Brush-Like Cobalt Nitride Anchored Carbon Nanofiber Membrane: Current Collector-Catalyst Integrated Cathode for Long Cycle Li–O2 Batteries

Abstract

To achieve a high reversibility and long cycle life for lithium–oxygen (Li–O 2 ) batteries, the irreversible formation of Li 2 O 2, inevitable side reactions, and poor charge transport at the cathode interfaces should be overcome. Here, we report a rational design of air cathode using a cobalt nitride (Co 4 N) functionalized carbon nanofiber (CNF) membrane as current collector-catalyst integrated air cathode. Brush-like Co 4 N nanorods are uniformly anchored on conductive electrospun CNF papers via hydrothermal growth of Co(OH)F nanorods followed by nitridation step. Co 4 N-decorated CNF (Co 4 N/CNF) cathode exhibited excellent electrochemical performance with outstanding stability for over 177 cycles in Li–O 2 cells. During cycling, metallic Co 4 N nanorods provide sufficient accessible reaction sites as well as facile electron transport pathway throughout the continuously networked CNF. Furthermore, thin oxide layer (<10 nm) formed on the surface of Co 4 N nanorods promote reversible formation/decomposition of film-type Li 2 O 2, leading to significant reduction in overpotential gap (∼1.23 V at 700 mAh g –1 ). Moreover, pouch-type Li-air cells using Co 4 N/CNF cathode stably operated in real air atmosphere even under 180° bending. The results demonstrate that the favorable formation/decomposition of reaction products and mediation of side reactions are hugely governed by the suitable surface chemistry and tailored structure of cathode materials, which are essential for real Li–air battery applications.