FILM FORMATION ON LITHIUM ELECTRODE IN LIALCL4 SO2CL2 AND LIALCL4-3SO2 BASED ELECTROLYTES/

The surface film on lithium in LiAlCl4/SO2Cl2 electrolyte, LiAlCl4:3SO 2 solvate, and mixture of these two electrolytes has been studied usin g ac impedance and scanning electron microscopy coupled to energy disp ersive x-ray analysis. The film was found to be essentially LiCl in th e case of LiAlCl4/SO2Cl2 and the mixture of LiAlCl4:3SO2 solvate and L iAlCl4/SO2Cl2 electrolyte, Differences in the film morphology were obs erved according to the nature of the electrolyte. Electrochemical resu lts implied that the passivating layer behaved as a two-layer film, a primary thin and compact film and a secondary porous film which progre ssively covered the inner layer. The nature of the electrolyte and esp ecially the presence of SO2 at the interface, was found to influence t he growth of the film. A model of formation and growth of the passivat ing film is proposed to describe the behavior of the lithium in these electrolytes.