臺灣博碩士論文加值系統

本文以分子動力模擬的方法，研究鋰鹽LiBF4及LiN(CF3SO2)2(簡稱LiTFSI)的γ-butyrolactone (簡稱GBL)溶液之導電性，及其與溶劑之交互作用。模擬之條件參考Aihara等之實驗參數，鋰鹽濃度0.5、1.0、1.5 M及295 K溫度。
模擬所得結果為鋰離子、負離子及溶劑分子之擴散速率隨濃度增加而遞減，但導電度值則遞增，主要是由於可導電離子增加所致。若以自由鋰離子之產生機率修正導電度值，則計算值與實驗值接近。當鋰鹽濃度高時，正、負離子互相結合的現象愈加明顯，造成離子群內之平均離子數增加，且自由鋰離子之機率遞減。
當LiBF4濃度為1.5 M時，鋰離子周圍第一殼層(約6.35 Å)含有6.3個GBL，及1.7個BF4-離子與之配位。當鋰鹽為LiTFSI時，這些值分別為6.1與1.8個。此外，前者之自由鋰離子機率11.0 ﹪，後者為7.2 ﹪，這顯示Li+與TFSI-結合之傾向較為明顯。當濃度降為0.5 M時，鋰離子周圍之溶劑數增加，而負離子逐漸減少。

Molecular dynamics simulation has been applied to investigate the conducting behavior and salt-solvent interactions for LiBF4 and LiN(CF3SO2)2 (LiTFSI) in γ-butyrolactone (GBL). Simulations were performed at salt concentrations of 0.5, 1.0, and 1.5 M at 295 K, to mimic the experiment at conditions of the previous research conducted by Aihara et al.
The simulated diffusion coefficients for Li+, anion, and solvent decrease with the increase of concentration, but the conductivities increases, due to the increasing number of conducting species. After revision with the probability of free lithium ion, the computed conductivities are close to the experiment as values. At high salt concentrations, the association between Li+ and anions becomes more sever, resulting in the formation of large cluster and reduction of the number of free ions.
At 1.5 M LiBF4 concentration, there are 6.3 solvent molecules and 1.7 anions within the first coordination sphere (about 6.35 Å) of Li+. The corresponding values are 6.1 and 1.8 for LiTFSI, respectively. Moreover, the probability to find free Li+ ion is 11.0 ﹪for the former and 7.2 ﹪for the latter, indicating a stronger tendency for Li+─TFSI- association. As the concentration is reduced to 0.5 M, the number of coordinating solvent molecules increases in contrast to the reduction of anions.

中文摘要…………………………………………………………………………….Ⅰ
英文摘要…………………………………………………………………………….Ⅱ
本文目錄…………………………………………………………………………….Ⅲ
圖目錄……………………………………………………………………………….Ⅳ
表目錄……………………………………………………………………………….Ⅵ
第一章緒論………………………………………………………………………1
第二章分子動力模擬………………………………………………………….8
2-1 模擬系統…………………………………………………………………..8
2-2 模擬方法……………………………………………………………………9
2-3 數據計算……………………………………………………………………10
第三章結果與討論…………………………………………………………….15
3-1 徑向分佈函數與累計原子…………………………………………………15
3-2 擴散係數與導電度…………………………………………………………49
3-3 離子群聚之討論……………………………………………………………60
3-4 黏度分析……………………………………………………………………65
第四章結論…………………………………………………………………….70
參考文獻……………………………………………………………………………71

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