3D Hollow α-MnO2 Framework as an Efficient Electrocatalyst for Lithium-Oxygen Batteries

Lithium-oxygen (Li-O-2) batteries are attracting more attention owing to their superior theoretical energy density compared to conventional Li-ion battery systems. With regards to the catalytically electrochemical reaction on a cathode, the electrocatalyst plays a key role in determining the performance of Li-O-2 batteries. Herein, a new 3D hollow alpha-MnO2 framework (3D alpha-MnO2) with porous wall assembled by hierarchical alpha-MnO2 nanowires is prepared by a template-induced hydrothermal reaction and subsequent annealing treatment. Such a distinctive structure provides some essential properties for Li-O-2 batteries including the intrinsic high catalytic activity of alpha-MnO2, more catalytic active sites of hierarchical alpha-MnO2 nanowires on 3D framework, continuous hollow network and rich porosity for the storage of discharge product aggregations, and oxygen diffusion. As a consequence, 3D alpha-MnO2 achieves a high specific capacity of 8583 mA h g(-1) at a current density of 100 mA g(-1), a superior rate capacity of 6311 mA h g(-1) at 300 mA g(-1), and a very good cycling stability of 170 cycles at a current density of 200 mA g(-1) with a fixed capacity of 1000 mA h g(-1). Importantly, the presented design strategy of 3D hollow framework in this work could be extended to other catalytic cathode design for Li-O-2 batteries.