Preparation Of Molybdenum Disulfide Composites And Their Lithium Storage Properties

The main way to effectively ease the energy crisis and environmental pollution is to develop and apply electric vehicles.High-performance batteries that are most likely to meet the demand for electric vehicles and hybrid electric vehicles in today’s society are considered as lithium-ion batteries（LIBs）because of their advantages such as long service life,high energy density,and environmental friendliness.Until now,graphite has been the material of choice for the negative electrode of lithium-ion batteries（LIBs）because of its high Coulombic efficiency and good cycle stability,with a theoretical capacity of 372 mAh g^-1,which limits the energy densities of lithium-ion batteries（LIBs）.In addition,the low Li⁺diffusion(10^-8 cm²s^-1)in the graphite structure reduces the energy density of lithium ion batteries（LIBs）and remains a major obstacle in EV applications.Therefore,many researchers devote themselves to the development of new capacity negative electrode materials.Among many alternatives to anode materials,molybdenum disulfide（MoS₂）has attracted the attention of researchers for its large specific theoretical capacity(670 mAh g^-1).At the same time,its larger interlayer spacing provides favorable conditions for the insertion/extraction of lithium ions and has good application prospects in lithium ion battery（LIBs）materials.The main contents of this paper are as follows.:The second chapter is the synthesis of composite materials of molybdenum disulfide and graphene by in-situ hydrothermal synthesis and the effect of composite materials on the electrochemical performance of lithium ion batteries（LIBs）.The SEM,TEM and other characterizations show that the uniform growth of MoS₂ on graphene shows that the interlayer spacing of MoS₂ increases from 0.65 nm to 0.95 nm by XRD.Battery performance tests show that the cell cycle can be maintained at 1030.6 mAh g^-1 for 50 cycles at a current density of100 mA g^-1 and 725.5 mAh g^-1 for 50 cycles at a high current density of 1000 mA g^-1.The improvement of the electrochemical performance of the composites is related to the excellent properties of graphene itself.Under the premise of utilizing the high specific capacity of molybdenum disulfide,the interlayer spacing of molybdenum disulfide is increased by the combination with graphene,and the stability of the structure is enhanced Nature,improve the conductivity of the material,thereby enhancing its electrochemical properties.The third chapter synthesized Mo₂C/MoO₂@MoS₂ composites,we use solid-liquid reaction,annealing,hydrothermal and other steps to synthesize molybdenum sulfide and molybdenum carbide and molybdenum oxide composite,and its microstructure,surface morphology and electrochemical Performance and other characterization.Battery test results show that at a current density of 100 mA g^-1,a voltage range of 0.01-3 V,it is clear that the cycling performance of MoS₂ is the worst.After 50 cycles,the reversible capacity has dropped to 50.1 mAh g^-1 with only 14.56%of the initial capacity.The reversible capacity of Mo₂C/MoO₂ nanobelt decreased to 522.2 mAh g^-1 at 50 cycles and the capacity retention rate was 76.50%.However,the Mo₂C/MoO₂@MoS₂ composites still have a capacity of 833.5mAh g^-1 at the 50th cycle.It can be seen from the cycle curve that the electrochemical stability is good.