Preparation And Electrochemical Performance Of Carbon-Coated Mno/graphene As Lithium-Ion Battery Anodes

Manganese oxide has a high theoretical capacity,moderate discharge plateau and lower polarity when it is used as the anode material in lithium battery.However,the issues that limit its application are its poor conductivity and large volume changes,which can easily result in the collapse of electrode structure during long-term cycling.Carbon materials have many advantages such as high conductivity,large specific surface area,flexibility and large pore volume.In order to improve the conductivity of MnO and relieve the large volume change of MnO during the charge-discharge process,we effectively combined MnO and carbon materials to prepare a carbon-coated MnO/rGO nanocomposite with good electrochemical performance.In this paper,MnO-based carbon composites were prepared by high temperature heat treatment.The electrochemical performance of the MnO-based electrode material is optimized by the different preparation methods and the coated carbon source and the addition of graphene,providing a continuous channel for electron transport and ion diffusion.In the meantime,the electrochemical behavior of carbon-coated MnO/rGO composites as lithium anode material has been detailedly studied in this paper to attempt to explain why the carbon coating and the addition of graphene can significantly improve the electrochemical properties of the material.During the experiment,the morphology and electrochemical properties of the materials were described by using XRD,SEM,TEM,CV test,constant current charge and discharge and impedance test methods.Three-dimensional carbon-coated MnO/rGO composite obtained by simple precipitation method,glucose as carbon source and treating with N₂ at 700℃for 6 h has the best electrochemical performance.The electrochemical tests indicate that the prepared 3D carbon-coated MnO/rGO electrode exhibits a high reversible capacity of1247.3 mAh g^-11 and 713.2 mAh g^-11 after 50 cycles at 100 mA g^-11 and 1000 mA g^-1,respectively.The capacity is 792.2 mAh g^-1after 200 long cycles at a current density of 1 A g^-1.In this structure,the graphene sheets are cross-linked with each other to form a three-dimensional conductive network.The three-dimensional conductive network not only provided good conductivity for the composite material,but also effectively dispersed the Mn（OH）₂ precipitate,which laid the foundation for the formation of uniform MnO nanoparticles on both sides of the graphene in subsequent experiments.The carbon protective layer prevents the aggregation of MnO nanoparticles and their fall from the graphene sheet during cycling.The three-dimensional structure of the carbon-coated MnO/rGO nanocomposites synthesized by a simple method showed excellent rate capability and cycle stability.Therefore,the 3D-structured carbon-coated MnO/rGO nanocomposites as lithium-ion battery anode material has a great application prospect.