| Because of their high energy density, high specific capacity, long cycle life, light weight, nomemory effect and so on, lithium ion batteries, which have broad prospects, have been widelyused in portable equipment, satellite, reserve power, electric vehicles and otherfields.Otherwise, the existing industrial application material has been difficult to meetgrowing demand, Along with the pursuit of better Lithium ion battery with higher energy,longer cycle life and more security. Therfore, looking for new electrode materials forlithiumion batteries has become an important research topic. As we all know,the anode oflithium ion batteries is a essential factor in its performance.It is imminent to look forsubstitutable anode materials with long cycle life,better security and low cost.In thisdissertation,we study the phase of Li2O-Fe O-Si O2 ternary system and compoundLi2 Mn O3.Hope to provide a certain reference for the practical application of these materials infuture.The main research contents are as follows:(1)Phase equilibria in the ternary Li2O–Fe O–Si O2 system is studied by means of X-raypowder diffractioninnovatively. The Li2O–Fe O–Si O2 system can becharacterized by theexistence of 9 three-phase regions with 7 compounds in the Li2O–Fe O, Fe O–Si O2, andLi2O–Si O2 binary systems and one compound,Li2 Fe Si O4, exists in the Li2O–Fe O–Si O2 ternarysystem.(2)Pure phase Li2 Si O3, which synthesized by solid-state reactions under different atmosphereand characterized through X-ray diffraction(XRD) and Rietveld refinement, shows likenanosphere with diameter varying from 500 nm to 800 nmby scanning electron microscopy(SEM).Carbon-coated Li2 Si O3 show the same structure and morphology, but has smallerdiameter from 200 nm to 500 nm.Charge-discharge testing,both carbon-free of carbon-coatedLi2 Si O3,is measured at 5 and 20 m A/g current density in the voltage of 0.1~3.0V. The initialdischarge-specific capacities of carbon-free can reach to 235.7m Ah/gand 124.0m Ah/g; thecarbon-coated can reach to 315.0m Ah/gand 279.0 m Ah/g.Besides,Electrochemical impedancespectrum(EIS) and in situ X-ray diffraction are used during the research.(3)The same methods are used during reasearching Li4 Si O4 as anode material of Lithiumion battery, although it has different structure and morphology.Carbon-free and carbon-coatedLi4 Si O4 show like nanoparticles with size about 300 nm and 900 nm, respectively.Charge-discharge testing,both carbon-free of carbon-coated Li4 Si O4,is measured at 5 and20 m A/g current density in the voltage of 0.1~3.0V. The initial discharge-specific capacities ofcarbon-free can reach to 180.0m Ah/gand 95.3m Ah/g; the carbon-coated can reach to277.5m Ah/gand 220.2 m Ah/g.(4)Li2Mn O3 is carried though a series of test as anode material,such as XRD,SEM,GITTand charge-discharge test.Charge-discharge testing,both carbon-free of carbon-coatedLi2 Mn O3,is measured at 60 m A/g current density in the voltage of 0.1~2.5V. The initialspecific capacities of carbon-free can reach to 1005.2m Ah/g and 291.9m Ah/g; thecarbon-coated can reach to 1274.9m Ah/gand 460.1 m Ah/g. After 10 cycles, can still maintain88.24% and 83.68% of the initial capacity; show great electrochemical performance. |
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