Preparation Of Monoatomic Copper Doped Carbon Fiber Films And Their Protective Properties For Sodium Metal Anode

Sodium metal anode has high theoretical capacity(1166 mA h g-1)and low potential(-2.70 V vs SHE),which shows a good application prospect.However,the interface between sodium metal and electrolyte is unstable,and it is easy to form dendrites,resulting in low coulomb efficiency and poor cycle life.The self-supporting carbon material doped with monatomic metal is expected to stabilize the interface of sodium metal and inhibit the growth of dendrite.However,monatomic metals have high surface energy and are easy to agglomerate,leading to a low load,which can not meet the needs of practical application.In order to solve the above problems,a high content monatomic metal doped carbon fiber film was designed,which showed good electrochemical properties for sodium metal anode protection.Details are as follows:Using copper nitrate,zinc chloride and polyacrylonitrile as raw materials,the flexible self-supporting carbon fiber films doped with single atom copper were prepared by electrospinning,stabilization and carbonization.The monatomic copper content is up to 10.15wt%and is anchored by cocoordination of nitrogen and oxygen atoms.We investigated the plating/stripping behaviors of sodium metal in monoatomic copper doped carbon fiber films.It was found that the highly dispersed mono-atomic copper as a sodiophilic site could reduce the nucleation barrier of sodium metal and induce the uniform nucleation of sodium.The flexible selfsupporting carbon fiber films not only disperse the local current density but also buffer volume expansion.The film used as a protective coating for sodium metal negative electrode shows good performance:When the current density is 1 mA cm-2 and the surface capacity is 1 mA h cm-2,the half cell of sodium metal can cycle 1200 times stably,and the coulomb efficiency is up to 99.8%.The symmetrical battery operated for 2500h stably under the conditions of 1 mA cm-2 and 1 mA h cm-2,and the voltage lag was only 10 mV.Even at high current up to 10 mA cm-2 and surface capacity up to 5 mA h cm-2,it can still operate steadily for 120 h.The battery is assembled with sodium vanadium phosphate,and the capacity can still reach 90 mA h g-1 at a current density of 1 A g-1 for 1000 cycles,and the capacity retention rate is up to 98.7%.