The degradation process: The effects of electrochemical ageing of Si−C based electrodes were interrogated by determining the coulombic efficiency and electrochemical impedance spectroscopy after cycling. The macroscopic analysis generated inconclusive interpretations for the cycled samples. Local electrochemical measurements by scanning electrochemical microscopy (SECM) were employed as a complementary technique to evaluate the protecting properties of the solid electrolyte interphase (SEI). SECM maps revealed the formation of a protective SEI after few cycles with increasing inhomogeneities with the number of cycles.