Air stable Al2O3-coated Li2NiO2 cathode additive as a surplus current consumer in a Li-ion cell

Abstract

Highly air stable Al₂O₃-coated Li₂NiO₂ cathode additive is prepared by coating with Al iso-propoxide on Li₂NiO₂, obtained from firing of a physical mixture of pure Li₂O and NiO at 600 °C for 10h under N₂ atmosphere. An as-prepared coated cathode has first charge and discharge capacities of 420 mAh/g and 310 mAh/g, respectively, between 4.3V and 1.5V showing an irreversible capacity ratio of 26%. However, when the discharge cut-off voltage increases to 2.75V (2.85V vs. graphite), its discharge capacity decreases to 120 mAh/g, which corresponds to an irreversible capacity ratio of 71%. Owing to such a high irreversible capacity, it can effectively compensate for the irreversible capacity of the Li-ion cell using LiCoO₂ and natural graphite as cathode and anode materials, respectively, in spite of only 4wt% addition to the LiCoO₂ cathode. In addition, the additive prevents the 12V overcharge, thereby preventing the explosion of the cell. We believe that Li₂NiO₂decomposition consumes the surplus current during the overcharging to 12V, and therefore the voltage is not increased until the complete decomposition of the Li₂NiO₂.