摘 要

本篇模擬以分子動力模擬的方法研究鋰鹽Lithium trifluoromethanesulphonate (LiCF3SO3)於N,N-Dimethylformamide (DMF)/Polyvinylidene fluoride (PVDF)膠態溶液之擴散、導電、配位、集結性質。溫度為308、328、348 K，濃度(DMF：Li)為6：1與15：1，這些參數參考Ward等之實驗。首先以均方位移圖求得擴散係數，並以Nernst-Einstein公式估計導電度。再以自由離子出現之機率修正導電度值，並由徑向分佈函數計算鋰離子周圍之溶劑及陰離子配位數。

模擬所得之鋰離子、CF3SO3-離子、及DMF分子之擴散係數與NMR測量值頗為接近，且導電度值也與實驗傾向一致。結果顯示，添加PVDF後，與鋰離子配位之CF3SO3-離子數不變，但DMF分子數則減少。當DMF：Li濃度由6：1降為15：1，但溫度保持固定時，DMF與PVDF會介入陰、陽離子之間，使得鋰離子周圍之陰離子配位數下降。當鋰鹽濃度固定，且PVDF存在下，鋰離子周圍之陰離子數隨溫度上升而減少，此應為鹽類熱運動增加所致。PVDF的加入，使得鋰離子可同時與CF3SO3-及PVDF之氟原子產生配位，故陰、陽離子結合之程度降低。由於PVDF之活動性較小，與其配位之鋰離子之活動性也隨之降低，使鋰離子與周遭CF3SO3-離子生成之配位鍵亦不易斷裂。

Abstract
Molecular dynamics simulation method has been used to study the diffusivity, conductivity, coordination, and association properties for LiCF3SO3 in N,N-Dimethylformamide (DMF)/ Polyvinylidene fluoride (PVDF) gel at DMF：Li ratio of 6：1 and 15：1 at temperature of 308、328 and 348 K. The diffusion coefficients were computed firstly from the mean-square displacement to estimate the specific conductivities. The computed values were then revised with the probability of free Li+ and CF3SO3-. The average numbers of DMF、PVDF and anion around the lithium ion were computed from the radial distribution functions.
The simulated diffusion coefficients of Li+、F atoms of CF3SO3- and H atoms of DMF agree with the NMR measurement. The computed specific conductivities also has the same trend with experimental results. It was shown after adding PVDF, the number of coordination CF3SO3- ions around Li+ was nearly unchanged, but those of DMF molecules decrease. As the DMF：Li ratio increases from 6：1 to 15：1 at constant temperature, DMF and PVDF would intervene in Li+ and CF3SO3- ions, which reduces the number of coordinating CF3SO3- ions near Li+. At a constant lithium salt concentration and in the presence of PVDF, the number of coordinating CF3SO3- ions around Li+ decreases with increasing temperature, owing to the increase of thermal motion. The addition of PVDF let lithium may coordinate simultaneously with CF3SO3- and florine atom of PVDF, therefore the degree of ion association decreases. Owing to the low mobility of PVDF, the mobility of Li+ which coordinate with PVDF is reduced, leaving the coordination bond between Li+ and CF3SO3- ions uneasy to break.

參 考 文 獻
(1)M. Jose, and G. M. Howell, Vibrational Spectroscopy , 24, 185, (2000).
(2)C.Y. Chiang, Y.J. Shen, M. Jaipal Reddy, and Petter P. Chu, J. Power Sources 123, 222, (2003).
(3)A.M. Voice, J.P. Southall, V. Rogers, G.R. Davies, J.E. Mclntyre and I.M. Ward, Polymer 35, 3364, (1994).
(4)S.F. Johnston, I.M. Ward, J. Cruickshank, and G.R. Davies, Solid state Ionic 90, 39, (1996).
(5)M.J. Williamson, J.P. Southall, H.V.St.A. Hubbard, G.R. Davies, and I.M. Ward, Polymer 40, 3945, (1999).
(6)I.M. Ward, M.J. Williamson, H.V.St.A. Hubbard, J.P. Southall, G.R. Davies, J. Power Sources 81, 700, (1999).
(7)J.C. Soetons, C. Millot, and B. Maigret, J. Phys. Chem. 102, 1055, (1998).
(8)L. Doucey, M. Revault, A. Lautie, A. Chausse, and R. Messina, Electrochim. Acta 44, 2371, (1999).
(9)王俊傑,碩士論文,六氟砷酸鋰於有機溶劑中導電性之電腦模擬,國立成功大學, (2000).
(10)陳輝龍,碩士論文,四氟硼酸鋰於混合有機溶劑中導電性之電腦模擬,國立成功大學, (2001).
(11)郭人華,碩士論文,聚乙醚電解質溶液導電性之分子模擬,國立成功大學, (2002).
(12)黃建中,碩士論文,LiCF3SO3於有機溶劑中導電性之分子模擬,國立成功大學, (2003).
(13)沈政勳,鋰鹽溶於丁內酯之導電性之分子動力模擬,國立成功大學, (2003).
(14)D.N. Theodorou, and U.W. Suter, Macromolecules 18, 1206, (1985).
(15)J.N. Baskir, and U.W. Suter, Macromolecules 21, 1877, (1988).
(16)Discover user guide Part 1, Biosym/MSI Technologies V4.0, (1996).
(17)A. Marchetti, C. Preti, M. Tagliazucchi, L. Tassi, and G. tosi, J. Chem. Eng. Data 36, 365, (1991).
(18)M. Ratner. “Polymer electrolyte Reviews-1”, Elserier Applied Science, London, P.173, (1987).
(19)B.H. Zimm, J. Chem. Phys. 21, 934, (1953).
(20)B.H. Zimm, and J. L. Lundberg, J. Phys. Chem. 60, 425, (1956).
(21)J.L. Lundberg, J. Macromol. Sci. B3, 693, (1969).
(22)L. van Dam, AP. Lyubartsev, A. Laaksonen, and L. Nordenskiold, J. Phys. Chem. B. 102, 10636, (1998).
(23)E. Tocci, D. Hofmann1, D. Paulb, N. Russo, E. Driolia, Polymer 42, 521, (2001).
(24)E. Kucukpinar, and P. Doruker, Polymer 44, 3607, (2003).
(25)R.H. Fuoss, J. Am. Chem. Soc. 57, 2604, (1935).
(26)M.L.T. Asaki, A. Redondo, T.A. Zaeodzinski, and A.J. Taylor, J. Chem. Phys. 116, 10377, (2002).