Study Of Transition Metal Oxides And Transition Metal Sulfide As Anode Materials For Lithium-ion Batteries

Lithium-ion batteries, a new clear energy, is carried on by insertion-deinsertion reaction of lithium ion between anode and cathode of the battery. Along with the reduce of fossil energy and serious pollution which caused by using fossil energy, it is urgent to seek a clear energy. A rising number of researchers have paid more attention to lithium-ion batteries for its advantages of environment friendly, no memory effect, high energy density and reused. Although lithium-ion batteries have a widespread application, it is hard to meet the standards of high energy such as car power, and its partial reason is due to the low theoretical capacity commercial anode material. Therefore, it is essential to exploit new and high theoretical capacity anode materials for generalizing the application of lithium-ion batteries. The paper is aim to study the electrochemical performance of transition metal oxides and transition metal sulfide as high capacity anode materials for lithium-ion batteries. The research contents are mainly as follows:1.Mixed-phase iron oxide nanocomposites as anode materials for lithium-ion batteriesMixed-phase iron oxide nanocomposites (abbreviated as m-Fe2O3) of hematite (α-Fe2O3) and magnetite (γ-Fe2O3), using potassium ferricyanide (K3[Fe(CN)6]) as the precursor, are successfully synthesized via a simple two-step approach incorporating a hydrothermal reaction and the subsequent thermal annealing. The crystalline structures, specific surface areas and surface morphologies of the as-prepared m-Fe2O3 are characterized in detail by X-ray diffraction (XRD), nitrogen sorption analysis and scanning electron microscopy (SEM), respectively. The electrochemical performances of m-Fe2O3 are examined by galvanostatic cycling and cyclic voltammetry (CV). Transmission electron microscope (TEM), high resolution TEM (HRTEM), selected area electron diffraction (SAED) and Raman are used to investigate the nanocrystalline and composition of the materials. Compared to α-Fe2O3, m-Fe2O3 exhibits a much more excellent cycling stability with a typical discharge specific capacity of 982 mAh g-1 after 50 cycles at a current density of 100 mA g-1. The superior performance of m-Fe2O3 to α-Fe2O3 would provide a new perspective about the effect of mixed-phase on improving the electrochemical properties of lithium-ion batteries.2. Cobalt sulfide/CNTs nanocomposites as anode materials for lithium-ion batteries.Cobalt sulfide/CNTs nanocomposites (CoS-CNTs) was prepared by a simple and effective solvothermal method with one pace. The X-ray diffraction (XRD) is used to investigate the crystal structure. The surface morphologies of the as-prepared CoS-CNTs are characterized by scanning electron microscopy (SEM). The nanocrystalline and particle diameter of the materials are characterized in detail by transmission electron microscope (TEM). The electrochemical performance measures are carried on a Land tester and examined by galvanostatic cycling with a density of 100mA g-1 between 0.005 V to 3 V, and the results show the materials have a superior cycle stability that keep a high discharge capacity of 780 mAh/g after 50 cycles. The materials are also present a better rate capabilities in the density of 100 mA g-1,200 mA g-1,500 mA g-1 and 1000 mA g-1. The excellent electrochemical performances is duce to litter particle diameter and synergistic reaction of CNTs. The preparation and the excellent electrochemical performances of cobalt sulfide/CNTs nanocomposites is promising to provide assist for study on improving the property of cobalt sulfide.3.Cobaltosic oxide nanoparticle as anode materials for lithium-ion batteries.Cobaltosic oxide nanoparticle were prepared by sol-gel method with histidine and Cobalt chloride. The crystal structure and the surface morphologies of the nanoparticles were characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The electrochemical performance were carried on Land tester with a current density of 300 mA g-1. Compared with cobaltosic oxide nanoparticle which prepared by hydro-thermal method, the particles size of obtained sample are about 30 nm. And the measure results shows that the obtained cobaltosic oxide nanoparticle has a similar electrochemical with which prepared by hydro-thermal method which can be attributed to the aggregation of the nanaparticles. The research will provide some theory basic for the study of preparing cobaltosic oxide nanoparticle by sol-gel methode.