Synthesis of polycarbonate polymer electrolytes for lithium ion batteries and study of additives to raise the ionic conductivity
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Polymer electrolyte films based on poly(trimethylene carbonate) (PTMC) mixed with LiTFSI salt in different compositions were synthesized and investigated as electrolytes for lithium ion batteries, where the ionic conductivity is the most interesting material property. Electrochemical impedance spectroscopy (EIS) and DSC were used to measure the ionic conductivity and thermal properties, respectively. Additionally, FTIR and Raman spectroscopy were used to examine ion coordination in the material. Additives of nanosized TiO2 and powders of superionically conducting Li1.3Al0.3Ti1.7(PO4)3 were investigated as enhancers of ionic conductivity, but no positive effect could be shown. The most conductive composition was found at a [Li+]:[carbonate] ratio of 1, corresponding to a salt concentration of 74 percent by weight, which showed an ionic conductivity of 2.0 × 10–6 S cm–1 at 25 °C and 2.2 × 10–5 S cm–1 at 60 °C, whereas for even larger salt concentrations, the mechanical durability of the polymeric material was dramatically reduced, preventing use as a solid electrolyte material. Macroscopic salt crystallization was also observed for these concentrations. Ion coordination to carbonyls on the polymer chain was examined for high salt content compositions with FTIR spectroscopy, where it was found to be relatively similar between the samples, possibly indicating saturation. Moveover, with FTIR, the ion-pairing was found to increase with salt concentration. The ionic conductivity was found to be markedly lower after 7 weeks of aging of the materials with highest salt concentrations.
Place, publisher, year, edition, pages
2015. , 29 p.
UPTEC K, ISSN 1650-8297 ; 15020
battery materials, polymer electrolyte, PTMC, poly(trimethylenecarbonate), LiTFSI, nanofillers
batterimaterial, polymerelektrolyt, PTMC, polytrimetylkarbonat, LiTFSI, nanofillers
IdentifiersURN: urn:nbn:se:uu:diva-259513OAI: oai:DiVA.org:uu-259513DiVA: diva2:844529
Subject / course
Master Programme in Chemical Engineering
Mindemark, Jonas, Researcher
Lewin, Erik, Associate senior lecturerBrandell, Daniel, Senior lecturer