Electrochemical Properties of Yolk-Shell-Structured CuO-Fe2O3 Powders with Various Cu/Fe Molar Ratios Prepared by One-Pot Spray Pyrolysis

Several yolk-shell-structured CuO-Fe2O3 powders with various Cu/Fe molar ratios have been successfully prepared under equivalent reaction conditions using a one-pot spray pyrolysis process. The Cu and Fe components are uniformly distributed throughout the powders, irrespective of composition. The Brunauer-Emmett-Teller surface areas of the yolk-shell CuO-Fe2O3 systems increased from 5 to 16m(2)g(-1) if the Cu/Fe molar ratios are decreased from 3:1 to 1:3. The initial discharge and charge capacities of the yolk-shell CuO-Fe2O3 system (Cu/Fe=1:2), showing maximum values at a constant current density of 1000mAg(-1), are 1436 and 1012mAhg(-1), respectively. After 130cycles, the discharge capacities of the yolk-shell CuO-Fe2O3 powders with Cu/Fe molar ratios of 1:3, 1:2, 1:1, 2:1, and 3:1 are 1159, 1151, 755, 655, and 651mAhg(-1), respectively. The discharge capacities of the yolk-shell and dense powder samples after 50cycles, when subjected to a series of current density increases from 500 to 5000mAg(-1), are 735 and 495mAhg(-1), respectively.