鋰離子電池之人工薄膜界面脫層力學分析

Abstract

本論文主要為探討人工SEI膜與電極界面上發生的脫層行為。在鋰金屬做為負極材料的鋰離子電池中，為了抑制枝晶生長而利用人工方式於電極表面製造人工SEI膜，提供良好的機械強度與均勻結構，並同時擁有高離子導電率與化學穩定性。然而在循環充放電過後鋰金屬於電極表面不均勻的沉積，造成枝晶的生長，隨著循環次數不斷增加慢慢累積增大，進而推使人工SEI膜與電極間發生脫層行為。 本論文主要利用有限元素軟體對人工SEI膜的脫層行為進行模擬，同時將人工SEI膜與電極間的界面性質以黏著層模型描述。在模擬模型中主要以兩個主軸進行討論，分別為利用不同的界面性質進行模擬、不同枝晶大小與人工SEI膜厚度進行模擬，由不同的模型假設下模擬人工SEI膜與枝晶間的抑制關係。 由本論文所提供的人工SEI膜脫層力學模型進行研究，對於不同界面性質的模擬結果，可歸納出於人工SEI膜對於枝晶的抑制能力可完全反應在脫層半徑上。對於不同的枝晶大小與人工SEI膜厚度模擬結果，可以建構出抑制力(SF)與脫層半徑的關係式和枝晶大小與抑制均佈力(SDF)的關係式。從模擬結果可以更進一步了解到人工SEI膜、枝晶、脫層行為三者之間的關係。

This thesis mainly discusses the delamination behavior occurring at the interface between artificial SEI film and electrode. In the lithium ion battery in which lithium metal is used as a negative electrode material, artificial SEI film is artificially fabricated on the surface of the electrode in order to suppress dendrite growth, providing good mechanical strength and uniform structure, and at the same time having high ionic conductivity and chemical stability. However, after the charge and discharge cycle, the lithium metal deposits unevenly on the surface of the electrode, causing the growth of dendrites, which gradually accumulates as the number of cycles increases, and then causes the delamination behavior between the artificial SEI film and the electrode. In this thesis, the delamination behavior of artificial SEI film is simulated by finite element software, and the interface properties between artificial SEI film and electrode are described by cohesive zone model. In the simulation model, two conditions are mainly discussed, which are simulated by different interface properties, different dendrite sizes and artificial SEI film thickness. The artificial SEI film delamination mechanical model provided by this paper is studied. The simulation results of different interface properties can be summarized as the artificial SEI film can completely react to the delamination radius. For the simulation results of different dendrite size and artificial SEI film thickness, the relationship between suppressing force (SF) and delamination radius and the relationship between dendrite size and suppressing distribution force (SDF) can be constructed. From the simulation results, the relationship between artificial SEI film, dendrites and delamination behavior can be further understood.