Self-assembled vanadium-graphene hydrogels for high-capacity aqueous zinc-ion batteries.

Abstract

This work presents a novel strategy for synthesizing vanadium-oxide-based cathode materials for zinc-ion batteries. The synthesis begins with the preparation of a vanadium-graphene hydrogel via hydrothermal reduction of a graphene oxide dispersion containing vanadyl sulfate. In a subsequent hydrothermal step, the resulting vanadate species are converted into hydrated vanadium pentoxide. The obtained vanadium pentoxide-graphene hydrogel composites are thoroughly characterized in terms of their structural and electrochemical properties. At a current density of 0.1 A g^-1, normalized to the entire cathode mass, the material delivers an impressive discharge capacity of 502 mAh g^-1. When normalized to the electroactive vanadium pentoxide content, this value increases to around 670 mAh g^-1. This exceptional performance arises not only from the reversible intercalation of zinc ions into vanadium pentoxide but also from concurrent proton intercalation and the capacitive contribution of the high-surface-area graphene host material.