Electrochemical oxidation of propylene carbonate (containing various salts) on aluminium electrodes

Electrochemical reactions taking place on aluminium electrodes in propylene carbonate, with 1.0 M LiClO4, LiBF4, or LiPF6, are investigated in terms of the stability of non-aqueous electrolytes. The techniques used are potential sweep method, X-ray photoelectron spectroscopy, and in situ Fourier-transform infrared (FT-IR) spectroscopy. From these analysis, it is found that the surface of the aluminium electrode is covered with aluminium oxides and fluorides as a passivation layer when it is polarized at 5.5 V versus Li/Li+. Moreover, the surface state of the aluminium electrode depends on the type of electrolyte salt, as do the current-potential curves. On the other hand, in situ FT-IR studies indicate that the oxidation products of propylene carbonate are independent of the type of electrolyte salt. From these results, it is concluded that the stability of propylene carbonate electrolyte depends on the surface state of the aluminium electrode which is strongly combined with the stability of anions.