Improved electrochemical performances of core-shell Cu2O/Cu composite prepared by a simple one-step method

Core-shell Cu2O/Cu composites were successfully prepared by over-reduction of aqueous CuSO4 with hydrazine hydrate as reductant. Field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) clearly illuminate that the core is Cu2O with 400 nm in diameter, and the shell is Cu with about 50 nm in thickness. The core-shell Cu2O/Cu exhibited weaker polarization and higher coulombic efficiency than pure octahedral Cu2O, especially in the initial stage of cycles. After 50 cycles, the reversible capacity of Cu2O/Cu (360 mAh g(-1)) was much higher than that of pure Cu2O (160 mAh g(-1)). The improvement of electrochemical properties is attributed to the core-shell structure of Cu2O/Cu and the catalytic effect of Cu on the decomposition of Li2O during the charging process. (C) 2008 Elsevier B.V. All rights reserved.