Preparation of α-MnO2 Nanorods/Porous Carbon Cathode for Aqueous Zinc-ion Batteries

Aqueous zinc-ion batteries (ZIBs) have attracted more attention as large-scale energy storage technology due to their high safety, low cost and environmental benignity. To date, numerous cathodes based on manganese dioxide, vanadium dioxide, and polyanionic compounds have been reported. Among them, Manganese oxides have the advantages of low cost, non-toxicity, abundant materials and high working voltage, have been widely explored as promising cathodes for zinc ion batteries. Among them, MnO2 cathodes are particularly desirable candidates for commercialization owing to their tunnel structure and affordability. alpha-MnO2 has (1 x 1) and (2 x 2) tunnel structures, and Zn2+ can rapidly inserted and deserted in the tunnel. However, the capacity of manganese dioxide is fast decaying with the cycles due to the poor conductivity of MnO2, which limits its electrochemical performance. Herein, alpha-MnO2 nanorods are uniformly distributed on the surface of porous carbon nanosheets network (PCSs) by a simple hydrothermal/dispersion method strategy. In the alpha-MnO2/PCSs architecture, the alpha-MnO2 nanorods and alpha-MnO2/PCSs composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), etc. The results testified that alpha-MnO2/PCSs nanorods were firmly adhered on the surface of porous carbon nanosheets, which can effectively avoid the stacking of alpha-MnO2 nanorods, while the high conductive carbon network can improve the electrical conductivity of the composite. The porous network can provide effective electron transfer channels, provide stable hosts for fast Zn2+ extraction/insertion, and prevent the alpha-MnO(2 )nanorods from stacking each other. Benefiting from the unique porous structure and high conductive network, the alpha-MnO2/PCSs hybrid shows high reversibility capacity, good rate performance, and outstanding cycling stability. Specifically, alpha-MnO2/PCSs exhibits high reversible capacity of 350 mAh.g(-1) after 100 cycles at 0.1 A.g(-1) and maintains a capacity of 160 mAh.g(-1) at a high rate of 1 A.g(-1) after 1000 cycles, thus making it promising cathode for the high performance ZIBs.

Automated summary

Due to the poor conductivity of MnO2, the capacity of manganese dioxide decays quickly with cycles. In this study, alpha-MnO2 nanorods are uniformly distributed on the surface of porous carbon nanosheets network (PCSs) to improve the electrical conductivity of the composite. The resulting alpha-MnO2/PCSs hybrid exhibits high reversible capacity, good rate performance, and outstanding cycling stability, making it a promising cathode for high-performance ZIBs.