Iridium Cluster Decoration on Amorphous Cobalt Oxide-Coated Carbon Nanotubes for High-Performance Lithium-Oxygen Battery Cathodes.

Lithium-oxygen batteries hold great promise for next-generation energy storage due to their exceptionally high theoretical energy density. However, their practical application is hindered by the sluggish kinetics associated with the oxygen reduction reaction and oxygen evolution reaction, resulting in severe voltage polarization and limited cycling stability. Herein, a simple solvent thermal reaction and a one-step reduction reaction is developed, where amorphous cobalt oxide (CoO) is uniformly coated on multi-walled carbon nanotubes (CNT) and further decorated with highly dispersed iridium (Ir) clusters. The amorphous CoO coatings preferentially nucleate at CNT defect sites, which not only passivates surface defects but also facilitates the homogeneous distribution of Ir clusters. This unique Ir/CoO@CNT architecture provides abundant active sites and promotes efficient electronic and ionic transport, thereby enhancing the electrocatalytic activity and overall battery performance. The synergistic effect between the highly active Ir clusters and the amorphous CoO, which accelerates reaction kinetics and stabilizes the electrode interface. As a result, the Ir/CoO@CNT cathode achieves a high discharge capacity of ≈6700 mAh g, with a low overpotential of 0.96 V and exhibits excellent cycling stability, sustaining over 150 cycles under a limited capacity of 500 mAh g at 500 mA g.