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Title: High throughput studies of polymer electrolytes for battery and fuel cell applications
Author: Alcock, Hannah Jane
ISNI:       0000 0004 2668 9512
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2009
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New methods for the high-throughput characterisation of polymer electrolytes have been developed. Polymer electrolytes for use in lithium ion batteries have been prepared in a novel systematic manner that involves parallel preparation and subsequent high-throughput conductivity measurements of up to 64 individual compositions in a multi-electrode cell. The method of casting the polymer electrolytes directly onto the substrate also allows high-throughput characterisation by x-ray diffraction. The technique was applied specifically to a ternary system of PVdF-HFP, LiTFSI and PC. By preparing a vast array of samples across the composition range, it was found that the conductivity reached a maximum value when the weight fraction composition was 0.45/0.45/0.1 of PVdF-HFP/LiTFSI/PC with completely free standing samples. The trend of increasing conductivity tended towards the maximum liquid conductivity of LiTFSI/PC. Due to limitations of this method with highly conductive polymer electrolytes, a second novel alternative polymer synthesis, preparation and measurement technique was developed for proton conducting polymers for fuel cell applications. In addition a second multi-electrode cell was designed and constructed specifically allowing AC Impedance measurements to be taken whilst allowing the polymer electrolytes to be subjected to temperature and relative humidity effects. The multi-electrode cell was calibrated using commercially available Nafion samples before being used with synthesised samples. PEEK was sulfonated to SPEEK using varying temperatures and reaction times to obtain many samples with differing DS values. The conductivity of the samples was measured in situ using an in-plane 4 electrode impedance measurement, over a range of environmental conditions. It was found that water loss caused significant conductivity decay under PEMFC conditions for Nafion but not for SPEEK samples. SPEEK with a DS of 75 % was found to have the maximum SPEEK equilibration conductivity of 0.177 S cm-1, a value comparable to that of commercial membranes. By blending this sample with a lower DS SPEEK, high conductivity values could be maintained at temperatures of 105 °C and 75 % relative humidity with maintained mechanical integrity. When an inorganic additive (Zr(HPO4)2) was introduced into the blended samples, the conductivity was enhanced further due to increased water retention within the phosphate structure.
Supervisor: Owen, John Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry