Hollow Cobalt Selenide Microspheres: Synthesis and Application as Anode Materials for Na-Ion Batteries

Abstract

The electrochemical properties of hollow cobalt oxide and cobalt selenide microspheres are studied for the first time as anode materials for Na-ion batteries. Hollow cobalt oxide microspheres prepared by one-pot spray pyrolysis are transformed into hollow cobalt selenide microspheres by a simple selenization process using hydrogen selenide gas. Ultrafine nanocrystals of Co3O4 microspheres are preserved in the cobalt selenide microspheres selenized at 300 degrees C. The initial discharge capacities for the Co3O4 and Cobalt selenide microspheres selenized at 300 and 400 degrees C are 727, 595, and 586 mA h g(-1), respectively, at a current density of 500 mA g(-1). The discharge capacities after 40 cycles for the same samples are 348, 467, and 251 mA h g(-1), respectively, and their capacity retentions measured from the second cycle onward are 66, 91, and 50%; respectively. The hollow cobalt selenide microspheres have better rate performances than the hollow cobalt oxide microspheres.