Study On Synthesis And Modification Of Li-Ni-Co-Mn-O

With the energy increasing tensions, rising oil prices, new energy gets more and more attention, one of which is lithium-ion battery. At present, the commercial cathode material for lithium-ion battery is mainly LiCoCO2, which owns preparation simply, good reversibility, long cycle life, stability and excellent electrochemical performance, but the Co is sparse, toxic, and when a high rate charge-discharge exists security issue.As a result, people have to look for a low cost, high specific capacity, long cycle life, more security, more environment-friendly lithium-ion battery cathode materials to replace LiCoO2.LiNi1/3Co1/3Mn1/3O2 owns low cost, high specific capacity, a high rate for charge-discharge, which has gotten public attention.however, There are still some disadvantages, such as, bad circle performance, high irreversible capacity.Li-Ni-Co-Mn-O series of materials are prepared by carbonate precipitation, then LiNi1/3Co1/3Mn1/3O2 is adulterated with Cr,Fe; LiNi1/3Co1/3Mn1/3O2 is coated respectively by SnO2, ZnO, V2O5. The crystal structure and morphology of samples were analyzed by XRD and SEM tests. Electrochemical properties of the samples are studied by charge-discharge tests and AC impedance measurements. The results showed that the samples are a-NaFeO2 layered structure, space group R 3m, spherical morphology, particle even distribution.The sample of the proper amount of Cr3+ doped plays a role in grain refinement and improve the discharge specific capacity and cycle performance. In all samples, Li (Ni1/3Co1/3Mn1/3) 0.98Cr0.02O2 are best, the grains is uniform, the surface array is neat, the first discharge specific capacity is 184.72mAh/g, after 30 cycles, discharge specific capacity is 171.64 mAh/g, the capacity retention rate is 92.92%.The sample of the proper amount of Fe3+ doped does not change the Li(Ni1/3Co1/3Mn1/3)O2 layer structure, refines the grains and improves the discharge specific capacity of samples and cycle performance. In all samples, the performance of Li (Ni1/3Co1/3Mn1/3)0.98Fe0.02O2 is the most outstanding, its fine particles, uniform, smooth surface, the first discharge specific capacity is 170.36mAh/g, after 30 cycles, the discharge specific capacity is 134.28mAh/g, the capacity retention rate is 78.82%.Crystal structure and morphology of LiNi1/3Co1/3Mn1/3O2 by SnO2 coated does not occur to fundamentally change, in all samples, it is the best that LiNi1/3Co1/3Mn1/3O2 is coated with 2% SnO2, the initial discharge specific capacity is 165.09 mAh/g, after 30 cycles, discharge specific capacity is 150.31 mAh/g, the capacity retention rate is 91.05%.LiNi1/3Co1/3Mn1/3O2 by ZnO coated are layer crystal structure, when the amount of coating is 10%, the shuffle is serious. Five samples is uniform particles, small spherical particles, large specific surface area, that is good for Li+ intercalation/emergence, it is the best that LiNi1/3Co1/3Mn1/3O2 is coated with 2% ZnO, the initial discharge specific capacity is 167.99 mAh/g, after 30 cycles, discharge specific capacity is 136.16 mAh/g, the capacity retention rate is 81.05%.LiNi1/3Co1/3Mn1/3O2 by V2O5 coated are still layered structure, but with the increase of coating amount, and gradually begins agglomeration. it is the best that LiNi1/3Co1/3Mn1/3O2 is coated with 2% V2O5, initial discharge specific capacity reached 168.03 mAh/g, after 30 cycles, the discharge specific capacity reached 140.03 mAh/g, capacity retention rate is 83.34%.