Development of zinc-ion battery cathodes with vanadium dioxide-based materials

Zinc ion batteries have attracted great interest due to their environment-friendliness, non-toxic, good safety, low-price, and abundant metallic Zn resources, possessing extensive application in the fields of energy-storage devices, high-energy batteries, and the large-scale electric grid. Aqueous ZIBs use mildly acidic electrolyte solutions, so they can be fabricated under ambient conditions without the need for a glovebox or high-purity organic solvents, so the scalable production of ZIBs is very rapid and cost-effective compared to other battery technologies. As a secondary rechargeable battery, Zn ion batteries usually use metallic Zn as the anode and vanadium/manganese-based or Prussian blue analogous compounds as the cathodes. Thus, exploring a capable cathode could remarkably enhance the electrochemical performance of Zn ion batteries. Vanadium-based oxides would be suitable as cathodes for Zn ion batteries owing to the multi-valence of vanadium element. However, vanadium oxides suffer a low electronic conductivity, unsatisfactory cycling performance, and poor rate ability, hindering their application in Zn ion batteries. Among various vanadium-based oxides, the monoclinic phase of vanadium dioxide (VO2 (M)) has a metal-insulator-transition (MIT) property, and it is converted to rutile phase ((VO2 (R)) around 68 oC. Thanks to the MIT property, the conductivity of VO2 is significantly increased, and the electrochemical properties are also improved. In this work, high performance ZIB devices with VO2-based cathodes were fabricated and characterized. The fabricated ZIBs had improved electrochemical energy storage properties due to the MIT feature of VO2 cathodes. Vanadium dioxide based materials and their graphene oxide composites that were synthesized via low-cost and solution-based methods to be used in aqueous ZIBs to show distinct advantages, which was the main subject of this thesis. In this regard, heat-activated VO2 and their graphene oxide composites were used in high performance cathodes and aqueous Zn-ion battery devices.