Understanding the initial stages of Si electrodeposition under diffusion kinetic limitation in ionic liquid-based electrolytes

The electrochemical nucleation and growth of silicon on a vitreous carbon substrate in 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide [BMP][TFSI] is investigated by interpreting potentiostatic current transients. Theoretical model for three-dimensional nucleation, accounting for propagation and overlap of diffusion zones is applied for quantitative characterization of the process. In addition to the established methodology of current maxima analysis in dimensionless coordinates our approach involves interpretation of the entire current transient by a non-linear fitting procedure. The initial stages of the Si phase formation display an instantaneous behavior, showing a tendency for more progressive character with decreasing the applied over-potential. The results attained by analysis of the current transients are confirmed by scanning electron microscopy (SEM). The chemical composition of the deposit is determined by X-Ray Photoelectron Spectroscopy (XPS).