A molecular dynamics study of ion-conduction mechanisms in crystalline low-Mw LiPF6·PEO6
2007 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 17, no 37, 3938-3946 p.Article in journal (Refereed) Published
Molecular dynamics (MD) simulation has been used to probe ion-conduction mechanisms in crystalline LiPF6.PEO6 for smectic- and nematic-ordered models of methyl-terminated short-chain monodisperse poly(ethylene oxide) chains with the formula CH3-(OCH2CH2)23-OCH3; Mw = 1059. The effect of aliovalent substitution of the PF6- anion by ca. 1% SiF62- has also been studied. External electric fields in the range 3-6 x 106 V m-1 have been imposed along, and perpendicular to, the chain direction in an effort to promote ion transport during the short timespan of the simulation. Ion-migration barriers along the polymer channel are lower for the nematic models than for the smectic, with anions migrating along the channels more readily than Li-ions. Ion mobility within the smectic interface could also be confirmed, but at a higher field-strength threshold than along the chain direction. Li-ion migration within the smectic plane appears to be suppressed by ion pairing, while Li-ion transport across the smectic gap is facilitated by uncoordinated methoxy end-groups. Interstitial Li-ions introduced into the PEO channel through SiF62- doping are also shown to enhance Li-ion conduction.
Place, publisher, year, edition, pages
2007. Vol. 17, no 37, 3938-3946 p.
Doping, Interstitials, Energy gap, Pairing, Diffusion, Interfaces, Ion mobility, Polymers, Diffusion barriers, Digital simulation, Electric field effects, External fields, Polyethylene glycols, Theoretical study, Ionic conduction, Molecular ions, Molecular dynamics method
IdentifiersURN: urn:nbn:se:uu:diva-92859DOI: 10.1039/b706938cISI: 000249553200010OAI: oai:DiVA.org:uu-92859DiVA: diva2:166164