Superior electrochemical performances of double-shelled CuO yolk–shell powders formed from spherical copper nitrate–polyvinylpyrrolidone composite powders

Abstract

Spherical copper nitrate–polyvinylpyrrolidone (PVP) composite powders coated with a copper nitrate hydroxide [Cu₂(OH)₃NO₃]–carbon composite are prepared by a one-pot spray pyrolysis process. In this, Cu₂(OH)₃NO₃ and carbon are formed by dehydration of copper nitrate and carbonization of PVP, respectively. Thermal decomposition of the composite powders is then performed at 300 °C under an air atmosphere, producing the final yolk–shell-structured CuO powders. The electrochemical properties of these powders are then compared with those of commercial CuO nanopowders. The discharge capacities of the CuO yolk–shell powders and the commercial CuO nanopowders after 240 cycles at a current density of 500 mA g⁻¹ are 590 and 302 mA h g⁻¹, respectively. Furthermore, the discharge capacity of the CuO yolk–shell powders is as high as 615 mA h g⁻¹, even after 1000 cycles at a current density of 1000 mA g⁻¹. Electrochemical impedance spectroscopy reveals that the structural stability of the CuO yolk–shell powders during cycling lowers the charge transfer resistance, and thereby improves the lithium ion diffusion rate.