Yolk-Shell, Hollow, and Single-Crystalline ZnCo2O4 Powders: Preparation Using a Simple One-Pot Process and Application in Lithium-Ion Batteries

The electrochemical properties of yolk-shell-structured, multi-component, transition-metal oxides have not yet been properly compared to those of hollow-structured or nanoscale powders. In this study, yolk-shell, hollow, and single-crystalline ZnCo2O4 powders with uniform compositions are prepared by using simple gas-phase reaction methods. Double-shelled ZnCo2O4 yolk-shell powder is prepared directly from the spray solution by using spray pyrolysis. Single-crystalline ZnCo2O4 nanopowder is prepared by means of flame spray pyrolysis. The yolk-shell ZnCo2O4 powder shows higher charge and discharge capacities than the hollow and single-crystalline powders. The yolk-shell, hollow, and single-crystalline ZnCo2O4 powders deliver discharge capacities of 753, 586, and 206mAhg(-1), respectively, after 200 cycles at a charge/discharge rate of 3Ag(-1), and the corresponding capacity retentions measured after the first cycle are 99, 74, and 27%, respectively. The yolk-shell ZnCo2O4 powders are structurally stable during cycling and have good electrochemical properties even at high current densities.