Graphene oxide nano-sheets wrapped Cu₂O microspheres as improved performance anode materials for lithium ion batteries

Cu₂O microspheres were successfully encapsulated by graphene oxide (GO) nano-sheets and used directly as the anode material for lithium ion batteries. The core-shell structured Cu₂O@GO composite delivered a reversible capacity of 458mAhg-1 at a current density of 100mAg^-1 after 50 cycles. Even at a high charge-discharge rate of 1000mAg^-1, Cu₂O@GO still demonstrated a reversible capacity of 240mAhg-1 after 200 cycles, significantly higher than those of the bare Cu₂O microspheres (37mAhg^-1) and GO nano-sheets (11mAhg^-1). The rate capability evaluated by the ratio of capacity at 100mAg^-1/1000mAg^-1 current density was 49%, 25% and 9.8% for Cu2O@GO, bare Cu₂O and GO, respectively. The greatly enhanced performance for GO nano-sheets wrapped Cu₂O microspheres composite mainly resulted from the synergistic effect of Cu₂O microspheres and GO nano-sheets core-shell composite: the flexible in-situ electrochemically reduced GO nano-sheet coating layer functioning as an efficient three dimensional (3D) conductive network and lithium storage active material; the Cu₂O microsphere core functioning as a skeleton to support multilayer GO sheets and avoid GO nano-sheets aggregation.