Multi-scale Structural Engineering Of Ni-doped CoO Nanosheets For Zinc-air Batteries With High-Power Density

Zinc-air batteries have great application for large-scale energy-storage due to their low cost,high energy density and significant stability,but their widespread application is limited by low power density,which is mainly affected by the oxygen reduction reaction?ORR?efficiency on the air electrode.In the past decade,great progress has been made in the development of highly active ORR electrocatalysts,These highly active electrocatalysts by changing the structure and increasing the intrinsic catalytic activity significantly have increased the peak power density of zinc-air batteries to>200 mW cm^-2.However,to compete with present lithium-ion technology further improvement in zinc-air batteries is needed.This requires multi-scale control of structure of electrocatalysts to assist the ORR at the gas?O₂?/liquid?electrolyte?/solid?catalysts?three-phase interface.?i?ZnO NSs were first grown on a fluorine-doped tin oxide?FTO?substrate using a simple hydrothermal method,and CoO NSs were synthesized by the cation exchange method in a quartz-tube by adjusting different temperatures and different Co/Ni ratios.Experimental and theoretical calculations show that we have achieved multi-scale structural engineering of Ni-doped CoO NS for zinc-air battery:In micro-and nanoscale,robust 2D architecture together with numerous nanopores inside the nanosheets provides an advantageous micro/nanostructured surface for O₂ diffusion and a high electrocatalytic active surface area.In atomic scale,Ni doping signifcantly enhances the intrinsic oxygen reduction reaction activity per active site.?ii?As a result of controlled multi-scale structure,the primary zinc-air battery with engineered Ni-doped CoO NSs electrode showed excellent performance with a record-high discharge peak power density of 377 mW cm^-2.Rechargeable zinc-air battery based on Ni-doped CoO NSs afforded an unprecedented small charge-discharge voltage of 0.63 V(charge density:2 mA cm^-2,discharge density:20mA cm^-2),outperforming state-of-the-art Pt/C catalyst-based device.Moreover,a significant durability of Ni-doped CoO NSs leads to primary and rechargeable batteries that are stable for>400 h at 5 mA cm^-2 and with 100 h charge and discharge cycles,respectively.Moreover,we show Ni-doped CoO NSs assembled into all-solid-state coin cells can power 17 light-emitting diodes and charge an iPhone 7mobile phone.