Chiang Mai Journal of Science

     This study investigates the synthesis of Lithium Iron Phosphate (LFP) with NMC-doped cathode materials, aiming to enhance the performance of lithium-ion batteries. The NMC content was varied from 0.02 to 0.10wt%, and 1wt% of (NH4)₃PO₄ was added to all conditions to prevent phosphate loss during the calcination process. The composite powder was prepared using a straightforward mixed oxide method, with a calcination temperature of 600 °C for 5 hours under an argon gas flow. X-ray diffraction (XRD) analysis confirmed the successful formation of pure LFP with an orthorhombic crystal structure, devoid of any secondary phases. To further explore the impact of NMC doping on the structural characteristics, FTIR and Raman spectroscopy were employed. Results revealed that increasing NMC doping concentration beyond 0.02wt% led to the broadening of the PO₄³⁻ symmetric stretching band at approximately 947 cm⁻¹, indicating a higher degree of disorder in the LFP structures. This disorder was found to adversely affect electrochemical performance, resulting in decreased discharge capacity and increased impedance, as determined by electrochemical impedance spectroscopy (EIS), with higher concentrations of NMC and (NH4)₃PO₄. Scanning Electron Microscopy (SEM) analysis unveiled the presence of agglomerated particles ranging in size from 0.5 to 0.9 microns. Optimal conditions were identified with the addition of NMC doped at 0.02wt%, which exhibited a discharge capacity of approximately 119.41 mAh/g at 0.2 C, along with a low impedance of 200 Ohm. Moreover, the 0.02wt% sample demonstrated a promising linear trend in cycle performance, suggesting its potential for future applications in lithium-ion batteries.