The Electrochemical Behavior of Lithium Salt Solutions of γ-Butyrolactone with Noble Metal Electrodes

The electrochemical behavior of lithium salt solutions of γ-butyrolactone with noble metal electrodes (Ag, Au, Pt) was rigorously investigated. Linear sweep voltammetry in conjunction with ex situ FTIR (external reflectance mode) were used in order to analyze various electrode processes in these systems. It was found that the solvent, traces of water and oxygen, is reduced at a potential higher than the potential of lithium bulk deposition (which is the cathodic limiting reaction). These processes form several types of surface films that control the electrochemical behavior of these systems and lead to their apparent stability within an electrochemical window of more than 4V. BL reduction processes precipitate derivatives of lithium butyrate on the electrode surfaces. Water and oxygen reductions form films of LiOH and LiO₂, respectively. These compounds react further, nucleophilically with the solvent to form secondary films. The structure of these films has a pronounced effect on the lithium deposition and dissolution processes. Hence, these systems should also be categorized as solid electrolyte interphase (SEI) systems.