A unique hierarchical structure: NiCo2O4 nanowire decorated NiO nanosheets as a carbon-free cathode for Li–O2 battery

Abstract

The development of high-performance cathodes is critical to promoting the development of Li–O₂ batteries. In this work, three-dimensional NiCo₂O₄ nanowire-decorated NiO nanosheets (NiO@NiCo₂O₄) on a Ni foam were fabricated by a two-step solvothermal process. The product exhibited efficient catalytic performance for Li–O₂ batteries. This three-dimensional NiO@NiCo₂O₄ hierarchical structures grown on Ni foam forms a porous catalytic surface for the uniform growth of discharge products. First, NiCo₂O₄ is a promising catalyst for improving the oxygen reduction reaction/oxygen evolution reaction (ORR/OER) processes for the Li–O₂ batteries. Second, NiO can provide a porous scaffold for the further deposition of NiCo₂O₄ nanowires to avoid their aggregation. Furthermore, NiO can promote the decomposition of by-products containing carbonate/carboxylate species. As a result, the Li–O₂ system with NiO@NiCo₂O₄ as a carbon-free cathode showed a maximum in-depth-specific discharge capacity of 9361.4 mA h g⁻¹ at a current density of 100 mA g⁻¹ and 176 cycles of stability under a limited capacity of 500 mA h g⁻¹ at a current density of 200 mA g⁻¹. The reported strategy regarding a multicomponent hierarchical structure may provide a new approach for effective electrocatalyst design for Li–O₂ batteries.