Manipulating intercalation-extraction mechanisms in structurally modulated 6-MnO2 nanowires for high-performance aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted wide attention recently because of their low cost, high safety, and environmental friendliness. However, manganese-based materials always suffer from irreversible structural transformation and sluggish reaction kinetics, resulting in low capacity and poor cycling stability, which hinders their practical application in large-scale energy storage. Herein, we demonstrate a structural modulation strategy to manipulate the electrochemical reaction mechanism in layered 6-MnO2 via Cu2+ intercalation. A favorable H+/Zn2+ intercalation-extraction mechanism is identified in structurally modulated 6-MnO2 electrode after the reversible Zn2+ intercalation and H+ conversion reaction in the initial several cycles, which is thoroughly investigated and demonstrated through multiple analytical means. The resulted 6-MnO2 cathodes deliver rapid and reversible Zn2+ storage, with a high reversible capacity of 398.2 mAh g? 1 at 0.1 A g? 1 and 90.1% capacity retention after 700 cycles at 5 A g? 1. Further ex-situ characterization demonstrates the rapid and reversible H+/Zn2+ storage in the structurally modulated 6-MnO2 cathodes. Density functional theory calculations reveal Cu2+ intercalation in 6-MnO2 effectively enhances the structural stability of 6-MnO2 via the strong ionic bonds bonded with oxygen atoms, and also optimizes electronic bandgap and ion/charge state of 6-MnO2, thus attributing favorable ion intercalation-extraction mechanisms. This structural modulation strategy provides a new gateway to the development of robust-structured cathode materials by manipulating the electrochemical reaction mechanisms in electrode materials for ZIBs. Superscript/Subscript Available

Automated summary

This study demonstrates a structural modulation strategy by Cu2+ intercalation to manipulate the electrochemical reaction mechanism in layered 6-MnO2, resulting in rapid and reversible zinc ion storage. The findings address the challenges of low capacity and poor cycling stability in manganese-based materials and provide a new approach for the development of cathode materials for zinc-ion batteries.