Synthesis and characterization of LiNi0.95-xCoxAl0.05O2 for lithium-ion batteries

Samples of LiNi0.95-xCoxAl0.05O2 (x = 0.10 and 0.15) and LiNiO2, synthesized by the solid-state reaction at 725°C for 24 h from LiOH·H2O, Ni2O3, Co2O3, and Al(OH)3 under an oxygen stream, were characterized by TG-DTA, XRD, SEM, and electrochemical tests. Simultaneous doping of cobalt and aluminum at the Ni-site in LiNiO2 was tried to improve the cathode performance for lithium-ion batteries. The results showed that co-doping (especially, 5 at.% Al and 10 at.% Co) definitely had a large beneficial effect in increasing the capacity (186.2 mA·h/g of the first discharge capacity for LiNi0.85Co0.10Al0.05O2) and cycling behavior (180.1 mA·h/g after 10 cycles for LiNi0.85Co0.10Al0.05O2) compared with 180.7 mA·h/g of the first discharge capacity and 157.7 mA·h/g of the tenth discharge capacity for LiNiO2, respectively. Differential capacity versus voltage curves showed that the co-doped LiNi0.95-xCoxAl0.05O2 had less intensity of the phase transitions than the pristine LiNiO2