Modelling of segmental dynamics in polymer electrolyte PPO-LiClO4, by surface fitting of quasi-elastic neutron scattering data

Andersson, Daniel; Carlsson, Patrik; Engberg, Dennis; Torell, L. M.; Börjesson, Lars; McGreevy, R.L.; Howells, W.S.

doi:10.1016/s0921-4526(98)01507-5

Cited by 17 publications

(16 citation statements)

References 9 publications

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“…The log of the relaxation times agrees within 10% with the previous results of Ref. (20). The unphysical increase of the relaxation time in that study is, however, here replaced by the expected decrease, making the present results more reliable.…”

Section: Discussionsupporting

confidence: 91%

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The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

et al. 2005

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AThe relaxation properties of poly(propylene oxide) at temperatures above the glass-transition temperature are studied by quasi-elastic neutron scattering and molecular dynamics (MD) simulations. The contributions to the dynamic structure factor from the segmental motion and the methyl group jump rotation are separated using a threefold jump-rotation model for the methyl side group motion, with a delta function for the distribution of relaxation times, and a stretched exponential function for the segmental motion.This simple model describes momentum transfer and time dependence of the data over a wide temperature range. The results show that with this separation, both neutron and MD data can be well described, and the analysis of both contributions is necessary in order to obtain reliable results for the segmental relaxation and rotational relaxation times at temperature above T g .

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Section: Discussionsupporting

confidence: 91%

“…Both motion types have to be taken into account to get consistent results. The results of a first attempt to use the model for PPO data in a limited temperature range were previously reported (20).…”

Section: Introductionmentioning

confidence: 91%

The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

et al. 2005

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“…In harmony with an equal amount of M and B deuterons in the monomeric unit of the studied polymer, we obtain coefficients a M Ϸ a B Ϸ 0.5 from these fits. 43,44 This study reported an activation energy of 17 kJ/ mol. 2, we see that the spin-lattice relaxation time T 1 M decreases upon cooling, indicating 0 Ӷ 1 for the methyl group jumps at the studied temperatures.…”

Section: -4mentioning

confidence: 89%

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

Vogel

Torbrügge

2006

The Journal of Chemical Physics

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We investigate ion and polymer dynamics in polymer electrolytes PPO-LiClO4 performing 2H and 7Li NMR line-shape analysis. Comparison of temperature dependent 7Li and 2H NMR spectra gives evidence for a coupling of ion and polymer dynamics. 2H NMR spectra for various salt concentrations reveal a strong slowdown of the polymer segmental motion when the salt content is increased. The 2H NMR line shape further indicates that the segmental motion is governed by dynamical heterogeneities. While the width of the distribution of correlation times G(log tau) is moderate for low and high salt content, an extremely broad distribution exists for an intermediate salt concentration of 15:1 PPO-LiClO4. For the latter composition, a weighted superposition of two spectral components, reflecting the fast and the slow polymer segments of the distribution, describes the 2H NMR line shape over a broad temperature range. Analysis of the temperature dependent relative intensity of both spectral components indicates the existence of a continuous rather than a discontinuous distribution G(log tau). Such continuous distribution is consistent with gradual fluctuations of the local salt concentration and, hence, of the local environments of the polymer segments, whereas it is at variance with the existence of large salt-depleted and salt-rich domains featuring fast and slow polymer dynamics, respectively. Finally, for all studied PPO-LiClO4 mixtures, the 2H NMR line shape strongly depends on the echo delay in the applied echo-pulse sequence, indicating that the structural relaxation of the polymer segments involves successive rotational jumps about small angles gamma < 20 degrees .

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“…Polyethylene oxide (PEO), polypropylene oxide (PPO), and 4 poly[bis(methoxy-ethoxyethoxy) phosphazene] (MEEP) are all promising Type I polymer electrolytes. [12][13][14][15][16] The electron-donating groups incorporated into the polymer architecture are responsible for solvating the lithium ion while the fast segmental dynamics promote high ionic conductivities through fluctuation-driven diffusion. [17][18][19] However, Type I polymer electrolytes typically suffer from poor mechanical properties, which is an unfortunate compromise for the fast segmental dynamics.…”

Section: The 21mentioning

confidence: 99%

Method of Measuring Salt Transference Numbers in Ion-Selective Membranes

Vardner

Ling

Russell

et al. 2017

J. Electrochem. Soc.

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A technique to measure the cation-transference number of salts in fully hydrated ion-selective membranes has been developed and demonstrated on Nafion 117 for LiCl and Li 2 SO 4 . Dilute solution theory is used to identify experimental conditions that reduce the propagation of uncertainties in membrane properties to transference number estimates. This technique has advantages over commonly used methods, including the elimination of the need for the analysis of electrode potentials in approaches that exploit electroanalytical methods or the need for additional information required to reconcile NMR-based methods with the bulk transport property. It additionally allows for numerous measurements per day and offers the possibility to relate trace measurements of either cations or anions to values of transference number. For LiCl both modes of the technique were employed; the anion-tracer method is more precise and gives t + = 0.936 ± 0.010. The experimental procedure was repeated using the cation-tracer method for Li 2 SO 4 , and t + = 0.95 ± 0.06 was estimated. The 21 st century presents a key challenge in energy storage due to the intermittency of wind and solar energy sources. Lithium ion batteries, fuel cells, and redox flow batteries are promising technologies for energy storage since they have high energy densities, are environmentally friendly, and have an array of other desirable properties. [1][2][3][4][5][6] Solid electrolytes are ubiquitous for these energy storage systems since they serve the important function of mechanical separation between electrodes. In addition, solid electrolytes circumvent several problems associated with liquid electrolytes such as the leakage of electrolyte solution and the reaction of volatile organic solvents.7 Of the solid electrolytes, polymer electrolytes have garnered the most interest in recent years. [8][9][10][11] These membranes facilitate ionic transport between electrodes, inhibit electron flow between electrodes, prevent direct contact between electrodes, and minimize mixing of the anolyte and catholyte.In recent decades, researchers have sought to understand the relationship between the molecular structure of polymer electrolytes and their performance. These structure-property relationships have been developed for two major types of polymer electrolytes: (I) mixtures of salts in high molecular weight polymers and (II) polymerized ionic liquids (single ion conductors). Polyethylene oxide (PEO), polypropylene oxide (PPO), and 4 poly[bis(methoxy-ethoxyethoxy) phosphazene] (MEEP) are all promising Type I polymer electrolytes.12-16 The electron-donating groups incorporated into the polymer architecture are responsible for solvating the lithium ion while the fast segmental dynamics promote high ionic conductivities through fluctuation-driven diffusion. [17][18][19] However, Type I polymer electrolytes typically suffer from poor mechanical properties, which is an unfortunate compromise for the fast segmental dynamics. Furthermore, Type I polymer electrolytes have relative...

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Modelling of segmental dynamics in polymer electrolyte PPO-LiClO4, by surface fitting of quasi-elastic neutron scattering data

Cited by 17 publications

References 9 publications

The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

Method of Measuring Salt Transference Numbers in Ion-Selective Membranes

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