Effect of Heat Treatment on Structure and Electronic Conductivity of LiFePO4 Composites Containing Activated Carbon derived from Oil Palm Shell

Oil-palm-shell-derived activated carbon was investigated as a conductive carbon component in LiFePO4 (LFP) composites. The carbon precursor was prepared by carbonization followed by KOH activation. Commercial LFP was mixed with carbon, dried at 80 °C, and either used as an unsintered control or heat-treated under argon. X-ray diffraction showed that the main olivine LFP structure was retained after carbon addition and heat treatment, with only small changes in the refined lattice parameters. Scherrer analysis gave apparent crystallite sizes of 42.6, 43.4, 31.6, and 31.0 nm for LFP/C-80, LFP/C-350, LFP/C-550, and LFP/C-750, respectively. SEM-EDS showed irregular and agglomerated particles, while FTIR retained the characteristic phosphate bands of LFP. The reported four-point-probe conductivities were 3.9 × 10⁻⁵, 5.1 × 10⁻⁵, 4.9 × 10⁻⁵, and 4.6 × 10⁻⁵ S cm⁻¹ for LFP/C-80, LFP/C-350, LFP/C-550, and LFP/C-750, respectively, compared with 2.9 × 10⁻⁷ S cm⁻¹ for unmodified LFP. These results show that the addition of oil-palm-shell-derived activated carbon increases the solid-state electronic conductivity of LFP while the main LFP crystal structure is preserved. Within the reported dataset, the conductivity varies only moderately among the carbon-containing samples, showing that heat treatment affects the composite but does not produce a simple monotonic improvement with temperature.