Study The Lithium Storage Performance Of MoS₂-based Composites

lithium-ion batteries?LIBs?have many merits,such as high energy density,environmentally friendly feature and light weight,thus the LIBs have a wide range of application as a secondary energy.However,the commercial graphitic anodes possess low specific capacity(372 mA h g^-1).It is one of the important research directions to search for the higher capacity of environment-friendly non-carbon anode materials in lithium ion batteries fields.Molybdenum disulfide?MoS₂?with higher specific capacity(670 mA h g^-1)and graphene-like lamellar structures have attracted widely attention in recent years.The electrical conductivity of MoS₂ itself is very poor,which can deadly affect the electrochemical performance.The volumetric expansion of MoS₂ existed during the lithium insertion/extraction process can also contribute to the pulverization of the electrode materials.Therefore,in order to resolve the above-mentioned drawbacks of MoS₂,MoS₂ decorated by graphene or carbon-containing compounds are synthesized in this paper to improve the electrochemical performance.The MoS₂/N-doped graphene composites are prepared by the hydrothermal method.The effect of hydrothermal systems with ethylenediamine additive on the morphology and electrochemical behavior of the prepared composites are investigated.The microstructure and morphology of the as-obtained composites are characterized by SEM,TEM and XRD methods.The results exhibit that MoS₂/N-doped graphene composites retain the morphology of graphene hydrogels.The ultrathin MoS₂ nanosheets selectively grow on the graphene.The synergistic effect between the MoS₂ and graphene inhibits the restack of each other.The discharge/charge cycling test indicates that when the concentration of ethylenediamine is at 0.2 mol L^-1,the composites exhibit improved electrochemical performances,i.e.the enhanced cycling stability with reversible capacity of 816.6mA h g^-1 at 200 mA g^-1 after 120 cycles and remarkable high-rate capacity of 683.8mA h g^-1 at 2000 mA g^-1.The polyaniline?PANI?as nitrogen-containing carbon source is coupled with MoS₂/N-doped graphene composites and the as-obtained composites are designated as MoS₂/NG/NC.The impacts of different amount of PANI and calcination temperatures on the MoS₂/NG/NC composites have been investigated.When the mass ratio of MoS₂ and polyaniline is 1:2,the MoS₂/NG/NC composites exhibit a higher and stable cycling performance.In addition,when the calcination temperature reaches800?,theMoS₂/NG/NCelectrodedisplaysbetter intercalation/deintercalation performance.The reversible capacity keeps 761.9 mA h g^-1 at 200 mA g^-1 after 200 cycles.In addition,the MoS₂/C composites are synthesized using the ball-milling method.The well-prepared MoS₂ are coated with glucose and PANI and the obtained composites are calcined to carbonize the glucose and PANI.The analytical results illustrate that both the composites show stable cycling performance.The MoS₂coated with caronized PANI show more excellent electrochemical performance,i.e.the reversible capacity maintaining 581.4 mA h g^-1 at 200 mA g^-11 after 500 cycles.