Synthesis and Electrochemical Performance of Spherical LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2

Spherical LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2(x=0.075,0.1,1/6) powders were synthesized from the co-precipitated carbonate precursor,Ni_(0.5-x)Co_(2x)Mn_(0.5-x)CO_3(x=0.075,0.1,1/6).The effects of the Co content on the physics and electrochemical performance of LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2 were in- vestigated.The SEM images of LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2 show that the spherical material consists of many primary particles,which sizes increase with the content of Co increasement.The results of X-ray powder diffraction show that all LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2 are pure phase materials with layered struc- tures.The electrochemical tests indicate that the discharge capacities of LiNi_(0.5-x)Co_(2x)Mn_(0.5-x)O_2 increase and the cycle performances become better with the content of Co increasing.Under the charge/discharge conditions of 0.2C rate and voltage range of 2.7-4.3V,the discharge properties of spher- ical LiNi_(0.425)Co_(0.15)Mn_(0.425)O_2,LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2 and LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 are 145,150 and 158 mAh·g~(-1),respectively.The discharge capacity fadings for LiNi_(0.425)Co_(0.15)Mn_(0.425)O_2 and LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2 are less than 3%,however,there is no fade for that of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 after 50 cycles.The results of AC impedance show that the impedance decreases with the content of Co increasing.