Superior Lithium-Ion Storage Properties of Mesoporous CuO-Reduced Graphene Oxide Composite Powder Prepared by a Two-Step Spray-Drying Process.

Mesoporous CuO-reduced graphene oxide (rGO) composite powders were prepared by using a two-step spray-drying process. In the first step, hollow CuO powders were prepared from a spray solution of copper nitrate trihydrate with citric acid and were wet milled to obtain a colloidal spray solution. In the second step, spray drying of the colloidal solution that contained dispersed GO nanosheets produced mesoporous CuO-rGO composite powders with particle sizes of several microns. Thermal reduction of GO nanosheets to rGO nanosheets occurred during post-treatment at 300 °C. Initial discharge capacities of the hollow CuO, bare CuO aggregate, and CuO-rGO composite powders at a current density of 2 A g(-1) were 838, 1145, and 1238 mA h g(-1) , respectively. Their discharge capacities after 200 cycles were 259, 380, and 676 mA h g(-1) , respectively, and their corresponding capacity retentions measured from the second cycle were 67, 48, and 76 %, respectively. The mesoporous CuO-rGO composite powders have high structural stability and high conductivity because of the rGO nanosheets, and display good cycling and rate performances.