Improving the electrochemical performance of lithium-rich layered oxide (LRMO) cathode materials is a significant challenge for next-generation lithium-ion batteries. This study illustrates the capacity of Al2O3 coating to improve the electrochemical performance of Li1.2Ni0.35Mn0.35O2, utilizing the dry coating method with varying concentrations (0–2000 ppm). The findings indicate that a coating concentration of 1000 ppm yields the most favorable outcomes, exhibiting a maximum capacity retention of 91.12%, in contrast to the uncoated cathode, which retains only 89.82% after 100 cycles. The discharge capacity is superior at 208.37 mAh/g, in contrast to the uncoated cathode’s 202.32 mAh/g. This aligns with the EIS results, which indicate the lowest resistance (Rs 2832 Ω, Rct 38.14 Ω) and the highest diffusion coefficient (1.16 × 1012 cm2s−1). Together with |ΔV| being the smallest value (0.286 V) compared to other concentrations. The coating technique is efficiently executed on a large scale and at a comparatively low cost. Consequently, the future demand for substantial energy may be adequately fulfilled.