Fabrication of high-performance supercapacitors based on hollow SnO₂ microspheres

Abstract

Hollow SnO₂ microspheres are prepared from resorcinol–formaldehyde gel and different tin compound precursors, including stannous sulfate (SnSO₄), stannous chloride dihydrate (SnCl₂·2H₂O), and stannic chloride pentahydrate (SnCl₄·5H₂O) via chemically induced self-assembly in hydrothermal environment. Morphological and structural characterizations of as-prepared hollow SnO₂ microspheres are carried out using scanning electron microscopy, X-ray diffraction, and nitrogen adsorption–desorption method. Their electrochemical properties as the supercapacitor electrode materials for application are also investigated using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurement in 1 M H₂SO₄ electrolyte. There are redox peaks in CV curves and a large number of Faradic plateaus in GCD curves. At different scan rates, all the obtained samples have excellent electrochemical properties. The hollow SnO₂ microspheres obtained from SnSO₄ and SnCl₂·2H₂O as precursors show relatively lower specific capacitances of 395 and 347 F g⁻¹, respectively. However, the specific capacitance of SnO₂ from SnCl₄·5H₂O is up to 663 F g⁻¹. The high specific surface area and hollow structure of SnO₂ microspheres are due to facilitating the rapid transport of electrolyte ions and improving the electrochemical performance. It is expected that hollow SnO₂ microspheres are the promising redox supercapacitor materials.