Facilely synthesized honeycomb-like NiCo₂O₄ nanoflakes with an increased content of oxygen vacancies as an efficient cathode catalyst for Li-O₂ batteries

The development of high energy density Li-O₂ batteries is restricted by the sluggish kinetics of both the oxygen reduction reaction and the oxygen evolution reaction, and developing an efficient cathode catalyst is the key to resolving this issue. In present study, interconnected honeycomb-like NiCo₂O₄ nanoflakes are synthesized by facile electrochemical deposition on carbon cloth (CC) and subsequent heat treatment. Compared with NiO and Co₃O₄, suitably sized NiCo₂O₄ nanoflakes benefit from a vital synergistic effect of components Co and Ni and are expected to show superior OER/ORR performance. The presence of redox couples Co³⁺/Co²⁺ and Ni²⁺/Ni³⁺ and abundant oxygen vacancies in NiCo₂O₄ allow Li-O₂ batteries deliver satisfactory cycle durability and high discharge/recharge capacities. Li-O₂ batteries that use the NiCo₂O₄/CC cathodes exhibit high specific discharge capacities of 8388 mA h g⁻¹ and 5238 mA h g⁻¹ at 200 mA g⁻¹ and 400 mA g⁻¹, respectively, and deliver a long lifetime of 102 cycles with a capacity limit of 500 mA h g⁻¹ at 340 mA g⁻¹, thereby suggesting that honeycomb-like NiCo₂O₄ nanoflakes are a promising cathode catalyst.