹性

Fig.13 Viscoelastic curves of each slurry with different mixing orders

图14 几何模型尺寸

Fig.14 Geometric model size

表6 模型材料属性参数

Table 6 Model material attribute parameters

材料	介电常数	电导率/(S/m)	密度/(kg/m³)
LiCoO₂	19	1.00×10^-4	4.90×10³
CB	5	6.67×10⁴	1.80×10³
PVDF-NMP	32.2	1.00×10^-6	1.85×10³

图15 不同搅拌时间下粒子分布状态的仿真模型

Fig.15 Simulation model of particle distribution under different stirring time

表7 不同搅拌时间下各仿真模型的网格信息统计

Table 7 Grid information statistics of each simulation model under different stirring time

模型	四面体	三角形	边单元	顶点单元	最小单元质量	平均单元质量	网格体积/mm³
(a₁)	605846	88281	9216	1197	0.093	0.656	81730
(b₁)	594577	88313	9216	1197	0.093	0.655
(c₁)	585765	85445	8496	1077	0.093	0.655
(d₁)	582733	87021	8869	1135	0.093	0.655

图16 不同搅拌时间下各模型的仿真结果

Fig.16 Simulation results of each model under different stirring time

图17 不同混合顺序下粒子分布状态的仿真模型

Fig.17 Simulation model of particle distribution state under different mixing orders

表8 不同混合顺序下各仿真模型的网格信息统计

Table 8 Grid information statistics of each simulation model under different mixing orders

模型	四面体	三角形	边单元	顶点单元	最小单元质量	平均单元质量	网格体积/mm³
(a₂)	556618	85379	8496	1077	0.093	0.656	81730
(b₂)	627895	88071	9143	1185	0.093	0.656	81730

图18 不同混合顺序下各模型的仿真结果

Fig.18 Simulation results of each model under different mixing orders

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