MoS₂ Nanosheets Hosted in Polydopamine-Derived Mesoporous Carbon Nanofibers as Lithium-Ion Battery Anodes: Enhanced MoS₂ Capacity Utilization and Underlying Mechanism

In this work, solid, hollow, and porous carbon nanofibers (SNFs, HNFs, and PNFs) were used as hosts to grow MoS₂ nanosheets hydrothermally. The results show that the nanosheets on the surface of SNFs and HNFs are comprised of a few grains stacked together, giving direct carbon-MoS₂ contact for the first grain and indirect contact for the rest. In contrast, the nanosheets inside of PNFs are of single-grain size and are distributed evenly in the mesopores of PNFs, providing efficient MoS₂-carbon contact. Furthermore, the nanosheets grown on the polydopamine-derived carbon surface of HNFs and PNFs have larger interlayer spacing than those grown on polyacrylonitrile-derived carbon surface. As a result, the MoS₂ nanosheets in PNFs possess the lowest charge-transfer resistance, the most accessible active sites for lithiation/delithiation, and can effectively buffer the volume variation of MoS₂, leading to its best electrochemical performance as a lithium-ion battery anode among the three. The normalized reversible capacity of the MoS₂ nanosheets in PNFs is about 1210 mAh g^-1 at 100 mA g^-1, showing the effective utilization of the electrochemical activity of MoS₂.