Redox Charge Transfer Kinetics and Reversibility of VO2 in Aqueous and Non-Aqueous Electrolytes of Na-Ion Storage

The deep understanding about the electrochemical behavior of the nanostructured electrode in electrolytes provides crucial insights for the rational design of electrode for sodium (Na)-ion storage system (NIS). Here, we report redox charge transfer kinetics and reversibility of VO2(B) nanorod electrodes in both aqueous and organic electrolytes for NIS. The as-synthesized VO2(B) nanorods show the reversible redox reaction with the higher specific and rate capacitances at high current density in aqueous electrolytes than in organic electrolytes. Temperature-dependent impedance measurements demonstrate the more facile interfacial charge transfer of Na ions into VO2(B) nanorods in aqueous electrolytes. The reversible evolution in oxidation state and chemical composition of VO2(B) nanorods is observed in aqueous electrolytes, as confirmed by ex situ XRD and ex situ X-ray photoelectron spectroscopy analyses. Given by the facile and reversible pseudocapacitive feature, the electrochemical performances of VO2(B) nanorods are further improved by constructing the hierarchical structure of the reduced graphene oxide-VO2 composite for aqueous Na+ ion storage.

Automated summary

The reversible redox charge transfer kinetics and reversibility of VO2(B) nanorod electrodes in both aqueous and organic electrolytes for Na-ion storage system were investigated. It was found that the VO2(B) nanorods demonstrated higher specific and rate capacitances in aqueous electrolytes than in organic electrolytes. Moreover, the temperature-dependent impedance measurements indicated a more facile interfacial charge transfer of Na ions into VO2(B) nanorods in aqueous electrolytes.