Study Of Freestanding Anode Materials By Electrospinning For Lithium-and Sodirum-ion Secondary Batteries

Since commercial lithium-ion battery had been launched for the first time by SONY company in 1991,lithium ion batteries(LIBs)have received wide attention of researchers and consumers due to their high energy density,long cycle performance,low self-discharge rate,no memory effect,light weight and portability.In recent years,with the development of electric vehicles and large-scale energy storage devices,lithium-ion batteries with better electrochemical performance are demanded.Meanwhile,sodium-ion batteries also show great potential recently in the world because of abundant resources and low prices.Sodium-ion batteries are also considered as promising batteries for large-scale energy storage devices such as smart grids.Generally,the electrochemical performance of the batteries is largely determined by the composition and structure of electrode materials.Currently,carbon materials are the most promising anode materials for batteries.Although carbon materials as anode electrodes have stable electrochemical properties,its specific capacity cann't satisfy the requirement of their future batteries.Therefore,it is of great significance to explore and develop high-capacity anode materials for lithium/sodium ion batteries.In this paper,a series of freestanding composites based on 3D-structured carbon fibers as anode electrodes have been prepared using novel and simple electrospinning method.The chemical component and microstructure of as-synthesized composites were further characterized and analyzed.The superior electrochemical performance of the free-standing electrode materials in this paper has been verified.And the main research contents are listed as following:The heart/coronary structured silicon/graphene @carbon fibers was synthesized by electrospinning.The composite materials as anode for lithium ion batteries have outstanding electrochemical performance.The reversible specific capacity of G/Si @CFs composites can reach up to 1036.7 mA h g-1 at current density of 100 mA g-1,which is four times more than that of commercial high-performance graphite anodes.After 200 charge and discharge processes,the specific discharge capacity of G/Si @CFs composites was 896.8 mA h g-1,and the capacity retention rate was 86.5%.Under current density of 1000 mA g-1,G/Si @ CFs can also have a high discharge specific capacity of 543 mA h g-1.Flexible phosphorus/carbon fiber(P/CFs)composites were prepared by electrospinning and evaporative condensation for the negative electrode of a sodium-ion battery.At the same time,fiber surfaces were covered by reduced graphene oxide film using infiltration method to fabricate novel phosphorus/carbon fiber@reduced graphene oxide(P/CFs @ RGO).P/CFs @ RGO has a very stable electrochemical performance,and the specific capacity of reversible discharge of the self-supporting P/CFs @ RGO electrode can reach 958.7 mA h g-1 at current density of 50 m A g-1.The specific discharge capacity was 725.9 mA h g-1 after 55 cycles,and the electrode capacity retention rate was 75.7%.The P/CFs @ RGO composites still have excellent electrochemical properties at high current densities.Under high current density of 1 Ag-1,the P/CFs @ RGO electrode can still have 406.6 mA h g-1 after 180 cycles,in which capacity contribution of P element is about 1179.9 mA h g-1.