本研究將改善傳統水熱法的缺點,以微波溶劑熱法製備LiFePO4正極材料。因微波法具有:(1)反應速率較快 (2)溫和的反應條件 (3)較高的化學純度 (4)使用較低的能量 (5)不同反應的選擇性。 實驗中,採用一步合成與二步合成製備LiFePO4的前驅物,以氫氧化鋰、硫酸亞鐵、磷酸為起始物,反應的溶劑則選用乙二醇,利用乙二醇在微波系統中進行合成反應。並研究一步合成與二步合成這二種實驗方法之微波的功率、時間、溫度、合成環境探討之間的關係,以SEM、XRD、TEM 及SEM/EDX觀察其表面型態、結晶構造及分析晶格是否缺陷。 根據實驗結果可知,一步合成及二步合成在微波條件為600W-200W、180℃、N2環境下,時間分別為20分鐘與80分鐘可分別合成出LiFePO4正極材料。再以導電高分子PEDOT包覆至LiFePO4正極材料裡改質,最後以四點探針測試其導電度,發現以PET(含量較高的poly3,4-ethylenedioxythiophene;PEDOT)效果最好。
This project will improve the disadvantage of conventional hydrothermal method, to prepare LiFePO4 powder by microwave solvothermal. we use microwave to prepare because it has several characteristics: (1) faster reaction rate, (2) milder reaction conditions, (3) higher chemical yield, (4) lower energy consumption, (5) better reaction selectivities. Experiment, the precursors of LiFePO4 were synthesized by precipitation named one step synthesis and two steps synthesis separately. The source of lithium hydroxide, ferrous sulfate, phosphoric acid as a synthetic raw material. Using ethylene glycol as solvent that used to conduct reaction in the microwave system and studying the relationship between microwave power, time, temperature and synthetic environment of one-step and two-steps synthesis methods separately. We explore the form, the crystalline phases and analysis of lattice defects by SEM, XRD ,TEM and SEM/EDX. According to the experiments, we found that one-step and two-steps synthesis methods separately in the microwave conditions for the 600W-200W, 180 ℃, N2 system, and the microwave time was 20min and 80min respectively synthesized LiFePO4 cathode material, And then, the conductive polymer is coated LiFePO4 cathode material. Finally, Four-point probe to test its conductivity. We found that PET (high content of poly 3,4-ethylenedioxythiophene, PEDOT) is the best.