A Study On Preparetion Of Nitrogen Doped Carbon Materials By High Pressure Vapor Thermal Reaction And Their Properties

With the deterioration of environment,including smog,greenhouse effect and other environmental problems,it is urgent for the world to transfer the use of fossil fuels to cleaner energy.Lithium ion batteries,one of the hot areas in the application and research of new energy devices,are determined by several components.Anode material is one of the key factors to improve the performance of lithium-ion batteries.Currently,the most widely used anode material is graphite,which has the shortcomings of low specific capacity,slow charge and discharge rate.So,the large scale application and progress of clean energy are restricted seriously.Nitrogen doping is an effective strategy to enhance the conductivity and surface activity of carbon materials,and improve the electrochemical performance.However,the frequently used doping methods possess several drawbacks,including large source consumption,low doping concentration,and severe environmental pollution.To overcome these drawbacks,we develop a novel high pressure vapor thermal reaction method to prepare nitrogen doped carbon materials.Then the lithium storage performance of the obtained materials is characterized.Specific research contents and achievements are as follows:Low toxic and decomposable pyrrole were used as precursors whose ratio of nitrogen to carbon reaches 1:4.Nitrogen doped carbon materials were manufactured successfully within a sealed vessel.The influences of temperature,the mass precursor,reaction time on the morphology,structure,doping concentration and kinds were studied explicitly.Consequently,as the temperature rise,the obtained products change from irregular particles to perfectly spherical carbon materials.The nitrogen doping concentration gradually decline to 4.56%,which yet still ranks at a competitive doping level.The precursor mass' s increase will prompt the irregular powder products converting to spherical carbon materials and the augmentation of nitrogen doping concentration.With the lengthening of reaction time,the products maintain the perfectly spherical feature,but explicit an obvious decrease in nitrogen doping concentration.Under 600 oC for 1 h,using 2ml precursor,regularly shaped nitrogen doped carbon spheres whose nitrogen doping concentration is 6.14% and size range between 1 5 ?m,were successfully manufactured by high pressure vapor thermal reaction for the first time in the research area.The dense packing property of spherical particles can benefit the transmission of electrolyte between the active particle materials.Galvanostatic charge and discharge,cyclic voltammetry and electrochemical impedance spectroscopy were used to assess the lithium storage performances of the products.The carbonization degree and the spherical integrity grow with the rising temperature,and the nitrogen doping concentration rank at a competitive level.So the lithium storage performances will progress.Adding more precursor will improve the spherical integrity and the nitrogen doping concentration,which could enhance the lithium storage performances.Since the lengthening of reaction time only diminish the nitrogen doping concentration maintaining the spherical feature,the lithium storage performances degrade.The nitrogen doped carbon microspheres prepared at 600 °C for 1 h display a reversible capacity of 715.6 mAhg^-1 at the charge /discharge current density of 50 mAg^-1.After charge and discharge for 50 cycles at 50 mAg^-1,the capacity still remains 544.5 mAhg^-1.Even at a high current density of 1000 mAg^-1,the reversible capacity reaches 215.5 mAhg^-1,indicating a remarkable rate capability.The properties of obtained nitrogen doped carbon materials are competitive in the relevant research area and outperform the commercial graphite materials,holding great promise for future practical application.