Current collectors are typically electrochemically inactive in lithium ion batteries. However, they might affect the whole cell performance once they are thermally treated during battery assembly procedure. The goal of this study is to investigate the heat treatment effect of Ni foam current collectors on the electrochemical performance in lithium ion batteries. Ni foams were thermally treated at different temperatures in air, and they were characterized in terms of morphology, structure and electrochemical performance in a half cell. SEM images showed that Ni foam surface became coarse with an increase of the heating temperature. Thermally treated Ni foams below 200 degrees C had negligible capacity of about 0.025 mAh, but above 300 degrees C showed certain capacity up to 3.13 mAh at 30th cycles due to the oxide layer formed by the thermal oxidation of the Ni foam. The results demonstrate that the thermal treatment of Ni foam current collector promotes the gradual oxidation on the Ni foam surface with nonnegligible capacity contribution. (C) 2011 Elsevier B.V. All rights reserved.