XPS analysis of a lithium surface immersed in propylene carbonate solution containing various salts

The film resistances of lithium electrodes immersed in propylene carbonate (PC) solution containing various salts were measured using cyclic voltammetry. The changes in the film resistance depended on the type of electrolyte used. The film formed on the lithium electrode surface was analyzed by X-ray photoelectron spectroscopy (XPS). Though the surface of the lithium electrode immersed in PC containing 1.0 mol dm−3 LiAsF6 or LiClO4 reacted with the electrolyte to form small amounts of LiF or LiCl respectively, the native film originally covering the electrode surface was still present after immersion in the electrolyte. However, the native film on the lithium electrode immersed in PC containing 1.0 mol dm−3 LiPF6 or LiBF4 reacted to form a large amount of LiF. This reaction was related to the stability of the salt and the impurities in the electrolyte. The dependence of the film resistance of the lithium electrode on the type of salt used was explained by changes in the composition of the film caused by the reaction between the native film and the salt.