Fabrication Of Flexible Carbon Nanofiber Films Doped With High Content Of Tin Atoms And Their Ude In Sodium Metal Collector

With the advancement and rapid development of electronic technology,lithium ion secondary batteries based on intercalation reactions have reached the limit of energy density.The sodium metal negative electrode has a high theoretical specific capacity and low electrochemical potential,as well as abundant sodium resource reserves and low cost in nature,so the sodium metal secondary battery has become one of the promising candidates.However,the practical application of sodium metal batteries still faces many obstacles:(1)The solid electrolyte interface(SEI)formed by the sodium metal and the electrolyte is extremely fragile and insufficient to inhibit the growth of sodium metal dendrites;(2)Sodium dendrites breakdown The diaphragm will cause serious safety problems;(3)Sodium dendrites are easy to fall off to form dead sodium,which causes internal polarization and irreversible loss of sodium and electrolyte,resulting in low battery life.Therefore,how to suppress the growth of sodium dendrites and design a high-performance sodium metal anode is the current main challenge.In this thesis,polyacrylonitrile and tin salt were used as raw materials to prepare flexible and self-supporting tin atom-doped carbon nanofiber films through electrospinning and pyrolysis.The tin atom is co-coordinated and fixed on the carbon matrix by nitrogen and oxygen,and its content is as high as 30.18 wt%.The high content of tin atoms adjusts the electronic structure of the carbon matrix and improves the sodium-philicity of the carbon matrix.Therefore,The film acts as a metal sodium current collector,effectively induces the uniform deposition of metal sodium,inhibits the growth and volume expansion of metal sodium dendrites,and shows good sodium deposition/stripping efficiency and cycle stability.Under the conditions of a current density of 4 mA cm-2 and a capacity of 1 mA h cm2,the sodium metal half-cell circulates stably for 1000 cycles,and the coulombic efficiency reaches-99.8%;the symmetrical cell runs stably for 1000 hours under the conditions of a current density of 10 mA cm-2 and a capacity of 10 mA h cm-2;the full battery with this electrode circulates stably to 1500 cycles under the condition of 1 A g-1,the capacity remains at 83.7 mA h g-1,and the retention rate is 96.6%.This work provides new ideas for the preparation of high-content metal single atoms and the design of dendritic-free sodium metal current collectors.