Investigation of thermal, structural, vibrational spectroscopic and optical properties of LiNi0.45A0.05Mn1.475Al0.025O4 (A = Mg, Zn, and Cu) cathode materials

Abstract spinel LiNi0.45A0.05Mn1.475Al0.025O₄ (LNMA) cathode materials doped with Mg, Zn and Cu were synthesized via the solid state route. The thermal, structural, vibrational, and optical properties of LiNi0.5Mn1.475Al0.025O₄ (LNMA), LiNi0.45Mg0.05Mn1.475Al0.025O₄ (LNMA-Mg), LiNi0.45Zn0.05Mn1.475Al0.025O4 (LNMA-Zn), and LiNi0.45Cu0.05Mn1.475Al0.025O₄ (LNMA-Cu) materials investigated. The X-ray diffraction (XRD) analysis revealed that all the prepared cathode materials exhibited a cubic spinel structure with disordered Fd-3m space group. Doping with Mg, Zn and Cu cations resulted in a more disordered cation distribution in the LNMA lattice, which is beneficial for enhancing electronic conductivity and electrochemical properties. The average crystallite size were found in (44.32 to 47.68 nm). And Rietveld refinement of XRD data confirmed the high crystallinity of the investigated materials. Fourier transform infrared (FTIR) and Raman spectroscopies identified absorption peaks associated with Mn-O and Ni-O bond vibrations, further supporting the cubic spinel structure with a minor P4₃32 phase. All synthesized cathodes amterials exhibited optical absorption in visible range, as evidenced by luminescence spectroscopy(PL) and Ultraviolet visible spectroscopy(Uv-Visible) spectra. The calculated optical bandgap energies were 1.85, 1.83, 1.78 1nd 1.73 for LNMA, LNMA-Mg, LNMA-Zn and LNMA-Cu, respectively.