Formation of core–shell-structured Zn2SnO4–carbon microspheres with superior electrochemical properties by one-pot spray pyrolysis

Abstract

Core–shell structured Zn₂SnO₄–carbon microspheres with different carbon contents are prepared by one-pot spray pyrolysis without any further heating process. A Zn₂SnO₄–carbon composite microsphere is prepared from one droplet containing Zn and Sn salts and polyvinylpyrrolidone (PVP). Melted PVP moves to the outside of the composite microsphere during the drying stage of the droplet. In addition, melting of the phase separated metal salts forms the dense core. Carbonization of the phase separated PVP forms the textured and porous thick carbon shell. The discharge capacities of the core–shell structured Zn₂SnO₄–carbon microspheres for the 2^nd and 120^th cycles at a current density of 1 A g⁻¹ are 864 and 770 mA h g⁻¹, respectively. However, the discharge capacities of the bare Zn₂SnO₄ microspheres prepared by the same process without PVP for the 2^nd and 120^th cycles are 1106 and 81 mA h g⁻¹, respectively. The stable and reversible discharge capacities of the Zn₂SnO₄–carbon composite microspheres prepared from the spray solution with 15 g PVP decrease from 894 to 528 mA h g⁻¹ as current density increases from 0.5 to 5 A g⁻¹.