Core/shell design of efficient electrocatalysts based on NiCo2O4 nanowires and NiMn LDH nanosheets for rechargeable zinc–air batteries

Rechargeable zinc–air (Zn–air) batteries having high theoretical energy density are the most attractive energy technologies for future electric vehicles and flexible/wearable electronics. However, the serious lack of highly efficient and cost-effective oxygen electrocatalysts is one of the major obstacles for their future commercialization. Herein, we presented a core/shell design based on porous NiCo2O4 nanowires and ultrathin NiMn LDH nanosheets as an efficient method for the synthesis of electrocatalysts for rechargeable Zn–air batteries. Due to the large active surface area, rapid mass/charge transport, and high electron conductivity as well as unique structures, the core/shell NiCo2O4@NiMn LDH materials could deliver a rather low OER overpotential of 255 mV at 10.0 mA cm−2 while maintaining good stability in alkaline media. When these materials were further employed as air-cathode materials for Zn–air batteries, they exhibited an ultrahigh energy density (866 W h kg−1), superior reversibility (initial round-trip efficiency of 63.5%) and excellent stability (voltage gap increased by only about 20 mV after 500 cycles), which were much better than those of commercial Ir/C catalyst. Furthermore, the as-prepared flexible solid Zn–air battery also displayed very good mechanical properties, long cycle life and outstanding round-trip efficiency (70–74%).