Adsorption of Aromatic Decomposition Products from Phenyl-Containing Magnesium-Ion Battery Electrolyte Solutions

摘要

A series of solutions containing PhMgCl in THE solvent are examined electrochemically to investigate the adsorption of an electron-insulating layer. Solutions containing no additional salt, as well as those containing added MgCl2 or Al(OPh)(3), show an initial anodic current response on a platinum working electrode poised between 2 and 4 V (vs Mg2+/0) followed by electrode passivation (minimal current on continued cycling) due to adsorption of aromatic polymer decomposition products on the platinum. On the other hand, PhMgCl-AlCl3 solutions do not demonstrate the adsorption of an aromatic species and show continuous electrolyte degradation. Once an adsorbed layer is formed, a significant increase in electrode impedance is observed (10(3) to 10(5) Omega) with no additional growth of the insulating film. A phenyl radical (Ph-center dot) is deemed the culprit, as adding a phenyl anion source (Ph-) provides apparent 5 V (vs Mg2+/0) stability to nonpassivating electrolyte solutions. Through gel permeation chromatography, the adsorbed polymeric species has an average molar mass of either 50-300 g/mol or 200-800 g/mol depending on electrolysis conditions and electrode composition. Overall, this work shows that electrolytes containing phenyl constituents are nonideal for testing potential rechargeable Mg-ion battery components.