Unraveling the Role of Nitrogen‐Doped Carbon Nanowires Incorporated with MnO₂ Nanosheets as High Performance Cathode for Zinc‐Ion Batteries

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Abstract

Manganese‐based cathode materials are considered as a promising candidate for rechargeable aqueous zinc‐ion batteries (ZIBs). Suffering from poor conductive and limited structure tolerance, various carbon matrix, especially N‐doped carbon, were employed to incorporate with MnO 2 for greatly promoted electrochemical performances. However, the related underlying mechanism is still unknown, which is unfavorable to guide the design of high performance electrode. Herein, by incorporating layered MnO 2 with N‐doped carbon nanowires, a free‐standing cathode with hierarchical core‐shell structure (denoted as MnO 2 @NC) is prepared. Benefiting from the N‐doped carbon and rational architecture, the MnO 2 @NC electrode shows an enhanced specific capacity (325 mAh g −1 at 0.1 A g −1 ) and rate performance (90 mAh g −1 at 2 A g −1 ), as well as improved cycling stability. Furthermore, the performance improvement mechanism of MnO 2 incorporated by N‐doped carbon is investigated by X‐ray photoelectron spectroscopy (XPS), Raman spectrums and density functional theory (DFT) calculation. The N atom elongates the Mn‐O bond and reduces the valence of Mn 4+ ion in MnO 2 crystal by delocalizing its electron clouds. Thus, the electrostatic repulsion will be weakened when Zn 2+ /H + insert into the host MnO 2 lattices, which is profitable to more cation insertion and faster ion transfer kinetics for higher capacity and rate capability. This work elucidates a fundamental understanding of the functions of N‐doped carbon in composite materials and shed light on a practical pathway to optimize other electrode materials.

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