Insert Zn²⁺ in Tetrahedral Sites of Bi-metal Zn-Co Spinel Oxides with High Oxygen Catalytic Performance for Liquid and Flexible Zinc-Air Batteries

Nowadays, it is very challenging to develop a low-cost, highly active and stable bi-functional catalyst for accelerating oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction during the charge and discharge process of zinc-air battery. Herein, we successfully design a novel bi-metal oxide hybrid catalyst (ZnCo₂O₄-CNT) by inserting Zn ions. Benefiting from the robust synergetic effects between porous ZnCo₂O₄ and CNTs, the high conductivity and the unique nanostructure, the ZnCo₂O₄-CNT shows lots of accessible active sites and improved reactants and electrons transfer. As expected, the hybrid shows higher ORR and OER performances with larger limited diffusion current density (5.72 mA cm^-2) and lower OER over-potential (0.49 V) than Pt/C and other ZnCo₂O₄-CNT samples. In addition, rechargeable zinc-air battery assembled with the bi-functional catalyst exhibits a high power density of 249.4 mW cm^-2, a strong discharge durability and charge-discharge stability of 240 cycles. Notably, the flexible zinc-air battery also shows good battery performances with high power density and good flexibility. Hence, exploiting efficient bi-functional catalytic materials with excellent ORR and OER performance and assembling flexible devices will improve the development of current zinc-air batteries battery industry.