Controllable Synthesis Of Nanostructured Metal Oxides And Sulfides As Anode Materials For Lithium Ion Batteries

With the rapid development of high energy-consuming electronic devices,like electric vehicles(EVs)and hybrid electric vehicles(HEV),lithium-ion batteries(LIBs)with long cycling performance,high energy and power densities have received intensive research attention as energy storage devices.The performance of LIBs is determined mainly by the choice of electrode materials.Graphite is at present the most intriguing anode materials for LIBs.Unfortunately,its application is held back by the inferior theoretical capacity and the formation of lithium dendrites on the surface of electrodes after consecutive cycles.It is therefore highly desirable to develop advanced anode materials with high theoretical capacities and superior rate capabilities.Titanium dioxide(TiO2),(iron,cobalt)oxides and metal sulfides have been extensively investigated as attractive anode materials owing to their excellent rate performance and high specific capacities,respectively.Novel structural designs and synthetic techniques are the most crucial points to improve the electrochemical performance.This paper focused on preparing different morphologies and chemical compositions of Fe2O3,Co3O4,TiO2 and metal sulfides hybrid functional electrode materials.The lithium storage performances of the as-prepared electrode materials are further studied.The work mainly included the following contents:1.The one dimensional(ID)core-shell hybrid nanostructures were synthesized through mild oxidation of Fe(CO)5 on the surface of silver nanowires.Because the good conductivity of silver nanowires and the 1D core-shell structure can alleviate the large volume change during cycling,the hybrid structures can deliver superior lithium storage performance in terms of stable cycling performance and superior rate capabilities.2.Porous Co3O4 cubes are synthesized by utilizing cobalt coordination composite as both the precursor and the self-sacrificing template through annealing in air.The graphene encapsulated Co3O4 cubes are obtained by a facile self-assembly process.The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity and withstand volume variation upon prolonged cycling.As anode materials for LIBs,the composite shows high specific capacities and excellent cycling performance.3.Uniform mesoporous TiO2 hollow spheres are synthesized by combining template,sol-gel and hydrothermal methods.Fluorine-doped carbon derived from polyvinylidene difluoride was further encapsulated onto mesoporous TiO2 hollow spheres to improve the electrical conductivity.The hybrid materials possess good electrical conductivity and lithium ion mobility,thus exhibiting desirable lithium storage properties.4.Mesoporous TiO2 hollow spheres are modified by carbon layer and Au nanoparticles.When used as anode materials for LIBs,it is believed that the carbon and Au can improve the electric conductivity,and such well-defined construction can effectively shorten the diffusion path of lithium ions,thus lead to excellent electrochemical properties.5.The core-shell Co3O4?TiO2 composite is synthesized by the thermal decomposition of the cobalt coordination polymer which surface was the homogeneous deposition of polydopamine and TiO2 layers.The sample possesses the advantages benefiting from the merits of both components and robustness of the architecture which can withstand structural deformation upon long-term cycling,thus resulting in high specific capacity and good cycling stability.6.Uniform sized CoMo-glycerate spheres were prepared by a hydrothermal process.Subsequently,the CoMo-glycerate spheres were successfully converted into yolk-shell structures via a sulfuration reaction.Finally,the Co9S8/MoS2 yolk-shell spheres are obtained by a thermal annealing treatment.The Co9S8/MoS2 yolk-shell spheres possess a high Brunauer-Emmett-Teller(BET)surface area and effective synergistic interactions between both components.When evaluated as anode materials for LIBs,the as-prepared Co9S8/MoS2 yolk-shell spheres deliver superior lithium storage performance with stable cycling performance and good rate capability.