The positive electrodes of nickel metal hydride (NiMH) batteries were doped with Al to improve the discharge capacity of NiMH batteries and its effects on the electrode performance were studied. Al-doped alpha-Ni(OH)(2) electrodes were prepared by co-precipitation method. The characteristics of the positive electrode in KOH solution were investigated with charge/discharge cycles. The elution of doped Al into the electrolyte was observed as the number of charge/discharge cycles increased, which was confirmed by the ICP-AES analysis of the electrolyte after repeated charge/discharge cycles. This subsequently led to the decrease in the discharge capacity. However, it was found that the addition of Al ions into the electrolyte stabilized alpha-Ni(OH)(2) and resulted in the increased discharge capacity.