Construction of N-doped carbon encapsulated Mn₂O₃/MnO heterojunction for enhanced lithium storage performance

Owing to high theoretical capacity, low cost and abundant availability, manganese oxides are widely viewed as promising anodes for lithium-ion batteries (LIBs). Nonetheless, their practical application is significantly hindered by poor electrical conductivity, sluggish reaction kinetics and substantial volume change. In this work, an ingenious polypyrrole encapsulation followed by pyrolysis strategy is proposed to produce N-doped carbon encapsulated Mn₂O₃/MnO heterojunction (Mn₂O₃/MnO@NC) by using mechanically ground Mn₃O₄/C₃N₄ mixture as the precursor. The results show that the selection of precursor plays a pivotal role in the successful preparation of Mn₂O₃/MnO@NC hybrid. It is revealed that the uniform encapsulation by N-doped carbon significantly enhances the conductivity and structural stability of the final product. Concurrently, the Mn₂O₃/MnO heterojunction within the resultant hybrid exhibits a unique quantum-dot size, which effectively shortens ion transport pathways and exposes the active sites for lithium storage. Additionally, experimental observations and theoretical calculations demonstrate that the built-in electric fields generated at the interfaces of Mn₂O₃/MnO heterojunction accelerate the charge transfer and ion diffusion, thereby enhancing the electrochemical reaction kinetics. As a result, the Mn₂O₃/MnO@NC hybrid displays much enhanced lithium storage performance. Evidently, our work offers a good guidance for the design and synthesis of advanced transition metal oxide/carbon anodes for LIBs.