Preparation And Lithium Storage Performance Of Siliconcarbon Nanofiber Composite Materials

Rechargeable lithium-ion batteries（LIBs）are the most attractive energy storage devices due to their higher energy density,longer cycling life,and lower self-discharge.The limited capacity of 372 mA h/g of graphite anode inhibits its application in the next generation of LIBs.Thus,it is necessary to develop a higher energy density anode material.Silicon（Si）is considered as an attractive candidate anode material in LIBs due to its highest theoretical capacity of⁴200 mA h/g and low electrochemical potential.Up to now,Si-based anode can’t be practically applied for its intrinsic defects characterized by large volume change（³00%）during（de）lithiation cycling and poor electrical conductivity.It has been evidenced that the promising approaches to optimize Si anode mainly include:（1）adopting nanoscale or porous Si to avoid structural fracture;（2）creating novel binders to reinforce the electrical contact;and（3）constructing silicon/carbon（Si/C）composites to buffer volume expansion and enhance electrical conductivity,as well as block electrolyte The thesis as-prepared Si/C nanofiber composite electrodes successfully achieve higher capacity and better cycling performance than the bare nano-Si anode.1.We use polyvinylpyrrolidone（PVP）as the carbon precursor.Adopted the method of Electrospinning to prepare the Si/C nanofiber composite materials.The structure of this material was characterized by scanning electron microscope the composite materials maintain a complete fiber morphology.And the effects of preparation conditions（massratio of silicon/carbon.）on the electrochemical performance of composite anodematerials were studied.The performance of composite material has large improvement than pure silicon through electrochemical performance test.Through explorations of experiments,it is observed when silicon and carbon feed ratio is 1:6,the composite materials obtained have excellent electrochemical cycling performance.These composites can still reserve 1083 m A h/g specific capacity after50 charge-discharge cycles at a current density of 50 mA/g2.SiO₂ as template using the method of Electrospinning preparation of porous Si/carbon nanofiber composites materials.By the research of different silicon carbon proportion,The performance of composite material has large improvement with the increase of silicon content.Through explorations of experiments.When the amount of PVP unchanged only change the silicon content,in three proportions when the silicon content of up to 0.8 gthe composite materials obtained have excellent electrochemical cycling performance.These composites can still reserve 1071 mA h/g specific capacity after 50 charge-discharge cycles at a current density of 50 mA/g and the initial coulombic efficiency of 88%.