Synthesis of Co4N nanoparticles via a urea-glass route toward bifunctional cathode for high-performance Li-O2 batteries

Rechargeable lithium-oxygen (Li-O2) batteries are considered as one of the most ideal energy storage devices because of their high theoretical energy density. However, the practical application of Li-O2 batteries is hindered by their slow reaction kinetics and various notorious side reactions, which causing inferior redox over -potentials. Herein, Co4N nanoparticles electrode with low agglomeration by using a urea-glass route at moderate temperatures is proposed to address the above challenges. It shows high electron conductivity since it retained metallic cobalt crystal structure. In addition, the efficiently catalytic activity of Co4N can effectively suppress side reactions by reducing the charging polarization and expand the reaction kinetics. The DFT results demonstrate that the electronic structure change of Co4N crystal plays an important role in improving ORR activity. The overpotential for ORR increases in Co4N/N-CNTs is much easier to implement within the applied potential, and thus leading to a better catalytic performance toward ORR. Meanwhile, coupling with nitrogen can effectively optimize the electronic structure of Co4N sites in N-CNTs, thereby reducing the energy barrier of reaction intermediates to promote the reversible ORR kinetics process. Benefiting from the above advantages, the Co4N/N-CNTs delivers improved long-term cycling stability (80 cycles under O2 atmosphere) under the capacity limited at 500 mAh g-1 and current density at 200 mA g-1. This work suggests an effective pathway to fabricate the metal nitrides with efficiently catalytic activity.