Preparation And Performances Of Transition Metal Oxides(Sulfides) As Anode Materials For Lithium Ion Batteries With Binder-free

As a kind of environmental friendly and renewable energy storage devices,lithium ion battery(LIB)as commodity power has entered the life of human beings.With the increasing demand for lithium-ion battery performance,commercialized negative graphite materials have been unable to meet the needs.Therefore,finding new materials with high specific capacity,low cost and environment friendliness is the common goal of today's lithium ion battery industry.Owing to high reversible capacity,abundant sources and low price,the transition metal oxides(or sulfides)have attracted wide attention in the field of LIB.However,transition metal oxides(or sulfides)have some problems,such as poor electrical conductivity,high irreversible capacity loss and the volume expanding etc.,,which could reduce the electrochemical performance of the materials.Therefore,in order to overcome the above shortcomings of transition metal oxides(or sulfides),there are many measures have been carried out,such as the rational design of material structure,carbon material composite,morphology control,and binder-free in this dissertation.The main results of this work are summarized as follows:1.The organic carbon was directly adsorbed on the nickel foam by the incomplete combustion of candles,and then NiO/C/Ni foam nanocomposite was prepared by calcination methods.The nanocomposite was directly used as an anode material for LIB with binder-free.Atthe current density of 0.2 A g-1,after 770 cycles,the reversible specific capacity of the NiO/C Ni foam nanocomposite was still as high as 710 mA h g-1,exhibiting very stable cycling performance,which can be attributed to its excellent structure design and good contact between electrodes and foam nickel,which shortens the diffusion path of Li+ and accelerates rapidly embedding and releasing of Li+ on its surface.This research method is simple,and using candles as carbon source in our life provides a new idea for us to synthesize other metal oxides coated carbon as anode materials.2.Based on the foam nickel framework,the octagonal flower-like Cu2O was grown on the surface of nickel foam by Gibbs-Wulf.After annealing at high temperature,the PVP coated on the Cu2O surface was carbonized to obtain the porous octagonal flower-like CuO@C/Ni foam composite material.The octagonal flower-like CuO@C with a particle size of about 1.5?m is distributed on the surface of the nickel foam framework.When used as anode materials for LIB,the first specific charge and discharge capacity of The octagonal flower-like CuO@C/Ni foam can be reached 781 and 550 mA h g-1 respectively,and after 300 cycles,the the reversible capacity of the octagonal flower-like CuO@C/Ni foam could remain 505 mA h g-1.The porous octagonal flower-like CuO@C/Ni foam composites for lithium ion anode material with binder-free showed excellent electrochemical performance,because coated carbon layer can relieve the bulk crushing which caused by the electrode in the charge discharge process,increasing the electrode conductivity and cycling performance stability.Porous octagonal flower-like type special structure and binder free design can make the material fully contact with organic electrolyte,increase the diffusion rate of ions,and enhance the electrochemical performance of electrodes.3.The Ni3S2@GO/Ni foam composites with multilayer nanosheets arrays are synthesized in situ on nickel foam via one step hydrothermal method and co-precipitation principle.By using Ni foam as nickel source and thioacetamide as sulfur source,the composites are prepared by the hydrothermal process,at the temperature of 160? for 10h.When the Sn4+ is introduced into the system,the morphology of the composites can be changed by the rhombus conical array surface of nickel foam growth transforming into the multilayer chip array structure.The multilayer nanosheets arrays as anode materials for LIB can not only increase storage sites of the lithium,but also can alleviate the embedding and prolapse of volume change in the process of charge and discharge by Li+.At the same time,the Ni foam can be used as the collector fluid in the battery.The metal frame can make more active site on the surface,as well as the electrode material can come into contact with the organic electrolyte,which could accelerate the ion diffusion rates,and enhance the electrochemical performance of the electrode material.The electrochemical performance tests should when the current density is at 0.5 A g-1,the first specific charge and discharge capacity of multilayer Ni3S2@GO/Ni foam nanosheets arrays can be high 797.8 and 1182.3 mA h g-1,respectively,and at the high current density of at 0.2 A g-1,after 120 cycles,the reversible capacity could remain 1006.6 mA h g-1.It is shown that the multilayer nanosheets arrays are beneficial to the improvement of the electrochemical performance of the anode material for lithium ion batteries.