Metal–Organic Framework-Derived Porous NiCo-Layered Double Hydroxide@MnO<sub>2</sub> Hierarchical Nanostructures as Catalytic Cathodes for Long-Life Li–O<sub>2</sub> Batteries
Mingjie Ding, Peng Wang, Zhiwei Zhang, Longwei Yin
Abstract
The commercial application of lithium–oxygen (Li–O2) 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–O2 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–O2 battery based on the NiCo-LDH/MnO2 cathode shows a high charge/discharge specific capacity of 13,380 mA h g–1 at 100 mA g–1 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–O2 batteries.