Ultra-small few-layered MoSe2 nanosheets encapsulated in nitrogen-doped porous carbon nanofibers to create large heterointerfaces for enhanced potassium-ion storage

MoSe 2 has recently attracted great interest in the development of high-performance potassium-ion batteries (PIBs) anode materials because of its high theoretical capacity. However, the practical application of MoSe 2 in PIBs is still hampered by its low conductivity and large volumetric expansion upon cycling. In this work, ultra-small few-layered MoSe 2 nanosheets are encapsulated in N-doped porous carbon nanofibers (N-PCNFs) by an electrospinning and in situ carbonization/selenization process to form MoSe 2 /N-PCNFs nanocomposites. The morphology of nanocrystalline MoSe 2 is fine-tuned to maximize the heterointerfaces of dichalcogenide/carbon matrix that function as active sites for potassium-ion storage. Benefitting from the effective confinement of MoSe 2 in the carbon matrix and the robust chemical bonds (C Se and C Mo) formed at the heterointerfaces, the structure stability and charge transfer kinetics of MoSe 2 /N-PCNFs are significantly improved. Moreover, the one-dimensional structure of N-PCNFs accelerates ions/electrons-transfer kinetics. The optimized MoSe 2 /N-PCNF with a moderate MoSe 2 content exhibits excellent electrochemical performance for PIBs. The electrochemical storage mechanism of MoSe 2 /N-PCNFs is investigated by in situ X-ray diffraction measurements. Density functional theory calculations verify the enhanced adsorption of potassium-ion and electron transport at the heterointerfaces. This work provides new insights into the design of MoSe 2 based anodes for high-performance PIBs and other advanced secondary batteries.