Preparation And Modification Of LiFePO₄ Cathode Material

In recent years,the demand for energy is increasing.As an important part of new energy,LiFePO4 cathode material is the main force to solve the problem of energy shortage.LiFePO4 cathode material as an important part of new energy is the main force to solve this problem.However,due to the defects of the material itself,the rate performance is low,which affect the application range of the material in the field of power vehicles.The scanning electron microscope（SEM）,electrochemical workstation,X-ray diffractometer（XRD）,fourier infrared test（FTIR）and other means were used to text nano-scale LiFePO4 cathode materialsto used by the polymer network gel method in this topic.The optimal process conditions for the preparation of LiFePO4 cathode materials by the polymer network gel method were determined.The carbon-coated spherical LiFePO4 cathode material was prepared by the polymer network gel method.Studies had shown that when the monomer content was6%,m（AM）:m（MBAM）=7:2,glucose was the carbon source and n（Fe）:n（C）=1:0.10,The first discharge specific capacity of the sample reached 156 m Ah·g^-1,and the efficiency was 92.3%after 50 cycles.A cathode material of LiFe1-x Alx PO4/C（x=0,0.005,0.01,0.015,0.02,0.025）prepared by doping LiFePO4/C with aluminum ions.LiFe0.985Al0.015PO4/C cathode material had the best electrochemical performance.The discharge specific capacity of167 m Ah·g^-1 at 0.1C was 7.0%higher than that of LiFePO4/C(156 m Ah·g^-1).At a high rate of 5C,the discharge capacity of the material was increased by 29.4%.It can be seen from the cyclic voltammetry test results that this sample had smaller electrochemical polarization and higher electrochemical reaction intensity.From the kinetic analysis,the reaction process in which the material participates was mainly controlled by diffusion.The material LiFe0.985Al0.015PO4/C/Ni prepared by the Ni deposition method showed excellent rate performance.When the coating amount of Ni was 3%,the material LiFe0.985Al0.015PO4/C/Ni exhibiting excellent rate performance.the discharge capacities were 0.1C(167 m Ah·g^-1),0.2C(166 m Ah·g^-1),0.5C(158 m Ah·g^-1),1C(139m Ah·g^-1),5C(57 m Ah·g^-1)and 10C(38 m Ah·g^-1).After 50 cycles at a high rate of 5C,the capacity retention rate was 86.0%.