Solid Electrolyte Interphase (SEI) Electrode: II. The Formation and Properties of the SEI on Magnesium in SOCl2-Mg(AlCl)4)2 Solutions

Magnesium metal immersed in thionyl chloride solutions becomes covered by a passivating layer which has properties of solid electrolyte. The buildup and the electrochemical properties of this layer were studied. Tafel slopes measured on freshly immersed Mg electrodes depend linearly on the apparent thickness of the SEI, The reaction resistance and the differential capacitance, on Mg and W electrodes, were measured by several methods. Values of the electrochemical parameters depend on the bias potential. The metal/solution interfacial capacitance of W electrode is higher by an order of magnitude than that of Mg electrode. This higher capacitance decreases markedly, under cat ho die polarization.