Preparation And Electrochemical Properties Of Anode Materials For Lithium-ion Batteries

In recent years,Lithium-ion batteries（LIBs）have been widely used in portable electrical equipment,such as notebook computers,mobile phones,and digital cameras,as well as electric vehicles,aerospace and many other fields due to their high energy density and long cycle life.However,at present,the main anode materials on the market are traditional graphite carbon materials.The theoretical specific capacity of graphite is low,which can not meet the needs of high energy density for energy storage equipment.To solve the above problems,biomass-carbon functional materials were synthesized by the chemical activation,carbonization,and freeze-drying methods.And the cobalt nanoparticles with vanadium nitride composites were synthesized through hydrothermal method and nitridation.The structure of lithium-ion anode material was reasonably designed and its electrochemical performance was also investigated.The main research contents are as follows:（1）The loofah sponge-derived hollow carbon fibers（LDHCF）were obtained by the activation and carbonization of biomass loofah sponges.SnO₂ nanoparticles were coated by hydrothermal method with LDHCF.The prepared SnO₂/LDHCF electrode retained the discharge capacity of 562.1 mAh g^-1 at 0.2 A g^-1 and the coulomb efficiency is about99.0%after 100 cycles.This composite material has good electrochemical performance as an electrode for lithium-ion battery,owing to the high conductivity,buffer effect of LDHCF,and the high theoretical capacity of SnO₂.（2）The HMD/rGO hollow fiber coated with graphene layer is favorable for the growth of ultra-thin MoS₂ nanosheets vertically and uniformly grown on the surface of the HMD/rGO.The HMD/rGO/MoS₂ electrode clearly shows a high discharge capacity of 838.2 mAh g^-1 at a current density of 0.2 A g^-1 after 200 cycles.This excellent electrochemical performance may be ascribe to the high theoretical specific capacity of MoS₂,the high conductivity of HMD/rGO,the synergistic effect between HMD/rGO and MoS₂ nanosheets,and the reasonable structure.（3）The Co-VN@C nanosheet composites were synthesized through hydrothermal method and ammonia nitridation.The metallic Co nanoparticles were distributed uniformly and had strong adhesion with the VN substrate.The prepared hexagonal Co-VN@C has many holes,active centers and carbon shell.It can buffer the large volume expansion and improve the diffusion during charge and discharge progress.The result displays that it has high cycling performance,good coulomb efficiency and better rate capability.After many cycles,it still has a stable cycle performance and good rate ability,and can maintain nearly 100% good coulomb efficiency.