Electrochemical and structural investigations on solutions of organomagnesium bromide in polymeric ether

The electrolytic behaviour of ethylmagnesium bromide in poly(ethylene oxide) was investigated. Besides polymeric ether, the electrolyte solution contained a small amount of monomeric ether (THF or DEE). Best conductivities were obtained with an ethylene oxide to Mg ratio of 4. For the electrolyte system EtMgBr–P(EO)4–DEE, an electrical conductivity of 0.1 mS cm−1 at 40°C was found. Using these electrolytes, magnesium can be deposited by cathodic reduction as well as dissolved by anodic oxidation. For a magnesium electrode in contact with these electrolytes, an OCV of −1.9 V (vs. Ag–AgCl) was measured. The kind of monomer ether influences significantly the structure of the electrolyte systems. DSC and XRD measurements of the THF-containing electrolytes showed a decrease in content of the crystalline PEO phase with increasing content of EtMgBr, which is not the case for the DEE-containing systems.