Electron-redistributed Ni–Co oxide nanoarrays as an ORR/OER bifunctional catalyst for low overpotential and long lifespan Li–O2 batteries

Abstract

Lithium–oxygen batteries with extra-high energy density have attracted increasing attention. However, their development is limited by sluggish oxygen redox kinetics, resulting in large overpotential and low cyclic life. Herein, N-NiCoO₂/CoO arrays on conductive carbon cloth (noted as NNCO/CC) were designed by a hydrothermal and nitriding method as an ORR/OER bifunctional catalyst for LOB cathode to alleviate this problem. The introduction of N promotes electron redistribution on bimetal sites, which can enhance the affinity of intermediates (O*, LiO₂*, Li₂O₂*) and induce the deposition/decomposition of flake-like amorphous Li₂O₂. Based on the NNCO/CC cathode, Li–O₂ cells exhibit a low overpotential of 0.35 V and improved cycling capability of over 500 cycles at 0.05 mA cm⁻². The cycle stability could be maintained over 225 cycles with a limited capacity of 0.2 mA h cm⁻². DFT calculations further disclose that NNCO/CC shows a synergistic role in the ORR and OER processes. N-NiCoO₂ has a more vital adsorption ability toward key intermediates (LiO₂*) in the ORR process and N-CoO has a slight reaction energy barrier in the OER process. The method of regulating the electronic structure of bimetallic oxides to promote synergy in the redox reactions opens up new paths for the functional cathode design of Li–O₂ cells.