2, Winston Chung Global Energy Center, University of California, Riverside, Riverside, California, United States
3, University of California, Riverside, Riverside, California, United States
LiFePO4 has been proved as a promising cathode material for LIBs because of its cost effective, high thermal stability, environmental friendly, and theoretical capacity of 170 mAh/g. Previously our group demonstrated that LiFePO4 is able to be synthesized in a limited air environment. By doing this, it lowers the requirement of equipment, gas environment, and decrease the synthesis time needed in compare to traditional solid state method. And by applying a closed crucible designed to limit the amount of oxygen participating in the reaction, the quality of produced materials was improved and so decrease the cost of LiFePO4 synthesis. However, the oxidation of the LiFePO4 is still an issue that limit the quality of synthesis. In order to further improve the quality of the LiFePO4, a time study on the synthesis is conducted. In our method, pre-dried iron phosphate (FePO4) and lithium acetate (CH3COOLi) are mixed. The mixture is placed in a sealed crucible and heated in a muffle furnace. The crucible is inserted in to the furnace after it reaches the designed temperature and removed from the furnace once designed heating time is reached to limit the byproduct reaction. Multiple experimental runs are conducted with various heating time to optimize the time needed for the reaction. The time study allows toward the understanding of the reaction evolution, especially the type of the oxide formed during the reaction and the oxidation development base on time. Several techniques are applied to characterize the properties of synthesized LiFePO4. The crystal structure and chemical composition of the synthesized material are characterized by X-ray Diffraction (XRD) and Energy Dispersive Spectroscopy (EDS). The grain size of resulted materials is determined by scanning electron microscopy (SEM). Raman spectroscopy is applied to detect the type of oxidization and oxidization level inside the materials. The synthesized LiFePO4 is assembled into a half coin cell for electrochemical characterization. The cycleability and electrochemical performance of the cells under different C-rates are tested using an Arbin tester.