Numerical simulation of cathode coating of lithium-ion battery for porosity optimization

doi:10.11949/0438-1157.20210854

Abstract

Abstract:

Lithium-ion batteries using lithium iron phosphate (LFP) as the cathode material are widely used in electronic products, electric vehicles and other fields, but their energy density still needs to be improved to further meet the application needs of different scenarios. The diffusion of lithium ions in the electrolyte through the pores of the positive electrode is one of the key factors dominating the performance of LFP lithium-ion batteries. The diffusion resistance of the lithium ions can be reduced by certain extent by optimizing the electrode porosity, hence the energy density. In this paper, a quasi-two-dimensional model is used to describe the electrochemical process of the lithium-ion batteries with positive electrode of both gradient and uniform porosities. The influence of gradient porosity of electrode on the energy density of the lithium-ion battery is investigated. A comparison was made between the simulation results with porosities of uniform and gradient distributions. It is found that the introduction of gradiently distributed porosity into electrode coating can improve the utilization ratio of unit active material and increase both the electrolyte flux and the amount of lithium intercalation in the active material, therefore effectively increase the energy density of the lithium-ion battery. Especially, for the thick electrode coating, the enhancement in energy density is more significant with greater gradient porosity. These findings are of great importance for the preparation process of thick electrode slice.

Key words: lithium-ion battery, mathematical modeling, pore structure, gradient distribution, energy density

摘要：

以磷酸铁锂(LFP)为正极材料的锂离子电池在电子产品、电动汽车等领域应用广泛，但其能量密度仍有待提升以进一步满足不同场景应用需求。锂离子在正极孔隙电解液中的扩散过程是LFP锂离子电池性能的控制因素之一，通过优化电极孔隙结构可以在一定程度上减小锂离子在电解质中的扩散阻力进而提升能量密度。采用准二维模型描述电池内部的传质电化学过程，考察了当锂离子电池正极孔隙存在梯度分布后对锂离子电池能量密度的影响及作用机理。通过对比孔隙率均匀分布和梯度分布的电池模拟结果，发现孔隙率的梯度分布能提高单位活性材料的利用率，提升电解质通量和电极活性材料的嵌锂量，从而增加电池能量密度。随着电极厚度的增加，孔隙率分布的梯度越大，对能量密度的提升效果越显著，研究结果对于厚电极涂层的制备工艺具有重要意义。

关键词: 锂离子电池, 数学模拟, 孔隙结构, 梯度分布, 能量密度

CLC Number:

TQ 152

Huiyan WANG, Yiqin CHEN, Jinghong ZHOU, Yueqiang CAO, Xinggui ZHOU. Numerical simulation of cathode coating of lithium-ion battery for porosity optimization[J]. CIESC Journal, 2022, 73(1): 376-383.

王慧艳, 陈怡沁, 周静红, 曹约强, 周兴贵. 锂离子电池正极涂层孔隙结构优化的数值模拟[J]. 化工学报, 2022, 73(1): 376-383.

Figures/Tables 7

Fig.1 Illustration of the normalized position X

Fig.2 The comparison of energy density for lithium-ion batteries with different porosity distributions

Fig.3 The influence of the porosity gradient on the energy density of lithium-ion batteries

Fig.4 The comparison of energy density for lithium-ion batteries of different electrode thicknesses with uniform and gradient porosity under different discharge rates

Fig.5 The concentration distribution of lithium ion in the electrolyte(a) and metal lithium in active particles(b) for lithium-ion batteries with uniform porosity and gradient porosity under different discharge rates

Fig.6 The concentration distribution of lithium ion in the electrolyte for lithium-ion batteries with uniform porosity and gradient porosity at 4 C discharge rate under different electrode thickness

Fig.7 The concentration distribution of metal lithium in active particles for lithium-ion batteries with uniform porosity and gradient porosity at 4 C discharge rate under different electrode thicknesses

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