Electrochemical performances of Li1+zNiO2 (z=0, 0.04, 0.08, 0.10, 0.12, and 0.15) synthesized by a combustion method

LiNiO2 was synthesized by a combustion method with various excess lithium amounts z in Li1+zNiO2 (z=0.00, 0.04, 0.08, 0.10, 0.12, and 0.15). The sample with z=0.10 has the largest first discharge capacity of 195 mAh/g at 0.1 C rate between 2.7 and 4.4 V, with a discharge capacity degradation rate of 1.56 mAh/g/cycle. Samples were fabricated with an active material: acetylene black: binder weight ratio of 85:10:5. The sample with z=0.10 has the smallest unit cell volume, the smallest R-factor, and the largest I003/I104. This shows that the sample with z=0.10 has the smallest cation mixing, and thus has the largest discharge capacities. The dQ/|dV| vs. voltage curves of the samples with z in Li1+zNiO2 (z=0.08, 0.10, 0.12, and 0.15) for charging and discharging, where Q is the charge capacity and V is the voltage, show four peaks. This reveals four phase transitions from H1 to M, from M to H2, from H2 to H2+H3, and from H2+H3 to H3, or vice versa.