請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/2745
標題: | 運用ReaxFF力場模型探討原子尺度下鋰離子電池矽基負極鋰化動力學行為 Atomic-scale Modelling and Simulations of the Lithiation Behavior of the Si Anode in Li-ion Batteries using Reactive Force Field (ReaxFF) |
作者: | Li-Yi Pan 潘立毅 |
指導教授: | 郭錦龍(Chin-Lung Kuo) |
關鍵字: | 鋰電池,矽負極,非等向膨脹,ReaxFF,分子動力學, Li-ion battery,Si anode,anisotropic expansion,ReaxFF,molecular dynamics, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 鋰電池為現今重要的能量儲存裝置,並且被廣泛運用於可攜帶電子裝置、電動車等。目前大部分的商業用鋰電池負極材料使用的是石墨。然而,研究人員發現以矽作為負極材料的鋰電池擁有石墨電極約10倍的單位(重量)電容量。因此被視為鋰電池負極材料的明日之星。然而,矽負極的充電會造成矽的破裂,這主要是由矽負極的不等向膨脹所引起。矽的破裂將嚴重影響鋰電池的表現與可循環使用性。本研究將探討矽負極材料的鋰化機制,我們將使用Reactive Force Field (ReaxFF)的分子動力學模擬探討此問題。我們計算並觀察矽的平板在不同溫度下的鋰化行為,我們部分複製了在實驗中觀察到的不等向膨脹。除此之外,我們也使用了奈米線鋰化並觀察到非等向膨脹。由計算結果我們認為是動力學主導了不等向膨脹的問題。我們認為鋰在Si(110)方向的高擴散速度是此不等向膨脹的主因。我們分析了在鋰化過程中矽所產生的應力。本次模擬仍有一些問題,包括了ReaxFF在能量上的斷點、以及在高溫下不尋常的晶格常數等問題,其中有部分我們仍舊需要找出癥結點。在未來研究中,我們將會在低溫且高鋰濃度下進行鋰化,以完整複製實驗結果觀察到的非等向膨脹。 Li-ion battery is important in energy storages application such as portable electronic devices or electric cars. In most of Li-ion batteries, the anode material is graphite. Some researchers have found that the Si anode has a specific capacity approximately 10-fold larger than graphite. Therefore, it is deemed as a promising anode material. However, it suffers from the fracture problem in charging, due to the anisotropic expansion. This will strongly hinders the performance and cyclability. In this thesis, we will study the lithiation mechanism of Si anode by Reactive Force Field (ReaxFF) molecular dynamics simulations. We have performed the silicon slab lithiation to observe the lithiation behavior at different temperature, and we have reproduced some anisotropy in this case. On the other hand, we have also performed the nanowire lithiation to show the anisotropic expansion. Our results show that the lithiation behavior is mainly kinetic controlled rather than thermodynamic controlled. We suggest that it is the lithium insertion preference in the Si(110) facets that leads to the anisotropic expansion. We have also analyzed the stress developed in the silicon. There are still some problems in the simulations, such as the energy discontinuity and the anomalous lattice constant at high temperature in ReaxFF, and some of which are still under investigation. In the future study, we will perform the simulation at lower temperature and higher lithium concentration to fully reproduce the anisotropic lithiation behavior. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/2745 |
DOI: | 10.6342/NTU201703940 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 材料科學與工程學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-106-1.pdf | 22.06 MB | Adobe PDF | 檢視/開啟 |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。