Evaluating the optimal cathode material for energy storage devices: a comparative study of LiFePO₄ and LiMnPO₄ using electric impedance

This study investigates the crystalline structure, phase compositions, and electrochemical properties of LiFePO₄, LiFe₀.₅Mn₀.₅PO₄, and LiMnPO₄ cathode materials using thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, and impedance spectroscopy. XRD analysis revealed distinct peaks corresponding to each material, confirming their successful synthesis and high crystallinity. The incorporation of manganese resulted in shifts in peak positions, indicating changes in lattice parameters and unit cell volume. Impedance spectroscopy, conducted over a wide frequency range, showed that LiFePO₄ exhibited the lowest impedance, suggesting superior charge transport and lower resistance, while LiMnPO₄ showed the highest impedance, indicating greater resistance and potential challenges. LiFe₀.₅Mn₀.₅PO₄ displayed intermediate impedance characteristics. The Cole–Cole diagrams highlighted these differences, with LiFePO₄ demonstrating the smallest semicircular arc, indicating lower charge transfer resistance, while LiMnPO₄ exhibited the largest arc. The findings suggest that LiFePO₄ is the most efficient material for energy storage applications, while LiMnPO₄ requires optimization to improve its performance.