Effect of fluoride additives on the corrosion of aluminum for lithium ion batteries

Effect of fluoride additives was investigated in organic solvents containing LiCF3SO3 to prevent the corrosion of aluminum current collector for lithium ion batteries. LiClO4 was also examined for comparison. Among examined LiBF4, LiPF6, LiAsF6, LiSbF6 and LiClO4, LiBF4 was the best additive to suppress the corrosion of aluminum because its oxidation potential is close to that of CF3SO3- anion. Corrosion currents for aluminum in a complex fluoride- or LiClO4-added solvents became smaller in the order, LiSbF6 > LiAsF6 > LiClO4 > LiPF6 > LiBF4. Oxidation potential of ClO4- is nearly the same as that of CF3SO3-. However, the corrosion currents were similar to or slightly larger than those observed in LiPF6-added solvents. SEM images of electrochemically oxidized aluminum samples indicated that the level of corrosion well coincided with the observed corrosion currents. The corrosion mechanism of aluminum was also proposed. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.