Preparation Of Nitrogen-doped Hollow Carbon Material And Sodium Storage Performance

Lithium-ion batteries(LIBs)are widely used in portable electronic devices due to their high operating voltage,high capacity,low self-discharge,and long cycle life.With the rapid development of electric vehicles and electronic equipment,limited lithium on the earth does not satisfy the demand of people.Sodium is an element belonging to the same group with lithium in the periodic table,and the energy storage/release mechanism of the SIBs is similar to the energy storage/release mechanism of the LIBs.In recent years,SIBs have attracted the attention of researchers and have become a promising alternative to LIBs in the field of large-scale electric energy storage due to the low cost and abundant content.Sodium ions have a larger ionic radius than lithium ions,so materials used as anode for LIBs are not suitable for SIBs.At present,it is critical to develop anode materials suitable for SIBs.At present,researchers have found that anode materials for SIBs include various carbonaceous materials,sodium ternary compounds,metal nitrides,metal oxides,phosphorus and alloys.However,carbonaceous materials are the most promising anode materials for SIBs in many anode materials because they are inexpensive,easily available,and non-toxic.In order to further improve the electrochemical performance of carbonaceous materials as anode material for SIBs,the materials with large specific surface area are prepared by constructing a novel nanostructure,which can provide more active sites to increase the sodium storage capacity.In addition,doped heteroatom is also a common and effective method.The heteroatoms(N,S,P,B)are doped into the carbon skeleton,which can effectively improve the conductivity of carbonaceous materials and cause defects to increase the storage of sodium capacity.This paper mainly studies the electrochemical performance of nitrogen-doped carbon materials as the anode for SIBs,and improves the electrochemical performance by doping with heteroatoms and constructing novel nanostructures.(1)Nitrogen-rich hollow microspheres(NGHM)were synthesized by a simple calcination of the graphene oxide coated polystyrene(PS@GO)micro spheres in the presence of melamine.During calcination,the PS microspheres are removed and the GO is reduced.At the same time,the pyrolysis reaction between GO and melamine will dope nitrogen into the graphite structure of the GO.When NGHMs are used as anode material for SIBs,NGHM exhibits excellent electrochemical performance such as high specific capacity(reversible capacity of 238.6 mAh/g after 260 cycles at a current density of 100 mA/g),excellent cycle stability(77.8 mAh/g reversible capacity after 8,000 cycles at a current density of 10 A/g)and excellent rate performance(reversible capacity of 66.7 mAh/g at a current density of 20 A/g).(2)Nitrogen-doped Carbon Nanocube(NCC)was obtained by the template method.Dopamine is both raw material and the source of nitrogen.The material with nitrogen doped and large specific surface area exists excellent electrochemical performance as anode material for SIBs.The discharge specific capacities at the current densities of 200 mA/g and 20 A/g were 251.5 mAh/g and 127.8 mAh/g,respectively.The above results indicate that NCC has good cycle stability and excellent rate performance.