This paper investigates the effects of pretreatment of the MlNi(4.00)Co(0.45)Mn(0.38)Al(0.3) (Ml: Lanthanum rich misch metal) alloy powders in 12 M NaOH solutions with 0.05 M NaBH4 at 110 degrees C for 3 h and the performance of 6 Ah prismatic traction battery. The alloy powders are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy with energy dispersive X-ray detector, inductively coupled plasma-atomic emission spectroscopy, laser particle size analyzer and BET chemisorptions analyzer. The electrochemical performance of the battery was effectively improved by the pretreatment of alloy powders with a NaOH/NaBH4 solution. It is found that the discharge efficiencies at 30C at room temperature and at 3C at -20 degrees C are increased from 5.6% to 88.1% and from 3.7% to 83.7%, respectively. The cycle lifetime at 3C of SOC of 80% is increased from 2200 to 4424. The enhanced performance is attributable to the change of the surface structure and properties of alloy powders by pretreatment. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.