Anodic Aluminum Dissolution in Conducting Salt Containing Electrolytes for Lithium-Ion Batteries

A series of conducting salts in a liquid electrolyte mixture based on propylene carbonate and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)azanide is studied regarding anodic aluminum dissolution. In detail, the compatibility between the conducting salts LiBF4, LiOSO2CF3, LiClO4, LiPF6, and lithium bis(trifluoromethanesulfonyl)azanide and lithium ion grade aluminum foil is investigated. It is verified by electrochemical measurements, microscopy and XPS studies that in ionic liquid containing electrolytes the anodic aluminum dissolution strongly depends on the conducting salt. Furthermore it is shown that the aluminum dissolution can be suppressed effectively by the use of lithium bis(oxalato)borate (LiBOB). It is demonstrated that a minimal concentration of LiBOB is necessary depending on the conducting salt in the electrolyte to protect the aluminum surface reliably from anodic aluminum dissolution.