Controlled-potential electrolysis of copper foil and graphite-coated copper foil in a nonaqueous 1 M LiPF6 in a ternary organic carbonate solvent

Controlled-potential electrolysis of battery-grade copper foil and graphite-coated copper foil electrodes in a typical lithium ion battery electrolyte (1 M LiPF6 in propylene carbonate:ethylene carbonate:dimethyl carbonate [1:1:3 vol.]) was performed in order to construct Tafel plots to obtain values of the exchange current, i0, and transfer coefficient, α. The transfer coefficients of both electrodes were found to be small (α = ∼ 0.25), which was consistent with an assumption of a dominant anodic process in the cell. At room temperature, the graphite-coated copper foil was found to have a higher exchange current than the copper foil. This can be explained by the intercalation of lithium ions into the graphite coating which increases the electron transfer rate. In the range of 0 °C to 50 °C, the exchange currents of both electrodes increased with temperature, but at different rates, while the transfer coefficients were not significantly affected by temperature.