The Effect of Reduced Graphene Oxide (rGO) Coating on Electrical Conductivity of Lithium Ferro Phosphate (LFP) as an Alternative Cathode for Li-ion Battery

Abstract

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 powder 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 600oC, 650 oC and 700 oC within 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 a temperature of 700oC. 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, it is carried out using a four-point probe. The results of the analysis 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 increase in good conductivity values, from the original order of 10-8 S/cm to the order of 10-4 S/cm. Keywords: LiFePO4, nanoparticle, reduced graphene oxide (rGO), sol-gel method