Effects of combinatorial AlCl3 and pyrrole on the SEI formation and electrochemical performance of Li electrode

•A protective film is formed on Li surface by modification with AlCl3 and pyrrole.•The film is tight, dense and stable in the electrolyte.•The film leads to reduced interface resistance and improved Li cycling efficiency.•The film also gives rise to homogeneously distributed Li deposits.

Both AlCl3 and pyrrole are simultaneously added to the non-aqueous 1 M LiPF6/EC + DMC electrolyte and their combinatorial effects on the electrochemical performance of Li electrode are systematically studied. A composite protective film of Li–Al alloy and lithium pyrrolide is demonstrated on the Li surface. XRD, EDS, XPS and FTIR are applied to characterize the film. AC impedance, cathodic polarization and galvanostatic charge/discharge cycling tests are performed to evaluate the electrochemical behaviors of the film. It is indicated that the composite protective film formed on Li metal surface in 0.1 M AlCl3 and 0.1 M pyrrole containing electrolyte is dense and tight with high stability in the electrolyte, and gives rise to a low interface resistance and a greatly improved cycling efficiency of the lithium metal electrode.