Electrochemical studies of polymer electrolytes
Electrochemical studies of polymer electrolytes
Oxymethylene-linked PEG400 (APEO) was prepared by a modified Williamson ether synthesis to form a high molecular weight host polymer. The electrochemical properties of various lithium salts dissolved in APEO were investigated using a novel method, the gap electrode cell, which was developed for the conductivity measurements of the polymer electrolyte samples. The work demonstrated the electrochemical method for the calculation of ionic conductivity without reference to the cell constant. The method yielded results which are in agreement with those obtained by the conventional cylindrical cell, except at lower temperatures.
In view of the sensitivity of electrochemical devices to water, a study of equilibration of polymer electrolyte (APEO/LiCIO4) with a humidified gas phase was carried out at various values of relative humidity (0-80%). A quartz crystal microbalance (QCM) technique was used for the determination of the water content in the electrolyte. The theory of the technique was reviewed to assess the effect of non-rigidity of sample films and to provide a method of correcting results for viscosity effects by measuring the admittance spectrum close to resonant frequency. For a film with 0.1 μm thickness it was possible to measure the mass change up to sufficient accuracy; however, for thicker films a correction due to fluidity was important especially at high hydration level. Three regimes of water interaction were recognised at 25°C: a strong water interaction below 1% relative humidity, followed by a region of linear increase in water uptake according to Henry's law until 60% humidity, and a region of an aqueous solution at >60% humidity. Conductivity change was found to be a more sensitive indicator of humidity than mass change; this effect was suggested as a device for a humidity sensor. A combined role of water as plasticizer and co-solvent was suggested to account for the complex relation between the ionic conductivity and polymer fluidity.
University of Southampton
Ismail, Iqbal Mohammed Ibrahim
1996
Ismail, Iqbal Mohammed Ibrahim
Ismail, Iqbal Mohammed Ibrahim
(1996)
Electrochemical studies of polymer electrolytes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Oxymethylene-linked PEG400 (APEO) was prepared by a modified Williamson ether synthesis to form a high molecular weight host polymer. The electrochemical properties of various lithium salts dissolved in APEO were investigated using a novel method, the gap electrode cell, which was developed for the conductivity measurements of the polymer electrolyte samples. The work demonstrated the electrochemical method for the calculation of ionic conductivity without reference to the cell constant. The method yielded results which are in agreement with those obtained by the conventional cylindrical cell, except at lower temperatures.
In view of the sensitivity of electrochemical devices to water, a study of equilibration of polymer electrolyte (APEO/LiCIO4) with a humidified gas phase was carried out at various values of relative humidity (0-80%). A quartz crystal microbalance (QCM) technique was used for the determination of the water content in the electrolyte. The theory of the technique was reviewed to assess the effect of non-rigidity of sample films and to provide a method of correcting results for viscosity effects by measuring the admittance spectrum close to resonant frequency. For a film with 0.1 μm thickness it was possible to measure the mass change up to sufficient accuracy; however, for thicker films a correction due to fluidity was important especially at high hydration level. Three regimes of water interaction were recognised at 25°C: a strong water interaction below 1% relative humidity, followed by a region of linear increase in water uptake according to Henry's law until 60% humidity, and a region of an aqueous solution at >60% humidity. Conductivity change was found to be a more sensitive indicator of humidity than mass change; this effect was suggested as a device for a humidity sensor. A combined role of water as plasticizer and co-solvent was suggested to account for the complex relation between the ionic conductivity and polymer fluidity.
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Published date: 1996
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Local EPrints ID: 460275
URI: http://eprints.soton.ac.uk/id/eprint/460275
PURE UUID: 5ed041cb-b72d-452d-ac1c-438e52454c17
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Date deposited: 04 Jul 2022 18:17
Last modified: 04 Jul 2022 18:17
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Author:
Iqbal Mohammed Ibrahim Ismail
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