Preparation And Electrochemistry Properties Of Nitrogen-Doped Hollow Carbon Nanospheres

Nitrogen-doped hollow carbon and yolk/shell nanospheres have inspired considerable attention due to their novel structure and morphology.However,the formation of internal hollow structure and the regulation of internal structure remains challenges.The most traditionally used methods are template-based routes and high temperature and high pressure synthesis methods.The synthesis of the above structures by hard template method requires multi-step complex operations.The removal of the template mainly use HF,NaOH and other strong corrosive solvents.The traditional soft template method needs to choose the appropriate surfactant and has poor control on the sphericity of the sphere.Other methods always need harsh reaction conditions and high energy consumption.In this paper,the nitrogen doped hollow and yolk/shell polymer nanospheres were prepared by controlling solubility at room temperature.Firstly,the order of the m-phenylenediamine and melamine participating in the reaction was adjusted according to the difference of solubility and reaction rate.Solid polymer nanospheres with intraparticle difference were prepared successfully.According to the difference of internal and external structure of solid polymer spheres and the reversibility of Schiff base reactions,the solid spheres were immersed in formaldehyde solution to achieve the dissolution of the inner core.Then the nitrogen doped hollow spheres was obtained.The important parameters of hollow nanospheres can be regulated.The diameter of the hollow spheres can be adjusted from 320nm to 1.5?m and the thickness of the shell can be adjusted from 35 nm to 135 nm.After exploring the influence of different solvents on the polymer stability,the paper also soaked the the solid polymer nanospheres in methanol.As a result the core was partly dissolved and the yolk/shell polymer nanospheres were prepared.By further adjusting the parameters of reaction and post-treatment,the particle size,shell thickness and the size of yolk can be regulated.The size of yolk can be adjusted from 30 nm to 250 nm.The two new synthesis methods overcome many disadvantages of traditional methods and provide new ideas for the synthesis of nitrogen doped hollow and yolk/shell structure nanospheres.The specific surface areas of the two nitrogen doped carbon spheres were 2462.3 m³g^-1and 2772.5 m³g^-1,respectively,after carbonization of nitrogen doped hollow and yolk/shell polymer nanospheres.The two types of nanospheres have high nitrogen content?mass percentage over 12%?and large internal spaces.Using the above advantages,two carbon materials were used as the cathode material in lithium sulfur battery,the capacity of cell were528 m Ah g^-11 and 534 m Ah g^-11 after 300 cycles at the current density of 0.5 C.The battery has high capacity and high cycling stability,which can effectively solve the problems existing in the cathode materials of lithium sulfur batteries.