Yucca-like CoO–CoN Nanoarray with Abundant Oxygen Vacancies as a High-Performance Cathode for Lithium–Oxygen Batteries

In this paper, we report a three-dimensional, yucca-like CoO–CoN composite cathode prepared by the in situ growth of a Co(OH)F array on pretreated carbon paper, followed by controllable partial nitridation in ammonia flow. The material exhibited excellent oxygen reduction and evolution activity and, in particular, excellent cathode performance for aprotic Li–O2 batteries. Our optimal sample yielded a specific capacity of up to 5423 mA h g–1 and functioned for 200 cycles with no degradation. It was found that the introduction of oxygen vacancies on the surface of CoO–CoN through nitridation played a crucial role in the material’s high performance, especially its high stability and long cyclability. We attribute the high performance to the following: first, the material’s nanoarray architecture, which provided a large surface area and featured enough interspaces to ensure a high density of active sites as well as to assist with oxygen and ion diffusion, and with the hosting of discharge products, and second, the abundant oxygen vacancies generated on the CoO–CoN surface during partially controlled nitridation, which significantly enhanced the material’s oxygen reduction/evolution reaction activity and stability.