Preparation Of MoS₂/MoSe₂/CN And Application As Anode Materails Of Sodium-ion Batteries

Since the beginning of the 21st century,the widespread use of lithium-ion batteries has led to the emergence of the shortage of lithium resources on the earth.As a potential replacement for lithium-ion batteries,sodium-ion batteries have gradually become a new star in the field of energy storage,but the lack of suitable anode materials has been restricting the further development of sodium-ion batteries.Among many negative electrode materials,molybdenum disulfide（MoS₂）has the advantages of low cost and high capacity.MoS₂is a typical two-dimensional material with a high specific surface area,but MoS₂is easy to stack in layers during the preparation process,and the two-dimensional material is easy to collapse during the charge and discharge cycle,which affects its cycle stability.In order to improve the application of MoS₂on the negative electrode of sodium ion batteries,this paper intends to use dicyandiamine as the carbon source to synthesize MoS₂/C through high temperature annealing in one step to increase the stability of MoS₂during charge and discharge.Then the selenium powder is used as the selenium source to prepare MoS₂/MoSe₂/C to improve the conductivity of the material.And use morphology characterization,composition analysis,electrochemical performance test and other means to further reveal the sodium storage mechanism of the two materials.The specific research content of this article is as follows:Using dicyandiamine as a carbon source to synthesize MoS₂/C,through a series of characterizations,a two-dimensional oligolayer MoS₂/C composite material can be prepared when dicyandiamide is used as a carbon source,and the interlayer spacing of MoS₂ is 0.61 The expansion of nm to 0.65 nm is more conducive to Na+intercalation.Three samples were prepared by adjusting the annealing temperature,and the pseudocapacitance ratio of the samples made by annealing at 600°C reached 99.56%.The initial specific capacity is 424 mAhg^–1 and the specific capacity eventually rises to500 mAhg^–1.The specific capacity remains above 100 mAhg^–1after 10,000 cycles at a current density of 50 Ag^–1,and the battery can be fully charged in just 5 seconds by charging at a current density of 50 Ag^–1.The MoS₂/MoSe₂/C composite material was prepared by annealing at 600℃with selenium as the selenium source.After characterization,it is determined that MoS₂/MoSe₂/C is a two-dimensional oligo-layer material and the layer spacing is further expanded to 0.67 nm.The electrochemical performance test of MoS₂/MoSe₂/C showed that the introduction of MoSe₂ increased the pseudocapacitance ratio of the material to 99.99%;the rate performance test showed that the initial specific capacity was 524 mAhg^–1,and the current density reached 50 Ag^–1 It still has a specific capacity of 130 mAhg^–1;the cycle stability test results show that the sample is charged and discharged 40,000 times at a current density of 50 Ag^–1 and the specific capacity remains above 105 mAhg^–1,and the high current charge and discharge performance It is further improved,which proves that MoSe₂ increases the electrochemical activity and conductivity of the material.