Electrochemical Performance of Oxygen Vacancies Enhanced Transition Metal Oxides in Supercapacitor

As electrode materials for supercapacitors, transition metal oxides have some advantages of high theoretical specific capacity, good chemical stability, and abundant sources. However, its inherent poor conductivity, low utilization rate, and poor cycle stability greatly hinder its practical application. Oxygen vacancies in metal oxides can effectively regulate their electronic properties, reduce the band gap, and increase their electrical conductivity, thus significantly improving their electrochemical rate performance. Furthermore, oxygen vacancies can induce a low oxidation state of the metal, provide more active sites for surface redox reactions, and improve its electrochemical storage capacity. The review introduced various preparation methods and characterization techniques of oxygen-vacancy abundant transition metal oxides. This review also represented the latest advances of various metal oxides with oxygen vacancies from single metal oxides, bimetal oxides, and heteroatom doped metal oxides to achieve the superior performance for supercapacitors. In addition, some challenges and opportunities for the further development of metal oxides in electrochemical energy storage were also pointed out.