Revisiting the stability of aluminum current collectors in carbonate electrolytes for High-Voltage Li-ion batteries

Anodic dissolution (often referred to as corrosion) of the aluminum positive electrode current collector above 3 V vs. Li+/Li can become performance-limiting in high-voltage Li-ion batteries. Herein, the results of a systematic reevaluation of this phenomenon at potentials up to 5.0 V vs. Li+/Li, using different carbonate electrolytes containing LiPF6, LiFSI or LiTFSI, are presented. The anodic dissolution is most likely caused by etching of the Al2O3 passive layer by protons released during the oxidation of the solvent. This sparks off a second oxidation step, involving the oxidation of the aluminum. While a passive AlF3 layer is formed in 1.0 M LiPF6, extensive anodic dissolution of aluminum is seen in 1.0 M LiFSI or LiTFSI at potentials where the solvent undergoes oxidation. In 5.0 M LiFSI, a passive layer of AlF3 is, however, formed most likely due to the presence of fluoride as an impurity in the LiFSI. No significant improvement was seen when using carbon-coated aluminum electrodes.