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

MoSe2 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 MoSe2 in PIBs is still hampered by its low conductivity and large volumetric expansion upon cycling. In this work, ultra-small few-layered MoSe2 nanosheets are encapsulated in N-doped porous carbon nanofibers (N-PCNFs) by an electrospinning and in situ carbonization/selenization process to form MoSe2/N-PCNFs nanocomposites. The morphology of nanocrystalline MoSe2 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 MoSe2 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 MoSe2/N-PCNFs are significantly improved. Moreover, the one-dimensional structure of N-PCNFs accelerates ions/electrons-transfer kinetics. The optimized MoSe2/N-PCNF with a moderate MoSe2 content exhibits excellent electrochemical performance for PIBs. The electro-chemical storage mechanism of MoSe2/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 MoSe2 based anodes for high-performance PIBs and other advanced secondary batteries.