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%).