RECENT STUDIES OF THE LITHIUM LIQUID ELECTROLYTE INTERFACE - ELECTROCHEMICAL, MORPHOLOGICAL AND SPECTRAL STUDIES OF A FEW IMPORTANT SYSTEMS

Our recent studies on the correlation between Li-cycling efficiency, m orphology, interfacial properties and surface chemistry in a variety o f Li battery electrolyte solutions are reviewed. The solvent systems i nclude alkyl carbonate mixtures, ether and ether alkyl carbonate mixtu res, and methyl formate solutions. The techniques include surface sens itive Fourier-transform infrared spectroscopy, both in situ and ex sit u modes, energy dispersive analysis of X-rays, scanning electron micro scopy, impedance spectroscopy and standard electrochemical techniques. The principal points are: (i) the surface chemistry of Li is determin ed by a delicate balance between reduction processes of the solvents, salts and common contaminants; (ii) the surface films initially formed are subjected to ageing processes which gradually change their struct ure and properties; (iii) the heterogeneous chemical structure of the Li electrode's surface films induces non-uniform Li deposition; (iv) t he cycling efficiency is high in systems where Li deposition is smooth and/or the Li deposited is efficiently passivated by the surface spec ies instantaneously formed on it, and (v) it is evident that less hygr oscopic surface species passivate the active metal in solution (e.g., Li2CO3, LiF) more effectively.