Facile synthesis of flower-like hierarchical NiCo2O4 microspheres as high-performance cathode materials for Li–O2 batteries

Abstract

Development of efficient and cost-effective catalyst is one of the key issues for practical lithium–oxygen (Li–O₂) batteries. Herein, we report a facile synthesis of flower-like hierarchical NiCo₂O₄ microspheres as an effective cathode catalyst for Li–O₂ batteries. The synthesized NiCo₂O₄ microsphere consists of loosely interconnected nanopetals, which could simultaneously offer sufficient active sites, facilitate mass transfer of Li⁺/O₂ and provide enough space for Li₂O₂ deposition. When employed as the cathode catalyst for Li–O₂ batteries, a low discharge/charge voltage gap of 0.86 V can be obtained, much lower than previously reported results for NiCo₂O₄. Meanwhile, flower-like NiCo₂O₄ shows improved discharge capacity (3163 mA h g⁻¹ at 0.08 mA cm⁻²) and better cycle stability (60 cycles at 500 mA h g⁻¹ capacity limit) compared with NiCo₂O₄ nanoneedles and bare carbon cathode. The superior electrochemical performance of NiCo₂O₄, together with the facile fabrication approach, makes NiCo₂O₄ microspheres a promising candidate for Li–O₂ batteries.