A Composite of Carbon‐Wrapped Mo₂C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O₂ Batteries

Abstract

Cathode design is indispensable for building Li‐O 2 batteries with long cycle life. A composite of carbon‐wrapped Mo 2 C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo 2 C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo 2 C nanoparticles. The even distribution of Mo 2 C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O 2 batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g −1 and a low average charge voltage of ≈4.0 V at 200 mA g −1 . With a cutoff capacity of 1000 mAh g −1 , the Li‐O 2 batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo 2 C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O 2 batteries.