Cationic and anionic defect decoration of CoO through Cu dopants and oxygen vacancy for a High‑Performance...

CoO has attracted increasing attention as an electrochemical energy storage owing to its excellent redox activity and high theoretical specific capacitance. However, its low inherent electrical conductivity results in sluggish reaction kinetics, and the poor rate capability of CoO limits its widespread applications. Herein, a multiple-defect strategy of engineering oxygen vacancies and Cu-ion dopants into the low-crystalline CoO nanowires (Ov-Cu-CoO) is successfully applied. Because of the advantage of the dual defect synergetic effect, the electronic structure and charge distribution are effectively modulated, thus enhancing the electrical conductivity and enriched redox chemistry. The obtained Ov-Cu-CoO electrode exhibits a high specific capacity of 1388.6 F⋅g^-1 at a current density of 1 A⋅g^-1, an ultrahigh rate performance (81.2% of the capacitance retained at 20 A⋅g^-1) and excellent cycling stability (101.1% after 10,000 cycles). Moreover, an asymmetric supercapacitor device with Ov-Cu-CoO as the positive electrode having a high energy density of 44.1 W⋅h⋅kg^-1 at a power density of 800 W⋅kg^-1, and can still remain 27.2 W⋅h⋅kg^-1 at a power density of 16 kW⋅kg^-1. This study demonstrates an effective strategy to enhance electrochemical performance of CoO that can be easy applied to other transition metal oxides.