The Study Of Preparation And Electrochemical Performance Of NCA As Cathode Material For Lithium-Ion Batteries

As for the research status of lithium-ion battery, each kind of cathode materials has its disadvantages. The poisonous LiCoO2 costs a lot to be prepared, and Co is short of resource. LiNiO2 is really hard to be prepared, and its thermal instability is a very tricky question. Among the rich nickel cathode materials based on LiNiO2, NCA, as the solid solution of LiCoO2, LiNiO2 and LiAlO2, has advantages like high capacity, good thermal stability, low cost et al. NCA is considered to be the second generation of lithium-ion battery which can take part of LiCoO2. NCA also has disadvantages. During the charge and discharge of NCA, cationic disorder will led to the blocking of channels for Li-ion diffusion, which cause the bad electrochemical cycleability and the form of NiO. All these issues are needed to be discussed.This paper takes lithium-ion battery cathode material NCA as the research object. The study is mainly about the preparation of NCA and the different electrochemical performance of different samples. In this paper, I prepared NCA by different ways like sol-gel, hydrothermal and the combination of the two.1) When NCA is prepared by sol-gel, there are different factors to influence the structure and electrochemical performance of samples, like the additive amount of citric acid, the highest sintering temperature, the duration of the highest sintering temperature, the additive amount of conductive agent and the coating thickness of cathode material on aluminum sheet. Finally, a set of parameters which is best for the preparation has been found.2) When Ni0.8Co0.15Al0.05O is prepared by hydrothermal, there are different factors to influence the structure and electrochemical performance of samples, like the additive amount of hydrolysis agent, the additive amount of the surfactant, the concentration of reactants and the volume of reactants. Finally, a set of parameters which could made well-shaped short rod-like Ni0.8Co0.15Al0.05O has been found.3) In the two-step method, the second step is to made short rod-like Ni0.8Co0.15Al0.05O to be solid solution of Li-ion. After several experiments, it is found that if the second step could take the sol-gel method, well-shaped NCA with good cycleability and high rate capacity can be made, compared to the sample simply made by sol-gel method. Although the first discharge capacity of the sample made by two-step method is a slight litter lower than the sample simply made by sol-gel at 0.1C, the advantages of the two-step sample begin to emerge with the rate getting higher and higher. The gap between the two-step sample and the sol-gel sample rises from lOmAh/g at 0.2C to 20mAh/g at 0.5C, and finally to 100mAh/g at 1C. After charged and discharged for 50 cycles at 0.1C, the capacity retention ratio of the two-step sample is 90% which is much higher than 75% of the sol-gel sample. The two-step sample also has great electrochemical cycleability at high rate. The capacity retention ratio is 90% after the sample is charged and discharged for 50 cycles at 1C.