Spherical Cathode Materials For Lithium Ion Batteries Lini _{1 / 3} Co _{1 / 3} Mn _{/ 3 1} O ₂ Study On Synthesis And Properties

To increase the tap density and improve the cycle performances ofLiNi_1/3Co_1/3Mn_1/3O₂, the spherical LiNi_1/3Co_1/3Mn_1/3O₂ with a high densityand excellent cycle performance were synthesized by sintering Li₂CO₃and a spherical nickel, manganese and cobalt carbonate precursor(Ni_1/3CO_1/3Mn_1/3CO₃) which were produced by co-precipitating in ourstudy. The facts which affected the physical performances of sphericalNi_1/3Co_1/3Mn_1/3CO₃ were researched to obtain the optimal conditions ofsynthesizing. To obtain the best way of synthesizing sphericalLiNi_1/3CO_1/3Mn_1/3O₂, different methods of synthesizing sphericalLiNi_1/3Co_1/3Mn_1/3O₂.was studied in this research.The tap-density of spherical LiNi_1/3CO_1/3Mn_1/3O₂ powders can reach2.2g·cm^-3. Spherical LiNi_1/3Co_1/3Mn_1/3O₂ was pure phase with layeredstructure. The test results of Li/LiNi_1/3Co_1/3Mn_1/3O₂ indicated that thespherical LiNi_1/3Co_1/3Mn_1/3O₂ delivered 170 and 192 mAh·g^-1 at the rateof 0.2C during the voltage range of 2.7-4.3V and 2.7-4.6V. The capacityretention rates were 87% and 82% after 30 cycles. The test results ofC/LiNi_1/3Co_1/3Mn_1/3O₂ battery indicated that the sphericalLiNi_1/3Co_1/3Mn_1/3O₂ delivered 158 mAh·g^-1 at the rate of 0.2C at thevoltage range of 2.7-4.3V, and the material also showed excellent cyclingperformance that the capacity didn't fade after 50 cycles at the rate of0.2C.To save Co and reduce the cost of the lithium-ion battery, thespherical LiNi_0.4Co_0.2Mn_0.4O₂ and LiNi_0.425Co_0.15Mn_0.425O₂ with a highdensity and pure phase layered structure were synthesized by theco-precipitated precursor. The results of C/LiNi_1/3CO_1/3Mn_1/3O₂ batteryindicated that the spherical LiNi_1/3Co_1/3Mn_1/3O₂ delivered 145,150mAh·g^-1 under the charge/discharge conditions of 0.2C rate and voltagerange of 2.7-4.3V. The discharge capacities fading forLiNi_0.425Co_0.15Mn_0.425O₂ and LiNi_0.4Co_0.2Mn_0.4O₂ were less than 3%. Thecost of LiNi_0.4Co_0.2Mn_0.4O₂ and LiNi_0.425Co_0.15Mn_0.425O₂ are lower, soLiNi_0.4Co_0.2Mn_0.4O₂ and LiNi_0.425Co_0.15Mn_0.425O₂ are also the promosingcommercial materials for lithium ion batteries. To improve the cycle ability of LiNi_1/3Co_1/3Mn_1/3O₂ during 2.7-4.6V,spherical Li(Ni_1/3Co_1/3Mn_1/3)_1-xZn_xO₂ (x=0,0.01,0.03and 0.05) weresynthesized and researched, Zn-doping were made in the synthesizedprocess of carbonate precursors. The results indicate that doping Znimproved the cycle abilities of LiNi_1/3Co_1/3Mn_1/3O₂ discharge/chargeduring 2.7-4.6V, but reduced the capacities and increase the impedance ofLiNi_1/3Co_1/3Mn_1/3O₂. The quantities of Zn-doping are no more than 3%.Surface modifications of LiNi_1/3Co_1/3Mn_1/3O₂ were studied. It wasfound that LiNi_1/3Co_1/3Mn_1/3O₂ samples coated by nano-Al₂O₃ enhancedthe cycling performance at high rate. The results showed that Al₂O₃ wasevenly dispersed on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ well. The cycleperformance of LiNi_1/3Co_1/3Mn_1/3O₂ coated with Al₂O₃ was improvedduring 2.7-4.3V and 2.7-4.6V at the rate of 1 C。...