Enhancing the Electrical Performance of LiNi_0.65Co_0.3Al_0.05O₂ Oxide Cathode by Substituting Mn for Co

Nickel-rich layered oxide cathodes have emerged as leaders in next-generation lithium-ion batteries (LIBs), offering high energy density while reducing reliance on cobalt. However, challenges such as cation mixing, structural fatigue, and poor capacity retention persist. Most studies conducted to date have focused on higher Ni amounts (Ni ≥ 0.8) in the stoichiometry thus leaving smaller rooms for Mn and Co, which makes their tuning impacts minimal and challenging to examine. In this study, we systematically fine-tuned manganese (Mn) substitution in LiNi_0.65Co_0.3-xMn_xAl_0.05O₂ (x = 0-0.3) cathodes to optimize these limitations. Increasing Mn increased the c parameter of the crystals, decreased particle size, introduced plausible covalency alterations at the surface and antisite disorder, which strongly correlate with the electrochemical behavior of the series of cathode materials prepared. While Energy Dispersive X-ray spectroscopy (EDX) suggested a uniform distribution of elements, the local distribution, as confirmed by Electron Energy Loss Spectroscopy (EELS) analysis, revealed enrichment of Mn at the surface of the particles. The sample with x = 0.1 demonstrated an optimal balance of structural integrity and Li-ion diffusion kinetics (GITT), and delivered the highest capacity retention (≈87% after 100 cycles at 1C) among all the compositions.