Coaxial Fe₃O₄/CuO hybrid nanowires as ultra fast charge/discharge lithium-ion battery anodes

We report the facile, template free electrochemical fabrication of hierarchical Fe₃O₄/CuO hybrid wires, grown directly on a copper substrate. The electrodes are produced by the electrochemical deposition of Fe₃O₄ on CuO nanoneedle arrays, fabricated by anodization. The Fe₃O₄/CuO hybrid anodes displayed ultrafast charging/discharging properties and high rate capabilities, superior to those of their individual building blocks Fe₃O₄ and CuO. For example, at a current density of 820 mA g^-1, the Fe ₃O₄/CuO hybrid wires delivered high reversible specific capacity, good cycling stability (delivering 953 mA h g^-1 discharge capacity with 98.7% Coulombic efficiency after 100 cycles) and excellent rate capability (319 mA h g^-1 at 8200 mA g^-1). The excellent performance of the Fe₃O₄/CuO hybrids comes from the intelligent integration of the two compatible components into unique hierarchical architectures with a high specific capacity, with one-dimensional CuO nanoneedle arrays electrochemically coated with mesoporous Fe ₃O₄ nanocubes.