| With the development of the lithium ion battery industry, which makes LiCoO2battery positive electrode material already cannot satisfy battery industry’s needs. High voltage, big capacity performance of positive electrode materials becomes the research hotspot. LiCoP04olivine structure as a new positive electrode material, the high voltage is4.8V, and the theoretical specific capacity is167mAh/g, and which is considered as one of the new anode materials instead of LiCoO2.Nitric acid system is selected as the research object, the spray flash pyrolysis method is used to get the complete crystal structure and morphology of solid spherical particles LiCoPO4anode materials. Study to discuss which factors such as the precursor solution system, the thermal decomposition temperature, the concentration of the precursor solution, atomized flow, heat treatment temperature, crystal structure and process conditions have influence on crystal structure and microstructure of the final powder material in the preparation process, finally to obtain the optimum process conditions to make LiCoPO4anode materials. Under the optimum process condition, the coated with carbon LiCoPO4/C composite material is prepared, and discuss that the amount of carbon coating on LiCoPO4/C composite material has influence on crystal structure and carbon coating morphology. The main content of the specific studies and research conclusions are as follows:(1) Thermo gravimetric-differential thermal analysis is used to analyse and test the raw mix, the results show that at the275℃mixture start to react and synthesise new material. When the thermal decomposition temperature is400℃, LiCoPO4powder material can success to be prepared, and crystal structure of powder material is complete, microstructure is solid spherical particles, only small part is hollow or broken.(2) Different Precursor solution concentration directly affects the final product microstructure, small concentration of precursor solution can make the atomized droplets become saturation concentration and make its size small. In the process of precipitation nucleation solute precipitate to the whole globe, which makes it easy to prepare solid spherical particle. Whereas larger concentration of precursor solution will make the particles appear hollow or broken phenomenon. When the concentration is0.2mol/L, the solid spherical particle can be made.(3) Atomized flow directly determines that how long time the atomized droplet is in the reactor, lower atomized flow can make the small droplets in the reactor for a long time, which makes it have enough time for small droplet solvent evaporation, drying, pyrolysis and conducting a series of physical and chemical reaction, to synthesise tiny solid spherical particles. Instead of higher atomization flow can make small droplets in the reactor with short time, which makes the particles appear reunite together and not form spherical morphology. Aerosolized amount of15L/min, particle morphology is optimal.(4) High temperature and long time heat treatment can improve the crystal structure and microstructure of powder material, and heat treatment temperature is600℃, the heat treatment time is6h, under the condition to get the final powder material which crystal structure and microstructure is best.(5) Different amount of carbon coated (3wt%,6wt%,9wt%) of the preparation for LiCoO4/C which characteristic peak is the same as characteristic peak of LiCoPO4standard cards, is still the original single pure phase olivine structure. When carbon coating is9wt%, the crystal grain surface coats a layer of thin carbon film, the coated result is best. |
