title: Highly mobile segments in crystalline poly(ethylene oxide)8:NaPF6 electrolytes studied by solid-state NMR spectroscopy.
abstract: Two types of high-crystallinity poly(ethylene oxide)/NaPF6 electrolytes with ethylene oxide (EO)/Na molar ratios of 8:1 and 6:1, termed as PEO8:NaPF6 and PEO6:NaPF6 with Mw = 6000 g mol(-1) were prepared, and their ionic conductivity, structure, and segmental motions were investigated and compared. PEO8:NaPF6 polymer electrolyte exhibits the room-temperature ionic conductivity 7.7 × 10(-7) S cm(-1) which is about five times higher than the PEO6:NaPF6. By variable-temperature measurements of static powder spectra and (1)H spin-lattice relaxation time in rotation frame ((1)H T1ρ), we demonstrate that crystalline segments are more highly mobile in the crystalline PEO8:NaPF6 with higher ionic conductivity than in the PEO6:NaPF6 with lower ionic conductivity. The large-angle reorientation motion of polymer segments in the PEO8:NaPF6 onsets at lower temperature (∼233 K) with a low activation energy 0.31 eV that is comparable with that of the pure PEO crystal. Whereas, the large-angle reorientation motion of polymer segments in the PEO6:NaPF6 starts around 313 K with a high activation energy of 0.91 eV. As a result of the temperature-enhanced large-angle reorientations, the (13)C static powder lineshape changes markedly from a low-temperature wide pattern with apparent principal values of chemical shift δ33 < δ22 < δ11 to a high-temperature narrow pattern of uniaxial chemical shift anisotropy δ33 > δ22 (δ11). It is suggested that the segmental motion in crystalline PEO-salt complex promotes ionic conductivity.
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Huan
authors.initials: H
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Xinmiao
authors.initials: X
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Liying
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Anmin
authors.initials: A
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071, People's Republic of China.
authors.forename: Jiwen
authors.initials: J
authors.lastname: Feng