Embedding MnO@Mn3O4 Nanoparticles in an N-Doped-Carbon Framework Derived from Mn-Organic Clusters for Efficient Lithium Storage

Abstract

The first synthesis of MnO@Mn₃O₄ nanoparticles embedded in an N-doped porous carbon framework (MnO@Mn₃O₄/NPCF) through pyrolysis of mixed-valent Mn₈ clusters is reported. The unique features of MnO@Mn₃O₄/NPCF are derived from the distinct interfacial structure of the Mn₈ clusters, implying a new methodological strategy for hybrids. The characteristics of MnO@Mn₃O₄ are determined by conducting high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy loss spectroscopy (EELS) valence-state analyses. Due to the combined advantages of MnO@Mn₃O₄, the uniform distribution, and the NPCF, MnO@Mn₃O₄/NPCF displays unprecedented lithium-storage performance (1500 mA h g⁻¹ at 0.2 A g⁻¹ over 270 cycles). Quantitative analysis reveals that capacitance and diffusion mechanisms account for Li⁺ storage, wherein the former dominates. First-principles calculations highlight the strong affiliation of MnO@Mn₃O₄ and the NPCF, which favor structural stability. Meanwhile, defects of the NPCF decrease the diffusion energy barrier, thus enhancing the Li⁺ pseudocapacitive process, reversible capacity, and long cycling performance. This work presents a new methodology to construct composites for energy storage and conversion.

The first synthesis of MnO@Mn₃O₄ nanoparticles embedded in an N-doped porous carbon framework (MnO@Mn₃O₄/NPCF) through pyrolysis of mixed-valent Mn₈ clusters indicates unprecedented lithium-storage performance. The as-synthesized MnO@Mn₃O₄ composition is first identified by a combination of atomic-resolution HAADF-STEM and EELS valence-state analyses. This work presents a new methodology to construct composites for energy storage and conversion.

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