Cubic CuFe2O4 (c-CuFe2O4) and tetragonal CuFe2O4 (t-CuFe2O4) nanoparticles were selectively prepared using a facile one-step solid state reaction route by ferrous oxalate and copper acetate as the reactants. As an anode material for Li-ion batteries, compared with c-CuFe2O4 and t-CuFe2O4 synthesized at 800 degrees C, c-CuFe2O4 synthesized at 400 degrees C with smaller particle size and larger surface area exhibited superior discharge capacities and better cycling performance (950 mAh g(-1) at 100 mA g(-1) after 60 cycles), and higher rate capability. The influence of the two crystal phases on the electrochemical performance were only exhibited at the Li+ insertion process during the first discharge. The average particle size and the surface areas play an important role in effecting the lithium-ion storage capability and cycling ability. Through ex situ HRTEM analysis, we observed the existence of metastable FexCu1-x alloy in the discharged nanocomposition for the first time, which exhibits the interaction of metallic Cu particles with the adjacent iron ions. (c) 2013 Elsevier Ltd. All rights reserved.