Review—High-Capacity Li[Ni_1-xCo_x/2Mn_x/2]O₂(x= 0.1, 0.05, 0) Cathodes for Next-Generation Li-Ion Battery

LiNiO 2 with theoretical capacity of 275 mAh g −1 is regarded as a promising cathode material for Li-ion batteries, but its potential capacity has not been fully realized due to the severe capacity loss in the first charge/discharge cycle. Via co-precipitation method, we synthesized Li[Ni 0.90 Co 0.05 Mn 0.05 ]O 2, Li[Ni 0.95 Co 0.025 Mn 0.025 ]O 2 , and LiNiO 2 which delivered 221, 230, and 240 mAh g −1 , respectively, when cycled from 2.7 to 4.3 V vs. Li 0 /Li + at 0.1 C and retained ∼70% of the initial capacity after 100 cycles. To date, such high reversible capacities are not yet to be reported from the Ni-rich Li[Ni 1− x − y Co x Mn y ]O 2 cathodes. The observed high capacities were attributed to the presence of a rock salt phase from severe cation mixing and excess Li ions in the host structure. It is believed that the rock salt phase stabilized the host structure in the delithiated state while the excess Li allowed the Li ions percolated through the rock salt phase which would be electrochemically inactive otherwise.