Hollow Structural Transition Metal Oxide for AdvancedSupercapacitors

Electrochemical capacitors (supercapacitors, SCs), have been deemed to be one of the most promising powerful electrochemical energy storage devices, owing to that SCs have long cycle lives, high power densities, and fast recharge capabilities. Transition metal oxide is one of the most promising electrode materials in the application of SCs, but the poor active surface areas limit their electrochemical performances. Particularly, hollow structures can enhance their active surface areas and porosity for better transportation. In this review, the development regarding hollow structures of the metal oxide, metal oxide complex, and carbon-metal oxide complex is discussed. Furthermore, performances of these materials applied in SCs are tested in various systems, and their electrochemical performances are introduced and compared. The disadvantages of SCs based on hollow metal oxide materials are also discussed, and the various solutions are provided.