Facile electrochemically induced vacancy modulation of NiCo2O4 cathode toward high-performance aqueous Zn-based battery

Abstract

Transition metal oxides are highly promising cathode materials in rechargeable Zn-based batteries owing to their low cost, high theoretical capacity and good reversibility. Nevertheless, intrinsically low conductivity and sluggish redox reaction kinetics normally result in their inferior specific capacity and poor rate capability, which critically constrains the practical performance of Zn-based batteries. Herein, an ultrafast and controllable electrochemical activation (EA) process is developed to effectively enhance the electrochemical performance of NiCo2O4 cathode. Systematic studies reveal EA process triggers in situ reconstruction of NiCo2O4 lattice by weakening the coordination of Co-O bonds, resulting in the formation of abundant oxygen vacancies (octahedral Co2+). These oxygen vacancies increase the charge carrier density and endow the superficial metallic active sites with higher electrochemical activity, which synergistically accelerates the electrochemical reaction kinetics. The oxygen-deficient NiCo2O4 exhibits a remarkable capacity of 418.9 mAh/g at 1 A/g, which is nearly 5-fold higher than that of pristine NiCo2O4. Furthermore, the oxygen-deficient NiCo2O4//Zn battery presents an extremely high energy density (682.4 Wh kg−1) and excellent power density (50.8 kW kg−1), surpassing most of the reported aqueous rechargeable batteries. This work provides a facile and effective vacancy modulation strategy for the development of advanced materials utilized in energy and catalysis fields.