Preparation Of Submicron Ni - Co - Mn Ternary Cathode Materials

Lithium ion battery have drawn great attention due to its high voltage, high capacity, excellent cycle performance and so on. Layered ternary cathode material, LiNi_1-x-yCoxMnyO₂, which has many merits, is considered to be one of the most promising cathode material. This article first introduces the research background, the development, sturcture and status of lithium ion battery, then the synthesis of precursor Ni_1/3Co_1/3Mn_1/3（OH）₂, the synthesis of LiNi_1/3Co_1/3Mn_1/3O₂ through microwave heating were deeply studied, finally the effect of surfactants on the morphology, structure and electrochemical performance was studied. The morphology, structure and electrochemical of samples were characterized through XRD, SEM and charge-discharge test.The synthesis of nano-sheet precursor Ni_1/3Co_1/3Mn_1/3（OH）₂ through ultrasonic-assist co-precipitation were investigated. The result show that, pH value is the key factor in the process of synthesis of precursor. With the increase of pH value, the orientation as well as crystallinity of precursor material increase; The morphology of particle gradually transform to mono nano-sheet.With the increase of temperature, particle size increases gradually, as well as aggregation condition. The particle size increase to about 700nm when the temperature is the highest. Ultrasonic power contribute to improve material particle dispersion. At the same time the introduction of ultrasonic contribute to the formation of nano-sheet.We prepared submicron LiNi_1/3Co_1/3Mn_1/3O₂ through convention calcination treatment of precursor and the temperature and time of calcination were investigated. The result show that, the sample synthesized at 850℃ for 10h has the lowest cation effect and the best electrochemical performance, the electrochemical test show that its initial capacity is 130mAh/g at the rate of 1C,and 106mAh/g at 5C. The capacity retention is 81.5%.LiNi_0.5Co_0.2Mn_0.3O₂ powders are prepared by ultrasonic-assist co-precipitation of the Ni_0.5Co_0.2Mn_0.3（OH）₂ precursor plus post-calcination treatment in this paper. Effect of surfactants including polyvinyl pyrrolidone （PVP）, sodium dodecyl benzene sulfonate （SDBS）, oleyl amine （OA） on the structure, morphology of Ni_0.5Co_0.2Mn_0.3（OH）₂ and electrochemical performance of LiNi_0.5Co_0.2Mn_0.3O₂ materials are studied.The research results show three kinds of the cathode materials are a hexagonal α-NaFeO₂ layered structure, Among them, the cathode material synthesized by PVP exhibit the lowest cation mixing. The precursors synthesized by adding PVP and OA show obvious nanosheet morphology and remained precursor morphology after calcination; while the precursor synthesized by adding SDBS express flake and needle-like morphology and change to obvious needle-like morphology after calcination. The cathode material synthesized by adding PVP has the best electrochemical performance, especially under high rate charge and discharge process, which showed excellent performance and cycle performance.