Electrochemical properties of LiNi1−yTlyO2 cathode

LiNi1−yTlyO2 (y = 0.005, 0.01, 0.025, 0.05 and 0.1) specimens were synthesized by milling and the solid-state reaction. Their electrochemical properties were compared with those of LiNi1−yMyO2 (M = Ga and In). All the samples exhibited the R⁡3¯⁡m structure. LiNi0.95Tl0.05O2 showed the largest first discharge capacity of 179.8 mAh/g and a discharge capacity of 113.8 mAh/g at the 20th cycle. LiNi0.995Tl0.005O2 showed the smallest first discharge capacity of 125.4 mAh/g. The capacity degradation rate decreases as the discharge capacity at n = 5 decreases. LiNi0.975Ga0.025O2 and LiNi0.9In0.1O2 possessed the best electrochemical properties among the samples substituted by Ga and In, respectively. Among LiNi0.975Ga0.025O2, LiNi0.9In0.1O2 and LiNi0.95Tl0.05O2, LiNi0.95Tl0.05O2 showed the largest first discharge capacity, but the worst cycling performance. LiNi0.975Ga0.025O2 possessed the smallest first discharge capacity, but the smallest capacity degradation rate of 0.70 mAh/(g cycle).