| Olivine-type LiFePO4 has been known as a promising cathode material for lithium-ion batteries due to its stable work voltage, high specific capability, structural stability, good electrical performance, non-toxicity and low cost. Compared with other synthesis techniques, solid-state method is the most attractive method for industry producing with its low cost, simple process and easy industrialization. The electrical property of this material is related to the size of product since large particles lead to a declination on electrical performance. The hard-controlled particle size during the calcinations of solid-state method at high temperature makes it an obstacle for its electrochemical performance.In this paper, LiFePO4 cathode material was prepared by solid-state method. The structure, morphology and electrochemical performance of LiFePO4/C material prepared at different temperature, time, heating rate and cooling procedure were investigated by XRD, SEM and EIS.LiFePO4/C materials were synthesized by FeC2O4-2H2O, NH4H2PO4, LiCO3 and sucrose in N2 atmosphere. The results indicate that increasing sintering temperature and extending sintering time result in higher discharge capacity but some impurity occurs. The optimized method of synthesizing LiFePO4/C material is to pre-sinter the precursor at 350℃ for 6h, then calcined it at 700℃ for 20h. Well crystallized samples with perfect electrochemical performance were obtained at a proper cooling velocity.We investigate the structure and morphology of the samples synthesized by hydrothermal method at different temperature and concentrations. FePO4 were synthesized by a mild hydrothermal method using FePO4, FeCl3 and CO(NH2)2 as the raw materials. The prepared microspheres composed of numerous nanorods are hierarchical structure. LiFePO4 were prepared from FePO4 as the precursors with the same surface morphology. The morphology, size and uniformity of FePO4 could be modified by surfactant. |
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