Electrochemical Performance Of Carbon Anode Materials For Sodium Ion Batteries

Lithium ion batteries plays an important role in the current energy storage system market and the demand for lithium resources is increasing rapidly.However,the supply is in short supply,and there is an urgent need to find alternatives.The once-forgotten sodium ion batteries have regained attention.The same working principle and a large number of related researches have made the development of sodium ion batteries rapid.However,for sodium ion,the layer spacing of graphite is too small,resulting the poor capacity.In order to adapt to the development of higher market requirements,various carbon materials have been repeatedly studied.At present,researchers tend to prepare more holes for carbon materials,and strive to make electrode materials obtain more active sites;secondly,the incorporation of non-metallic atoms can also improve the discharge capacity of electrode to a certain extent.In this paper,we conducted a comparative analysis of three designed carbon materials and conducted in depth research of the best one.Three kinds of carbon nanofibers were successfully prepared by simple electrospinning technology and hard template method.According to the analysis and comparison,the various physical properties of the three carbon materials,including the carbon structure shown by XRD and Raman,main pore size type and external morphology,are not significantly different.And the most different physical properties,specific surface area,has a linear relationship with the proportion of hard template of precursor,which has a linear relationship with the reversible capacity of the three electrodes.Therefore,it is enough to prove the controllability of the carbon material design and the effect of the number of holes on the carbon electrode.The most promising carbon material mentioned above is named loofah-like carbon fibers because of its unique morphology,which is mainly caused by a large number of hard templates arranged in a linear shape under the mutual attraction of their magnetism and the effect of carbon walls.The unique design makes the material have lower strain force,higher stability and faster ion diffusion.When finally applied to sodium ion batteries,it can show ultra-long life and high reversible capacity.At room temperature,the electrode had the reversible capacity of 269 mAh g-1 after being charged and discharged at 500 mA g-1 for 2000 times;after 5000 cycles at high current density of 10 mA g-1,the specific capacity can be maintained at 143 mAh g-1.At a high temperature of 50? and a high current density of 15 mA g-1,the specific capacity of the electrode was very stable,and there was still 156 mAh g-1 after ten thousand cycles.In the full battery,the electrode also exhibited good performance,and the specific capacity could reach 182 mAh g-1.The high capacity and stability of electrode materials can be verified by the analysis of pseudocapacitive behavior and dynamic calculation.Capacitive control analysis combine with ex-situ Raman are used to verify the existence of intercalation and adsorption reactions during the charging and discharging.The influence of nitrogen doping can be calculated by different nitrogen doping models.The combination of nanopores and pyrrole/pyridine nitrogen can effectively improve the adsorption of sodium ions on carbon,thus improving the capacity of carbon materials.Therefore,loofah-like carbon fibers is expected to become the anode materials of a new generation of sodium ion batteries to replace the status of lithium-ion batteries.