Iridium coated Co nanoparticles embedded into highly porous N-doped carbon nanocubes grafted with carbon nanotubes as a catalytic cathode for high-performance Li–O2 batteries

Abstract

Rechargeable Li–O₂ batteries have attracted worldwide attention due to their super-high energy density. However, there are still many critical challenges for Li–O₂ batteries, such as huge overpotential caused by sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics, and inferior cycle life derived from severe side reactions. Designing highly efficient cathode catalysts should be a good choice for Li–O₂ batteries to solve the above problems. Herein, we developed Ir-coated Co nanoparticles confined into highly porous N-doped carbon nanocubes grafted with carbon nanotubes (Ir–Co/HP-NC/CNT) through carbonization of the Co/Zn–zeolitic imidazolate framework (ZIF) and the subsequent Ir-coating. Introduction of Zn into the ZIF precursor not only makes Ir–Co/HP-NC/CNT have high porosity that can promote ion/electron transfer, but also improves the surface content of pyridinic/graphitic N and Co_xN phases which accelerate ORR/OER kinetics. Moreover, theoretical calculation/experimental results further confirm that the synergy between the Ir-coating and Co/HP-NC/CNT can effectively alleviate undesired parasitic reactions and also enhance reversibility in Li–O₂ batteries by adjusting Li₂O₂ formation. As a result, Ir–Co/HP-NC/CNT based Li–O₂ batteries show a super-high discharge capacity of 13 200 mA h g⁻¹ at 100 mA g⁻¹ and a very long cycling life up to 320 cycles at 500 mA g⁻¹ with a fixed capacity of 1000 mA h g⁻¹. Importantly, we have also designed large-size bulk-shaped Li–air batteries with Ir–Co/HP-NC/CNT cathodes that exhibit good performance even under bending conditions and effectively power practical electronic devices.