New three-dimensional electrode structure for the lithium battery: Nano-sized γ-Fe2O3 in a mesoporous carbon matrix

► We have developed a new iron-based electrode for lithium battery with inexpensive and low environmental impact. ► A new electrode structure was introduced to improve the charge-discharge characteristics of iron oxide using a three-dimensional mesoporous carbon matrix. ► Nanoparticles of iron oxide (γ-Fe2O3) were introduced into the mesopores of a carbon matrix by oxidizing metallic iron, and the composite electrode showed the first discharge capacity of 1100 mAh g−1. ► The reaction mechanism of the composite electrode is discussed.