| Development and application of electric vehicles(EVs) can effectively relieve the worldwide pollution and energy crisis. Lithium-ions batteries(LIBs), with its advantages of high energy density, long cycle life and environmental friendliness, have been regarded as the most promising candidate for the next-generation energy storage device. However, the application of LIBs in the EVs/HEVs is hampered by the commercial graphite anode, whose theoretical capacity is limited to 372 m A h g-1. So, as a result, significant effort has been devoted to exploit alternative anode materials with higher capacities. Molybdenum disulfide(Mo S2) is the focus of recent research interest owing to its high theoretical capacity(~670 m A h g-1).Molybdenum disulfide(Mo S2) has a typical layered structure held together by weak van der Waals forces, which is similar to graphite. The adjacent layers spacing of Mo S2 is 0.615 nm, significantly larger than that of graphite(0.335 nm). Due to these desirable properties, Mo S2 can be easily intercalated by lithium ions. Therefore, it can be regarded as a superior electrode material for LIBs. However, the performance of bulk Mo S2 is still unsatisfactory when used as anode materials in LIBs, suffering from rapid capacity fading because of its poor electrical/ionic conductivity and drastic volume change upon Li+ insertion/extraction. To solve the problems mentioned above, we have conducted work of the following aspects.In the first work, three-dimensional(3D) hierarchical Mo S2/polyaniline(PANI) microflowers were successfully fabricated via a simple hydrothermal method. The crystal structure and morphology of the Mo S2/PANI microflowers were characterized by SEM, TEM, XRD, XPS, and FT-IR spectra. The excellent electrochemical performance of the 3D hierarchical Mo S2/PANI microflowers was demonstrated. Further 3D hierarchical Mo S2/C microflowers can be prepared conveniently by annealing the Mo S2/PANI sample in a N2 atmosphere at 500 °C for 4 h. The obtained Mo S2/C sample exhibited more excellent electrochemical performance, High reversible capacity of 888.1 m Ah g-1 with the Coulombic efficiency maintained at above 90% from the first cycle were achieved at a current density of 100 m A g-1. Even at a current density of 1000 m A g-1, the reversible capacity of the Mo S2/C sample could be retained at 511 m Ah g-1.Two-dimensional(2D) nanosheets have been widely acknowledged to be superior electrode materials for LIBs because of their unique structural characteristics, which can provide shorter lengths and more channels for lithium ions diffusion as well as enhanced kinetics. In the following work, three-dimensional(3D) porous Mo S2/N-doped graphene aerogels were successfully fabricated using Mo S2 nanosheets and graphite oxide as starting materials. During the solvothermal process, the graphene oxide was reduced greatly and doped by the N element using Dimethyl Formamide(DMF) as reactive solvent. Meanwhile, the N-doped graphene and Mo S2 nanosheets as building blocks co-assembled into 3D architectures driven by π-π stacking interactions. The 3D architectures possess high specific surface area, porous structures, and high electrical conductivity. Such novel features combined with the advantage of N-doping which creates defect sites and vacancies for more Li+ ions intercalation together made the Mo S2/N-doped graphene aerogel(mass ratio of 3:1) excellent electrochemical performances including high reversible capacity(1053 m A h g-1 at a current density of 100 m A g-1), as well as good cycling stability and high-rate capability(592 m A h g-1 even at a high current density of 1000 m A g-1) when used as anode materials for LIBs. |
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