In this study an investigation has been conducted on the effect of reduced graphene oxide (rGO) coating on increasing the value of Lithium Ferro Phosphate (LFP) electrical conductivity. This coating process uses a variation of the mass ratio of LiFePO4/rGO by 90%:10%, 70%:20%, and 67%:33%. The LiFePO4 precursor was prepared using the sol-gel rute from the main commercial materials, namely Li2CO3 powder as a source of lithium ions, FeCl2.4H2O as a source of iron and NH4H2PO4 powder as a phosphate source. As for the coating used rGO extracted from coconut shell waste. The samples were calcined with temperature variations of 600°C, 650°C and 700°C in an argon environment for 10 hour. The phase purity and crystal structure of LiFePO4 were analyzed using XRD. The analysis of data from XRD was done using the the Match!, Rietica, and MAUD software. Based on the results of XRD analysis, LiFePO4 with high purity and good crystallinity was obtained when the sample was calcined at temperature of 700°C. The results of the MAUD analysis show that the best size of LiFePO4 crystal is 86,54 nm. LiFePO4/rGO nanocomposite was successfully synthesized by mechanical ultracentrifugation method. The characterization of the value of electrical conductivity, carried out using a four-point probe. The results show that the greater the percentage of rGO, the higher the value of electrical conductivity. The mass ratio of 67% LiFePO4 and 33% rGO shows an increment in good conductivity values, from the original order of 10-8 S/cm to the order of 10-4 S/cm.
In this study, an rGO – like carbon (C) compound was synthesized from coconut shell (biomass), and inserted into LiFePO4 (LFP), as Li-ion battery cathode. Thus, an LFP/C nanocomposite was successfully fabricated using a combination of the sol-gel technique and mechanical ultracentrifugation. LiFePO4 precursors were prepared from commercial starting materials, using the sol-gel technique, and the composites’ carbon weight content was varied between 15% and 30%. Subsequently, the microstructural characteristics and electrochemical properties as cathode for Li-ion batteries were measured. In addition to exhibiting higher electrical conductivity, the synthesized LFP/C nanocomposite showed higher capacity and better cycle capability. Also, the nanocomposite cathode showed a specific capacity of 128 mAhg-1 in the first cycle, and a retention capacity of 75% after 10 cycles, at room temperature and a rate of 0.1 C. The enhanced electrical conductivity and electrochemical performance of the samples prepared are believed to be due to three-dimensional conduction network formed by the rGO like carbon sheets, as observed by electron microscopy.
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