The application of atomic force microscopy for the study of Li deposition processes

Li deposition on copper substrates was investigated using atomic force microscopy. The electrolyte solutions included LiClO4 and LiPF6 solutions in propylene carbonate. This work demonstrated the applicability of atomic force microscopy to the study of Li electrochemistry. It proved that the sensitive electrodes and solutions can be properly isolated from atmospheric contaminants and that surface scanning of the tip leaves the electrode's morphology unchanged. Li deposition in LiPF6 solutions was found to be more uniform than Li deposition in LiClO4 solutions. This difference is attributed to the different surface chemistry developed in the two electrolyte solutions as known from previous studies. It was also possible to follow surface film formation on copper upon polarization to potentials higher than those of Li deposition, due to reduction of solution species at low potentials and precipitation of insoluble Li halides, LiOH-Li2O and ROCO(2)Li.