Study On The Synthesis And Electrochemical Performances Of LiFePO₄

On the basis of past research, in this thesis the LiFePO₄was synthesized bysolid-phase and precipitation method, compared the electrochemical performance of thematerials synthesized in different conditions, and optimized the synthesis process. Todetermine the optimal preparation plan, the X-ray diffraction analysis and LPSA wereused to analysis the structure of the materials and particle sizes synthesized in variousconditions, and DC-5battery charging and discharging tester was used to test theelectrochemical properties.In the solid-phase method, fully grinding the mixture to make sure it mixinguniformity, the mixed precursor body was sintering with inert atmosphere in tubefurnace to synthetize the LiFePO₄. The experiments were studied the electrochemicalperformance of the materials synthetized by Different sintering temperature anddifferent sintering time. The results show that in join applicable glucose as reductionmaterial, the material have the best electrochemical performance when the materialsintering6h under the temperature of700℃，the material was in charge and dischargecurrent of0.3C, initial cycle of discharge capacity was123.7mAh/g, after the fourthcycle the discharge capacity can reach145.9mAh/g..FePO4was first compounded by the reaction of FeSO₄·7H₂O and NH₄H₂PO₄aqueous solution when the LiFePO₄was synthetized by the Hydrogen peroxideoxidation precipitation method. The presoma was firstly by H₂O₂take the bivalent ironoxide as three price iron, then the three price iron and PO₄^3-reaction generated FePO4precipitation. The Best Reaction Condition of the LiFePO₄material is under the carboncontent of7percent roasts6hours in650centigrade in the tube furnace. The LiFePO₄preparated in the most optimal conditions has higher Charge and discharge specificcapacity, and have better cycle performance and rate performance. The material was incharge and discharge current of0.3C, initial cycle of discharge capacity was163mAh/g,after the thirtieth cycle the discharge capacity can reach159.4mAh/g, after the sixtiethcycle the discharge capacity can reach more then146mAh/g. When the current reached1C, the highest discharge capacity can reach141.8mAh/g.