Synthesis And Research Of LiFePO₄/C As Cathode Material For Lithium Ion Battery

LiFePO₄ is considered as a promising cathode material for lithium-ion batteries due to its merits such as low cost, environmental friendliness and good cycling capability. In this paper, the research and development on LiFePO₄ as a cathode material are reviewed systematically, and the aspects that prevent the real application of LiFePO₄ as a cathode material for lithium-ion batteries are also pointed out. In the aims of developing an available technique to prepare LiFePO₄, carbon reduction method was adopted. And the effects of different mass of sucrose and doping Mg²⁺electrochemical properties of LiPePO₄ were investigated. The microstructure and phase compositions of the LiFePO₄ materials were studied by X-ray diffraction (XRD), fourier transform infrared (FT-IR), scanning electron microscope (SEM).The capacity was studied by charge-discharge and cyclic voltammetry (CV) test.Synthesized with LiNO₃,Fe(NO₃)₃·9H₂O,NH₄H₂PO₄ and C₁₂H₂₂O₁₁(sucrose) by carbon reduction.Analysed by XRD,the sample is the olivine-LiFePO₄. Analyzed by the FT-IR, carbon do not be doping into the crystal lattice of LiFePO₄. It is found by SEM that the more sucrose the more carbon coating on the sample. High-power electron microscope founded the thickness of carbon coating layer is 20 nm. It was found by the charge-discharge tests that the sample with the 63mass% ( vs. LiFePO₄) is the best performance of the cycle. Its maximum discharge capacity was 143.2mAh/g at 0.1C, and the discharge capacity was 99.8mAh/g at 2C. The sample has a good cycle life. After 40 cycles at 2C, tested at 0.1C, the first discharge capacity is 88.7mAh/g.The sample have a good capacity renewed.Doping the Mg²⁺into the sample with 63mass% sucrose, it was synthesized by the XRD that it was the olivine-LiFePO₄.It was found by the small angle XRD that with the increase of doping, XRD spectra significantly to the high angle deviation. Note Mg2 + replace some of Fe2 + doping lattice nodes located within the crystal lattice. It was detected by SEM that the sample conductivity increased after doping. It didn't impact the thickness of carbon layer after doping. It was found by the charge-discharge test that LiMg_0.05Fe_0.95PO₄/C was the good cycle performance.Its first discharge capacity was 122.1mAh/g at 0.1C,the capacity is 88.7mAh/g at 2C.Synthesizing by carbon reduction excellent material of LiFePO₄ for short sintering time,low raw material cost and obvious improved effects.I believe in the preparation of high-performance LiFePO4 have good prospects.