Electrochemical properties of LiNi1−yMyO2 (M = Ni, Ga, Al and/or Ti) cathodes

LiNi1−yMyO2 specimens with compositions LiNiO2, LiNi0.975Ga0.025O2, LiNi0.975Al0.025O2, LiNi0.995Ti0.005O2 and LiNi0.990Al0.005Ti0.005O2 were synthesized by wet milling and solid-state reaction, in which the mixtures with these compositions were preheated at 450 °C for 5 h in air, pressed into pellets and calcined at 750 °C for 30 h under an oxygen stream. All the synthesized samples possessed the α-NaFeO2 structure of the rhombohedral system (space group; R3¯m) with no evidence of any impurities. Among all the specimens, LiNi0.990Al0.005Ti0.005O2 has the largest first discharge capacity 196.3 mAh/g at a rate of 0.1C. LiNiO2 has the best cycling performance, its degradation rate of discharge capacity being 1.06 mAh/(g cycle).