Effects of Valence States of Working Cations on the Electrochemical Performance of Sodium Vanadate

Supercapacitors have received much attention as large-scale energy storage devices for high power density and ultralong cycling life. In this work, sodium vanadate Na0.76V6O15 /poly(3,4-ethylenedioxythiophene) (PEDOT) nanocables with deficient bridge oxygen at the interface (denoted Vo(center dot center dot)-PNVO) have been tailored for supercapacitors through the in situ polymerization of 3,4-ethylenedioxythiophene and studied using three different electrolytes. Experiments and theoretical calculations reveal that all Na+, Zn2+, and Al3+ ions appear as hydrates in aqueous solutions but insert into the crystal structure as Na+ ions and Zn2+-H2O and Al3+-H2O hydrates, respectively. In comparison with the Zn2+-H2O and Al3+-H2O hydrates, Na+ ions with a smaller radius diffuse more quickly in Vo(center dot center dot)-PNVO. Thus, Vo(center dot center dot)-PNVO delivers better charge storage capability and stability when an electrolyte with Na+ ions is used. The results strongly suggest that an electrostatic interaction is significant in determining transport properties and storage capacities, rather than hydrate radii or valence states.

Automated summary

This study focuses on the preparation and investigation of nanomaterials tailored for supercapacitors. It is found that Na+ ions exhibit faster diffusion in the nanomaterials, leading to better charge storage capability and stability.