Research On The Construction Of Carbon Composite Nano-anode Material And Its Lithium Storage Performance

Lithium-ion battery has been widely used in a wide range from the portable digital products,electric vehicles,to energy storage power station,due to the lithium ion batteries offering a high average output voltage,high energy density,no memory effect and longer cycling life and working in a wider range of temperatures.However,the low specific capacity(372 mAh/g)and poor charge and discharge performance of graphite,which is the most popular anode material in commercial lithium ion batteries limited the application of lithium-ion battery.So exploration of new anode material,which has high energy density,high rate performance and long cycle life,is key research area for improving new generation of lithium ion battery.Recently,many research groups' works showed that some transition metal oxides,exhibit high reversible capacities and high energy densities.Unfortunately,the application of transition metal oxidesis limited by their poor ion diffusivity,electronic conductivity.On the other hand,the alloy anode materials,such as Sn,display high specific capacities,moderate operation potentials,and good safety.However,the alloy anode material has severe capacity fading problem due to the cracking and crumbling of the active material caused by huge volume change during the lithiation/delithiation processes.It is one of effective solution for above problems to fabricate electrode with special nanostructure.In this work,two kinds of carbon-based electrode structureshave been designed and prepared to improve the conductivity of TiO2 anode material and stability of Sn anode material.The main studies include the following parts:1.Study of preparation and propertiesof Ni nanoparticles decoratedanode of TiO2/reduced graphene oxide(RGO)flakes and the study of and Electrochemical Lithium Storage.The Ni nanoparticles decoratedanodes of TiO2/reduced graphene oxide(RGO)flakes were prepared by hydrothermal method.The structures and compositionof the electrods have been studied by scanning electron microscope(SEM),Transmission electron microscope(TEM),X-ray diffraction(XRD)and Raman spectra.The electrochemical results show that this anode has high specific capacity even under the high current density(331 mAh/gat 0.5 A/g and 198 mAh/g at 5 A/g).This kind of anode is very stable,the specific capacity did not reduce after 1000 cycles.2.Study of preparation and propertiesof anode of Sn-C nano fiberAnode of Sn-C nano fiber was prepared by electrospinning technique.The characterization of structure showed that the Sn particles were evenly embedded on the carbon nanofibers with many pores in the nanofibers.This structure improved the dififusion of lithium ion and also provided much space for stabilizing Sn nanoparticles.So the anode displayed very high capacity and stability.The first discharge capacity of the anode could be 2218 mAh/g.Under the rate of 0.2 A/g,the specific capacity of anode kept at 809 mAh/g after 500 cycles,and the retention capacity could reach 93%after 500 cycles even at higher rate of 0.5 A/g.