| Summary: | 碩士 === 明志科技大學 === 化學工程系碩士班 === 102 === In this thesis, lithium iron phosphate precursors were synthesized by a microwave synthesis method. Then, the prepared precursors were through the carbon-coating and calcination process to obtaine the crystalline LiFePO4/C composite cathode materials. The effects of lithium source, microwave heating time, calcination temperature and time on the electrical properties for LiFePO4/C composites were investigated. The optimum operating conditions for preparing LiFePO4/C cathode materials were obtained. Finally, the spray drying was applied in carbon-coating stage to improve properties of carbon coating and enhance the electric conductivity of LiFePO4/C cathode materials.
The experimental results showed that the optimum conditions for preparing LiFePO4/C materials were 10 min of microwave time, 750℃of calcination temperature, and 5h of calcination time. The prepared lithium iron phosphate by XRD analysis showed the smallest characteristic peaks of impure phase and thus the best crystallinity of lithium iron phosphate. After spray drying with sucrose aqueous solution, the primary LiFePO4 particle could form a uniform spherical secondary particle and a uniform sucrose coating could cover on the surface of LiFePO4 particle. It increased obviously the content of carbon on particles and thus improved the electric conductivity of LiFePO4/C cathode materials. The LiFePO4/C delivered a discharge capacity of 106mAhg-1 at a 0.1C-rate between 4.0 to 2.8 V.
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