Self-standing heterostructured NiC -NiFe-NC/biochar as a highly efficient cathode for lithium-oxygen batteries.

Lithium-oxygen batteries have attracted research attention due to their low cost and high theoretical capacity. Developing inexpensive and highly efficient cathode materials without using noble metal-based catalysts is highly desirable for practical applications in lithium-oxygen batteries. Herein, a heterostructure of NiFe and NiC inside of N-doped carbon (NiC -NiFe-NC) derived from bimetallic Prussian blue supported on biochar was developed as a novel self-standing cathode for lithium-oxygen batteries. The specific discharge capacity of the best sample was 27.14 mAh·cm at a stable discharge voltage of 2.75 V. The hybridization between the d-orbital of Ni and s and p-orbitals of carbon in NiC , formed at 900 °C, enhanced the electrocatalytic performance due to the synergistic effect between these components. The structure of NiC -NiFe-NC efficiently improved the electron and ion transfer between the cathode and the electrolyte during the electrochemical processes, resulting in superior electrocatalytic properties in lithium-oxygen batteries. This study indicates that nickel carbide supported on N-doped carbon is a promising cathode material for lithium-oxygen batteries.