Synthesis And Study Of Lithium Manganese Iron Phosphate As Cathode Material For Lithium Ion Battery

Olivine type phosphate anode material LiMPO₄（M=Fe、Mn）with high volume specific energy and mass specific energy,large current charging and discharging,high open circuit voltage,environmental friendly and pollution-free,good safety,low price and so on.In this paper,the co precipitation method and solvothermal method were used to prepare MnCO₃ and NMP（C₂H₈N₂）precursors respectively LiMn_0.8Fe_0.2PO₄ composite was prepared by mechanical activation assisted high temperature solid-state method with lithium carbonate as lithium source,diammonium phosphate as phosphorus source and glucose as carbon source.The structure,morphology and electrochemical properties of the materials were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,constant current charge discharge test and cyclic voltammetry.The results show that the LiMn_0.8Fe_0.2PO₄ cathode material with carbon source content of20%,calcination temperature and time of 650℃/12h has the best charge discharge performance.Under the condition of p H=7.5,the precursor particles of manganese carbonate are uniformly distributed,and the particles of the prepared cathode materials are small and uniformly distributed.At 0.2C,the first charge and discharge reaches90.5m Ah/g.NMP（C₂H₈N₂）was synthesized by solvothermal method.The precursor of manganous ethylenediammonium phosphate prepared by p H=5,the ratio of glycol to water is 11:1,and the surfactant is cetylammonium bromide has good morphology and the prepared cathode materials have special morphology,The first discharge of LiMn_0.8Fe_0.2PO₄ cathode material prepared by this method is 112.48mah/g at 0.2C rate.At the same time,Mg,Co,V were added into LiMn_0.8Fe_0.2PO₄ material.The electrochemical performance of Co doped samples was the best,and the first discharge capacity was 123.8 m Ah/g.