Oxygen Vacancy-Rich RuO2-Co3O4 Nanohybrids as Improved Electrocatalysts for Li-O2 Batteries.

Abstract

Lithium oxygen (Li-O2) batteries have shown great potential as new energy-storage devices due to the high theoretical energy density. However, there are still substantial problems to be solved before practical application, including large overpotential, low energy efficiency, and poor cycle life. Herein, we have successfully synthesized a RuO2-Co3O4 nanohybrid with a rich oxygen vacancy and large specific surface area. The Li-O2 batteries based on the RuO2-Co3O4 nanohybrid shown obviously reduced overpotential and improved circulatory property, which can cycle stably for more than 100 cycles at a current density of 200 mA g-1. Experimental results and density function theory calculation prove that the introduction of RuO2 can increase oxygen vacancy concentration of Co3O4 and accelerate the charge transfer. Meanwhile, the hollow and porous structure leads to a large specific surface area about 104.5 m2 g-1, exposing more active sites. Due to the synergistic effect, the catalyst of the RuO2-Co3O4 nanohybrid can significantly reduce the adsorption energy of the LiO2 intermediate, thereby reducing the overpotential effectively.