Preparation And Modification Of LiFePO₄as The Cathode Material In Lithium-ion Battery

Olivine-like LiMPO₄/C（M=Fe、Mn）is a promising cathode material forrechargeable lithium-ion battery due to its high theoretical capacity, good cyclingstability, rich source of raw materials, low cost and low toxicity. However, its lowelectronic conductivity prevent it from being applied more widely.In this paper we used a new method that self-made NH₄FePO₄H₂O as the Fesource, Li₂CO₃and CH₃COOLi as the Li source to to preparate LiFePO₄/C, Thestructure and morphology of the materials were characteristiced by XRD, SEM, TEMet.al. The electrochemical properties of the materials were studied bycharge-discharge instruments and cyclic voltammetry. The first discharge capacities ofthe twor samples were141.1mAh/g and140.61mAh/g at the rate of0.1C, and theircycling performance are good. The particle sizes were below5μm, and they all hadthe olivine-like structure.Besides, Li_1.04MnPO₄/C were prepared by the s by wet ball milling. The bestsamples was calcined at550℃.And Li_1.04Mn_xFe_1-xPO₄/C（x=0.85，0.75，0.65） wereprepared at the same process. The results of cyclic voltammetry showed the goodreversible of the samples.The carbon coating increased the electronic conductivity.Li_1.04Mn_xFe_1-xPO₄/C had two potential platform in the discharge curve which is4.0-4.1V and3.4-3.5V. The discharge capacity of Li_1.04Mn_0.65Fe_0.35PO₄/C was138.0mAh/g at the rate of0.05C, and specific energy was487.8mWh/g. The cyclingperformance of the sample was very good and maintained at least95.0%at the rate of0.05C. Compared to the single-phase LiMnPO₄/C, the electrochemical performancewere improved. The sample had the olivine-like structure and good electrochemicalproperties. The process could industrialize easily.