| Ternary composite cathode material Li-Ni-Co-Mn-O is a concern of new lithium-ion battery cathode materials with good cycle performance, good rate capability, high discharge capacity, low-cost safety, environmental protection. Li-Ni-Co-Mn-O can be prepared in different proportions, and the research found that the proportion of 1:1:1 for prepared Li Ni1/3Co1/3Mn1/3O2 cathode material of lithium-ion batteries possesses the better overall performance and broad application prospects.Prepared the Li Ni1/3Co1/3Mn1/3O2 is mainly of in the high-temperature solid-phase synthesis, co-precipitation method, sol-gel method, hydrothermal method. The prepared methods will affect the performance of the cathode material severely, considering the advantages and disadvantages of each of the prepared methods, so choosing the co-precipitation method synthesis the Li Ni1/3Co1/3Mn1/3O2 cathode material precursor. Prepared by co-precipitation process, the components of the cathode material can reach the molecular or atomic level mixing, and improve the electrochemical performance.In this paper, Na2CO3 as precipitant and ammonia as complexing agent, controlling the reaction process of the p H, the feed rate, reaction temperature and stirring speed conditions prepare spherical Ni1/3Co1/3Mn1/3CO3 precursor. After the precursor is pre-burned, the oxide and Li OH·H2O was mixed and calcined to prepare Li Ni1/3Co1/3Mn1/3O2 cathode material. By surface morphology analysis of carbonate Ni1/3Co1/3Mn1/3CO3 precursor, we can get a conclusion that p H of the resulting solution, the feed rate of the metal solution, the temperature of the reaction, and the stirring rate have a greater impact on the surface morphology and particle size of precursor. The p H of the reaction solution 10-10.5, metal solution feed rate of 3 ml· min-1, the temperature of the reaction solution of 50℃, stirring speed 1200 rpm, the synthesized precursor of cathode material morphology is better finally.In this study, the cathode material is synthesized at the conditions of p H 11.0-11.5, 10.0-10.5,9.0-9.5,8.0-8.5 and feed rate of 2 ml·min-1, 3 ml·min-1, 4 ml·min-1 and is tested performance testing, analysising the electrochemical properties of the material at different p H values and the feed rate. At p H 10.0-10.5, the feed rate of 3 ml·min-1, the initial discharge capacity is up to 188.1 m Ahg-1. The X-ray diffraction cathode material, the material belongs to a-Na Fe O2 type layered structure, space group R3 m, and the experiment does not introduce impurity phase.To further improve the Li Ni1/3Co1/3Mn1/3O2 cathode material morphology, this experiment study carbonate as precipitator precursor without adding ammonia as complexing agent and prepare transition metal carbonates spherical. Preparation carbonate precursor for p H 7.0,7.5,8.0, 8.5 have obtain different morphologies carbonate precursor obtained. After the precursor calcined, oxide and Li OH·H2O was mixed and calcination. Thus, spherical particles Li Ni1/3Co1/3Mn1/3O2 cathode material was prepared. Ni1/3Co1/3Mn1/3CO3 precursor has a good particle size distribution and morphology. XRD pattern of the material also shows good crystallinity. By testing cycle performance and rate capability, cycle performance and rate properties of the material are better. At p H 8.0, the initial discharge capacity is 178.9 m Ahg-1, and at 5C, after 50 cycles the capacity retention is 91.1%,capacity up to 77 m Ahg-1. This shows Ammoniated co-precipitation method have improved the morphology and performance of the cathode material precursor. |
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