Synthesis And Electrochemical Performance Of Molybdenum-and Iron-based Anode Materials For Lithium-ion Batteries

With the development of science and technology,wearable electronics portable and electronic have been widely used in modern society.The use of non-renewable fossil fuels as energy sources will cause serious environmental problems.Therefore,the lithium ion batteries developed and commercialized have become the choice of energy storage power.Graphite is a commercialized anode material for lithium ion batteries.Its theoretical specific capacity is 372 mAh g^-1,which is difficult to meet the needs of modern social development.Therefore,the current research focus on the development of new anode materials.Molybdenum and iron-based anode materials have many advantages,such as high theoretical specific capacity,abundant reserves and low cost.They have attracted much attention and are expected to instead of graphite become the next generation of lithium-ion battery anode materials.However,molybdenum-and iron-based anode materials display volume effect during charg-discharge process,this will cause the electrode material agglomerated and pulverized,resulting in poor capacity cycling performance.In order to overcome the defects of volume expansion,this paper tries to use carbon-based materials?CNF,RGO,GO?as substrates,and composite with molybdenum-and iron-based materials to restrain the volume expansion and improve the material cycling performance.The specific research contents are as follows:1.The powder of carbon nanorods-MoS₂ core-sheath heterostructure is successfully synthesized by hydrothermal method.Carbon nanorods-MoS₂ is compose of hierarchical MoS₂ nanosheets tightly grown on carbon nanorod,in which carbon nanorod as a template effectively reduces the aggregation of MoS₂ nanosheets.In this paper,the electrochemical properties of carbon nanorods-MoS₂ composite electrode are studied in detail,the processes of lithium ion embedding MoS₂ in two different electrochemical windows?1.0-3.0 V and 0.001-3.0 V?were studied.MoS₂ supported by carbon nanorod presents better electrochemical performance than pure MoS₂sample under various electrochemical windows.2.On the basis of the previous chapter,flexible MoS₂/CNF membranes are prepared by changing the amount of raw materials,without any binder,conductive additive and current collector,the problem of contact between electrode material and collector is avoided.The number and morphology of MoS₂ nanosheets grown on CNF films can be adjusted by changing the amount of raw materials.Porous MoS₂nanoflakes in MoS₂/CNF-B sample possess abundant channels for fast ion diffusion,and CNF provide a channel for electronic transmission,increased the conductivity of MoS₂.MoS₂/CNF-B sample delivers 605.7 mAh g^–1 at higher current density of 1.0 A g^–1,and no capacity decay till 100 cycles.3.Fabricate heterostructure MoS₂-MoO₂/RGO?MOSR?hybrids as anode material for lithium/sodium ion battery by a facile hydrothermal synthesis.In the as-obtained hybrid,reduced graphene oxide?RGO?as substrate can not only improve the electronic conductivity,but also effectively prevent the restacking and pulverization of MoS₂-MoO₂ during a long cycling process.The remarkable heterostructure of MOSR can supply abundant active sites and shorten electron and ion transport channels.Meanwhile,synergistic effect of MoS₂,MoO₂ and RGO are responsible for excellent electrochemical performance of MOSR.Our results indicate that the heterostructure MOSR is one of a good candidate anode material for LIBs and SIBs.4.Fe₂O₃-GO composites with different GO were prepared by ultrasonic-assisted and hydrothermal methods.As a base material,GO improves the conductivity of Fe₂O₃ and alleviates the aggregation and volume expansion of particles.The electrochemical performance of the prepared composite was tested.The electrochemical performance of the electrode with GO concentration of 2 mg mL^-1 is the best.