Sodium-ion batteries are generating considerable interest for large-scale energy storage systems and electric vehicles. However, high energy density cathodes often show low power due to poor kinetics and rate capability. The primary cause is large ionic radius of Na+ ion that provide high kinetic barrier to Na+−ion transport. The β−NaMnO2 show high discharge capacity but fails to retain long range order during sodium extraction that prevents it from fast charging. Here, we report successful aluminium doping of 4 and 11% to the parent structure to mitigate this problem. The β−NaMnO2 shows capacity retention of only 41% after 35 cycles when cycled at 1C−rate. On the contrary, aluminium doping of 4 and 11% shows capacity retention of about 76% and 80.4%, respectively after 50 cycles. The designed material, β−NaMn0.96Al0.04O2, can deliver a discharge capacity of 139 mAh g−1. These values demonstrate an excellent electrochemical reversibility at high rate. The density functional theory based analysis shows that aluminium doping increases bond length of Mn−O and a decrease bond length of Al−O. This increases the overall volume of the structure and facilitates free access to the sodium ions without significant distortion.