PENGARUH pH, SUHU DAN WAKTU PADA SINTESIS LiFePO4/C DENGAN METODE SOL-GEL SEBAGAI MATERIAL KATODA UNTUK BATERAI SEKUNDER LITHIUM; EFFECT OF pH, TEMPERATURE AND TIME ON SYNTHESIS OF LiFePO4 /C BY SOL-GEL METHOD AS CATHODE MATERIAL FOR LITHIUM SECONDARY BATTERIES

Endah Yuniarti, Edi Suharyadi

2013 | Disertasi | PROGRAM STUDI S2 ILMU FISIKA

Cathode material of lithium secondary batteries LiFePO4/C has been synthesized by sol-gel method. Synthesis and carbon coating process are conducted in one stages of heating. The LiFePO4 are synthesized using the powder of Li2CO3, FeC2O4.2H2O and NH4H2PO4. Citric acid has been used as a carbon source in the LiFePO4 cathode material. Synthesis parameters that have been investigated are the acidity (pH), temperature and sintering time. Effect of synthesis parameters on the morphology of LiFePO4 as a cathode material related to the value of electrical conductivity and electrochemical performance has been analyzed. Acidity (pH) value of the precursor was varied by the addition of different amount of distilled water. Obtained variation of the pH value is 5; 5.4, and 5.8. Applied temperature and time of the synthesis prosess are varied, respectively 600, 700 and 800ºC and 6, 8 dan 10 hours. The phase composition of the synthesized cathode material was analyzed by X-Ray Diffractometer (XRD). This analysis result indicates that the dominant phase was formed as LiFePO4. The morphologi of cathode material was analyzed by Scanning Electron Microscopy (SEM). Increasing the value of pH will decrease the grain diameter. Moreover, grain agglomeration occurs with increasing temperature and time of sintering. Specific surface area of the cathode material obtained from the Brunauer Emmett and Teller (BET) test with a value of 7.743 m2/gr is produced by samples with a pH of 5.8 which is sintered at a temperature of 700°C for 10 hours. Electrical conductivity of LiFePO4/C was obtained from the Electrochemichal Impedance Spectroscopy (EIS). This test showed that the highest electrical conductivity of LiFePO4/C obtained at pH 5.8 with sintering temperature of 700°C for 6 hours is 1,842 x 10-3 S/cm. Electrochemical performance of the cell (Li//LiFePO4/C) is strongly influenced by the value of the electrical conductivity of the cathode material. Curve of Cyclic Voltammetry (CV) that show the most redox reactions based on pH range 5, sintering temperature 600 to 800°C for 6 to 8 hours is obtained from sample with a pH of 5.8 which is sintered at a temperature of 700°C for 6 hours.

Kata Kunci : material katoda LiFePO4/C; pH; suhu sinter; waktu sinter; konduktivitas listrik; metode sol-gel; reaksi redoks