Design And Preparation Of CoSe2/Carbon Nanofiber Composites As Anode Materials For Sodium-ion Batteries

Compared with other battery systems,sodium-ion battery has the advantages of abundant resources,low price and friendly environment,regarding as considerable potential secondary battery in the field of large-scale energy storage.The key to the further development of sodium-ion battery is to develop high-performance electrode materials.In this paper,CoSe₂@CNFs composite material for sodium-ion battery anode was studied.The main research contents and obtained results are as follows:?1?Co@CNFs composites,the precursor of CoSe₂@CNFs,were prepared by electrospinning and subsequent carbonization heat treatment process,and the influence of heat treatment process on the morphology and structure of Co@CNFs was studied.The size of Co nanoparticles was optimized by adjusting the parameters of heat treatment process.The experiment found that the Co nanoparticles were randomly embedded in the carbon nanofiber matrix.When the carbonation time was 1 hour,the size of the Co nanoparticles in the Co₁@CNFs composite was 5-20 nm,and the material presented a flexible three-dimensional network structure with the best mechanical properties.The experiment also found that the nitrogen element in the electrospinning source material resided in the carbon nanofibers,which realized the in-situ nitrogen doping in the process of carbon fiber preparation.?2?The CoSe₂@CNFs composite material was prepared by sintering the mixture of precursor material Co₁@CNFs and selenium powder,and the influence of parameters such as selenization temperature and selenization ratio on the phase composition,morphology and structure of CoSe₂@CNFs composite material in the process of heat treatment selenization was studied.The experimental results showed that when the selenization temperature was 400?and the selenization mass ratio was 1:1,the uniform size of CoSe₂ nanoparticles was randomly embedded in the carbon nanofibers.The escape process of CoSe₂ nanoparticles from carbon nanofibers was also observed with the increase of selenization ratio.?3?The electrochemical properties of CoSe₂@CNFs composite and precursor Co₁@CNFs for sodium-ion batteries were investigated.The self-supporting structure of the three-dimensional network allows them to be used directly as the negative electrode of sodium-ion batteries,no binder,no conductive agent.The active material CoSe₂ particles embedded in carbon nanofibers can effectively improve the utilization of CoSe₂.The electrochemical test results show that the CoSe₂@CNFs composite electrode has excellent cycling performance and rate performance.Under the large current density of 1A g^-1,the specific capacity remains at 175 mAh g^-1 after 400 cycles.The experiment also measured the reversible capacity of 221 mAh g^-1 in the first cycle at the current density of 0.1 A g^-1,using the selenized precursor Co₁@CNFs directly as the electrode.