| MoS2 is one of the typical two-dimensional transition metal chalcogenides（TMDs）which possesses unique structural features,high electrochemical activity and good chemical stability.Furthermore,weak van der Waals interactions and relatively large interlayer distances between Mo S2 layers facilitate its exfoliation and dispersion in organic solvent,resulting in an increased effective surface area that can be used as 2D templates for the growth of other functional nanocomposites particle.Make it possible in energy storage equipment（supercapacitors,lithium-ion batteries）.However,the efficient preparation of high quality Mo S2 nanosheets remains a challenge.In addition,its own poor conductivity and structural stability,re-stacking effect and structural collapse during electrochemical reactions often lead to rapid decay in performance,which greatly limits its practical application.In this dissertation,aiming at these key problems,a versatile and scalable solvent-exchange method has been developed to obtain high-concentration Mo S2（f-Mo S2）dispersions in low-boiling solvents,such as ethanol and water.In this regard,Mo S2-based composites with controllable hierarchical structures,high conductivity and high specific surface area are prepared by utilizing Mo S2 as tamplates,and functionalized conductive polymer,transition metal oxide or nitrogen-enriched polypyrrole as building blocks through a convenient reaction process.Furthermore,the formation principle and regulation mechanism of its structure has been revealed,and the relationship between its microstructure and macroscopic properties has been also explored.The research is expected to propose a useful method for the design and developing of subtly structured Mo S2-based nanocomposites with high electrochemical performance.The main results obtained in this dissertation are as follows:（1）Based on the design of three-dimensional structure,"pizza-like" Mo S2/PPy/PANI ternary composites are prepared and their electrochemical properties used as supercapacitor electrode materials are also evaluated.Ultrathin two-dimensional Mo S2 nanosheets can be used as energy storage ion reservoir and shorten the diffusion path for electron transport.This special structure improves the dispersion of PANI,and enhances the contact interface between PANI and the electrolyte,and improves the electrochemical performance.The PPy intermediate layer can buffer the volumetric swelling and shrinking during the charge/dischargeprocess,so that the structure is stable.The Mo S2/PPy/PANI composite achieves a specific capacitance of 1273 F g-1 at a current density of 0.5 A g-1 and exhibits excellent cycle stability.（2）The f-Mo S2 was successfully integrated with transition metal oxides（nickel oxide,tricobalt tetroxide and ferric oxide）by chemical bath deposition at room temperature and the electrochemical performance of the composites was investigated as electrode materials of supercapacitors.The hybrid material has the characteristics of three-dimensional porous structure,large specific surface area,high electrical conductivity and excellent structural stability.Transition metal oxide and Mo S2 nanosheets form a synergistic effect.The formed molybdenum disulfide/transition metal oxide framework can not only restrain the re-stacking of the molybdenum sulfide nanosheets,but also buffer volume change of the transition metal oxide during the charge and discharge process.The Mo S2-Ni O composite achieves a specific capacity of 1100 F g-1 at a current density of 0.5 A g-1.In addition,the Mo S2-Ni O-2//Mo S2-Fe2O3 asymmetric supercapacitor was assembled with these composite materials and exhibited a high energy density of 39.6 W h kg-1 with a long cycle life and excellent rate capability.（3）The molybdenum disulfide-nitrogen-rich carbonized polypyrrole（Mo S2-NCP）2D composites with highly conductive interpenetrating network,large specific surface area and excellent structural stability were obtained by coating the prepared f-Mo S2 nanosheets with nitrogen-rich carbonized polypyrrole,and studied its electrochemical properties as an anode material of lithium ion battery.The composite material can effectively prevent the re-stacking of molybdenum disulfide sheets and the Mo S2-NCP hybrids with a morphology of nanosheets display high packaging density,which further increase volume energy density of the whole electrodes.The ultra-thin nature also allows rapid diffusion of electrolyte to promote full contact between the lithium ion and the molybdenum sulfide nanosheets.Furthermore,robust adhesion of NCP coatings on Mo S2 via strongly coordinated N-Mo bonds assures an excellent structural stability which is favorable for long time cycling,Electrolytic ions and electrons could rapidly penetrate into the electrode matrix with the polysulfide shuttling mitigated due to largely enhanced atomic interfaces between Mo S2 and NCP coatings.As a result,the optimized Mo S2-NCP hybrid exhibits high charge capacity of 1087.5 m A h g-1 at a 0.1 A g-1,with excellent cyclic stability of over 95.6% after 500 cycles of charge-discharge. |
PDF Full Text Request