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

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.