Study On Synthesis Of Hirarchical MoS₂/C Materials And Its Excellent Properties Of Lithium Storage

Li-ion batteries(LIBs) have been widely applied in portable electronic devices, and are now being considered as the power sources for electric vehicles and hybrid electric vehicles owing to their attractive energy density, environmental friendliness, and long cycling life. In order to achieve these new applications, technological advancements in LIBs remain urgently necessary to meet the critical requirements on energy, power, and cycling life. One of the most effective approaches is to develop high-performance electrode materials. Mo S2 possesses a layered structure analogous to graphite. The S-Mo-S sandwich layers are hold together by weak van der Waals forces, which lead to an interlayered space of about 0.62 nm, considerably larger than that of graphite(0.34 nm). Such a wide space makes it an appealing candidate for Li storage. Nonetheless, the concomitant substantial volume expansion generates mechanical strain that causes electrode pulverization and loss of active material/current collector integrity, which lead to the poor life and sluggish dynamic of Mo S2 for Li storage. In this paper, wo greatly improve the electrochemisical performance of Mo S2, through synthesis hierarchical Mo S2/C microspheres. The contents include the following aspects:Monodisperse sulfonated polystyrene(SPS) microspheres are employed as both the template and carbon source to prepare Mo S2 quasi-hollow microspheres encapsulated with porous carbon. The synthesis procedure involves the hydrothermal growth of Mo S2 ultrathin nanosheets on the surface of SPS microspheres and subsequent annealing to remove SPS core. Incomplete decomposition of SPS during annealing due to the confining effect of Mo S2 shells leaves residual porous carbon in the interior. When being evaluated as the anode materials of Li-ion batteries, the as-prepared C@Mo S2 microspheres exhibit excellent cycling stability(95% of capacity retained after 100 cycles) and high rate behavior(560 m Ah g-1 at 5 A g-1).Hirarchical Mo S2 microspheres are synthesized through hydrothermal methods with PVP surfactants as the structure-directing agent and the template. After the reaction, residual conductive carbon is absorbed on the surface of Mo S2, forming uniformly-hierarchical Mo S2/C nanocomposites. The electrochemical performance of the Mo S2 nanocomposites are further improved by the addition of 0.8 g PVP surfactants. After 100 cycles, the specific capacity of the Mo S2 nanocomposites still remains 805 m Ah g-1. When the current density reaches 5A g-1, the specific capacity can still remain 700 m Ah g-1, with a capacity rentention of 78.6%.Mo S2/C precursors are successfully synthesized via spray drying method with addition of different carbon sources and subsequent calcination in Ar atmosphere leads to the successful formation of Mo S2 hollow microsheres. The electrochemical properties of the Mo S2/C nanocomposites synthesized above are significantly improved compared to that of bulk Mo S2. The next step is to improve the cycling ability of the Mo S2/C nanocomposites synthesized via spray drying.