Oxygen Defects in Promoting the Electrochemical Performance of Metal Oxides for Supercapacitors: Recent Advances and Challenges

Abstract Metal oxides (MOs) with multiple active sites are regarded as one of the most potential active materials for high‐performance supercapacitor (SC) constructions. Engineering oxygen vacancies into MOs can effectively modulate their electronic properties, subtly induce impurity states in their bandgaps, and considerably optimize their electrical conductivity. Benefiting from these advantageous properties, the resultant oxygen‐defective electrodes generally embed more electrochemical active sites and present better charge storage capability in contrast to the pristine sample. Particular research attention has been given to the realization of precise oxygen vacancy introduction into MOs and the fine tuning of their properties. This review presents an overview of recent accomplishments in developing new oxygen‐defective MOs for advanced SC assembly. Different strategies for oxygen vacancy productions are summarized and compared. The specific roles of oxygen vacancies in the electrochemical performance enhancement are fully addressed and the relevant impact factors are discussed in detail. Finally, the key challenges and future opportunities in this rapidly developing field are highlighted.