In this paper, the performance of metal hydride electrodes prepared with different amounts of tricobalt tetraoxide (Co3O4) and AA size cylindrical Ni-MH battery with the capacity of 1500 mAh prepared with Co3O4 as negative additive has been investigated. The investigation reveals that the charge and discharge efficiency at 1400 mA g(-1) at room temperature, and the discharge efficiency at 140 mA g(-1) at -20 degrees C of metal hydride electrode are increased from 82.2% to 92.4%, from 55.1% to 84.7%, and from 30.2% to 68.8%, respectively, by adding proper amounts of Co3O4. Furthermore, it is also found that the high-rate and low-temperature discharge ability, overcharge endurance ability, cycle life, inner pressure of battery are greatly improved by adding Co3O4. These results can be attributed to the high electrocatalytic activity and extended hydride storage capability of Co3O4, the improvement of gas consumption ability and the restraining of oxidation of electrode alloys by adding Co3O4. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.