The progress in lithium-ion battery (Li-ion) technology is crucial to addressing the increasing energy needs of modern society. This research examines the impact of doping nickel-manganese-cobalt oxide (NMC811) electrodes with varying concentrations of Al(OH)3 on the electrochemical performance of Li-ion batteries. Through a systematic experimental approach, the study analyzes how different Al(OH)3 dopant levels affect morphology, crystal structure, and battery performance. The results show notable improvements in capacity retention and cycling stability, which are attributed to better structural stability and ion diffusion kinetics. The research indicates that aluminum-doped NMC811 outperforms undoped NMC811 in retention capacity. Specifically, NMC811 with 2.5% Al exhibits the highest retention capacity at 76.19%, compared to 57.74% for the undoped variant. The addition of Al(OH)3 enhances the reversibility of the redox reaction, as demonstrated by the smaller difference in the redox potential peak in the CV measurement curve. The NMC811-2.5% Al sample shows the smallest redox peak potential difference of 1.81  V, while the undoped NMC811 has a larger difference of 2.25  V. According to EIS measurements, the NMC811-2.5% Al sample achieves the highest ionic conductivity of 0.0096 S/cm, corresponding to the lowest cation mixing value with a peak ratio of I(003)/I(104) of 1.36. Insights from this study offer valuable guidelines for enhancing the performance of high-performance NMC811 cathodes.