Preparation Of Sulphide Mineral/Graphene Composite Electrode Materials By Microwave

Transition metal sulphide have recently emerged as a promising candidate to serve as the anode in lithium-ion batteries due to its advantages of non-toxic,low cost and high theoretical capacity.The defects of large volume change and low conductivity of the transition metal sulphide can be effectively improved by getting nanosized materials and composite with carbon materials.In many researches,sulphide anode materials are synthesized by chemical methods.The synthesis conditions are relatively complex,time-consuming and high cost.The natural sulphide minerals are abundant worldwide in resource and very low in cost.Therefore,the cost of sulphide mineral based anode materials can be greatly reduced if natural sulphide minerales can be used as the raw material.Herein,we synthesized sulphide mineral nanoparticle/graphene composites using bulk natural sulphide minerales by a simple and rapid microwave shock method.The effects of different preparation conditions on the physical and electrochemical properties of the composites were investigated.Therefore,the present work provided not only a solution for decreasing the cost of battery materials,but also a new idea for high-value application of natural minerals.The main results are as follows:?1?A new molybdenite/graphene composite?MoS₂/NG-MW?was prepared through electrostatic attraction with nitrogen doped graphene and microwave treatment.The composite material has flower cluster structure,larger specific surface area and higher mechanical strength.The specific discharge capacity of MoS₂/NG-MW sample is 454.4 mAhg^-1 after 200th cycles,with coulomb efficiency above 98%.?2?Using molybdenite as raw material,nanostructured MoS₂/rGO composites were successfully prepared by simple microwave shock method.The experimental results demonstrated that the material size can be effectively reduced by microwave shock.The particle size changed from micrometer to nanometer in an ultra-short period of time,and the nanoparticles were uniformly distributed on the graphene nanosheets in the composites.At the same time,the decrease of functional groups on the surface of graphene enhances the conductivity of the composite.Therefore,compared with the raw mineral,the rate and cycle performance of the microwave treated electrode materials have been significantly improved.The lithium storage mechanism of MoS₂materials in the charge and discharge process was analyzed by ex-situ XRD and SEM test,combined with voltammetry and constant current charge/discharge test.?3?Using natural sphalerite as raw material,ZnS/graphene nanocomposites with different proportions of raw materials were successfully prepared by simple and rapid microwave shock method.The composition,phase and electrochemical properties of the samples synthesized under different microwave conditions were studied.The results showed that the particle size of ZnS particles decreased by more than three orders of magnitude after microwave shock,and the ZnS particles were loaded uniformly on the graphene layer.The composition of ZnS did not change before and after microwave,but the high temperature and sudden cooling of microwave treatment made part of sphalerite change to wurtzite.As the anode material of lithium-ion battery,the electrochemical performance of nano ZnS/rGO composite electrode is significantly improved compared with that of Pristine ZnS electrode.?4?A new synthetic method of preparing graphene based nanocomposite electrode materials was proposed through freeze-drying and microwave treatment.After freeze-drying,the composite has a three-dimensional network structure,which is conducive to the subsequent microwave absorption and greatly improves the effect of microwave impact.The nanoparticles prepared by this method have small particle size and uniform distribution on graphene matrix.