Preparation And Properties Of Graphene-coated Copper Matrix Composites For Lithium Ion Batterie

In the era of rapid development of mobile communication,our lives are increasingly dependent on the use of electronic devices such as mobile phones,laptop computers and charging treasures,and this is due to the development of lithium-ion batteries.Lithium-ion batteries have the advantages of high operating voltage,high energy density and long working life.However,the commonly used negative electrode of lithium ion batteries is made of graphite material,and the theoretical capacity is only 372 mAh/g,which is difficult to meet people's growing application needs.In alternative negative materials,Copper based materials which is transition metal oxide,step into people's vision for the advatage of rich resources,low price,large mass production,high reversible capacity and excellent cycle stability.The main research content and conclusions were as follows.In this paper,novel in situ composite LAPN and spray drying methods were used to prepare graphene coated cuprous oxide microparticles?GCU?,graphene coated copper oxide micron particles?GCO?and cobalt doped graphene coated copper oxide micron particles?OGCO?.These three materials exhibit excellent electrochemical performance in the negative electrode of lithium ion batteries.The main work of this paper is as follows:?1?preparation of graphene coated copper oxide micron particles?GCU?:using water as dispersant,industrial copper oxide?CuO?and liquid polyacrylonitrile?LPAN??mass ratio22%?developed in laboratory were in situ composite.After spray drying,the GCU of nuclear shell structure was sintered at low temperature under N₂ atmosphere.In this experiment,by examining the XRD results of materials placed at different lengths of time,it was found that the diffraction peaks did not change substantially,demonstrating that they can exist stably in the air.The influence of low-temperature sintering temperature on the structure and properties of the material was further discussed.Through the combined analysis of TG,XRD,XPS,SEM,TEM,and electrochemical properties,it was found that the pure GCU could be obtained by sintering at 320?.In addition,the experiment also explored the effect of adding different proportions of LPAN on the reduction of Cu²⁺in the thermochemical process.It was found that,within a certain amount of addition,a pure phase GCU material with different carbon content can be prepared by controlling the temperature.?2?For the direct low-temperature sintering of GCU materials,the carbonization degree of the cladding material is low and the electrochemical performance is poor.In this experiment,the composite material?GCU?was carbonized in a nitrogen atmosphere at1400?.,and then in an air atmosphere at different temperatures.Under the conditions,the core-shell structure of graphene-coated copper oxide composites?GCO?was successfully prepared by further oxidation.This article mainly discusses the effects of different oxidation temperatures on the structure and properties of materials during the preparation process.By analyzing the XRD and XPS results,it was found that the composites prepared under different conditions were all CuO and Cu₂O composites.By comparing the SEM images of the material,it was found that all the materials were micrometer-sized spherical particles,and the surface of the material prepared at 460?was a perfect porous structure.By comparing the electrochemical properties of the material,it was found that the initial discharge specific capacity of the GCO oxidized at 460?was 826.0 mAh/g,and the discharge specific capacity gradually increased from 336.6 mAh/g on the second cycles to 497.2 mAh/g on the 200th cycles,an average increase of 0.8mAh/g per cycle.After a long-term cycle of materials,the increase in capacity may be caused by the reversible formation and decomposition of lithium oxide during the cycle.At the same time,the composite effect of graphene-based carbon shells can also promote the reversible formation/decomposition of lithium oxides.Reaction with electrolytes.?3?Based on the previous experiments,this chapter further explores the influence of doping different proportions of Co on the structure and properties of materials in the material preparation process.The cobalt-doped graphene-coated copper oxide microparticles?OGCO?were obtained by doping Co?CH₃COO?₂ after spraying and then oxidizing after high temperature sintering.Through comprehensive analysis of XRD,SEM and TEM results of the material,it was found that the doped Co element perfectly combines with the composite material in the sintering oxidation process.By comparing the electrochemical properties of Co doped materials prepared under different ratio conditions,it was found that the material prepared under the condition of Cu:Co=5:5 maintained a 555.6 mAh/cycle after 100 cycles at a current density of 50 mA/g.The reversible capacity of g is greatly improved compared to other conditions.This may be a suitable doping ratio.The heterogeneous structure formed between the oxides of different elements produces a multi-component synergistic effect.The graphene shell structure may increase the conductivity of the electrode material and suppress the volume expansion of the metal material within the shell,making The electrochemical performance of the material has greatly improved.