The effect of solid electrolyte interface formation conditions on the aging performance of Li-ion cells

Abstract

The effect of formation temperatures and current densities on the aging performance of LiNi_1/3Co_1/3Mn_1/3O₂/artificial graphite Li-ion cells during storage and cycle was investigated using three-electrode electrochemical impedance spectroscopy and charge–discharge experiment. The higher formation temperature at 45 °C decreased the resistance of solid electrolyte interphase (SEI) film and the irreversible capacity loss of Li-ion cells during SEI formation process. After Li-ion cell storage at 60 °C for 10 weeks, the ohmic resistance of the negative electrodes and the irreversible capacity loss of the cells reduced 24% and 7.9%, respectively, accompanied by a significant decrease of SEI film resistance when the formation temperature increased from 25 to 45 °C. The higher temperature at 45 °C may facilitate the transformation of metastable ROCO₂Li to stable inorganics to form a stable SEI film. Three hundred cycling tests indicated that the capacity retention of the cell formation at 25 °C was only 87.5%, about 8% less than that of the cell formation at 45 °C. However, the SEI formation current density did not significantly affect the property of SEI film and the irreversible capacity loss of the aged cells.