Structure Design Of Carbon Nanofibers For Energy Storage Based On Electrospinning

Carbon nanofibers have the advantages of high strength,light weight,high heat conduction and high conductivity,and are widely used in energy storage field.Electrospinning is one of the simple and efficient methods to prepare carbon nanofibers.However,how to optimize the design of carbon nanofibers with high energy storage performance through electrospinning is still a great challenge.In this paper,the effect of beads-on-string carbon nanofibers and single atom copper doped carbon nanofibers on energy storage was investigated by electrospun technique,and the conclusion follows:1.Beads-on-string carbon nanofibers are a common phenomenon in electrospun,but it is not clear how beads affect sodium storage behavior.For this reason,by controlling the precursor concentration,we designed the polyimide-based beads-on-string carbon nanofibers to investigate the sodium storage behavior.When used as free-standing electrode for sodium ion battery,beads-on-string can inhibit the storage behavior of sodium ions in the plateau region,that is,insertion/extraction reactions.When used as slurry-coating electrode for sodium ion battery,beads-on-string do not affect the storage behavior of sodium ions,and show good cycling stability.After cycling for 1000 cycles at 5 A g-1,the capacity remains at 110 mA h g'1 with a retention of 88%.2.Single atom metal doped carbon material is a hot spot in the field of energy storage,but it is still a great challenge to flexibly design single atom metal with controllable loading.A single-atom copper doped carbon nanofibers was prepared by using polyacrylonitrile and copper nitrate as precursors.The controlled loading of copper atoms was achieved by controlling the precursor ratio,and the highest copper content was 8.57 wt%.The Cu atom is coordinated with three N atoms to form Cu-N3 structure.Ncoordinated Cu atoms can not only improve the Li-ion difusion kinetics,but also act as reversible Li-ion storage sites.Therefore,when used as anode for lithium ion battery,it shows excellent rate performance,and the specific capacity can reach 435 mA h g-1 at 2 A g-1.Further assembled into lithium-ion capacitors,it demonstrates high energy density and power density.