Fabrication And Property Research Of Metal Oxide Anode Materials For Lithium Ion Batteries

With the rapid increase of demand for energy,more and more fossil fuels are needed,leading to serious environmental pollution and Global warming,at the same time.Considerable efforts are made to try to discover and develop new environmentally friendly renewable energy,such as wind energy,solar energy,nuclear energy and so on.Lithium ion batteries?LIB?received extensive attention because of its high energy and power capacities,low price and environmental friendly as a reusable energy device.But the energy and power density of Li-ion battery currently can not yet meet the requirements of Electric Vehicles and large energy storage devices.One of the major limits to further improve the energy density of lithium-ion batteries is that the present commercial anode material is graphite,whose theoretical specific capacity is only 372mAh g^-1.Therefore,Design and fabrication of new kind of anode material with high energy density,cheap price and high safety,is of vital significance.Metal oxide anode materials consider as one of the most promising alternatives of next generation LIB anode materials,due to their high theoretical specific capacity,abundant reserves low price and higher security.Firstly,the dissertation introduces a method of coaxial electrostatic spinning to fabricate SnO_x/C@Ni fiber materials with core-shell structure.The inner layer is porous SnO_x nano-spheres evenly dispersed in the carbon fiber,and outer coated with higher graphitization degree of carbon layer and nano-sized nickel particles.Porous SnO_x nano-spheres not only greatly shorten the transfer path of lithium ions and electrons,but also provide ample space for the volume expansion in the process of charging and discharging.The addition of nickel nano-particles,effectively enhances the graphitization degree of carbon fibers,and improves the whole conductivity of the composite materials,further provides of protective layer for SnO_x anode materials with better electrical conductivity.As a result,the core-shell SnO_x/C@Ni nano-fiber materials prepared exhibit excellent cycle stability and rate performance.Next,the thesis recommends porous Fe₃O₄/C microspheres fabricated by methods of electrostatic spray.By adjusting the composition and the proportion of organic polymer and carbon materials,we design and prepared a new kind of Fe₃O₄/C composite material.In the typical structure,CNTs and KB are deposited together to form a stable microsphere structure with good electrical conductivity and numerous mesoporous pores inside.Finally,the graduation thesis presents hollow core-shell SnO_x/C@TiO₂ composite microspheres and its preparation method.SnCl₄/PVA microspheres were fabricated by oil in water.Because PVA contains lots of hydroxyl,tetrabutyl titanate can hydrolyze on the surface of SnCl₄/PVA microspheres.After carbonization treatment,hollow core-shell SnO_x/C@TiO₂ composite microspheres were obtained.The composite material both uses high theoretical capacity of the inner SnO_x,and makes full use of the stability of TiO₂ anode materials in the process of charge and discharge.The plentiful space between SnO_x/C and TiO₂ provides enough buffer space for volume expansion during lithiation/delithiation processes,improving the electrochemical stability of SnO_x materials.