XPS ANALYSIS FOR THE LITHIUM SURFACE IMMERSED IN GAMMA-BUTYROLACTONE CONTAINING VARIOUS SALTS

Lithium surfaces immersed in gamma-butyrolactone solutions containing salts were analyzed by X-ray photoelectron spectroscopy. The lithium surface before immersion in electrolyte was covered with the native film that consists of Li2CO3, Li2O and LiOH. During the immersion of lithium in electrolyte, the native film reacted with acid in the electrolyte to form lithium halide on the lithium surface. The formation of lithium halide strongly depended on the kind of salt. The reaction rate of the native film in gamma-butyrolactone containing 1.0 mol dm(-3) LiClO4 or LiAsF6 was much less than that in gamma-butyrolactone containing 1.0 mol dm(-3) LiBF4 or LiPF6. The morphology of lithium deposited on the lithium surface immersed in electrolyte for three days was influenced by the surface state of lithium. The film formed on the lithium surface immersed in gamma-butyrolactone containing 1.0 mol dm(-3) LiPF6 was thinner than those immersed in any other electrolytes. The chemical compositions of the lithium surface immersed in gamma-butyrolactone containing 1.0 mol dm(-3) LiPF6 were different from those of the lithium surface immersed in gamma-butyrolactone containing 1.0 mol dm(-3) LiAsF6, LiClO4, or LiBF4. When gamma-butyrolactone containing 1.0 mol dm(-3) LiPF6 was used as electrolyte, dendrite formation was not observed on lithium immersed in the electrolyte for three days.