Metal-Organic Framework-Derived Porous NiCo-Layered Double Hydroxide@MnO2 Hierarchical Nanostructures as Catalytic Cathodes for Long-Life Li-O2 Batteries

The commercial application of lithium-oxygen (Li-O-2) batteries has been seriously hindered by their large overpotential and inferior cycling performance caused by the insoluble and insulated traits of the discharge product, Li2O2. Herein, hierarchical hollow NiCo-LDH/MnO2 hybrid nanostructures derived from metal-organic frameworks (MOFs) are successfully constructed as cathodes for Li-O-2 batteries to fundamentally improve the decomposition kinetics of Li2O2. The hollow NiCo-LDH/MnO2 nanostructures assembled by hollow NiCo-LDH and MnO2 nanosheets possess a highly special surface area, abundant open active sites, and a fast diffusion path for Li+ and oxygen species. As expected, accelerated sluggish oxygen reduction reaction/oxygen evolution reaction kinetics and reduced charge/discharge overpotentials can be obtained. The toroidal Li2O2 assembled by nanoflakes formed on the surface of the cathode can be conducive to form a low-impedance Li2O2/cathode contact interface to achieve the reversible formation and decomposition of Li2O2. The Li-O-2 battery based on the NiCo-LDH/MnO2 cathode shows a high charge/discharge specific capacity of 13,380 mA h at 100 mA and a continuous cycling stability for 162 cycles at a fixed capacity of 500 mAh g(-1) as well as a low overpotential of 0.63 V. Moreover, the application of MOF-derived porous hierarchical nanostructures expands the selection range of electrocatalysts and offers a new idea of structure design for Li-O-2 batteries.