Synthesis And Elecrochemical Performance Of Li₂FeSiO₄/C Composite Cathode Material

Li₂FeSiO₄has been attracted more attention as a promising cathode materialfor Li-ion batteries because of its low cost, a wide range of raw materials,environmental friendliness, high safety. However, the application of Li₂FeSiO₄islimited, because of its low the material’s electronic conductivity and lithium ionmigration rate. In this paper, Li₂FeSiO₄/C nanocomposites are prepared bysolid-state method and hydrothermal method. The impact of different preparationconditions to the material morphology and electrochemical performance are studied.The Li₂FeSiO₄/C nanocomposite prepared under different hydrothermaltemperature and carbon content in the control of hydrothermal methods werestudied by structure analysising and electrochemical testing.The lithium-ion battery cathode material Li₂FeSiO₄was prepared by asolid-state method with stoichiometric amount of analytical reagents, Li₂CO₃,FeC₂O₄·2H₂O, SiO₂and sucrose. There are a certain number of impurity in thematerial, the particle size is concentrated in the range of several tens of nanometers.At1/16C rate, the first discharge capacity of Li₂FeSiO₄cathode material is153mAh·g^-1. After35cycles, the discharge capacity is55mAh·g^-1with the capacityretention ratio of36%. Then put stoichiometric amount of C4H6MnO₄·4H2O intothe raw materials and get Li₂Fe_0.5Mn_0.5SiO₄/C. At1/16C rate, the first chargecapacity of Li₂Fe_0.5Mn_0.5SiO₄/C cathode material is211mAh·g^-1, up to308mAh·g^-1in the second cycle and approach to the theoretical capacity of Li₂MnSiO₄.After25cycles, the capacity retention ratio is33%. By comparison, theLi₂Fe_0.5Mn_0.5SiO₄/C cathode material has higher discharge capacity and bettercycle performance, which shows that the doping Mn has effectively improved theperformance of the material.The lithium-ion battery cathode materials Li₂FeSiO₄were prepared byhydrothermal method with stoichiometric amount of analytical reagents,CH3COOLi·2H2O, FeC₂O₄·2H2O, Si（C2H5O）4and sucrose. The Li₂FeSiO₄/Cnanocomposite prepared under different hydrothermal temperature and carboncontent in the control of hydrothermal methods, were in-depth studied by structureand electrochemical methods. The results showed that, when the hydrothermaltemperature is150℃, Material has a smaller particle size, it has higher dischargecapacity and better cycle performance. The Li₂FeSiO₄of12.5%carbon content,particles smaller and more uniform and electrochemical performance is moresuperior. Above all, at the hydrothermal reaction temperature of150℃, with the carbon content of12.5%, the preparaed Li₂FeSiO₄/C has uniform particle andconcentrated in a dozen nano. At0.1C rate, the first charge capacity and dischargecapacity of Li₂FeSiO₄optimized material were140mAh·g^-1and144mAh·g^-1, thecoulomb’s efficiency is more than100%. The discharge capacity is160mAh·g^-1inthe following cycle, The largest discharge capacity is166mAh·g^-1and reach thetheoretical capacity of Li₂FeSiO₄, and the discharge capacity is151mAh·g^-1without decresing the capacity after20cycles. At the same time, material has agood performance rate. At1C rate, the first discharge capacity of Li₂FeSiO₄cathode material is121mAh·g^-1, in30cycles the discharge capacity is110mAh·g^-1. At2C rate, the first discharge capacity of Li₂FeSiO₄cathode material is90mAh g^-1, the discharge capacity is100mAh·g^-1in the following cycle, and thedischarge capacity is93mAh·g^-1after50cycles; At5C rate, the first dischargecapacity of Li₂FeSiO₄cathode material is84mAh·g^-1, the discharge capacity is100mAh·g^-1in the following cycle, and after50cycles the discharge capacity is82mAh·g^-1.