TY - JOUR
T1 - Conductivity enhancement induced by casting of polymer electrolytes under a magnetic field
AU - Kovarsky, R.
AU - Golodnitsky, D.
AU - Peled, E.
AU - Khatun, S.
AU - Stallworth, P. E.
AU - Greenbaum, S.
AU - Greenbaum, A.
N1 - Funding Information:
The authors express their gratitude to the BSF Foundation for financial support of project 2006149. The work at Hunter College was supported in part by a grant from the U.S. Office of Naval Research.
PY - 2011/12/15
Y1 - 2011/12/15
N2 - We recently presented a procedure for orienting the polyethylene-oxide (PEO) helices in a direction perpendicular to the film plane by casting the polymer electrolytes (PE) under a magnetic field (MF). Here we study the influence of magnetic fields of different strengths and configurations on the structural properties and ionic conductivity of concentrated LiCF 3SO3 (LiTf) and LiAsF6:P(EO) pristine and composite polymer electrolytes containing γ-Fe2O3 nanoparticles. Some data of LiI:P(EO) system are shown for comparison. We suggest that the effect of type of salt (LiI, LiTf and LiAsF6) on the structure-conductivity relationship of the polymer electrolytes cast under magnetic field is closely connected to the crystallinity of the PEO-LiX system. It was found that the higher the content of the crystalline phase and the size of spherulites in the typically cast salt-polymer system, the stronger the influence of the magnetic field on the conductivity enhancement when the electrolyte is cast and dried under MF. Casting of the PE from a high-dielectric-constant solvent results in disentanglement of the PEO chains, which facilitates even more the perpendicular orientation of helices under applied MF. The enhancement of ionic conductivity was appreciably higher in the PEs cast under strong NdFeB magnets than under SmCo. Both bulk (intrachain) and grain-boundary conductivities increase when a MF is applied, but the improvement in the grainboundary conductivity-associated with ion-hopping between polymer chains-is more pronounced. For LiAsF6:(PEO)3 at 65°C, the interchain conductivity increased by a factor of 75, while the intrachain conductivity increased by a factor of 11-14. At room temperature, the SEI resistance of these PEs, cast under NdFeB HMF, decreased by a factor of up to 7, as compared to the typically cast polymer electrolytes. The effect of MF on orientation is observed directly down to the molecular level by 7Li nuclear magnetic resonance measurements.
AB - We recently presented a procedure for orienting the polyethylene-oxide (PEO) helices in a direction perpendicular to the film plane by casting the polymer electrolytes (PE) under a magnetic field (MF). Here we study the influence of magnetic fields of different strengths and configurations on the structural properties and ionic conductivity of concentrated LiCF 3SO3 (LiTf) and LiAsF6:P(EO) pristine and composite polymer electrolytes containing γ-Fe2O3 nanoparticles. Some data of LiI:P(EO) system are shown for comparison. We suggest that the effect of type of salt (LiI, LiTf and LiAsF6) on the structure-conductivity relationship of the polymer electrolytes cast under magnetic field is closely connected to the crystallinity of the PEO-LiX system. It was found that the higher the content of the crystalline phase and the size of spherulites in the typically cast salt-polymer system, the stronger the influence of the magnetic field on the conductivity enhancement when the electrolyte is cast and dried under MF. Casting of the PE from a high-dielectric-constant solvent results in disentanglement of the PEO chains, which facilitates even more the perpendicular orientation of helices under applied MF. The enhancement of ionic conductivity was appreciably higher in the PEs cast under strong NdFeB magnets than under SmCo. Both bulk (intrachain) and grain-boundary conductivities increase when a MF is applied, but the improvement in the grainboundary conductivity-associated with ion-hopping between polymer chains-is more pronounced. For LiAsF6:(PEO)3 at 65°C, the interchain conductivity increased by a factor of 75, while the intrachain conductivity increased by a factor of 11-14. At room temperature, the SEI resistance of these PEs, cast under NdFeB HMF, decreased by a factor of up to 7, as compared to the typically cast polymer electrolytes. The effect of MF on orientation is observed directly down to the molecular level by 7Li nuclear magnetic resonance measurements.
KW - Ionic transport
KW - Magnetic field
KW - Solid polymer electrolyte
UR - http://www.scopus.com/inward/record.url?scp=82955189663&partnerID=8YFLogxK
U2 - 10.1016/j.electacta.2011.04.016
DO - 10.1016/j.electacta.2011.04.016
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AN - SCOPUS:82955189663
SN - 0013-4686
VL - 57
SP - 27
EP - 35
JO - Electrochimica Acta
JF - Electrochimica Acta
IS - 1
ER -