Preparation Of MoS₂ Composites And Research On Lithium-electrode Properties

Efficient energy storage is a long-standing technological and scientific problem that has global implications.The requirements of a progressively small scale and considerably large capacity for a wide range of portable,automotive and stationary systems continue to be strong driving forces in developing advanced lithium-ion batteries?LIBs?.Rechargeable LIBs are considered as one of the most promising energy storage devices and a priority candidate for stationary energy storage systems such as consumer products,smart grids and electric vehicle batteries.However,as an widely used anode material,graphite shows a relatively low theoretical capacity?372 mAh/g?and cannot meet the need of large-scale batteries in the future.In comparison with graphite,2D transition-metal dichalcogenides MX2 have been considered as promising anode materials for LIBs based on their unique physical and chemical properties,such as relatively high energy density,long lifecycle and design flexibility.In particular,MoS₂ shows an analogous layered structure of graphene in which molybdenum atoms are sandwiched between two layers of sulfur atoms,which are few of the most stable and versatile members of the layered material family.The layered structure of MoS₂ was reported to have a considerably high theoretical specific capacity of 670 mAh/g,which allows for easy lithium-ion insertion/extraction,Despite of these advantages,MoS₂ suffers from poor cycling and rapid fading capacity,hindering seriously the application of MoS₂ as an anode material for LIBs.In order to study MoS₂ modification that we have done the following work,The first paper reports a facile synthesis nanocomposites of a core-shell structure with MoS₂ nanosheet-decorated TiO₂ microspheres.TiO₂ microspheres were first prepared through the hydrolysis of titanium isopropoxide,which was then modified using cetyltrimethylammonium bromide?CTAB?that is cationic surfactant.The modified surface of TiO₂ with a positive charge easily adsorbed the Mo precursor and reacted with thioacetamide via hydrothermal reaction to produce core-shell structures of TiO₂ microspheres@MoS₂ nanosheets?TiO₂@MoS₂?.Finally,the annealed sample was applied in LIBs;the sample exhibited good lithium performance,showed a reversible capacity of 467 mAh/g at 0.1 A/g after 80 cycles with highly stable capacity retention.In the second work,we report a template approach for the fabrication of N-doped carbon-coated MoS₂ on hollow carbon microspheres?C@MoS₂@PDA?by using titanium dioxide microspheres?TiO₂?as a template material.The TiO₂ microspheres were synthesized for use as the template materials by a simple hydrothermal reaction.The spheres were then coated with a carbon layer,which was then loaded with MoS₂ nanosheets.The nanocomposites were further covered with a thick carbon layer,using dopamine as the carbon source.After annealing at 500 oC in an atmosphere of 2% H2 balanced by Ar for 2 h,the TiO₂ core was removed,forming the 3D N-doped carbon coated MoS₂ nanosheets on hollow carbon microspheres.In serving as the anode material for LIBs,the MoS₂ nanosheets act as a host for Li,providing efficient storage for Li+ ions;in particular,the hollow structure increases the specific surface area of the anode.Meanwhile,the N-doped carbon layer helps to protect the MoS₂ against direct contact with the electrolyte and promotes rapid charge-transfer reactions by providing an efficient electron pathway for fast lithiation-delithiation.The prepared composite material exhibits excellent performance in lithium-ion batteries.