| 1. |
- Brandell, Daniel, et al.
(författare)
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Molecular dynamics simulations of Li- and Na-Nafion membranes
- 2006
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Ingår i: SPIE--The International Society for Optical Engineering Vol 61680G. ; , s. 61680G-
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Konferensbidrag (refereegranskat)abstract
- Molecular Dynamics (MD) techniques have been used to study the structure and dynamics of hydrated Li- and Na-Nafion membranes. The membranes were generated using a Monte Carlo-approach for Nafion 117 oligomers of Mw = 1100 and with water contents of 7.5 and 20 % by weight, equivalent to 5 and 15 water molecules per sulfonate group, respectively. After equilibration, local structural properties and dynamical features such as coordination, cluster stability, solvation and ion conductivity were studied. In a comparison between the two cationic systems, it is shown that the Na-Nafion system is more sensitive than Li-Nafion to the level of hydration, and also show higher ion conductivity. The ionic conductivity is shown to increase with higher level of hydration.
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| 2. |
- Brandell, Daniel, et al.
(författare)
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Conduction Mechanisms in Crystalline LiPF6·PEO6 Doped with SiF62- and SF6
- 2005
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Ingår i: Chem. Mater. - : American Chemical Society (ACS). ; 17:14, s. 3673-3680
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations have been made under imposed electric fields for crystalline LiPF6·PEO6, (LiPF6)1-x(Li2SiF6)x·PEO6, and (LiPF6)1-x(SF6)x·PEO6 for x = 0.01 under standard pressure and temperature conditions with the aim of identifying the conduction mechanisms in the systems. Contrary to the results of earlier experimental investigations where only cation mobility was observed, ionic transport is here found to occur in regions between the polymer hemi-helices, with a high transference number (0.9-1.0) for the PF6- anions.
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| 3. |
- Karo, Jaanus, et al.
(författare)
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A molecular dynamics study of the effect of side-chains on mobility in a polymer host
- 2005
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 176:39-40, s. 3041-3044
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Tidskriftsartikel (refereegranskat)abstract
- The effect on polymer dynamics of adding methoxy-terminated poly(ethylene oxide) (PEO) side-chains with different lengths and separations to an amorphous long-chain PEO backbone has been studied by Molecular Dynamics (MD) simulation at 293 K and 330 K. The study is seen as having a direct general relevance to the optimal design of ion-conducting polymer hosts for both Li-ion battery and polymer fuel-cell applications. The MD box used contains a long-chain PEO backbone to which side-chains comprising 3, 6, 7, 8, 9 and 15 EO units are added. The chosen separations between the side-chains are 5, 10, 15, 20 and 50 EO units. All potentials used to describe these systems are taken from earlier work (J. Mater. Chem., 13 (2003) 214). The overall mobility of the polymer host system is found to have both minima and maxima at both temperatures for side-chain lengths in the range 6–9 EO units. This is almost totally independent of side-chain separation at 293 K, while the situation is more complex at 330 K.
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