Rational design/fabrication of metal oxide/metal composite arrays is critical for construction of advanced energy storage devices. Herein, we assemble ultrathin Co shell on the preformed Co3O4 nanowires core forming porous Co3O4@Co core shell arrays. In such a composite structure, nanowire arrays possess open spaces for shorter ion diffusion length, while ultrathin metal Co shell has high electronic conductivity for fast electron transfer. As an anode of lithium ion batteries, enhanced Li ion storage properties have been demonstrated for the Co3O4@Co composite nanowire arrays. At a high current density of 3 A g(-1), the specific capacity of Co3O4@Co electrode is up to 642 mAhg(-1), which is much higher than that (440 mAhg(-1)) of the pristine Co3O4 nanowires electrode. These results indicate that conformal deposition of ultrathin metal shell can efficiently enhance the Li ion storage performance of metal oxides. (C) 2016 Elsevier Ltd. All rights reserved.