A new electrode structure based on a three-dimensional mesoporous matrix was developed. Nanoparticles of γ-iron oxide (Fe2O3) were introduced into the mesopores of a carbon matrix (mesoporous carbon, CMK-3) by oxidizing metallic iron, which was electroplated in the matrix. The resulting structure was found to have a high charge–discharge capacity when used as the positive electrode of a lithium battery. The iron oxide nanoparticles bonded tightly to the electrically conductive electrode framework, and showed a high activity for the electrochemical reaction: Fe2O3 +6Li→3Li2O+2Fe.