| Abstract: | The effects of using different sources of precursor poly(ethylene oxide) (PEO) and acetonitrile solvent on the physical and electrochemical properties of lithium salt-PEO polymer electrolytes were investigated. Although no differences were found due to the use of different types of PEO, the purity of the acetonitrile solvent was found to be critical in controlling the properties of the polymer product. Acetonitrile of nominally relatively low purity produced polymer electrolytes exhibiting largely crystalline type behaviour while the use of nominally high purity solvents gave polymers which were apparently completely amorphous at temperatures above about 50°C. Transport number measurements gave values for the lithium ions of 0.4 at 132°C for the largely crystalline materials and 0.3 at 112°C for the amorphous polymers. Analysis of the acetonitrile solvents revealed the presence of water in the nominally high purity grades and it has been confirmed that water contamination is responsible for the production of the low melting temperature form of the polymer complex. |
